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24-turn Spin RV-7. 47-turn Spin RV-8

Also interesting is the prop that doesn't automatically start windmilling once gliding speed is achieved. Looks like it only took a slight dive to get enough additional airspeed to start it moving again, but if you held it at your glide speed it would stay stopped (or maybe flick over slowly as his did).

The annotations on the RV-8 video were useful as well... Looks like ~10000' for 47 turns, or about 4.7 turns per 1000' loss in altitude on average. Recovery was in about 2 turns on the RV-8, as opposed to 5 on the RV-7. Does anyone see why?
 
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Also interesting is the prop that doesn't automatically start windmilling once gliding speed is achieved. Looks like it only took a slight dive to get enough additional airspeed to start it moving again, but if you held it at your glide speed it would stay stopped (or maybe flick over slowly as his did).

The annotations on the RV-8 video were useful as well... Looks like ~10000' for 47 turns, or about 4.7 turns per 1000' loss in altitude on average. Recovery was in about 2 turns on the RV-8, as opposed to 5 on the RV-7. Does anyone see why?


Prop stops while spinning but it doesn't want to stay stopped at best glide speed. I kept it stopped intentionally and to do so I had to fly slowly. I mean about 75 knots top. A bit faster and it starts windmilling. I have fixed prop. May be CS behaves differently. Friend of mine intentionally stopped engine above airport and landed this way. Prop stopped first time already at roll out. He flies 7 taildragger with CS prop.
 
Does anyone see why?

Guess multiple factors. Size of the tail feathers, length of fuselage, pro or con aileron position, CoG, recovery inputs, and many more...

Thanks for the links Tandem :)
 
...
Recovery was in about 2 turns on the RV-8, as opposed to 5 on the RV-7. Does anyone see why?

On th -7 the elevator remained slightly up or neutral for about 3 turns after opposite rudder was applied. Once elevator was deflected downward, the recovery was fairly quick.

Skylor
 
Spin

It is very important that full opposite rudder be applied followed immediately with elevator at least slightly down or significantly down as required by the individual airplane. I thought the 7 might have had a bit of out spin aileron but can not tell for sure due to the viewing angle. In high performance aerobatic airplanes recovery from a fully developed upright flat spin is almost immediate if one simply applies opposite rudder and simultaneously puts the stick in the opposite corner. Full power throughout. In the Pitts S2B and many of the monoplanes the spin stops in about 1/8 turn. I have no spin experience. In RV but would absolutely not recommend this technique in RV. The failure to apply proper elevator control and neutral aileron is typical of spin recovery mistakes. Many years ago two very experienced pilots spun a Pitts S2A into the ground. Intentional power off upright spin, would not recover because the stick was not far enough forward. Just before impact full power was applied, the spin flattened out. They both walked away.
 
When the RV-7 kit came out around 2001-2002, Van had a test pilot do a flight test program. Before that Van did all the testing of previous models. I flew with Van once, he is a good stick. I caught one of his aerobatic routines at Arlington Airshow once. The result of RV-7 spin testing was RUDDER was increased in size. I recall recovery was 4-5 turns to recover with the original smaller rudder. It recovered but took too many turns. This is some back issues of RVator.

The original first RV-7 empennage kits Van sold had smaller rudder. Van later sent out the larger rudder to the original kit buyers who asked for it free of charge. I am sure some folks stuck with the original rudder. It is not that it would not recover just it took longer. The RV-8 came out after the RV-7 and all RV-8 kits came with the wider rudder.

I can't tell if the this Red RV-7 has original smaller rudder. I took screen shots of both RV-7 and RV-8 from video and scaled them. It is hard to tell if a rudder chord is a a few inches wider with this method, but it looks like the RV-7 rudder might have less chord than the RV-8 rudder.


PS the Piper Tomahawk I once had a partnership in was certified in utility category and approved for spins. I spun it a few times but only a three turns. It had a reputation of winding up and getting faster and steeper
https://www.youtube.com/watch?v=xzFgqtPVCZ0
 
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The RV-8 has a different rudder altogether. The RV-8 rudder is smaller than the RV-7/-9 rudder and has thicker skins (0.020" vs 0.016").

Below is a pic of an RV-8 rudder (on the left) next to an RV-7/-9 rudder (on the right)

Carl, I believe the 8 rudder (.020" skin folded TE) is the same as the final .020" skin 6 and the originally shipped 7 rudder.

If there is a dimension you believe is different between the 7 (short/original) a and 8 please post it and I will measure against mine hanging in the basement.
 
Rudder

Carl, I believe the 8 rudder (.020" skin folded TE) is the same as the final .020" skin 6 and the originally shipped 7 rudder.

If there is a dimension you believe is different between the 7 (short/original) a and 8 please post it and I will measure against mine hanging in the basement.

This is what I've always thought was the case as well. The -7 in the video appears to have the "early" rudder, based on the size and shape of the counterbalance.

EDIT: After seeing Marabou's later reply and watching the RV-7 video again, it's clear that this has the large (tall) counter-balance of the large -7 (AKA RV-9) rudder.

Skylor
 
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The -7 in the video appears to have the "early" rudder

Red 7 in the video has new bigger rudder. Empennage had been bought in 2009 and it has riveted trailing edge.
 
All RVs will recover simply by releasing the stick. A faster recovery will be achieved by applying limited anti-spin controls - opposite rudder, slightly forward stick. The fastest recovery will be achieved by applying maximum anti-spin controls - full opposite rudder, full forward and full into spin direction aileron. The reason those recovery controls aren't advocated is because pilots too often SCREW THEM UP, exacerbating the spin and delaying the recovery. If recovery isn't occurring, it's probably the pilot. Release the controls and wait.

One of the first steps in any spin recovery should be reducing power to idle. In my experience, power on will flatten the spin (sometimes desirable for aerobatic contest) but also slow recovery.
 
All RVs will recover simply by releasing the stick.

True if you just entered the spin. First turn is very slow and releasing the stick causes almost immediate recovery. It may help if you unintentionally entered spin and remaining altitude does not allow to pick up textbook hidden somewhere you don't remember where. Just drop stick and pedals and you are fine. Actually I have no idea how to cause spin in RV unintentionally. It just drops the nose and flies. This plane had been designed with safety in mind rather than aerobatics.

Second turn is much faster and then spin establishes and there is no difference between third and thirty third turn. I tried to release the stick being in established spin. I had plenty of altitude and felt safe but the plane did not even try to recover until I lost patience and forced it to recover. If you look at recovery in slow motion you will see that delay with recovery is actually not a delay. After first recovery inputs the plane very gradually lowers the nose while still turning. And just when nose is down enough and there is enough forward movement to increase rudder authority comes the recovery. It is not a science, it is just how I see it.
 
Remind me never to do that!

I wonder from what AGL they started? I did an hour of training and we typically stopped it at 2.5 turns, which was plenty for me. It is amazing how fast you are dropping/losing altitude, like a rock:eek:
 
Video

If you look carefully at the spin recovery in the 8 you can see a very momentary application of down elevator. The elevator is quickly returned to neutral. The autorotation stops immediately with the application of down elevator. The 7 uses only neutral elevator which delays the"P recovery. I am now convinced that the 7 pilot used at least some out spin aileron which slows the recovery. The 7 spin also appears to be slightly flat which could be caused by out spin aileron. Idle power does not enhance spin recovery. The problem with full power spin recovery is the relatively high risk of making a simple error which prevents recovery. I learned the full power recovery from a student who was using it for spin in Sportsman competition. Normal power off entry, at about 1/4 turn aggressive forward stick and full power. 1/8 to 1/4 turn lead full opposite rudder and simultaneous neutral stick, as soon as rotation stops neutral stick. In the S2B this puts the airplane very close to a vertical down line. Again I strongly recommend against trying this in an RV. It is just too easy to screw up.
 
Some of the above is not correct.
Carl I was one of the early builders to buy a full RV7 kit and have serial number to prove it. :D This is my rusty memory. I got the notification to upgrade rudder just as I was finishing the original rudder design. This was before that Service Letter, just a notice. So I built two rudders. My main point, a good number of early RV-7 Kits were sold with small rudders and could still be flying with original smaller rudder. The change was due to spin recovery.

You are saying this was driven by the RV-9? OK. The RV-8 and RV-9 did come out before the RV-7 not after, and RV-8 rudder is smaller. Thanks for clearing that up.

Using my forensic video analysis the RV-7 and RV-8 rudders in video look to be about the same size. So this RV-7 may be the small rudder. From the SB 2-6-1 the smaller rudder worked but could not recover to aerobatic standards from 6 turn spin, recovering in 1.25 turns. The SB also states the larger rudder brought the RV-7 to as good or better recovery as other RV's.

The point made earlier the video of the RV-7 shows elevator being neutral in recovery, not nose down. This may have delayed recovery.

FYI the original RV-7 rudder had a folded trailing edge like RV-4 and RV-6. The newer one is like RV-9 with riveted TE.
 
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My post (#8) pretty well explains where we differ, and the embedded link in post #8 to Van's SB (June 2002) describes why Van's replaced the original RV-7 rudder with the RV-9 rudder, i.e., due to better spin recovery characteristics.

Nope, never said that.... [snip - deconstruction of my post line by line ha ha]
Carl relax. There is no argument here. I never said you said. I read Van's Service Bulletin and even paraphrased it in my post, thanks for pointing it out to me. I read aircraft SB's for a living. I agree and appreciate your input. No worries. What I am saying, I experienced the RV-7 small to larger rudder change real time in 2002-2003 time frame, and.... getting back to OP Video reference and the 4 turn RV-7 spin recovery: :eek:

1) It appears like it had smaller rudder (my opinion)
2) The elevator was neutral during recovery.*

* Van recommends neutral elevator for spin recovery. However pointed out by other post the RV-8 video shows pilot pumped momentary nose down elevator during initial spin recovery. Elevator from my spin recovery experience in different planes, can and does make a difference. Usually to recover from a spin once rotation stops, is like stall recovery. Most stall recoveries for most planes involves some nose down elevator (followed by taking it out quickly but not too quickly to cause secondary stall). I suspect Van doesn't recommend nose down elevator because it's not needed, and there is a chance of over controlling and extreme nose down attitude. Same with aileron input for stall/spin recovery. Neutral is often recommend to avoid adverse yaw and stalling the wing (due to increased camber). However Van's RV's have Frise ailerons. Often recommended pilot techniques are based on KISS, keeping it simple stupid.

Bottom line to the RV-7 rudder size, the small one is sufficient but for recreational aerobatics and has enough authority for one turn spin recovery from a one turn spin, to meet non-aerobatic standards. However if you want to do intentional 6 turn spins you should have the larger rudder of you want to get close to recovery more in line with what the RV-8 does in the video. (This is basically from the SB that Carl pointed out.)

Carl thanks for the information, corrections, reiterating. I acknowledged that the RV-8 and RV-9 came out before the RV-7. Got it. The history of RV development is interesting. I learned a few things, especially about RV-8 and RV-9's I didn't know. Good info. Thanks. Cheers
 
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