HP-18 Center Stick Project

Update 16 April 2001:

Some good progress, but no photos because I left the camera up at the shop.

I got the welded aft roll bellcrank support tripod installed, and it works just fine as expected. I did get an idea on how to make the part cheaper and lighter, though. So I'll probably test a simplified version before production units go out the door.

I had the entire roll control system hooked up, and it seemed to work great. But on closer inspection the travel limits weren't right. So I started digging into the system, and found that a lot of the parts had been modified. Specifically, the ailerons centerline bellcrank had beem modified for differential. Also, the flap cam profile was a little different, as was the mixer stanchion and flap cam follower support.

All in all, I lost about 2/3 of my shop time restoring things to their original configurations, so I didn't get as much done as I'd hoped. Fortunately, I have flap cams and the mixer stanchions in stock, so I could get back on track much more quickly than if I had to make those parts from scratch.

I did manage to assemble my pushbutton flap crank handle (O.K. Udo, it's actually pull-handle) and double-geared crank mechanism, and get it mounted.

I also installed a prototype of my stabilizer link for the flap/aileron mixer stanchion. The prototype of the part that clamps to the stanchion was bandsawed out of aluminum plate; future units will be welded up out of .040 steel strap. There were no particular hitches, and that subsystem seemed to work great. After I installed it, I loosened the flap cam follower bolt up a little, and spread the ears on the follower support a bit. That greatly reduced the friction on the flap cam, and the whole mechanism seemed to work more smoothly.

I also did some more work on the access cover for the knee hump. In the instructions, I'm going to suggest leaving at least 2" of perimeter between the cut lines and the fuselage shell on the right and left sides. That'll make it tons easier to reattach the access cover. I made my access cover out of aluminum sheet, but it's starting to look pretty attractive to recycle the cut-out material as the cover. It'll probably require a couple of stiffening ribs on the inside, but those can easily be made out of some PVC foam with a couple of plies of bias tape and polyester over the top.

As far as the schedule goes, it looks like I'm slipping a bit. Earlier, I was hoping to tow over the hill to Air Sailing on the weekend of 21 April. But the ship is definitely not going to be ready for that. I'm going to Air Sailing that weekend anyway to take part in the annual clean-up day where we get the place ready for the soaring season. So now, I'm trying to get the ship to Air Sailing the weekend of 11 May, and start the inspection and flight test program on or about 25 May. The weekend of 18 May? I'm taking the family (actually, they're taking me) to Disneyland.

If the flight test program goes OK, I'll start a production run of 5 retrofit kits in late June.

page updated 04/16/01 all text and graphics copyright (c) 2001 HP Aircraft, LLC