39

Yes it's called a Deep Stall, and is mostly a problem with T Tail aircraft, especially jets with Supercritical Airfoil wings (like the CRJ Regional Jet line). Such wings stall from the leading edge and the stall's flow separation spreads rapidly and completely across the entire wing all at once, so there is very little residual nose down pitching moment. ...


12

Airspeed dictates how (and if) a plane flies because it relative to the air that the plane is flying through, the only thing that matters for aerodynamics. Groundspeed can be greater or less than the airspeed depending on which way the air is moving over the ground, i.e. wind. The latter is only important for figuring out when you'll arrive at your ...


9

There are a few electric aircraft now, and because batteries hold far less energy than fuel, they're low-performance and short-range compared to normal aircraft. If we imagine that at some point in the future we'll have batteries that can match fuel, the answer would be: Only slightly. Back in the 60's and 70's, airliners regularly carried a flight ...


8

A performance increase after a compressor wash is expected to happen, but it does not return to the original performance as there are more degradation mechanisms at play. This answer explains that organic build-up causes a change in airfoil shape causing the recoverable performance degradation. Another source may be deposition of salts and dissolved ...


6

What you describe is a tailslide, as another answer has noted -- but there is a condition in which the wing is stalled and the normal recovery method (apply down elevator and wait for the nose to drop and airspeed to build) can't be used. It's called a "deep stall" and is only a problem with certain layouts of flying surfaces. One of the best known is a T-...


5

The compressor blades accumulate a coating of organic material from the atmosphere on the blades, which in the later stages, where the temperatures get above the material's flash point, may be mostly carbon from cooked organic material like pollen and bugs (the same sort of blackened accumulated crud you'll see on the butterfly of a late stage compressor ...


5

For an ultralight with rudder only roll control, which achieves lateral control with a lot of dihedral to create a really strong roll/yaw couple, the issue would be how much reserve rudder authority is there once enough has been applied to counteract asymmetric thrust. That would determine how much roll rate you could still achieve trying to yaw toward the ...


4

When turning on the Anti-Ice, the demand for bleed air increases and the EEC (Electronic Engine Control) will increase the target N1 to provide enough pressure by injecting more fuel. From the Boeing 737 NG FCOMv2 (7.20.5 Engines, APU - Engine System Description, emphasis mine): In the normal mode, the EEC uses sensed flight conditions and bleed air ...


4

The groundspeed can be more, less or the same as the airspeed. Go back to boats. I'm driving around in my boat on a big river with a 5 mph current. My boat goes 30 mph. If I'm going with the current, my boat is going 35mph relative to the river bottom and the shoreline. If I turn around and go the other way, my boat is going 25mph relative to the river ...


3

Yes. Moving CG farther and farther back will eventually cause the plane to be directionally stable falling backwards. Abusing rearward CG limits is contributory to this condition. Secondly, poor design of horizontal stabilizer, particularly, lacking sufficient "weathervaning" area, will cause an aircraft to be more susceptible to the unrecoverable "deep ...


3

Groundspeed is the MOST important speed to know when it comes to flight planning, and flight monitoring. If you don’t know how much time it will take to arrive at your destination, you may never arrive. There is is only a finite amount of fuel in your tanks. Every flight has to use estimated groundspeed before the flight, and actual groundspeed during the ...


3

Robin makes a lot of great points, but since we are talking on a purely hypothetical case lets have fun and take it to supersonic speeds. Let's assume that somehow batteries have the required energy density to be used to run some sort of low-bypass electric turbofan to propel our aircraft to high speeds where the neutral point of the aircraft starts ...


3

Yes you simply fly with the pressurization system set to a mode that holds the outflow valve open so the air conditioning air being pumped in can't "inflate" the cabin; it all just goes overboard. Most transport aircraft have a specific QRH procedure for "unpressurized flight", which among other things, limits the maximum altitude to 10000 ft, the altitude ...


3

Turning on Engine Anti-Ice causes the engine idle N1 to automatically increase so that it can supply additional bleed air and not flame out. This means that for descent planning, an earlier descent should be planned since idle N1 is now producing higher thrust.


2

The formula from wikipedia is a rough estimation. Think of it as a rule of thumb. It's useful if you need numbers for rough calculations. However, the exact formula is as shown below: According to that formula, I calculated pressure altitude difference for 28.92 and it's 938 feet, as opposed to 1000 feet. Additionally, as you can tell from the formula, the ...


1

If a conventionally laid out aircraft is flown into a tail slide, it's unlikely that it could maintain that attitude for long. The tail has low mass relative to the rest of the aircraft and a substantial moment between the tail surfaces and aircraft center of mass. As negative airspeed (falling down tail first) builds, aerodynamic forces on the tail will ...


1

The F-16 is unstable at low speeds, and stable at higher Mach numbers. It has a flight control computer though, which stabilizes the aircraft using the feedback from pitch rate (so from the view of the pilot an F-16 acts similarly as a stable aircraft). This applies to both positive and negative attitude disturbances, so for both + and - G loads perceived by ...


1

I work within a engine test facility. During a compressor wash process we inject water and detergent. This also depends on how much work have been carried out during the overhaul on the engine. The positions are given only to provide an even flow of water through the engine. Sadly I have no experience with live aircraft, so I can not comment when their on ...


1

Unless someone can find an old 14CFR Part 25 ruling that has the explicit reasoning, I believe you are right to consider that the rationale for giving extra performance credit to airplanes that have demonstrated minimum unstick speed ($V_{MU}$) limited by tail contact is that they are not limited by aerodynamics. However, I should point out that the intent ...


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