Uncommanded Engine Shutdown

[ddhix]

30 March: Just had a problem with an engine shutting down uncommanded during taxi. This is not the first time this has happened. The crew took it this time because they started back up and it was fine; this engine is a problem child.

If we could get some help on this we would all very greatly appreciate it. If any more info is needed just let me know. Thanks a lot!

Here is some history on it:

25 Feb: #4 Secondary Fuel Pump Pressure Light Illuminated. Changed the Secondary Fuel Pump Pressure Switch, it taxied out and came right back with the same problem. We changed the switch again, along with the paralelling valve and high pressure fuel filter. Ops check good.

01 March: #4 Secondary Fuel Pump Pressure Light Illuminated. Crew said they were down sped for a few minutes, until the FE looked up and saw the light was on. He heard ignitors in the head set, said that TIT was rising with Fuel Flow. He went to pull the Ignition Control C/B and everything went back to normal. They flew 2 or 3 more stops with no problems. We could not duplicate it. We changed the Speed Sensitive Control anyway. Ran to power, couldn't find anything. This was different from the one on 25 Feb because they never had a light problem at power.

02 March: Crew heard ignitors & saw #4 Secondary Fuel Pump Pressure Light illuminated, and RPM rolled back. It Immediately "caught" itself and came back online to 100% RPM. They were low sped for about 5 minutes before all this happened. No cargo or flight deck packs were on and there was no tail wind. We ran it; could not duplicate it. Fuel Control is 80Deg Rich

11 March: #4 Uncommanded Shutdown, changed the Fuel Heater Strainer filter, checked the inlet to FHS, borescoped the engine (checked good), checked the fuel line from the firewall, checked 5th & 10th stage bleed air pucks, beeped the mag plugs, ran it, could not duplicate the issue. Replaced the Speed Sensitive Valve and Low Pressure Fuel Filter. Ran it again, could not duplicate the issue.

[PACAF]

We had this problem on an acft at Little Rock and, I could be wrong but I believe it was acft 63-7775. After the fourth time the DCM decided to have the engine removed and replaced. This ended the problem. The engine was high hours and maintenance kept CNDing the problem, but like you changed many parts. Test stand finally duplicated the problem, rebuilt the engine, including a complete new electrical harness. Never found what the problem was but the engine was put back into the system, never heard of it recurring.

Hope this helps.

[Dan Wilson]

Sounds like chafed wiring with intermittent shorts to me.

Just my guess but I would look at the harness in the QEC.

Dan

[pjvr99]

Two areas to look at here:

1. left hand harness could have broken wires on the speed switch c/plug. Swap it out,

see what happens;

2. a little more difficult to determine, but maybe a bad tower shaft, bearings, or gears. Hook a direct

reading gauge to 5th/10th stg bleed valves, and run the engine. Pressure should be same

as CDP, but could be as much as 10psi lower. The thing you're looking for is flux exceeding

about 5psi. At the same time keep an eye on TIT and fuel flow. excessive or erratic fluctuation

would give an idea

[trev130eng]

I've had a similar problem twice over the years. If the wiring harnesses check out good there is a couple of things you can try. Change the fuel pump assy. The one i took off we checked out on the bench by turning the shaft, sometimes it would turn smoothly and other times it would seize up. The strangest uncommanded shutdown i had turned out to be the T.D. amp. Engine shutdown and wouldn't start. Started in null fine and ran up to full power. Swich back to Auto and engine shutdown. Amp change cured the problem. Good luck.

[pjvr99]

..... The strangest uncommanded shutdown i had turned out to be the T.D. amp. Engine shutdown and wouldn't start. Started in null fine and ran up to full power. Swich back to Auto and engine shutdown. Amp change cured the problem. Good luck.

Had this one too, many, many moons ago .......

[Skip Davenport]

May sound to easy but I remember one I had and it was the NTS plunger --

[tusker]

good day guys!! Oh I like it!...it'a good thread. It makes me feel alive!!

Last summer I finally buried my Herc books in my backyard and now that I am member of this forum, I regret so much!!. I only kept my runup book................................John Boy

[tinyclark]

If the igniters are coming on, then something is definiteluy amiss in the wiring.

Unless someone used the little engine junction box as a FOD or tool holder and forgot to empty it, I would have to agree and R2 the engine.

I always like to go back and find out what was done before the problem initially started. Any corrosion on the Misc connectors?

Was it in for ISO or HSC?

[tinyclark]

If the igniters are coming on, then something is definitely amiss in the wiring.

Unless someone used the little engine junction box as a FOD or tool holder and forgot to empty it, I would have to agree to R2 the engine.

I always like to go back and find out what was done before the problem initially started. Any corrosion on the Misc connectors?

Was it in for ISO or HSC?

[ddhix]

Hey guys, thanks for all the information! I'll definitely be checking out the wiring harness the next time around. Anyone think the geneva loc could have a say in it at all?

I forgot to mention (or just plain screwed it up in the first post), but it is typically only happening in Low Speed Ground Idle; so technically the engine is doing what it is supposed to be doing below 65% with the igniters and starting; so it is catching itself during a malfunction.

I was thinking that the wiring harness could be intermittently FUBAR, actuating the geneva loc only partially (?), sending it below 65%, firing igniters and catching itself, then returning to normal; but then why is it only happening in Low Speed Ground Idle? As far as I know, though, the Left Hand Distribution box contains wires for both the geneva loc, and LSGI solenoid, too.

Thank you again for all the input; ya'll are extremely helpful.

-Hicks

[MAXTORQ]

That would be the first place to look is to shoot the wiring harness , while you are doing this move the cannon plug wires around .

I replaced one once for the exact problem . What had happened was the wires inside the box itself had broke due to vibration and shorted .

80 rich on a fuel control is about at it's end of life too.

You can also test the Geneva Loc with three 9 volt batteries hooked in series , this will give you a good indication if the thing is hanging.:cool:

[Lkuest]

If this problem is only happening in LSGI, and the ignition relay is actuated because of RPM dropping below 65%, then technically what you have is either a Lean Blowout or a Bogdown.

A Lean Blowout is a flameout caused by too-lean of a fuel mixture, usually in LSGI. Possible causes are TD Amp (seen this at least three times), Fuel Control misadjusted (Min-Flow, not to be confused with LSGI RPM) or clogged fuel system (sheared ADH, failed fuel pump/fuel control, clogged fuel nozzles).

A Bogdown is a condition usually caused by too much fuel in the Fuel/Air mixture caused by an eroded compressor blades and vanes, eroded turbine blades and vanes, air leaks in the bleed air system, dirty compressor, FOD damage, excessive propeller blade angle, Speed Valve malfunction, or dirty or clogged pressure probes.

I suppose the Geneva Loc could cause this problem, but if the engine never dies at power, you can rule that one out (engine needs more fuel at power). The NTS plunger is cammed out below Flight Idle, so you can rule that one out too.

If you have access to Air Force Job Guides, I suggest looking at the 1C-130H-2-71JG-00-1 wp 71-00-20 ENGINE POWER LOSS FLAMEOUT/BOGDOWN CHECKLIST.

[topboltsto400]

often overlooked, may be worth it to pop the horsecollar and check out the c/p's. Loose c/p would be along the same line as chasing the harnesses.

Back in my engine troop days, I can remember 3 events caused from the firewall c/p's....

@base X, came in on X shift, other shift changed an engine and were swearing to me that ALL of the Y-boxes were bad....I popped the horsecollar and tightened the Missy's, strange they all worked after that...

different base X, X shift wetn thru a SYNC and 2 V/H's, prop wouldn't do anything electric...I got turn over on the line, went back inside, checked the log book, engine was on the wing ~a month, opened the horsecollar, loose C/P....I left the g081 for them to clean up as well as turn in their parts....

in the desert, crew says no rotation, FE got it down to the horsecollar bleed vlv not opening, good on him. again loose c/p

having said all that, if you happen to find a loose plug back there, you'd want to get in a book and chase the schematic, make sure that plug goes to a component that could cause your symptoms..ie; prop brush block conduit probably won't shut an engine down....validate your find kinda thing....

Sure they're safety wired, and shouldn't back off, but we all know stranger things have happened...

good luck

[NATOPS1]

"Lkuest

If this problem is only happening in LSGI, and the ignition relay is actuated because of RPM dropping below 65%, then technically what you have is either a Lean Blowout or a Bogdown."

Think Lkuest has this one... the RPM is dropping not just the SSC or wiring failing.

I would think if the wiring were to blame there would be other start problems as well (as in NOT starting)

Once the RPM goes below 65% the ignitors fire and the pumps go into parallel and the RPM returns to normal as one would expect.

May want to check your TD Start Limit setting...

If the Start limit is adjusted (too low) or the POT is broken off (has been turned too far) once the RPM is below 94% the TD will take fuel and retard the RPM if the TIT is greater than the setting. You stated the Fuel Control was 80 Rich so that could be compounding the problem.

Also check prop blade angles... when you move the throttle you "command" a speed (fuel) and pitch. If the angles are too high there is not enough "power" to maintain the RPM.

[ddhix]

Hey guys,

Just wanted to give an update. We Y-Boxed the TD Amp, it checked good. We payed a lot of attention to the Start Limiting, messed with all the wires while doing every check; nothing flipped out. We changed the TD Amp anyway. We also changed the J3 cable connecting the Amp and the TD Valve (just in case). Ran it; problem seems to have gone away.

Last time we changed parts for this problem, it stayed gone for 14 days; so we will see. Everything seems good though.

I really appreciate all of ya'lls help. Ya'll are lifesavers.

-Hicks

[Guest]

Ususally LSGI bogdown are mainly SSV problems. However, such situation most likely will be a full winddown and will not restart the engine. For your case, it is more like a Fuel system problem rather than bleed air. If you suspect LSGI is the cause, try telling your pilots to taxi with NSGI instead for a few sorties to see how is it.

[Pebbles]

Try doing a insulation resistance between pin A and B of the Fuel shut off valve actuator (Geneva Loc) wiring connector plug, P18. They should not breakdown as one of the pin goes to OPEN and the other to CLOSE the fuel to the engine. We have encounter breakdown at the LH engine harness distribution box connector plug.

[Allmostsmart]

We had a problem that was pretty close to that and it ended up being the LSGI part inside the fuel control. As soon as we down sped the engine it did crazy stuff. sometimes it would just shut down, and sometimes we couldn't shut it down. ended up changing the fuel control and that fixed it.

[keepemflying130]

Similar problem. Had an engine on incudt. with high tit on down shift. about 850. For other reasons changed TD valve, R/H eng harness and Relay Box. Problem never came back until crew ran prior to delivery. Would not go below 750. Checked all six of the easy nickle dime valves. Nothing. Connected a 30 foot hose to the outled of the ss valve to a gage. My thinking is that the ss valve is bypassing some air...will not see it on start because on coast down the 5 10 overcome the 14 partial and open the valves. SS valve is surely suspect, but home station should be able to r2. Thoughts?