Hawker Spring 2007

• Industry Standard Electrical Components vs. OEM Components
• Are You Indicating a Generator Amperage Split?
• It’s Your Turn

Industry Standard Electrical Components vs. OEM Components

— Karl Detweilier

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

What’s the difference? 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 fact that the OEM has done the 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 this topic, please contact Dan Magnus at 800.228.4277 ext. 4217 or Jerry Cable at ext. 8112.

Are You Indicating a Generator Amperage Split?

— Jason Behrens

Do you have a DC generator output amperage split between your left and right generators or are you just indicating one? A simple troubleshooting step is to open the Buss Tie Contactor with both generators online (APU Gen. off). If the amperage split still exists with the Buss Tie open, you may have an issue with indication not the generator systems.

An aircraft with a true generator split usually indicates a close to equal amperage reading between the two generators with the buss tie open. In the DC generator amperage indicating circuit for each generator is a little relay that is used to either indicate generator amperage output or main battery charging amperage. The relay is energized by the battery charging amps push button switch located on the CG panel near the gauges. Over time these relays may build resistance across their contacts and produce errant generator amperage readings. These relays are designated “AA” (No. 1 Gen) and “AB” (No. 2 Gen) in the 800 series aircraft and are installed on Sub-panel B behind the co-pilot seat on the DA panel. On 700 series aircraft they are designated “LT” and “LU” and also installed in the DA panel.

For more information, please contact Jason Behrens at 269.969.8419 or Dick Hyde at 402.479.1561.

It’s Your Turn

— Dick Hyde

Throughout years of Duncan Intelligence issues, Duncan Aviation technicians have shared their learned experiences, techniques and technical advice while working on thousands of Hawker aircraft. We would very much like to hear about your experiences and any tips and techniques you may wish to share about the Hawker airframe.

Please contact Dick Hyde at 402.479.1561 or Jason Behrens at 269.969.8419 and let us know your thoughts.

( Return to top )