texts: Why does the flight controls check come before arming the autobrake on the A320?

texts: As per SOP on the A320 we first perform the flight controls check and then arm the autobrake to max. What is the reason behind this?


texts: What equipment qualifies as FAA-acceptable for providing "Supplemental Oxygen"?

texts:
FAR 91.211 tells us when supplemental oxygen is required, but it's not very specific as to how that oxygen is to be provided. FAR 23.1447 gives some information about installed systems, but I can't find much on FAA requirements if you're using a portable system (cylinder, regulator, and cannula/mask like a Mountain High system).

Are there specific requirements/recommendations regarding portable oxygen equipment for Part 91 General Aviation, or can you just pick up a a medical or welding tank, stick a regulator on it, and pass out masks to your passengers?


texts: What navigation publications are required when flying from KSNA to KAVX?

texts: If I'm flying to Catalina Island (KAVX) from John Wayne Airport (KSNA), which is 30 miles over water, what navigation publications are required to be on board for the route of flight?


texts: Best Practices when removing/inspecting/mounting control surfaces?

texts:
I am looking for a better way to essentially "mount" the control surfaces from a Boeing 737-747-777-787 and MD-11's. The current process is to just remove them and strap to a table. The issues with this is that it takes a lot of time to remove/inspect and possibly repair. the other issue as the way we are "mounting" them for said inspection. By strapping them to a table they can be bent, dropped, and it just isn't the best idea to have the control surfaces, like an 18 ft aileron, laying on a table...

I am just looking for any advice when it comes to mounting and servicing these parts as well as alternatives to strapping them to a table...


texts: What are the structural differences between short- and long-haul airplanes?

texts: As I understand it, pressurization cycles introduce the most stress on an airframe so maintenance intervals are tied to it. However, not all planes are equal in that regard, a long haul flight in a 747 might easily take 10 hours counting for one pressurization cycle while a 737 can do 6 trips in that time. Are short-haul planes build "sturdier" in this regard than their long-haul counterparts so that they are able to better cope with the amount of stress? And/or do they have to go into maintenance more often?


texts: About climb: If we use T/W as input, the second grade equation yields two solutions for W/S. Are both solutions realistic?

texts:
Raymer tells (Source: Raymer: Aircraft Design – A Conceptual Approach Chapter "5 THRUST-TO-WEIGHT RATIO AND WING LOADING" Paragraph “5.3 WING LOADING” Subparagraph “Climb and Glide”) that, when the aircraft is climbing, if the climb angle γ is small,

then $G=\frac{T-D}{W}$

(G is Climb Gradient as defined by Raymer words: "Rate of climb is vertical velocity,.. Climb gradient G is the ratio between vertical and horizontal distance traveled. This is approximately equal to the vertical climb rate divided by the aircraft velocity, or the sine of the climb angle γ." Source: Raymer: Aircraft Design – A Conceptual Approach Chapter "17 PERFORMANCE AND FLIGHT MECHANICS" Paragraph “17.3 STEADY CLIMBING AND DESCENDING FLIGHT” Subparagraph  “Climb Equations of Motion”)

Then $\frac{D}{W}=\frac{T}{W}-G$   ( that is the first relation for D/W).

At the same time  $D=q\cdot S\cdot c_{D0} + q\cdot S\cdot\frac{c_L^2}{π\cdot AR \cdot e}$

And substituting $c_L=\frac{W}{q\cdot S}$,

$$\frac{D}{W}=\frac{q\cdot S\cdot c_{D0}+q\cdot S\cdot\frac{c_L^2}{π\cdot AR\cdot e}}{W}=\frac{q\cdot c_{D0}}{\frac{W}{S}}+\frac{W}{S}\cdot\frac{1}{q\cdot π\cdot AR\cdot e}$$

(that is the second relation for $\frac{D}{W}$)

Equating the first and the second relation and solving for wing loading,
we have:

$$\frac{W}{S}=\frac{\left(\frac{T}{W}-G\right)± \sqrt {\left(\frac{T}{W}-G\right)^2-\frac{4\cdot c_{D0}}{π\cdot AR\cdot e}}}{\frac{2}{q\cdot π\cdot AR\cdot e}}$$

MY FIRST QUESTION: In this equation are both, the bigger and the lower solution values for $\frac{W}{S}$ realistic for aircraft?

After,  Raymer notes that the term within the square root symbol in the equation above cannot fall below zero, so the following must be true regardless of the wing loading:

$$\frac{T}{W}≥G+2\cdot\sqrt{\frac{c_{D0}}{π\cdot AR\cdot e}}$$

MY SECOND QUESTION: Raymer doesn’t consider that there are two solutions sourcing from the condition that the term within the square root symbol cannot fall below zero, the other one is:   $$\frac{T}{W}≤G-2\cdot\sqrt{\frac{c_{D0}}{π\cdot AR\cdot e}}$$. Why shouldn’t be considered? Could the second solution represent something realistic?

I HAVE A SUPPLEMENTARY QUESTION:
Relating to my questions above, I have to report two comments Raymer writes immediately after the last equation and inequality.: "This equation says that no matter how "clean" your design is, the T/W must be greater than the desired climb gradient! ....... Another implication of this equation is that a very "clean" aircraft that cruise at a high speed despite a very low T/W will probably climb poorly. A 200-mph airplane that flies on 20 hp can't be expected to climb as well as an airplane that requires 200 hp to reach 200 mph (unless the latter weighs ten times as much)"
Could anyone explain me better the last sentences, in particular, in which case T/W is very low with high speed? If we have high speed doesn't T/W should be high too?


texts: How are winter weather operations different if they are based on an aircraft carrier instead of a runway on land?

texts:
I am guessing that naval aircraft carriers do not have room for conventional deicing trucks and snowplows.  If they need to have frequent takeoffs and landings, time for clearing precipitation may be very limited, and there may be no alternate runways.  How do they deal with winter weather?

I am interested in treatment of both the carrier deck and the aircraft.


texts: What is the specific consumption of an A320 at Mach 0.78 and 11,000 metre altitude?

texts: I am currently doing a dissertation on an electric drive system on planes and I need help. I can't find the specific fuel burn rate for an Airbus A320; if anyone could help it would be great. Also a link or solution to calculating specific fuel consumption and known fuel burn would be much appreciated. It is so I could calculate the fuel used from added weight in the Breguet equation, but there is no average fuel consumption for the formula in kg/Ns.


texts: Why wasn't Saint-Exupéry able to cover more distance before his 1935 desert crash?

texts:
Is there any source that provides more details on Saint-Exupéry's desert crash in 1935 than Wikipedia does:

  On 30 December 1935, at 2:45 a.m., after 19 hours and 44 minutes in the air, Saint-Exupéry, along with his mechanic-navigator André Prévot, crashed in the Libyan desert, during an attempt to break the speed record in a Paris-to-Saigon air race and win a prize of 150,000 francs. The crash site is thought to have been near the Wadi Natrun valley, close to the Nile Delta.

I find hard to understand how flying for nearly 20 hours between Paris and Saigon can lead any plane to as short distance as middle Libya?

Google Maps shows a distance of approx. 1950 miles straight line between Paris and Wadi Natrun, which gives us nearly exactly 100 mph of speed, which is only half of Caudron Simoun's speed.

What am I missing? Is it / was it a regular practice to fly "that slow" on such large distances?

There are 6000 more miles to fly between Wadi Natrun and Saigon, according again to Google Maps. With 100 mph we have 60 hours of flight plus additional 20 hours already flown. Which gives us a total distance of 8000 miles or 80 hours with this speed. Was there any aircraft and pilot, in 1935, able to manage such trip, even assuming breaks in flight for fuel refilling and resting?


texts: What are the differences between the two main brace positions?

texts:
Why are there two different brace positions (pictured below) ?
(If there is a difference between the official and true reason, please state both. In many planes the reduced seating spacing does not allow the pike position (on the right), but I doubt this is the official statement of airlines.)
Are they equally protective ? If not, why are both recommended ?
What arguments are there in favor or against each ?
If available, statistical data and relevant links to studies and crash tests would be very welcome if they distinguish between the two positions.


texts: Are all US airline aircraft certified into known ice?

texts:
Are all  US airline aircraft certified for flying into known icing (FIKI) conditions?

I assume all the large (100+ PAX) aircraft come FIKI certified from the design stage?

What's the largest passenger aircraft that would be non-FIKI certified?


texts: How does inlet spillage drag produce a lip suction effect?

texts:
From this page:

  Spillage drag, as the name implies, occurs when an inlet "spills" air around the outside instead of conducting the air to the compressor face. The amount of air that goes through the inlet is set by the engine and can change with altitude and throttle setting. The inlet is usually sized to pass the maximum airflow that the engine can ever demand and, for all other conditions, the inlet will spill the difference between the actual engine airflow and the maximum air demanded. As the air is spilled over the external cowl lip, the air is accelerated and the pressure decreases. This produces a lip suction effect, which partially cancels out the drag due to spilling.

I understand most of the above, except starting from "This produces a lip suction effect..."

If I'm getting this right, the unwanted air, stuck in the inlet, leaves the inlet moving forward, spills out, sucking the airframe with it, thus negating some of the drag caused by the spillage?


texts: Does the EPU on the F-16 need to be manually extinguished after an emergency landing?

texts:
After having watched

I noticed at the end that one of his colleagues mention he has a "running EPU with hydrazine, you're gonna need fire response".

Is this just a precaution, or does this fire response actually do anything with the EPU?


texts: Why did my flight climb so sharply on takeoff?

texts:
I was on a Ryanair flight this morning that seemed to perform an incredibly aggressive takeoff from London Stansted on a 737-8.  Takeoff was fairly fast, but the climb was the steepest I ever encountered.

For context, we were taking off from runway 22, with wind 34 kt from the South/Southwest gusting 51 kt


texts:
A rare -- as I was told -- situation of aborted take off for a large passenger jet. What is next?

Everything goes as smudge as possible after getting jetliner to full stop. Plane clears the runway and goes back to the either parking position or designated place at taxi way.

What steps must be performed in order to make this aircraft back to take-off waiting queue?

Approximately how long will it take for this plane  to be taking-off again? I know that this vary on many circumstances that's why I am asking about approximate only. Is there any priority for the plane that should already went off? Will that take minutes, tens of minutes or hours?

Clarification: This question is for the sake of the story that I am writing. It (both story and the question) involves Boeing 777 taking off from LHR in August 2014.

Aborted take of is due to a misleading information coming from cargo doors' sensors that reveal a possible problem only during take-off, not before (i.e. during taxi). The doors are actually closed (no real danger posed after check). But there's a tiny piece of fabrics from cargo loader's uniform stick in between doors. This question is a follow-up or alternate version of this question. Here I'd like to know what happens, if such situation will be detected after V1 or shortly after take-off and thus after such aircraft returns safely to the airport and clears the runway. In linked question I am asking about the same situation detected before V1.

I am aware that most airline experts will say that such situation is not possible at all. I am, on the other hand, a system designer and I know that such "ghost" situations of "neither 0 nor 1" sometimes do happen. But, for the sake of this question, if you feel uncomfortable with such reason -- let's assume that take-off was aborted due to any other reason, i.e. engine failure. I belive that such reason has similar severity as the need of checking whether cargo doors are really closed due to fact that on-board computer provides misleading data.

I'd lilke to underline that this is purely hypothetical question. I am aware that while such questions are sometimes hard to answer, they're in general quite welcomed in this site and are not off-topic.


texts: What should I look for / check during an oil change?

texts:
Piston aircraft engines require regular oil changes, and at least in the US it's something the FARs allow an owner with a private pilot certificate to do.

What are some of the things I should look for during an oil change (or what are some of the things I should be sure my shop is checking when they do an oil change)?


texts: How is thrust of engines on the two sides of an airplane kept exactly equal to prevent yawing?

texts: I assume that the thrust of engines on the two sides must be kept exactly equal otherwise the plane would start yawing. What mechanism is used to prevent this from happening?


texts: How do stealth aircraft reduce the Heat Signature?

texts:
According to the wikipedia article, a stealth plane requires the following features in order to reduce its radar signature and thermal detection:

  Reducing thermal emission from thrust
  Reducing radar detection by altering some general configuration (like introducing the split rudder)
  Reducing radar detection when the aircraft opens its weapons bay
  Reducing infra-red and radar detection during adverse weather conditions

How do aircraft actually achieve reduction in their thermal emission from thrust?


texts: Why do the A320’s primary flight controls have hydromechanical backups only for the rudder?

texts:
The A320 is primarily a fly-by-wire aircraft, with the pilots’ joystick and rudder-pedal inputs not going directly to the flight-control surfaces, but, rather, to the aircraft’s flight-control computers, which then decide what, if any, control-surface deflection is necessary, and send the requisite commands to the hydraulic actuators which move the control surfaces:1

However, in the event of a complete failure of the aircraft’s flight-control-computer system, the A320 can switch to a backup mode known as mechanical law, which bypasses the FCCs completely.2  In this mode, the only one of the primary flight controls to remain active is the rudder, using an emergency cable mechanism which sends the pilots’ control inputs directly to the rudder actuators; with the elevators, ailerons, and spoilerons all inactive, pitch control is maintained using manual horizontal-stabiliser trim (which uses a similar cable mechanism to send trim commands to the hydraulic motors  powering the stabiliser jackscrew) and varying engine power, and the ability to control roll separately from yaw is lost completely (to roll the aircraft in one direction or the other, it has to be yawed in the desired direction using rudder inputs and differential engine thrust; the resulting sideslip then causes the aircraft to roll towards the trailing wing, due to the positive slip-roll coupling generated by the A320’s rearward wing sweep):

The reason the elevators, ailerons, and spoilerons are unuseable in mechanical law is that, unlike the rudder, they have no direct hydromechanical connections to the cockpit controls at all, being connected only via the flight-control computers (thus leaving them cut off from the pilots’ control inputs in the event of a total failure of those computers).  If the A320 did have hydromechanical backup controls for the elevators, ailerons, and spoilerons, the pilots would be able to control the aircraft in each of its three axes separately (rather than with roll dependent on yaw, which provides very sloppy roll control with a significant time delay between the initiation of the yaw and the resulting sideslip-induced roll, and with a small but significant initial rudder-induced rolling moment in the wrong direction), and would be able to do so using the same types of control inputs as would be used in normal, fly-by-wire flight (albeit likely with considerably-increased control forces and a markedly-different force gradient), rather than having to switch to a completely different input style in mechanical law:

So why is the rudder the only one of the A320’s primary flight controls to have hydromechanical backups allowing its use in mechanical law?

1: The A320’s flight-control system, and that of all later Airbus aircraft, has several different fly-by-wire flight-control modes.  In some of these (direct law, alternate 1/2A/2B law), the pilots’ flight-control inputs in some or all control axes are simply passed straight through the computers unfiltered, with the computers parroting whatever the pilots ask of the aircraft without any of the translation present in the usual operational mode (known as normal law); however, the pilots’ inputs are still passed to the computers first, and only then to the control-surface actuators, rather than going directly aft.

2: The pitch and roll/yaw axes can each also revert to mechanical law separately in the event of a major fault in one of the primary flight controls (for instance, a double elevator jam would cause the aircraft to revert to mechanical pitch control), while still leaving the other in fly-by-wire mode.


texts: What are the pros and cons of a straight wing plane?

texts: I need this asap for my folio... Much appreciated. I'm doing a research section on my folio and I need to know the pros and cons for a straight wing in general. Everywhere I've searched doesn't seem to have the question above and is making it very difficult.


texts: Can the thrust reversers still be activated if the landing gear won't extend?

texts:
In the case of Boeings, I understand that the thrust reversers cannot be activated unless the landing gear is extended.

However, would it still be possible to activate the thrust reversers if the landing gear cannot be extended due to a technical malfunction, and the aircraft has to belly land? Would it be helpful to activate thrust reversal in this scenario?


texts: Is Rutan's method of foam core construction obsolete?

texts: Is Rutan's method of foam core construction obsolete, or is it used on other fibreglass designs as well?


texts:
In the wake of the Qatar diplomatic crisis, I saw this image from Business Insider:

How is airspace in the Persian Gulf determined? Why, for instance, does Bahrain have such a disproportionately large amount of airspace for its size? And why is Qatar's airspace predominately to the east of the country? Is this related to air traffic routes in and out of the territory (e.g., lots of Qatari flights fly over Das island, despite it being part of UAE territory)?


texts: Who operates a 707 with Boeing factory livery?

texts:
I have just seen a 707 depart from HTDA Dar es Salaam that has the tail painted with the Boeing colors. Any idea of who the plane belongs to?

Livery like this one:

Obviously 707 instead of 777 painted on it.


texts: What is the horizontal stabilizer failure procedure?

texts:
During the final flight of Alaska Airlines Flight 261:

  The CVR transcript reveals the pilots' continuous attempts for the duration of the dive to regain control of the aircraft. At one point, unable to raise the nose, they attempted to fly the aircraft upside-down.

I was wondering what the actual procedure is, if the horizontal stabilizer has a complete failure like this? Do commercial pilots ever simulate such scenarios?


texts: i have graduated from Nation Aviation Academy and my occupation is Air Traffic Control. But to become a pilot was my childhood dream. So my question is, is it possible to pass atpl exams in this situation or is it necessary to pass the pilot course? I already have medicine and icao level. Thanks in advance for answering my question.


texts: Has an earthquake ever complicated or prevented a safe landing/takeoff?

texts:
This question on being able to see ground effects of earthquakes from the air got me wondering:

No doubt a severe earthquake at the wrong time could hinder even experienced pilots, but I expect a minor one may be unnoticeable or simply cause a mildly unsteady landing:

  "An earthquake--really?  I thought that felt a little weird"

Are there any known instances of an earthquake during approach/landing/takeoff? What were the results?

Naturally if there exists any video that'd be helpful.


texts: Stress on wing/fuselage-joint of aerial water tanker aircraft - and possible mitigating measures

texts:
Following the unfortunate crash of a C-130 aerial water tanker aircraft in Australia, a friend brought to my attention a 2002 C-130 tanker crash in the US. As can also be seen in this video, the wings fold upward and separate from the fuselage, which then rolls over and crashes.

According to the referenced Wikipedia-article, citing the NTSB (1, 2), the wing/fuselage-joint (likely) failed due to fatigue:

  The NTSB investigated the crash and determined that the accident was caused by a structural failure that occurred at the wing-to-fuselage attach point, with the right wing failing just before the left. The investigation disclosed "evidence of fatigue cracks in the right wing's lower surface skin panel, with origins beneath the forward doubler. The origin points were determined to be in rivet holes which join the external doubler and the internal stringers to the lower skin panel. These cracks, which grew together to about a 12-inch (30 cm) length, were found to have propagated past the area where they would have been covered by the doubler and into the stringers beneath the doubler and across the lap joint between the middle skin panel and the forward skin panel."

This and another crash in the same year subsequently led to a fleet grounding, partially following concerns over training and maintenance.

Besides the incident referred to above, this got me thinking. The substantial and rapid change in weight when the tanker performs the drop must result in (temporary) large forces/moments on the wing/fuselage-joint. According to the summarised NTSB-report, the aircraft in the video carried some 3000 gallons of retardant (some 7000kgs at 9lbs/gallon), but does not specify volume flow. A more recent Modular Airbore FireFighting System that fits into a C-130 can disperse something under 3000 gallons in 5 seconds, yielding 600 gallons/sec - equivalent to 5400lbs or 2450kg/sec. Various comments on the YouTube-video (such as this and this) also point in that direction -- but unfortunately don't include sources. As such, I'm wondering:

to what extent these changes in weight indeed introduce forces/moments that (might) go beyond the design specifications of the aircraft?
what (technical or operational) measures are/were normally taken to prevent  such problems (structural reinforcement during the conversion, limiting 'offloading speed', no dropping during climbing/manoeuvering, etc.)?


texts: Can you fly an airliner without an ATPL?

texts:
The "captain in the right-hand seat" discussion got me thinking. As of 2013, you need an ATPL to operate any plane operating under Part 121 (as part of an "airline"). Both Captain and FO need this level of license, and new Captains require at least 1000 hours as FO.

However, all you'd need to fly the same model of plane for hire in any other situation is a CPL and the applicable type rating for the aircraft. Prior to 2013 that was all you needed to be hired as an FO on an airliner and get yoke time towards your ATPL and the left-hand seat.

The question is, are there still opportunities for a civilian CPL holder to fly large turbofan-powered airframes for a living on his way to an ATPL? My first thought was freight, but cargo planes for FedEx or UPS operate under Part 121, same as American Airlines. The only thing that really leaves is charter flights, which operate under Part 135 and thus may not require the same stricter regs as a pilot on a scheduled service. But, I don't know how many charter operations are using anything bigger than a narrow-body.


texts: How unique are waypoint names supposed to be?

texts:
I had thought that someone such as ICAO was coordinating the assignment of five-letter waypoint names such that they were globally unique.

Now I notice that OpenNav knows three different waypoints named PINTO, two of which are on the same continent.

Is this supposed to happen? Are there rules for how close identically-named waypoints can be to each other?

(A significant factor in the AA 965 crash was that there were two NDBs with the same ID close to each other, and the FMC selected the wrong one to fly towards. This might be inevitable when NDBs usually have one- or two-letter IDs, but surely with a big fat five-letter namespace uniqueness ought to be achievable?)


texts: Why is a model quadcopter 'better' than a helicopter? Why doesn't this scale up to the full-size versions?

texts:
EDIT

  Soon after I posted this, it was pointed out that a similar question
  exists. That other question answers most of mine. I shall leave this here as a stub. That way it provides a pointer to the other question and, importantly, my title contains all the keywords 'model', 'quadcopter','helicopter' and 'scale up' whereas the other question's title (Why haven't quadcopters been scaled up yet?) is less comprehensive and therefore less searchable.

Model helicopters were on the market for many, many years before quadcopters.

Presumably most of the engineering bugs had been removed by then as well as control issues.

Suddenly along comes the new kid on the block and it's all change.

Related questions

Why are model quadcopters so popular in relation to model helicopters?
How come the same reasons don't apply to full-size helicopters and quadcopters? Why don't we see search and rescue quadcopters and personnel-carrying quadcopters?


texts: Difference in lift generation for a swept wing and straight wing in subsonic condition

texts: Would there be any differences in lift for a straight wing and swept wing (front or back) with the same airfoil cross section, same chord length, same wing span, and same area when flying in subsonic condition that is lower than Mach 3?


texts: Can I fly over Schengen zone without visa?

texts:
I don't have a Schengen visa. Am I eligible to fly over any Schengen country without landing there? Of course I mean that I take off from a non-Schengen country, and land in a non-Schengen zone as well.

Moreover, can I land somewhere in Schengen zone? For example, one touch-n-go in Schengen zone airport, and then fly back.

I consider that I fly an EASA-reg aircraft with an EASA pilot license.


texts: Is the RAT pump on the A320 standard fitment or is it an "option"?

texts:
Is the RAT pump standard or optional on the A320 aircraft?
What about the B737?


texts: How does a combat aircraft handle the recoil force of a mounted gun?

texts: How is the recoil momentum distributed or countered for smaller aircraft or drones while using a mounted gun? Is there any hydraulic mechanism to counter it and how it is distributed across the entire body of an aircraft?


texts: Is multi/quadcopter flight control similar to helicopters?

texts:
The wikipedia Quadcopter entry provides some details about its flight control:

Hovering or altitude adjustement.

Pitch or roll  adjustment.

Yaw adjustement.

The following post "Quadcopter flight modes beyond traditional aircraft?" raised to my attention that it had other flight modes apart from those of fixed wing aircraft but I am not so sure with respect to conventional rotorcraft.

Question:

My assumption is that the quadcopter can be flown using conventional helicopter flight control inputs (cyclic, collective, anti-torque, throttle), am I right or is it really another beast with its very own flight control inputs?


texts: What's the minimum number of sensors for a hobby GPS waypoint-following UAV?

texts:
I would like to develop my own guidance, navigation and control (GN&C) flight software on a Raspberry Pi, for a small hobby fixed-wing UAV. From a physical standpoint, what is the minimum set of sensors/inputs needed to implement plain old GPS waypoint-following?

I understand I have a lot of math to learn, but what is the minimum set of inputs for that math? I have experience with embedded C++ for vehicle entertainment systems, but no knowledge in the aviation realm.


texts: What materials form the structural elements of the Boeing 737?

texts:
What materials form the structural elements (leaving the spars, ribs etc) of the B737?
It was tough to get any information on the kind of composites used on the 737 structure. Hoping to get some information on that.


texts:
I have heard the explanation which states that the endplates reduce the tip vortex formation thereby reducing induced drag. From what I understand induced drag is the backwards component of the total force acting on the wing and a consequence of lift creation over a finite span. Thus it depends on the downwash angle. Vortex is an after effect of this lift. I dont understand how induced drag is reduced by suppressing this vortex.

I would appreciate some clarity on this topic or an explanation which doesn't include vortices.


texts: What is the mechanism by which condensation forms above wings?

texts:
The planes landing at Sydney Airport have what looks to be sheets of steam pouring off the wings. Larger planes have multiple contrails while smaller regional planes only have these sheets.

This is the first sunny day after a large storm. There are patches of dark cloud.

From the link posted by fooot, I've learned that it's condensation, but what is the mechanism by which it forms?  The video shows planes in poor weather, but visibility here is excellent, with 20% cloud coverage.


texts: What are the indications that your turbofan engine has "thrown a blade?"

texts:
In an airliner, such as an A380, what indications do the pilots have that an engine has thrown a fan blade?

Will that always result in destruction (of the engine)?


texts: Does a rotating control surface change the wing area?

texts:
It might seem like a silly question, but bear with me.

I am using the standard formula to calculate the lift force of a wing.

L = (1/2) d v2 s CL

My question related to the s part of the formula. According to what I can find this area is calculated as if the wing was completely flat. This would be from the leading to trailing edges.

Wing Area = Wing Span x Average Chord

I am currently doing exactly this, to calculate the lift force of the wing on a computer model while model is flying. It is done at regular intervals along the wing span and added up. The sections that include control surfaces have different chord lines when the control surfaces rotate as expected causing the desired affect on lift.

BUT I noticed that the wing area also changes with the change of control surface angle. As the control surface moves closer to its upper or lower limits the surface area changes too.

Control surface at 0 deflection and at max

Red part is a control surface.

Obviously on a simple wing, the rotating control surface cannot affect the (3d) surface area of a wing. Or should not. Yet using the formula to calculate the s part the wing now has a smaller area.

To get to the point, I would like to know if this makes sense. Does the ...effective wing area change during operation of a control surface ?


texts: Why does a de Havilland Comet have radiation symbols on the instrument panel?

texts:
This image of a De Havilland Comet cockpit shows a radiation hazard symbol on each of the three centre panels, next to the (to me unknown) blue, green, and grey indicators. Why are they there?
I can't find any resources to shed light on it, but then again, I'm no aviator myself so I probably looked in the wrong places.

Source: Wikipedia


texts: What does the callout "300... MINIMUMS" mean?

texts:
MINIMUMS.... 400 APPROACHING MINIMUMS...   300 MINIMUMS.   Is this a reference to gravity? Needing more speed? Or the minimums you can see to the lights on your approach to land?

I looked this question up and someone said it had to do with being able to see the light on the runway when you are on your approach to land. But I have found that when you are in your minimums, 300 ft from ground, you need to increase your speed to avoid falling quickly or it results in a hard landing.

Do the minimums talk about gravity?


texts: What is this "hole" in the A350 fuselage?

texts:
As usual, I was looking at pictures of planes flying around me. And then I noticed a weird hole in this Singapore Airlines A350 fuselage:

Source

Registration number of this plane is 9V-SMD. According to the angle we look at the plane, the hole is more or less visible:

Source

What is this hole, and what is its purpose?


texts: How might one start a new logbook for an engine that had one lost?

texts:
About 6 months ago in a hangar at a local (KLWT), I saw a Piper PA-30 Twin Comanche and instantly wanted it. When I got home, I did a look up on the Registration (N) number and found out that the aircraft was de-registered in 2005.

I did some asking around the airport the next day and discovered that the owner had passed away. After some more research, I discovered that the airplane had one engine and its prop totaled. It had the propeller and engine replaced, but neither had logbooks and that was why the plane is collecting dust.

I really would like the airplane, because it is actually in good condition, yet it sits in the back of the central hangar and is ignored by everyone. So in a nutshell, the airplane is in good condition with airframe, avionics and logbooks for the right engine and prop. There are just no left prop or engine books.

The current owners (the estate of the deceased pilot) do not seem to even realize that the airplane is still sitting there, so I do not think that they would put much thought into selling the plane and I might be able to pick it up relatively cheaply. The only thing that I seem to need is a logbook. So I was wondering if it would be possible to somehow just start a new log after purchase? The other option is to just buy a new engine with books. Any advice?


texts: Is the Boeing 737 MAX 8 MCAS exceptional in operating when autopilot is off?

texts: To the uneducated reader it seems strange the Boeing 737 MAX 8 MCAS system only operates when autopilot is off. I understand the reasoning behind why it was implemented to operate when autopilot is off. My question is, is the operation of MCAS automated system when autopilot is off an exception for the 737 line, or are there other automated systems providing direct control surface actuator inputs when autopilot is off on the Boeing 737s? If so, what are these?


texts: ATC interruptions, when is it okay/overlooked?

texts:
Having recently completed my first solo flight, the tower gave me my taxi instructions, and then congratulated me, as my instructor was hanging out in the tower with the controllers at the time.

It's relatively busy airspace, so there were quite a few pilots on frequency, and multiple landing at the same time. However, before I could repeat/confirm my taxi instructions, a half dozen other pilots got on frequency congratulating me as the "new-blood". Seeing as this took about 30 seconds, it delayed my taxi readback, and potentially delayed other pilots approaching.

Controllers were fine with it, so it seemed, but I would assume that in certain situations this could be considered abuse of airport communications. Are there any guidelines for when the tower has to / should report such incidents, or is it merely up to the towers discretion?

It didn't prove any large issue in my case, other than a delayed taxi, but I'm wondering where the "line" would be drawn.


texts:
How did the propellers attach on a Lazair attach if the shafts had a woodruff key instead of opposite thread?

I understand the early Lazair prop shafts had a woodruff key.  How were
the props attached?

Don't you need opposite thread?

I assume you couldn't just use a cotter pin and a washer, as the props would try to shear off the cotter pins.


texts: Is the 777X actually the newest Boeing plane?

texts: I don't think the 777X is actually the newest Boeing plane (in april 2020), since it's only a new variant of a previous Boeing plane. So the actual newest plane would belong to the 787, since it's the newest plane. If that makes sense? Can anyone answer why Google says the 777X is the newest Boeing plane?


texts: Do small or regional airports have maintenance staff or companies onsite?

texts:
Do small airports or regional airports with just a couple of flights per day, maybe even from different airlines all have on-site aircraft maintenance staff? It hardly seems economical to have certified on call mechanics at most small airport? Are there regulations requiring such?
If there are not any, what happens if a hard landing is performed? From my knowledge an inspection by a mechanic is then required.


texts: Can I do an alternator check at idle in a C152?

texts: I have one question about alternator check in Cessna 152. During engine run-up we should check whether alternator is working or not, so we switch it off and then the warning light should illuminate. But we do it on pretty high RPM (1700). Would this warning light illuminate if I switch off the alternator also on lower RPM i.e. idle?


texts: How does downwash affect angle of attack?

texts:
Many aerodynamics textbooks, as well as many answers on here and similar websites claim that the downwash downstream of a wing induces a net angle of attack that is lower than just looking at flow direction and chord orientation would have you believe. They then often go on to say that lift is perpendicular to this "induced flow direction", explaining that the component parallel to the originally perceived flow direction is induced drag. I struggle with this idea, because my current understanding of lift dictates that downwash itself is a product of lift generation and therefore a product of angle of attack.
Also, when looking at visualisations of flow fields around a wing, we can see both upwash ahead of the wing and downwash behind it. Intuitively, I'm inclined to think that the downwash, being downstream of the wing, can't really affect the flow dynamics around the wing anymore. Conversely, the upwash, being upstream of the wing, should affect the flow around it, increasing angle of attack and therefore lift produced.

The only explanation I've come up with is this, though I'm not sure if it's correct:
Since any wing producing lift must introduce a net downwash on the surrounding air, the average air movement over the whole wing must also be negative. I guess my problem with this explanation is that I've always thought of angle of attack as a function of just chord orientation and flow direction. Is it correct to assume that, looking at the flow field closely around a wing, "traditional angle of attack" doesn't matter as much since the large induced flow velocities in front of the wing will make actual "aerodynamical" angle of attack, i.e. the angle at which the oncoming air actually hits the wing (as opposed to the angle between freestream flow direction and chordline) differ significantly?
I apologise if my question isn't very comprehensible, I had quite a hard time formulating it. In any case, I'd be glad for an answer, and I'll try my best to clarify what's unclear.


texts: Why do we use composite aluminium or titanium stacks in airplanes? What are their machining conditions?


texts: Does a class E airspace still exist when the associated airport is closed?

texts:
An airport tower closes at 1600 hours:

Does the extension (class E from surface up) airspace becomes non existing?
Can I fly through since the tower is closed?


texts: What is this tube along the right side of a Blue Angel?

texts:
I was at the Museum of Flight in Seattle, WA, yesterday, and came across a Blue Angel aircraft, pictured below.

Along the right front of the plane, there is a small tube that is capped with a silver cap.

I thought at first that this might be a refuelling point, but (A) I didn't see any real purpose to have mid-air refuelling on a Blue Angel, and (B) it doesn't seem like a great place to refuel (since it seems like it could easily obstruct the pilot's view).

(I looked online at some images of Blue Angel aircraft and realized there are several makes. However, I didn't find this particular tube and cap on any of the other makes. (example) In fact, I don't even recall what make of Blue Angel this craft actually is.)

What is this tube at the front of the jet, and what is it used for? Why does it only appear on some makes of the jet?


texts: Why is this F/A-18 flying through a hailstorm of sparkles?

texts:
The F/A-18 Super Hornet squadron VF-102 Diamondbacks, flying from the USS Ronald Reagan, has posted a montage video of its 2019 Indo-China cruise.
At about 5:15, the video shows a night-time cockpit view of the aircraft flying through a shower of sparks. There is also the view looking backwards. It's like a sci-fi special-effect.

What would cause this phenomenon?

source - YouTube


texts: Why do heavy bombers not carry air-to-air missiles?

texts:
Imagine a heavy bomber – such as the B52, Tu160 or B1 – is heading toward a hot zone carrying a large number of AMRAAM or longer ranged missiles. Why doesn't it also carry air-to-air missiles?

I got the idea from a TV documentary about the future projection of the air forces but I don't know why they're not already doing this? Wouldn't it be a strong deterrent capability? I'm aware of the fact that such aircraft were not designed to engage hostile aircraft; neither their speed nor maneuverability is enough for that. However, I feel they caould do serious damage to enemy aircraft formations from a relatively safe distance while being under protection of the fighters like F15, F22, Su XX...

Well, of course the enemy would be carrying similar missiles in such a scenario. Or maybe the radar of the aircraft does not have the capability to engage air to air (I don't know if such a thing is possible). But thanks to its great lifting capacity, when compared to a fighter jet, a heavy bomber may have the advantages of getting more missiles and a more powerful jammer into the action at a time. Also, especially if the aircraft was one of the low observable ones, I think it would be a game changer in any aerial conflict even when the missiles were not longer ranged than the ones the other party would be using.

So, basically, why do heavy bombers not carry air-to-air missiles today? And as a side question, what would be the benefits and trade-offs of such an upgrade to existing heavy bombers other than what I mentioned?


texts: When do pilots engage the autopilot in airliners?

texts:
I may be wrong but I learned that in regular airliners, pilots always takeoff manually.

After taking-off and going to a positive rate of climb:

When do pilots engage the autopilot?
Is there a minimum altitude to engage it?


texts: What are some examples of holding instructions and how to enter them? I understand entry with direct, teardrop, and parallel. Just having a hard time coming up with formulating the procedure. Example; C172 hold south of ABC VORTAC. Does that mean race track is the 360 radial and holding south of the vortac?


texts: What happens when an airplane is retired?

texts:
With launch of new models every few years, what happens to the older airplanes which was in service for more than decades? Where does it get stored.

Who buys old airplanes? Does manufacturers buys it back for reusing the parts or is there any specific companies which buys old airplanes?


texts: What does a higher pitching moment mean? (ie -0.095 vs -0.0022)

texts: I've found that as the angle of attack increases, the moment becomes more negative. I wanted to know what does that negative value say about the characteristics of the airfoil, and what is its importance.


texts: What is the significance of the 10,600 lbs MTOW limit?

texts:
I recently noticed that several airplanes have MTOWs very near or exactly 10,600 lbs. That was an interesting phenomenon to me because I am familiar with the 12,500 lbs MTOW regulatory limit on certain types of small planes, and familiar with the 19,000 lbs MTOW regulatory limit on certain other "commuter" planes, but I couldn't find anything to support why so many airplanes would have MTOWs at 10,600 lbs.

As I tried to google for "10,600 lbs max takeoff limit" I found more planes that are at or very near that exact MTOW but couldn't find the basis for why this is.

Does it have to do with European regulations? Does it have to do with insurance considerations?

Airplanes with near or exactly 10,600 lbs MTOW

Cessna CitationJet / M2
Beechcraft King Air C90 / and derivatives
Embraer Phenom 100
HondaJet HA-420

EDIT: A Little More Info

I have noticed that 10,600 lbs is very close to 4,800 kg. So its possible that this regulation stems from something non-FAA, something that regulates in kg, but even still, I haven't had any more luck with Google trying to figure out what the derivation of a 4,800 kg limit might be. Yet again, all I found was yet more planes that have that same MTOW limit.


texts: Do the shock waves from a supersonic plane affect general aviation planes?

texts:
Are there any considerations to take into account when flying around supersonic aircraft? I know that wake turbulence from large aircraft can pose a threat to smaller planes. Is the same true of the shock waves generated by planes in supersonic flight?

For instance, do fighter pilots need to be aware of the shock waves caused by other fighter planes in the vicinity?


texts: In which countries can I fly an FAA compliant Part 103 ultralight?

texts: İf I have a legal part 103 ultralight as defined by the FAA, in which countries may I fly this ultralight in the world in addition to the USA?


texts: Do they wait until all aircraft have landed before winding up an airline?

texts:
This BBC article suggests that any announcement about winding up Thomas Cook will wait until late at night and all its planes are on the ground (I guess they don't fly long haul distances?) before an announcement is made about bankruptcy.

What is the significance of this? Surely no airport would turn away an aircraft that needed to land?

Is it an insurance thing?

How do airlines which never have all their planes on the ground get wound up?


texts: What are these diagonal devices above the leading edge of the V-22 Osprey's wing?

texts:
The Osprey has some kind of aerodynamic devices sticking up along the top of the leading edge. This picture from the Wikipedia page of the wings rotated shows them against its silhouette:-

Public domain picture taken by Lt. Col. Kevin Gross

You can see them a little clearer on this photo shot from above, on the same page:-

Author Peter Gronemann, licensed CC 2.0

Seen from above, they look like alternating slashes and backslashes, and they're clearly intended to change the flow properties in some way. But what precisely do they achieve, and how?


texts: How is the Density Altitude performance penalty split between propeller and engine?

texts:
Let's say we have a Cessna 150 with a Continental O-240.

How is the density altitude performance hit split between the engine air intake and the propeller ability to "grab" the air.

Let's say I was able to put a engine on it that would not be affected by density altitude.

What would the remaining penalty be on the aircraft performance due to the propeller still being affected?


texts: What date and time definition is used for the second leg of a flight?

texts:
Let's take flight BA0015, from London to Syndney, via Singapore.
This is data from FlightStats.

The first leg has this data:

  "carrierFsCode":"BA",
  "flightNumber":"15",
  "departureAirportFsCode":"LHR",
  "arrivalAirportFsCode":"SIN",
  "departureDate":{
    "dateUtc":"2019-08-17T20:30:00Z",
    "dateLocal":"2019-08-17T21:30:00"
  },
  "arrivalDate":{
    "dateUtc":"2019-08-18T09:45:00Z",
    "dateLocal":"2019-08-18T17:45:00"
  },

It takes off from London, on 2019-08-17 at 20:30 UTC
and lands in Singapore, on 2019-08-18 at 09:45 UTC

but then the second leg:

  "carrierFsCode":"BA",
  "flightNumber":"15",
  "departureAirportFsCode":"SIN",
  "arrivalAirportFsCode":"SYD",
  "departureDate":{
    "dateUtc":"2019-08-17T11:25:00Z",
    "dateLocal":"2019-08-17T19:25:00"
  },
  "arrivalDate":{
    "dateUtc":"2019-08-17T19:10:00Z",
    "dateLocal":"2019-08-18T05:10:00"
  },

It takes off, in the past, from Singapore on 2019-08-17 at 11:25 and lands in Sydney on 2019-08-17 at 19:10.

Is is possible that the day doesn't get incremented because the second leg still belongs to the same flight code?


texts: What makes inertial guidance unsuitable for auto-land?

texts:
Above shows the performance of a Lockheed Martin civilian landing system developed in the mid-90s. It works by using the weather radar in SAR mode to update the INS, and the final 100 ft are flown by inertial guidance only.

There was interest from American and European carriers, and certification was underway, the rest is unknown. (Rumor has it, an export-embargo was placed due to the sensitivity of the SAR technology.)

Why can't the inertial guidance on its own fly an automatic landing the last 200 ft, thereby saving the CAT II/III installment?

Flying the final 200 ft in 20-30 seconds should have a maximum worst case scenario error of 3-4 m on a 45-60 m wide runway. It should even be better with today's GPS-coupled INS.

The final update before lock-on can happen either via an ILS CAT I or GNSS/SBAS. With a cross-check against stored runway track heading and glide-path angle. Thus eliminating the need for the weather radar and the runway specific SAR data.

RE comments:

LM, as shown, has done it in 1996 for the last 100 ft. It was for civilian application.
Initialization/alignment is not required, just a position update/check.


texts: If a typical passenger plane had total failure of all engines mid-flight, is it possible for passengers to survive?

texts: I have pretty bad flying phobia and often wonder what would happen if all the engines on the craft went out at the same time. I initially had the anxiety-ridden thought that the hundreds of thousands of pounds of metal would nose-dive and explode into the Earth. Then I read somewhere that the plane would actually glide forward as it descended, making a landing where all passengers survive a possibility. What if you were flying over the ocean versus flat land versus mountains? Has complete engine failure ever happened?


texts: What is the maximum side slip angle that can be achieved by a F-16?

texts:
During which flight regime is maximum side slip needed (apart from take-off and landings in cross winds)? I have learned that during a knife edge maneuver, the side slip angle plays a crucial role in maintaining the flight path angle.

What is the maximum side slip angle that can be achieved by an F-16?
And if possible, how does the F-16 compare to other planes of different roles?


texts: Tapered Wing Providing low Coefficient of Lift

texts:
Hi I am currently analyzing different wing designs using ANSYS Fluent.
One of my designs has a straight leading edge but a swept trailing edge thus it is tapered with wing root chord at 50mm and wing tip chord at length 200mm. Wing span is 250mm. (See Picture)
The airfoil shape used is the S1223 which has a CL max around 2.3. Therefore using the Lift formula which (i know is approximate), I calculate the wing can produce 58.5N of lift at 36.452m/s.

However using ANSYS Fluent I find the wing can only produce a maximum of 39N of lift which is a CL of 1.5.

I am fairly certain the simulations I'm running are accurate but need advice on what could be causing this difference.
Assuming the results I've obtained are correct. What is the reason for the large difference in coefficient of lift ?
Let me know if I need to provide any additional information!
Any help greatly appreciated!
EDIT : Forgot to add that the simulation used assumes the wind tunnel boundary is at wing tip and wing root. Thus the wing span takes up the full wind tunnel.


texts: I'm trying to build a home cockpit for the PMDG 737-800. I'm looking for some landing gear position indicator lights but I don't know where to get them from. I've tried ebay and amazon, but it returned no promising results. The other alternative is of course to make them. Does anyone know where I could have something like this made?


texts: Do airplanes have sensors to detect landing gear fires?

texts: Given that retracting a landing gear that happens to be on fire is a suicidally bad idea, for reasons that should be immediately obvious, do airplanes have temperature sensors on their landing gear in order to detect landing gear fires and prevent burning landing gear from being retracted?


texts: Are there any airliners not made by Airbus or Boeing?

texts:
Are there any commonly used passenger aircraft larger than regional jets (100+ seats) that aren't Boeing or Airbus?

If so, what are they and where are they used?


texts: Is autorotation possible in a tandem rotored helicopter?

texts: I just wonder, whether a synchronized autorotation is possible in case of turbine failure (one or both gas turbine engines). All Gearboxes obviously must turn not to desynchronize -> lethal


texts: What keeps an aircraft engine from flaming out at high altitude?

texts: High altitude atmosphere has lower oxygen level. How do aircraft, especially the military ones, prevent engine flameout?


texts: What lights does the Cessna 172 light rheostat control?

texts:
I am part of a team developing a Cessna 172 P model for FlightGear, an open source free flight simulator. We are now programming how the panel and radio lightning rheostat should work, but we found a lot of unclear and/or contradictory information about it online. Our main problem is to understand how the radio light knob (labelled as RADIO LT) work in these older models of the 172.

The POH from 1982 states the following:

  The engine instrument cluster (if post lights are installed), radio equipment, and magnetic compass have integral lightning and operate independently of post or flood lightning. The intensity of this lightning is controlled by the inner knob on the light dimming rheostat labelled RADIO LT; rotate the knob clockwise to obtain the desired light intensity. However, for daylight operation, the compass and engine instrument lights may be turned off while still maintaining maximum light intensity for the digital readouts in the radio equipment. This is accomplished by rotating the RADIO LT knob full counterclockwise. Check that the flood lights/post lights are turned off for daylight operation by rotating the PANEL LT knob full counterclockwise.

This makes it look like the RADIO LT knob controls both the brightness of the radio digital readouts (i.e. the frequency digits) as well as other types of lights (radio cluster buttons and compass), but I found out that other renowned simulations of the 172 for other simulators do not dim the digital readouts with that knob. It also seems strange to me that one would be able to dim the radio digits under any condition, let alone turn them completely off.

So does anyone here have experience with these models of the 172? Would anyone be able to describe how to best model the behaviour of the radio lights?


texts: Do the F-18's leading edge flaps deflect symmetrically in rolls?

texts: When the F-18 Hornet does rolls, do the Leading Edge Flaps (LEFs) deflect symmetrically or is the deflection different on the left and right LEFs?


texts: Why are high-bypass turbofans faster than turboprops?

texts: The turboprop, and especially the high-blade-count propfan, differs from the high-bypass turbofan principally in throwing away the draggy outer ducting. This makes it easier to obtain a greater diameter, moving more air slower, and hence higher efficiency. Fewer blades further increase aerodynamic efficiency. Tip speeds remain much the same, limited by the speed of sound. So why are turboprops significantly slower than high-bypass turbofans?


texts: Are there any EU/EASA regulations surrounding aviation software?

texts:
A great question's been asked: Is there any U.S. / FAA regulation that could apply for aviation software?

This is interesting to me as a programmer and aviation enthusiast, but being based in the UK,  I'd like to know if there any EASA regulations surrounding the creation of software for use in the aviation industry?


texts: What is the working principle of gravel kits?

texts:
In this answer gravel kits are mentioned. I then looked at the wikipedia page and I noticed that they are quite different from what I was expecting:

I was expecting some kind of "shield", plate or extended inlet on the bottom side of the engine.
Wikipedia says that these instead are

  vortex dissipators, using compressor bleed air

How do they work? How does a beam and a sidewise jet of air prevent FOD ingestion?


texts: How could I find the air velocity and lift force?

texts:
As shown below I have this information as shown below in the picture. I got the density according to the ISA standard  = 1.225[kg/m^3]  and  =  (−0) is calculated as below :

α=−4: CL=0

α=16: CL=0.025∗(16+4)=0.5 according to the diagram below:

I just want to know how to find the velocity and lift force?.

The lift force law is like this =(1/2)  ^2


texts: Are helicopter pilots required to use GPS navigation?

texts: Some helicopter crashes are caused by a disoriented pilot. This would presumably be impossible with a GPS with terrain maps. Are pilots required to use a GPS when flying a helicopter in the US?


texts: In the few rudder incidents with the B737, rudder-freeze caused the airplane to roll. From what I know, the rudder causes yaw while the aileron causes roll. Why in the case of these accidents/incidents would the rudder cause a roll?


texts: What are possible causes for the flaps not deploying on a Cessna 172?

texts:
I would like to seek some expert opinion on why my flaps failed to deploy when I took it to Flaps 20.

I was turning from Downwind to Base when I took flaps 20 and noticed that my speed was creeping past 80kts even at idle power. My instructor took a look outside and that’s when we realised that the flaps were still at the UP position. We tried checking the circuit breaker for Flaps and the other switches, and everything else was normal.

We came in flapless until short finals when the flaps deployed to Flaps 10 when the switch was moved to the Flaps 30 position.

We did some checks on the ground and whenever we took Flaps down, static interference could be heard. It’s as if it was timed to happen the moment the flaps are extended. No static heard when the flaps are raised.

Any expert opinion would be appreciated as I would like to really understand what I am flying. I have checked the POH and it barely says anything, even the Electrics diagrams aren’t helping me diagnose why.

I’m a student pilot with barely 20 hours flight time.


texts: Can pilots tell if a cloud or fog is made out of water droplets or ice crystals when flying through it?

texts:
I understand that clouds can be made out of water droplets or ice crystals. And that fog is nothing else than low-lying clouds.

However, I've experienced fog in a wide ranges of temperatures. I like mountaineering and you often get fog high in the mountains. I've been lucky enough to visit the high mountains of Antarctica and I've also experienced fog there at very low temperatures.

This answer (in the comments) and the fog wikipedia article mention that ice fog happens only at extremely low temperatures (-35 or -40 C). But I think I've experienced fog at those temperatures too. Some times, with the right light I've seen the air filled with tiny crystals, but I wouldn't call that "fog", because it is very thin.

Then, as far as I can tell, all thick fogs/clouds feel and look the same. No matter if they are made out of ice crystals or water droplets. Is that right? Or is there a way to differentiate between ice/water fogs?

Or maybe contrary to what I think, I've never experienced frozen fog.

But, would I notice the difference if I were to ever experience it? How would they feel/look different?

Other sources, like the UK meteorological office say that water always remain in liquid state in fog, no matter how low the temperature is. Is that true? Is it true for clouds too? In that case there would be no such thing as "ice clouds".

One possibility is that ice or water clouds would give rise to different optical phenomena, like sun dogs that are produced by ice crystals, but usually in conditions were they are not dense enough to be considered fog, like in this image:

(Image from Wikipedia page for sun dogs)

So I wonder what's the experience of pilots, as they go through clouds?. When they do so, they know also the external air temperature, which is a plus. Do they see sun dogs or other optical phenomena that differentiate water from ice clouds?


texts: When and why was runway 07/25 at Kai Tak removed?

texts:
Wikipedia states that Kai Tak Airport in Hong Kong originally had two runways, both built under Japanese occupation during World War II:

  ... In 1942, the Japanese army expanded Kai Tak, using many Allied prisoner-of-war (POW) labourers,[9] building two concrete runways, 13/31 and 07/25.

However, by the time Kai Tak was closed in 1998, only one runway (the famous 13/31) remained.  I can find no mention of when runway 07/25 was closed, or why; can someone help answer those questions?


texts: "Fundamental of Aerodynamics" 5th editon, example about oblique shock. Is the author's solution wrong?

texts:
I am reading "Fundamentals of Aerodynamics" 5th edition, J.D.Anderson. If you have the book, go to chapter 9: Oblique shock and expansion waves. Please look at example 9.2, page 618:

Consider a supersonic flow with M = 2, p = 1 atm, and T = 288 K. This flow is
deflected at a compression corner through 20◦. Calculate M, p, T, $p_0$, and $T_0$ behind the resulting oblique shock wave.(I only have problem with $p_0$).

Before see the solution, try to solve this example by yourself, you might need to see the appendices, here it is: https://drive.google.com/file/d/1MX6MASeP8pU-u_4MDjInfKIzPJfUfMaB/view?usp=sharing

And this is the solution from author:

The interesting thing here is: I was reading the note carefully, I still see something wrong here:

And this is my solution for $p_0,2$:

$p_2$ = 2.82 atm

From $M_2$ = 1.21 $\Rightarrow$ $p_0,2$/$p_2$ = 2.489 (isentropic flow, appendix A)

So $p_{0,2}$ = 2.82 x 2.489 = 7.019  atm

You may think the result is the same as the author's solution, but this is just coincident, look at example 9.5, page 620:

Consider a Mach 3 flow. It is desired to slow this flow to a subsonic speed. Consider two separate ways of achieving this: (1) the Mach 3 flow is slowed by passing directly through a normal shock wave; (2) the Mach 3 flow first passes through an oblique shock with a 40◦ wave angle, and then subsequently through a normal shock. These two cases are sketched in Figure 9.14. Calculate the ratio of the final total pressure values for the two cases, that is, the total pressure behind the normal shock for case 2 divided by the total pressure behind the normal shock for case 1. Comment on the significance of the result.

Again, try to solve this example by your own. Author's solution:

My solution:

Case 1: same as author's solution

Case 2:

$M_{n,1}$ = 1.93 $\Rightarrow$ $p_2$/$p_1$ = 4.224 (1)

$M_1 = 3$ $\Rightarrow$ $p_{0,1}$/$p_1$ = 36.73  (2)

(1) and (2) $\Rightarrow$ $p_{0,1}$/$p_2$ = 36.73/4.224 (3)

$M_2 = 1.9$ $\Rightarrow$ $p_{0,2}$/$p_2$ = 6.701 (4)

(3) and (4) $\Rightarrow$ $p_{0,2}$/$p_{0,1}$ = 6.701x4.224/36.73 = 0.771 (different from author's solution $p_{0,2}$/$p_{0,1}$ = 0.7535

$p_{0,3}$/$p_{0,2}$ is same as author's solution

In both examples, you can see what is going on. Am I wrong or Anderson wrong ??
You might think: "Oh, Anderson said that changes across an oblique shock wave are
governed only by the component of velocity normal to the wave." But this holds only for p, T, $\rho$, $M_{n,1}$, $M_{n,2}$. For $p_{0,1}$ and $p_{0,2}$, we must consider the tangential components of velocities.


texts: Why did early 747s have only two or three windows on the upper deck on each side?

texts:
All 747-100s and some 747-200s were built with just three windows on each side of the upper deck.[1] I'm wondering why so few?

Some of the 100s were retro-fitted with ten windows on each side, so clearly the reason isn't structural; nor do I imagine the cost difference would be relatively very much. It seems connected with the original use of the upper deck as a 'lounge' area, but it seems surprising that you'd want a premium area with very little natural light. On occasion Pan Am seems to have been content with just two windows each side.

Was the three-window configuration purely driven by aesthetics, or were there other considerations by Boeing or the airlines?

3-window Pan Am 747-100 upper deck source

10-window Quantas 747-200 upper deck, 1971 source

 source
Pan Am 747s 1969


texts: Do airplanes have vapor recovery systems for refuelling?

texts:
Related to the question regarding pressure refuelling and this one regarding fuel vapors at large airports.

Refuelling an airplane involves putting fuel into tanks which are "empty" but are in fact full of dangerous air-fuel vapors. I do not believe many airplanes use "bladder" type flexible tanks which would avoid the creation of these airspaces.

When fuel goes in, the vapor has to go somewhere else. In contemporary cars, there is a vapor recovery both in the fuel system (activated carbon cylinder) as well as in the fuel nozzles.

If I understand both pressure refuelling as well as regular refuelling systems for airplanes and airliners, neither seem to have any sort of vapor recovery system. Wouldn't this be a considerable source of greenhouse gas emissions, let alone a tremendous fire hazard? Or is there a vapor recovery system being designed or implemented to mitigate this.


texts: Is there an engine thrust level limit for deploying thrust reversers?

texts:
Does an engine have to be at idle thrust for the reversers to deploy? If the engine is at higher than idle thrust, will it slow down to deploy the reversers and then speed up again, or can it just deploy the reversers at the higher thrust?

I am also asking about turboprops going into beta range.

I had this question based on the discussion on this question:

What to do when you accidentally land on a runway thats borderline long enough to land on?


texts:
I was doing research about jet engines, and they seem really difficult to fully understand. So, can anyone explain it in a simple way?

An afterburner glows on an F-15 Eagle engine, source: Wikimedia.

How do jet engines work?


texts: What is the theoretical maximum RPM of a typical aircraft piston engine?

texts:
Given a standard 6 cylinder horizontally opposed engine like the Continental IO-550 or Lycoming IO-540, the maximum RPM for those engines is 2700 RPM. That's due to keeping the propeller tip speed under the supersonic range.

But what is preventing these engines from turning at a higher RPM for another, non-aircraft use?

I'm thinking if they would work up to around 5000 RPM or so. Maybe the fuel mapping must be modified? Will the valvetrain start to float at that RPM? The application would be automotive, so the load would be far, far less from a duty cycle standpoint then an aircraft application: basically, 5000 RPM would only be seen for a second or two at a time under full (or nearly full) load.

Is there anything else I'm missing? I realize this is a weird question, just doing some thought experimenting.


texts: Is there information available about an aircraft incident from New York to LHR in 2004?

texts:
I am attempting to find some form of incident log regarding a flight I took i 2004 (I believe May/June).  I believe it was a British Airways flight but it may have been operated by another airline.

I was on a flight from New York (I think JFK) to LHR when we had to divert to a runway in Bangor, Maine due to a cockpit fire, I seem to recall being caused by an Air Conditioning Unit.

I can't seem to find any details online about this incident.  Does anyone know of any resources I could use to locate this?  It was in the Bangor Daily News at the time but I've searched their site and can't find any info.

It seems to me that this wasn't "major" enough of an incident to be on any main logs, etc.


texts: Does jet engine exhaust velocity relative to itself remain constant despite speed changes?

texts:
Maybe this is a stupid question.

I seem to have been told, the velocity of the exhaust leaving an airbreathing jet engine relative to the engine, is constant despite changes in airspeed. However, to my understanding:

The ram effect causes air pressure to rise within the engine.
This higher pressure can then be converted right back to velocity with a nozzle.
This velocity adds to the velocity given by the fuel.
For an airbreathing engine with no friction or other losses in the ducts, this means that the exhaust velocity relative to the engine increases with airspeed.
meaning that the reason why we use low-bypass turbofans for supersonic aircraft is to reduce weight and intake losses, NOT propulsive efficiency
and this is what is shown by some attempts to develop low-loss supersonic through-flow turbofans of higher (around 2) bypass ratio.
in short: the statement only makes sense for rockets, which carry their own reaction mass, not airbreathing engines, which ingest reaction mass with any kinetic energy it contains, which cannot simply disappear.

So, what am I missing?


texts: Even after years of research, why are planes unable to keep passengers alive in case of a fiery crash?

texts:
Aviation dates back to the 18th century, and since then tremendous research has been put into making aircraft safer and more efficient. Though these efforts have resulted in better aircraft, why are they still not strong enough to keep the passengers alive in case of a fiery crash?

In recent times, especially, it's a rare incident that a plane crashed and even some of its passengers survived. So, why has this issue not yet been resolved?


texts: Is it possible to build an ultralight helicopter with electric motors as its main engines?

texts:
So I'm trying to make an electric ultralight helicopter, but I'm not sure if it will work. Is it possible to use electric motors to make it fly? If yes, I'm going to need some advice.
I'm expecting the aircraft to be able to lift a 200kg load, with the maximum rotor blade diameter of 7m in coaxial rotor configuration.


texts: What are the advantages of using a ramjet in an air-to-surface missile?

texts: Which are the advantages of using a ramjet compared to a rocket engine in an air-to-surface missile? I suppose the cost rises a lot, so why do some countries use ramjets as a way of propelling ASM missiles?


texts: What is the crank on the ceiling of this aircraft?

texts:
What is the crank the pilot is operating above his head? Also what type of aircraft is this?

 image source


texts: Why A320/330 use C* FBW control without speed stability?

texts:
The A320 and A330 family are FBW aircraft that use C* longitudinal control laws for longitudinal sidestick command tracking. In essence, stick neutral commands 1G flight. When stick is deflected longitudinally, a blend of pitch rate and normal load factor is commanded to provide a consistent G-feel to the pilot; once the stick is released, 1G flight resumes, but the airplane is steady-state at the new pitch angle (or flight path angle to be more exact).

Unlike B777, B787 and A220, however, the A320/330 family do not have artificial speed stability. Once the aircraft is steady-state at the new pitch attitude, and with the autothrottle disengaged, the airspeed will settle to a new trim point. In another word, unlike a conventional aircraft, the A320/330 only has neutral speed stability.

This is why the envelope protections of the Airbus aircraft are not nice-to-have features, but essential features to ensure the airspeed does not rapidly bleed off to stall or increase to overspeed, all while the stick is neutral.

My question is, why is a C* control law without speed stability desirable for a transport category aircraft? The A320 does not need to perform precision target tracking as a fighter aircraft would, and it changes the flying characteristics drastically from those of a conventional aircraft.


texts: what are the advantages and disadvantages of tilt rotor vs ducted jet engine for a VTOL aircraft?

texts:
Please could someone summarize the main advantages and disadvantages of a tilt-rotor (the V22 Osprey) vs jet (F35) system for VTOL. I have been trying to look into this but found details very sparse and not in comparison to each other.

Among other advantages and disadvantages I am very interested in

speed
energy efficiency
ease of maintenance and why.


texts: Can a plane land on an aircraft carrier without support from its crew?

texts: Imagine a scenario where a carrier was dead in the water. No-one inside. Could a plane land on the carrier? What would such a procedure look like potentially?


texts: Does the flight always switch to TRACON on a go-around in class B airspace?

texts:
I have been listening to class B go-around ATC recordings.  After the initial climb of the go-around, the tower gives the flight a heading and altitude.  Then, on some recordings I hear the tower say "contact departure" and a frequency.  But on others I don't hear that.
I can't tell whether:

It's optional for the tower to hand off the flight to departure in a
go-around and the tower can keep control the whole time until they
land, or

The tower always switches the flight to departure, but sometimes
that hand-off is left off of the recording.

Which is it?


texts: When and how do I align with the runway during an offset ILS approach?

texts:
In X-Plane 11, when landing an A330 on 04R at Nice (LFMN) on an ILS approach, the aircraft is brought perfectly to the end of the runway but because this is an offset ILS the aircraft is at about 2° to the centreline.

My question is at what time and with what technique (rudder or aileron) should the aircraft be aligned with the centreline? I always seem to over-adjust and struggle to avoid wing tips touching the ground.


texts: What is the difference between an Airbus A330-200 and an A330-243?

texts:
I am just curious to know the difference between Airbus A330-200 and A330-243.
Sri Lankan Airline A330-243

Sri Lankan Airline A330-200


texts: Who can carry out airworthiness inspections?

texts:
My understanding is that aircraft regularly have inspections for defects just like cars in the U.K. have an annual MOT test to check their condition and safety.

My question is, who can do these inspections and what qualifications/certifications do they need?

I'm primarily interested in CAA requirements but FAA requirements would also be interesting to know.


texts: How do we find the breaking point of an old braced wing?

texts: I was curious about how to find the maximum g's an old plane like the Spitfire (c-wing) could endure, given all realistic factors. Since the Spitfire's wing, in particular, was quite thin and braced with wood for most of its variants how much positive and negative force could it withstand?


texts: Can aileron differential eliminate adverse yaw?

texts: Can aileron differential completely eliminate adverse yaw?


texts: Why do the RNAV (GPS) approaches to KAPC not use the same missed approach procedure as the ILS/LOC approach?

texts:
While looking at the various instrument approaches for Napa Valley (KAPC), I noticed a discrepancy between the RNAV (GPS) Y/Z RWY36L missed approaches and the ILS/LOC RWY36L approach:

Why is it that the ILS approach is able to use a turning missed approach to keep pilot and plane clear of the high ground to the north, but the RNAV approaches to the same runway force you to either have visual contact with the high ground early, or outclimb it?  To me, it'd make more sense to have the RNAV procedures use a similar missed approach to the ILS, as then you could have an all-aircraft RNAV procedure with low minima, vs. one with high minima that works for everyone and one with low minima that requires a significant (more than twice the norm) missed approach climb rate.


texts: Currently I am investigating the feasibility of transmitting a limited amount of FDR data via radio link for domestic flights within continental USA. I am working on building a prototype system in which I need to connect the FDR with a computer. USB interface is the most appealing one. I am using a small Flight data recorder (FDR) which has a USB interface. However, it is for hobby planes. Is there a USB interface for FDR's in the passenger planes? Or something that converts between ARINC and USB?


texts: Are Crew Resource Management (CRM) and other Human Factors methods effective?

texts: I help in giving human factor training in both the start up phase and in the biennial continuous training. I am a bit tired of my students...especially those in aviation long term, being disillusioned in this subject. I have tried to find statistics or information where I can show that sitting the human factor training has in fact helped in the prevention of accidents and incidents in the maintenance environment. But have been unsuccessful in finding this information. Wondering if anyone knows where I could find this? Thanking you in advance. :)


texts: What is the definition of "occupant" in 14 CFR 91.307?

texts: Does a solo pilot performing aerobatics constitute an "occupant" for the purposes of requiring a parachute per 91.307(c)?


texts: Which map projection is typically used on ATC radar screens?

texts:
Displaying a (roughly) spherical surface on a flat map turns out to be pretty difficult. There are many different map projections, each with their advantages and disadvantages. Some of the most common ones are cylindrical (Miller), conical (Lambert) and azimuthal.

On aviation maps and charts, I often see the Lambert conical projection used. This made me wonder: on an ATC radar screen, which projection is typically used? It is important that the controller can easily estimate both headings and distance by looking at the screen. For large sectors especially, an inaccurate projection might make this difficult.

Clarification: The discussion of whether the choice of projection will have an operational impact at all is an interesting one. My question, however, is not about how important the choice of projection is, but rather what projections are commonly used. I have a professional interest in this, even if the choice of projections is not operationally important.

Maybe different standards are used in different companies or different regions of the world. If that is the case, a brief summary of the most commonly used standards would be appreciated.


texts: Why did some Spitfire variants have their wings clipped?

texts: Some Spitfire variants have clipped wingtips instead of the round, elliptical wingtip. The reason for this is to increase the roll rate and low-altitude performance. My question is: How would clipping the wings of an aircraft increase its low altitude performance?


texts: What is the purpose of logo lights on airliners?

texts: Why do modern airliners use lights to illuminate the sides of their tails and illuminate the airline's logo?  Is this just done to give ground and tower controllers an easy way to differentiate between multiple jets on the ground during night ops or direct them to the appropriate gates e.g. Delta flights to Delta terminal, Qantas flight to Qantas gates, etc.?


texts: What is the maximum fuel amount that fits into the rare Boeing 737-700ER version?

texts: Title is self explanatory: what is the exact maximum fuel amount that fits into the still rare-to-see Boeing 737-700ER version?


texts: What are the defining characteristics of aviator glasses?

texts:
The title pretty much says it all.

It's easy to find pages for resellers of aviator glasses or aviator sunglasses, but what are the defining characteristics of these as compared to ordinary glasses or sunglasses?

If one were to buy from an ordinary optician not specializing in aviator customers, what should one look for or ask for to get "aviator" glasses? Correspondingly, what should be avoided?


texts: How do you request a 3D block of airspace to to freely maneuver your privately owned military jet?

texts:
Referring to this How can you fly your own military jet in terms of altitude and acrobatics? how can you request a block of airspace to freely maneuver your private military jet (barrel rolls, vertical climb, pulling Gs, etc..).
If that kind of block of airspace is indeed possible to be permitted, what are your limits flying your jet in it?


texts: How do airlines handle their non-standard passengers for the load control process?

texts:
How are non-standard passenger weights maintained in the systems?
How they do they handle these passenger weights between check in and load control system and etc..


texts: What do you do when your engine quits right when the airplane starts off the ground?

texts:
This has been one of my fears in flying (a plane the size of Cessna 152). I sort of know what to do when the engine quits on you when you are a few hundred feet off the ground, although it is definitely not easy to manage. However, lets say you are just past the rotation speed and have very little runway left. Is there anything you can really do other than cut power, retract flaps and try not to set your brakes on fire?

Edit: I am assuming that I am barely 10 feet above the runway. I suppose this is a more specific version of the general case of engine failure at lift-off.


texts: Is the official weather report for an airport in Class D airspace controlling for its Class E surface extension?

texts:
If the official weather report for an airport for which Class D airspace is designated is showing IMC, is that controlling for a Class E surface extension (designated for that airport)?

For example, if I determine that I have 3 miles flight visibility and at least a 1000 ft. ceiling, can I fly through that Class E surface extension without receiving an SVFR clearance?


texts: What is meant by "Outbound leg timing begins over/abeam the fix, whichever occurs later" in FAR/AIM 5-3-8?

texts:
In FAR/AIM, 5-3-8. Holding part, There is a sentence that says

  (b) Outbound leg timing begins over/abeam
  the fix, whichever occurs later.

I got to know that the word 'over' is for parallel or teardrop entry. But I still can't understand the intention of 'whichever occurs later'.

Could anybody explain this more specifically?


texts: Why were the TWA TriStar middle seats smaller than the aisle seats?

texts:
I was watching an old TWA advert and a question came up:
why were the L-1011 TriStar middle seats smaller than the aisle seats?


texts:
Source

Why was this cockpit much more complex than any other modern day aircraft or a fighter jet? It looks to have many more buttons and controls, and very small (interesting) screens. Also, its steering was much different than you would see in any other aircraft.


texts: Just how much power (as a percentage) is necessary to drive a compressor in a jet engine?

texts: If i understand correctly this is the "back work ratio". I'd like to know how much % of the "gross" thrust is used by the turbine to drive the compressor in a typical turbofan.


texts: What is the correct go-around procedure in a PA-44?

texts:
I wanted some advice on a procedural-type question. In the PA-44 (Piper Seminole) go-around procedure, it is listed as follows:

  MIXTURES ............................................FULL RICH
  PROPELLERS ............................................ FULL INCREASE
  THROTTLES.............................................FULL OPEN
  Control Wheel...........................BACK PRESSURE TO OBTAIN POSITIVE CLIMB ATTITUDE
  FLAPS....................................................RETRACT SLOWLY
  GEAR.........................................................................UP
  COWL FLAPS........................................................... AS
  REQUIRED

(You can find this on any online version of the PA-44 PIM - here's an example on page 4-17.)

Now, the way I have always been taught is to go full throttle, carb heat off (not listed in PIM), flaps 40°->25° immediately, then 25°->10° at positive rate, and 10°->0° upon being above Vy, then gear up, and cowl flaps open.

I began researching the Airplane Flying Handbook and it states in the Transition to Multi-Engines section (page 12-18) that:

  With sufficient airspeed, the flaps should be retracted from full to
  an intermediate position and the landing gear retracted when there is
  a positive rate of climb and no chance of runway contact. The
  remaining flaps should then be retracted. [Figure 12-10]

My question is this: would a better go-around procedure be full throttle, carb heat off, bring the flaps to 25°, then gear up, then continue as previously specified? This would reduce the drag the gear is giving a lot sooner, briefly take advantage of the increased lift coefficient 25° degrees of flaps gives (that is the specified flap setting for the short field take-off), and also follow the AFH procedure.


texts: What happens in a turbine high-temp combustion?

texts: I'm designing an aircraft, and I notice that in high bypass turbofan engines, the fuel is used at relatively low temperatures. So I'm wondering, what happens if the fuel is burned at high temperatures? Does something happen to the metal?


texts: How to calculate angular velocity and radius of a turn?

texts:
How can I calculate with known tangents of different angles and by rules of thumb?

Which formulae should I use for fps and NM?


texts: Why do some airlines have different flight numbers for IATA and ICAO?

texts:
Most of the time when I see flights on either flightradar24 or flightaware it doesn't matter whether you use the 2-digit IATA code or the 3-digit ICAO code, the flight number is the same, i.e. a flight will be listed as UA1234/UAL1234.

But some airlines show different flight numbers for IATA and ICAO. Just picking a couple of random flights I can see on Flightradar24:

SunExpress flight XQ231/SXS5J
Pegasus Airlines flight PC398/PGT35R
Turkish Airlines flight TK656/THY3YE

I've also seen this on RyanAir (FR/RYR) flights. Why do the IATA and ICAO identifiers have different flight numbers?


texts: Can you turn off the instrument panel lights?

texts: Do general aviation aircraft generally allow the turning off of the instrument panel lights? By lights I am referring to any screens, bulbs or other devices which shine a light within the cockpit.


texts: What are those 5-character alphanumeric waypoints?

texts: On the following High IFR chart from skyvector.com I notice along the meridian at 30' intervals there is a green symbol the same shape as an RNAV waypoint. Next to them are 5-digit identifiers, but it is alphanumeric rather than the usual 5-letter fix name. What are these symbols and what are they used for? Can they be entered into the FMS?


texts: Why do blimps have fins? Can't the two (or so) engines already control direction?


texts:
What do you know about yaw control and more precisely about the result caused by the rudder (R on picture)?

Below the right pedal of the airplane has been depressed, and the rudder creates a rotation around the yaw axis and generates an aerodynamic result (R on picture) to the left on the vertical tail. Can you develop how this result is create?

https://www.lavionnaire.fr/CelluleGouvernes.php


texts: What is the purpose of the selected altitude/airspeed in ARINC 429?

texts: What is the purpose of the selected altitude and airspeed fields in ARINC 429?


texts: Is it allowed and possible to hold at the intersection of two VOR radials using a single VOR receiver?

texts:
First of all, is it permitted? I am practicing VOR tracking on my simulator and the missed approach procedure (KLGB VOR 30) takes you out to an intersection off two VOR radials. Since the plate doesn't specify "DME required" I figured yes.

Assuming yes, are there any tricks/protips to doing this successfully?


texts: Is there a difference in aerodynamic efficiency between single engine and twin engine airplanes?

texts:
I've learned a lot of great information about aviation on this website. One insight I learned from a poster here is that, all else equal, for every doubling of engine power that you give an airplane, speeds increase by about 25%.

However you're not always comparing "all-else-equal" airplanes, for example sometimes I want to compare between a single engine airplane a twin engined airplane. Yes the second engine adds weight and drag, but the factor that I have the most trouble accounting for are the difference in aerodynamic requirements between the airplanes.

My understanding is that regulations require all single engine airplanes to have a stall speed of no greater than 61 knots, while a twin-engine plane could have an arbitrarily higher stall speed. The higher stall speed is directly correlated with higher aerodynamic efficiency, meaning that it should be able to achieve higher speeds than a single engine airplane of the same mass, drag, and power, would be able to achieve.

So I am looking for a simple rubric with which to be able to compare single and multi engine airplanes. I think that there are really two parts here: (1) identify realistic stall speeds for the multi-engine airplane and (2) formula for comparing top speeds between planes with X mass and drag and Y power and Z stall speeds.

Any ideas?


texts:
I wonder what jobs I can get if I have ppl and cpl but no atpl?
is it possible to earn money from holding these licences?


texts: will a Sears-Haack body straighten itself out if "launched" sideways?

texts:
I'm asking this here not because it's a question about flying a plane but because I read some engineering questions that said to bring aerodynamics questions to aviation.se for the best results.

Will a Sears-Haack body straighten itself out if "launched" sideways? Let's say it's launched from space toward the earth and hits the atmosphere at supersonic speeds. Even if it "hit" air side-on would it straighten itself out? (That is -- one of the pointy-sides now at the front) And if so would it happen in a quick/undramatic way so that the spaceship launching it would have a reasonable chance of hitting an intended destination?

If not, would the addition of fins to one end make it more likely to right itself as it hit the air?

--I guess this question boils down to: "will an object moving at high speed find and stay in its most aerodynamic orientation?" and then: "if not, will a major control surface like fins make it do so?"


texts: How does the flap configuration affect the tailstrike limit on the A320 aircraft family?

texts:
The configuration that provides the maximum FLEX temperature varies with the runway length.

On short runways, CONF 3 usually provides the highest FLEX temperature, and the tail clearance at lift off does not depends on the configuration.

On medium or long runways, the second segment limitation becomes the limiting factor, and CONF 2 or CONF 1+F becomes the optimum configuration, in term of FLEX temperature.

In these cases, the tail clearance at lift off depends on the configuration. The highest flap configuration gives the highest tailstrike margin.

How does the flap configuration affect the tailstrike limit?


texts: Do wheels continue spinning when gear retracted?

texts: Do landing gear wheels continue spinning inside the landing gear compartment once the gear has been retracted or is there a mechanism that will stop them?


texts: What ILS type approach my flights landing could be?

texts:
I had one of the foggiest landing experiences recently and I'm interested if any of you could guess what type of ILS could it be like CAT I,II,IIIA or IIIB?
So the METAR issued 9 minutes before my flights touchdown stated RVR as 100 meters and the METAR issued 21 minutes after the landing stated RVR 750 meters.
The aircraft type is A321NX IndiGo Airlines and Airport VILK the RWY is 27.
Here are the METAR and TAF reports ..it could be wrong but I have just tried to gather them with the information I had so I'd love If someone could decipher it for me please !
METAR REPORTS
(After Landing and Deboarding)
SA 02/02/2021 03 : 30
METAR VILK 020330Z 00000KT 0100 R27/0750 FG NSC 11/08 Q1020
BECMG 0150 FG=
(During Approach and Landing) [Touchdown at 03:09]
SA 02/02/2021 03 : 00
METAR VILK 020300Z 00000KT 0000 R27/0100 FG VV/// 08/07 Q1019
NOSIG=
(During Holding Pattern)
SA 02/02/2021 02 : 30
METAR VILK 020230Z 00000KT 0000 R27/0075 FG VV/// 08/06 Q1019
NOSIG=
Below are the TAF reports for the flight -:
TAF VILK 020200Z 0203/0212 VRB02KT 0050 FG VV///
BECMG 0204/0206 0800 MIFG FG NSC BECMG 0207/0209 32004KT 2000 HZ=
TAF VILK 012300Z 0200/0209 00000KT 0200 FG VV///
BECMG 0204/0206 0800 MIFG FG NSC BECMG 0207/0209 32004KT 2000 HZ=


texts: Do people get less airsick if cabin pressure is at 6000 ft.?

texts: This is in relation with a question I asked yesterday . This is part two of the question. Do people feel less discomfort. Whenever I'm traveling on planes, at times I feel strain in back of the head, sometimes my ears get closed, sometimes the throat,nose either get fully dried or they start to blow. Would a lower cabin pressure help in any of those things ?


texts: Were stub wings on early flying boats designed or able to exploit ground-effect lift?

texts:
I came across a link to the Dornier Do X, and the Boeing 314 Clipper in another question, both aircraft have similar short wings/floats low on the fuselage, described in one wikipedia article as "stub wings"

Were these stub wings designed to exploit ground effect to aid take of and landing (or could that have been an unintended advantage)? Or is the ground effect of these small wings likely to be irrelevant relative to the full size wings.

The wikipedia articles linked imply their main function was for stability in the water and use as landing stages for embarkation. But they seem reminiscent of the wings of some ground effect aircraft or ekranoplans such as the A-90 Orlyonok


texts: Why fuel left/right when C172 is secured?

texts:
The C172 POH checklists say to set the fuel selector to "right" or "left" when securing the plane but "both" while operating the plane.

What is the point of changing the fuel selector when the engine isn't running? IOW, what practical (not legal) problems could it cause to leave it on "both" while secured?

[Edited to remove incorrect understanding of the vent connection between tanks, which is cleverly designed to not cross-feed fuel.]


texts:
I understand you pay to land at an airfield, but do you pay to Touch-and-Go?

Pilots will often practice many Touch-and-Go's at an airfield, are you billed for each one (assuming you pay something to use the airfield's resources for the Touch-and-Go procedure).

How are you charged if you don't do a full-stop at the field (practicing at another airfield different from your home base)?


texts: What level of liability should a GA renter's insurance policy have?

texts:
As a GA pilot who rents planes occasionally, I am looking at buying a renter's insurance policy so that I'm covered against the injury of any passengers as well as damage to the aircraft.

For bodily injury, I based the amount off of my car insurance. That is, in the neighborhood of $100,000/person. Is that assumption correct?

What I don't know is what level of aircraft damage liability is an acceptable amount. I mostly fly Cessna 152s, 172s, and Piper Warriors. Of course, it isn't worth paying for a liability that is more than the plane is worth. So what would be a good level of liability to be covered for?

Further, I understand that an FBO will have insurance on its planes. However, this insurance is to protect the FBO, not the pilot. Should the FBO's insurance affect the level of insurance I, as a renter, choose?

For reference, here are Avemco's current annual damage liability rates for single engine planes:

Limit      Premium
-------------------
$1,000     $60
$5,000     $120
$10,000    $155
$15,000    $210
$20,000    $220
$25,000    $275
$30,000    $310
$35,000    $365
$40,000    $415
$45,000    $465
$50,000    $500
$55,000    $540
$60,000    $560
$65,000    $605
$70,000    $675
$75,000    $725
$80,000    $745
$100,000   $925
$150,000   $1,400


texts: Why is the rotor system of an aircraft and the rotor system of a helicopter different?

texts:
Both aircraft with propeller(variable pitch) and helicopter rotor system can change pitch.
Of course, for helicopter, there is not only collective pitch control but also cyclic control.
The aircraft rotor system seems to be heavy because it uses hydraulic.
With the exception of the cyclic control of the helicopter, it seems lighter and simpler to use the helicopter's rotor system on an aircraft.
I would like to know what happens when we replace the aircraft's rotor system with helicopter's rotor system.


texts: How a customer could choose "A330-Neo" or "A350 Regional" on shorter routes?

texts:
According to Wikipedia, Airbus is studying a new A350 Regional that effectively is a think that I suggested some time ago when I asked "Why is the A330neo more efficient than the A350 on shorter routes".

In that question I said:

  why for shorter routes A330neo is more efficient than A350? Could not
  be enough to have an 350 with lower fuel capacity (in case shorter
  length) and maybe reduced engine power (the opposite of higher power
  in A350-1000) thanks to reduced weight?

Now, it seems that with this model Airbus is creating a more evident overlap in its proposal to market for shorter routes because, as written in A330neo Wikipedia page, is written:

  A330neo enables profitability on shorter ranges where the longer-range A350 and Boeing 787 aren't optimized.

So what reasons could push a customer to choose to A330-Neo or A350 Regional on shorter routes?


texts:
It's on a Lockheed Martin banner showcasing the company's iconic planes. The plane to the left on a crimson background is the U2, and the plane to the right on a blue & tan background is the C130.

It looks like a prototype UAS.