Slingsby Firefly's
 

Hi All,

I've been reading, on and off, about the grounding of all those Firefly's that our Cousins have been operating. I'm aware that there have been some accidents, mostly related to spinning, but I can't understand why it's all ended up as bad as this.

Are US Firefly's so very different to those we operate in the UK? I'm pretty sure ours are ok, so what's going on?

Quite agree - spent the last 4 years flying the Firefly 160/260.
Great machine with no problems in the UK environment.
I believe the US machines were flown from high altitude airfields so maybe this is a factor.

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Arent a lot of the problems related to the American Engines fitted to the Slingsby?

All Fireflies are fitted with an American Engine, it's called a Lycoming, you may have heard of it.

Almost all the American accidents happened at an airfield with a ground elevation of 8000ft, in hot conditions, with military instructors who were very unused to piston-prop aircraft. The problems were largely with engine failures and spin recoveries.

The USAF operated another training base, with the same type, at about 2000 ft amsl in temperate conditions, with mainly civilian instructors (who inevitably were used to propeller aircraft). The serious accident rate was no different to most other training stations.

Go figure.

G

[This message has been edited by Genghis the Engineer (edited 16 February 2001).]

Oxford got rid of their Slingsbys after they nearly killed two of their instructors (Oh yes, and two of their students) - 'Delayed' spin recovery as I understand it.

Do enlighten us RC, I don't recall seeing more than about a further turn to recover a firefly - pretty much the same as a Bulldog (which has also got a, probably undeserved, reputation for an unrecoverable spin).

G

Okay, we all know that the press occasionally get things wrong. So too do laymen, from whom the press will seek to gain comment.

However, this article in the Yorkshire Post seems pretty good. Apparently many of the problems have been due to vapour locks, perhaps explained by the high altitude field theory.

Yorkshire Post

This link might only be valid for a few days. If the story isn't readily apparent, click to Page 2 and then click the main story.

Char

It's all getting more complicated...

...quoted from the Monday 19th Feb 2001 news section on www.avweb.com .

Ghenghis I agree

>engine stoppage caused by heat and altitude
But poor old slingsby dont make engines !

.. The T67 requires - like the bulldog
and the PA38 a correct recovery technique
.. it aint as forgiving as some

The USAF have done a study of the T67 at edwards AFB and the test pilots could find nothing wrong ,if my memory is correct they went to 20 turn spins with no recovery problems.

The biggest problem that the T67 had in the states was the fact that the americans dont like it if they did not make it !.

I am told that the reason for the T67 being withdrawd from service is that slingsbys product support was not up to the mark and the USAF had large numbers of T67 ,s sitting about waiting for parts.

The Slingsby does not respond well to sloppy spin recovery technique. A very experienced friend of mine owns one and gave me a very thorough demonstration of spinning and recovery. It recovers perfectly well but requires correct and positive control inputs.

In the lastest issue of Flyer, there's an article on the ab-initio training done at JEFTS which also happens to be done on Fireflys.

One thing caught my eye: it's normal practice to simply set the prop to 2,600 rpm and the mixture to fully rich. The author of the article raised his eyebrows at this, mostly on the grounds of cost.

I just wondered whether such a practice would have any pitfalls when used in an 'hot 'n' high' scenario? Any ideas?

(I'm not suggesting that the Cousins use the same procedure, by the way).

I flew and instructed in the T67 for several years. In general, a deliberate spin entry with full central aft stick and full rudder just before the stall induces a clean entry. Normally, centralising the controls within one and a half turns should result in recovery. (This makes it a good machine fo flick manoeuvres!) Care should be taken to ensure that the stick is moved far enough forward to put the elevators in the neutral position. This stick position is surprisingly far forward. Going back to the spin with correct pro-spin controls, a standard (CFS?) spin recovery technique is, once the direction of spin has been confirmed, throttle closed, full anti-spin rudder, pause, move stick progressively and centrally (aileron-wise) forward until the rotation stops, centre the rudder, roll to horizon, etc etc. The spin should recover in a couple of turns.
If aileron is applied at spin entry, the rate of roation may go high-speed a la Bulldog. Confirm that full normal pro-spin control is applied and ailerons neutral before recovery. The incipient stage recovery of merely centralising the controls may not work. (Differing inertia?)
IMHO, most 'scary spin' stories are the results of not taking/persisting with the correct recovery actions. The Chipmunk had similar scare stories in the 60s and 70s. Of course, without the tail-end mods fitted on most of the UK registered a/c and all the MoD fleet, the Chipmunk was more reluctant to recover than some.
One final point: the T67A has more critical longitudinal CofG limits than for its plastic siblings. These parameters should be carefully checked before spinning and aerobatics.
I recall there were problems with the spin charactersitics of the Tincanno when the A/B ratios were changed with the re-engined UK MoD fleet. Anybody care to comment re the 260hp version of the Firefly?

I've spun the Bulldog and the T67M260, but although I've flown the T67A, I've not spun it. Both suffer high rotational spin with mishandling, both suffer a protracted recovery if you mishandle, but both came out eventually with a degree of patience. I did notice a lightening of pitch forces as I approached the stall in the M260 which worried me, but Slingsby didn't consider it an issue.

I've also done quite a lot of spinning in the Tincano. The altered B:A ratio I don't think was as significant as the huge torque (remember the airframe was designed for 2/3 the power). A typical entry from manoeuvre with power required about 100lbf rudder and 100 lbf stick for initial loss of control action, then 150 lbf on the rudder for full recovery action. IMHO this created a disincentive to taking a hand off the stick to close the throttle - with full power it won't recover every time from an erect spin to the left - which is the most common mode from a departure. These were the main reasons that the RAF banned solo student spinning, although I don't know if that ban is still in place.

I don't however think that the Tucano that was lost in a training spin was lost as a consequence of the spinning characteristics - it had a pitch trimmer runaway during the spin itself, which led the pilot to think he'd had a loss of control after the recovery.

G

Agree that the T67A has very different charactristics depending on Centre of Mass. Some years ago we hired one for basic spinning and aeros instruction. The aircraft has a lowish mass limit; after weighing the crew, we used to calculate the fuel load pemissible and then measure it carefully into the tank (which is well forward of the Centre of Mass), finally checking the fuel load with a dipstick. With a heavy student, the fuel load had to be low and this caused an aft C of M. Hence stalling and spinning were markedly more lively than with a lighter student, more fuel and a forward C of M.

I thought that the T67A was excellent for teaching stalling and spinning, but awful for teaching aeros as too much time had to be spent milking the throttle to stop the engine from over-revving. It also has an utterly appalling roll-rate; nothing like as good as the Bulldog. Hence you only ever see vertical or flick maneouvres at air shows; large aileron deflections merely cause aileron snatch and buffeting. How on earth this thing was ever accepted for military training (beyond the very basic stage) is quite beyond me!!

FIREFLYBOB
 

IS THAT YOU WRT????


HAPPY SPINNING


RJS:ok:

Could the altitude the Americans operate their aircraft have an effect. I wonder what altitude they start their spins if the aerodrome elevation is 8000ft!.... add 3000 for safety plus 5000 for possible doggy spin recovery....16,000 feet. After half an hour perhaps they are starting to forget how to recover.
Do they operate on oxygen?
I seem to remember BH having at least one bail out.
Once in crew room listening to the account from the instructor.
Student got out easily, he being held in by g force, had to drag himself off the wing...so he said.
The final report i seem to remember said it was a sloopy spin entry by student and recovery. Report suggested go back to pro spin then standard recovery.
Held me in good stead one day in a Terrahawk.:O

Thinking about buying a Slingsby Firefly from RAF - would be interested to hear any firsthand experience from anyone who operated them in following areas...

1. Serviceability eg typical faults, time in maintenance etc

2. Fatigue - has the RAF thrashed the engine + airframe to near exhaustion

3. Atypical handing characteristics (other than spinning already covered)

Nb I have operated an ex-RAF Bulldog so comparisons between the two would make sense also.


Thanks- Barney

Barney, they are very good aircraft and from the estimate mentioned when I spoke to the vendors (£50 - £100 k depending on hours) a very good deal. I don't know exact figures on maintenance but in the last 2 years at Church Fenton we had very few faults and the only major issue ( a tailplane bracket mod) has been done on all the aircraft. As to fatigue, the aircraft have been serviced and maintained with no expense spared, down to checking the oil every 25 hours rather than 50, and the way they have been flown in service is much, much kinder than at a normal club ( how many times have you seen people start up and taxi within about a minute, oil cold as a dead fish - never happened at JEFTS) plus the operation of the engine with mixture fully rich all the time means they have not been overheated, nor have they been shock cooled. Handling is the dog's bollocks, although I haven't flown a 'Dog so can't compare ( but they are better than a Tutor in virtually all respects), but there's no substitute for hp and they have plenty! For what we used them I don't know of a better aircraft and if I had the dosh I would be buying a couple.

Thanks for the input DB6, for a relatively young + well looked after aircraft the Firefly seems good value.

Another quick Q - what was the average fuel burn for GH sorties, plus navex's if different?

Cheers

Barney