Help with an APU

[drumwilldrum]

Hello All, 

I have been browsing these forums for some time with great interest - there is a wealth of very knowledgeable people around these parts!

Anyway I have finally bought myself an engine to tinker with, and the eventual aim is to get it running. Saying that I have stumbled out of the starting blocks somewhat in not knowing exactly what is is... perhaps somebody can help me identify it?

The seller advertised the engine as an APU from a Fokker 70/100, the only marking on the engine itself is "GT594" which made me think Garrett, but google yields no match. The oil cooler is marked with an Allied Systems plate. Anyway i've uploaded some pictures for assessment. 

The engine appears to be in very good condition, the rotor spins freely and apart from one open port which appears to be a compressor bleed everything else ancillary wise is in place. My hope is that someone here on this forum can help me with getting it running  .

Thanks
Will

[drumwilldrum]

Sorry i'm not sure if these images are linking correctly? Images can be found here: imgur.com/a/4YvGD

Thanks
Will

[racket]

Its a Sundstrand , they made starters etc etc .

Could you try posting more pics please

[finiteparts]

The generator may say Sunstrand, but the rest of it says Honeywell (Airsearch/Allied Signal).

The inlet and combustor case look like an GTCP36-150 to me. The problem is that so many things change everytime they install/certify an APU to a specific airframe...it leads to a lot of variants that look slightly different. Still, the major elements are there to suggest it is some sort of 36-150.

aerospace.honeywell.com/BGA-Mechanical/

Nice small unit, if the internals are ok. Hope you can get it going.

Good luck!

Chris

[racket]

Hi Will

Thanks for the extra pics , yep , I agree with Chris about the maker ..............looks in reasonable condition :-)

Cheers
John

[drumwilldrum]

Hi Chris and John, 

Thanks for the info - yes i had come to a similar conclusion that it is some variant of a GTCP36-150. Any idea where i can track down a maintenance manual?

There is a large AC Generator coming off the accessory gearbox, which makes up a most of the wiring loom - can i ignore this or will i need to provide some sort of resistance load to it for running?  

In terms of starting i've seen some articles on google suggesting this engine has an analog ECU, but not sure if this for my model or later? Ideally i'd like to make my own start panel but an ECU is beyond my knowledge of electricals. 

Having had a good look around the engine now i've identified the following: Starter - positive / negative terminals that i assume i feed 24V to? Fuel solenoid, again would this take 24V continuous to energise/open? Theres an excitor box underneath the engine which again i'm assuming is also 24v?

So my start list would be as follows (please correct me if wrong!):

Fill Oil tank 
Gravity feed fuel to the FCU
Feed 24V to starter 
Watch RPM's and around 10% feed 24V to fuel solenoid and ignitor
Watch EGT for light off and then cut starter and allow engine to spool to steady state

Will the engine self govern to steady state without an ECU?

There are a couple of sensors i'm not certain on yet from visual inspection, looks to be oil pressure, fuel pressure, perhaps oil temp?

More pictures to follow. 

Thanks
Will

[gidge348]

Hi Will, I am no expert on the GTCP engines but just a couple of observations.

You mention that the engine has a FCU can you get some clear pics of the unit, does it have any form of governor attached? My Tierney ground start unit appears to govern the engine by cutting the fuel to the engine intermittently and is controlled by an external electronic unit.

When starting a turbine engine it is good practice not to cut the starter as soon as you have light off. An engine may light off at say 10-20% but not be self sustain until say 50%+. You can get what is called a "Hung Start" adding more fuel will not increase engine speed it will just sit there at light off speed and get hotter and hotter until bad things happen.

We are all used to piston engines and the general rule that you don't "rev the bags" out of it when it is cold. Turbines need to get to operating speed as quick as possible. The danger points on turbines are low revs (they get VERY hot VERY quick) and at revs higher than the design limit.... "Must have a governor".

[drumwilldrum]

 




Guys are you able to see the pics i've inserted above? A little confused by this insert a URL lark, doesn't seem to show the pictures in the draft post??

[CH3NO2]

This link works: imgur.com/a/4YvGD

Looks great. Hope you can get it working.

[pitciblackscotland]

Have you tried using the upload image window Have a read on Ian Bennett web site he exspains about small APUs and how to get them runing. As for a manaul for it will be hard to find,have a look at my thread on the GTP 70 this may help you out a bit.
jetandturbineowners.proboards.com/thread/242/gtp70-turbine-engine?page=1
www.gasturbineworld.co.uk/gasturbinehandbook.html

Cheers,
Mark.

[drumwilldrum]

Hi Guys, 

Thanks for the various replies/links/inputs all greatly received. 

So after a fair amount of fiddling around with the electricals i've dry started the APU. 

The fuel solenoid, oil pressure switch, excitor box/spark, starter motor all work a-OK. I have removed the oil line to double check oil flow and the circuit is definitely pressurised - there is now a significant volume of oil all over my yard to prove this.. 

The big hurdle I have before starting is the fuel control unit - as mentioned I don't have the manual for this APU, but from what I have discovered it is a hybrid fuel control unit with a torque motor driven by an ECU signal. One online article I read mentioned the hydromechanical control is on its own until around 50% N1 before the torque motor starts trimming the fuel supply.

Here are some images of the FCU and the torque motor:








Now my knowledge of electronics is very very limited, but there are four wires leading to/from the barrel connector, which as a wild guess i'm assuming are 24V +/- to drive the torque motor, and a return circuit sending the position back to the ECU?? Again I'm wildly guessing that the motor will be driven by a changing current from the ECU, but I have no idea if this is a continuous signal, or a waveform of some kind? 

Does anybody have experience with a similar Garrett unit with a torque motor fuel control? I am really at a loss as to how to proceed, as I can't find any information about driving these torque motors or what type of output the ECU should be providing. In addition I can't experiment with the FCU without removing it from the engine, something I'm reluctant to do given everything else seems in mint condition. 

Many Thanks
Will