Speed brake retraction

[Mooney Mike]

My right speed brake just started to be slow to retract (after a Colorado cold snap). They both deploy fine. I believe they are vacuum type since it’s a1988 m20k and they only work with the engine running. Does anyone know if the vacuum retracts or is it strictly cable or spring? Do they run off the engine driven pump? I also noticed my vacuum gauge took about five minutes to get in the green. Normal? Problem looming? Even when engine driven pump was in the green the right brake would not retract normally.( very slow) I’m working hard on Ifr currency and expect to be flying in imc soon. Don’t want any surprises. Help!

[kortopates]

The vacuum system extends the speed brakes against the spring. The spring retracts them back in. If you have the Standby electric Vacuum System, you can test them on the ground in your hangar without starting the engine. The cables that go through a bicycle like sheath can also become a problem when the sheath becomes cracked and brittle. When that happens the cable & cable conduits need replacing. You can examine the cables conduits from under the wheel wells. If their extending okay then the vacuum canister is working fine which is below the rear seat.

Its not normal for them to hang on retraction so you'll have to figure out the cause and address it. The vacuum should be in the green range when you have sufficient RPM, idle is not necessarily enough, but 1700 should be fine. 

Speed brakes should never be deployed in IMC at or near icing, so personally I just avoid their use on approaches 100% of the time to avoid bad habits. If they ice up they're not coming back down till above freezing temps again.

Edited December 31, 2017 by kortopates

[dlmorris]

Check to make sure the retraction spring is not broken. They wear out and are needed to draw the brake back into the wing.

I agree with prior post. NEVER deploy a speed brake in icing conditions.

[carusoam]

Welcome aboard, Other Mooney Mike.  Or Mooney Mike with the space... 

Add some detail to your avatar when you can.

Best regards,

-a-

[Mooney Mike]

Thanks much for a better understanding of the speed brakes. I will never deploy in icing. Hope to never be in icing. Not surprised there’s another Mooney Mike. I’m Colorado Mooney Mike. M20 k 252. Owned three years. Had seven singles before her and this is head and shoulders the best airplane I’ve ever flown. Solid, fast and looks damn good. ... now if I could just get that speed brake to retract. Got my seaplane rating last week at the ripe old age of 63! Fun stuff.

[David Mazer]

18 hours ago, kortopates said:

Speed brakes should never be deployed in IMC at or near icing, so personally I just avoid their use on approaches 100% of the time to avoid bad habits. If they ice up they're not coming back down till above freezing temps again.

Been there and done that. One brake up and one brake down.  Very interesting and something I avoided after.

[Piloto]

Keep them lubricated with WD-40 during winter. On my way to CYYT from LPAZ during winter (ferry flight) I accidentally depressed the speed brakes switch on the yoke. When tried to retract them they stayed half way up frozen. This reduced my range to reach CYYT. I went on doing very steep turns (60deg bank) to increase the g forces. This helped on fully retracting them. After this I pulled the brakes circuit breaker.

José 

[David Mazer]

WD-40 might be a good choice under icing/wet conditions but it isn't a lubricant.  WD actually stands for water displacement and WD-40 is the 40th formula. I was pretty surprised to learn that after using it for many years incorrectly. A silicone based lubricant might do both lubricate and water displace.

[BradB]

Pulling the breaker in the winter in IMC is a good idea.   I have accidentally hit mine in icing on decent to an approach with the same results as above - one stuck up and one down.   Luckily it retracted within 20 seconds, but I was a lot more careful around the speed brake button after that.

Brad

[Piloto]

The best of both:

https://www.bing.com/videos/search?q=silicone+lubricant+vs+wd+40&qpvt=silicone+lubricant+vs+wd+40&view=detail&mid=575D5BE8D91D99AF5E7A575D5BE8D91D99AF5E7A&FORM=VRDGAR