Learjet Spring 2007

• Phase V Upgrade Confusion—Broken Down and Simplified
• Landing Gear Life Limits
• Industry Standard Electrical Components vs. OEM Components

Phase V Upgrade Confusion—Broken Down and Simplified

— Dave Schiver

Model 45s at Phase III: S/B 45-22-7* is the only way to fulfill this S/B. IC-600s must be sent to Honeywell for the upgrade at a cost of $750 per unit. Upon reinstallation, the units will need to be reprogrammed.

Model 45s at Phase IV: Two options: Use S/B 45-22-7, as stated above (send in/reprogram) or wait for S/B 45-22-9# and upload Honeywell software on the A/C with no software charges.

Model 40s at Phase IV: Two options: S/B 40-22-02* requires sending in the IC-600s to Honeywell for upgrade at a current cost of $750 per unit and then reprogram upon reinstallation or use S/B 40-22-04# and upload Honeywell software on the A/C with no software charges.

After completion of Phase V on any 40 or 45 A/C, the Brakes-Fail-Takeoff-CAS-Inhibit can be installed. These are S/B 45-22-8* for 45s and S/B 40-22-03* for the 40s.

*Released S/Bs
#Expected release date: April 2007

Landing Gear Life Limits

— Jerry Cable

The Learjet 20, 30 Series and 55 MLG struts have the same life limit of 9000 landings. This can be increased to 12000 landings by replacing the MLG cylinder per the applicable Learjet SSK (Special Spares Kit). This modification does not zero time the struts, but gives another 3000 landings before replacement.

Operators will want to perform this SSK, especially if they have more than one Learjet in their fleet. When the gear that has been modified reaches 12000 landings and is cycled out, the cylinders are still serviceable and can be used on another aircraft that is in need of the SSK. The landings on the cylinders will need to be tracked independently from the strut and must still be scrapped once they have accumulated 12000 landings. This allows the cylinders to be used on four sets of gear, to increase the landings, before they are scrapped.

The other option, for Lear 20 and 30 Series, is to perform an STC that increases the cycle limit of the gear to 17000 landings. This requires the SSK to have been previously incorporated and certain internal parts to be changed at time of STC compliance. The strut must then undergo inspection at 1000 landings and every 800 landings thereafter.

Industry Standard Electrical Components vs. OEM Components

— Karl Detweiler

Duncan Aviation often sees Mil Spec electrical components (resistors, transistors, IC’s, diodes) installed where OEMs have specified a certain criteria for repair parts.

OEMs often identify a tolerance specification range they prefer an electrical component to operate within that is more stringent than the broader tolerance range of a Mil Spec equivalent part. Although the generic Mil Spec part may work, its use may lead to less reliability, and early failure of the assembly. Duncan Aviation recognizes and agrees that the closer tolerance ranges identified by OEMs increase longevity of repaired assemblies.

OEMs identify these electrical piece parts in repair manuals with their part numbers and the price may be a little higher. The higher price reflects the OEM’s hard work of identifying and eliminating electrical parts that are less reliable, thus saving you time and money.

If you have questions or want additional information concerning these topics, please contact Dave Schiver at 800.228.4277 ext. 1680, Jerry Cable at ext. 8112 or Dan Magnus at ext. 4217.

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