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Aero Precision provides OEM part support for military aircraft operators across more than 20 aircraft


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  1. Hi, Thanks again for your reply. Your response is exactly what prompted my question. If I set RPM by the T.O , the unit is seemingly running at 410-412hz so I am puzzled how the unit runs at 400 hz once installed. Mathematically the numbers do not work out: 4292 tach pad RPM x 10.043-1 gear ratio = 43,104 at the turbine wheel. 43,104 / 7 (planetary to gen reduction) = 6,157 RPM at generator=410.5 hz at the generator. Running at max 4311 tach pad RPM puts generator at 412.3 hz I'd really like to hear from a pilot or crew that can confirm that the unit runs at 410-412 when installed. Perhaps this is normal? Sorry to drone on about this, I am just wanting to get real world information.
  2. Hey, Thanks to all for replies...I have latest (2015) T.O's and also commercial manuals for the GTCP85-185L. Through these manuals there is a lot of conflicting information. Running the unit at 4292 -4311puts frequency at 410-412 hz. In the commercial world, I would expect a phone call right away as a commercial operator wants to see no more than 404 hz. Does the C-130 unit really operate at such a high frequency? What I would really like to know is what do the guys in the cockpit want to see by way of generator frequency with no load? I understand the window of 380-420hz, but there must be something that seems "normal" or desired. On a related side note, our 85-180's for the A/M32A-60A hold 400hz even within +/- 1hz under any condition as they incorporate a clever stepper motor on the fuel control. The 85-180C for the -95 (LASS) cart states 43,300 RPM max by the T.O , but at installation is tweeked down to just around 42,200 -42,500 or else the tachometer reading in the panel looks a bit overspeed. Thanks again for all the input...I am always working hard to maximize these units.
  3. Hi Guys, Thanks..that's a big window for frequency...working an APU in a test cell environment and have the frequency at idle (no loads) at about 402/403hz...with 60kw load applied I am right at 400hz....with full bleed load, temperature maxed at 1170F, frequency is at 396 hz. it sounds like in actual installation this will be acceptable. The T.O only provides a "maximum rpm" for the APU, but never specifies an actual value. My thinking is that you guys like to be as close to 400hz as can be maintained...correct? Tom
  4. Hi, Wondering if anyone can tell me the APU frequency of the GTCP85-180L (H model APU) in a no load situation, basically APU running, no bleed air or electric being used. What is the max variation in the frequency when fully loaded with AC? Basically looking for the frequency at idle and the maximum droop. What window is considered acceptable by by the pilot and crew? Thanks, Tom
  5. Hi, I am wondering if anyone has experience with the A/M32A-95 (LASS cart). My question is not so much C-130 related, but in operation of the airstart unit. We work with these, but not as much as the -60A. The -95's we see sometimes experience intermittent flameouts when coming off load to return to idle speed (60%). I am just wondering if anyone has had this experience? I'd appreciate any comments or email me directly. Kind Regards, Tom Timmermann tom@avonaero.com
  6. Hi, Unfortunately, Honeywell does not produce a "short shaft" to allow use of the -789 repair in APU types with a planetary style gearbox. This repair is used widely in commercial units that incorporate a flat gearbox, not the crossways style on the 180L/185L APU. Your options at this point are: Relpace the turbine wheel with a unit that does not have a plugged shaft (-789) Re-shaft the wheel to restore the spline wear. Remove the plug from the wheel and re-evaluate the wear in the splines. Sorry there is not better news, most of us learned this lesson the hard way..had the compressor / turbine built only to find out the gearbox would not seat onto the assembly. Lastly, I have 3842360's in stock without the plugged repair. Regards, Tom Timmermann Avon Aero Supply Inc tom@avonaero.com
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