How do you know 'when' an aircraft has stalled?

[naremman]

Who says the stick has to be back for the aircraft to be stalled?

You are not incorrect Mazda, but in the run of the mill RAA aircraft a stall induced by a whole heap of forward stick is probably going to be pretty ugly.

 

Can remember being briefed for a Royal Aero Club WA Aerobatic comp by Squadron Leader Don Pollock when a half reverse Cuban was part of the sequence. He stated that while Mr Arresti required the right way up and inverted component of the upward 45 to be equal in distance, but glancing around at the apron and seeing a collection of Aerobats, Airtourers and Tiger Moths present, he said he was very comfortable to be on the ground judging in case anybody got too keen on pushing the upwards inverted!!

 

To pick up on the thread. How can you tell when an aircraft is stalled? In some aircraft not too easily. I have flown a few where they have just mushed about with no well defined nose drop. The Tiger Moth and Airtourer are both out of the textbook for stalling. My experience in J160 and Foxabt both, in the flapless configuration, did not produce a defined nose drop no matter how aggressive you approached it, In a Warrior, if you ignored the VSI, you would call stalling a non event.

 

I suppose as a traditionalist, any good trainer should display an identifiable stall. All other aircraft should at least have a stall where a pilot is aware that the airflow over the wing is disturbed, lest we run the risk of the ground coming up to smite thee.

 

 

[Powerin]

My experience in J160 and Foxabt both, in the flapless configuration, did not produce a defined nose drop no matter how aggressive you approached it, In a Warrior, if you ignored the VSI, you would call stalling a non event.

Off-topic....how does that work? The elevator runs out of authority before the wing stalls I guess...but does the HS stall, or run out of airflow, or get blanked by the wing?

Is it a good thing or a bad thing that these aircraft do this? (feature or bug)

 

 

[Guest davidh10]

When weight exceeds lift and drag exceeds thrust?happy days

This also fits the situation where you are in a non-stalled descent with a negative acceleration (slowing airspeed), as you are likely to do in preparation for landing.

In normal flight:-

 

• Every time you decrease your airspeed, drag exceeds thrust. That is what causes you to slow down.
   
   
  
• Every time you descend, weight exceeds lift. That is what causes you to lose altitude.
   
   
  

 

 

 

 

[shags_j]

Out of interest, out of the people in this thread that have answered, who flies in aircraft without stall warnings? If you did your training in an aircraft without a stall warning would you recognise the symtons as easily (particularly if you are low hours)?

 

Every time I am out on my own I practice stalls a little bit (usually on my way back home). I believe this has helped me to identify both when a stall is going to occur and when it has occured.

 

Not that stalling the tecnam is easy to do. Nor is it very evident. In my test for my pilot certificate we just couldn't get it to stall impressively. Just perfect flying conditions, as soon as the nose dropped the aircraft basically reasserted authority.

 

In the Cherokee however, you could really tell when that bad boy stalled. You'd almost be diving vertically.

 

 

[facthunter]

OK assuming that the question is not a totally"trick" question. How do YOU know when an aircraft has stalled?

 

You probably shouldn't be in the thing if you don't have a fair idea, that it is stalled when it has stalled. Again, I am not answering the question. So.

 

The ASI will indicate a number which is near the stall speed.( for whatever "G" loading you have.) If you have an angle of attack indicator it will read beyond the critical angle where that particular wing stalls.

 

IF you had tufts of wool all over the top surface of the wing, their orientation would indicate a stall. (Severe airflow separation) The aircraft's performance will be minimal. Nev

 

 

[Guest davidh10]

Out of interest, out of the people in this thread that have answered, who flies in aircraft without stall warnings? ...

Trikes don't have stall warnings and the one I fly is actually difficult to get it to stall fully (particularly with only 1 POB). It will just mush unless you push it up into a stall.

 

Reality may be harder to pick than in practise. You usually practise in calm conditions and level flight. A few weeks back, I was joining the circuit to land on a day when there was a fair amount of very gusty wind and just as I was turning base, the ASI suddenly dropped from 60 to about 45kn. I felt it first; as a bump and loss of lift in the turn, then glanced at the ASI. My reaction was instinctive; to just ease the AOA a little. Then the gust passed and the ASI was back to 60kn. All over in a couple of seconds.

 

So; Did it actually stall momentarily? Hard to tell, as the aircraft movement and loss of lift could have been gust induced or could have been caused by a momentary stall or partial stall. As I was banking at the time, the increased wing loading increases the stall speed above the S/L flight stall speed and the gust may both increase wing loading momentarily as well as change the relative airflow, and hence AOA.

 

Loss of altitude is not an indication by itself. Just up / down draughts associated with thermals can do that. Last Saturday, I tightened my seat belt a little after the aircraft tried to drop out from under me, due solely to a down draught associated with a thermal. Just a once-off occurrence during the flight, but I was encountering up and down draughts that were taking me up and down at over 800'/minute.

 

The point is that while steady state conditions are quite clinical and definitive, in other than those conditions, it may not be quite as clear cut.

 

 

[facthunter]

The whole method of stall training should be reviewed. The "classic" S&L, power off, hold the nose up, probably lulls people into a false sense of security. Most aircraft are set up to be docile in the stall, by not having enough back elevator effect to get, and hold, a full stall.. They can ALL bite however, Just get one a little tail heavy and in a steep turn with a little top rudder and the whole scene can go pearshaped quickly. ( Usually turning final from a base where there is a tailwind ) or such. Nev

 

 

[naremman]

Out of interest, out of the people in this thread that have answered, who flies in aircraft without stall warnings? If you did your training in an aircraft without a stall warning would you recognise the symtons as easily (particularly if you are low hours)?The Tiger Moth is classic in this department. What you hear and feel leaves one in no doubt as to what is approaching. A Tiger with the slats unlocked has an unmistakeable sound hwen the slats deploy.

 

In the Airtourer the stall warning horn only works with flap deployed, as it would drive you nuts in aerobatics. The horn is a circa 1960's Holden car horn and does it go off. In the flapless configuration the feedback comes initially from the tailplane with light buffet occurring, progressing through to some robust "oil canning" in more extreme turns or aeros. Elevator authority still remains pretty sound despite the sound effects.

[naremman]

The whole method of stall training should be reviewed. The "classic" S&L, power off, hold the nose up, probably lulls people into a false sense of security. Most aircraft are set up to be docile in the stall, by not having enough back elevator effect to get, and hold, a full stall.. They can ALL bite however, Just get one a little tail heavy and in a steep turn with a little top rudder and the whole scene can go pearshaped quickly. ( Usually turning final from a base where there is a tailwind ) or such. Nev

Well said Nev. Every pilot needs this mantra constantly repeated to them, starting initially in the early hours of training, especially when they are let loose as training is completed, and certainly whenever a pilot starts to take an aircraft forgranted.

 

We could add mustering to the activities that have given some pretty dramatic examples of how ugly the stall/spin scenario can get. I still recall the images of some Cessna 150s that have "candled" mustering.

 

 

[turboplanner]

Has anyone answered the question yet?

 

 

[facthunter]

It's not an instantaneous thing. The wing gradually ( from the rear) goes to turbulent ( non laminar flow). The airflow even reverses direction near the trailing edge. What does happen that is really quick is the wing drop (roll) which allows the rapid onset of stall conditions on the downgoing wing.

 

Most of the lift from the top of the wing is in the first half of the chord, Some vortices occurr on the rear part of the wing at medium angles of attack too, progressively extending to the forward area, as the engle of attack increases. This is why the L/D ratio of an airfoil varies. Vortices represent a loss of energy (Aerodynamic Efficiency). Whilever there is forward motion there will be some part of the wing that is not stalled. VG's and slats/slots help sustain this, near the leading edge..

 

This is why very high aspect ratio wings are so efficient. The rear part of a wing only works aerodynamically at low attack angles.( unless you have flaps ( slotted) and suck and blow devices to maintain the airflow. Nev

 

 

[turboplanner]

We've all come up with theories, but the question was:

 

How do you know.......when an aircraft........has stalled?

 

 

[ahlocks]

How do you know.......when an aircraft........has stalled?

When the spinney thing stops turning and a little red light comes on.....?

 

 

[turboplanner]

When the spinney thing stops turning and a little red light comes on.....?

...at exactly the same time you sit on top of the broomstick.

 

 

[ahlocks]

Nah.... Turning the fuel on usually sorts it out....

 

 

[facthunter]

I thought it might be a good idea to know what a stall is and what the stalled condition means. If we all have different ideas, how are we going to arrive at any sort of concensus. Ok some genius tell us and let's get it over with. Nev.

 

 

[facthunter]

I've worked it out. When the stick shaker activates and the rectangular thing in the middle of the Dash with STALL on it flashes. That's gotta be the answer. Nev

 

 

[ahlocks]

... the rectangular thing in the middle of the Dash with STALL on it flashes. That's gotta be the answer. Nev

... I gotta get me one of those things! ()

 

 

[facthunter]

You won't be safe until you do. Nev

 

 

[djpacro]

This question was asked by Mr DJP and I have really enjoyed thinking about it....

[facthunter]

Just another good example of a situation justifying an angle of attack indication. We had a long thread about THAT sometime ago. I don't need convincing of its value. ( but a thread of wool out the front will do as much, if you like simplicity as I do. It doesn't work it there is a prop there). Nev

 

 

[djpacro]

I've worked it out. When the stick shaker activates and the rectangular thing in the middle of the Dash with STALL on it flashes. That's gotta be the answer. Nev

[turboplanner]

But you haven't answered the "How you know" for us DJ...........Sh$t don't tell me you don't know either!????

 

 

[facthunter]

And I thought MY instrument unusual attitudes instructor was a Bit hard. Nev

 

 

[fly_tornado]

the wings as a control surface or as a generator of lift. By definition a stall is where your wing stops generating lift.