F-22 SBD testing has a inflight crash scare

Just a post for everyones information. It seem like the F-22 has had a inflight crash scare while testing the SDB (small diameter bomb).

The Boeing GBU-39 Small Diameter Bomb (SDB) began separation tests on the F-22 in early September after more than a year of sometimes difficult work to integrate the weapon in the weapons bay and carry out airborne captive carry tests, Maj Jack Fischer, a USAF test pilot,

Flight tests so far have produced a few in-flight problems, including one particular event that "could have been very bad", Fischer said.

In that incident, an F-22 suffered a brief, dual-engine flameout while performing a negative-g, 360 degree roll with eight SDBs loaded in the weapons bay. The flameout occurred because the aircraft entered the manoeuvre with an incorrect trim setting.
Although the engines restarted before the pilot was even aware of the problem, the momentary power loss dropped the telemetry signals to the control room on the ground.

The control staff lost contact "with the aircraft pointed down toward the water at a very low altitude", said Capt Harris Hall, a programme official. "For a time, we thought the aircraft was lost."

www.flightglobal.com...

I wouldn't of wanted to be in that control room. The fact too that the engines restrated before the pilot noticed is even crazier. So am I to assume there is a programe that does that for the pilot.

The SBD being added is a key thing for the F-22 as it will up its bomb load from 2 to 8 and bring the F-22 into a more multi role framework with the ablity to do more work per sortie and in turn require less missions to do the same job and less aircraft. a key point for a country whos aircraft are becomeing even more expensive.

Wow, the engines fired up again before the pilot knew about it.

Pretty much any other aircraft would of ended up in he drink in a similar situation I would of thought.

1. Incorrect trim setting?

If they mean elevators etc that has nothing to do with the engines - i.e. they are inventing an excuse to cover something else. More likely its the FADEC systems threw a wobbly.


2. Engine 'restart' before the pilot knew about it?

Eh? That would be impossible, unless it was the briefest of flame outs in the combustion chamber only and not really a full 'restart' as such. Sure as hell if the engine STOPS (and by that I mean the whole thing stops turning, LP & HP compressors and by default the related turbines) the pilot will know about it, its simply not physically possible that they couldn't.



3. The fault would seem to be totally unconnected with the SDB, and from that text would seem to be a wider problem with the electronics.

Originally posted by Now_Then
Wow, the engines fired up again before the pilot knew about it.

Pretty much any other aircraft would of ended up in he drink in a similar situation I would of thought.

Any modern aircraft with a FADEC (Full Authority Digital Engine Control) system would have done exactly the same as this - nothing. The engines would have restarted with no intervention.

Originally posted by kilcoo316
1. Incorrect trim setting?

If they mean elevators etc that has nothing to do with the engines - i.e. they are inventing an excuse to cover something else. More likely its the FADEC systems threw a wobbly.

The incorrect trim settings probably threw the airframe into a slew turn rather than the correct path - this could have interrupted the airflow into the engines momentarily.

What is puzzling is why the trim settings were not automatically compensated for by the FBW system?

2. Engine 'restart' before the pilot knew about it?

Eh? That would be impossible, unless it was the briefest of flame outs in the combustion chamber only and not really a full 'restart' as such. Sure as hell if the engine STOPS (and by that I mean the whole thing stops turning, LP & HP compressors and by default the related turbines) the pilot will know about it, its simply not physically possible that they couldn't.

The article says it was a flame out - this would have been handled by the FADEC system automatically.

3. The fault would seem to be totally unconnected with the SDB, and from that text would seem to be a wider problem with the electronics.

From what I have read, the weight of the extra payload affects the characteristics of the airframe, resulting in different handling which needs to be taken into account (the above trim settings as an example).

reply to post by RichardPrice


Thanks for that, thought it was all part of the super dooper avionics.

I

Originally posted by RichardPrice
The incorrect trim settings probably threw the airframe into a slew turn rather than the correct path - this could have interrupted the airflow into the engines momentarily.

What is puzzling is why the trim settings were not automatically compensated for by the FBW system?

Possible - but with some of the angles the F-22 is capable of running at it would have had to been some seriously f'ed up flow!


Yeap, looks like they might have some work to do there. Should just be a software thing though.

Originally posted by RichardPrice
The article says it was a flame out - this would have been handled by the FADEC system automatically.

Originally posted by RichardPrice
From what I have read, the weight of the extra payload affects the characteristics of the airframe, resulting in different handling which needs to be taken into account (the above trim settings as an example).

Correct, but if anything the maneuvers would be slower with the increased weight (inertia)...


I just get the feeling its a gremlin in the electronics and could have happened on any test.

Originally posted by RichardPrice
What is puzzling is why the trim settings were not automatically compensated for by the FBW system?

That is indeed what's puzzling and I suspect it's something that is already being addressed seeing as how this particular event occurred in early September.

Originally posted by kilcoo316
That would be impossible, unless it was the briefest of flame outs...

This particular incident lasted for only a fraction of a second as the system immediately re-lighted itself. This would not produce any noticeable flight characteristics or complete loss of power. The only real indication for the pilot would have been an automated warning system, but that's not clear in this case.

Originally posted by RichardPrice
From what I have read, the weight of the extra payload affects the characteristics of the airframe...

Quite possible as any new configuration requires testing in all flight and performance parameters, so naturally it may cause unforeseen problems. However I do not think that was the key issue in this particular case. An SDB configuration (rack included) weighs significantly less then a load out of two 2K 'class' JDAM's and not significantly more then when carrying six "slammers".

This article covers in general detail why integration for the F-22 may be difficult at times.

Also, when considering trim, the Raptor may have fixed inlets but it does have movable parts within those ducts...

reply to post by WestPoint23

would they ever refer to the ducts and inlets going to the F-119 as being trimmed? if so which I don't think is far fetched I think that maybe what was refered to or is at least possible.