Page 14 - Oct24

MAINTENANCE TIP
Preflighting and Preventative Measures
by Dean Benedict
Let’s talk about your preflight routine. Did you know there are some simple tasks you can add to your preflight checklist that could ultimately save you thousands of dollars in maintenance costs? Your flaps are one example—do you check your flaps regularly?
Remember the old adage: “An ounce of prevention is worth a pound of cure.” That’s especially true in aviation maintenance because when preventive measures are not taken in time, the cure weighs much more than a mere pound. It’s, unfortunately, more like a ton.
Playing With Flaps
What’s the first thing I do when I walk up to a King Air? I check for play in the flaps. Most likely they’re in the “up” position, so I wiggle the trailing edge up and down a little bit. If the flap is rigid with no play at all, it is a red flag. I’m looking for a little bit of movement.
Next, put the flaps in the “down” position and do the same thing. You want the same outcome as in the up position. Wiggling the trailing edge up and down, you are looking for about a quarter-inch of movement. The down position check is the most critical, as you never want to be stranded in the boondocks with your flaps stuck in the down position!
A rigid flap is usually bottomed out in the flap track. If not detected and remedied, this will cause the flap flex shaft to fail and/or the flap motor to jam or burn up. These expensive problems are easily avoided by regularly checking for a little play in your flaps.
Limit Switches Have Limits
A flap that bottoms out in the flap track has limit switches out of rig. The righthand (R/H) inboard flap is the “master” flap on all King Airs, and on many models the limit switches are found there.
You can see them with your flaps in the down position. On some older King Airs, the limit switches are mounted on the flap track assembly. On newer King Airs, an arm runs a shaft with cams that activate the switches. The flap switch in the cockpit controls the flap motor and the limit switches prevent the flaps from moving too far.
Over time, as the linkage and bushings start to wear down, the limit switches go out of rig. A flap that bottoms out repeatedly will eventually break the flap flex shaft or burn up the motor and gearbox. Avoid these problems by checking your flaps regularly and alerting your shop at the first sign of flap stiffness. Bushings can be replaced and the cam or switches can be adjusted to stop the flaps a little sooner and prevent them from bottoming out. Crisis averted.
Watch Your Washers
While you still have your flaps in the down position, there is another thing to check: the Teflon® washer
12 • KING AIR MAGAZINE
OCTOBER 2024