Unusual spin recovery technique

[MayorQuimby]

I recently flew a Robin 2160 - Nice airplane.

However, I was taken by surprise when I noticed the counter-intuitive spin recovery technique in the POH.

I'd be delighted if any of the knowledgeable visitors to this forum could explain to me (in layman's terms) the aerodynamic reason for applying opposite rudder and then PULLING THE STICK FULLY BACK!

PS. This is not for inverted spins.

Regards,
MQ.

[Airbedane]

MQ,

I've not flown the Robin 2160, nor am I familiar with it's layout, but here's a few thoughts, straight from the French TP course notes, circa 1981:

When testing spin recovery in aircraft, particularly in France, all combinations of flight control positions are essayed.

I suspect that on this aircraft, the rudder was found to be the most powerful and thus, the most effective anti spin control. I also suspect that the rudder is blanked by the tailplane when full down elevator is held in a spin (think of where the relative airflow is coming from). In fact, it may be that the blanking is so heavy that spin recovery may not be possible with the stick forward - I must stress that I don't know this for sure, I'm talking generic here. However, if the elevator is held fully back, more of the rudder may be exposed to the airflow, thus allowing the most effective anti-spin control to be employed.

Whilst not a complete answer, I hope the above points you in the right direction.

A

[John Farley]

Agreed. Stopping the yaw as quickly as possible is the aim. If the yaw stops quicker with the stick back because the rudder does a better job like that then so be it.

[djpil]

MayorQuimby - would you mind posting the complete text of the spin recovery technique from the POH. As others have suggested, we'll probably find that its not much different than what is used for other types with the same basic tail layout.

(I was a student at Cranfield when the Robin was there doing spin trials from which the rudder grew and the ventral was added).

[sycamore]

Had a look at an R -210 today- may be similar/ may not. Has a stabilator,that with full-fwd. stick would seem to blank off a lot of airflow over the rudder. With aft stick, the rudder seems to have a much better chance as the apparent airflow direction is more in-line with the stabilator.
Airbed- ca va bien M`Sieu?
Syc.

[LOMCEVAK]

I seem to remember this being a recommended aerobatic spin recovery for some aircraft. I believe that Eric Mueller was a great advocate. I do not have a copy of his book but I will try to find some references. Out of interest the Tornado spin recovery is full back stick (to unblank the fin) and full in spin lateral stick.

[djpil]

Over a bottle of red wine one evening I told Eric that the spin recovery method he was promoting was consistent with the NACA standard spin recovery method - from memory, described as such in
Summary of spin technology as related to light general-aviation airplanes
Bowman, J. S., Jr. (NASA Langley Research Center, Hampton, VA, United States)
NASA Center for AeroSpace Information (CASI)
NASA-TN-D-6575 , 1971

Tail-design requirements for satisfactory spin recovery (http://naca.larc.nasa.gov/reports/1946/naca-tn-1045/) is the earliest reference I've seen to effect of the pause between applying opposite rudder and down elevator, although there is earlier work on shielding of the vertical surfaces.
Comparison of model and full-scale spin test results for 60 airplane designs (http://naca.larc.nasa.gov/reports/1950/naca-tn-2134/) refers to a desired spin "recoveries in two turns or less by reversal of rudder followed approximately 1/2 turn later by downward movement of the elevator".

[MayorQuimby]

Thanks for the replies guys.

djpil, I don't have the POH to hand - I'll post when I do - it was very simple - Full opposite rudder, stick fully back. I do remember it mentioning something like "the only important action is opposite rudder", suggesting that it is probably eager to come out even without the elevator-up input.

I guess the reason I found it unusual was that I had probably convinced myself that spin recovery is all about stopping the yaw AND unloading the wing. I hasten to add that I'm a very low hours pilot.

I've yet to spin in the Robin, but would I be correct in supposing it might be a bit twitchy in the recovery? I'm basing this on an assumption that, with stick back, the wing would still be stalled when the yaw stops.

Regards,
MQ.

[Aerobatic Flyer]

The stick back instruction is for the reasons suggested by Airbedane above. If you follow the instructions in the POH, you will stop the rotation quickly and recover with minimum loss of altitude.

However, the Robin will recover nicely from a spin even with the stick fully forward. If you are want to do a competition spin, with a vertical exit, you'll probably find it better to use forward stick. The rotation takes just slightly longer to stop, but your attitude on exit will be much closer to vertical and you will score more points if being judged!

I haven't flown a Robin 2160 for some time, but I seem to remember the POH mentions that the "stick forward" recovery can be used, but is not as quick as with the stick back.

[Feck]

The Harrier spin recovery is also stick back I believe. Blanking again?

PS I loved the 2160, great plane. Shame (the one I flew) had a carburettor, always hated engines stopping when inverted.

[paulo]

Repeating a bit from Private forum, but here's my experience with the Robin....

...my instinct has been not to pull fully back, just keep a bit of pressure on. There's placarded 2.5 turn limit, and in that limit it's never gone fully developed for me.

Recently though someone demo'd full stick back, and it did go fully developed (can't say for sure whether it was the recovery technique, or the entry). We did about 5 or 6 quick rotations in 1000ft before recovery.

Great ride, but I'll stick to my more tentative technique for now. ;)

[I've also heard of successful recoveries from inadvertant stick forward.]

[Nozzles]

You wouldn't believe the F-16 spin recovery dril................and as for the F-18 drill-it takes longer to quote than it does to fall from
10, 000 feet to Earth

[Genghis the Engineer]

If my memory serves me correctly, the Jaguar was

- Let go of all controls, watch ASI
- If Airspeed not above (something) by FL100 - eject
- FL140 for a 2-seater.

Which seemed a little fatalistic in a low-level jet.

G

[paulo]

Perhaps this should be another thread... I'm just a curious novice aeros pilot, but in terms of the slippery fast stuff, just how hard is it to get in to an inadvertant spin?

I'm assuming that with such a big 'hoover' onboard that you need to go a bit doolally to end up having to reach for the bang handle. i.e. Throttle sorts out most things before you really depart from controlled flight?

[Airbedane]

Paulo,

Yes, it should be another thread, but here's a starter:

Swept wing aerodynamics are significantly different from that of the straight wing. CL max is of a lower value, but occurs at a much higher alpha (angle of attack). On some swept wings, they still produce lift at approaching 90 degrees alpha (they also produce phenominal drag, too). The problem is that that sort of lift is unstable, and can let go at the drop of a hat. If one wing lets go before the other, bingo, inadvertant spin.

Engine wise, the thrust may help avoid spin entry - as with the Peggy in the Harrier 1- but not so on the Jag. The intake distortion at the higher alpha's will cause the engine to go into surge close to the departure, or during it, so the mighty Adour won't be much use to you - embryo Jag pilots used to be shown the spinning film in training; it shows flames coming out of both ends of the engine as the aircraft departs and spins earthwards!

There's obviously a lot more to it than that, but lets see how the thread develops. If you want a personal on it, drop me a private message and we can meet up at Old Warden some time.

Ghengis,

My personal spin recovery drill in the Jag was:

Centralise controls, if it's still spinning, let go controls.
Find the altimeter, if you can't find it, Eject ( the aircraft gyrations were so severe that finding any instrument in the cockpit was academic).
If you can find it, when below 10,000ft and still spinning, Eject.

In practice, the recovery could only be used when playing at combat above FL100, or in flight test. Luckily, the single seater had a good recovery from departure, although the two-seater wasn't. Operationally, we made sure we never exceeded departure Alpha, which lowered in value with every new issue of the FRC's. When I first flew the jet, the Pilot's Notes allowed: "a departure free operating envelope of 17 degrees normal and 20 degrees never exceed", in all configuraitons - I lost a lot of mates!

VBW
A

[Genghis the Engineer]

ACM above FL100 in a JAG !!!!!!! Surely only viable if you are bounced by another jag, and then if it had centreline tanks fitted.

My recollection was a rather lower limit (I should admit to only about a dozen hours backseat, and most of that on ETPS although I did P&HQ work on it from a desk for a couple of years) - I think 12 Alpha with centreline stores and 17 clean? What you describe sounds more like an early days FT limit?

An interesting question with a thin metal tube like the Jag (or Tornado, Mig-21 etc.) is whether you spin it or it hits an inertia couple. Whilst there's at-least a theoretical chance of a spin recovery - even in one of these, I'm not aware of a recovery from inertia couple without an external safety device. I've had a few interesting barside conversations with a certain retired WingCo who jumped out of a T2 about 25 years ago, and he still has no recollection of events between briefing and waking up in hospital - apparently an aeromedic subsequently showed the BOI that the oscillations were sufficient to blank his memory of the surrounding event, which presumably is what happened. (Apparently it was also shown that he had a fighting chance of having pulled the handle with his teeth!).

G

N.B. Appreciate the point about separate threads. I'll let it run as is for the moment, if it seems to start running seriously at cross-purposes I'll see if the moderators tools will let me split the thread.

N.B.B. Answering Paulo's specific questions, a highly loaded but responsive swept wing like a Hawk or Hunter has no particular tendency to spin inadvertently, but responds well to a deliberate spin entry - the actions being pretty much identical to those for an SEP. An aircraft like Jaguar or Tornado is a special case because it has an "intertia couple" mode which has much in common with the spin but is triggered by high AoA rather than an aerodynamic stall per-ce. In the Jag the aircraft starts wing-rocking alarmingly from about 1½ degrees above the AoA limit (which has a klaxon associated with it - therefore little excuse for exceeding it). If taken to extremes the aircraft starts a pitching-rolling-yawing oscillation which technically isn't a spin but looks jolly like it. This characteristic is associated with aeroplanes that have high pitching and yawing inertia due to a "cigar-tube" fuselage but very low rolling inertia due to lightweight stubby wings. Spin recovery in a fast jet tends to be straightforward and little different to a piston-prop, except that powered controls eliminate nasties like rudder-tramping and high stickforces, and the lack of torque tends to make the spin pretty-much identical left and right.

[Airbedane]

Hi G,

ACM above FL100 in a Jag - no problem if clean or with two empty drop tanks. The power weight ratio was quite high with burner, which could be used selectively quite effectively. ACM was, and I assume still is, part of general fast-jet training, so like v like, and like v unlike was caried out regularly.

Alpha Limit - you are quite right when you say that you remember the limit as being a lot lower when you flew the aircraft. It also had a selective alpha warner to prevent inadvertent exceedence. However, back in 1975 when I arrived on my first (and only) Jag Squadron, the limit released to service was 17 normal amd 20 never exceed. There was also no audio warning. Several aircraft, and sadly pilots, were lost. Over the following decade or so, the alpha limit crept downwards and an audio warner was introduced.

I'm sure someone will correct me on this, but I belioeve the single-seater had a good spin recovery, albeit with large loss of height, but the two-seater never demonstrated a full recovery. i.e. both aircraft were lost in spins.

Inadvertent spin - I've not managed it on a Hawk, but I did it twice on a Hunter in training, both cases were mis-handling of the controls. Several of my colleagues did the same, one failed to recover, but successfully ejected. The Hawk flies very much like a straight winged aircraft, the Hunter flies as a swept wing, but with some straight wing characteristics, float on landing is a good example.

You are right when you say that the Hawk and Hunter respond well to light aircraft entry techniques, but the Hunter requires swept wing handling to get into a predictable inverted spin - i.e. the use of inertia coupling. But for the latter, mis-handling at hi-AOA, or in a verticle recovery will often lead to an inadvertent departure, which may lead to spin.


VBW
A