Learjet 40/45: Main Landing Gear TR

Learjet has just released a couple of Temp Revisions (TR) on the 40 and 45 model aircraft, regarding the inspection of the main landing gear (MLG) struts and actuators.

Landing Intervals

The largest area of concern is the revision of Inspection Reference Numbers (IRN) S3220018, S3220022 and S3220111. All three have revised the inspection interval to include the words:

“…or 8 years, whichever occurs first.”

The landings interval for IRN S3220018 remains at 6,600 landings and 10,000 landings for IRNs S3220111 and S3220022. However, if your aircraft is over eight years old, you have until the next scheduled “B5” Inspection to perform these items per the note included in the IRNs.

Nondestructive Inspection

We are currently working with Learjet to gain clarification on other issues surrounding this TR.

• IRNs S3220022 and S3220018 have the same interval and Nondestructive Inspection (NDI) procedures to inspect the same parts according to NDI manual Part 7, 32-10-07 (forward trunnion pin) & 32-10-08 (aft trunnion pin).
• For IRN M3220024, this inspection is performed at 24-months and is also called out for an 8-year interval on S3220018, both of which use the NDI Manual, Part 7, 32-10-02 (actuator to strut pin). Also note IRNs M3220014 & M3220038 call out those actuator pins having a Life Limit at 60 months.

Axle Beams

The last item I want you to be aware of is even if your axle beams have been sent out to the vendor for repair, the NDT requirements in S3220018 WERE NOT DONE at that time. Hence it is still due at the 8-year/ 6,600 landing interval. Since we are discussing axles now, you should consider complying with IRN P3220007. This is to borescope the axles at 48 months.

Be aware that the MLG struts and actuators do have to be removed from the aircraft and disassembled for these items to be inspected. Our concern here at Duncan Aviation is that in performing maintenance on these items in the past, we have come across corrosion issues that have required part replacement. This in turn has led to issues with availability of parts.

Removing Bushings

In order to comply with IRN S3220018, ALL the bushings must be removed. Currently there is no published procedure to install the bushings back into the strut pieces. All the pieces that had bushings removed must go to Learjet in Wichita to have the bushings installed per a proprietary Heroux process. There are a limited number of bushings available. Be careful during removal that the bushings are not destroyed.

Results of Changes

One last item to note as a result of these changes, the 10,000 Landing “Major Landing Gear Inspections” is all on the nose gear area.