Citation Spring 1998

• Faulty Readings On Your Step Modulator?
• SB 560-53-23
• AVPAC Is Ready To Serve All Your Parts Needs
• SL 560-72-14

Faulty Readings On Your Step Modulator?

The step modulator is a valve located on the back side of the engine fuel control unit. Its purpose is to keep P3 air pressure to the fuel control constant when anti-ice is selected in order to maintain a constant acceleration time.

It has been noted during post maintenance engine runs that many of these valves do not function properly. Generally, you will not notice any abnormal engine parameters if the valve is not operating. The following procedures will determine if your valve is operating correctly.

With engine operating at idle, select ignition to on. You should see a rise in N2 of .5%. This may also be done by selecting engine anti-ice to on as engine ignition is also turned on as part of the antiice system.

If you do not see a rise in N2, your valve is not functioning properly. This can generally be traced to a dirty or worn out cannon plug on the valve. This requires that the plug be cleaned or replaced. If this does not resolve the problem, then the electrical system or the valve itself may be at fault.

For more information about your step modulator valve, contact Ed Johnson, Tim Klenke, Cecil Sloan or Jon Dodson at 1.800.228.4277.

SB 560-53-23

With our paint, sheet metal and Cessna certified NDT in-house capabilities, Duncan is able to perform a spar-carry-thru upper lug inspection. This inspection and repair can be accomplished with little to no additional down-time during any major phase inspection or modification.

For more info about SB 560-53-23, contact Tim Klenke: 1.800.228.4277 Our Engine/Airframe Road Teams Know YOUR Aircraft Duncan’s technicians take dozens of road trips every year to help customers in the field.

One thing customers like about our road crews is that the same technicians who help them in the field are the same technicians who work in our Lincoln facility.

For more info, contact Cecil Sloan or Jon Dodson at 1.800.228.4277.

AVPAC Is Ready To Serve All Your Parts Needs

Many still think of AVPAC as a parts consignment organization. AVPAC’s scope is considerably larger. We function as Duncan Aviation’s outside parts sales, resellers of vendor supplied parts and maintain an inventory of quality, traceable rotables. Contact any AVPAC parts expert via the ILS or call us at 800.228.1836.

SL 560-72-14

Pratt & Whitney SB JT15D-72- 7527 concerns a loss of coating from the Rear Inner Compressor Stator of JT15D-5D engines. These stators have insufficient adhesion coating.

The SB provides instructions for borescoping the stator commencing at 600 hours. If found to be serviceable, it may be reinspected every 150 hours until replaced with an improved design. Improved stators have a chamfer added to each end of the abradable groove to provide a better surface for coating adhesion.

Commercial Support Program Notification (CSPN) A96029 provides reimbursement of labor costs of 1.0 M.H. per engine for accomplishment of the borescope inspection. If excessive damage is found, the program will provide parts at no cost and 50.0 M.H. labor reimbursement to replace the stator. The stator will be replaced during the next Hot Section Inspection, at no cost for engines having been inspected as directed in SB JT15D-72-7527.

The CSPN is only effective for aircraft that have had the borescope inspections performed, as indicated by SB JT15D-72-7527. The program will expire on November 30, 1998.

This inspection can be accomplished in conjunction with other maintenance events or Phase inspections. Failure to comply with the SB can lead to expensive engine maintenance events in the future.

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