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Learjet Spring 2004
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45 Model Ground Blocks
— Dave Schiver
On Service Bulletin 45-53-10 R1, which replaces the ground blocks and fasteners, there have been problems with heat damage. These ground blocks are located in the pylon areas and attach to the fuselage. In worse case situations, this has caused PDP failures. Learjet is working on revision 2, which will create a better contact area and reduce the heat. Some aircraft have had repairs accomplished with good results. Duncan Aviation recommends inspection of the area around the ground blocks and fasteners for any sign of corrosion and/or heat damage any time the pylon panel is open for maintenance. If there are signs of heat damage, we can assist you in coordinating the repair. For further information, please contact Dave Schiver at 800.228.4277.
AD 2004-03-08
— Dave Schiver
On March 15,2004, AD 2004-03-08 became effective. This AD requires the shear web inspection (S/B 31-51-2 or 35/36-51-3) within 3,000 hours total time or 1,200 flight hours or 1 year after the effective date of this AD, whichever occurs first. There is a repetitive inspection (part b) dependent on the results of the initial inspection (part a) until the repair (S/B 31-51-3 or 35/36-51-4) is accomplished. The issue that we have noted is the way the Terminating Action is written. It calls out Rev 1 for both repair S/Bs.
This means that if the repair was done per the S/B with no revision or revision 2, this will not terminate this AD. Also included is the early aircraft that had the repair done per the “repair drawing.” We have been informed that Learjet is working on a solution for this.
Environmental Control System
— Chris Gress
Duncan Aviation has received a number of customer calls regarding the failure of the Environmental Control System. A major component to this system is the ECS Panel (an electronic & relay circuit board). Duncan Aviation has obtained FAA approval for our test panel that essentially operates like the aircraft portion of this system. The test panel functions by providing indicator light illumination. An illumination indicates an active system component. Some ECS panels were sent to Duncan Aviation with apparent failures.
However, after examination, our technicians remarked that a number of the units were working correctly. Our Tech Reps relayed our findings back to the aircraft operator’s DOM. The finding was that these problems were being caused by corrosion build-up on the “gang ground connection” or by a high-resistance build-up in that system’s 28 vdc supply circuit. Both of those findings were causing voltage drops across a portion of the ECS panel that forced the system to operate in the emergency bleed mode. Keep this in mind while troubleshooting ECS squawks.
45 Fairlead Modification
— Dave Schiver
Watch future Intelligence issues for information on the release of Service Bulletin 45-27-9, Control Cable Fairlead Modification. This SB is expected to be released third quarter 2004 and will require the replacement of current fairlead material.
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