Challenger Spring 2008

• 604 Operators — Unusual Break Wear
• 601 & 604 Honeywell GTCP36-150(CL) APU SOAP Kits

604 Operators — Unusual Break Wear

— Scott Shefke

604 operators are experiencing one brake wearing out faster than the others, fueling some to purchase a temperature probe to track the heat patterns of the brakes at post flight. The brake that appears to be the hottest is typically replaced prematurely. The most common squawk associated with premature brake wear occurs when the brakes are applied evenly and one brake grabs sooner than the others, causing the aircraft to veer to the left or right. The grabbing brake is typically hotter than the rest. However, there is a noticeable difference between the most common squawk and the squawk the 604 operators are experiencing; the aircraft does not veer to the left or right when the brakes are applied evenly, but there is still one brake hotter than the rest at post flight. This leads us to believe the aircraft may have a dragging brake.

Although high heat at post flight is an indication of normal wear for carbon brakes (when there are no other considerations), in this situation there could be another cause for the increased heat. Duncan Aviation has noticed, during post flight inspection, that one or all the brake pucks on the brake in question are not fully retracting, causing the brake stacks to remain in slight contact with each other. This slight touch is thought to be enough to cause the high wear rate that occurs when a carbon brake is cold and not because of the high heat. The higher heat at post flight, may be the result of the brake stacks not dissipating the heat as efficiently as when the brake pucks are completely retracted. Duncan Aviation technicians have been able to improve this situation by thoroughly cleaning the pucks and cycling them through several times; however if enough people report this problem , a solution could be introduced, such as a stronger return spring. The Challenger Advisory Committee is aware of this and is seeking additional information from operators. Bombardier has provided a form asking for details about this situation. If any of this sounds familiar, e-mail me and I will forward the form to you:

601 & 604 Honeywell GTCP36-150(CL) APU SOAP Kits

— Jason Burhoop

The APU on the 604 & 601 Challenger is very important; without it, you are unable to start the main engines. For this reason, most operators place their APU on Honeywell’s Maintenance Service Plan (MSP).

To provide coverage of unexpected maintenance costs, MSP requires you track the health of your APU via the Spectrometric Oil Analysis Program or SOAP. SOAP is designed to analyze the APU oil and oil filter at intervals that coincide with other APU inspections. The SOAP lab can see what metals are found in the oil and filter and determine the wear-rate of the APU components. This provides the means to trend monitor the APU and prevent future problems.

Honeywell SIL APU-49 is the guide to everything pertaining to Honeywell’s SOAP program. At the time of this Duncan Intelligence release, there is an issue with SIL APU-49 that needs to be addressed with regards to the GTCP36-150(CL) APU. Currently the SIL states if you are operating a GTCP36-150 APU to use SOAP sampling kit P/N 831171. This would lead you to believe that P/N 831171 is the correct kit for the GTCP36-150(CL) APU. The problem is the GTCP36-150(CL) APU is a hybrid APU that consists of a GTCP36-100(E) model gearbox and a 150 style Hot Section. Because of this, the GTCP36-150(CL) APU requires SOAP kit P/N 831139, designed for the 100 series APU.

Honeywell is aware of this discrepancy and changes will be made to SIL-49 per a new revision.

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