texts: Does the Cessna 208B still require a part 23 waiver to operate with 14 seats?

texts:
The selected answer to this question refers to the applicability of part 23 to aircraft of nine passengers or less. Other countries certified the 208B with as many as fourteen passenger seats, using a waiver to allow the extra seats while relying on the FAA nine seat single engine certification base. The FAA normally required aircraft with ten to nineteen seats to be multi-engine.
The part 23 rewrite allows certification using ASTM standards, which provides for "level 4" occupancy of up to nineteen seats, and has a propulsion matrix with space for level 4 single engine aircraft. If the 208B were certified using the ASTM standards, would it still require a waiver to operate with more than nine passengers outside the US? Would it now be legal to operate this way inside the US under part 135?


texts: Where can I find climb and cruise performance charts for a specific aircraft?

texts: I'm looking for climb and cruise charts for a cirrus sr20 G3, but I can't find them in the POH?  where are these charts typically located?


texts: Is there any example of a US VFR sectional chart containing both a reference to "Class E" airspace, and to older terminology for the same airspace?

texts:
Is there any example of a US VFR sectional chart whose legend describes the  airspace depicted by the thin dashed magenta line both as "Class E"  or "Class E airspace", and also with the older terminology "Control Zone at airport without control tower and Control Zone extension without communications requirement", or similar?

Based on old sectional charts I've looked at-- and new batches of chart updates become effective on a 28-day cycle-- this would have happened no sooner than 28 days after August 19 1993, and no later than 28 days before November 11 1993.  So it appears that the only possible dates for such a situation are Sept 16 1993 or October 14 1993.

In answering this question please disregard any reference to non-US airspace on the legends of US VFR sectional aeronautical charts.

Note that this related answer to a related question Re old (1992) US VFR sectional charts-- when was the thin dashed magenta line first used? clearly describes an INTENTION to have dual legends (including the old and new airspace terminology) on aeronautical charts between October 15 1992 and mid 1994.  But was this ever actually done on US VFR sectional charts?  Checking charts with effective dates of Sept 16 1993 and Oct 14 1993 should settle the issue.


texts: Can an aircraft flying VFR with a squawk code enter adjacent class C or D airspace after being handed over to the destination tower?

texts:
In the US, a VFR aircraft request VFR flight following and is given a squawk code after takeoff.
15nm before arriving at it's destination class D airport, the TRACON facility instructs the pilot to "contact the destination tower".
The pilot keeps his squawk code and change frequency to contact the destination tower. The tower instruct the pilot to enter "straight-in" for the runway in use. However, in order to enter straight-in, the pilot must briefly transit through the class C shelf of an adjacent airport and through the class D of another airport not far from the destination.
Q: Is the pilot cleared to transit through both adjacent C and D airspace since he still squawking the code provided by the local TRACON?
I understand the legal requirements to enter each airspace (AIM 3-2). If the pilot was still in contact with the TRACON facility he would be cleared to enter adjacent C and D airspace since he is squawking a discrete code AND previously established two-way communication. In this case however, the pilot is not anymore talking to the TRACON and switched to the destination tower. I cannot find an official reference that covers this particular scenario.
I came across this question/answer, Does Flight Following automatically include permission to fly through class C or D airspace?, before posting but my scenario is different since the pilot is not talking to the TRACON anymore. It's subtle but makes a big difference.


texts: How do I estimate piston aircraft fuel efficiency?

texts:
Is there any way to figure out or calculate fuel consumption of piston engines for aircraft? I'm looking at different engines in a book, and while jet engines have useful values like thrust, bypass and pressure ratio, piston engines only have power output and weight.
Propeller efficiency plays a role here, I guess, but it's not at hand so I assume all engines use the same propeller in this case.
Would the easiest way to calculate such a number be to find the maximum fuel capacity and range and from there find out how much fuel each engine uses per hour?

I've asked a similar question before about turbojets and turbofans and received good answers - sadly, piston engines are completely different...

EDIT: To clarify, I am looking at airliners powered by piston engines and wish to compare them.


texts: What are the differences between the Avro RJ85 and the BAE 146-200?

texts: As far as I understand, the Avro RJ is a newer version of the BAE 146? What are the exact differences?


texts: Why are the engines of the Airbus A400M slightly tilted down?

texts:
Picture: Youtube.

Firstly, are the engines really tilted down? I have tried to check another picture over the net, seems they are really tilted down slightly. But need confirmation from you experts, however.

Second, if it is true, what is the reason?


texts: Why and how were "eybrow windows" helpful in tight turns?

texts: It is written in some answers that "eybrow windows" were helping pilots in "tight turns". How did this work? These tiny windows seem located right above the head, so I would not expect to see anything else than the sky right above through them, regardless if turning or not.


texts: Maximum/Lowest achievable expansion ratio (generally) in a turbine?

texts:
Let's think about a turboprop with a single shaft. The turbine moves the compressor and the propeller.

My question: what is the "limit" to the expansion ratio achieved by the turbine?

If we call $5$ the air that is exiting the turbine, and $4$ the air that enters the turbine, then the expansion (or compression) ratio is defined by: $$\pi_t\equiv \dfrac{p_{05}}{p_{04}}<0\Longleftarrow \left(\textit{Because air is expanding}\right)$$

But for a non-ideal, single-stage axial turbine this ratio can be related to $T_{04}$ (that is, the temperature at the burner exit) by: $$\pi_t=\bigg[1-\dfrac{W_t}{c_p\eta_tT_{04}}\bigg]^{\gamma/\left(\gamma-1\right)}\quad \text{where}\quad \gamma\approx 1,35>0$$ where $W_t$ is the specific energy extracted from the fluid by the turbine.

On the one hand, as $T_{04}$ increases, $\pi_t$ will increase as well.

But on the other hand, I think we are interested in $T_{04}$ as high as possible BUT $\pi_t$ as low as possible, which comes into direct contradiction right? (Please, correct me here if I'm wrong).

What is the compromise solution between $T_{04}$ and $\pi_t$? If we make $T_{04}$ too high (which is thermodinamically convenient) then $\pi_t$ will be higher than its optimal value, and the other way around.

EDIT:

$T_{04}$ has itself a structural/thermal limit (if it goes too high, it can ultimately melt and/or generate way too high pressure on the turbine blades until it breaks). I think this defines a maximum value for $\pi_t$, right? Although knowing the maximum $\pi_t$ I think doesn't make sense, because we want to minimize it.


texts: Why doesn't the landing gear get raised on the first flight of a new airplane?

texts: This image shows the A350 first takeoff high in the air and the landing gear is still down. Why didn't they retract it?


texts: Is it allowed to let the engine of an aircraft idle without a pilot in the plane. (For both helicopters and aeroplanes)

texts:
Is it allowed to let the engine of an aircraft idle without a pilot in the plane. (For both helicopters and aircr).

Would there be a difference between a C172 and a 737?


texts: Do modern airliners have a flaps warning indication?

texts:
Years ago I was on a flight from San Francisco to Los Angeles, a 737 if I remember rightly, and was sitting just behind the wings and could not help noticing the flaps were partly extended for the whole flight.

I thought they looked odd out the window but did not bother mentioning it to the cabin crew since I was not sure what I was seeing. However, on landing in LA, the pilot retracted the flaps after using them for landing, and they were then correctly seated.

I assume the pilot felt something was off, since after landing I could see ground crew wandering around and inspecting the aircraft with puzzled looks on their faces.

I understand that the flap controls are a bit out of the pilots normal sight lines and this got me wondering whether there is instrumentation in the cockpit that alerts the pilot to the fact that the flaps are not fully closed once in normal cruise attitude. Perhaps even an indicator similar to the landing gear lights.


texts: How does the GE H75 eliminate the need for hot section inspections?

texts: Operators of the Pratt & Whitney Canada PT6 will be familiar with the need for hot section inspections half way to TBO. General Electric is touting the lack of hot section inspection requirements for their GE H75 engine. How did GE eliminate the need for the added inspections?


texts: What are the disadvantages of using just rudder to roll an airplane?

texts: Ultralights with slight dihedral will roll and yaw on rudder input (e.g the Bloop 3, Maxair Hummer) so some don't have ailerons for the sake of simplicity. Is this kind of control input advisable, or are there disadvantages?


texts: Why can’t electric motors be used in aviation? Is it a problem with batteries, torque, or what? From what I’m aware motors at high torque are expensive and need a massive footprint, than a high rpm low torque motor. Is the issue the weight and size of a motor to lift 500,000 pounds off the ground? We have motors right now that can spin a turbo fan at a high speed and compute a comparable thrust, but is that thrust under load a different story? Is the energy required way too much for a realistic battery size?


texts: Do I have to notify ATC if I go-around when I was cleared for a touch and go?

texts:
If I was cleared for a touch and go and go-around on short final or just before touchdown, do I have to notify ATC?

I still would have made a takeoff after the touchdown during a touch and go, so it's basically the same when I start the climb a few seconds earlier isn't it?


texts: What factors made my flight land at runway 02 in El Prat?

texts:
Aircraft normally land at Barcelona's El Prat airport using either of the 25 runways, along a flight path hugging the coast, with a flip to the 07 orientation generally associated with bad weather.

Earlier today, though, my flight landed on a cross runway, 02, which I never knew existed, with a flight path at a rather steeper angle to the coast; there is some light cloud cover but nothing to write home about. What factors drive the change to this mode of operation? I'm interested both in the general criteria and in the specific conditions tonight.

And, more generally, what are the standard resources (or types of resources) that one should use to find out this type of information?


texts: What training is required for pilots conducting ASETPA operations?

texts: In Australia, aircraft approved for ASETPA operations are certain single-engine turbines allowed to be operated commercially under IFR. While I understand that the manufacturer is required to meet a series of requirement, I'm not so sure about whether the pilots in ASETPA operations need special training or approval. Is extra training and/or testing required, and if so, how extensive is it?


texts: How realistic is the plane scene in Captain America: The First Avenger?

texts:
In Captain America: The First Avenger, there's a scene in which Captain America gets into the villain's plane by holding onto the landing gear as it's taking off and waiting for it to be retracted. How realistic is this scene, when applied to modern airplanes?

Could you theoretically gain access to a large, modern airplane by just holding onto the landing gear - assuming, of course, you managed to hold on? Do the landing gears of large modern planes retract into interiors that have access to the rest of the plane, or do those interiors tend to be sealed off? And for that matter, how hard would it be to hold on to a plane's landing gear as it's taking off?


texts: Is it cheaper to drop cargo than to land it?

texts: Is it more fuel efficient to drop cargo onto a runway from the air en route to a final destination than to land and unload it using a more fuel efficient plane?


texts: Does an autopilot that controls roll, pitch and a yaw damper meet the requirements of 135.105(c)(1)?

texts:
For single-pilot VFR operations, 14 CFR 135.105(c)(1) requires that:

  The autopilot is capable of operating the aircraft controls to
  maintain flight and maneuver it about the three axes

Does this mean an autopilot with roll, pitch, and a yaw damper would qualify?


texts: Do FAA endorsements have to use the current language word-for-word?

texts:
When pilots are going through the instruction process they receive many endorsements from flight instructors. It's common for a pilot to possess a logbook that has a prefilled endorsement in the back. It's also common for the logbook to use language that was current at the time it was produced, but for that language to have been superseded.

The FAA publishes and updates AC 61-65. At the current time, we're up to AC 61-65G.

My question is this. Are endorsements valid if they don't use the current language found in AC 61-65?


texts: Do hospitals have radio communications with air ambulances?

texts: Do hospitals have a sort of ATC for incoming medical helicopters? What kind of procedures do helis follow when landing at a hospital to make sure they are cleared to land/takeoff, etc?


texts: Is it possible to get into a spin situation while coordinated?

texts:
Is there any possibility of spinning while coordinated?  Of course, any CFI would tell you no, but I wonder if the the following situation could result in a spin while coordinated:

Slow level flight in a turn
Outside aileron needed to counter over-banking-tendency; rudder as needed to keep coordinated
One wing has a higher AOA due to aileron deflection
Pull back on elevators, stalling one wing first


texts:
I have found out that an ISA atmosphere is:

15 °C temperature
5 °C dewpoint
1013.25 hPa pressure

What are the conditions of an ISA +10, ISA -15 and ISA -30? I know the temperature, but what are pressure and dewpoint?

I need to create those conditions to do some flight testing in a simulator.


texts: Is there a system of automated sharing of current (experienced) weather between aircraft in flight?

texts: For example, if say - Aircraft 1 is flying a certain route, being followed by Aircraft 2 at an interval of say, 5 minutes (over the same position). Is there a system by which Aircraft 1 can transmit the weather it is experiencing at that moment to Aircraft 2? Something like crowd-sourcing weather from all on-board sensors of aircraft in the air? Akin to ADS-B for weather?


texts: What kind of liquid can be seen 'leaking' from the upper surface of the wing of a Boeing 737-800?

texts: Can anyone advise what the liquid seen on the wing of a 737-800 on approach as highlighted on the attached images is? The liquid was seen "pulsating" from the bases marked by the arrows. As the plane came to land, the intensity of the flow decreased until it eventually stopped altogether.


texts: What constitutes "the lights delineating the runway"?

texts:
ICAO defines RVR as "The range over which the pilot of an aircraft on the centerline of a runway can see the runway surface markings or the lights delineating the runway or identifying its centerline."

What are "the lights delineating the runway" here? Do they just point to runway edge lights? Or do they include approach lighting systems as well?


texts: What factors affect the minimum time to go from point A to point B?

texts:
I've created this trajectory for a small RC aircraft to go from 15m to 61m as quickly as possible (e.g. quickest time to get from point A to point B). I'm trying to perform a sanity check for why the aircraft would go to the lowest allowed altitude to maximize velocity before beginning it's climb. Can anyone provide an explanation for why this would be most time-efficient for this problem?
The reason that the aircraft does not fly lower than 5m is because I set 5m as the lowest possible constraint. If that constraint was not in place, it would try to fly at 0m.
Edit:
The reference listed for this type of problem is given as 'J. Betts. SOCS Release 6.5.0, 2007.'. This is an inappropriate place to ask for this, but I have tried searching for whatever this paper/journal this may be referencing and cannot find it. If anyone has any tips/tricks on how to actually find this source, please let me know


texts:
This is confusing to me:

Since pressure increases with temperature (I don't know why), how can air density decrease with temperature. In a hot day then pressure would increase and air density decrease? How is that possible?

@casey @steve V. @StallSpin

The point is this: FAA writtten says:
The altimeter will indicate lower altitude than actually flown in a temp warmer than standard. I understand that this way: this an example

1) Indicated Altitude: 12.000ft
   True Altitude: 12.000ft
   Temperature: -9 Celsius (STD)

Then suddenly the air temperature changes from -9 to +20 (Example) and in a couple of minutes we have:

Indicated Altitude: 12.000ft
   True Altitude: 14.000ft
   (In warmer than stantard, pressure increases so the aneroid waffers in the altimeter will contract indicating lower altitude (lets say it indicated 10.000), then the pilot will climb "back" to 12.000 but in reality (true altitude) he is climbing to 14.000.

Am I getting this right?

2) Now another thing, temperature decreases with altitude, so aneroid waffers are expanded with altitude.

Does the aneroid waffers mesure density or pressure?


texts: How to calculate Vx for a propeller driven airplane?

texts:
I know that Vx for jet engines airplane is at Vmd and that Vy is at 1.32 Vmd;
I do also know that Vy for propeller airplanes is at Vmd.
Now I cannot figure out where i can get the Vx for propellers.


texts: Which regulations require the ARROW documents?

texts:
In the US, a common mnemonic for the documents that must be on board an aircraft is ARROW:

Airworthiness Certificate
Registration Certificate
Radio Station License (international flights only)
Operating Handbook
Weight and Balance

Which regulations state that these documents must be on board?


texts: Why wasn't there a belly gunner on the B-25 Mitchell?

texts: The B-25 Mitchell doesn't have a belly gunner, which would seem quite dangerous. Why didn't it have one?


texts: On SEP airplanes, why does the fuel consumption decreases with temperature, pressure and airspeed being equal?

texts:
Looking at the cruise performance tables in the POH of the C150, C172 or C182, one can see that for the same pressure altitude, the same RPM and the same true airspeed, the fuel consumption is reduced at higher temperature.

For example, a 1976 C150 POH indicates, at 2500 RPM, at 2000 ft pressure altitude,

at -5°C: 97 KTAS, 5.3 GPH
at 15°C: 96 KTAS, 4.9 GPH
at 35°C: 95 KTAS, 4.6 GPH

(yes, there is a 1 kt difference each time, but interpolating the values gives very similar results)

But thermodynamics tells us that the efficiency is proportional to the difference of temperature between the isothermal expansion at Th and the isothermal compression at Tc in the Carnot cycle, thus efficiency = (Th-Tc)/Th.

I cannot reconcile the consumption data with that theory, since apparently the output power is the same (true airspeed, with identical parasitic and induced drag forces) for an apparently higher efficiency at higher Tc temperature.

What other factor am I missing?


texts: Do high-speed ailerons help with the roll rate control in non-FBW?

texts:
Do inboard high-speed ailerons help with the roll control by decreasing the moment arm as a secondary benefit? As in make it harder to exceed the roll limits when at high-speed.

I know the main benefit is to avoid aileron reversal. Also I'm aware discussing tailoring the stick forces in depth will be too broad. So I'm not after an in-depth analysis. Just if that secondary function is indeed a reason.

Comparison of high-speed aileron placement on Airbus and Boeing is shown below. In an Airbus with fly-by-wire (FBW), the stick commands a roll-rate. And all the Airbus FBW heavies—including the A380—do not feature far-inboard ailerons like the Boeings. In other words, if FBW did not exist, could Airbus have still been able to not have mid-wing ailerons?

Airbus (top) source; Boeing (bottom) source.


texts: Why does fuel vaporize in the carburetor?

texts: So I get that a carb vaporizes fuel and mixes it with the air intake for the engine. But my question is what is the explanation for what causes the fuel to vaporize after it exits the fuel nozzle?


texts: What is the autorotative rate of descent for a Bell 47-H?

texts: I would like to estimate the amount of time a pilot would have before a forced landing after suffering engine failure in a Bell 47-H at 1,000ft. This is for purposes of understanding a historical accident. The pilot in question ran out of fuel so the tanks were empty. Many thanks.


texts: What is the name or part number of the Bose 'Lemo' aviation headset connector?

texts:
In a similar direction to this question, I was wondering if anyone knows the name or part number of the connector commonly featured on Bose aviation headsets such as the A20. It is commonly know as the 'Bose connector', 'lemo connector' or the '6-pin connector'.

The A20 manual merely calls it the 6 pin plug (page 13) and gives the connector dimensions (page 35).
The name 'lemo' suggests it's one of the connectors developed by the LEMO company (perhaps something from the B or K series?).


texts: How does a pilot report a person (on the surface) in distress?

texts:
After a downhill bike ride gone wrong last night.  Around midnight I was climbing up a mountain (to my Jeep) with my bike on my back.

While I was climbing I was thinking about the fact my headlight had an SOS function (I didn't consider using it).  SOS functions of lights are great and all, but then I realized that as a pilot, myself, I am not sure how to report a person in distress on the surface.

As a climber and ROTC cadet, I am well versed in the hand signals, and various ways to flag down airplanes, but as a pilot, if I were to come across someone flashing SOS at night, or flagging me down with a mirror in the day, how would I report their location to get a search and rescue team dispatched?


texts: Do any regional turboprop aircraft have leading edge high lift devices?

texts: I'm currently working on an aircraft design project for a regional turboprop. I wanted to know if there are any regional TP's with leading-edge devices. It seems that a lot of them have deicing boots on the leading edge that make high lift devices difficult to install. Also maybe TPs just don't need the additional lift.


texts: What is the difference between RTOP, MTOP, and MCP?

texts: I am currently learning how to fly the SD3-60 (Shorts) Aircraft, and I am trying to gain an understanding of RTOP (reserved take off power), MTOP (max take off power), and MCP (max continuous power).  Can someone explain the difference between all three of these and which phases of flight/situations we would use these in?  Can someone also explain why we would use one over the other in certain conditions?  Thank you so much in advance!


texts: Which FAA or EASA regulation does prevent a high wing to cross the passenger compartment?

texts:
I'm looking for reference subpart and eventually chapter in either FAA or EASA regulation where it is stated that for passenger aircraft with high wing passenger compartment can not be interrupted by fuselage-passing wing, so the wing must be placed above the fuselage (with additional fairing thus increasing drag and weight - eg. ATR-42).

I know this is quite obvious but I need a regulation reference for a report.


texts: How secure is an airplane on the ground whilst passengers are boarding the aircraft?

texts:
On my recent flight to Ibiza, as I and the other passengers were boarding, there were many occasions where I could see right into the cockpit as the pilots and cabin crew were communicating back and forth for whatever pre-flight checks they were conducting. Being near the front of the queue at the gate, I was one of the first seated, the 10-20 minutes it took for the rest of the passengers to board was the time I refer to when I say I was able to see into the cockpit.

With it being my first flight in quite a few years, understandably I was extremely nervous. From the open cockpit to the smell of burning as the engines spooled up...

If we ignore terrorism, what is stopping a drunken passenger from, instead of turning right when they board at the front loading door, turn left and take a few steps into the cockpit, and if they were able to get into the cockpit, assuming they know absolutely nothing about the operation of a plane besides that pushing that pushing the throttles forward = more thrust = plane moves (faster), what damage could they do with a plane parked at a jetway or a plane parked out on the tarmac that requires a shuttle to drop passengers to the plane in order to board it.

If we introduce terrorism into the mix, what is stopping a group of strong men from forcing their way into the open cockpit past 1 or 2 cabin crew?


texts: How do typical ground marshaling signals differ for helicopters?

texts:
There are common hand signals used by ground crew for fixed wing aircraft like 'taxi forward', 'spin up engine #1', 'turn right', or 'stop', for example:

At most airports, general helicopter traffic doesn't need to be marshaled, but I'm sure that pilots must be required to at least know some standard signals, in case of some communication issue that would require the use of hand signals.

Do these signals differ for helicopters, and how so? Do helicopter pilots have a different set of signals they must know?


texts: Can anyone please help me identify this biplane? The photo was taken in Newcastle, NSW, Australia. I can’t seem to find anything.


texts: Is it possible to install a bike rack on a Cessna 172?

texts:
I stumbled upon a nice photo manipulation on aviationhumor.net.

Source

My question is short and concise:

Is it practically possible to do that? Is it okay in terms of aerodynamics, weight, CG?
Bonus Question: If it was possible, would there be any chance it gets certified for use?


texts: Why so much ground time at Frankfurt Airport?

texts:
Disclaimer: Total layman here.

I frequently fly into and out of Frankfurt Airport (FRA) with regional jets (flight time advertised as 45 minutes) and one thing that everyone is always annoyed about is that you spend approximately the same amount of time in transit on the ground in Frankfurt as you spend in the air.

I understand FRA is a huge airport, but what does not make any sense to me is that you...

...have to walk 10 min to the gate
...must spend 10 min on a bus to get you to the aircraft
...then spend at least 10-15 min on the aircraft as it taxis to its start position on the runway

Given that these regional connection flights are always on a tight schedule, I do not quite get why they do it this way.

Specifically, can anyone explain why — in FRA — these small jets are parked so far away from their landing/starting positions when you have to get there by bus anyway?


texts: Who is responsible for airspace separation when an IFR flight is cleared for a visual approach?

texts:
In areas tightly packed with airports (FXE, PHF, and countless others) it is possible to enter the airspace other than that of your destination airport. Some are less than 5 miles apart.

In particular,  say you are on an IFR flight plan and cleared for a "visual approach" to your destination.  While proceeding with the visual approach and descending, you could enter the class D airspace of a nearby airport.

You are in communication with the destination tower but not the tower of the other airspace you have just entered.

Is it the pilots responsibility to avoid the surrounding airspace or the tower controllers responsibility to coordinate with the other towner when IFR and conducting a Visual approach as referenced in AIM 5-4-23.


texts: Is setting elevator to certain angle equal to trimming the horizontal stabilizer?

texts:
(I was trying to understand the longitudinal stability of aircraft and how it is related to elevator)

If I pull the stick back by, say 2 inches, will it have the same affect as trimming the horizontal stabilizer to make the aircraft fly at that angle of attack?

I mean, does setting the elevator at constant 2 degree will make the aircraft swing its nose up as long as the stick is held or does it trim itself to the new angle of attack and ride steadily in its new position?


texts: How many significant digits should I use for simulating aircraft equations of motion?

texts:
I have coded the equations of motion in Matlab, and I am using the ode45 function to simulate the nonlinear dynamics of F/A-18 Hornet without any controller (just the airframe). I have given initial conditions as trim conditions.

d2r = pi/180;           % degree to rad

V       =  438.653328;  % Airspeed , ft/s
beta    =  0*d2r;       % Sideslip Angle, rad
alpha   =  10*d2r;      % Angle-of-attack, rad

p       =  0*d2r;       % Roll rate, rad/s
q       =  0*d2r;       % Pitch rate, rad/s
r       =  0*d2r;       % Yaw rate, rad/s

phi     =  0*d2r;       % Roll Angle, rad
theta   =  10*d2r;      % Pitch Angle, rad
psi     =  0*d2r;       % Yaw Angle, rad

pN = 0;                 % X position in Earth Frame, ft
pE = 0;                 % Y position in Earth Frame, ft
h = -25000;             % Z position in Earth Frame, ft

During the first iteration, C_m has a very positive small value (1e-10), which leads to some pitching moment when multiplied by S, c, and qbar (even though it's small). But, as time keeps on increasing, this value of C_m goes on increasing and as a result, a large moment is created. Due to the high precision of Matlab, the pitching moment coefficient is not for the given trim condition.

My question is: should I round off the values of C_m to 3 or 4 digits? By rounding off, the C_m will be zero and I get M as zero.

The below figure shows how velocity is varying with time when the aforementioned initial conditions are given.

This figure is obtained after rounding off C_m to 4 significant digits.

This figure is obtained without rounding off C_m to 4 significant digits.

Alpha and theta values without rounding off C_m.


texts: When the winds aloft are light and variable, what wind direction and speed should I use for flight planning?

texts: What do you input in a navlog for wind direction and velocity, when the wind and temp forecast says 9900+18? I know 9900 means light and variable winds less than 5kts but how do I determine the average wind direction to use for my navlog?


texts: Where can the FAA versus ICAO official filed differences be found?

texts:
ICAO has a process where individual countries may file differences from the ICAO standard when the rules of the country do not coincide with the published standards.

Where can the list of differences that the FAA has filed be found?  I have found references saying that it is in the AIP, but I could not find a list in that document.

For instance, there is an ICAO requirement that certain aircraft are covered by a Flight Data Monitoring (FDM) program, but FAA rules say that it is an optional program and not required by 14 CFR.

I found one (expired) document, paragraph 4b which refers to the FAA filing a difference with ICAO and want to see a complete list of all current differences.


texts: Are turns, while under the control of a two-axis autopilot, uncoordinated?

texts: Since the two axes of a two-axis autopilot are pitch and roll, when the autopilot executes a turn, is it uncoordinated since the autopilot is not controlling the rudder (yaw)?


texts: What do these explanations for propellor RPM increases mean?

texts:
I have read in a book that if the engine RPM increases while descending, the probable causes are:

Engine transfer bearing leaking excessively
Excessive friction in blade bearings

I am not able to understand these reasons.

Can someone explain "engine transfer bearing" and what these two reasons mean?


texts: Why are many early gliders high-wing designs as opposed to newer designs?

texts:
Many early gliders were designed with a high-wing configuration. An example of this is the K 8, but many more of the same and previous generations follow this configuration.

Later generations (e.g., ASK 21) mostly follow a mid-wing design.

Is there a simple reason for this (including the change of material for fuselage and wings)?


texts: As I understood, when the relative airflow meets the wing it changes, and the resulting flow is called effective airflow?


texts: What first aid equipment is on a commercial aircraft?

texts: I have always wondered what type of first aid equipment is on a commercial aircraft with an airline such as Thomas Cook or Ryanair. Do they have things to save your life etc.??


texts: Why don't large commercial airplanes have electric motors in the wheels?

texts:
The cost of jet fuel during taxiing can be a pain. Concorde in particular had very large fuel expenditure for taxiing.

So why not put electric motors in at least 2 wheels to drive the plane that way? They would not have to be the most powerful motors in the world---only strong enough to get the plane up to a few miles per hour, or normal taxi speed.

EDIT: I don't think this is a duplicate of this other question. If anything, the savings cited in the answer of that question seems to imply that my question, asking why it isn't implemented, is actually a pretty good question.


texts: How long can ATC operate for without main power?

texts: This question pertains to large towers at large airports. I'm assuming there is backup power in case of a power cut / power failure. But how long does a typical reserve generator / unit supply power for and what happens if it runs out without a main supply back online?


texts: Do "water bomber" aircraft pilots have more relaxed rules?

texts:
I have no exposure to aviation regulations, but I'm curious if some rules are different for emergency aircraft pilots.  Similar to ambulance drivers and police officers being allowed to speed or run red lights for the sake of emergencies.

Specifically, this video shows a water bomber very close the ground and bystanders during an approach:

My gut tells me two things:

A) that this plane is dangerously close to the ground, and

B) that this would be a serious incident, representing some sort of strike against the pilot's record.

Please correct me if I'm wrong about either point.  If either are true, though, is the situation treated differently for emergency pilots?  Are they trained to go that close to the ground, like police officers are trained to handle a car at higher speeds?  And are their rules different for that reason?

I'm not sure how much the answer would vary country to country, aircraft to aircraft, or even situation to situation.  So if the question is too broad, assume the United States or Canada even though that's not where the video is from, and assume a water bomber pilot in a situation just like this.


texts: How does the idle speed adjustment in a Stromberg NA-R9B float-type carburetor work?

texts: What is the purpose of the idle speed adjustment in a Stromberg NA-R9B float-type carburetor? In what situation do we adjust the idle speed?


texts: How do they quickly replace the pylons after a hit during the Red Bull Air Races?

texts:
My 3 years old was watching the movie Planes (Dusty Crop hopper one) and when he saw one airplane hit a pylon and puncture it he asked: How will they fix it?

I told him it was air filled and they will put a new one there but his question got me wondering as to how can they be replaced quickly before the next guy's run? Is it just like pop one off and put a new one there and quickly blow air with heavy output pumps?


texts: What if you refuse to fasten your seatbelt?

texts:
As a passenger, what happens / can happen if you refuse to fasten your seatbelt when you are told to, either during take off/landing or (bad) turbulences?

I've recently read a Facebook post that supposedly described such a situation. It didn't give many details, so that's why I'm here.


texts: What is the difference between rate of climb and climb gradient?

texts:
I am currently trying to study aircraft performance and I have some difficulties distinguishing between rate of climb and climb gradient.

Can someone explain what are the differences between the two of them?


texts: What are the major causes of flameout, excluding ingestion of foreign objects?

texts:
What are the most frequent causes of flameout, excluding ingestion of foreign objects and other sudden forms of damage to the engine?

I'm limiting this to modern turbojet and turbofan engines with a computerized (digital), closed loop engine management system.

E.g. what could cause a F119-PW-100 engine to flameout or otherwise fail?

I'm not looking for a thorough study or carefully detailed statistics, I doubt something like that even exists. I'm basically asking if this ever happens, or if this is basically a thing of the past with early fighters, such as the Me 262. Are modern jet engines "bulletproof"?

If it does happen, then how?


texts: What exactly happened in this bird strike incident?

texts:
This Boeing 737 was hit by a bird and continued all the way to its final destination, from Prague to Las Palmas.

What actually happened here? Was the incident considered a bird strike or an engine stall? Can an aircraft continue to its final destination after a bird strike?


texts: What effect does cold weather have on helicopter performance?

texts:
Recently I was flying around my RC helicopter on a 40 $^\circ$F (4$^\circ$C).

At some point in the flight the rotor just stopped moving in mid-air and then I regained control back at ground level. I never had any issues before in warmer weather, so I assume it's a cold-weather related issue with this model.

This leaves me with two questions:

Could something like this  happen in a full-size helicopter like a Robinson R22?
What effect does temperature have on helicopter performance in general?


texts: What is the authority of the Air Boss at an airshow?

texts:
Regular ATC operates under regulations like FAA Order 7110.65 when they control traffic. At an air show, there is typically an "air boss" that manages aircraft within the air show area.

Is the air boss required to have the same training and certification as a regular controller?

Does the air boss operate under the same regulations as regular controllers?

Does the air boss have the same authority as regular controllers?


texts: Can someone explain this glideslope question?

texts:
The glideslope deviation bar is covering the second upper dot. The required action to meet glideslope beam is to:

What does this question mean?


texts: Why are inlet vanes used instead of variable geometry inlets to prevent compressor surge/stall?

texts:
Jet engine core axial compressors (that of subsonic turbofans anyway) are designed to keep air flowing the right way at max RPM(or close to it). Below that, the airflow slows more and more, and becomes unstable.
In other words, the compressor can no longer compress the large air volume flowing into it. To prevent this, variable inlet vanes are used to reduce the airflow volume into the compressor at low RPM.

My question is: why was this method chosen? When you're running the engine at low power/RPM, the closed vanes will create drag by presenting their blunt face to the air. So why not use a streamlined variable geometry inlet which can forespill the excess air with less drag? such as the following:

TOP: low RPM, a sliding annular door narrows the annular gap

BOTTOM: high RPM, the door slides back, widening the annular gap


texts: What caused the loss of "everything" on Swiftair Flight QY-2939?

texts:
I found this from a youtube video, and more info from this avherald article.

One of the pilots declares an emergency because right after takeoff they lost "everything", as in all instruments. ATC managed to steer them back to a safe landing.

This was 2016 Nov 17, in Ireland, on a Boeing 737-400. What on Earth could cause the loss of all instruments? From what I gathered online, the plane was not struck by lightning or going through bad weather.


texts: Does downwash increase or reduce lift generation?

texts: I’m wondering about the impact of downwash on lift generation. I've read that, because downwash creates lift according to Newton's third law of motion, increases in downwash due to greater AoA (especially when augmented by devices such as slots and slotted flaps, which use various aerodynamic effects to increase the amount of downwash generated) result in increased lift. But I've also read that ground effect increases lift by decreasing downwash, so I'm confused how this works. Can someone clarify the effect of downwash on the amount of lift generated and tell me whether I've got it right or not? Thanks!


texts: What is the future of manufacturer independent jet engine maintenance repair and overhaul (MRO) services?

texts:
I have noticed that Air France KLM offer a Maintenence (MRO) service for aircraft and jet engines. This sounds like a potentially big threat to engine manufacturers like Rolls Royce who makes around 50% of its revenue from its TotalCare MRO servicing contracts.

I would have thought the price of buying saying a Rolls Royce jet engine would be far higher if an airline customer did not take the MRO TotalCare package from RR and in addition the airline may suffer from reduced engine warranties if they employ a 3rd party to service the engines.

Do you think engine manufacturers business will get competed away by independent MRO businesses like Air France KLM's?


texts: What are the most number of propellors that a rotorcraft has been flown with?

texts:
If you had 1000 small propellors you could accelerate upwards many times faster than with 4 large propellors.

What are the rotorcraft experiments with the most number of propellors ever?


texts: Why do the jet turbines spin while the engines are turned off? Is this as a result of the wind? Or are the turbines deliberately spun using the APU? If so what is the reason behind this?


texts: Where do websites like expertflyer.com get their information?

texts: I've been looking at internet resources like expertflyer.com and KVSTool which query information like live seat maps, upgrade availability and fare bucket information. To my knowledge, this seemed like proprietary information unique to each individual airline. Is there a public API or database that these pieces of software are using or do they simply scrape the websites of each individual airline? Perhaps this might be a question better suited for Programming SE but I thought I'd start here.


texts: What is the relation between number of crew members (pilots and attendants) and fleet size in airlines?

texts:
Taking into account relevant elements like the fleet size or the type of flights (short or long haul, passengers or cargo, ...), do airlines use typical ratios between the number of aircraft and the number of pilots and attendants?

Clarification for the type of elements I'm looking for:

Northwings has 120 passenger aircraft and 720 pilots, this is comparable to other US airlines with modern aircraft (6 per passenger aircraft).
There are between 4 and 10 Captains per passenger aircraft. This is dependent on local labor laws and unions.
4 to 6 F/O for cargo aircraft (and no attendants because no passengers).
A380 are atypical at Thing Air with 700 flight attendants for 10 aircraft of that type.
Count 25% less for low cost airlines in the Middle East due to less restrictive labor laws and extended working time.

(Figures are for illustration, I've no idea of what the actual values are.)


texts: Do planes turn while climbing? Is this because of air characteristics variation?

texts:
I've developed the impression that often commercial planes will bank and turn as they climb across thin cloud layers that appears to be stratus or stratocumulus.

I think these clouds indicate a separation between different air masses. So my question is two-fold:

Are planes actually doing this or is it a coincidence?
If not a coincidence, what is the reason? and what would happen if they didn't?


texts: How is the visibility at airports measured?

texts:
What tools are being used by airports to measure visibility precisely?

Do we have some kind of tools on aircraft as well for measuring visibility?


texts: What does the * (asterisk) next to radio and nav aid frequencies on Jeppesen charts refer to?

texts:
For Bournemouth, all radio frequencies and LOC IBMH are marked with an asterisk - *

Many other airports also have these markings, such as: Southampton, Alderney, Jersey, Guernsey, Exeter...
However, Cardiff doesn’t have an asterisk preceding to its radio frequencies:

But it does have one before LOC ICWA
What does an asterisk, preceding a frequency, refer to?


texts: Is there an efficiency measure for airports?

texts: For large, busy airports (such as JFK), how do they measure how well they are being utilized? I assume airport management wants to serve as many flights as possible, for maximum revenue. Any time their gates are empty, or runways aren't being utilized, the airport has more capacity to sell. Is there some sort of industry standard measurement for "airport utilization efficiency"?


texts: Can a harbor freight predator 212 cc engine be enough for an ultralight

texts:
Hi I am planing on building a budget ultralight and I was wondering if a 6.5 hp 212 cc predator motor will be enough and if so what size prop should I use.

A little background, it is going to be a wood and foam plane with fiberglass covering I am going to have a few bits and pieces of aluminum for strength. I don’t have a plan yet because I am going to plan it around the engine. I am shooting for 160 pounds dry. Thank you in advance.


texts: In case of engine failure, do the fighter jets have such a stable airframe so that they can glide their way through to the nearest landing strip (As it happened in the case of Gimli glider)?


texts: Does the auto thrust at takeoff compensate for asymmetric engine characteristics?

texts:
When a percentage thrust has been determined for take off the auto thrust system (Airbus) or the auto throttle (Boeing) will send the data to the engines FADECs to provide the required thrust.

When the levers are set at FLEX (Airbus) or when the levers push button is pressed (Boeing) the engines will develop the takeoff thrust which is displayed as an N1 or as an EPR.

It seems the FADECs will command the same N1 (EPR) for all engines since the displayed N1 (EPR) are the same for both (all) engines. Am I right?

Considering the engines may have different age and therefore producing different thrusts for the same indicated N1 (EPR), a thrust assymetry will result. Is it true? How this is acceptable at take off?

Considering the engines total running hours (aging of the engine) are known by the operator, is there a way  to enter such a data to the auto thrust or to the auto throttle or to the FMS in order to get at take off really equal thrusts and not just equal N1(EPR)?


texts: Why do the B747 of NASA Shuttle Carrier Aircrafts (SCAs) need additional vertical stabilizer?

texts: Here is picture of B747 SCA of NASA and the AN-225 SCA. There are additional vertical stabilizer in the tip of the elevator to the Boeing's, while the AN-225 is designed with the vertical stabilizer located at the tip of the elevator. As we know, AN-225 was also designed and intended to carry Soviet's Aircraft. Then my question, why do the B747 of NASA Shuttle Carrier Aircrafts (SCAs) need additional vertical stabilizer?


texts: How do I know when to use flaps in glide approach or force landing?

texts: During glide approach or practice force landing, I can see the aim point moving down. It means the aircraft will overshoot the field. But I am not sure when should flaps be used or which stage of flaps should be used. I concern that deploying flaps too early, the aircraft will not make it to the field.


texts: What are the two turning tendencies that occur during a steep turn?

texts:
A question has come up in preparation for a Block exam. what are the two turning tendencies that occur during steep turn? If you know this may you please explain to me, why these tendencies occur.
Cheers !


texts: What is this aircraft (Le Bourget airshow 1965)

texts:
Approximately 31 seconds into this video of a walkaround of the 1965 Paris airshow, there's a curious aircraft shown next to a Navy F-4.

The question is - what is it?


texts: Why was Pan Am Flight 103 flying over Lockerbie?

texts:
Pan Am Flight 103 was a flight from Frankfurt to Detroit with stops in London and New York.

Why after taking off in London did it fly all the way to Lockerbie instead of going directly to New York? Take a look at these pictures.


texts: How is an aircraft with a stabilator trimmed?

texts: Many supersonic fighters have a stabilator to control pitch. My question arises when I cannot see any trim-tab on the stabilisator (e.g. on the F-16 or on the F-22). Other means to trim an aircraft without trim-tab and without using the stabiliser as a trim must exist. What are those means?


texts: Can you re-register a de-registered aircraft with the same N-number?

texts: If I'm selling a plane that has been de-registered, can the new owner re-register the aircraft with the same number (or do they have to get a new one)? Does the airworthiness certificate transfer as well? How long does this process typically take?


texts: Which speed shall be used on high speed taxiway?

texts: After landing, which speed shall we use to exit from high speed taxiway? Max. 60 knots ground speed or indicated air speed?


texts: Is English sufficient for international aviation?

texts: Is it possible to fly internationally understanding only English for radio communications? Are there exceptions?


texts: Are the window wipers on jet aircraft ever deployed in flight?

texts:
Many commercial airliners have car-like window-wipers. I would presume this is for taxiing only, as the wind would surely keep the windows free from water when airborne,  or do they turn them on in flight?

Also, don't these wipers cause a lot of drag, and wouldn't it be more economical to have some kind of air-jet blowing from nozzles to keep the windshield clear?


texts: What happens to the transponder, FDR and CVR in case of an explosion?

texts: Will the above mentioned equipment still work and transmit data/location information if an explosion occurs inside the aircraft?


texts: Why is a sweeping second hand required for IFR?

texts:
The reasons why a clock is necessary for IFR have been explained elsewhere, but I haven't seen the reason that the clock has to have a sweeping second hand.

It seems like when timing things it would be more useful to have a ticking second hand, why is it expressly required that it be a sweep?


texts: Wikipedia lists N8 at the IATA code for National Cargo Airlines (ICAO NCR), a regional airline based in Orlando, Florida. AirlineCodes.info and other sources list N8 as the code for Fika Salaama (ICAO HGK), which is based in Uganda. Both are currently in operation. What on earth is going on here?


texts: Flight plan departure procedures vs real life departure procedures

texts:
In the flight plans there are included departure procedures. However, sometimes something can change eg. different runway is assigned by ATC and then departure procedures in the flight plan is invalid, because SIDs are assigned to the runways.

Are flight plan amendments send after such change?
Does it happen often?
How airline dispatcher knows which departure procedure to fill in the flight plan if he doesn't know which runway will be used in the future or what will be the wind direction etc.


texts: What is that building in Suvarnabhumi Airport?

texts: In Suvarnabhumi Airport (Bangkok) there is a building in aerodrome, next to the main terminal (Circle by red colour) . What is that?


texts: How does altimeter reading vary when departing from ISA conditions?

texts:
I am a soon-to-be student-pilot and am struggling with a basic concept that is altitude. After watching multitude of online videos, I feel that most of the people do not have good teaching skills.

Introduction

The altimeter is a barometer, it reads atmospheric pressure. At 0' altitude, it should measure "this certain pressure that we find at 0'" and indicate 0'. This is obtained by setting the reference pressure in the Kollsman window measured somewhere near the airport. One day it might be 1013 hPa, others it will be 998 hPa or 1036 hPa.

The Scenarios

We are in the aeroplane, at the airport which is at MSL (0' altitude).

SCENARIO 1 (International Standard Atmosphere):

Elevation: 0', temperature: 15 C, pressure: 1013.25 hPa
METAR reads QNH 1013

we set our Kollsman window to 1013 => it correctly indicates 0' altitude
we set it to less than 1013 => it will indicate more than 0' (say 230') LESS than 0'!
we set it to more than 1013 => it will indicate less than 0' (impossible but bear with me) MORE than 0'

SCENARIO 2 (low pressure):

Elevation: 0', temperature: 15 C, pressure: 998 hPa
METAR reads  QNH 998

set our Kollsman window to 998 => it correctly indicates 0' altitude
set it to less than 998 => it will indicate more than 0' (say 230')
set it to more than 998 => it will indicate less than 0'

If I got the above correctly than the following should apply too:

SCENARIO 3 (International Standard Atmosphere):

Elevation: 5000', temperature: 5 C  (as per lapse rate, -2C for every 1000'), pressure: 847 hPa (as per lapse rate, -1hPa every 30')
METAR reads  QNH 1013 (actually our pressure of 847 hPa, adjusted down to MSL)

set our Kollsman window to 1013 => it correctly indicates 5000' altitude
set it to less than 1013 => it will indicate more than 5000' (say 6200')
set it to more than 1013 => it will indicate less than 5000'

My Questions

What happens at this altitude of 5000' if we move out of the ISA?

if the temperature drops further to, say -2 C?
if the pressure goes up to 900 hPa?

EDIT (answer):

My premise of "...we set it to less than 1013 => it will indicate more than 0' (say 230')" was wrong all the time! By setting the pressure in the Kollsman window we are effectively "telling" the altimeter at which pressure the 0' elevation is (or what is the pressure at 0' elevation).

If we "tell it" that the 0' is at 1000 hPa, and it is still sensing 1013 hPa as I initially stated, it will indicate only possible altitude - LESS than 0', not more.


texts: Can you please explain aircraft spin in simple non-mathematical terms?


texts: Are there pilot weight limits for the Rutan Vari Eze?

texts:
In this question on the Rutan Vari Eze it is said one of the reasons it parks nose down (gear up) is to bring the Cg forward for stability (so it doesn't tip over) when there is no pilot in the aircraft.

If the pilots weight is that important to move the Cg to a safe position, is there a minimum/maximum weight the pilot must be to bring the Cg to be within acceptable limits?


texts: How do I calculate the wind angle relative to the aircraft's heading?

texts:
If I want to calculate the wind angle relative to the aicraft's heading, I use TAS and not IAS, right?
I want to calculate the relative wind angle to the aircraft. I have this information to work with: GS, IAS, TAS, Heading and GPS direction. I wonder if I can just calculate the ground vector (ground speed and direction) minus air vector (TAS and heading)?


texts: Is there a standard format to exchange airspace information in electronic form?

texts:
I am looking for information about airspace definitions.

On maps they look great and a pilot has no problem reading maps and NOTAMs, but what about autopilots? Do they use some kind of standardized interface/database? If it exists, where is it defined?

I am not specifying a country because hopefully there only one standard (or an extremely limited set). Should this not be true, I would like to focus on Europe and North America.


texts: Aeroplane protection against lightning strikes

texts: I would like to know what kind of protection are available on planes against lightning strikes.


texts: Did the contemporaries of the F-14 also have automatic swing wings?

texts:
The F-14's Central Air Data Computer was a innovative design, using microprocessors for its implementation. This computer was used to control the swing wings of the F-14.

How did the contemporary aircraft to the F-14 achieve the same functionality? There were many variable-sweep wing aircraft constructed in the 60's and 70's such as the Mig-23 and the Su-17.

References:

https://en.wikipedia.org/wiki/Central_Air_Data_Computer
http://firstmicroprocessor.com/documents/ap1-26-97.pdf


texts: What are these panels underneath the wing root of a A380?

texts: What are these open panels underneath the wing root of a A380 (right above the person standing under the aircraft)? Are they ram air exhausts of the air conditioning packs?


texts: What is the strongest jetstream ever encountered in commercial flight?

texts:
Jet-streams are high-altitude winds which flow from west to east. They can be provide a very strong tailwind or headwind depending on which direction the aircraft is going.

What is the historic record of the strongest jet-stream ever countered by commercial aircraft? I'd expect the result to be either a very short east-going flight (much shorter than the expected time of travel), or a very long west-going flight.


texts: Why is the critical AoA of most flaps 40° when most airfoils stall at 15°?

texts:
A plain flap deflected 40 degrees is largely stalled (...)

Flaps stall at 40° according to an answer on Quora, why is this so when typical airfoils stall at 15°?


texts: Why some planes are scrapped way sooner than others?

texts:
I am browsing the planespotters.net database, and I see plenty of planes in their twenties. Delta, for example, has 117 MD-88 with an average age of 25 years.

While other planes are scrapped with no apparent reason when they are not even 10 years old: when Malev went bust, all its B736s were scrapped, 6 planes that were around 8 years old. https://www.planespotters.net/production-list/search?fleet=Malev-Hungarian-Airlines&manufacturer=Boeing&subtype=737-600&fleetStatus=historic

This is not the only example, there are plenty of aircrafts not older than 15 years that are scrapped, while other planes are still flying in the late twenties.

What are the reasons?


texts: Can an aircraft owner legally replace an oil quick drain valve?

texts:
The quick drain valve on our older Mooney has started leaking and making a bit of a mess.  We went to our local shop to asked them to schedule to replace it for us and they told us they are booked out several weeks and turning away any smaller jobs due to being understaffed -_-

I mentioned we do our own oil changes and he suggested that if we were handy enough to handle an oil change we could just remove the quick drain and replace it with an original plug and he was happy to give us one for free.  That would get us to our next oil change and we could get it replaced then.

Part 43 allows owners to do the oil changes and replacing the quick drain valve with a plug looks to be basically identical to the oil change process if you didn't have a quick drain valve in the first place: remove the plug, catch the oil, replace plug, add new oil.  But if I'm going to down that route anyway why not just grab a new quick drain off of aircraft spruce and put that in instead of the plug?

Are we on the right side of owner maintenance if we replace the quick drain with a plug as the A&P suggested?  How about if we replace the quick drain with a new one?  Or should we get a sign off from an A&P


texts: Can I get a 20/40 requirement waiver after cataract lens replacement?

texts:
I have had lens replacement surgery and now one eye is focused at 16” (close, reading distance)and the other eye is focused at a distance. I have 20/20 vision both at 16” and at distance as long as both eyes are open.

I have a third class private Pilots license and my medical is due. Can I get a waiver because I don’t meet the 20/40 requirement with either eye closed?

For example when my left eye is closed I can not meet the 20/40 requirement with my right eye when it comes to the 16” test and the same goes for my other eye when it comes to the distance test.


texts: What's the difference between racetrack and holding pattern?

texts: Is there any difference between them or they are only synonymous?


texts: Given aircraft and runway characteristics, how do you compute the maximum temperature for take-off?

texts: Consider an airport e.g. Phoenix Sky Harbor International Airport (PHX), with Maximum runway length (ft) of 11500 and Elevation (ft) of 1135. For Boeing 737 whose Maximum takeoff weight is 174,200 lbs, How do you compute the maximum/optimum temperature for takeoff


texts: What does the instruction "Climb heading [BEARING] to [NAVAID] 2.5 DME" mean?

texts:
I am examining FAA's Standard Instrument Departure Procedures (SIDs) and while reading their textual description, I came across this instruction from
LGA's La Guardia Five Departure SID, for Runway 13 (Whitestone climb): "Climb right turn heading 180 degrees to LGA 2.5 DME then left turn heading 040 degrees etc."

Could someone explain to me what the phrase "heading to LGA 2.5 DME" means? Does it mean that the pilot maintains this magnetic bearing (180 degrees) until the distance between the aircraft and the LGA (NavAid) becomes 2.5 nautical miles?


texts: Why are Krueger flaps called flaps and not slats?

texts:
I always thought that flaps are trailing edge high lift devices and slats are leading edge high lift devices. This is also confirmed by the accepted answer for What is the difference between flaps and slats?.

Inspired by this question, I learned that Krueger flaps are actually leading edge devices, despite being named flaps. The definition on SKYbrary is:

  Krueger flaps are high lift devices that are fitted to all or part of the leading edge of the wings of some aircraft types. The aerodynamic effect of Krueger flaps is similar to that of slats; however, they are deployed differently. Krueger flaps are mounted on the bottom surface of the wing and are hinged at their leading edges. Actuators extend the flap down and forwards from the under surface of the wing thus increasing the wing camber which, in turn, increases lift.

(image sources: Wikimedia and SKYbrary)

I understand that the deployment mechanism is different, but the Krueger flaps are still deployed differently than other (trailing edge) flaps:

(image source: SKYbrary)

So why are they called flaps and not Krueger slats instead?


texts: When evacuating after a rejected takeoff, what is the minimum distance you should be from the plane and which direction should you run?

texts:
In case of a rejected takeoff, and due to a malfunction or engine explosion, how far do you have to distance yourself from the plane and in which direction would you run towards?

In my opinion (please correct me if im wrong) this is what i think, for direction, the most logical sense would be upwind incase of engine fire. for distance, during our training we were told 1 wing span...?

Please include some official references like FCOM, FCTM or other similar documents!

Thank you for taking the time to read my question too!


texts: How frequent is the use of spoilers during descent?

texts:
Having flown a number of flights as a passenger recently, I observed that:

Roughly 50% of pilots used spoilers above FL180
Almost everybody used spoilers to pass the 10,000 feet / 250 knots mark
Roughly 25%~33% of pilots used spoilers around 7,000 feet ~ 8,000 feet down to glideslope capture

Are modern airliners so "slippery" that an engine-idle descent is not enough to meet operational requirements? (on the other hand, makes them really good gliders in the event of a total engine failure!)

I was told that companies like to use engine-idle descent as much as possible because it is the most fuel-efficient way to get down; spoilers are only "sometimes" used when ATC clears the descent path unexpectedly, which usually means a short-cut and passengers can expect an earlier arrival. That was in the 90s'.

Has it changed in the last decade? How frequent is the use of spoilers during the descent portion in today's flights?


texts: Where can a 300lb person get a spin endorsement in Miami?

texts: I'm in Miami Working on my CFI, I'm at the level of trying to get my spin endorsement. The problem is I'm 6'2" and 300lb, so I need your help.


texts: What is the aerodynamic motivation behind vortex generators?

texts:
An airplane's wing creates lift efficiently when the airflow is parallel to the chord of the wing. Vortex generators twist the airstream on the wing surface.

Doesn't this kind of twisted airflow cause lift inefficiency?


texts: Where can I listen online to live VOLMET broadcasts?

texts: Are there sites that stream live VOLMET broadcasts? I need to listen to the format but haven't have the time to put together an amateur radio.


texts: How does the University of Bristol's AI fixed-wing perched landing change the wings?

texts:
The BBC radio program Click's 2017-01-24 episode, starting at about 06:20, describes the use of AI to develop a perched landing capability by an autonomous fixed-wing craft. I can't understand exactly what is happening.

While the BBC's Gareth Mitchel suggests the winds "sweep up", BMT Defence Service's Antony Waldock says that they move or rotate forward, and goes on to say, roughly transcribed:

  ...as you are about to stall you rapidly pitch-up the aircraft, and that pitch-up gives you a little bit of extra lift, and that stops you (from) kind-of mushing into the ground, so you can 'pick it up', and land with minimal velocity at a particular location.

BBC's Bill Thompson then describes the technique as a change the wing shape allowing a controlled stall to lose velocity really quickly and manage the descent.

I'd like to understand if the wings "sweep up" or do they move forward, and is this movement considered a change in the wing's shape? Or are they otherwise changing shape?


texts: Is it safe to use a propeller plane to fly commercially over the Tibetan Plateau?

texts:
I saw this youtube video today: Flying over Mt Everest. A lovely view of stunning nature - quite spectacular. However, I looked up the plane - or at least what I think is the plane - and found that it might be a propeller plane: 9N-AHV (I saw this registration number in the video).
The plane appears to be a BAe Jetstream 41 - check that link for details - it is Wikipedia.
Of particular interest (maybe):

Service ceiling: 26,000 ft (7,900 m)
Service ceiling on one engine: 15,000 ft (4,572 m)

Tibetan Plateau: "...average elevation exceeding 4,500 metres (14,800 ft)".
So it sounds like an engine failure for this plane type means that it  can not descend to the acceptable service ceiling? The service ceiling is the maximum usable altitude of an aircraft.
This seems unsafe?
I am not a pilot, but I hear it is rare to fly over Himalaya / Mount Everest / Tibet because planes can't go low enough for passengers to breathe without oxygen if there is an emergency? If they lose an engine they have to descend I read. There is also a lot of turbulence. Why Planes Don't Fly Over Himalayas.
Airports: Lhasa and Kathmandu - short runways - not many places for emergency landings due to medical emergencies and such. And they wrote "the place is desolate with little people around". That sounds a bit funny seeing as the area is situated between China and India :-). Remote it is though. And China has 94% of its population in the eastern part of the country (towards the sea).
Links:

https://www.quora.com/Why-don%E2%80%99t-planes-fly-over-Tibet/answer/Paul-Oroborust

Maximum altitude limit where propellers can propel?

How high can propeller airplanes fly?


texts: What is the constant in this formula for additional lift?

texts:
Let’s consider the case of a plane flying s/l in a headwind with a positive gradient. A wing produces lift by inducing a bound vortex superimposed on the relative wind., and in the particular case of flying in a positive gradient, one can imagine an extra pseudo-vortex associated with the gradient itself, that re-inforces the bound vortex producing additional lift.

The question is now how to quantify that additional lift. From the variables that enter in the circulation theory of lift, one can guess that the variables involved are the density of the air rho, the airspeed v, the wing area A, the chord c and of course the wind gradient ß.

From dimensional analysis, it results that the extra lift L is:

L = k · rho · v · A · c · ß

where k is a constant to be determined. It can be probably done with a ‘material experiment’, but my question here is whether it can be derived from already known data or from a ‘mental experiment’.


texts: How does an airline decide on an engine?

texts:
How does an airline, when buying aircrafts, decide on which engine to use? In many cases, although there are several options to choose from, the engines do not differ much in their operating parameters.

As an example I would take the Boeing 757-200. This aircraft was able to be equipped with Rolls-Royce RB211 and Pratt&Whitney PW2000. Both engines have very similiar performance ratings and also do not differ much in their physical parameters (e.g. diameter, weight).

From this perspective, it seems to me, that engine decisions are mostly driven by business consideration (e.g. sales discounts, maintenance contracts...)?


texts: Is there a minimal legal ground clearance to use an international airport?

texts:
The question arises while I was looking at the evolution of the B737 engines and the lower and lower space available between ground and engines. Then I realized that ground clearance is also low for other small airliners we can find in international airport (e.g. Embraer 175, ATR-42,...).

I imagine ground clearance is designed taking into account tailstrike, FOD, runway irregularities.

My question is: can an aircraft legally be excluded from using an airport because of its ground clearance?

Let's restrict this question to international airports and airliners transporting at least 8 passengers


texts: Can an airport fine an aircraft for being too noisy?

texts:
I stumbled upon this article (sorry, in French!) stating that in order to avoid fines, Ryanair pilots start take-off procedures at the beginning of the runway (rather than at the "intersection"), with extra engine power (24klb instead of 22klb in Brussels airport) -> this allows pilots to take tighter turns and avoid the noise-sensitive Brussels region.

I know that most (if not all?) major airports have noise monitoring terminals (NMT) in their vicinity which constantly measure the noise as it is perceived on the ground.

From the article, it seems like a single aircraft can be fined for being too "noisy" (i.e. noise generated at monitor above a certain limit). If such is the case:

What is the noise fining policy around an airport / Are there internationally agreed rules on noise limits around airports?
Is it common practice (is it even possible) to "single out" an aircraft and fine the pilot/company for generating too much noise on ground?


texts: What is the difference between variable and transient bleed valves?

texts: What is the difference between variable bleed valves (VBVs) and transient bleed valves (TBVs)? What is their range of operations? Can they be used at all airspeeds?


texts: How do airports in hot climates handle extremely high temperatures?

texts:
In June 2017 dozens of flights were cancelled in Phoenix, Arizona because of temperatures exceeding 120 degrees Fahrenheit/48.9 degrees Celsius.1,2

Hot air at a given air pressure is less dense, generating less lift at a given speed. At least some commercial jets were not rated to fly in air that thin.

While the temperatures that summer were fairly extreme Phoenix is surely not the hottest place one earth, or at least not alone in this range. For example Kuwait City or the Iranian city of Ahvaz3 come to mind.

How do other hot places handle extreme heat? Do they also suspend operation or do they impose specific requirements like lower maximum loads, or do they have special adaptations for the thinner air like long runways, allowing higher speeds at take-off and landing?

1 https://airlinegeeks.com/2017/06/22/multiple-flights-cancelled-due-to-heat-in-phoenix/

2 https://www.sciencedirect.com/science/article/pii/S2212012218300753

3 I found Ahvaz googling for hot places; I admit that I have never heard of it before even though it has more than a million inhabitants and an international airport, AWZ.


texts: What are the Radarless approach control services in the United States?

texts:
I was recently in Twin Falls, ID at KTWF. There is no radar for approach control services. All instrument approaches are full procedures and aircraft must report all requested fixes.
There is Salt Lake Center radar services at altitudes well above the usual approach and landing phase of flight for KTWF.
When I remarked to tower that is old school, they stated "last of two in the country."
What is the other?


texts:
Aviation confusing me... I’ve read that stall speed doesn’t change (IAS) no matter what altitude you’re flying - of course under specific conditions ISA, 1G level flight, no wind, gross weight etc. then why I keep witnessing for example in the Boeing 737-800 PFD (primary flight display, intend to the barber pole) that at low altitude let’s say your stalling speed is around 140CAS when at cruise level stalling speed is way above - approximately 220CAS (random number) Why is that ? Doesn’t stalling speed must to be the same at all altitudes?

Thank you all for your answers!


texts: What is the procedure after a missed approach at the destination alternate since alternate fuel does not contain a missed app. at the alternate?

texts: I am currently studying the fuel policy planning criteria for ATPL EASA(A) and i just learnt that the alternate fuel does NOT comprise the missed approach at the alternate destination aerodrome; in case of such a situation and without contingency fuel (imagine that is already used during trip), what is the procedure then since that I probably have to use the final reserve fuel? I guess that I should declare an emergency, how would it be declared?


texts: How can I check that the GPS receiver is sending data to the transponder?

texts:
I fly an ultralight aircraft. The GPS is a puck-type device from which the TX line runs to the mode-s transponder. The transponder does not readily show if it is receiving position data. The data is NMEA RMC sentences only, serial 4800 baud 1 message / second.

Is there any way to ascertain as part of the preflight check that the GPS is alive and sending some data (how correct is besides the point, for now)? I'm thinking along the lines of connecting an LED in parallel on the TX line which will flash to show data traffic if I press a test switch. Any ideas? Thx


texts:
Spins cannot occur without stalls. To enter a spin, a pilot would hold the elevator up and let speed bleeds off. This is how you'd approach a stall. Just as the stall starts to develop, apply full rudder; now the world is spinning around you.

Now, how does one enter an inverted spin? How do you stall an aircraft while it is inverted?


texts: What indicated altitude should I hold at after missed approach at KTVL airport

texts:
Assume I'm planning on conducting the GPS RWY 18 approach at KTVL (Lake Tahoe airport) and the current temperature is -40C.  If I execute a missed approach and proceed to the holding fix (HETRY), at what indicated altitude should I hold at.

Here is the GPS RWY 18 approach chart:


texts: What are the differences between Normal and Utiltiy Categories

texts:
In the operating handbooks for GA aircraft, there are often weight and balance limitations listed for both Normal and Utiltity category operation.  If I restrict the loading to the Utility category envelope, I want to know what regulations and prudence allow me to do over the Normal category envelope.

I am guessing that there are a set of regulatory certification standards for each category, as well as a list of specific restrictions for each type certificate.  What are these definitions and where are they found?


texts: Must an instrument approach plate be visible during the approach?

texts: Is there any legal requirement to display the approach plate for an IFR approach? Typically it's briefed as part of the descent checks and then kept on display - but I'm struggling to find any legal requirement to keep it visible.


texts: Is it possible to swap RR trent 900 engines to GP 7200 for existing A380 air frame?

texts: If an A380 was originally equiped with RR trent 900 engines, but decided to switch to GP 7200 for any reason, would this be possible? Has this kind of engine swap (different manufacturer engine swap) been done before?


texts: Can air-superiority radar function as weather radar?

texts:
Can the big, fat, sophisticated air-superiority radar in a modern fighter aircraft's nose serve as a weather radar for navigation in stormy conditions?

Alternatively would a datalink from somebody else (perhaps a tanker assigned to the deployment flight) be used to provide weather radar imagery into the cockpit?


texts: confusion between RNAV and RNP approaches and specifiations

texts: Ive been really confused between these two specifications recently. For example my research suggested that RNP has on board monitoring and alerting and RNAV doesn't require this, however then why must we compute a RAIM check before conducting an RNAV app when for RNAV specification no alerting or failure detection is required and hence TSO 129 may be used? Also doing my flying in Australia some ADs would state there is an RNAV app available for one runway and also an RNP, what additional requirements would there be in terms of pilot training or alerting etc for the RNP app. Appreciate all answers just trying to get a grip with this confusing concept!


texts: How to calculate aileron deflection for achieving similar roll dynamics at thin and dense air?

texts:
my question is inspired by projects like Perlan etc when one is trying to fly in thin air with a glider.
It is well known that at high altitude (say 10-20km) aircraft control becomes 'sluggish'.
However, thinking about lift equation I have encountered a paradox.

According to https://en.wikipedia.org/wiki/Lift_(force)

Lift coefficient is
L=const x rho_air x true_airspeed^2 x surface_area x coefficient_of_lift

Let's neglect the fact that at high altitude, with Reynolds number changing, one will get into a diferent CL (coefficient_of_lift)  vs AOA curve. This is a small issue compared to span of possible rho_air values.
Because this equation has true_airspeed^2, it is obvious that at low altitude, aileron effectiveness (which is also a lifting surface) will raise with second power when increasing TAS which at normal atmospheric conditions and low altitude, low subsonic speeds equals to EAS and CAS (IAS).
If we take any glider and lift it up, rho_air will decrease even by factor of 16 for simplicity. This will be compensated by required TAS forward glide speed by factor of 4, so that wings can still provide equal lifting force, otherwise tha plane would fall because of winning F=m*g - which doesn't care about air composition. The plane will fly faster, and while we should expect that diminished rho_air would diminish aileron effectiveness, increased TAS will naturally compensate for this following the same equation...

I have concluded that starting to roll which requires applying non-opposed rolling force to overcome (constant!) airplane inertia, so that roll rate will rise until it becomes balanced by wing drag resistance, should require identical aileron deflection for airplane at low and high altitude. In other words achievable rates of change of roll rate should be the same at cruise speed in thin air when using the same aileron deflection.

At high altitude however, measured IAS and CAS will be much lower than TAS but that doesn't matters as stable airplane will balance by itself at cruise speed.

Then we come into question what is the maximum roll rate achieved in thin vs dense air. After applying aileron deflection the roll rate will increase, when applied rolling force is compeensated by aircraft drag due to rollign motion whcih is again proportional to constrho_airrollrate^2.

I have concluded that maximum achievable rollrate will be higher at thin air, using the same deflection of ailerons that provide the same overall rollign force at high altitude because the airplame must fly faster just to provide its lift. With the same aileron deflection, achieved stable state roll rates will be higher in thin air than at dense air with the same aileron deflection

If all above is true, why airplanes are said to be 'sluggish at high altitudes due to thin air'.


texts: With the upgrade of the 737 to the Max model, what major changes are incorporated?

texts:
The Boeing 737 was originally designed in the 1960's and flew into the 1980's before a major redesign (the 737-700, -800, and -900 models) was implemented.

Coming up in a few years will be the next major revamp of the line as the 737-Max series (737-7, 737-8, and 737-9).

What major changes have been incorporated in these revisions?


texts: Why are turboprop intakes placed below the propeller?

texts:
On many turboprop aircraft, such as the A400M and the ATR 72, it seems that the air intake tends to be placed below the propeller (images: Wikipedia):

source

source

Given that mounting the intake in a higher location helps reduce the risk of foreign object damage from ingesting debris into the core, why are the intakes still mounted below the propeller? Are the wings and engines already mounted high enough that the intake location doesn't matter when it comes to FOD, or does another issue (maybe accessibility for ground crews?) outweigh the risk of FOD?


texts:
What causes the sudden spool-up sound from an F-16 when enabling afterburner?

I've included a video to make it clear what sound I'm referring to:

at 1:16, I assume the pilot engages afterburner (again), and there is a sudden spool-up sound associated with this.

Am I even correct in assuming this is what's happening? I don't understand what this sound is though, it doesn't seem to appear consistently. Throughout the video, it appears the pilot engages afterburner and turns it off multiple times, but the sound only appears once.

Bonus question: What is the purpose of running the engine like this, and how is the F-16 attached to the ground?


texts: What is the difference between flow separation and turbulent flow?

texts:
For air flowing over a wing, both flow separation and turbulent flow involve disturbed flow next to the surface and smooth flow further away. At what point does one say "oh, this flow has changed from turbulence to separation"  (or vice versa) and why?
I am wondering if separation involves only a disturbed boundary layer, while turbulence can involve a wider disturbance such as in a stall?
For example, is it correct to say that in the stall, an already-turbulent flow (sometimes experienced as burbling) becomes detached?
Or that vortex generators, designed to re-energize a stagnating boundary layer, do so by creating turbulence in order to prevent separation?


texts: Why aren’t multiengine general-aviation aircraft required to be capable of sustained single-engine flight?

texts:
While perusing the See How it Flies website, I came across this alarming statement regarding multiengine general-aviation aircraft:

You must not allow yourself to think that just because airliners can climb with an engine out, your favorite light twin can climb with an engine out.
It is legal to operate a light twin with anemic or nonexistent single-engine climb performance. In such cases, engine failure at low altitude is perhaps the most critical situation that arises in general aviation with any appreciable frequency. Like a single-engine aircraft with partial power failure, you need to make a forced landing.

Given that the main point of having multiple engines is the ability to maintain flight if one of them kicks the bucket in midair, why are GA aircraft with more than one engine allowed to be incapable of maintaining single-engine flight when all this does is double (or triple, or quadruple) the likelihood of a forced landing subsequent to an engine failure?


texts:
I was watching a presentation from a software developers' conference in which the presenter went through the steps leading to the crash of United Airlines Flight 232 to make a point about Crew Resource Management and how it relates to software development.
This prompted me to read the above linked Wikipedia article and see mentions of the flight hours the captain and first officer had accumulated. Now the Wikipedia article on flight hours doesn't explain it, so I was wondering: how are these flight hours logged (and I don't mean on which medium)?

Are fractions of an hour taken into account or only ever full hours? I.e. if some pilot flew 1:27 h on one flight and 1:33 h on another how does that count towards the logged flight hours?
Given many regulations surrounding aviation seem to be global, is the way flight hours are logged uniform around the world?
Any differences between commercial, private and military aviation?

NB: I'm a layperson.

Originally my question also asked for this detail:

Is the time from the gate to the runway counted?

In regard to US regulations it's been answered here


texts: What causes 'wing rock' and how does it work?

texts: Currently studying for a course on fighter aircraft. I came across the phenomenon of 'wing rock', which occurs at very high angles of attack, but I couldn't find any good sources that explain how this phenomenon works in detail. Could anyone give me an explanation of the mechanics of this phenomenon?


texts: What happens if an aircraft goes above maximum altitude?

texts: We all know what happens when a plane goes overspeed... but what happens when a plane goes above their max. altitude? And why are planes certified maximum altitudes anyway? Is it because there won't be enough lift to keep them at that altitude? I know it's not because they don't want the aircraft to get lost in space, because the max. alt. of the Airbus A350 is at FL420, which is not even close to space. Anyone ave an answer?


texts: What is the "A/B AUTO EXT" button for in a Falcon 7X?

texts:
What is the "A/B AUTO EXT" button in the overhead panel of the Dassault Falcon 7X? I see it's in the Flight Control section but I don't know what is its purpose.

(sorry for low quality image)


texts: Can the "G" and "VRB" wind conditions be combined in METARs?

texts:
I have never seen the "VRB" (for wind direction variations < 60°; e.g. VRB12003KT) and "G" annotation (for gusts > 10KT wind speed difference; e.g. 12003GT30KT) being combined in a METAR.

Until now I have just seen:

VRB03KT (so "VRB" without gusts)
12003G30KT 090V150 (so "G" with wind direction variation > 60°)

Why does this never happen? Is there a rule and is it not possible or does it just never happen?


texts: Why use an airplane with non-retractable landing gear for aerobatics?

texts:
I'm watching footage from Red Bull Air Race 2017 in Kazan (one example is

            ) and clearly at least some of the airplanes used have non-retractable landing gear.

I was under impression that non-retractable landing gear increases drag and also makes the airplane larger which is hardly good for application where maneuverability and speed are important.

Why are planes with non-retractable landing gear used in such competitions?


texts: When I use a plotter to identify a direction from a VOR, what heading or course is it exactly?

texts: When I use my ASA IFR plotter and I'm working off a VOR, what direction am I getting? True course, true heading, magnetic heading, magnetic course?


texts: What is the function of the leading edge strip?

texts: I understand the function of every wing part labelled above except the leading edge strip,what is its use in a fabric wing and will the wing function normally without it,if removed?


texts: Why do 20-series Learjets have such an extreme susceptibility to mach tuck?

texts:
Mach tuck is a change (usually nosedown) in an aircraft’s pitching tendency during transonic flight relative to its pitching tendency in below-transonic flight, caused by the appearance of areas of supersonic airflow (with attendant formation of shockwaves, sometimes accompanied by regions of flow separation) around the aircraft when it exceeds its lower critical mach number.  It first showed up immediately prior to and during World War II, as a completely unexpected, and quite deadly, type of loss of control at high speeds (especially on aircraft using the very thick airfoils then in fashion); however, by the mid-1950s, advances in wing and airframe design had reduced mach tuck to little more than a nuisance, allowing even first-generation jetliners to safely fly at transonic speeds without risking a loss of control.1

In contrast, 20-series Learjets, although dating from the 1960s (by which point we already knew very well how to make aircraft highly mach-indifferent), tuck like an aircraft from the 1940s, pitching down suddenly and violently at approximately mach 0.81.  This extreme susceptibility to mach-induced loss of control at high speeds caused a rash of crashes in the 1970s and 1980s, and is one of the many factors that make first-generation Learjets some of the most unforgiving aircraft ever sold to the public (at least, if the NTSB’s AAR archive is anything to go by).2

It is quite hard to see what about these aircraft would cause them to have such evil overmach characteristics; admittedly, they do have straight, rather than swept, wings, but this should impact more where the lower boundary of the transonic flight regime is - not so much how the aircraft behaves once it’s already in transonic flight - and, besides, the thinness of the wings should compensate for their lack of sweep.3

What is the cause of the extreme susceptibility of first-generation Learjets to mach tuck?

1: First-generation jetliners are, nevertheless, generally kept below their lower critical mach numbers in normal line operations, due to the greatly-increased drag associated with transonic flight; however, further design advances, first seen on the Convair 990, greatly mitigated even the transonic drag penalty, with the result that second-generation and later jetliners routinely cruise at transonic speeds.

2: Other factors included a balky autopilot, spoilers that make the aircraft go faster when extended (by causing a large pitch-down tendency of their own), and the fact that their original certificated service ceilings were well into the coffin corner.

3: The reason swept wings help with transonic flight is that they make the wing appear, to the air flowing over it, to be thinner than it actually is, thereby helping to delay and mitigate shockwave formation and flow separation.  These same benefits can also be gained by actually making the wing thinner.


texts: Can a turbofan engine have less noise so that it doesn't disturb our ears?

texts:
A few years back I have seen that Pratt and Whitney 's Geared Turbofan Engine(GTF) has reduced it's noise levels to about 50%. But recently I was having a discussion with a friend and he told me that there is an engine which has the noise levels reduced to about 10%.I tried searching on the net couldn't find any such engine .Is that even possible?
Considering the fact that the most of the noise is from the engine main exhaust.
 Thanks in advance


texts: Are there examples of diverse departure assessment departures in the US or Canada?

texts:
If there is no published departure procedure at an airport with an approach  then you can use what is referred to as a diverse departure assessment departure. I would think that you might find these in places like Kansas and Florida, but a cursory look in these areas doesn’t yield any examples.

Can anyone give examples of diverse departure assessment departures in the US or Canada?


texts: What lights to use for a high-altitude weather balloon?

texts:
I am designing a high-altitude weather balloon for a college project. The balloon may fly at night, which means that, per FAA regulations, I need a light that is visible for 5 miles.

Does anyone know how to calculate this? Or knows some cheap and lightweight LED lights that work for this application?


texts: Does a pilot of Air Force One receive any special privileges?

texts: I know that flying Air Force One is a position of high responsibility. I am curious to know what extra privileges, if any, come along with being the pilot of Air Force One. What extra he can do which a usual commercial/US Air Force pilot is not allowed to do (in air or on ground both)?


texts: Why do cockpit windows often appear to have a rainbow ‘tint’? It’s similar to what you would see when looking at a shallow puddle of water with oil on top. Here is an example of a B777 cockpit window with the same rainbow effect:


texts: Can we change light aircraft skin from aluminum to foam and fiberglass?

texts: Can we change the skin and wings of light aircraft from aluminum to foam and fiberglass composite in zenith ch 750 ?


texts: Is pressure lower than ambient on the pressure (bottom) side of an airfoil?

texts:
I've been reading about this for quite some time and thought I understood it. Then somewhere someone mentions that air under the wing has higher velocity than ambient thus a lower pressure than ambient. I couldn't find any other reference to this so here I am.

What this means is that, in a purely hypothetical situation, without the upper part of the wing generating a lower pressure zone the airplane would actually be pulled down because the pressure on top would be ambient thus higher pressure than the bottom.

This makes sense since hitting air molecules with the wings will cause them to accelerate and suddenly move faster than ambient, thus have lower pressure.

How accurate is this?

Picture version:


texts: What are the typical lift, lift coefficient and drag coefficient for a A320 in cruise?

texts:
What would you expect the typical lift force and coefficient of lift and drag to be for a A320 at cruise?

Considering flight at 36,000 ft, mass approximately 72 tons, velocity 230 m/s with a surface area of 122.6 m² and density 0.366 kg/m³.

The results I've calculated seem a little high, CL=0.666 and L=724 kN


texts: What does a pilot have to do in order to fly as a second in command in a private jet?

texts: If a pilot has the opportunity to fly as an SIC in a private jet, what FAA requirements must they comply with in order to fly with passengers?


texts: How can a private pilot prepare for a long cross country flight in an unfamiliar area?

texts:
TL/DR: What are common preparation tips or techniques for low-hour private pilots planning long cross country flights in unfamiliar territory?

I got my private pilot's license in November 2016 in Hawaii. I've since moved back to the mainland to continue working and flying here. I'm currently in Phoenix and have been checked out for Cessna 172 rentals at a local airfield.

Over MLK weekend (Jan 14-16) if the weather is nice I hope to fly from Glendale (KGEU) to San Luis Obispo (KSBP) then to Rancho Murieta (KRIU) near Sacramento, and back to Phoenix. My girlfriend plans to come with me and I want to do everything that I can to prep and plan this flight to minimize our risk.

I have about 75 hours total time, mostly in 172s and DA40s and all my cross country time has been on the Hawaiian islands where it is nearly impossible to get lost and there are few airspaces enroute.

I'm very comfortable with VOR navigation but I'm not yet accustomed to the smaller Garmin G430 GPS unit in the Cessna here (I'm spoiled, used to the G1000) so I don't want to stress with the GPS unit.

I'm most concerned with the strength of my pilotage and dead reckoning and whether they are up to the task, especially considering that this will be my first flight in the region. Since VOR is line-of-sight and there more than a few mountains in the region I want to feel confident that I can get us there safely in case the VOR signals aren't being received for the duration.

I have the routes planned, altitudes selected, waypoints and frequencies written down, performance planning and W+B done, etc. and I plan to speak with my local flight instructor to go over all of these materials before the flight.

In any case, it would be great to hear additional tips/tricks/things to be aware of/mistakes that you made early in your flying career so that I can be as prepared as possible moving forward!


texts: Why Air France 447 could not reduce angle of attack?

texts:
I just finished reading this article and couldn't understand why in 3 minutes and 30 seconds even though there was no reliable speed data, pilot could not level the plane? Isn't the angle of attack reported by a gravity based tool like in off-road vehicles?

Summed up Question: When it's unclear what is happening with the aircraft, isn't it safer to put it in level position and medium speed? (Sorry for rudimentry language here)


texts: What type of helicopter is shown in Star Wars The Last Jedi featurette?

texts:
There is a nice featurette about the new Star Wars movie The Last Jedi.

One shot (1:32) shows a helicopter in the background. What is it?


texts: On a centrifugal compressor impeller what is the difference between the radial vanes and rotating guide vanes?

texts:
I thought the radial vanes were a machined part of the impeller that just force the airstream radially? And that another name was rotating guide vanes as they are rotating with the impeller disc.. But the picture from a textbook I have is referring to them as 2 different things? Or have i misunderstood something?

Thanks