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Upwardbound
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I have a question and a discrepancy... it is dealing with engines and electrics.

MC-130(M)H

Trying to determine if this is a discrepancy or normal ops. During an engine run the throttles were pulled back kind of fast (from 1077) cnd if throttles are at 1010. This intermittently causes the gen out lights (1, 2, and 4) to come on. It never happens to #3 gen, and rarely happens (to 1, 2 or 4) w/ temp datum in null or locked. It is almost w/o fail to see it illuminate 1, 2, and 4 w/ td in auto. Other possible discrepancies (when pulling throttles back) include VDT's flickering, and f/d and c/c thunderstorm lights dimming and brightening. Is there T.O. info for pulling throttles back too fast?

Edited by Upwardbound
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Sounds like a problem on the main and essential AC busses. Generator out light should only

come on when the frequency falls below 380Hz (95%rpm). If the rpm actually fell that low

during a throttle back from 1077° to 1010°, it would be my guess you'd more than likely have

a flame out ....... in which case the generator out lights would be on :-(

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Hi,

Abnormal electrical high load imposed on generators at a moment of weakness leading them-in sequence of bus shifting-to momentarily get-out then recovered.

1- Check for abnormal load on generators especially on (No.2).

2- Check also TRUs for high load.

3- If high load is present check the cause.

4- Reduce the load to the minimum and recheck.

5- Switch off one generator at a time and recheck. (If equipped use the APU gen. to take ESS.AC and recheck)

6- Swap voltage regulators and recheck. (No.3 with No 2)

7- Switch to “null” TD control one at a time and recheck.

Hope the above will help you moving closer to the defect.

Edited by tenten
Adding a step point.
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"During an engine run the throttles were pulled back kind of fast (from 1077) cnd if throttles are at 1010.

"kind of fast" would that be less than 1 sec?

cnd (and)? 1077 "and" 1010...right?

This intermittently causes the gen out lights (1, 2, and 4) to come on.

It never happens to #3 gen, and rarely happens (to 1, 2 or 4) w/ temp datum in null or locked.

Ok a few things peak my intrest...

1. Do an engine run and see what your TIT is "before lights out" at crossover... and then see what the correction is after fuel correction lights out.... I would think 1, 2 and 4 fuel controls are lean and you will see an increase in TIT @ cross over.

Number three is equal or rich...

If so when the throttles are retarded below crossover you "take" fuel away (lean fuel controls) and the engine slows down in addition to the higher blade angle (cant decrease fast enough). Once RPM is below (sensed rpm) 380 or 368 the freq sensitive relay opens and your contactors start to switch, hence the blinking and diming of your lights...

Once RPM stabilizes rpm ABOVE 368-380 GEN OUT LIGHTS off and back to normal...

As to the reason they (gen out lights) do not illuminate in locked or null is due to the fact you have eliminated the corrected fuel schedule (increase in fuel for a lean fuel control) so when the throttles are retarded below crossover there is no reduction in fuel and thus no reduction in RPM.

As far as a T O that states the time frame for throttle movement, read the throttle quadrant for it is written on it "no less than one sec"...

I would say this is a "NORMAL" occurance if once the throttles are at Flt Idle all indications return to normal.

Normal due to a too rapid of a throttle movement coupled with a lean fuel control..

What I would do is check your fuel controls for a lean condition, set null start temps at 810 (most open "highest fuel flow setting" ) and retard the throttles IAW the placard see what happens.

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The throttles are pulled at about 1 second. I understand that the "1 sec" is on the throttle quadrant, but I was looking for Tech data in this matter.

When the throttles are pulled from 1077 to flight idle the rpms (as expected) push the freqs below 365Hz and gen outs on eng 1, 2, and 4 come on.

If pulling from 1010 to flight idle, we can not duplicate the (possible) problem.

Engine 1 is 30 rich, 2 is 35 rich and 4 is around 30 rich as well. #3 is about 5 rich.

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just a question, when this is happening, you guys dont have the APU holding the ESS buss, right? That could explain why you never get it on #3.

i would imagine the tech data for that should be out there with you. has anyone looked in the FE's -1? there very well could be a note in there for this. look in the EP's for rejected TO. let me know if you need/want me to look in it, and i will

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Brothers of “FAST WARDSâ€

(cnd) (we did not carry a C/C.) (ops) (gen) (w/ temp datom) (It is almost w/o fail) (BTW) (VDs flickering) (and f/d and c/c thunderstorm lights dimming and brightening) (Tnx.) (AFAIK)…………

The last one I thought it is a new avionic components and I spent a couple of hours digging net and books till I got it.

Non standard abbreviations on a technical issue lead me and others to misunderstand.

Apologize for me and others for the misunderstanding.

Back to the subject,

Pulling back the throttles “fast†from 1077⁰C to flight/idle according to my knowledge may affect the engine (RPM/ FREQUENCY) and cause it to drop below the limit on the present of one or more of the following factors:

1-TD system (high correction at cross-over)

2-Low pitch stop setting (high setting leads RPM to drop/frequency to drop).

3-FCU response not compensating to fast movement of throttles.

4-Propeller governor control response to fast movement of throttles.

5-Throttle to fuel control linkage miss-rigged (low).

One or more from the above may momentarily leads RPM/FREQUENCY to drop and cross the threshold (365) of generator out light, ….but three engines having the same sickness….!!!

On the other hand a high load on (Ess AC Bus) accompanied by one of the above mentioned may also leads the generators to be “out†momentarily (in sequence of bus shifting) due to the high load at a moment of generator weakness- voltage/RPM- till generators recover voltage/RPM drop.

For the limit of how fast moving the throttles some maintenance T.O. stated that the foreword movement should not be less than 4 seconds, but for the “high ranks†the 400% discount dropped it to only one second (maybe for emergency only).

For the point that the lights are not coming “On†when power pulled from 1010⁰C, I couldn’t explain it technically.

Maybe the third law of Newton…..as he stated: (Hitting the ground from second floor is worse than from first)

Maybe “ten ten†is a safe figure…… nobody knows.

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Here is the latest of our "problem"...

#1, 2, 4 gen outs flicker when throttles are pulled from 1077 to Flight Idle. There has been some improvement. The valve housing was changed on #4 prop and now #4 will not flicker. We are hoping this is the cure to # 1, and 2!

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Just between you and me... and all the other Herkybird members...

3 bad valve housings... NO WAY!!!

one bad sync box I belive.....

Throttle anticipation will start the blades moving in the right direction "Prior" to the change in engine speed brought on by throttle movement.

Reduction in throttle equals a reduction in blade angle "too slow of a reaction" low RPM and gen out lights.

Three BAD valve housings with the SAME issue....?????

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Just between you and me... and all the other Herkybird members...

3 bad valve housings... NO WAY!!!

one bad sync box I belive.....

Throttle anticipation will start the blades moving in the right direction "Prior" to the change in engine speed brought on by throttle movement.

Reduction in throttle equals a reduction in blade angle "too slow of a reaction" low RPM and gen out lights.

Three BAD valve housings with the SAME issue....?????

I'm with NATOPS1 on this. While new VH may temporarily 'fix' the problem, I think it going to haunt you. Another thought came up: when the generator out lights come on, do the lights remain on, or just momentary flicker? Do the generators remain on line?

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As (NATOPS1) said; “Just between you and me... and all the other Herkybird membersâ€....

Do not go for valve housings ($$$) to solve a momentarily flickering of “GEN OUT†to satisfy guys of “one second throttles movementâ€. Use “The 4 seconds movement reference to save the XX,000 $ X3

Yes you may go for “Prop filters†and “Synchrophaser box†-As brothers advise you.

You may also go for:-

-Prop hydraulic level checks.(low level leading to lag response)

-Low Pitch stop setting if at high setting. (High setting will cause low RPM setting when retarding throttles to F/Idle)

-Throttle to fuel control linkage adjustment for adding some fuel.(more fuel more RPM at F/Idle)

In general just improve valve housing response or increase RPM at F/idle position(to avoid the second "hit" beside the one at cross-over).

…..might help.

By the way, are you using the same type valve housing on all the four engines (same part numbers)?

The things that still spin on my head with no answers:

1- If the illumination of Gen.Out lights are due to the drop in RPM/frequency it should accompanied with momentarily shifting of load to (No. 3 Generator) in which at the moment will take only the Ess. and Main AC buses (can be noticed by the increase of No.3 load meter during the illumination of the three OUT lights); therefore the “Bus Off†lights of LH & RH should come “Onâ€/or at least flickers momentarily at that time.

2- The dimming & brightening of thunder storm /dome lights which are powered by main Dc through TRUs through Main Ac bus (No.3 generator) is indication of two possibilities either momentarily heavy load imposed on No.3 generator (left alone to take the load of two Buses) or the cycling of Bus contactors transferring load from one to another and in both possibilities the “Bus Off†lights of LH & RH should also come “Onâ€

Why not any “Bus Off†light comes “On†or flickers…..!!??

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I'm kinda curious if you can duplicate the Gen Out lights using symmetrical throttles only? i.e. 1 and 4 and 2 and 3 rather than all 4 at once.

I'm kinda thinking this could be something that may(or should) be seen more often given the same or similar set of circumstances.

Just for shits and grins put the Sychrophaser(all 4 props) in Mechanical and see if you can duplicate.

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We tried the inverter in DC pos. and we still get the #1 and 2 flicker. On a good note we changed the valve housing on #4 and the problem seems to be fixed. So we tried it (changing valve housings) on 1 and 2 and they are still flickering.

So as it stands when the throttles are pulled from 1077 to flight idle gens 1 and 2 give a gen out light. Gens 3 and 4 are holding strong with no issues.

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