Falling out

[BoostedNihilist]

How dangerous is stalling out of a loop at the top?

[fougapilot]

Ahhh, the good old "loop-spin".

Along with the "hammer-spin" and the "immel-spin, the "loop-spin" is nothing to write home about (at least in most aerobatic trainers. Can't say about the Pits, Extras or Sukois of the world). When the airpane runs out of energy, it will simply fall and if the ball is not perfectly centered, it might got into a spin. Now, don't misunderstand the fact that you fall into a spin "with your head upside down at the top of a loop" with an inverted spin (notice I avoid using the term flying inverted... there is a world of difference between flying with your head upside down and flying inverted). Falling out of the top of a loop while flying with your head upside down should result in an normal upright spin. The entry might look a bit funky, but it's an upright spin non the less.

To do an inverted spin, one must stall the airplane while flying inverted (inverted flight only begins when you reach -1G).

Hope this helps,

F

[Hedley]

Falling out of a loop requires some serious screwing up.

You are far more likely, as Dan points out, to spin out
of a botched hammerhead (stall turn) or immelman.

A Pitts is a easy to enter and exit a spin, especially
inverted. You can wind it up, but if you recognize
the onset of the spin early, you can apply corrective
inputs before you allow the spin to fully develop,
and with minimal loss of altitude.

Technical interlude:

If you fly a "big" loop (ie don't use much G during
the initial pull) your airspeed will be lower over the
top. This is no big deal. I frequently do both inside
and outside loops with the airspeed indicator showing
zero at the top of the loop, for my own amusement.

When I have zero airspeed, I also have zero angle
of attack, because I am not asking the wing to
generate any lift (ie pull and G). If you try to, you
will surely stall, which is mostly a pissoff because
of the increased drag you will incur at the high AOA.

At zero airspeed over the top of a loop, you are
ballistic - like a baseball that is at the top of it's
apogee. Just relax, look outside, and enjoy
the ride. Wait for the airspeed to build, before
you pull any G.

This is a very very very important lesson for a
beginner aerobatic pilot to learn - speed and G
are intimately related. How much G you can
pull is limited by how much speed you have.

Frankly, you should know the formula, but that
is my technical bias showing.

Another important lesson for an aerobatic pilot
is that pitch attitude is no longer a reasonable
proxy for angle of attack.

And every aerobatic pilot should know that angle
of attack is King - he should be able to draw the
Cl and Cd curves for his wings on a blackboard.

But again, perhaps that is my engineering background
showing.

[sugarfree]

Another important lesson for an aerobatic pilot
is that pitch attitude is no longer a reasonable
proxy for angle of attack.

It never was..

[Hedley]

You might be surprised how many experienced pilots
believe that if an aircraft is straight and level, it's
AOA is low (false)

You would also be surprised how many experienced
pilots believe that if an aircraft is vertical (up or down)
it's AOA is high (false).

When teaching aerobatics, this is a VERY important
lesson to cover.

Similarly with airspeed. I might be at a very low airspeed
in flight (eg zero, or even negative) and have a low AOA
(unstalled).

And, I might be at a very high airspeed and have a very
high AOA (stalled).

And contrary to popular belief, many aircraft are perfectly
flyable at very high AOA (in excess of stalling AOA).

It's amazing how few pilots could actually draw the
Cl and Cd curves for their aircraft's wings.

[Blue Side Down]

And contrary to popular belief, many aircraft are perfectly
flyable at very high AOA (in excess of stalling AOA).

It may be equally surprising to realize that the lift provided by a wing in a straight and level stalled condition is equal to that which is provided in normal straight and level flight (save the brief moment when the airflow transitions from the flying to the stalled condition).

[sugarfree]

It may be equally surprising to realize that the lift provided by a wing in a straight and level stalled condition is equal to that which is provided in normal straight and level flight (save the brief moment when the airflow transitions from the flying to the stalled condition).

Not sure what you mean here.. Care to elaborate??

Thanks

SF./

[sugarfree]

You might be surprised how many experienced pilots
believe that if an aircraft is straight and level, it's
AOA is low (false)

You would also be surprised how many experienced
pilots believe that if an aircraft is vertical (up or down)
it's AOA is high (false).

Actually no I am not, I find it quite frightning ... Its basics, I still believe that the book "Stick & Rudder" should be part of the study curiculum instead of the fly by numbers scenario...

Sorry for hijacking

SF/..

[Blue Side Down]

It may be equally surprising to realize that the lift provided by a wing in a straight and level stalled condition is equal to that which is provided in normal straight and level flight (save the brief moment when the airflow transitions from the flying to the stalled condition).

Not sure what you mean here.. Care to elaborate??

Thanks

SF./

The generally accepted theory is that when a wing stalls it 'looses lift', and a loss of altitude results because the wing is no longer 'lifting' enough to support the airframe. This is true for an instant, but only for an instant. The statement is misleading if used to explain the ensuing continual constant descent. In reality, the wing undergoes a momentary variation in total lift force right at the moment the stall breaks, whereafter the total lift force provided by the wing is again equal to that which it was before the stall (curiously happening to be equal to the weight of the plane). You hold it in the stall for as long as you want, and the lift on the wing will be the same as it would be if you were flying straight and level. The drag, on the other hand, would be significantly higher, hence the constant descent.

[Hedley]

Back on topic ... falling out of the top of a loop ...
I should mention:

If you fly the loop correctly in that you float over
the top inverted, with zero degrees AOA, the
wings will not stall.

However. What can happen if your airspeed
gets too slow over the top of the loop, is
that the prop starts to hurt you. Slipstream
coils up, so you better get on the right rudder.
Ailerons lose effectivness, so you start to
torque.

If not corrected for, the ill effect of the prop
can cause you to yaw/torque off the top
off the top of the loop, and "fall out".

How to cure this? Well, often, at slow
speeds, the best thing to do, to maintain
control of the aircraft, is to reduce power.

For example, during a hammerhead. As
soon as you kick the rudder, and nudge
the nose off top dead center, back the
power off. Get rid of the bad things that
the prop does to you at slow speeds,
and let gravity pull the nose down.

This technique above results in a much
smaller radius of pivot, too, than leaving
the power on - the thrust pulls the aircraft
out, after all.

It seems unnatural to be backing the power
off when the airspeed is low, but often,
that's the easiest and best thing to do. You
are ballistic, just unload, enjoy the view, and
let the gravity do it's thing, and let some
airspeed build before you get the power
back on again.

[mashowski]

How dangerous is stalling out of a loop at the top?

Either it is very dangerous or it is not dangerous.
The answer depends on the pilot, I have never stalled, spun, or fallen out of a loop, but if I did I could recover easily.
The catch-22 here is that a pilot that fails to recognize the impending stall-spin will also have difficulty recovering. That is why aerobatics are practised at a safe altitude so that a delayed recovery will not end up as a fatal case of dirt poisoning.
If you fly with an experienced aerobatic pilot (preferably one with an aerobatic instructor rating) it is not dangerous because he/she can see it coming a mile away.
Mash

[Hedley]

inverted spin

I doubt there is a Pitts pilot alive who has never
fallen out of a botched vanilla hammerhead, into
an inverted spin. You get just a little negative,
the left rudder does the rest

The good news is that inverted spins are pussycats,
unless you do something dreadful with the stick
to accelerate it.

Power off, opposite rudder, and it stops immediately.

I would rather be an inverted spin, than an upright
spin, any day. See, the airplane has no eyeballs,
and does not get frightened when it is upside down.

In fact, when it is upside down, the rudder is in clean
air - it is not blanketed NEARLY as much by the horizontal
stabilizer and the elevator, as it is in an upright spin.

I frequently enter and exit inverted spins below 1,000
AGL. Yawn.

[Adam Oke]

inverted spin

I frequently enter and exit inverted spins below 1,000
AGL. Yawn.

That just reminded me of this AT-802 Video that spun in after a water drop. Not a loop ... but appears to be a botched hammerhead like you guys were discussing.

[mashowski]

BoostedNihilist, the reason that I have never fallen out of a loop or hammerhead is because I did a lot of spin practise prior to doing aerobatics. I became familiar with my airplane. I did power on accelerated spin entries from different attitudes so that I could recognize them before it developed. A couple of times I have come close to a snap roll at the top of an Immelman. I have taken pilots who have never done aerobatics before for a ride in my Super Decathlon and let them do a loop, a few of them came close to stalling at the top but it was no big deal. It is actually kind of fun when they screw up because you can see it coming a mile away.
I hope that I get to meet EngineGuy and become friends some day. There is an aerobatic club Christmas party in Calgary on November 29th, pilots with an interest in aerobatics are welcome, go here for details: http://www.patspencer.ca/aerobaticscanada/joomla/
If there are any pilots out there that want to go for a ride in the SuperD I will be happy to oblige, too. It is hangared at YBW.
Mash

[Hedley]

I have never fallen out of a loop or hammerhead

yet ... (heh heh heh)

Clearly, you are a better pilot than I, sir.

And a better pilot than anyone I have ever given
aerobatic instruction to.

And a better pilot than anyone I have ever seen fly,
and I've been to an awful lot of airshows over the decades.

And a better pilot than I have ever heard of, to have never,
ever botched an aerobatic maneuver.

Frankly, such a legendarily natural and gifted pilot such as
yourself is wasting your time on the ground - you should fly
aerobatics full time - or do you do, already?

What aerobatic types have you flown? I presume the list
must be quite lengthy - my ICAS SAC card only has five
types listed on it: Pitts, Stearman, Harvard/T-6, PT-22 Ryan,
and Citabria.

How many types are on your ICAS card? You must be one
of the old-timers on the ICAS website, with 20 or so types,
correct?

[mashowski]

Hedley, I don't have as much aerobatic experience as you, and I'm not being smug or arrogant.
I have a lot of respect for your ability and aerobatic enthusiasm, and I like to read your comments on Avcanada, so why the cheap personal attacks against me?
I just made a simple statement of fact. What is the big deal? A loop is the easiest aerobatic manoeuver to do, but one of the hardest to do well. (that's not from me, I heard somebody else say it)
Chill out, dude.
Mash