Page 14 - Volume 10 Number 10

Will Your Flaps
Create a Flap?
Not long ago, I had four King Airs in a row that had flap issues. Three of them were in the hangar at same time. A contagion of flap failures? Flap Cooties? Let’s hope not.
F90 – No Washers
First, there was an F90 in for a pre-buy inspection, and we found that most of the flap roller bearings were worn out. We had to replace six out of the eight bearings. Worse yet, every roller bearing was missing the all- important Teflon washer – not one to be found! Also, the flaps were wildly out of rig. The only thing more shocking was the fact that just 10 hours earlier, this King Air had been through a Phase 1-4 inspection (at an authorized service center, no less)! Good thing the prospective buyer arranged his own pre-buy in spite of the recent inspections, because this King Air had plenty of other issues to be worked out before the deal closed.
Model 300 – Roller Bearings
Concurrent with the F90 issues, a King Air 300 was in for a phase inspection and needed all of its roller bearings replaced – making it another four roller bearings we changed. The 200s, 300s and 350s have the Teflon washer/roller bearing setup on the outboard flaps only; the 90s and 100s have it on all four flaps. Each flap takes two washers and two bearings.
The outer ring must slide smoothly around the center post with no grinding or rough patches, and the center post must stay firmly in place. The center post in a worn out bearing is wobbly and shifts back and forth.
A B100 – Damaged Flap Track
Across the hangar, a King Air B100 in for phase and gear inspections had one seriously messed up flap with a bad roller bearing and no Teflon washer. Actually, the washer was installed on the wrong side of the flap track where it does no good and does not fit. The washer’s interior hole is nearly one inch in diameter to accommodate the center post of the roller bearing. Installed on the wrong side of the flap track, this comparatively giant washer was hanging on a bolt less than one-fourth-inch in diameter.
by Dean Benedict
This example of roller bearings reveals the middle one is shown shoulder-down, the outside ones are shoulder up and show the outer ring around the center post; the one on the left is new.
I wasn’t surprised at having to replace all the roller bearings on this 300. They caught my attention at the last inspection and I knew they were nearing the end of their useful life. You can’t tell if a bearing is bad just by looking at it though, you have to hold it in your hand and feel it.
12 • KING AIR MAGAZINE
Diagram of the flap track assembly from the maintenance manual. Although this diagram is from the King Air 200 manual, all models of King Airs have the same flap track.
Without the Teflon washer in place to protect the side surface of the flap track, the shoulder of the roller bearing gouged into it, metal-on-metal. This is the worst possible situation, and the damage looked pretty profound. There is a diagram of the flap track assembly in the maintenance manual (see example above); the aft flap track is on the right. The shaded gray area on the diagram is where the roller bearing shoulder scrapes and gouges if the Teflon washer is worn out or missing. The maximum allowable wear to the flap track side surface is .050 inch. It wasn’t looking good and I was worried.
OCTOBER 2016
MAINTENANCE TIP