flap actuator failure

10-07-2009, 07:50 PM

Fred Lohr | flap actuator failure

on the way back from the flyin i was coming in for a routine landing on the 3000 ft turf strip where i keep my plane. gear down, flaps to 25 degrees, airspeed about 80 knots on final and there was a "thunk" in the back somewhere and a bit of a drop and the flap indicator went to 0 degrees.

i have landed before with no flaps in the seawind and it is really not a big deal, you just have to keep the power and airspeed up and then slow down right over the runway. The last time this happened was a couple of years ago because of some electrical and valve issues and i flew around at altitude while to get the feel of slow flight without flaps before i landed. This time i just landed with power and some more speed (maybe 80-85 over the numbers) and slowed down rapidly on the turf.

the failure was the shaft of the actuator where it is cut down to the threaded portion for the rod end. that is the weakest link. This is the new style actuator made by evansburg tool. it is fat, about 2 or more inches in diameter, has a tapered end and binds slightly when the flaps are down with the "deactivated mixer" set up. It is only about a year old. the older actuator "about 1 1/2 inch does not bind at all. I sent the new one back to alan at evansburg and will see if i can have it rebuilt with a shaft with larger diameter cut threads that will fit a rod end.

this is a failure mode that you really can't see developing, as the stress fracture in the metal probably can't be seen before it gives way, but any binding of the actuator should not be accepted as it applies a slight bending force to the rod with each flap extension. Right now the old actuator is doing fine as it does not bind at all due to the smaller diameter of the cylinder.

i also found out why the main gear wasn't tucking up fully, the "dog bone" that joins the actuators for the main gear had pulled down from the roof.

I'll have to fix that with better, longer, fiberglass layups.

10-07-2009, 07:57 PM

Mike

Fred, good to hear you are ok. Do you think the stress might also be created by the water landings....water hitting the flap..? I was reading about using flaps only while on step. You might also want to look at the flap rod since I have broken 2. I will have to check the flap actuator rod.......

10-08-2009, 07:13 AM

Fred Lohr

mike,

i agree that water hitting the flaps can stress that area as well. In rough water, i start with the flaps up. This method is advocated by dick silva in his tips on flying the seawind. One point of my post is that pilots should know that landing the seawind without flaps can be done safely, just keep the airspeed up a bit. You start to get nose high as you slow down so thats the time to set her down. So far my flap rods have held up but i am aware of you and others who have had failures there.

If anyone wants a nifty cover for their seawind, I am having one made by the same guy who made the one that Tom Saccio has. It is made of the same material that is used to cover vintage cars so it wont scratch your plexiglass. fits on easily. We can get a better price if we order a couple of them. send a text message to charlie 252 947 5355.

10-08-2009, 03:38 PM

Mike

One of my best landings was at 100 mph no flaps.....couldn't feel the wheels touch.

Yes I am looking for a new cover However, you all might want to think about an idea I had while trying to sleep at Oshkosh. I wanted the cover to have extensions so when the canopy is open there is netting that droops down to the ground. While closed I could roll it up and tie or clip it in place.

what is the $$ now..?

10-08-2009, 05:15 PM

Fred Lohr

for cover, don't know the price for cover yet, expect around 600$. check out this old seawind newsletter for the tent option. sorry if this is a little off topic .http://www.seawind.net/The%20Seawind...ummer%2004.pdf

10-08-2009, 06:21 PM

Mike

Thanks Fred....

I wasen't L@@King for anything that dramatic...something a little sleeker.

I have to look at some of those old newsletters....!

Thanks

10-10-2009, 07:35 AM

Fred Lohr

getting back to my flap actuaor faliulre, it tuns out that what happened was the dogbone that connects the two gear actuators had pulled loose from the underside of the fuselage/turtle shell. This was not too noticeable at fist because when the plane is on its gear it is pressed up into position. when the gear retracts it is pulled down and did a guilllitine on my flap actuator. This also explains why the maingear wasn't seating alway up for the last flight or two. John at planemakers has some great suggestions about this area which he will post so i will not steal his thunder. I'm not sure why this happened after 5 years of flying, but maybe its time to change those gas shocks, when i fix this up. he said mike reibling in canada had a similar issue Mike?