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working, such as the outflow valve, the safety valve, the dump solenoid and the pre-select solenoid.
Of course he wondered if there was a problem with the controller. It amazes me how many people immediately suspect the controller before everything else. Whenever there is a pressurization glitch, everyone’s knee-jerk reaction is to assume the controller is at fault. When troubleshooting pressurization, the controller is the last place I look – and I do mean last – that’s cardinal rule No. 2 in troubleshooting pneumatic flow packs. These controllers don’t fail. Yes, they can have inaccuracies, especially with selected altitude (being off by 500-1,000 is not unusual) but total failure is extremely rare.
He tested and re-tested the various valves and solenoids to no avail. Everything checked out well. Out of the blue, I asked him for the serial number of this aircraft, and guess what? I knew this B100 quite well! Back when I had my shop, I performed regular maintenance on the King Air for several years.
I asked him if he was ordering flow packs for a -6 engine or a -10 engine. (Note: The Garrett engines originally installed on B100s by the factory were TPE 331-252B-6. Later, an upgrade became available which modified these engines. Installation of the mod turned
the engine into a TPE 331-252B-10). I knew this B100 had -10 engines.
I also knew that the flow pack for a -6 engine was not the same as the flow pack on a -10 engine. The IPC he used to research the flow pack only lists the components installed when the aircraft was new. The parts and components that go along with the -10 engines are found in the -10 STC, which would be in the aircraft flight manual.
Once the correct flow packs for the -10 engines were procured and installed, everything worked as advertised. I just wish I had asked more about the aircraft history before diving into discussions of squawk and remedy.
Maintenance Manual Versus STC Requirements
This week, while writing this very article, I got a call from a King Air owner in distress. His model 200 was in a shop for phases and hot sections, and the shop’s estimate raised many questions. He had lost confidence in the shop and wanted my advice. He sent me the estimate, a few photos and the work order. Right away I saw several red flags to pursue.
DECEMBER 2023
KING AIR MAGAZINE • 13