Speed Brakes

[craig moodie]

I need some help with my speed brake system on an LNC4

I have a Lancair IV=P with what I think are legacy Precise Flight cable-operated speed brakes. They have worked with no issues for the last two years (since purchasing). Recently on a flight, they failed. I know very little about the system, but after looking them over, I have concluded that the switch on the stick is working. The servo motor is working. The speed brakes deploy when I pull the cables by hand, which leaves the clutch and pully that rolls up the cable and deploys the speed brakes to be the problem. The pullies don't turn much. They turn a little, and then they click and jump. I can't tell if the clicking and jumping is caused by a worn or misaligned gear or an electrical condition causing a solenoid to jump and click.

I can't tell what is causing this or find any good information on the system. There don't appear to be any parts for sale for this legacy system. To diagnose this, I must remove the servo and clutch, which will require me to remove both front seats.

Before I do that, does anyone have any experience with these old-speed brake systems? If I could find a diagram or a good picture of one before removing it.

Thank

Craig Moodie

[Admin]

Craig, do they fail to deploy, or fail to retract? Is it both brakes or just one? I had a speedbrake fail to retract and it ended up being the retract spring.

You can call Precise, but they will push for you to send the controller and boxes in so they can fix and give you a warranty. That will be very expensive.

If you can find the fail, they will sell replacement parts, but they won't warranty anything. That's the option I chose when I had the malfunction.

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[George Wehrung]

Bob Pastusek might have a diagram or schematic of the system.


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[Chad Crow]

Craig, et al;
I realize your post is over a year old, but my problem falls within the airbrakes subject. BTW, did you manage to solve your issue(s)?

My air brakes are also the older, cable driven style (Mfgr'd `94) - Precise Flight no longer supports this model at all - but they did send my the pdf file that describes installation and setup. PF's newer air brakes are $8,600.
With a no little trouble shooting we were finally able to confirm my 12V servo motor was dead - (AMETEK-PITTMAN GM8224S015 12 VDC 19.5:1 Ratio).
Am/Pit is impossible to talk to, but I did find a local elec motor company (in the MSP area) that handles their line. While I've been waiting for them to confirm if they have access to a new one ($500+ . . . ), I found a used one on Ebay that carries a 90 day warranty, for a $116 - I ordered it.

It occurs to me that the servo motor doesn't really see that much use - rhetorically, why should it burn out?
Part of the answer might be - making sure the mirco-switches that turn the motor on/off are working correctly.