Falling out of a loop

wilkersk

wilkersk

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KennyW
Hoping theres an experienced aerobatic pilot here that will confirm something for me.

I've got a little over 10 hours of dual aerobatic instruction in a Super Decathlon and a Pitts S-2C, and even 1 hour in an Extra 330L.

I've been doing barrel rolls and loops in my little stubby wing, 60hp Sonerai for awhile now. And, I thought I was at least minimally competent with these maneuvers. But today, I twice fell out of the top of a loop and recovered 90 degrees off my heading. Both times, going over the top, I got a little pre-stall buffet and the controls were a little mushy, despite a 140mph entry speed and a solid 3.5g pull.

The only thing I can think of is that I just happened to be going downwind with about a 10 knot quartering tail wind. Most of my other days days doing loops in the Sonerai, there had been very little wind, if any.

Does this sound right? Or, am I screwing something else up?
 
Wind is irrelevant once you leave the runway, you’re in the mass of air moving along with it. More importantly, your airspeed indicator is telling you your speed relative to that mass of air, it has no idea what that air is doing relative to the ground.

As for falling out of a loop, I’d make an amateur guess that you’re doing an accelerated stall. You do know you can stall at any speed, right?
 
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I suggest that you get further advice from the person who instructed you in the Super D, much more effective than typing words here.
 
FWIW, back when I took some aerobatics lessons, my instructor told me to ease up on back pressure, (ie, move the stick forward some) as you approach the top of the loop, as you go through, and for the first small part back down, then start to pull the stick back again and increase back pressure. His reasoning was gravity assists in the loop at the top and you don't need as aggressive of a pull. If you thing about it, you are also slowest at the top of the loop and closest to stall as well.

Of course, this was years ago, I haven't done aerobatics since, and I didn't even sleep in a Holiday Inn Express last night. So...
 
Bill Jennings said:
FWIW, back when I took some aerobatics lessons, my instructor told me to ease up on back pressure, (ie, move the stick forward some) as you approach the top of the loop, as you go through, and for the first small part back down, then start to pull the stick back again and increase back pressure. His reasoning was gravity assists in the loop at the top and you don't need as aggressive of a pull. If you thing about it, you are also slowest at the top of the loop and closest to stall as well.

Of course, this was years ago, I haven't done aerobatics since, and I didn't even sleep in a Holiday Inn Express last night. So...
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Yep, that's the ticket.
 
1) Wind would have zero effect*.

2) If I’m remembering correctly, too much pull can actually cause problems, due to excessive induced drag during the pull phase. Maybe try a little less pull (3g?) and see if that helps or hurts.

3) And Bill Jennings is right, the amount of pull needs to markedly decrease as the loop progresses toward the apex.

*Maybe I should add this to my “Stick and Rudder Moments” thread! And I see Salty jumped on that right away.
 
Maybe not coordinated over the top? I don’t do loops in the Glasair because I busted out of the top one time and was at least 90 degrees off. Think I just got too slow and either the torque of the engine or I had rudder applied subconsciously. Scared the bejesus out of me and haven’t done one since. Only rolls now. :)
 
I could be totally off in saying this, but I do seem to recall when I did some basic acro in the Super Decathlon, that the stick wouldn’t get pulled full aft until we were at the top of the loop and near inverted.

Fun times... combine basic acro with spin training and it was better than going to six flags!
 
Ryanb said:
I could be totally off in saying this, but I do seem to recall when I did some basic acro in the Super Decathlon, that the stick wouldn’t get pulled full aft until we were at the top of the loop and near inverted.
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Not sure if you actually mean full aft (as in on the stop) stick, but there is never a reason to pull the stick full aft on top of a loop. This is bad technique. You unload to near zero G over the top, you don't pull full aft. If you're flying a plane with a carb, you keep just enough load on the airplane to keep the engine from sputtering.

"Falling out" on top is an energy management issue. There are too many variables to say exactly what you are doing wrong without seeing you fly. You may need a little more G load than 3.5 on the initial pull. You may be pulling too hard after going through vertical, which scrubs excessive speed. You may be pulling too hard and stalling on top in trying to get the nose to keep pitching through. Or a combination of the above.

That being said, beginner loop mistakes are not pulling hard enough in the first quarter of the figure on entry, and not unloading and floating enough approaching the top. Newbies also tend to try to start pulling too hard too soon on the backside as the nose starts to pitch back toward the ground.
 
RoscoeT said:
Not sure if you actually mean full aft (as in on the stop) stick, but there is never a reason to pull the stick full aft on top of a loop. This is bad technique. You unload to near zero G over the top, you don't pull full aft. If you're flying a plane with a carb, you keep just enough load on the airplane to keep the engine from sputtering.
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I was mentally composing the same thought to post.

Neither of the Citabrias I taught in had inverted systems. You’d get very light in the seat at the top, but could manage to keep the engine running with slight positive g’s.

The only reason to have the stick back at the top is if you were performing a snap roll at the top.
 
It's not wind, it is just energy management. My guess is not pulling hard enough during the first 1/4 of the loop. Be smooth, but build the G rapidly. 4G is not a bad number to aim for, because you will probably not quite get there. That is the usual cause. Maybe a little too much pull at the top too.
 
RoscoeT said:
Not sure if you actually mean full aft (as in on the stop) stick, but there is never a reason to pull the stick full aft on top of a loop. This is bad technique.
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Like I say, I may just be day dreaming, but I thought that is what we did.
FastEddieB said:
Neither of the Citabrias I taught in had inverted systems.
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Not sure any of them do, but the 8KCAB does.
 
Ryanb said:
Not sure any of them do, but the 8KCAB does.
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7KCAB Citabria is a rare version w/ inverted systems. 8KCAB is a Decathlon and all have inverted systems.
 
Ryanb said:
Like I say, I may just be day dreaming, but I thought that is what we did.
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There are only two aerobatic maneuvers where full aft stick should be used - spins and tailslides.
 
Pulling full aft at the top of the loop (and adding rudder) is a great way to start an "avalanche", but absolutely not appropriate for a loop.

To Kenny, the OP, I have to echo the comments above:
1: wind is irrelevant. This is fairly fundamendal, and I encourage you to do your due diligence and read up on this if you don't believe us.
2: at the top of the loop, in a fairly undepowered aircraft like yours, the cg of the aircraft should be doing the work of pulling the nose down, not the elevator.
3: low speed at the top of the loop is indicative of too much altitude gained (remember aerobatic pilots are constantly trading between kinetic and potential energy). So if you have insufficient kinetic energy, and your induced drag in the entry was moderate (as inferred by your g-meter), then there can be only one conclusion: too much altitude was gained.

How would I fix it?
1: smoothly apply, and maintain, a harder pull in the lower 1/3 of the loop than you have previously been doing.
2: reduce the g-force as you climb, with the aim of experiencing zero g as you float over the top 1/3 of the loop.
3: gradually load the g back up as you descend on the backside of the loop, with the aim of having the same g in the bottom 1/3 of the backside of the loop, as you had during the entry.
4: As you reach level pitch attitude, smartly relax the backpressure and maintain level flight.
5: After a couple of seconds of maintaining level flight, you can either enter another maneuver, or establish a climb to regain some altitude.

I think talking to your 8kcab instructor is a great idea. I would suggest he/she ride along with you as you do the loops, but with 60hp....

Matt
 
MattC said:
Pulling full aft at the top of the loop (and adding rudder) is a great way to start an "avalanche", but absolutely not appropriate for a loop.
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Good 1st post, welcome to POA. Just wanted to note that even for snap rolls on top of a loop (avalanche), full aft stick produces a terrible, slow rotating, energy killing snap. Like any other snap, you don't want to pull full aft, but just enough to get a wing to stall before unloading (ASAP) the elevator to accelerate the snap.
 
Roscoe,

Thanks, and I completely agree!

Matt
 
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