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rpm doesnt estabilize at lsgi in starts whit hot wheather


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hi friends my doubt is about what to do when i start the engine in hot wheathers conditions and rpm doesnt estabilize at LSGI the situations is this :

the engine starts normaly i see good fuel flow, good tit, good air pressure but near to 70% of rpm the engine doesnt estabilize at LSGI and the secundary fuel pump light beigins to flash.then i shutdown that engine and try next start whit de td sistem in NULL and the situation is exactly the same.

i really know that maybe the failure is in the td system ( td valve or td control) or could be the engine fuel control.

i know that the flight manual said if the rpm doesnt estabilize at LSGI you must shutdown the engine but i see some pepople who in this situations retract the throttle so the blade angle of the propeller decrease that way the rpm estabilize or some of them pull the LSGI switch so the rpm rise to normal ground idle and the engine estabilize.Now this techniques not always work in some cases the rpm go down and them shutdown the engine.My question is if there is some technique that we can use to help engine rpm estabilizes instead shutdown the engine.


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Since you said that you are near 70%, then you have already disengaged the starter. You also, from that statment, are above 65%, so your ignition relay should have released and your paralleling valve should be in series.

The thing that throws this off for me is whether or not hot weather has anything to do with this problem. Since you have the flickering secondary fuel pump pressure light, then I'd think that you may have a problem with your speed sensitive control. If the 65% switch is making-and-breaking, it can cause the flickering light.

Is your TIT at that point (nearly 70%) low, normal, or high? Does pulling the LSGI switch up seem to cure the problem?

If TIT is low, then you may have a lean fuel control on the starting fuel schedule. If TIT is normal to high, I'd wonder about compressor bleed valves stuck closed or a blade angle that is out of starting angle range. If starting in normal instead of LSGI seems to fix the problem, then I'd think that you may be developing a failed SSC just because of the secondary fuel pump pressure light. Since the engine acceleration can carry you past the 70% mark more quickly, a bad 65% switch does not have time to mess up your start.

I wish you luck with this one. Let us know what you find.

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Two questions on your problem.

1: what model aircraft are you posting about?

2: is it happening on all engines or the first engine starting off of the APU/GTC?

1 the model of aircraft is the L-100 382g

2 and its happend on the engine number 2 after the engines 3 and 4 have started

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To troubleshoot this type of problem, these are the recommended steps.

1. Inspect compressor for damage and dirt buildup

2. Borescope turbine for missing, damaged, or eroded blades.

3. Removed the Speed Sensitive Control cover plate and ensure the shaft rotates with the prop

4. Check engine rigging and control cables, ensure propeller blade angle reads no more than 6 degrees in ground idle (when measured by rotating blade angle from reverse to ground idle)

5. Ensure there is no excessive play between the prop control drive bracket and the retaining lug (holds the propeller control steady)

6. Check the NTS gap in both places as well as for cleanliness and freedom of movement

7. Disconnect the Compressor Inlet Pressure line and ensure the line is not clogged (do NOT blow air into the fuel control, only the compressor side)

8. Inspect Speed Sensitive Valve filter for contamination

9. Inspect engine for bleed air leaks

10. Ensure acceleration bleed air valves move freely by alternating between air pressure and vacuum and verifying they open and close.

11. Visually inspect magnetic drain plugs for contamination

12. Inspect Fuel Heater/Strainer filter for contamination (if this is clogged, usually you will see a low fuel pressure light for that engine at higher power settings)

13. Disconnect Fuel Heater/Strainer inlet line and inspect inlet for contamination

14. Inspect Low Pressure Fuel Filter for contamination

15. Inspect main fuel line for evidence of constricting flow

16. Ensure the fuel tank boost pump puts out enough pressure

17. Flow test at least two fuel nozzles for obstructions

If you still have problems after all these checks, it is recommended you change the fuel pump. These steps are to troubleshoot a generic power loss, so you may perform the steps you feel are necessary given the circumstances, or only the easy ones followed by a quick runup to see if the problem is fixed. One thought though, if the RPM only stumbles at low speed ground idle, try to perform a Fuel Toppings check. If RPM stumbles there too, you probably have a bad fuel control. Also, don't have a bunch of things stealing air from the bleed air manifold during engine start unless you have at least one engine in HSGI.

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When you start you release the start switch at 60% and at 65% do you see Series (TIT cutback) indications that the paralleling valve opened?

Have you tried to start without low speed ground idle selected? If so did the engine start and stabilize? Did the secondary fuel pump pressure light stay illuminated or flashing above 65%.

It sounds like your TD is not the issue. If you had good TIT then you have no TD issue. You have somewhat proven this by selecting NULL and still have the same issue.

Try and start again, if your secondary fuel pump pressure light is illuminated or flashing, have someone pull the Ignition CBer and see if the light goes out (stays out) and the engine stabilizes.

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