Shola

Hello experts. We also have an APU that quits after running for about 8 minutes. Any idea what could be responsible for this discrepancy?

11 hours ago, pjvr99 said:

you didnt mention replacing aux start relay and fuel holding relay. try that. also

try replacing 110% overspeed solenoid on back of apu.

 

back to ignitor: can you hear it firing?

We replaced both the aux start relay and the fuel holding relay. We also replaced the centrifugal speed switch (110% overspeed switch). We heard the ignite firing. We even saw the spark before installing it back into the combustion chamber. During one of the attempts, the APU rpm rose to 32% and got stagnated. The combustion chamber was also hot indicating some combustion. However,  the APU couldn't self sustain its operations. We have replaced virtually every component from FCU to oil pump to atomizer. We are however not sure of the integrity of the ignite as we do not have a new one in store. We have placed order for new ignitors for further troubleshooting. Thank you all for your contribution. I think we all can learn one or two things from this experience after we might have succeeded. Meanwhile,  kindly keep your suggestions coming.

Thank you very much. We replaced the atomizer. We will replace the auxiliary start relay.

Hello guys. GTCP85-180L does not fire. It does not go beyond 20% rpm and there is no combustion. We have replaced FCU, oil pressure switch, oil sequencing switch, centrifugal switch, igniter plug, exciter yet no combustion. It just rolls but never achieves combustion. Any help please.

37 minutes ago, Ahmer said:

 

Thanks for the diagram 

18 minutes ago, Ahmer said:

If u propeller feather or unfeather on ground its means u switch is working, u said ur rpm rewind at 60 % rpm .its mean when u restart engine ur prop angle changed( from 92degree towers flight idle) and prop start rotating .go to an other option it's means switch & circut good properly working .u check other option because rpm not sustained ur engine.sometime malfunction of td system at auto .regards 

 

Thank you very much. 

38 minutes ago, Moeed hassan said:

may b SHOLA is talking about AIR START CIRCUIT.... because air start switch is not in valve housing.....

 

NOT SURE BUT MAY B THIS SWITCH IS AVAILABLE IN ELECTRONIC VALVE HOUSING.... 

46 minutes ago, Ahmer said:

There is no air start switch in valve housing, condition lever air start position is is used during propeller hydraulic servicing , prop rigging on ground and air start the engine in air. The micro switch in condition lever actuate the prop aux pump motor when we select the condition lever to air start.

Thank you very much. I saw a diagram of the valve housing showing air start switch. Hence, my curiosity. 

I know there is an air start switch in the valve housing. Could this be the cause of the engine failing to air start? Can anyone explain the function of the Air Start switch in the valve housing. Thanks. 

18 hours ago, Ahmer said:

Moeed Hassan, u r right most probably chance is 50 psi pressure switch cause of flame out.

Hello 

We just completed the ground run. The fuel enrichment system worked ok. Engine rigging ok. Engine performed well during ground running. What else could likely be the problem? Thanks for your time.

11 minutes ago, Ahmer said:

We checked all tank cap seals and replaced RGB as I written above but result is same , and there is no external scavenge pump of RGB.RGB have two scavenge pumps main & nose scavenge pumps which are inside the RGB.

Forgive me for the mistake. I actually wanted to refer to the main RGB scavenge pump. The nose scavenge pump is probably to remove oil back to reservoir when the aircraft is nose down. If the fault is with the main or nose RGB scavenge pump,  then, it was a good decision sending the engine for general overhaul. 

6 hours ago, Ahmer said:

Shola, the problem is not on ground & normal level flight, problem is start with aircraft escanding (nose up ) in flight.engine start oil lose.engine run several time on aircrft/test cell.all suspected components replaced result is same in flight.oil pumps both p/sec, heater strainer, scavenge filter,and RGB .finally engine send for GOH.

This problem you described could be as a result of bad oil tank cap. Many a times, the gasket for the oil cap may be worn or the cap not properly locked in place. During flight and with pressure differential between inside the oil tank and outside the tank, coupled with the venturi effect of the drain system, oil could be sucked from the reservoir to the drain during flight. Another possible cause might be a failed RGB external scavenge pump. Unfortunately,  the overhaul centre might not tell you the real problem. 

On 10/22/2018 at 5:15 AM, pjvr99 said:

Lockheed Service News V18 #3 contains a brilliant explanation of causes and troubleshooting

of oil dumping. It was later made into a service bulletin. I suspect you may be looking at RGB 

scavenge failure

 

We had a similar problem on our aircraft.  The engine was dumping oil in flight. Using ghe Lockheed Service News pjvr99 spoke about, We ascertained that the problem was due to oil accumulation in the accessory drive housing. As recommended by the Service News, We ran the engine at cruise power for 30 minutes. At the 29th minute, there was oil dumping as highlighted in the Lockheed Service News. We therefore confirmed that the problem was due to inadequate scavenging of oil back to the reservoir. You need to run the engine for minimum 30 minutes for the dumping to begin. We replaced the main engine oil pressure pump as well as the external scavenge pump, both on the accessory drive housing. Please note that you must bleed the main oil pumpbafter installation by loosening the back vent of the pump and then motoring the engine until oil gushes out of the bleed point. This procedure  solved the in-flight oil dump in our case. You may wish to try same.

The connector to one of the blade antennas on the vertical stabilizer was found removed. Connector tightened back and system checked and found ok. Apparently,  there was no signal from one of the 2 antennas to the receiver.

60% rpm. Suddenly,  engine wound down with all other parameters following. Remember that after landing,  engine started normally 

Please i need help.

#2 Engine failed to air-start. Engine wound down from 60 percent rpm. On landing, engine started normally. NTS switch and NTS brackets checked ok. Pump housing oil quantity normal. Need help to rectify the fault. Thanks.

On 10/21/2018 at 3:15 PM, NATOPS1 said:

I think I would make sure before I task my maintenance with two engine changes.

Hello NATOPS. Surprisingly,  the throttle creeping has stopped after we swapped the engines. The aircraft has been scheduled to go for functional check flight. I will let you know the outcome of the FCF. Thanks. 

Gentlemen, I regret to inform you that after ground run of the engines, the creep came back. This is even after replacing the valve housing cover. Our next plan is to swap engine 1 and 4 to see if the problem will transfer.

Thank you all for your suggestions.  Based on your advise, we replaced the gimbal assembly and carried out rigging of the propeller. The throttle lever creeping has stopped. Again,  thanks for your time. 

Thank you very much. 

2 hours ago, pjvr99 said:

check gimbal assembly - something is worn out

 

Thank you very much. We will install a new gimbal assembly this morning. I will let you know the outcome. Once more, thanks a million. 

Please i need help.

We recently encountered an uncommanded movement of the #4 engine throttle lever from ground idle to just before the gate of flight idle. We checked and confirmed that the cable tension is ok. We also cleaned and greased all bell-cranks. Yet,  the problem persists. Once the throttle is moved from the ground idle, it creeps forward until it reaches the gate of flight idle. Any advise would be appreciated. Thanks.

5 hours ago, casey said:

That's just it.  Asking where someone is from based on their use of a word that is not common where you live is not derogatory.    I did read Larry's comment (I think tiny's curiosity was aroused as you used a word much different than what we use to describe a system malfunction) and again, there is nothing derogatory about being curious about someone (where they are from.) The rest of his comments are clearly an attempt to placate you . I also understand that English is not everyone's  native tongue and that  underscores my point that we should not assume intent.  Trust me, if I it appeared that Tiny was being derogatory toward you, I would have given him the same type of warning.   

We are happy to have you here, to have you contribute to the community and to help you where we can. With that said, please keep in mind that we all have the responsibility to keep our emotions in check and to not assume mistreatment when there is no objective evidence to support our stance.    

 

--Casey

 

 

Thanks. 

1 hour ago, casey said:

@tinyclark has been a member of this site since its inception and based on more than 10 years of history, it is a safe bet that he did not intend to insult you.  I am sure that he knows the meaning of the word "snag" and does not need to look it up in the Oxford Dictionary.  Furthermore, I am quite certain that one cannot find the answer to what he was curious about (Where are you from?) in a dictionary.  Assuming the intent of another is never a good practice, neither is causing drama in our forums. 

You have been warned...

--Casey 

Thank you very much Casey. It is true I am relatively new here compared to tinyclark who has been a member since inception. Nevertheless,  I take exceptions to someone asking me derogatory questions. Read his comments again and  read Larry Myers objective intervention. I still believe tinyclark was unfair to me. I am here to learn and not to cause drama. Furthermore, it is not all on this forum that have English Language as their mother tongue. I think the warning is more applicable to him and not to me. 

Thank you very much Larry Myers. Tiny's question sounds very insulting to say the least. All he needed to do was consult Oxford English dictionary.