Ailerons In The Stall

[VicariousLiving]

Why does that make what Baronman said wrong? If they continue to be effective then they cause the wing to exceed the critical angle of attack more.

An aileron beyond the critical angle of attack will not maintain roll control per the requirements of the previous Part 23 reference. Per Part 23 aircraft design requirements, the wing is designed such that the tips (and ailerons) do not stall as the wing root stalls. The root stalls, the wing pitches down, and the wing tip/aileron portion of the wing never reaches critical AOA.

 

[mtsu_av8er]

An aileron beyond the critical angle of attack will not maintain roll control per the requirements of the previous Part 23 reference.

Vic, you've lost me . . .

 

[shooter13]

Theotokos

on my 150 it takes 6 seconds for the flaps to move to 10 degrees. It only takes about 3 to get from 10 to 20 degrees. It is about the same from 20 to 30 and from 30 to 40. I rarely ever use 40 degrees and I land normally at 20 degrees flaps. I try to get them in on the base turn and then not change it. When I first started flying the airplane I would count and then verify by looking but I can see my indicator from my normal position. Now, i don't really count. I have just gotten used to it and hold the switch for what feels like the right amount of time and verify as I do it. I only tell you this becuase if your 152 is like my 150, counting for 5 seconds for each ten degrees won't quite work.

 

[MidlifeFlyer]

The root stalls, the wing pitches down, and the wing tip/aileron portion of the wing never reaches critical AOA.

...and a spin is impossible.

 

[VicariousLiving]

...and a spin is impossible.

Vic, you've lost me . . .

Questions for the confused and sarcastic:

1. What does it take to initiate a spin?
2. Does lift increase or decrease as the airfoil AOA increases beyond the critical AOA?
3. Does induced drag increase or decrease with decreasing lift?
4. In case you can't solve the above--where'd the increasing adverse yaw come from?

 

[mtsu_av8er]

...and a spin is impossible.

- I almost said the same . . . :rawk:

I knew we'd get along swell, Midlife . . .

 

[VicariousLiving]

- I almost said the same . . .

I knew we'd get along swell, Midlife . . .

Okay, I tried educational prodding, but it appears for some folks their ignorance is militantly protected.

Let’s debunk the misinformation. We started this sub-discussion with the following statement:

So now let's say the aircraft is stalled and you agressively apply aileron. If you try to roll left (turing the yoke to the left) the right aileron goes down increasing the AOA of attack on the right. BAD!! Why? Cause we had already exceeded the critical angle of attack, now we lower the aileron (change the chord) and exceed the critical angle even more.

Why is this statement incorrect? It is incorrect because per Part 23 certification requirements the ailerons must continue to function normally throughout the stall. In order to do so, the aileron wing section cannot be stalled. Therefore, if the aileron cannot be stalled then the AOA of the aileron wing section cannot be beyond the critical AOA. Furthermore, deflecting the aileron downward in the stall cannot result in increasing the AOA of the aileron wing section beyond the critical AOA, much less result in increasing the aileron wing section AOA further beyond the critical AOA.

For reference purposes in continuing this discussion:

§ 23.201 Wings level stall.

(a) It must be possible to produce and to correct roll by unreversed use of the rolling control and to produce and to correct yaw by unreversed use of the directional control, up to the time the airplane stalls.
...
(d) During the entry into and the recovery from the maneuver, it must be possible to prevent more than 15 degrees of roll or yaw by the normal use of controls.

§ 23.203 Turning flight and accelerated turning stalls.

Turning flight and accelerated turning stalls must be demonstrated in tests as follows:
(a) Establish and maintain a coordinated turn in a 30 degree bank. Reduce speed by steadily and progressively tightening the turn with the elevator until the airplane is stalled, as defined in §23.201(b). …
(b) After the airplane has stalled, as defined in §23.201(b), it must be possible to regain wings level flight by normal use of the flight controls, but without increasing power and without—
…
(3) Uncontrollable tendency to spin;


Taking the above aircraft certification requirements point by point as a means to debunk the original, incorrect statement:

If an aircraft meets the certification requirements of 23.201(a), "...produce ... roll by unreversed use of the rolling control...up to the time the aircraft stalls...", then it should be obvious that aileron deflection may not cause the aileron wing section to either exceed the critical AOA, nor, as was claimed in the incorrect statement which began this sub-topic, cause the AOA to increase further beyond the critical AOA. Why? If the aileron deflection caused the aileron wing section to stall before the main wing stall, then aileron control would be reverse (the aircraft would roll into the downward deflected aileron).

IOW, assume the aircraft is nearing stall, but not yet stalled. If the original statement were true (lowering aileron can exceed critical AOA or further exceed critical AOA) then lowering an aileron near the stall would cause the aileron wing section to stall first, dropping that wing as a result and causing the aircraft to roll in the opposite direction of the roll control input. Such a roll reaction would be a reversed use of the rolling control, and therefore a clear violation of 23.201(a).

Furthermore, during the stall recovery the original statement is also obviously false as such performance would violate 23.201(d). To illustrate this point, assume the aircraft is stalled. Assume for a moment that the original statement actually is correct (it isn't, but the assumption makes the contrary proof quite simple). If deflecting the aileron downward caused the aileron wing section to further exceed the critical AOA, the lift generated on that wing would decrease further (lift decreases on either side of the critical AOA). Decreasing the lift on the downward deflected aileron side of the wing would cause the aircraft to roll towards that wing (aileron), which is quite obviously a reversed roll control. Reversed roll control obviously does not qualify as "...normal use of controls..." and therefore would violate the certification requirements of 23.201(d).

We then get to MidlifeFlyer's and mtsu_av8er's incorrect claims that the aircraft will spin due to this supposed aileron deflection inducing a wing section stall by exceeding of the critical AOA or increasing AOA beyond the critical AOA. We can debunk this myth via 23.203(b)(3). If use of the aileron would indeed cause one section of the wing to stall, or to stall further, and therefore enter a spin, such would clearly be a violation of the requirement:

"After the airplane has stalled...it must be possible to regain wings level flight by normal use of the flight controls...without...Uncontrollable tendency to spin..."
(emphasis added)

IOW, if the statement made by MidlifeFlyer and mtsu_av8er were correct normal use of the aileron control would induce a spin, which is clearly not legal in a Part 23 certified aircraft, nor is it observed by anyone who has actually read the FAA's "Airplane Flying Handbook" and followed the FAA advice to recover from stalls via coordinated control inputs. Use aileron, keep it coordinated, no spin.

Yes, it is possible to develop a spin out of a stall. What is required for the spin to develop is a yaw moment. Aileron deflection can lead to a spin if the aileron deflection is uncoordinated. The downward aileron deflection creates more lift (not less, as the original false statement claimed), which creates more induced drag, which in turn creates adverse yaw. It is this adverse yaw, which, if left uncorrected (uncoordinated) will result in a spin--not aileron wing section AOA beyond the critical AOA, nor increasing beyond the critical AOA.

Hopefully the above explanation was sufficiently clear that other readers will understand the aerodynamics that baronman, MidlifeFlyer, and mtsu_av8er obviously did not understand, and the reader will then be able to discard the misinformation presented in their posts.

As a final note, Mr. mtsu_av8er (and, to a lesser extent, Mr. MidlifeFlyer),
I suggest you reread FAA-H-8083-9, "Flight Instructor's Handbook" as you have obviously forgotten a recurrent theme found in that text which is succinctly exemplified by the following quote:

"Part of being a professional aviation instructor is being knowledgeable on the subjects of aviation and instructing. Instructors need to continually update their knowledge and skills."

In closing, in the words of Dean Wermer ("Animal House"):

"Fat and stupid is no way to go through life."

(apologies if I butchered the exact quote or the Dean's name)

 

[naunga]

Well, pitching the nose down alone to correct for a possible stalling condition isn't a good plan either. Especially on landing when you are probably at a reduced power setting.

I was taught, on landings, to never pitch down or up without a slight power change. The reason is that if you're already at say 70 or even 80 kts that's very close to slow flight. The plane is already dirty from the flaps etc. So to build up any speed you're going to have to pitch pretty far forward, but at that low speed you're going to lose altitute fast. So pitch for speed, power for altitite.

On take off it's different, because you should already be at full power. In most cases if it feels like you're pitching up too high and thereby going to slow, it's because you didn't trim correctly. Remember when you add power the nose is naturally going to want to pitch up at least momentarily. You need to add a little forward pressure and then trim to hold you attitude and speed.

Just a couple of tips you might try (cause I been where you are)...

You cannot just hit the button and it moves to the next degree of flaps. You have to hold it until it reaches the desired degree.

Try looking at the flaps themselves. Forget the indicator as the primary means of confirming the flaps are deployed. Used that as a backup. Once you figure out what 15° of flaps looks like on the wings, you'll just need to look at them briefly, then confirm. Then you're not having to put your head back into the cockpit.

Don't be afraid of stalls, but have a healthy respect for them. They can, obviously, ruin your whole day. Also remember as someone said, you stall, because the wings can no longer generate lift, which would also mean the ailerons are going to be ineffective (remember the mushiness of the control right before the stall? Well there you go). Although it is important to keep them neutral.

If the wing dips remember it's rudder that corrects it. Opposite from the dip (if I recall correctly) so dips right, left rudder, dips left, right rudder.

Most of all relax. Flying is supposed to be fun, and with your CFI there there isn't a whole lot that you can do that they can't get you out of.

Later

Naunga

 

[mtsu_av8er]

. . . nor is it observed by anyone who has actually read the FAA's "Airplane Flying Handbook" and followed the FAA advice to recover from stalls via coordinated control inputs.

You're right, I haven't ever read that one . . .