Elevator use during spin recovery

So far the spin recovery technique I have used in my RV-8 has been the following.
1. Throttle: Idle,
2. Aileron: Neutral,
3. Rudder: Full opposite the direction of spin,
4. Elevator: After full opposite rudder is applied, progressively forward until spin stops.

I had an interesting and protracted recovery today from the middle of the aerobatic cg envelope and I was wondering what other folks are doing with the elevator. I am particularly interested in the sequence of application and the size of application of elevator inputs.

Cheers

Nige

What exactly happened with this "interesting and protracted" recovery? Did it accelerate unexpectedly, or did recovery simply take longer than normal? Maybe the resident RV-8 pilots can comment, since I've only spun the RV-3 and RV-6 (w/ -7 tail). Both recovered perfectly normally from fully developed spins, which is to say 'PARE' (the 4 steps you list above) worked as expected. The RV-3 would recover with opposite rudder only, even with the stick held fully aft. I can't imagine a properly rigged and loaded RV-8 would require anything special with the elevator during recovery, besides moving it to around the neutral position after you have applied full opposite rudder. You should test this in your own airplane, but I'd also expect RVs to recovery using the neutral control emergency recovery technique, which works in most aerobatic aircraft with effective controls. This involves pulling power off, and moving the rudder, ailerons, and elevator to center, and waiting for airspeed to buildup (recovery) before pulling out of the dive.

I guess these planes are all similar but at the same time individual, so the following is right for mine but may not be at all true of yours.

Doing an investigation of the spin characteristics of my RV-8 I started with forward cg and worked up from 1 second input, 1/2 turn, 1 turn, 2 turn, 3 turn, 4 turn, 5 turn and finally 6 turns spins left and right. For spins up to 3 turns I also looked at aileron with and against. From there I worked aft in cg to the middle of the aerobatic envelope. What I have found thus far is the following:

1. It spins at just under 2 seconds per turn, averages about 1.8 seconds per turn.
2. Height loss per turn is consistent for all turns after the first at about 250' per turn.
3. Rate of descent builds steadily for the first three turns where it stabilizes at -7500 fpm.
4. Airspeed builds from 60 knots at entry to about 85 knots in the first turn and a half and then steadily falls back to 70 knots by the end of the third turn where it remains constant.
4. The AoA (Dynon skyview) varies between 85 & 100% for the first 2 turns after which it is pegged at maximum until recovery.
5. The first turn and a half are quite steep and oscillatory in roll and to a lesser degree in pitch, but not violent by any stretch.
6. Right at three turns the nose starts to slowly pitch up, roll and pitch oscillations begin to subside. The nose continues to steadily rise until turn 6.
7. It takes a full 6 turns for the spin to fully develop, that is if your definition of fully developed is that each turn is the same as the last.
8. By turn 6 the nose is only about 20 degrees below the horizon the turn rate is still ~180 deg/sec, it is very smooth with no roll & only minimal pitch oscillations.
9. Addition of in spin aileron after 1 turn makes the spin more oscillatory in roll and pitch.
10. Addition of out spin aileron after 1 turn makes the spin flatten quicker and delays recovery by about an extra 1/2 turn (when the recovery is affected at after 3 turns).
11. Recovery prior to turn 4 with power idle, aileron neutral, rudder fully opposite then stick forward results in recovery between 3/4 turn and 1 1/2 turns depending on turn direction (generally a little slower recovering from left spins).
12. Recovery once the spin has significantly flattened can be quite protracted. In a 6 turn spin to the right at mid cg it took me 5 1/2 turns of consistently held recovery inputs to recover, which tested my patience significantly. Following anti spin rudder the nose dropped about 10 degrees but then stayed there for the next 2 1/2 turns before slowly dropping until the AoA finally broke at 5 1/2 turns (for a total of 11 1/2 turns). The turn rate did not change until the turn prior to recovery when it increased slightly. Total height loss for the 11 1/2 turns and subsequent dive recovery was only 3200'. I'd started at 11,500' AGL so I still had 8,300' AGL remaining. It was the general lack of response to control inputs rather than height remaining that made it an uncomfortable experience.

So going forward I think:
1. I won't intentionally spin past 3 turns.
2. I'll immediately commence recovery if I detect the spin starting to flatten regardless of the number of turns.
3. Future spin investigation will be on optimizing sequence and rate of inputs to minimize recovery time/rotations after 1 or 2 turns, which seems to be the most likely scenario for an unintentional spin following botched aeros.
4. While the aircraft is not a unpleasant to spin, the oscillatory nature of the first 3 turns means it isn't fun to spin in the same way it is fun to loop or roll the aircraft. For this reason I probably won't do them every flight and will need to ensure I deliberately practice from time to time to stay familiar.
5. I won't intentionally spin the aircraft with a passenger.
6. The cost of the parachute and helmet I was wearing at the time seemed like very good value for money.
7. I'll start intentional spin practice as high as practicable. The aircraft climbs fast so its really no burden to go higher.

Hope this helps someone else having a misadventure.

Cheers

Nige

Out of curiosity, has anyone tied Beggs Muller recovery in an RV7 or RV8

I was practicing this in a Robin the other day and found that the stick stays in my crotch with full opposite rudder until the spin breaks and then the stick comes forward automatically ?

Cheers

Nigel, very detailed and interesting report. This thread has been unexpectedly quiet. The behavior of your airplane is outside my experience with RVs. I've also never heard anyone else report such a delayed spin recovery in an RV - especially the -8. I credit you for staying with it for so long, as most pilots would have been prepping for a bailout before hitting 5 extra unrecovered rotations.

Did you try adding in-spin aileron (same direction as spin) during any of those fully developed flattened spins? That is the traditional way to aid the recovery of flattened spins in most aerobatic airplanes. Of course, it seems continued exploration of this area would further put you in test pilot territory. I wouldn't blame you for limiting spin rotations from here on out. Not much reason to do this besides testing the aircraft's spin characteristics. You've already done that much more extensively than 99% of RV pilots.

eddieseve said:

I was practicing this in a Robin the other day and found that the stick stays in my crotch with full opposite rudder until the spin breaks and then the stick comes forward automatically?

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Yes, that is normal for Beggs-Muller spin recovery.

Hi Nigel,

Thanks for a very detailed report. I have done quite a bit of experimentation with RV-8 spins as well and find our results to be quite similar with two notable exceptions.

1. I have found that centrifugal forces sling the fuel to the outer ends of the fuel tanks and, depending on total fuel on board the engine will quit after 5 or 6 turns. Upon recovery the engine recovers easily.

2. I never had a recovery last longer than about one and a half turns even in a fully developed spin. This may be due to my recovery technique which differs from yours in that I rapidly apply forward stick (slightly forward of neutral) at the same time I apply full rudder opposite the spin.

It is worth noting that the RV is easily recoverable from spins of 2 or 3 turns and there is no requirement in competition aerobatics to turn more than 2 turns. Your measured approach to spin testing is admirable. Well done!

One thing I was concerned about was the engine quitting (my engine has high compression and a light prop so I was not convinced that it would windmill and start easy) so I did the spins with full fuel at start and always selected the inboard tank. In hindsight having full fuel probably exacerbated the spin, the flip side being the engine did not stop. One thing I did to reduce the consequences of an engine failure was to do the spins half way between to local airports so it didn't matter which way I was pointing on recovery it would not be far to turn to get to either one.

In spin aileron was next on the agenda, then I was going to try keeping the rudder fully deflected but going back to the aft stop and being more violent with putting the stick forward.

nigelspeedy said:

In spin aileron was next on the agenda, then I was going to try keeping the rudder fully deflected but going back to the aft stop and being more violent with putting the stick forward.

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What about the use of power as well? Due to propwash over the rudder, most aerobatic airplanes also recover intentionally flattened spins more quickly with power on than off. You say you have a light prop. This means additional flattening (when spinning left) due to gyroscopic precession would be very slight. Explore the use of power incrementally and carefully. Power on requires your other inputs to be correct, or it could make things worse. Power on is NOT part of normal 'PARE' or any sort of emergency spin recovery technique, nor should it be. Power should always be removed if control is lost...unless nothing else is working. This is important to understand. But the reality is that when practiced under control to known outcomes, it can be used to extract additional spin recovery performance from many aerobatic airplanes. I use it in the Pitts. Can't confirm any of this with the RV, though.

Spins

No RV spin experience but I can almost guarantee that full inspin aileron will enhance the recovery from upright flat spin. Inverted flat spins recover quicker in most aerobatic airplanes with conventional horizontal tail placement. That is because the vertical tail is operating in much "cleaner " air when spinning inverted.
spinning only 20 degrees nose low is quite unusual unless the spin is intentionally flattened with full outspin aileron and full or nearly full power.

nigelspeedy said:

One thing I was concerned about was the engine quitting (my engine has high compression and a light prop so I was not convinced that it would windmill and start easy) so I did the spins with full fuel at start and always selected the inboard tank. In hindsight having full fuel probably exacerbated the spin, the flip side being the engine did not stop. One thing I did to reduce the consequences of an engine failure was to do the spins half way between to local airports so it didn't matter which way I was pointing on recovery it would not be far to turn to get to either one.

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For what it's worth, protacted spins on less than ~1/3 fuel in the selected tank in my -6A result in the engine quitting after more than five or six rotations. Good call on thinking of this possibility ahead of time.

good timing on thread...

To throw in my amateur (but learning) experience into the discussion…

Just yesterday I flew with Mike Seager, our factory trainer in their RV-7. The flight was for my BFR PLUS spin training. It is nice to learn in a side-by-side.

Mike gave me a quick “ground school” explanation of what we were doing. I did some spin training in the last part of my primary training in a C-152 a few years ago. Mike explained how our neutral stable planes differ from a positive stable plane like the Cessna.
And he went on to say that the Beggs-Muller does not work well with the RVs. They need the control input to right itself, not unlike a banked turn, when compared to how a Cessna type will straighten itself out.

After a few warm up maneuvers we climbed to 5000’ for the spins.

Entry:
Throttle at idle
Landing 3-point pitch attitude
Just before stall apply full back stick, then full rudder
We spun 1.5 to 2 turns, nose down, no aileron input used.

Recovery:
Full opposite rudder
Slight push forward elevator, spin stopped in a about a half a turn.

We did about six or seven spins till I had the procedure down. Then we shot some landings to complete my BFR, and back to the barn

After lunch I hopped right away into my -8 to apply what I learned:

I carry my tiedown/emergency bag in the rear luggage when solo, still about ¾ forward CG.

Same entry, with no perceived difference in entry, but a noticeable degree more of nose down pitch when spinning.

Same recovery, but spin stopped with neutral stick, no down elevator needed. Spins seemed to stop at a half or so turn BUT more nose down than the RV-7 early in the day. It would not have been much at all of a push to establish a vertical down line for a competition spin exit. One pull out was 2.7 Gs. The rest were less.

I might try more weight in the back to feel the difference, but I agree with Nigel, not much good reason to scare a passenger with this maneuver.

All this was new to me, counting the turns and really focusing on the differences will take more time.
My hats off too to Nigel for doing such an extensive job of research, practice, observation and report!

ronschreck said:

2. I never had a recovery last longer than about one and a half turns even in a fully developed spin. This may be due to my recovery technique which differs from yours in that I rapidly apply forward stick (slightly forward of neutral) at the same time I apply full rudder opposite the spin.

!

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You didn't mention where your CG was when you did your spins. In my personal experience ( and I have certainly much much less then you) recovery happens in less the. 1.5 turns too. However, my CG is always close to the front as I fly solo when I do spins.

Oliver

spatsch said:

You didn't mention where your CG was when you did your spins. In my personal experience ( and I have certainly much much less then you) recovery happens in less the. 1.5 turns too. However, my CG is always close to the front as I fly solo when I do spins.

Oliver

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Oliver,

I am always solo when doing spins so my CG is pretty close to the center of the CG envelope depending on how much fuel is on board. If the CG is too far forward it is difficult to enter the spin cleanly.

ronschreck said:

Oliver,

I am always solo when doing spins so my CG is pretty close to the center of the CG envelope depending on how much fuel is on board. If the CG is too far forward it is difficult to enter the spin cleanly.

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I guess my RV-8 is more nose heavy then yours. Solo with full fuel I am at 79.2 30 minute reserve at 79.09 with a acro range of 78.7-85.3 ... and yes.

Oliver

Your spin characteristics are quite similar to those of a Chipmunk. Two or three turns to develop, followed by the spin flattening and stabilizing. Once stable, rudder alone is ineffective in recovery. It requires a significant push to full forward stick (I always aimed to keep my knuckle in contact with the bottom of the panel) after the rudder input, and holding these inputs fully, sometimes for several turns.

Although the Chipmunk and RV-8 have quite different rudder configurations, their aft fuselage and horizontal stabilizer configurations are similar. I was told long ago (can't vouch for its truth) that when the British investigated spinning problems with the Chipmunk they decided that part of the problem was due to the smoothly rounded upper aft fuselage, which tended to delay cross-flow separation and thereby generated significant in-spin aerodynamic forces. As a result, some Chipmunks were fitted with long strakes extending forward from the horizontal stabilizer for a couple of feet, as well as a larger rudder.

I've spun both configurations a long time ago, and I can't remember that I noticed a significant improvement. However, if you're interested a bit of aft-fuselage tufting on the RV-8 might be informative.

Also, I seem to remember that NTPS had a Chipmunk, so maybe you could arrange some comparative testing.

I have accomplished 1000's of spins while practicing competition acro.
The oscillations in pitch during the first few turns are caused by the inertia of the plane, although vertical, continuing across the ground on it's heading that it had during the spin entry. Because of this inertia the nose will be pushed down at every full turn and up at every half turn, until the movement on original heading subsides after a few rotations and the axis of rotation becomes truly vertical.

Rudder is always primary for spin recovery and should be applied first, before you apply forward stick. Abrupt forward stick during recovery can cause a cross over to occur; where the plane immediately and smoothly enters an inverted spin with very little visual difference to a pilot looking straight down at the ground. For that reason I recommend that the push over for breaking the spin be firm but limited to vertical down and never any tucked under a vertical down line. Less than vertical is ok, more is asking for a cross over. watch out for speed build up on recovery and pulling to hard and causing a secondary stall. You are looking for a pull hard enough to keep the speed from building but not so hard as to cause the secondary.

Pro spin "in" aileron will quicken recovery especially from a spin flattened by anti rotation "outside" aileron. Power flattens a spin power off steepens a spin. A power on spin with outside aileron is as flat as can be done. To recover from such a spin you need to: go to idle, apply opposite rudder, then apply in spin aileron and then push the nose down.

I'm learning a heck of a lot from just reading all this. Have never tried spinning my 8, even tho I'm well aware of PARE. Too chicken Got a question for you expert guys. I've not down immelmans for fear of, when I roll it right side up at the top, I might get in an inverted flat spin. No idea how to get out of one of those. Instead, I just pull the nose thru and do a cuban 8. Those are easy peasy.

I guess also, one can get in an inverted regular spin or inverted flat spin if one buggles a hammerhead??

Can you guys talk about that too?

donaziza said:

I'm learning a heck of a lot from just reading all this. Have never tried spinning my 8, even tho I'm well aware of PARE. Too chicken Got a question for you expert guys. I've not down immelmans for fear of, when I roll it right side up at the top, I might get in an inverted flat spin. No idea how to get out of one of those. Instead, I just pull the nose thru and do a cuban 8. Those are easy peasy.

I guess also, one can get in an inverted regular spin or inverted flat spin if one buggles a hammerhead??

Can you guys talk about that too?

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Don,

First, let's talk about proper aerobatic instruction. You don't learn aerobatics from a forum or a book. You get instruction from a qualified aerobatic instructor and the first thing you will learn is proper spin and unusual attitude recovery techniques. Not until you are comfortable knowing that you can safely recover from spins and unusual attitudes 100% of the time should you even consider trying your hand at aerobatics. It's when those "easy peasy" maneuvers go wrong that proper aerobatic training pays off. Get some, please! Then we'll talk about the immelmann.

ronschreck said:

Don,

First, let's talk about proper aerobatic instruction. You don't learn aerobatics from a forum or a book. You get instruction from a qualified aerobatic instructor and the first thing you will learn is proper spin and unusual attitude recovery techniques. Not until you are comfortable knowing that you can safely recover from spins and unusual attitudes 100% of the time should you even consider trying your hand at aerobatics. It's when those "easy peasy" maneuvers go wrong that proper aerobatic training pays off. Get some, please! Then we'll talk about the immelmann.

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OK, Ron, Will do.

Spins

Just an additional experience - in a Pitts. The first time I took a really heavy (220 pound) passenger up in the S-2A, I got into an inverted spin following the 1/2 roll off the top. Fortunately I had had a good deal of instruction in recovery and recovery was not a problem. I do think a botched recovery from a low-speed Immelmann can lead to an inverted spin.

Spins

The most common inadvertent spin in the Pitts S2B at the Sportsman level is an upright flat spin from an immelman. It goes like this:
hazy day, not a good horizon, trainee gets a bit lost, starts the roll with the nose very high, now has lost most visual reference, slams the stick to the left, too much top rudder, now the roll does not want to stop, full right stick, still a lot of left rudder, nose still very high, and presto, the immelspin.
Spins from a botched hammerhead can be either upright or inverted. Spins from a hammerhead are a very distant second place to spins from an immelman.
In the Pitts 99% of the time the airplane will not spin if you neutralize the rudder and VERY GENTLY push or pull to the closest horizon. I flew the Pitts over 1000 hours without ever inadvertently spinning the airplane. I did tumble a few times trying to learn outside snaps on climbing lines but recovered before spinning.
GET SOME INSTRUCTION

Most pilots new to acro tend to give inverted spins special status when it comes to apprehension and concern about accidental entries. As mentioned multiple times above, proper training is very important. With this, you will learn that it generally makes no difference exactly how the loss of control occurs - you will learn to recover ALL modes equally well. Actual spins take a few seconds to develop after losing control (assuming the pilot continues to hold pro spin inputs), and good training will program the brain to recover loss of control as soon as it happens, and avoid an actual spin. In practice it's actually quite easy. You just need to learn to immediately recognize when the airplane has departed controlled flight and take some very simple measured actions - which in most aerobatic airplanes is to simply pull power off and neutralize (move to center) all three controls. But the exact recovery inputs needed should be tested in each new aircraft type.

And just like basic aileron rolls, all this sounds very simple, but pilots should NOT attempt to self teach given the possibility of reacting incorrectly after the eyes see and the body feels things it doesn't understand. 'Braindeath' is real.