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Bombardier Learjet 40 & 45: Out Of Phase D Items

February 2021

L45.jpgIf your Bombardier Learjet 40 & 45 aircraft has complied with a Chapter 5 Phase D inspection due to Calendar Limits there is a chance some IRNs (Inspection Reference Numbers) could have been missed on the Phase D.

There are eight IRNs in the Chapter 5 Phase D that may not have been due at your last Calendar Phase D Inspection. These items are easily missed at the 4,800-hr Aircraft Total Time inspection.

Seven IRNs are single asterisk (*) items (No overrun or Ch 5 Tolerance). One is not. They are as follows:

*N5314000 (D1)
*N5323026 (D1)
*N5510005 (D2)
*N5510015 (D2)
*N5510016 (D2)
*N5510069 (D2)
*N5510082 (D2)
N5710084 (D4)

These all have the following Note:

NOTE: Initial inspection to be performed at 4800 flight hours with no calendar restrictions, and subsequent inspection every 2400 hours/96 months thereafter.

Therefore, if any Calendar Phase D inspections have been performed, they are not in sync with the IRNs listed above. Once out of sync, the only way to get the IRNs back into Phase D is to comply with these items early.

We have seen several Tracking Systems that do NOT track these IRNs separately from a calendar Phase D inspection.

Since recognizing this issue, we have begun to ask all customers if these IRNs are due and if they want them complied with “Out of Phase” when we quote a 4,800-hr inspection as a separate line item.

Pay close attention to this anomaly in the Learjet Inspection Program and have your chosen tracking service track these IRNs as separate items, if necessary. That ensures they do not get missed at the 4,800-hr inspection.


If your aircraft has more than 4,800 hrs. of total time and a Calendar Phase D Inspection has been performed, I highly recommend reviewing your aircraft’s records to ensure these IRNs did not get missed.

Additionally, I recommend taking it a step further and review old work orders and inspection guides to verify these items were complied with since most MROs do not list individual IRNs on the Log Entries for Phase Inspections unless requested by the operator.

Aircraft Enrolled on EMP

For aircraft enrolled on the EMP (Evolved Maintenance Program), Calendar Phase D IRNs are listed on the 2,400-hr, 4,800-hr Initial Inspection. Hopefully, your Bridging document captured this during enrollment.

If your aircraft has been on EMP since new, there should be no issue. The same is true with Bombardier Learjet 70 &75, as they have been on the EMP format Inspections since new.