whip stalls

[MikeSt]

... are prohibited in Cessna 172's / 152's, and I presume any other light aircrat.

Is that because of excessive negative g's being developed ?

What would be a guesstimate on the amount of g's developed ?

Mike

[Ollie]

The number of positive G's involved in entering a high speed stall depend on the air speed and the radius of the flight path. G's=total lift force/weight. G's=( V^2)/gxr. The smaller the radius the greater the G's. How small the radius can be depends on the maximum lift coefficient of the wing, assuming the elevator power is enough to force the wing to its maximum lift coefficient. So there are a lot of variables to tie down before you can define the maximum G's that a high speed stall will produce. The number of G' will be equal to the ratio of coefficient of lift in level flight to the coefficient of lift in the high speed stall. As a very rough guess I think a Cessna could try to pull at least 6 G's positive in a high speed stall, which could very well result in serious structural damage. That's from level flight. If the maneuver is entered from a dive, the potential for damage is far greater.

[Hostage-46]

Never heard the term whip stall.

Do you mean a snap roll? I'd think it would be tough to do one in a Cessna, tough enough to get one to spin. I'd suspect they are prohibited.

Accelerated stalls are no biggie, just exceed the stall AOA, as long as you below max manuever speed the stall break occurs and it's very gentle.

Initially I thought you may be referring to the adverse yaw departure, though I don't know if that's taught in civil aviation.

Thats when your poking around at a high angle of attack and not paying attention to the rudder and flying an uncoordinated turn.

This was a problem in the T2-C for new guys in the landing pattern. Straight wing, Navy training jet.

Your low and slow, over shoot the turn to final so you wrap it up. Your looking outside, not at the ball, maybe your feet are on the floor...

You need more back stick to hold the decent rate at the higher Angle of bank and, because you're behind the airplane, dont add enough power to compensate, so your getting slower and slower , rolling tigher to make the runway and your still not minding the ball.

Add a little more aileron to roll her up a bit more and BANG.

The two elements require for a spin, a stalled wing and yaw come together at 300 feet AGL.

In the above scenerio, the plane stalls in descending left turn then then the adverse yaw violenly snap rolls back to the right and, at 600 feet or so, it's all over.

Stalls in the landing pattern... not a good thing ...

[MikeSt]

A whip stall is like a 'straight" hammerhead.

Plane climbs vertically straight up, then nose drops.

Think of the plane pivoting through its tail.

Mike

[Hostage-46]

Oh .... a tailslide :)


that would be interesting in a Cessna ..... but not very :)

The biggest problem would be with airspeed control. A tailside is a low G manuever.

However when the nose falls through you'd need to get be at idle on the power and recover promplty to prevent the rapid build up of airspeed.

I'd suspect you'd go racing throught redline pretty easily, all those struts and things hanging off ..... not pretty.

[Ollie]

In the tail slide part of the maneuver the plane is traveling tail first and all the control surfaces are under very heavy loads from trying to reverse themselves (weather vane) 180 degrees. If this part of the maneuver persists until the airspeed builds too much the control surfaces, linkages, etc. may be damaged. Certainly the stick or control yoke will be forced to its limits and the pilot won't be able to budge it until the plane turns nose down for recovery.

BTW, this isn't a stall in the sense of exceeding a certain angle of attack. When the plane goes vertical the wing lift goes to zero to maintain the vertical path and the angle of attack goes to the zerolift angle of attack which is far from the normal stalling angle of attack.

[Hostage-46]

True,

In this case you might be at a very low AOA, but airflow just stops as the plane slows. Thrust, drag and gravity all in the Vertical.

However, the wing will still generate lift if thier is enough airspeed. Stray from the Cessna example and think of an F/A18 in the vertical. It still generates lift based upon AOA reagardless of attitude.

Couple with this enging torque and, and extreme attitudes, the post stall gyrations are indeed a violent event for the uninitiated, at this point you are a passenger.

The flight control feed back can be controled if expected and the flight forces aren't as bad as one would think. With the low airspeeds the loads are not very high.

Holding the nose vertical and actually doing a tailside is a pretty advanced manuever and takes silk hands.

That all said, I'd find that a bit unsettling in a Cessna....

[MikeSt]

Originally posted by Dan Ahearn
True,

That all said, I'd find that a bit unsettling in a Cessna....

I have no intention of ever trying this manouver in a Cessna !

I am merely curious at what loads would be involved.

And I don't think it neccesarily has to be a true "tailslide" to be a whip stall. Just getting the nose up to about 40-50-60 deg could be enough to "whip" the nose down (Although I must admit I have not seen the actual definiition for this manouver).

Mike

[Gary Warner]

I'm 99% sure the "No whip stalls" in the manual refers to the potential for rudder and elevator damage due to reverse air flow over them. It would do serious damage to the control system if the yoke or pedals were slammed to their stops.

(Std. disclaimer: Kids, don’t try this at home.)

[gjs]

If you found yourself in a tail slide situation wouldn't "down elevator" till horizontal lessen the whip, then up elev.

[Bill Mixon]

gls,
It would depend on several different factors like attitude, power, speed coming back down, etc..

Not sure about the 152's but the 172's have adjustable bolt stops on both the elevator and rudder. the bolts are actually on the fuse/stab and are what the control horns stop against in each direction. So the cables and other control system parts would not be under any stress unless that "stop" section of the airframe failed.

Regardless, airflow going backwards over the surfaces at a high speed isn't good.

Bill