Spin Recovery
 

Hi
I was watching a copy of an old TV prog called Test Pilot and in it they stated that the only swept wing aircraft that was safe to use/instruct on for spin testing at Boscome Down ETPS was a Hunter.
As the Hunter is now not used by the RAF what/which aircraft do they now have to use ???:confused::confused:
All the Best

Hawk?

.

According to this site: http://www.qinetiq.com/ix_etps/school/aircraft.html

This is the ETPS "fleet"
- Hawk T Mk 1 XX342
- Astra Hawk T Mk 1 - XX341
- BAC 1-11 ZE432
- Andover C Mk 1 - XS606
- Tucano T Mk 1 ZF510 & ZF511
- Bassett VSS XS743
- Gazelle HT Mk3 XZ936 & XZ939
- Sea King HC Mk4 ZB506 & HU Mk 5 XZ575
- Lynx AH Mk7 ZD560 and ZD559

So it looks like it will be the Hawk that's used for jet/swept wing spinning. Just to clarify the first post - the advantage the Hunter had was that it was cleared for inverted spinning, and that was what the programme was alluding to; the Hawk is of course cleared for erect spins, and used to train these routinely.

Spin Tests
 

I wouldn't want to see the '111 used for spin testing !!!

Usuallualy deliberate spin tests are carried out with a cartridge fired 'anti-spin' parachute fired from the tail of the aircraft - this includes such modern stuff as the F-22; just in case the normal recovery moves don't work out.

This has a 'sling-shot' effect of dragging the aircraft out of the spin rather like a sea-anchor on a boat - over to any Test Pilots reading for a better description please !

In the case of the Hawk, a special 'spin panel' set of instruments was fitted at its' birthplace, Dunsfold, to the company demonstrator / test-bed G-HAWK - ZA101 to aid the pilot.

Obviously a major consideration was ensuring the fuel pumps/feed were able to cope with a spin, including inverted.

There's a difference between spin TESTING - where you basically don't know what might happen, and need things like a recovery chute for the worst case scenario - and spin TRAINING - where the characteristics of the airframe are known and understood and it's the pilot that is the thing being studied, not the aircraft. ZA101, as a company test aircraft, was used for the former; ETPS is concerned with the latter, so I'd be somewhat surprised to find their aircraft fitted with an anti spin chute, any more than any of the RAF's training aircraft.

Unless it's been de-modded and changed job (which seems unlikely), Tucano ZF510 is instrumented for spinning in the ETPS role, and I'm pretty certain is cleared for erect and (I think?) inverted spinning, whilst the Hawk is cleared for erect spinning (and is clearly swept wing).

After my spell at Boscombe, but don't ETPS also have some Alpha Jets nowadays - as a swept wing jet trainer, presumably that has some form of spinning clearance that ETPS can make use of in teaching spinning assessment.

G

They certainly had a couple of Alpha Jets for a while, and in fact they had a "better" spin clearance than hawk - still erect only, but cleared for more spins. Used to be a marketing issue when the two were the main competitors in the market - it's a kind of stupid thing to be a selling point, because the idea is to train to get out of a spin, not see how long you can stay there. Hawk was limited because the aircraft actually speeds up in the spin and so eventually you get to a speed where the loads become excessive, whereas AJ is more like a stable speed, so you can keep going longer.

Since in both cases it was "many" rotations you were cleared for (my recollection is 8 for Hawk and 12 for AJ, but those numbers are VERY hazily remembered) it really was a very pointless thing to argue about.

Just out of interest, what sort of instruments were fitted to the spin panels? Some sort of rotational rate/trend gauges?

ASI

Spin panels in the days when Dunsfold was used to test aeroplanes not motor cars had three things:

A pair of red and green lights to show your direction of roll

A turn and slip to show your direction of yaw

A decent unambiguous altimeter

Surprisingly it may be difficult to be sure whether you are spinning errect or inverted just by looking out of the window. The roll lights being opposite in sense to the turn needle show you to be inverted. The use of the altimeter is obvious.

Double zero might have a spin panel photo for you.

JF

Thanks for that - A rather more simple setup than I had envisaged!

John Farley said:
Having never spun a swept wing jet I'm curious as to how one could get confused over this. Is it because swept wing aircraft have a greater variation in pitch attitudes during the spin?

In 1993 I went to Russia for 4 weeks to fly with Genna Elfimov in YAK 52's .

One day we experinced inverted and normal spin procedured for competition.
One sortie resulted in a very flat spin that did not seem to respond to normal, power off, opposite rudder, stick forward recovery.

I imputed inspin aileron and stick back. as per ERIC MULLER method.
Genna went beserk, "Never stick back he screamed " we recovered and after landing debriefed. He expalined on the board the 4 different spin recovery techniques from YAK 52 to jet fighters. It was all about getting some fluid over any controll surface. I had Eric's book on aerobatics with me and he borrowed it.
The next day he announced we would try Eric's recovery method. I exclaimed that he had convinced me that the method was flawed. "What if it doesn't work " I said. "The we get out of aircraft" he stated calmly.

We climbed to about 3000 mtrs and started to increase the spin to a very flat profile with power. We then followed Eric Mullers recovery and the YAK stopped on line.

On landing he announced "OK there are now 5 ways of spin recovery"

Hunter spinning video:

http://www.youtube.com/watch?v=TR2NuJJhacA

and the Hawk:

http://www.youtube.com/watch?v=M8nD5...eature=related

I notice both swept wing jets tend to "tumble" with greater amounts of pitching than the straight wing aircraft I've spun. Can anyone reflect on this or explain why?

The reason for no inverted spinning in the Hawk? Could that be the disturbed airflow over the wing blanking the rudder?

During my time on ETPS, we regularly span the Hawk and Tucano. The Hawk was cleared for erect spins only and the Tucano for erect, inverted and power on (40% Tq IIRC).

We carried out a dedicated spin exercise which involved the use of the Tucano where incorrect entry, maintenance and recovery procedures were investigated. However these were still bounded to prevent nothing worse than an inverted or erect spin developing.

The QinetiQ Alpha Jets are not used for spinning at present, however there was an aspiration to use them. AJ designs vary considerably and those that I have spun have anti-spin strakes underneath the nose. The QQ jets have a nice smooth pointy nose so that may lead to undesireable spin characteristics.

That being said, one trip on the course is flown on the French TP School's (EPNER) AJ's. These have the spin strakes but the nature of the spin that can be induced is varied. Smooth, oscillatory, erect, inverted, flat, you name it, it's there! One hell of a ride.

Similar reasons as to why pitching up/down in the stall is more of an issue for swept wing types. A classical spin is essentially an auto-rotative stall; the spin is in part 'powered' by the wings being stalled. With the wings being swept, as the degree to which each wing is stalled varies the aircraft pitches up and down a bit.

Another factor will be inertia effects; these aircraft, being larger/heavier, may have more pronounced inertia ratios between Ixx and Iyy or Izz - which can be a big player in the nature of the spin. BAC found significant variation in the spinning behaviour of Jaguar with relatively minor design changes, partly due to inertia effects I believe (there's an ancient RAE note on spinning characteristics, derived mainly from WW2 experience, which identified Iyy/Ixx as a significant parameter, IIRC. A similar analysis holds for more modern types, although it takes a bit of jiggery-pokery to make it work)

One of the problems with inverted spinning a Hawk is that the rudder loads (it's manual) become huge. In an erect Hawk spin the rudder either stays more-or-less straight, or can be kept there fairly easily; IIRC, the technique to keep the spin going is to hold pro-spin rudder, and centralising it is both easy and a prompt recovery action. Inverted, the rudder hinge memoents blow the rudder to the pro-spin direction; it can require CONSIDERABLE pilot effort to get the rudder central in order to effect a recovery (IIRC, one flight, which MAY have been an ETPS flight, ended up with BOTH crew pushing the pedals to get it centralised).

Ah! Thanks.

Bad news if flying a Hawk solo then. Out of interest how much height is used spinning a Hawk?

Well, it is possible that one guy could get the rudder close enough to neutral, but it's not an experiment I'd want to try. It takes a fair bit of enthusiasm to get it to spin inverted, so it's only really a problem if you choose to make it one.

One had to work hard to get the Hawk to spin IIRC.

Most of the relevant aspects of spinning on the ETPS course have been covered above but here is a little more meat on the bones. The Tucano and Hawk both have an expanded spin envelope to allow spinning outside of the Release to Service cleared envelope. This allows deliberate control mishandling at spin entry, during the spin and during recovery. It also allows the Hawk to be spun with the airbrake out and in the Tucano power on (30%TQ) spins in addition to the erect, left 4 turn spins in the R to S. However, to perform these spins a safety pilot must be in the telemetry ground station and the spin panel must be selected on. The most critical item in the 'spin panel' is a voice alerting device which automatically gives a voice command to 'recover' at the minimum altitude and to eject if not recovered by the relevant altitude.

The Alpha Jets at Boscombe are ex German Air Force ones that were never cleared for spinning in service althoug spin trials were flown and they could have been cleared had there been a need. Perhaps they will be cleared for spinning at ETPS one day but until then the EPNER Alpha Jets are spun whenever possible during the course. Out of interest, a spin panel was installed along with the flight test instrumentation fit into two airframes, and these have yaw rate (rather than roll rate) lights as the aircraft does not have a turn needle.

The Hawk inverted spin incident is an interesting one. The airframe in question, XX343, had been landed with the right main landing gear stuck up in the late 1980s. Thereafter it had some slightly unusual spin characteristics, one of which was a tendency to enter an inverted spin when certain deliberate mishandling cases were evaluated. In particular, relaxing the full aft stick back to trim whilst maintaining full pro spin rudder or applying full outspin aileron when there was a roll rate hesitation (which was actually one of the inverted spin entry techniques in the Hunter). I had it start to go inverted several times but I used to watch the AoA gauge closely when making these inputs and if I saw it drop below 10 degrees I knew that it was going inverted so I would just centralise and recover. However, I had some students who did not catch it and it actually went inverted, although you could then centralise the controls without difficulty during the first half turn. It was only if you let in go past that point that the rudder overbalanced, and once stabilised in a fully developed inverted spin the foot load to centralise the rudder was about 250 - 300 lbs (based on USN T-45 spin trials). The incident that occurred was a student pilot and a student FTE together. The pilot moved the stick forward too rapidly with pro spin rudder and the aircraft stabilised in an inverted spin. He knew what he had to do but could only get the rudder back to about 1/4 in-spin which was not enough for recovery. Eventually adrenalin enabled him to centralise the rudder, possibly with some help from the FTE and, as I recall, rotation stopped around 6000 ft. the telemetry safety pilot could offer no help as the pilot in the aircraft knew what to do but just couldn't do it! Shortly afterwards we stopped solo students performing relaxed back stick spins!

To go back to The Gorilla's question about visually recognising an inverted spin, this can be a problem in straight wing aircraft as well. At least one fatal accident in a Pitts was believed to be caused by the pilot not recognising that it had gone inverted. Although the pitch attitude is fairly stable, it is sufficiently nose down that it is hard to differentiate between more than or less than -90 degrees. Coupled with the high roll and yaw rates an it can be hard to recognise, particularly for someone who hasn't seen it before. There are some fairly "experienced" guys out there who've never explored/been shown inverted spinning.

In the 1980's film CLOUD DANCER about USA aero comp starring David Carradine, a Pitts crashes for real inverted, the pilot never recovered. It was left in the film at the request of his family.

BizJetJock

Yes it can be a real problem. I've had recoveries from lomcevaks in Pitts S2As go wrong a few times. On 2 occasions ac was still rolling with neutral controls after recovering to down vertical (well below 1,000ft). With T&S fitted, turn needle was a good clue as to erect/inverted; without it, a squeeze of rudder to oppose the roll increased the roll rate so I correctly assumed it was inverted. I defy anyone to visually differentiate between 89 and 91 degrees nose down.

rts

I got into an inverted spin in a JP5 (hard to imagine how you could do it by accident - but we did!). It felt like an erect spin, but was very nose down and very high rotational - and very disorientating. It was only the T+S which was telling us it that we were inverted that it became clear what we had to do to recover. However, we were both reluctant to believe it. The recovery was immediate when it was initiated, but it took us so long to think about what was going on and what to do about it, we bottomed out below ejection height.

We snagged the aircraft. It turned out one of the wings as out of incidence following an overstress.

The SSVC film 'The Spin Explained' which was shown to all RAF students on the Tucano explains everything you need to know about the spin including the moments of inertia and B/A ratios.

It's available to purchase, but very expensive. It is however, very good. There is also a much older film "Spinning Modern Aircacraft' which was made in the 60's. It also is good, but not as good as the new film which has some pretty natty (for 1990!) computer graphics.

Archive
 

Does anyone know where to find a good piece of archive footage of one of the development Jaguars from BAE Warton (then BAC of course) where Tim Ferguson (Test Pilot) is falling from the sky for a good while in a flat spin, but eventually recovers it without incident. I first saw it on a programme called QED in the 80's. Ive looked all over the net (Youtube etc) but cant find it anywhere.

Do you mean the one where fuel is spilling out the intakes?

Bill Finagin, who has done thousands of spins in Pitts and other types, teaches that you need to put the controls to neutral and take ALL power off, which means that you don't need to worry about stick forward or stick back. Look along the nose - then, "nose goes to too much rudder". It's a bit disconcerting when you experience it for the first time, but applying corrective rudder on this basis applies equally well to upright or inverted spins. Once the spin stops, recover.

i can think of one aerobatic genius that would argue this statement. AC.

I'm undoubtedly going to expose my own ignorance here, but.. how can you be in a spin (beyond maybe the initial 2-3 turns when you may be still travelling 'along'), when the aeroplane is 89-91 degrees nose down?

Surely once properly estabished, the overall vector of the plane is vertically down - so in order to be stalled, the wing needs to be at some significant degree from the vertical?

My only experience of an inverted spin was definately rotational, and relatively flat - the horizon line was in clear view. It wasn't in a pitts.

An accelerated spin in a Pitts is extremely steep. Perhaps the 89-91 is a bit of an exaggeration but whether upright or inverted it does look vertical.

To add to HappyJack's post - Bill limits that teaching to the Pitts - he calls it FART - refer his article in Sport Aerobatics magazine. He certainly demonstrated it satisfactorily to me. If I was disoriented in a Pitts I'd personally use that rather than Beggs-Mueller now.

(shouldn't we be in a different forum for this discussion the way its going?)

Spin recovery
 

I was told by a good pilot ( then on G.A, now an airliner captain like his father before him, who was also earlier on a fighter pilot ) ;

If in a spin , just MAKE A BIG CHANGE OF INPUT - whether any control surface, airbrake if you have one, or throttle, just make the input change & de-stabilse the spin.

Sounds reasonable to me...

In some aeroplanes, that may work - on the other hand, pick the wrong big input and you might just drive it into another (and less recoverable) spin mode. Aileron in a Bulldog springs to mind. Or power in a Tucano left hand erect spin - which tends to stabilise the spin and make recovery much more protracted (when we were doing spinning trials on the Tucano it fairly consistently would NOT recover from that mode with full power and then few more turns once it had been closed).

Actually, that advice comes across to me as downright foolhardy - it might work, if you get lucky, but given that any certified aeroplane will have a tested and approved spin recovery, and any aeroplane has a better chance of responding safely to a "standard spin recovery" than a randomly selected large control input which *might* destabilise the spin, but equally might stabilise it, or disturb it to something nastier than the mode you're in already.

G

Absolutely Genghis
 

That is a terrible bit of advice.
Depending on the dynamics of the aircraft at the time, making a big input change could cause enough excess loading to cause damage / structural failure.... or just expedite your arrival at the scene of the crash.
As you allude to, the development of safe recovery techniques is part of the Flight Test Programme. An expensive part and something we don't do for fun.

How can one inadvertedly get into an inverted spin ???

To enter an inverted spin you need to apply FULL FORWARD stick and OPPOSITE foot pressure on rudder (left foot for right spin).

That is a lot of cross controls to apply inadvertedly.

Assuming that you do it fully cosciously on a suitable aircraft, and that you have the situational awareness of what is happening ( comes with practice, the first time everything looks blurred around, the brain just does not follow), you will quiclky notice that you will be positionned OUTSIDE the sense of rotation. i.e. the canopy and pilot will be rotating on the outside.

On an erect spin, the canopy will be INSIDE the rotation during the spin.
Take a model airplane, simulate the manoeuver and you will get the picture.

Then on entry and during rotation on an inverted spin centrifugal forces will also be directed on the outside resulting in malfunctions in the oil/gasoline supply to the engine, if not equipped with fuel injectors and Chrsiten inverted oil supply.

Unconfortable to the pilot and not good for the aircraft engine....Oil sumps lines and carburettors are fed when gravity acts upon them !!!!

So if you have a change get out there, jump in the suitable aircraft with somebody who has practice and go demistify the whole manoeuver !!!

Actually I rather disagree with you. The 'standard' entry to a deliberate inverted spin requires full fwd stick and rudder. All any spin requires is asymetric stall - usually yaw and a suitable angle of attack, same as people still manage to spin into the ground, without doing a deliberate spin entry.

for example - here's a little inverted spin scenario:

Rolling off the top of a loop - you're a bit slow, a little hamfisted, and you forget that with negative alpha you're effectively cross controlling as the adverse yaw is reversed... trying to hold the line, and...

Oooppss! the world suddenly rotates..

Hopefully you're smart enough to catch it at the incipient stage, but if you're already head in/singular focus, who knows.

Of course inverted all the anti spin design features like washout are working against you.. so it's arguably even easier to spin inverted.. and in some types, mishandling the ailerons etc can turn an erect spin into an inverted spin.

For that matter, you don't even need rudder to spin - I've seen (deliberate) spin entries off adverse yaw/aileron use at stall (in gliders, granted).

Call me paranoid, but I did - last week. Damned unpleasant it is too - I enjoy spinning sunny side up, and do basic aeros regularly but the flick-upright-bunt-over is somewhat confronting, and a little disorienting. My lunch *just* about survived.

Jaguar Development
 

I have a video of Jaguar spinning in the early development. I think that it is on a video tape titled "Jaguar/TSR2" (I say 'think' because I haven't watched it for ages). It is produced by Colin Higgs of DD Video, 5 Churchhill Court, 58 Station Road, North Harrow, Middlesex HA2 7SA.
Incidentally I was the Jaguar Development Project Officer (the DEEPO) from 1981 to 1984 running the NAVWASS update programme and the wing strengthening programme.
Hope this helps and I hope I have the right video.
Cheers,
Clive Tudge
Brisbane Australia.

Spin recovery
 

Ghengis,

I will bow to your superior knowledge, I'm not even a PPL but have done hundreds of hours ( at least ) as an aerial photographer, often used as a dumb autopilot, though I did take courses in aeronautics etc.

The pilot who gave me that advice re. " make a large input " impressed me and my dad ( who was a FAA engine fitter on Seafires inc. Salerno then the much more suitable Hellcat, ending 37 years later as a foreman on Harrier 2's ! ).

The reason that pilot impressed us was he did a very strict engine check - almost a 'minor' ! Before we even thought about getting in the thing.

Then again he may have known something we didn't, as 6 weeks later it went in in a big way ( no casualties as far as I know ) through engine failure...

I think the only real answer to spin recovery is a tail ' chute or an ejection seat !

Wasn't there a case of a Trident or similar which deployed the 'anti-spin' 'chute, forgot to jettison it & couldn't understand the lack of 'go' & ended up landing ( safely ) in a field ?!

If no-one believes this, and I don't blame them, I can dig out the details...

Hi Clive,
Nice to hear from you - was Ops OS2 under Wg Cdr JS in 82. Remember a few happy times in Paris/Warton. Hope you are fit and well. See you've emigrated to Aus - I'm still in the UK. From memory we didn't expect the T2 to be able to recover from a spin, althought there was a drill for the GR. Spent many hours trying to extend the Jaguar life at various meetings - partly successful until the beast was grounded by the Air Force. Would be interested in a DVD of the video - which was Pete Orme AFAIK.
Colin

Mark1234 and markkal please note:
If you read my post22 again you'll see that I'm not referring to academic premeditated spin entries, stabilised spins and 'standard' recoveries. In my foolish youth I entered a lomcevak in my Rothman's Pitts S2A from a 45degree climb on knife-edge, and rarely had more than 700ft agl at entry (that's the foolish bit). By the time I'd 'recovered' to the down vertical I was free-falling at idle power with controls neutral and usually between 550 and 600 ft agl. I completed the manoeuvre over 100 times and only 2 went pearshaped after the 'recovery' - the aircraft was rolling without control input, and I assumed that the reason was an auto-rotational condition. The only significance of my remark about 89-91 degrees n/d is that it affects the 'subsequent' recovery actions and with only 2 or 3 seconds to get it right before an 'Oh Christ' pull-out it was nice to have a T&S that never lies about yaw direction.

Double Zero

Believe Ghengis and tightflester, NOT your friend. Unless ALL else has failed. My previous post on another thread re spinning an MU2B-40 explains my last remark.

Regards to all,

rts

Clive - will you have that video at Watts Bridge next month?