Learjet Summer 2007

• Intermittent Problems with your VG-301?
• Aging, Engine-Driven Hydraulic Pumps
• Incorrect “PRI TRIM FAULT” CAS Messages

Intermittent Problems with your VG-301?

— Rob Cline, HSI/FD Team

When fixing older equipment, one common squawk we see is the intermittent failure of the VG-301. A common culprit is the AM-101 Servo Amp. A quality piece for many years, the most frequent flaw in these classic amps is the original soldering. Over the years, it just gives out! The good news is that a reputable shop can fix it and keep it flying for years. If you suspect the AM-101, call us for troubleshooting help!

Aging, Engine-Driven Hydraulic Pumps

— Karl Detweiler

Duncan Aviation technicians have recently observed that aging, engine-driven hydraulic pumps have shown increased wear issues that demonstrate themselves in leaks, worn splines and shortened life spans. Operators have several options for dealing with these pumps including normal repairs or overhauls.

Duncan Aviation and Parker Aerospace have developed a program that rebuilds the ABEX engine driven pumps to new specifications at overhaul. The pumps meet more stringent manufacturer conditions than normal overhaul requirements. These pumps are then supplied to operators with a full five-year warranty.

For more information about this program, just call 877.PCS.QUIK (877.727.7845) and ask for Jerry Cable at ext. 8112 or Larry Stewart at ext. 4204.

Incorrect “PRI TRIM FAULT” CAS Messages

— Dave Schiver

The 45 “E-Tech” tool is a very good source for Learjet 45s. However, Duncan Aviation technicians have discovered some issues with the PRI TRIM FAULT CAS message.

During the ring-out procedures, please take note of the following corrections: These have all been verified with the 45 Wiring Manual.

• Step 3.C.2. “Measure voltage at A9BP1 pins 82 and 84.” It should read A9AP1.
• Step 3.C.3. “Measure voltage at A9BP1 pins 83 and 84.” It should read A9AP1.
• Step 3.D.2. “Measure voltage at A9BP1 pins 85 and 87.” It should read A9AP1.
• Step 3.D.2. “Measure voltage at A9BP1 pins 82 and 84.” It should read A9AP1.

Duncan Aviation found another discrepancy in Step 4.G. This step says to “Ring out A9BP2 pin 87 to A65P1 pin 10.” During a routing maintenance event at Duncan Aviation, we could not find pin 10 on A64P1. As with ALL discrepancies, this was researched in the Wire Manual and NO reference to pin 10 was found. Although the manual makes no mention, pin 10 is there and you should follow the procedure in Step 4.G.

Diodes Certain steps will have you check for grounds. That would be fine if it was mentioned that a diode is in the path since that will ring out different. Good luck and happy troubleshooting!

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