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Elite 1K Joined: Jan 31, 2004 Posts: 1563 Status: Offline

Wellllll....THIS certainly got my attention! Caught it on the Alert 5 news board. Excerpted from the article:

Quote:

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.

So..like...jeez. The jet can restart itself without the driver even bein' alerted? Cool

I guess we can scrub the airborne restart procedure from the training syllabus then, huh? Wink

(jk)

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Forum Veteran Joined: Dec 14, 2006 Posts: 505

Wow that is cool and something else I was ignorant of. No wander they are willing to fly it so slow, evidently if it flames out it can restart before it loses much altitude.

F-16.net Editor Joined: Aug 23, 2003 Posts: 1766

Noticed this story last night and posted it as F-22 nearly crashes during SDB flight testing

Asif wrote:

Noticed this story last night and posted it as F-22 nearly crashes during SDB flight testing

"Nearly crashes" might be a little bit too strong a description / title if the pilot never even realized that the aircraft had a problem. F-16.net isn't CNN, we don't need to be jumping to sensationalism here...

Mike

Elite 1K Joined: Jan 31, 2004 Posts: 1563 Status: Offline

MKopack wrote:

...F-16.net isn't CNN....

And I thank the dear Lord above (and the Janitors of course..) for that every time I come in here... Wink

But yea verily, puzzled I am at what kinda "trim" would cause a flameout. The thing's gotta have some kinda FADEC or DEEC, right?

Hmm, do the air intakes have moveable parts (ala mig-29 and f-15c) that could possibly cause a flame out?

F-16.net Editor Joined: Aug 23, 2003 Posts: 1766

MKopack wrote:

"Nearly crashes" might be a little bit too strong a description / title if the pilot never even realized that the aircraft had a problem. F-16.net isn't CNN, we don't need to be jumping to sensationalism here...

Mike

Take your point. Adjusted it to bring it more into line with what happened. 'F-22 flameout during SDB flight testing'

Elite 1K Joined: May 26, 2005 Posts: 1152

"nearly resulted in a potential crash"? Weasel words detected... After reading the story, it seems that the flameout caused a loss of telemetry while the a/c was descending, leading to a scare for the engineers on the ground.

Some important questions still remain unanswered...

1. What do they exactly mean by "trim"?

2. Why was this incorrect "trim" not adjusted (glitch?) by the FBW FLCS prior to it causing an dual engine flame out...?

So the guy basically turned upside-down then pulled the nose up, with SDBs inside and in a low altitude ??? Boy, they test every possible and impossible (= tiny probability of actually used) maneuver in Eddie, don't they Shocked

PhillyGuy wrote:

Why was this incorrect "trim" not adjusted (glitch?) by the FBW FLCS prior to it causing an dual engine flame out...?

LinkF16SimDude wrote:

..puzzled I am at what kinda "trim" would cause a flameout. The thing's gotta have some kinda FADEC or DEEC, right?

I think the "trim" they are talking about here would be fuel, not aircraft or engine.

Yes the F119s use full-authority computers for control that are redundant. Fuel-flow "trim" would be autonomous given any condition inside the flight envelope of the engine. Cool

FBW FLCS "trim" would keep the aircraft pointed in the right direction at the requested attitude in a similar manner; right?

But, what if your fuel was out of balance or you didn't have the proper quantities in the tanks/cells that directly feed to the engines? Shocked

I'm guessing here, but wouldn't both engines would suffer fuel starvation?... Shrug

In an F100-PW-229 with a similar starvation issue, the engine would still be spinning, hence the Main Fuel Pump would also be spinning along with the engine's generator. The generator would provide power for the DEEC, and ignition system, while the pump would give positive fuel pressure again to the main fuel control once the supply had been re-established. With the throttle anywhere above IDLE, the engine's ignition system (which is pressure suppressed) would come to life after a drop in combustion chamber pressure. The return of fuel flow would relight the engine automatically, and a "engine die-out" fault would most likely result on the pilot's MFL listing... Cool

Problem solved... engine running no harm done except to flight suit...
Nothin' too it....

Keep 'em flyin' Thumb

Excuse the double post, but I found this in an old "Code 1" magazine article... "Flameout" - By Joe Bill Dryden — Senior Experimental Test Pilot.

It pertains to the F110-GE-100 (1990) but would reflect in a similar manner for any modern engine. (Fighter or Commercial)

It illustrates a point about flame-outs in a modern fighter. (Esp DUAL flame-outs!)

From "Flameout" - By Joe Bill Dryden — Senior Experimental Test Pilot.

Quote:

One large impression that I had was how tenaciously the engine will cling to life if it has fuel. On one test, we had artificially closed the master fuel shutoff valve to only five percent of capacity, that is, ninety-five percent closed. (There is no way that you can do this in your airplane without some really weird failure, or a plumbing change like we had for the purposes of this test.) The boost pumps were off and the refueling door was open so the system was depressurized. The engine was in idle and running just fine. The test point called for me to snap-accel the engine to ninety-five percent. The engine only briefly touched ninety-five percent, immediately rolled back to ninety-two percent, and hesitated there for a few seconds. It then rolled back to about eighty-seven percent for a few seconds. Subsequently it flamed out, but had an automatic restart accomplished in time to catch the rpm at eighty percent. It stayed there for another few seconds, and then flamed out again. The engine then auto-transferred to secondary engine control, or SEC, and got another auto restart at seventy-two to seventy-three percent. It maintained this condition for a little while and then flamed out again, with an auto restart in SEC at about sixty-five percent where it stayed for a while and then slowly continued to decay toward zero rpm. From this, and other similar runs, I feel that if the engine is operating properly, you have little fear of its quitting as long as the aircraft is providing fuel.

The whole article is available here: http://www.codeonemagazine.com/archives ... index.html

I remember seeing a flameout on the trim pad. We had a new run guy snapping for max aug to idle and accidently threw the throttle into idle. The engine started spooling down. Any normal run guy would have let it just stop, but he however on the other end threw the throttle back into idle about 7 seconds later. I litl right off but slowly crept back to idle speed. Kicked out a flameout fault. It had us laughing for a week. When we looked at the scans when the fault kicked, the fan was at 65% while the core was at 30%. Crazy stuff.

I saw a compressor stall the other night when going over the horn to burner. It was, how do I say, a bone jarring experience. The flame lit for a half second, the motor shut off for half a second and then......BOOOOOOM!!!! That thing made a huge thud and shot about a 40 foot flame out the back. Scared the hell out of us, we were standing right next to the nozzle trying to get pics on our cells. Looked like the guys in the cockpit were ready to pull the D-ring haha. We shut it down and laughed for a couple minutes, then made sure the a$$ end of the jet was still attached. Cool experience

Elite 1K Joined: Jul 20, 2005 Posts: 1035 Status: Offline

The 119's have dual FADEC per engine. This story sounds VERY odd in that the pilot didn't notice the power drop. Not to mentention this:

"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."

--VERY odd that he would make that statement when previously in the article this was stated:

"However telemetry transmitted back to the ground station monitoring the test gave away the problem as there was a momentary power loss recorded in the signal. This information was only discovered in the post analysis of the flight data."

--Only discovered in the post analysis of the flight data sure sounds like NO ONE noticed the event at the time it happened. I think this incident was blown way out of the water if you ask me...it was a non-event. The dual FADEC's per engine are in authority here and if the computer detected a stall or other event, its possible that this needed to happen (re-light). Either way most testing does not occure at "low altitude" and certainly not below the set hard deck for the tests.

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