Thinking back on the King Air Gathering this past March in Phoenix, it was great to have a portion of the event in a hangar on the airport with a King Air on display and available to everyone. I was there with Travis Lamance of Haven Aero to give a maintenance technician’s perspective on certain things to watch for when preflighting a King Air. Tom Clements and Zach Cleaver were there to do the same from a pilot’s perspective.
Tom and Zach went first, with Tom walking around the King Air and commenting on things he does routinely that are not necessarily called out on the standard preflight checklist. I had to laugh. Tom completely stole my thunder. He touched on everything I was going to say, starting with checking the flaps for a little bit of play.
When “meeting a King Air for the first time,” my way of shaking hands is to jiggle the flaps. I want to make sure they aren’t totally rigid – there needs to be some movement. If this sounds familiar, you probably read my article on this very topic in last year’s October issue. Apparently, Tom is of the same mind. He and I go way, way back and through the years we usually found ourselves on the same page.
Tom and Zach continued their walk-around with many good tips, from checking the oil to closing the cabin door. When the topic of gear doors came up, it was mentioned that the main gear doors on a C90, like flaps, should have some play.
In fact, the main gear doors on the King Air C90 have quite a bit of slop when everything is done right. The linkages and hardware associated with these gear doors work great when the gear retracts and the doors close snugly. But when the aircraft is sitting on the ground with the doors open, this assemblage is quite loose, and this is normal.
Floppy gear doors win the day
I am reminded of a King Air C90 that was promptly ramp-checked by the Federal Aviation Administration after landing at KLAS in Las Vegas. The FAA inspector thought there was too much play in the main gear doors and grounded him on the spot. The owner/pilot was in disbelief but called back to the factory right away. He got through to Tech Support (this was a long time ago) and was assured that looseness in the gear doors on a C90 was normal.
When Beechcraft Tech Support learned the aircraft was in Las Vegas, they called me and asked me to help this owner. I called him while he was still with the FAA inspector, standing on the tarmac in front of his King Air. He put the FAA guy on the phone and we had a nice discussion on the rigging of gear doors on a King Air C90. The FAA had quite a few C90s back then; I had worked on a couple of them when they were in Las Vegas with squawks. This conversation did the trick. The owner and his King Air were subsequently absolved of any transgressions.
The thump test
At the recent King Air Gathering, we were still on the topic of gear doors when I reminded Tom of my post-maintenance tip on checking the main gear doors on 200s with standard gear. I give those gear doors a firm thump with my fist. If the door collapses inward, it’s not rigged properly.
The main gear doors on a King Air with standard gear should not have any play. King Airs with standard gear include the following models: 100, A100, B100, 200 series, 300, 350 series and the F90.
These gear doors must withstand the air load on takeoff without being pushed inward before the gear comes up. If rigged improperly, the oncoming airstream during takeoff can push the door inward – just a little bit, a half-inch is enough – and as the gear retracts, the tire snags the door, smashing it into the wheel well. It’s not pretty. Unfortunately, an example of this comes to mind.
The owners of a B100 (which has standard gear) took it to a shop with the following squawk: “Red light in gear handle stays on with landing gear in the up position.” Normally, when the red light won’t go out, one or more of the uplock switches is out of adjustment. This is a pretty straightforward issue, but the shop insisted the landing gear needed a full re-rig, and the owners did not know any better.
The shop rigged the gear. The owners came to test-fly the aircraft. They rolled down the runway, broke ground, put the gear up and got a red light. They tried to put the gear back down but it wouldn’t budge and the red light stayed on. They tried to crank the gear down by hand and were unsuccessful at first. Eventually enough force was exerted on the hand crank to get the gear down manually. Once on the ground, they were horrified to see the outboard gear door on one side was totally mangled and crushed into the wheel well.
You can guess what happened. The pressure of the airstream on takeoff pushed that gear door inward just enough to get caught by the tire as the gear retracted. The gear door was crunched into the wheel well. This jammed the gear and prevented a full retraction; further, it prevented the gear from extending. They were lucky they could apply enough force on the hand crank to break the jammed gear free and extend the gear manually. Though I doubt they felt lucky at the time, at least they avoided a gear-up landing.
Gear door linkages must be adjusted to an over-center position to withstand the air load during takeoff. Failure to do so allows the above scenario.
The same principle applies to the gear itself. The drag legs must be adjusted to an over-center position to withstand the force created when the gear meets the ground on landing. The No. 1 cause of gear collapse on landing is improper rigging of the drag legs.
It gets worse
The shop working on this B100 ordered a new gear door, installed it and proceeded to check the rigging of the gear all over again. They jacked the B100, but this time they disconnected the gear door linkages, allowing the gear doors to hang freely. When it came time to swing the gear, the same tire caught the brand new gear door and crunched it into the wheel well, again!
Apparently the gear door in question was hanging a little bit to the inside, just enough to get caught by the tire during retraction.
Doing it right
Disconnecting the gear door linkages was the correct move. On a gear swing retraction, you don’t want the doors to shut because they’ll cover up everything – you want to see everything in its retracted position. The big mistake by this shop was leaving the doors to hang freely. I always tied the doors back with safety wire. With the doors held open wide, I could get in there and see exactly how everything is retracting into the wheel well. Is the strut bumping into the spar? Are the tires rubbing against anything?
Once I confirm everything retracts properly, I would connect the door linkages and adjust as necessary, making sure all linkages are over-center and the doors are closing completely.
The main gear doors on the F90, the 100, A100, B100, the 200 series, the King Air 300 and the 350 series are all similar. Therefore, whenever those King Airs have had their landing gear worked on or rigged, I recommend you do the thump test before the next flight. This does not apply to King Airs with high-flotation landing gear.
High–flotation gear doors
High-flotation gear doors differ greatly from the gear doors for standard gear. They are physically connected to the gear strut. As the gear extends, it pushes the gear doors open. When the gear retracts, it pulls the doors closed. But take note: When the gear goes up, there is an unexpected twist to the gear door movement. As the gear begins to retract, the doors are pushed further open at first, before being pulled into their closed position. It will take you by surprise when you see it for the first time.
The doors for high–flotation gear generally have no play. There may be some very minor movement due to the composition of linkages and hardware.
Nose gear doors – The same on all King Airs
Let’s not forget the nose gear doors. All King Airs have the same nose gear and therefore have the same nose gear doors. Even King Airs with high–float gear have the same nose gear and doors as all the other models. King Air nose gear doors are rigid; they have no play.
In closing, remember that slop is good on the main gear doors of a C90. If your King Air has standard gear, add the thump test to your preflight routine, especially when it’s coming out of maintenance.
Fly safely out there.