Speed brakes

flyingcheesehead

flyingcheesehead

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iMooniac
Hey folks,

I've got speed brakes on the Ovation that need some work. These are the Precise Flight electric ones installed at the factory, and as I understand it, not the latest models which can detect asymmetric deployment and such. I've had a couple of problems with them, so they need some work.

How much maintenance can be done on these by an A&P, or am I just going to have to get them pulled and sent back to Precise Flight for overhaul? Also, about how much does it cost to R&R them, and how much does the overhaul from Precise Flight cost? Is there anything I can test/check on my own?

FWIW, the symptoms: For quite a while, they simply wouldn't retract fully if I was at idle, which I chalked up to low voltage in the electrical system. Then I had an asymmetric deployment (which is pretty much a non-event, BTW) and had them looked at by the local shop. They lubed them up and maybe did some other minor things, but now the right-hand one doesn't retract fully on its own and on my last flight the left-hand one started coming up halfway and doing what I can only describe as "having a seizure" - It kind of flutters in and out a little bit from halfway quickly. When I hit the switch again, it retracts just fine.

I got the feeling from talking with a Precise Flight rep at Oshkosh a year or two ago that they don't want anyone else to do anything to their stuff, they want to have a monopoly on maintenance - Is that justified? Are they really that hard to work on?

Thanks in advance for any help!
 
I don't mean to hijack the thread, but do they have that much of an effect on the aircraft? I've always wanted to ask.
 
The ICA on their website only says to lubricate at a specific interval and send them in for service at specified intervals, no other maintenance instructions. If your mechanic can't buy parts and mantenance data all you can do is send them in. Every other qution you asked is perefct for tech support. That's what the company pays the tech reps for...

Sometimes the sales reps at a booth don't know much about the service after sale.

SpeedBrake Tech Support
Dave Craig
Phone: 1-800-547-2558 Ext. 105
Email: dave.craig@preciseflight.com
Dave Mollman
Direct line: 1-541-585-2421
Email: dave.mollman@preciseflight.com
Adam Robirts
Direct line: 1-541-585-2428
Email: adam.robirts@preciseflight.com
Pulselite Tech Support
Doug Creach
Phone: 1-800-547-2558 Ext. 112
Email: doug.creach@preciseflight.com
 
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Cpt_Kirk said:
I don't mean to hijack the thread, but do they have that much of an effect on the aircraft? I've always wanted to ask.
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I have them on my Mooney. Yes, it's drag with an on/off switch. I can get 2000+fpm descent and keep the speed in the green, but unlike the flaps there's no max speed for use. They don't have much of an effect really slow either.. you can go around with them out.

In the summer, I like to stay up where it's cool until I get close, put the speed brakes out and "minimize my time in the descent".
 
Cpt_Kirk said:
I don't mean to hijack the thread, but do they have that much of an effect on the aircraft? I've always wanted to ask.
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On a draggy airframe like a 182, I doubt they'd do much although I did hear of a skydive 182 that had 'em installed to get down and get the next load of jumpers that much faster.

On the Mooney, they're very useful. Here's a few examples:

1) If you do nothing else - No trim, configuration, or power changes - Putting the brakes out gives you about a 500fpm descent. Great when IFR for doing short descents - Just hit the switch (on the yoke), let the plane descend on its own, and 50-100 feet above the target altitude just hit the switch again and you're once again perfectly configured in level flight.

2) If you need to slow down in a descent and you're still above gear speed, you can use them to get down to gear speed without needing to level out. Mooneys don't like to slow down and go down at the same time! I usually cruise around 170 KTAS up around 7,000 feet plus or minus, so I'm indicating about 150 KIAS. When I start descending (about 6 miles out for every 1000 feet I need to come down, depending on winds), I'll pick up another 10 knots or so. 20 miles out, I reduce to 22"MP. 15 miles out, 20". 10 miles out, 17". 5 miles out I'll still be doing 155 KIAS when I reduce to 14". Usually, after being at 14"MP for a couple of minutes the plane will slow enough to put the gear out, but if there's less headwind or more tailwind during the descent than expected, it's nice to have the brakes there to keep the descent going while slowing to gear speed.

3) If you end up high and/or hot on final, you can save yourself a go-around by popping them out. I usually retract them prior to the round-out because if they're still out you are either still too fast (in which case a go-around is advisable unless you've got a really long runway in front of you), or you're descending at a steep angle where the round-out is going to start earlier and/or happen faster, usually resulting in a firm arrival. In a short-field situation, though, that can be desirable.

4) I always put them out right after touchdown to take advantage of aerodynamic braking while I'm still going fairly fast. Hopefully it saves me money on brake pads...

I never flew with them before the Ovation, but they're a nice tool to have. They don't cause as much drag as extended landing gear - Maybe half as much - but they cause enough at high speeds to be about equivalent to full flaps at slower speeds and you can put them out at any speed (my gear speed is 140 and flap speed is 110).

Another tool in the box, but of course, another system to maintain.
 
I would really like speed brakes on the 310. It's a lot like the Mooney in the sense that it doesn't like to slow down and go down at the same time. Actually it doesn't like slowing down at all.
 
Ted DuPuis said:
I would really like speed brakes on the 310. It's a lot like the Mooney in the sense that it doesn't like to slow down and go down at the same time. Actually it doesn't like slowing down at all.
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So how do you slow down then? Forgive the newbie question just wondering how you deal with that.
 
Just pull the throttle back. A mooney has no problem slowing down. A pilot used to a plane with more drag has a problem slowing down. :)
 
Our club J's have these speed brakes disabled. Nice but not worth fixing when they brake.
 
I wouldn't have a problem with my A&P fixing anything as long as he wants to and has knowledge about it.

Sounds like precise flight is using scare tactics for $$$$.
 
Hocky said:
So how do you slow down then? Forgive the newbie question just wondering how you deal with that.
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It's just a matter of planning. I'll plan a 500 fpm descent, which is about the level of descent I can do without a significant power reduction without exceeding Vno. Then I add in 1"/minute manifold pressure reductions. I usually end up getting to the airport around 17" and 180 MPH IAS. Level off to slow down a bit. I can extend first 15 degrees of flaps at 180, gear and full flaps at 160.

The main thing is I avoid exceeding Vno in descent because I try to follow the part about the yellow arc being for "smooth air only".
 
The "siezure" behaviour and incomplete retract could be a limit switch issue (assuming they use limit switches).

If they do use limit switches, check their operation AND for chafed wires and shorting.
 
Mistake Not... said:
Just pull the throttle back. A mooney has no problem slowing down. A pilot used to a plane with more drag has a problem slowing down. :)
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I don't necessarily believe in shock cooling, but since there's no real drawback to pretending it exists just in case, I don't ever "just pull the throttle back".

Most flights, I only use the speed brakes after landing - After all, what's the point of a super-efficient airframe if you're just gonna throw energy out the door late in the flight? - But as you can see from my other post on the issue, there are plenty of times where they come in handy.

RotorAndWing said:
Don't get your hopes up on number 4.
Click to expand...

I'm sure the difference is miniscule - But if I have a 4000' runway, the speed brakes keep me from having to use the real brakes at all.
 
flyingcheesehead said:
Most flights, I only use the speed brakes after landing - After all, what's the point of a super-efficient airframe if you're just gonna throw energy out the door late in the flight? - But as you can see from my other post on the issue, there are plenty of times where they come in handy.
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I think the efficiency is the big thing. Where you run into the speed brakes being useful is on steep descents. Think going into busy Class Bs.
 
Ted DuPuis said:
I think the efficiency is the big thing. Where you run into the speed brakes being useful is on steep descents. Think going into busy Class Bs.
Click to expand...
Or in IFR, where you may not be able to decend early, or just want to descend thru the clouds quickly without going into the yellow.
I agree, if VFR you don't need them
 
I use the redneck speed brakes in the 182 ... push the doors open and wedge them open with a broomstick.

:goofy:

Jim
 
Apparently slips are prohibited in Mooneys. :rolleyes:
 
flyingcheesehead said:
Most flights, I only use the speed brakes after landing - After all, what's the point of a super-efficient airframe if you're just gonna throw energy out the door late in the flight? - But as you can see from my other post on the issue, there are plenty of times where they come in handy.



I'm sure the difference is miniscule - But if I have a 4000' runway, the speed brakes keep me from having to use the real brakes at all.
Click to expand...

On 4000' feet of runway if landed properly you wouldn't use wheel brakes even if you didn't have the speedbrakes. :rolleyes:
 
"airplane doesn't like to slow down" never made sense to me, clearly these defy physics.
 
dell30rb said:
Our club J's have these speed brakes disabled. Nice but not worth fixing when they brake.
Click to expand...

That's unfortunate. Owners can be blinded by a cheap buy-in price without looking down the road only to get screwed when the new shiny gizmo breaks.
 
RotorAndWing said:
On 4000' feet of runway if landed properly you wouldn't use wheel brakes even if you didn't have the speedbrakes. :rolleyes:
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Meh... I guess my landings suck then. :rolleyes: Or maybe it's just something I've always done. I also keep the nosewheel off as long as possible - And sometimes I do still need brakes, tho the runway is not level.

bnt83 said:
"airplane doesn't like to slow down" never made sense to me, clearly these defy physics.
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A plane that goes 170+ KTAS on 12 gph is pretty low drag. It's also over 3300 pounds, so pushes through the air in a descent pretty well. Reducing from 23-24" cruise power down to 17" in a 500fpm descent, I lose a measly 5 knots.

If I cut the engine, yeah it'd slow down. They're still subject to the laws of physics. But it will not slow down like a 182 at all. Again, physics.
 
I slowly back down to 12" in the Comanche and that seems to work.
 
I flew an F-22 Penguino that was for sale, and the owner did a high G turn to slow down ...

That was a nice bird, but it was one of only maybe two registered here. No parts, no production, and from Italy ... it was too much 'what if' for me to handle.

8150189142_d9a1eb381b.jpg
 
flyingcheesehead said:
I don't ever "just pull the throttle back".
Click to expand...

No wonder you need speed brakes. Next time, try pulling the throttle back. It's amazing what that'll do for your landing rollouts. Or do you just snag the third cable? :D

People kept warning me when I bought the plane that mooneys were hard to land, didn't want to slow down, were somehow more slippery than other planes. I've not found this to be true at all. If your only references are commonly available trainers (skyhawk, warrior, et al), then sure.. I'm lower drag. But I'm not -no- drag.. far from it. So I can't wait until turning base to slow down from cruise. Big deal. That's called "planning ahead" not "doesn't want to slow down".
 
To slow down you need to do 2 things, everyone seems to be forgetting the second thing.

1. Reduce Thrust
2. Hold Altitude

If you don't re-trim, all you are going to do is start a decent at pretty much the same speed it was trimmed at prior to thrust reduction.

Next point,

Ever dive at a runway only resulting in a long overshoot?

Ever come in too high about on speed, then pull the nose way up to INCREASE a decent rate?

High AoA = reducing wing efficiency...
 
Mistake Not... said:
No wonder you need speed brakes. Next time, try pulling the throttle back. It's amazing what that'll do for your landing rollouts. Or do you just snag the third cable? :D
Click to expand...

Hah! :rofl:

I normally have 6 power reductions prior to the final closing of the throttle prior to landing: 22" at 20 miles, 20" at 15 miles, 17" at 10 miles, 14" at 5 miles (that's as far as I can pull it back without the gear warning going off). Once the gear is down, back to 2000 RPM, mixture and prop forward, and that's also a good pattern-level setting. Descent from TPA is at 1500 ± adjusted as necessary, then at 50-100' AGL throttle closed.

People kept warning me when I bought the plane that mooneys were hard to land, didn't want to slow down, were somehow more slippery than other planes. I've not found this to be true at all. If your only references are commonly available trainers (skyhawk, warrior, et al), then sure.. I'm lower drag. But I'm not -no- drag.. far from it. So I can't wait until turning base to slow down from cruise. Big deal. That's called "planning ahead" not "doesn't want to slow down".
Click to expand...

Mooneys are NOT hard to land... They're just less forgiving than a trainer. Come in 10-20 knots too fast like many CFI's seem to teach and you're gonna have a bad time. You're exactly right, descents must be planned. They are "slippery" though, that's why they're so efficient and why you have to plan descents. But when things don't go according to plan, the speed brakes are a nice tool to have.

Reminds me of a friend who was being taught how to fly a DA40, and the CFI had him going 90 KIAS on final with half flaps! :eek: Book technique is 67 and full flaps. When I told him to slow down and use full flaps, suddenly he had great landings. And that plane had a prop strike a few months earlier. Gee, I wonder why.
 
Ever find out repair cost on the speed brakes? I don't think they are that difficult to R&R but Precise Flight might be expensive.
 
flyingcheesehead said:
Hah! :rofl:

I normally have 6 power reductions prior to the final closing of the throttle prior to landing: 22" at 20 miles, 20" at 15 miles, 17" at 10 miles, 14" at 5 miles (that's as far as I can pull it back without the gear warning going off). Once the gear is down, back to 2000 RPM, mixture and prop forward, and that's also a good pattern-level setting. Descent from TPA is at 1500 ± adjusted as necessary, then at 50-100' AGL throttle closed.



Mooneys are NOT hard to land... They're just less forgiving than a trainer. Come in 10-20 knots too fast like many CFI's seem to teach and you're gonna have a bad time. You're exactly right, descents must be planned. They are "slippery" though, that's why they're so efficient and why you have to plan descents. But when things don't go according to plan, the speed brakes are a nice tool to have.

Reminds me of a friend who was being taught how to fly a DA40, and the CFI had him going 90 KIAS on final with half flaps! :eek: Book technique is 67 and full flaps. When I told him to slow down and use full flaps, suddenly he had great landings. And that plane had a prop strike a few months earlier. Gee, I wonder why.
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Go to 14" earlier, check the descent rate, cut the decent rate by 75% by retrimming.
 
EdFred said:
Go to 14" earlier, check the descent rate, cut the decent rate by 75% by retrimming.
Click to expand...

I do re-trim to keep the descent rate at 500 fpm, and if I didn't have speed brakes I'd probably do as you describe. But, just like I avoid speed brake use because I don't want to waste the efficiency of the Mooney, I also avoid reducing power too early because I don't want to waste the speed either. Somewhat of a paradox, but having that tool available when necessary (probably 20% of the time or less) means that I don't need to slow down too early to ensure that I can get slowed down.

I wish I had some sort of indicator of the prop blade angle and torque - Usually I'm at 160 KIAS through most of the descent and I get to about 155 by the time I'm reducing to 14" but it slows noticeably better at that setting than the previous ones, so I'm wondering if somewhere between 17" and 14" at that speed is where zero thrust is and that 14" is actually turning the prop into a bit of a brake.
 
My WAG would be the 0 point would be when the prop control no longer changes RPM.
 
I've never flown a long body, but I think I'd rather have no speed brakes and an extra 6lbs. of useful load. :)
 
MSPAviator said:
I've never flown a long body, but I think I'd rather have no speed brakes and an extra 9lbs. of useful load. :)
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FTFY

Q. DOCUMENTATION​
Before performing flight tests it is recommended you complete the calculations for weight and​
balance and revise the equipment list showing installation of Precise Flight SpeedBrakes™ at 9-lbs.​
at 133.0 in. FAA Form 337, section 8 “Description of work accomplished”.
 
This is noteworthy:
Yearly:

Remove SpeedBrakes​
TM from aircraft​

d.)​
Clean and Inspect unit for damage, corrosion, looseness & proper operation​

e.) Lubricate worm and worm gear with Lubriplate. DO NOT USE SPRAY LUBRICANTS!

Every 50 hrs

Check drain tubes for debris​
​
​
​

​
​
Every 1000 hrs

​
.) Return SpeedBrakes​
TM to Precise Flight Inc. for​

Clutch Lubrication and Spring Replacement

Every 5000 hrs

d.) Return SpeedBrakes​
TM to Precise Flight Inc. for​

Drive Assembly Replacement


https://preciseflight.com/resources/doc/08059_Mooney_M20__M22.pdf
 
bnt83 said:
FTFY
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Thanks! 9lbs. is even better. I think what is really lacking in the long body IO-550 Mooneys is useful load. Mooney should come up with VGs, revised flaps, or something else to get the useful load up to more like 1100-1200lbs. like other planes with the big six cylinder engines.
 
Cirrus, Mooney (big ones) , Corvallis, Columbia : Big engine + Thin high speed wing, fast, efficient, = low full fuel payload


Everything is a compromise.

205 will carry about 80 gallons of fuel and ~1000# in the cabin with a lowly 260 hp, but it won't go 170 knots.
 
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Looking at the empty weight of a Falcon 7X which is limited to 19 passenger cabin seating per e-exit requirements.
Empty Weight: 34,936
Gross Weight : 70,000
Useful : 35,064
Fuel Cap: 31,940 pounds (4,766 gallons)
Full Fuel Payload: 2996
Two crew required: at least 340
Crew bags ~60
Payload = 2596 ~ 15 passengers with NO bags, food & refreshments etc.
 
EdFred said:
My WAG would be the 0 point would be when the prop control no longer changes RPM.
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Doubt it. If you push the nose over enough and have the throttle low enough, you could have the prop off the low-pitch stops while developing negative thrust (ie drag). Zero thrust is a somewhat more complex equation than that. You have to take into account airspeed, engine power, prop setting, etc... It'd be measured easiest via torque, but I've never seen a torque meter on a piston single.

MSPAviator said:
I've never flown a long body, but I think I'd rather have no speed brakes and an extra 6lbs. of useful load. :)
Click to expand...

Meh... That's a gallon of fuel. (or a gallon and a half with the actual 9-pound weight). Since it's impossible to even fuel the plane accurately to within that much, IMO the weight is in the realm of noise. Their usefulness is not.
 
flyingcheesehead said:
Doubt it. If you push the nose over enough and have the throttle low enough, you could have the prop off the low-pitch stops while developing negative thrust (ie drag). Zero thrust is a somewhat more complex equation than that. You have to take into account airspeed, engine power, prop setting, etc... It'd be measured easiest via torque, but I've never seen a torque meter on a piston single.
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But if you pull the RPM back even further, I bet it changes. Which means it was still producing drag - and you haven't reached your zero point.
 
EdFred said:
But if you pull the RPM back even further, I bet it changes. Which means it was still producing drag - and you haven't reached your zero point.
Click to expand...

If you're in cruise and you pull the prop back, the RPM changes... Does that mean it was producing drag?

Now, let's say we're at a relatively high RPM/low MP setting in level flight, right on the edge of the governing range for the prop (and thus at the low-pitch stop). Clearly we are not at zero thrust in that situation, as the engine is still keeping the plane in the air.

If we're right at zero thrust in the descent with the prop set at cruise RPM, pulling the prop back will increase blade pitch and the prop will slow down unless we're already at the coarse pitch stop. If we push the prop forward, it'll speed up unless we were already at the fine pitch stop.

Now, let's say we are at zero thrust and just barely touching the fine pitch stop in the descent with 14"MP / 2200RPM. We push the prop forward and nothing happens. But if we were already getting a little bit of drag (ie, negative thrust), we push the prop forward and it still won't change RPM despite us not being at zero thrust to start with.

I think finding the exact zero thrust point for a 155-knot, 500 fpm descent at 2200 RPM would involve first getting close via experience and feel, and then starting with the same MP and slightly lower RPM. Then, change RPM slowly until it starts increasing and then stops. If it stops at 2200, then you were right about the zero-thrust point - If it doesn't, adjust MP, stabilize and try again. Lotta variables to control for, though, so I'm not entirely positive this would work.
 
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