Page 16 - Dec 2022

MAINTENANCE TIP
F90 Heat Ducts:
A Curious Coincidence?
by Dean Benedict
Last summer I supervised a gear overhaul (inspection) on a King Air F90 belonging to a client. We were coming down the home stretch. The motor, gear box and torque tubes were ready for reinstallation. The cabin had been gutted for ease of access and we were about to reinstall all the floorboards that had been removed for the inspection. On a whim, we decided to look around before closing up.
To my dismay, we found a mess of melted ducting. The under-floor heat duct going to the aft cabin and baggage compartment was totally melted and deformed (photos above). Worse yet, the tail deice supply line, which runs right on top of the heat ducting, was melted flat which would point to no air getting to the boots on the tail. That’s a problem.
14 • KING AIR MAGAZINE
Seen It Before
Believe it or not, 10 years ago I saw this exact scenario on another F90. It flew to my shop for same-day service on a couple squawks. I’d never seen this King Air before. For one of the squawks, I needed access under the floorboards
The melted heat ducting (and a close-up of the damage, right) that was under the floor- boards of an F90.
DECEMBER 2022