slingsby firefly

[Jetscream 32]

robrob,

Cant help but read into your posts that you never had sight of the POH handbook - you are stating some incredible failures in operating a military aircraft across all levels of responsibility and accountability...I'm sure you might be paraphrasing but if as you are writing that is how they operated the aircraft it is no wonder the USAF had the incidents they had.!
Not wishing to be disrespectful!

[dobbin1]

Could someone post the maneuvering CG limits for the T67? Are they the same for all the variants?

The CG limits for our T67M MkII (160hp version) can be obtained here:-

Slingsby SR Group

No idea if these limits are the same for the bigger engined varients, but I doubt it.

[robrob]

Jetscream, the Air Force had its own self-written operating and maintenance manuals. The pilots studied the flight manual and knew it inside and out. But as mind boggling as it sounds we did nothing for weight and balance--it was never considered or calculated. The other glaring omission is that we never practiced gliding stalls and we never received any "student screws up the spin recovery" training. We got that training on the job and it was eye opening.

I do believe that we were operating the aircraft with the CG beyond the aft limit which would make the aircraft more unstable and more likely to enter and remain in a spin.

dobbin1, thank you for the excellent link. I'm looking at the weight and balance spreadsheet and reading through the manual now.
Baikonour, thanks for the link to the spin testing document. I didn't know the spin testing was carried out at Hondo Texas.

The more I learn about the T67 the more I realize the Air Force did a crappy job of developing the operating manual and the training syllabus for the instructors and the cadets.

[sapperkenno]

The more I learn about the T67 the more I realize the Air Force did a crappy job of developing the operating manual and the training syllabus for the instructors and the cadets.

So maybe a change to your website, and every previous post you've made on the subject blaming the Firefly is on the horizon? You're entitled to your opinions, but it's a shame the T-3a never worked out... I can't help thinking if it had been an American design, all the problems would have been ironed out in time and you would have had yourselves a fantastic training airplane.

[BossEyed]

Originally Posted by robrob

I do believe that we were operating the aircraft with the CG beyond the aft limit which would make the aircraft more unstable and more likely to enter and remain in a spin.

Well, that would hardly seem to be an issue with the aircraft - whatever its design or origin - then.

[robrob]

For those interested this document is a great review of the T67M260 and the Air Force's Enhanced Flight Screening Program's development: https://fas.org/man/dod-101/sys/ac/docs/t3bar.pdf

The Air Force tested the T67M200 in August 90 and tested the brand new T67M260 in August 91.

The report mentions some fatal accidents that aren't listed in the ASN database:

1984 UK Aerobatics "Aerial display; insufficient altitude for maneuver"

1985 UK Spin accident resulting in two fatalities from a "failure to recover." The 1986 Cranfield crash is also mentioned so it's not that crash.

1987 Sweden Aerobatics "Low level aerobatics" It lists the Switzerland spin accident so it not that crash.

1989 Japan "Steep turn after takeoff , rolled inverted."

1989 Turkey Simulated Forced Landing "Wing dropped near the ground."

1989 Turkey Formation "On inside of turn after takeoff, hit house."

1990 New Zealand Aerobatics "No information"

Adding these fatal accidents to the ASN T67 database gives a total of 28 fatal T67 accidents.

Anyone have any info on these unlisted fatal accidents?

sapperkenno, I have updated my T-3A webpage but the T67 still has a god awful safety record. Over 10% of the T67 fleet have been destroyed in fatal accidents.

Well, that would hardly seem to be an issue with the aircraft - whatever its design or origin - then.

It doesn't explain the other 25 fatal crashes all over the world. How about the Test Pilot Instructor that "failed to recover" from a spin in Mojave California? You can't write that one off on "some dim-wit that doesn't know how to do a proper spin recovery."

[The Ancient Geek]

Simple - A low level spin in ANY aircraft is unlikely to be recoverable.
Spin recovery needs a lot of altitude. Only a suicidal idiot would enter a deliberate spin below 5000ft AGL.

[sapperkenno]

Only a suicidal idiot would enter a deliberate spin below 5000ft AGL.

How many T67s have spun in doing competition aeros? Top of the box wouldn't be more than 3500' agl. Granted they're not intending to do more than a couple of turns, but still.

[Camargue]

Ancient greek - 1 1/2 turn competition spins are done from 3000-3500ft, (well that's the aim, entry may end up being in the high 2000's) often with a high rotation element so that thde exit is vertical. the trick is to do it in a plane designed for proper aerobatics, unlike say a slingsby or bulldog. Of course at that height a 'chute is probably not going to help much. I'm sure though slingsby's have been flown in many competitions

[dobbin1]

A 1 turn competition spin in the T67m uses around 1100 ft so spinning from 3000 or 3500 is not a problem if you know what you are doing.

If I am spinning with a student on the controls I always start above 5,000 ft just in case they get the recovery wrong. We always wear parachutes and practice abandon drills on the ground as part of the AOPA aeros course.

In the 10 years I have been flying and teaching aeros in the T67 I have never got into an accidental spin (plenty of departures of course, but always recovered at incipient stage by centering the controls) and I have never had any hint of a problem recovering from fully developed intentional spins. Always aware that the next one might be the first problem one though.

[Jetscream 32]

In summary to 4 pages of pruning - I think we can safely say the T67 is a fine aircraft if you operate it as per the POH and within CG limits.
Always do an AOPA aeros course if you want to have $hits and giggles doing loops, rolls and other fun stuff.
Always wear a parachute
Don't self teach aeros
Simples!

[robrob]

My summary of 4 pages of pruning:

36 T67's destroyed with 48 fatalities in flying accidents. That's the new total using the ASN and Enhanced Flight Screening Broad Area Review report.

Know what you're getting into when you get into a T67.

[RatherBeFlying]

CG and Pilot Position

AFMs commonly give a single arm for the crew positions, even though seats are commonly on tracks.

Parachutes (or more importantly lack of) will also affect the arm.

Many of us single seat glider owners will have the glider CG calculated after weighing with pilot wearing chute and strapped in.

I bought my first glider from a gentleman weighing some thirty pounds more than me; so I had to remove several tail weights. The fellow who bought it from me reinstalled them.

Another consideration is that North Americans, including USAF personnel, tend to weigh more and be taller; so sitting farther back.

[dobbin1]

Originally Posted by RatherBeFlying

AFMs commonly give a single arm for the crew positions, even though seats are commonly on tracks.

Parachutes (or more importantly lack of) will also affect the arm.

Many of us single seat glider owners will have the glider CG calculated after weighing with pilot wearing chute and strapped in.

I bought my first glider from a gentleman weighing some thirty pounds more than me; so I had to remove several tail weights. The fellow who bought it from me reinstalled them.

Another consideration is that North Americans, including USAF personnel, tend to weigh more and be taller; so sitting farther back.

The seats in the Slingsby are fixed position. The rudder pedals are adjustable to allow for taller or shorter pilots, so I don't think the arm of the pilots will change with weight or size. Our w&b spreadsheet gives the option of wearing a parachute. Careful fuel planning is required if you want to fly with two fat blokes and parachutes.

[MikeeB]

Only a suicidal idiot would enter a deliberate spin below 5000ft AGL.
How many T67s have spun in doing competition aeros?

Top of the box wouldn't be more than 3500' agl. Granted they're not intending to do more than a couple of turns, but still.

I did, in BONZO. I normally started at 3500ft, the spin was always early in the sequences that I did during my short foray in to aerobatic competition, so 3000ft for entry, anything below and I'd can it, and did do. It's a few years since I've flown, but I do remember some wise words that came my way, "one day, you'll put in the inputs to recover the spin and it won't recover as you expect, don't start £$%"£$"£ about with it, stick with it and it will drop out" It did it once and completed another rotation and then dropped out. I don't know why, but it did. From memory the FF's are not cleared for inverted spinning, but I had instruction on how to recover from that as well, should it happen. I always flew with a chute just in case.

If/When time and money allows and the kids stop bleeding me dry, I'll start flying again, and I would quite happily fly a FF.

[robrob]

I believe there is duplication between the two reports you mention, so your total is wrong.

Did you compare the two lists? Tell me which ones you think are duplicates.

Is it this one from the BAR report?

1984 UK Aerobatics "Aerial display; insufficient altitude for maneuver"

From the ASN database:

1984 Slingsby T67M Firefly G-SFTY Specialist Flying Training Ltd 1 Torquhan Farm, near Galashiels - Cross country flight, pilot bailed out too low and died.

1985 Slingsby T.67A Firefly G-BJGH Specialist Flying Training Ltd 0 Teesside International Airport, Middleton St. George, County Durham - Nose wheel fell off, damaged beyond repair

1986 Slingsby T67M Firefly G-FFLY Slingsby Aviation PLC 1 Cranfield, Bedfordshire (EGTC) - This crash is in both reports and I accounted for this - not duplicated

1987 Slingsby T67A Firefly G-BIUZ Slingsby Aviation PLC (reg. owners) 0 Cranfield, Bedfordshire - Takeoff stall crash avoiding a midair, no fatality, written off

Here's a screen capture of the ASN T67 accident database:

[robrob]

"one day, you'll put in the inputs to recover the spin and it won't recover as you expect, don't start £$%"£$"£ about with it, stick with it and it will drop out" It did it once and completed another rotation and then dropped out. I don't know why, but it did.

This is the key. That warning should be plaquered on the instrument panel. Sometimes the Firefly doesn't react the way it should.

It's like ghosts, you don't believe in them until you see one yourself.

Was this a right-hand spin? The Edwards test flight guys found the aircraft recovered quicker from left-hand spins. They speculated it was due to prop wash making the rudder more effective. The fatal Academy intentional spin crash hit the ground in a right-hand spin. The Apr 2016 crash looks to be right-hand too.

We should also take note that many of the T67 crashes resulted from stalls, some at low level, some that progressed into spins. In the T67 stall + rudder = aggressive wing drop. That should be plaquered too.

[Cows getting bigger]

This is the key. Sometimes the Firefly doesn't react the way it should.

That is the same with any aircraft if you find that little spot that no one else has experienced, hence my comments on a similar thread about spinning and parachutes.

[India Four Two]

From memory the FF's are not cleared for inverted spinning,

MikeeB,

Read the very interesting report in Baikonour's post:

For those interested, here is a USAF document about spin tests they carried out on the Firefly.

Here's the relevant part:

Inverted Mode Discovery
The possibility of an inverted spin seemed remote, due to the reluctance of the aircraft to depart or spin from an inverted stall. We tried roll coupled entries, but could not generate sufficient roll rate to translate to a yaw rate. The only card left unturned was the effect of the elevator trim (remember that trim tab)--could it make a difference?

We found with the elevator trim set full nose up, the aircraft would spin inverted in either direction. This was accomplished from an inverted stall, with full forward stick and full pro-spin rudder held throughout the incipient stage (1 to 2 turns) and the developed spin. The full nose up setting of the trim tab allowed an extra bit of elevator control power when inverted. This in turn, kept the angle of attack high enough to allow a yaw rate to develop. And as we know, stall plus yaw equals spin.

Follow-On Tests
Naturally, Slingsby wanted to further investigate the inverted spin mode. Their follow-on testing completed before delivery verified the importance of the trim tab for inverted spins. Expanding from the QT&E sorties, they looked at both forward and aft CG, as well as heavy and light aircraft weights. In all cases, once the trim was set more than half nose up, the propensity for inverted spinning increased. The aircraft was more susceptible to inverted spins with right rudder, though it could spin both directions once the trim was set to full nose up (as we had done during QT&E). Slingsby also found the neutral recovery to be most effective for the inverted spin. In the end, Slingsby recommended the aircraft not be certified in this area and for inverted spins to remain a "prohibited" maneuver. In part, this decision was an economic one, as travelling the certification highway can be a long and expensive journey. And on-time delivery of the aircraft was paramount to both the USAF and the contractor.

This is a very interesting report and it merits reading completely. When I opened it, I had expected a typical, dull, factual USAF flight-test report. However, this is a very interesting, well-written paper, presumably presented at a conference. Does anyone have a reference?

I think the summary at the end of the paper is very telling:

Overall Assessment and Impact of Testing
On the USAF side, we were pleased with the Firefly's spin characteristics--how it spun when you wanted to and a when you weren't expecting it. The inverted spin potential seemed remote enough to eliminate most of the worry on part of the user. The T-3A had a no-nonsense, erect spin mode that would expose pilots to the spin environment in a safe and energy-efficient manner. As long as the pilot utilized rudder for primary anti-spin control, most mistakes during recovery could be tolerated.

I've never flown a T-67, but it seems to me, to be not a lot different from the Chipmunk - apply the correct recovery procedure and it will always come out of a spin.

As an aside, but relevant to robrob's comment about W&B of the T-3A, when I flew Chipmunks at UBAS is the 60s, there was never any discussion of gross weight or W&B. I presume the assumption was that even with ex-truckie middle-aged QFIs in the back seat, there was no issue.

[Gertrude the Wombat]

Originally Posted by MikeeB

If/When time and money allows and the kids stop bleeding me dry, I'll start flying again

In my case it was thirteen years until the childcare budget dropped to zero and I could start flying again.