Pebbles Posted December 18, 2014 Share Posted December 18, 2014 We have this aircraft with APU start normally on ground but unable to start in Flight. The APU intake door opened to 15 degrees, rpm goes to 30 percent but no rise in EGT. Failed air test thrice. In the course of fault isolation, we have changed out the no.2 aux touchdown relay, door control relay, door closed control relay, ignition unit, fuel control unit, and APU door actuator. Have anyone out there had this experience and know what is the problems. We have decided to change out the APU. But what if it happen again. Quote Link to comment Share on other sites More sharing options...
herky400M Posted December 19, 2014 Share Posted December 19, 2014 Pebbles, we had a similar problem, and if my memory is correct we send it to overhaul/repair, I'll try to trace what the outcome of the problem. try to find out!! herky400M:cool: Quote Link to comment Share on other sites More sharing options...
victorp1 Posted December 20, 2014 Share Posted December 20, 2014 If the OAT is very low and any moister in the fuel filter/strainer it will freeze and not allow fuel to flow properly. I have had this problem but once we were on the ground, even with ground OAT of 0°C, the fuel will flow and start properly. I had this problem on GTC's also, it would not start right after landing but after about 15 minutes it would start and run properly. Quote Link to comment Share on other sites More sharing options...
RavenFE Posted December 20, 2014 Share Posted December 20, 2014 What altitude did this occur at? APU's may not start above 20K Quote Link to comment Share on other sites More sharing options...
howell fe Posted December 22, 2014 Share Posted December 22, 2014 Is it a GTCP85-180L? Run the H296G APU tester on it, should pinpoint the problem(http://www.howellinst.com/H296B.htm). Quote Link to comment Share on other sites More sharing options...
neelamagam Posted April 10, 2015 Share Posted April 10, 2015 Hi Neela here, We had the exactly the same problem. Several flight attempt to start APU if flight fail. We have replace amost all components and even changed the APU in two occasions, but still unable to start in flight. Ground checks are satis. On ground we are able to start, we even jack up the aircraft, to simulate in-flight condition. APU can start. Can anybody shed some light on this problem Quote Link to comment Share on other sites More sharing options...
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