Precise Flight Speedbrakes

[Mark89114]

I had a minor issue with a microswitch on my 2000 ovation, mechanic and I diagnosed and adjusted the switch and everything looks good for now.

He was commenting on the enormous thump the brake makes as it retracts, I always assumed it was normal?  Nothing looked abnormal in our investigation but just double checking with the experts.

Thanks.

[N201MKTurbo]

They only make the big clunk when the clutches open. The clutches open when the power is turned off or the control box tells them to open because they are out of sync. 

FWIW mine don't retract reliabley on the ground, but they always work perfect while flying. I went compleatly through them this annual and they are better, but on the ground they will still clunk down about one out of five times.

[Emmet]

I had the same same problem. Mine was wired incorrectly so that when pushing the retract button the power was taken of - result was the bang. We rewired the relais and they now they retract as smoothly as they deploy.

[Mark89114]

Emmet - interesting I will take note of this in the near future.  How were the relays wired incorrectly?  I assumed during installation just run the cannon plugs and everything is done at the factory, but I could be wrong.  I believe they were installed as after market speedbrakes. 

Is there any logic on extension?  The right one seems to come up first, hesitate and then they both go up at the same time?

 

[Emmet]

You are right, mine are an aftermarket installation. So yours may be different. There is no complicated logic in the relais box - only one relais. I can also imagine that a short in the wiring can produce the same behaviour.

[Jeff H.]

Just to confirm what others have said - Rocket with speed brakes, owned for 2 years, operated every flight, never a thunk or thump on retraction.  Both work simultaneously on extension and retraction.

Good luck.

[peevee]

On 3/11/2016 at 9:42 AM, N201MKTurbo said:

They only make the big clunk when the clutches open. The clutches open when the power is turned off or the control box tells them to open because they are out of sync. 

FWIW mine don't retract reliabley on the ground, but they always work perfect while flying. I went compleatly through them this annual and they are better, but on the ground they will still clunk down about one out of five times.

Interesting to hear, apparently if you extend ours, leave them out, and cut the master ours don't either. One side goes down and the other wouldn't. Go figure? 

[jclemens]

2 hours ago, peevee said:

Interesting to hear, apparently if you extend ours, leave them out, and cut the master ours don't either. One side goes down and the other wouldn't. Go figure? 

Your speedbrakes and the OP's need to go back to Precise Flight for repair.  They should extend and retract simultaneously at the same speed.  If extended and power is removed they should both slam down.  There were several different variations of components used in the speedbrakes over the years, some more reliable than others.  They started out vacuum driven and cable operated, then went to self contained electric units with an asymmetric logic unit.  The early electric units had gears that were prone to damage.  Sending them back to the good people in Oregon will get them up to date and working properly.

[N201MKTurbo]

If they don't go down when the power is turned off, you probably have broken springs. There are two clock springs in each unit. They fatigue and break eventually.

[peevee]

On 3/29/2016 at 7:44 PM, jclemens said:

Your speedbrakes and the OP's need to go back to Precise Flight for repair.  They should extend and retract simultaneously at the same speed.  If extended and power is removed they should both slam down.  There were several different variations of components used in the speedbrakes over the years, some more reliable than others.  They started out vacuum driven and cable operated, then went to self contained electric units with an asymmetric logic unit.  The early electric units had gears that were prone to damage.  Sending them back to the good people in Oregon will get them up to date and working properly.

Thank you, it came up at annual when they were due for lube and inspection. He mentioned for whatever reason that he did that and one side hung up, I think he banged on the wing and they snapped down, I'm sure just something hung up there. I'll have our regular mechanic run it down once I verify the condition exists. I don't know about the other partners but I only use the brakes about every 4th or 5th flight anyway.

Edited March 30, 2016 by peevee

[jclemens]

He did it because you are supposed to test them at annual.  If you have to bang on the wing to get them to go down, they failed the test. 

[ArtVandelay]

6 hours ago, peevee said:

I don't know about the other partners but I only use the brakes about every 4th or 5th flight anyway.

I would exercise them more often, mechanical components like to be used, but not abused, especially if you park outside.

[rgpilot]

The most common problem with the electric speedbrakes is from water and dirt washing down into the speedbrakes from rain and perhaps washing the plane. I've had two versions of the speedbrakes, 93 M20J, and 04 M20R. I had them freeze up at high altitude because of a clogged drain. I had them clog up do to dirt at the bottom of the housing. It's important to check the drains regularly if you leave the plane outside. I mostly hanger the plane but when I leave it outside for extended periods, I cover the speedbrakes with painters tape. Put a small piece over the door key hole to remember to remove tape.

[peevee]

10 hours ago, jclemens said:

He did it because you are supposed to test them at annual.  If you have to bang on the wing to get them to go down, they failed the test. 

Does the required test call for extending the brakes a d then shutting off the master? I sort of doubt that procedure is specified anywhere.