JT15D Engines Summer 1999
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SB 7561R1
Pratt & Whitney recently issued SB 7561R1 covering field inspection and cleaning of the fuel control unit (overspeed valve) on affected Citation 560 aircraft with JT15D- 5A and -5D engines. Some of these engines have experienced no throttle response due to malfunctioning overspeed valve assemblies. The packing lubricant deteriorates causing the valve to become sticky, leading to discrepancy. Removal, cleaning and reinstallation of the valve with different lubricant is needed to alleviate this condition. Duncan believes that compliance with SB 7561R1 at your earliest convenience will provide you with trouble-free engine operation and eliminate one reason for missed flights. Another positive associated with this SB is AlliedSignal Canada’s willingness to defray costs for bulletin installation.
Duncan has completed 20 of these SBs so far. A four to six hour stay is all that is needed to accomplish this SB. Pratt & Whitney recommends the SB be done at the next convenient inspection or 3001450 hours for JT15D-5D/JT15D-5A respectively.
For more info, contact Ken Kuchenreuther in BTL at 800.5252376 or Doug Alleman in LNK at 800.228.4277.
SB 7527R1
If you operate a JT15D-5D engine (Citation 560 Ultra) and your engine is pre-SB 7520 (Modification of rear inner compressor stator), SB 7527R1 recommends inspection of the rear inner compressor stator at 600 hours since new and every 150 hours thereafter on acceptable stators. Applicable engine serial numbers are pre-and including PCE-500230 and pre-and including PCE-JC0296 (excluding JC0291). Inspection labor (one hour) is covered under P&W Commercial Support Program Notification A96029R1 as are parts and up to 50 hours of labor to comply with SB7527R1.
Commercial Support Program Notification A96029 expires on November 30, 2000. Pre-SB7520Rl stators must be replaced at hot section inspection regardless of abradable coating condition.
On preflight, by turning the fan, you may hear stator material deterioration in its earliest stages by listening for scraping noises in the inlet area. In advanced cases, you may not be able to turn the fan. Duncan has replaced 10 of these stators. Parts procurement is not an issue.
For more info, contact Ken Kuchenreuther in BTL at 800.525.2376 or Doug Alleman in LNK at 800.228.4277.
Watch Out When You Check Your Oil Pressure
Oil pressure on the JT15D engine in cruise varies depending on oil temperature and/or N2 speed. Once you settle into a repeated cruise condition, oil pressure should be the same as it was on the last trip. If it’s not and you notice a drop in pressure over a period of time, it should be checked out.
The problem could be the gauge, transmitter or the relief valve, but first look at the oil filter; check it for plugging. Because of air-sealed bearing compartments, some transfer of materials does take place. These become suspended in the oil and are removed by the filter. Cleaning doesn’t remove all particles though, and the filter may have to be replaced. If you use the bottom of the filter bowl as a convenient location for redundant pressure readings, you may be creating more problems. The redundant pressure may be considerably higher than the cockpit indicator. This is because the redundant pressure is read before the filter; cockpit pressure is read after the filter. The degree of error depends on pressure drop across the filter. A gauge teed into the oil pressure transmitter line works better for troubleshooting transmitter and gauge, but check the filter first. If you just adjust the relief valve, you may mask the real problem.
For more info, contact Ken Kuchenreuther in BTL at 800.525.2376 or Doug Alleman in LNK at 800.228.4277.
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