Torque fluctuate inflight

[apexlined]

Today,i have problem no 2 engine torque fluctuate inflight but other engine instrument within limit.

a. what limitation fluctuate for torque?

b. what the correct action to be taken for this malfunction inflight?

c. after landing, i swap the torque indicator with other engine torque indicator but same

malfunction occur. is it the symptom for turbine collapse?

[Lkuest]

a. 800 in/lbs above crossover, 400 below

b. treat it as an RPM flux

c. probably not

I'm assuming you should have a flight manual that covers this situation, but here's what I have on the top of my head:

1. Put Propeller Governing switch in mechanical

2. Put TD switch to Null

Beyond those, you really need to have maintenance look at the problem, on the ground, as it could be a great deal of things. Of course, the amount of flux could tell you a lot. 5000 in/lbs would point to an acceleration bleed valve system failure. If the flux is much less, you could have a thermocouple or two with loose or missing nuts making intermittent contact. If the flux gets worse after selecting mechanical, you could have mechanical valve housing failure, with the electrical system partially covering the malfunction. You could also have internal prop leakage, which may be uncovered by putting the condition lever to air start and looking for the flux to get better. There are any number of things, electrical and mechanical, that could cause this problem, and only a maintenance team looking at total engine performance should troubleshoot a flux beyond the simple fixes in the flight manual. Any other checks beyond the flight manual shouldn't be done in the air.

[pjvr99]

To add to Lkuest, check magnetic plugs on RGB and P/S. Also do a fuel governing & pitchlock

check - unstable fuel flow, rpm would indicate a fuel control failure. If you're going to try

another flight or FCF, close the bleed air valve and see if the problem persists.

A very long time ago, I had an engine that had a torque flux below X-over. The engine was sent

to overhaul, but when it came back it still did the same thing .... but worse. The next time it

came back with the report of a problem with the towershaft bearing. What was happening, it

was intermittently missing a tooth on the gearing, and the speed valve was popping open. Above

x-over, the TD system was strong enough to smooth out the problem. I only knew about the speed

valve opening because I heard an intermittent hiss during a man-on-stand check.

As Lkuest says, there is any number of things independently or in conjunction, that could cause

this. Let us know what you find.....

[tenten]

Since you did not mentioned any other indications beside the fluctuation of torque or any corrective actions taken; I have to ask.

Is there any beating noise during the flux?

Is there any flux on the frequency meter (more sensitive than RPM indicator)?

I never had an “actual†torque fluctuating more than 600 in/lb without the above.

If having any of the above; as brothers advised isolate the defect “first†(before you go farther) by:

TD null, mechanical governing, and bleed off.

If defect not a combined by the above, check your torque meter pick-up and indication system wiring, since you already swapped the indicator.

[apexlined]

Thanks for all information.

tenten,

during torque flux, don't have abnormal sound from that engine. i already check frequency, also stabilize.the others indication looks normal.

from flight manual, under tachometer generator failure. the decrease/ flux of RPM, increase/flux of fuel flow and decrease/ flux of torque simultaneous occurs, place Propeller Governing switch in mech gov.

[tenten]

I don’t know what you mean by the last statement; Do you mean that you haven’t got the authority during flight to shift the prop to mechanical gov because you don’t have any other indications beside the torque flux?

Or do you mean is it possible that the defect is related to a tachometer generator failure...?

Look my brother; one of the “Golden Advice” that I have it from my IFE and it works many many times in isolating the defect is:

When you “get puzzled” of abnormal -power related- indications (Torque, Fuel, TIT, or RPM) “Free Your Effected Engine from any assistant/supporter” (synchrophaser system, TD system, Bleed air regulating system). One by one and check the behaviour.

Bearing in mind that; When removing assistant of any of the above you should be familiar of the normal reaction of each.

Which one you start isolating first…?... Not a big issue, any… If not improving return it back.

Concerning your defect; if what you have is only fluctuating of torque indicator without any abnormality of other indications. I advice to go first for torque meter indication system malfunction.