In-spin aileron

[Diana]

Well, I've been researching this for the past day, and have found lots of confusing information about the effect of in-spin aileron during a spin. Evidently it is airplane specific? I'm asking this in regard to the effect of the aileron in a spin, not necessarily the recovery.

 

[tonycondon]

i believe ryan ferguson on the red board once did some experimenting with in spin aileron in a citabria or something similar. he found that eventually it did stop the spin, but took several turns, IIRC. i dont know why the effect would be airplane specific. In spin would lessen the intensity (lower AOA on down wing) and anti spin would make it wrap tighter (higher AOA on down wing)

 

[poadeleted20]

Generally speaking, in light planes, pro-spin aileron will create adverse yaw against the spin, helping slow the spin rate. However, it will also generally create a rolling moment in the direction of the spin. In any event, during spin recovery, the ailerons should be placed as directed by the POH.

BTW, an F-4's rudder is useless in a spin, and it requires pro-spin aileron with neutral rudder to effect a recovery.

 

[gismo]

I believe the effect of aileron in a spin is conditional on three major factors. One is wing washout (and other factors that reduce airflow separation over the ailreon in a stall or spin). A wing with considerable washout will allow "normal" alieron function well into the stall and as a result, the use of aileron in a spin may be useless at best and counterproductive in the worst case. IOW the drag of the downward deflected (outside) aileron will be fighting with the extra lift produced by that same aileron. Second is the aileron configuration itself. Freise ailerons produce minimal adverse yaw (and it's adverse yaw from "stick to the inside" control position that normally assists spin recovery) so they should be less able to reduce the (yaw) rotation. Finally, different aircraft and different spin modes put the spin axis in different locations relative to the ailerons and that is bound to affect any aileron input's impact on the spin. Angular momentum is a big factor in spins (and one of the reasons why full power is destabilizing... that big gyroscope otherwise known as a propellor creates significant forces in a spin) so the distribution of mass affects spin dynamics in non-intuitive ways.

BTW in an aerobatic airplane certified for unlimited turns in a spin I see no reason why a pilot couldn't experiment with the effects of various control inputs during a spin provided there is plenty of altitude for a "proper" recovery, so if you want to find out whether aileron helps or hinders recovery in a particular airplane, I think you should just try it.

 

[Diana]

I believe the effect of aileron in a spin is conditional on three major factors.

Thanks Lance. I appreciate your analysis.

BTW in an aerobatic airplane certified for unlimited turns in a spin I see no reason why a pilot couldn't experiment with the effects of various control inputs during a spin provided there is plenty of altitude for a "proper" recovery, so if you want to find out whether aileron helps or hinders recovery in a particular airplane, I think you should just try it.

Good point. It's on the agenda this morning. BTW, I have that video clip for you that you asked for with the view of the wing during a spin.

 

[parrothead]

Diana, you talked me into it. Now I'm on this board! When my wife complains about the fact that I stay up too late on the computer, I'm blaming you!! Have a great weekend!

 

[Diana]

Diana, you talked me into it. Now I'm on this board! When my wife complains about the fact that I stay up too late on the computer, I'm blaming you!!

Oh, my. I get into enough trouble as it is!

Did you do any aerobatics when you went flying in the CJ yesterday?

Have a great weekend!

You too Bryan. Let me know if you buy that 172.

 

[Diana]

Well, as I have received additional input elsewhere, I see that I'm not the only one confused about the definitions, and therefore the concept.

 

[parrothead]

No aerobatics, just a nice flight. It was a great day to fly! The 172 had mucho corrosion problems due to mouse pee from sitting in the hangar since '89, and was in need of an overhaul, etc, etc. It still brought $22,000. I thought that was crazy, but more power to the new owner! I'll keep looking. The one I'm looking for doesn't have to look pretty or be a newer one, it just needs to be something safe and solid (and cheap) so I can build some time and fly the kids around the patch.

 

[Diana]

No aerobatics, just a nice flight. It was a great day to fly!

Bryan, I'm glad you enjoyed the flight in the CJ. I've ridden along on some rolls and loops in it, but no spins yet. Did you go with Terry to Arkansas to get the elevator repaired? Did Terry figure out who inflicted the damage to the airplane?

The 172 had mucho corrosion problems due to mouse pee from sitting in the hangar since '89, and was in need of an overhaul, etc, etc. It still brought $22,000. I thought that was crazy, but more power to the new owner! I'll keep looking.

It might be better if you bought an airplane that you could start flying now, rather than one that will take a lot of time and unknown amount of money before it will be flyable, IMHO.

 

[parrothead]

Amen on buying the plane now. That 172 would've taken me a couple of years and truckloads of ca$h just to get it in the air.

The first time Terry took me up in the CJ he put it through some aerobatic maneuvers. The last ones were a couple of spins. That's the first time in a long time that I have felt a touch of air sickness. It was great!

I didn't get to the point of losing lunch, I just felt a little weird, that's all. My grandad in Miami (Tom met him a couple of times) had a Christian Eagle that was a real hoot to fly. He introduced me to loops and rolls, but Terry put me through my first spin. I loved everything but the spin. It was a bit too disorienting for my taste and it was the first time I have ever felt that I was in a plane that was out of control. I had full confidence in Terry, it was the feel of the spin that freaked me out. Still, it was fun and I'd do it again in a heartbeat (while I'm in the PASSENGER'S seat!).

 

[jkaduk]

BTW, an F-4's rudder is useless in a spin, and it requires pro-spin aileron with neutral rudder to effect a recovery.

I heard it required the drag chute.

 

[tonycondon]

wasnt that a future astronaut who discovered that? Deke Slayton perhaps?

 

[poadeleted20]

Originally Posted by Ron Levy

BTW, an F-4's rudder is useless in a spin, and it requires pro-spin aileron with neutral rudder to effect a recovery.

I heard it required the drag chute.

F-4 boldface procedures:

Out of control
Stick - full forward
Ailerons and rudder - neutral
If not recovered - Maintain full forward stick and deploy drag chute

Spin
Stick - Maintain full forward
Ailerons - full with spin (turn needle)
Aircraft unloaded - ailerons neutral

Given the gyrations an F-4 goes through when it departs controlled flight, you really wouldn't know you were in a spin until things settled down. So you'd execute "Out of Control" first, followed by "Spin" if "Out of Control" didn't work, which means you'd have the drag chute deployed before you even started evaluating whether you were in a spin or not.

 

[poadeleted20]

wasnt that a future astronaut who discovered that? Deke Slayton perhaps?

Not Slayton, as he was USAF and the Air Force didn't get the F-4 until after the first seven astronauts were named. It could have been Wally Schirra, as he was flying F-4 suitability tests at Pax River when he was selected, but it was more likely someone at McDonnell before the plane was even delivered to the Navy. None of the other three Navy/USMC pilots in the original seven were at Pax River at that time -- all were in non-test-piloting assignments when the F-4 testing was going on.

 

[Steve]

A not so recent interview of Dick Rutan includes a mention of riding out an F-4 spin in the back seat. Another description I've read of spin recovery in the F-4 stated you eject if you don't have it under control by 10,000' due to the altitude required to recover from the resulting dive. I've got a video around here somewhere that shows an F-4 in spin testing with the drag chute wrapped around the vertical fin...

 

[poadeleted20]

Another description I've read of spin recovery in the F-4 stated you eject if you don't have it under control by 10,000' due to the altitude required to recover from the resulting dive.

That's straight from the flight manual -- if you're out of control at/below 10,000 AGL, eject. It's 15,000 for the F-111.

 

[Scott 'Gunny' Perdue]

Generally speaking, in light planes, pro-spin aileron will create adverse yaw against the spin, helping slow the spin rate. However, it will also generally create a rolling moment in the direction of the spin. In any event, during spin recovery, the ailerons should be placed as directed by the POH.

BTW, an F-4's rudder is useless in a spin, and it requires pro-spin aileron with neutral rudder to effect a recovery.

Most POH's I've seen have very sketchy direction on spin recovery.

Your comment about the F-4... I'd be curious where you got that? Navy? Generally speaking in swept wing airplanes In-Spin aileron is the best control input (the rudder is mostly blanked in a stablized spin)... for the F-15E this was part of the recommended procedure. For the USAF F-4's... for a departure you were supposed to pull the chute.

In-Spin aileron is actually Anti-spin.... it increases pro-spin roll and decreases pro-spin yaw (due to the precession of force applied)... it increases the rotation rate and steepens the attitude. Depending on the airplane it may be enough to degrade the situation into a high-speed spiral... but mostly in exposes the rudder to more airflow.

Conversely, Out-spin aileron is actually Pro-spin... it tends to flatten the spin and potentially will increase the rotation rate The roll force is precessed in application reducing the pro-spin roll and resulting in pro-spin yaw. This is one of the techniques used to flatten a spin (that and power).

 

[Diana]

In-Spin aileron is actually Anti-spin.... it increases pro-spin roll and decreases pro-spin yaw (due to the precession of force applied)... it increases the rotation rate and steepens the attitude. Depending on the airplane it may be enough to degrade the situation into a high-speed spiral...

That's what has happened in the Citabria when I have used left aileron in a spin to the left...it turns into a spiral.

 

[gismo]

That's what has happened in the Citabria when I have used left aileron in a spin to the left...it turns into a spiral.

That's been my experience in the planes I tried it in. In the Porterfield (which really doesn't want to stay in a spin for long) I usually have to hold the ailerons away from the spin (I call that pro-spin but what I mean is left aileron in a spin to the right) as well as full up elevator and pro-spin rudder in order to make it around three times without translating into a spiral.