Category Archives: AircraftTroubleshooting

F900EX Generator traumas

Current troubleshooting: engines running:

  1.  Check for Bleed leak blowing on GCU.  BE very carefull if you elect to run the AI on the ground.  !!!!!!APU BLEED OFF!!!!!!, slats extended.    20 seconds ground test max. leave the slats out to cool.
  2.  Test “E” ground quality.  Fluke on volts.  Black lead to airframe ground, red lead to GCU Black test point.  Very small voltage~ .1v.  less is better
  3. Volt drop on line contractor.  Fluke meter on volts.  Red lead on upper contactor, bottom big bolt, black lead on same contactor, upper big bolt. Very small voltage~ .1v.  less is better.
  4. Ripple test.  use fluke MIN/MAX.

Run each test with only 1 gen online, 50 to 100 amps load, try to hold conditions quite similar for each test.

some other thoughts:
look at big E terminal, small 20awg terminal.

double check each  GCU voltage. Is it stable at 28.5? is it stable with load? is it stable with RPM change?

select cockpit red switch to off.  Is the voltage of a running generator, cockpit switch selected off,  .7v to 1.0v at idle? this checks the quality of the permanent magnets inside the Generator.

ASSURE that NO ENGINE GENERATOR  has a cooling fan installed. (possibly a borescope through the black sooty outlet.) or it mat be necessary to unbolt the cooling exhaust.

Initial problem definition:

#3 Gen Light occasionally, Much troubleshooting. Gen 3 amps tend toward zero. #1 seems to “take the load”



#3 gen troubleshooting, #1, #3 gen shunts…..?Removed?

Detailed summary of troubleshooting:


Old Auxilec presentation:




Westwind pressurization problem











The valve opens correctly with shop air applied, and the controller  disconnected, and slight vacuum applied to control circuit





Front valve will open when control i connected straight to the pneumatic relay.




Ground prepress seems to work correctly





Aircraft pressurizes hard on the ground, straight to 3 psi at idle.  Fwd valve will not open via the controller.


Turns out the limit valve was failed.  It had opened because the pilots got the cabin to 17,000 feet.  Then the brass seat fell out of place.  Then valve leaked from then on .





Removed failed altitude limit valve PN 102466-1  SN 88-2322.  Installed serviceable valve received on form.   PN 102466-1   SN 17-1898






Removed failed anti-ice pressure reducing valve PN 38E59-1D  SN 2907 -U. Installed Ovrrhauled valve recieved on AVITECH W.O. 1021932 PN 38E59-1D  SN RF3502.







Ferry trip NC to TX

C 172, N79945. 1969 CESSNA 172K SN 17258272







#1 70psi, #3 62psi,

Baffles are rough.


G-drive with pictures:




Ron Grandgury Aircraft Service
1 817-771-2195

TCDS  3a12

Min rpm over 2230

Tanner Aviation Services at Harnett Regional Jetport Airport janhar 8400. Manager natalie 910-890-0067

Microtel Inn & Suites by Wyndham Lillington / Campbell Univ R2370024401


Hotel lillington

Selling Agent: Scott Tanner, Tanner Aviation Services Inc
559 Airport Rd, Erwin, NC 28339
Phone(919) 604-4307

Hartnett Regional KHRJ

Hobbs 26824.

Off 7.32


Spot Tracking :


Union County – 35A non-towered 8648778275

  1. On 8.30. 17 gsl $63.75 reads 6qt. Add 1 qt. Reads 7 qt.

Off 10.04  tach 70.1, hobbs 26847

Airport 4M4 , ON 11.15A

OIL 6.5 ADD 1 TO 7.5

GAS 17.19HSL 67.90$

OFF 11.55


OFF2.49 TACH 72.8 HOBBS 2687.7


M40 off 7.18a tach 74.1 hobbs 2689.7



Okolona.  5A4. 9013688453


HAMBURG AR.  Crossett jack stell field KCRT 901 368 8453

On 9.40

Off . 10.10a tach 76.3 h 2691.6

Williams 3f3 off 12.40 tach 77.9 hobbs 2693.3



Gdj 3.00 hobbs 2695.7





long push on power

for tracking , RT Button foot print. two lights flash together.