Brain Teaser: Stalling by PUSHING the Stick

[facthunter]

How?

 

There are quite a few ways. The load can shift, passengers can relocate themselves, when not supervised. The configuration of the plane can be changed without applying the new index. Items can be double loaded or placed in the wrong locker. etc. A tricycle undercarriage aircraft can get airborne in a dangerously tail heavy state because the propwash will keep the elevator functioning, and the tricycle undercarriage has the obvious effect. This does not happen with a power-off approach. Nev..

 

 

[Guest RogerRammedJet]

Outside snap roll - the wing is stalled with the stick full forward (and full rudder in the direction of the roll)!

 

OK - cough up my lolli!

 

Rog

 

 

[Guest airsick]

the aircraft is oriented in an upright position

 

Outside snap roll - the wing is stalled with the stick full forward (and full rudder in the direction of the roll)!OK - cough up my lolli!

If you get a lolli then my answer certainly deserves one. Since when is snap rolling considered as an upright position?

 

 

[blueshed]

I reckon that one would assume that in the original question the aircraft would have been within c of g limits and the loads were secured in position.

 

And all very interesting analagies!

 

As the horizontal stabilizer does have an angle of incidence to the main wing, the main plane will usually stall before the tail plane, so if the machine is loaded correctly you should not get the tail plane to stall!

 

If you were in straight and level flight and pushed the stick full forward and you changed the angle of attack to a negative 16 degrees will it stall and as it stalls will the nose become raised as in the oposite if you were to stall the aircraft with a positive angle of attack?????????????

 

Oh No

 

What a Proposal Guy

 

 

[Guest pelorus32]

I reckon that one would assume that in the original question the aircraft would have been within c of g limits and the loads were secured in position.And all very interesting analagies!

 

As the horizontal stabilizer does have an angle of incidence to the main wing, the main plane will usually stall before the tail plane, so if the machine is loaded correctly you should not get the tail plane to stall!

 

If you were in straight and level flight and pushed the stick full forward and you changed the angle of attack to a negative 16 degrees will it stall and as it stalls will the nose become raised as in the oposite if you were to stall the aircraft with a positive angle of attack?????????????

 

Oh No

 

What a Proposal Guy

The answer is in post #16 in this thread.

 

The critical thing is that coming across the top the g is less than 1 and the airspeed can therefore be below the 1g stall speed. If you then push hard you can quickly build negative g, the speed is low and so you very rapidly get to a negative critical angle of attack.

 

No fancy stuff with C of G or shifting loads or stalling tailplanes, just nice simple aerodynamics.

 

Regards

 

Mike

 

 

[Yenn]

It will take a bit of reading to work that one out, but I will get my head around it.

 

 

[djpacro]

"AEROBATICS" by Neil Williams. Been a while since I've taken it off the bookshelf. The earlier reference to Neil's book was probably his mention of upright entries to inverted spins. Up to about 15 years ago it was a standard figure in Advanced competition aerobatics. The Pitts, for example, goes in quite neatly. i.e. decellerate as you would normally to enter an upright spin and a few knots above the stall push the stick forward (instead of pulling back) and push on the rudder. Aileron helps to get it rolling neatly. Without the aileron there's a more pronounced nose-down pitch before it starts to auto-rotate.

 

Sometimes get students doing it inadvertently near the end of a roll-off-the-top.

 

PS - some aircraft, sometimes there is an upload on the horizontal tail.

 

 

[Seal]

PS - some aircraft, sometimes there is an upload on the horizontal tail.

Care to elaborate? For example:

 

What type of flight regime?

 

Up relative to what?

 

Are we talking planes controllable by people or things that need one or more black boxes to make them behave?

 

 

[djpacro]

Some light reading material which may answer you question:

 

- near the top of http://www.zenithair.com/kit-data/ht-90-5.html - see Fig 8

 

- near the bottom of http://www.pilotfriend.com/training/flight_training/wt_bal.htm

 

- Mechanics of Flight by Kermode. Page 160 and subsequent

 

Enough of theory - flight tests of the Bell XS-1, Fig 6 of http://www.nasa.gov/centers/dryden/pdf/87529main_RM-L8A23A.pdf