Speed brakes for landing

[midlifeflyer]

I searched the forum but too many different types of speed brake questions to figure out which might be useful...

Reading through the M20R POH supplement on the speed brakes, it describes landing with speed brakes if the approach is too high. The description is of a marginally higher airspeed, a more nose low attitude for the descent itself, and a more rapid rotation in the landing flare to compensate.

As someone who has not used speed brakes, It kind of strikes me, from a practical standpoint, as somewhat like a forward slip in the sense that I would want to use the speed brakes to get down to a point where I could remove them and land normally, rather than land with them extended. Of course, I could be completely off base.

So I'm wondering what SOPs you guys who actually use them follow. When deployed, what kinds of situations, when retracting after deployment.

Thanks.

[gsengle]

The brakes do almost nothing at slower speeds. In fact part of their approval is you can go around fine with them still extended and that asymmetrical deployment is not a problem.

In my R I find that they do little at under 90 kts and almost nothing over the runway.

Don't plan on them helping you during short final and flare.


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[Rszent]

Generally I use the speed brakes to land and leave them on all the way down to the runway,, they do very little below 90 knots but do help in the float. My base airport has a hill with a obstacle clearence light center line of the runway on 1/2 mile final,,some have accidently found it at night and crashed,, thats another story....so with a steeper decent thease birds dont hesitate to pick up speed so yes I use them..

[75_M20F]

If it is windy I land with them out. Cuts down on the floating when I just want to get the airplane on the runway.

[gsxrpilot]

34 minutes ago, midlifeflyer said:

As someone who has not used speed brakes,

You should really go out and try them.  First use them at altitude and learn how they affect a decent. Then once comfortable, use them in the pattern or on Final, and then all the way to the runway. It's also useful to know approximately how quick they deploy and retract.

They can certainly be useful with our slippery birds.

[peevee]

IIRC on our precise flights they're as you say, no limitations.

I have landed with them out, inadvertently. I don't remember noting anything unusual, demonstrated by the fact that I forgot to stow them and didn't notice.

Edited January 29, 2017 by peevee

[carusoam]

Non-CFI response.... pp thoughts only...

The Speed brakes disrupt airflow and lift over a swath of the wing... a few times wider than the brakes themselves.

This eliminates the lifting ability of that swath...

It seems to me it is similar to shortening the wing, from a lift point of view.  All the resistance of the wing is there and then some.

less lifting wing results in a slightly higher AOA increasing the induced drag...

All of this is related to airspeed.  

- The brakes are incredibly effective at dissipating energy at high speeds.

- They are much less effective at slow speeds.

- they suffer from brain load like all other switches during the cognitively busy time. The same button raises and stows them it is hard to know if they are deployed or not without looking at them, while you are busy with track, bank, altitude, descent rate, Airspeed.

- Go around... Best stowed. If they are stuck up, partially up, or asymmetrically deployed, fly the plane...

Not CFI ideas, only pp thoughts...

Best regards,

-a-

[Bennett]

While I agree that speed brakes become less effective with lower speeds, I use them to some degree in most landings, and keep them deployed on rollout. The electric units pop in and out so quickly that they can be used to "fine tune" the last few hundred feet before the flare. I fly out of a 2600' runway, which means you don't want to float down it with excessive speed. With full flaps, and speedbrakes deployed, and in no headwind landings, it is easy to roll off the runway below 1000' from the approach end. This means that touchdown occurs just as the stall warning starts to sound, and the red light in the CYA-100 AOA lights. I've had speed brakes on all three of my Mooneys, and I find them to be a useful tool. I also find them valuable when having to descend rapidly to get under closely spaced Class B rings where topography limits getting lower too soon. I know that some MS members regard speedbrakes as a crutch for "poorly planed descents", but I have no problem using them as just one more tool in flying. By the way I have a light on my panel that lights up when the speedbrakes are deployed, but at high speed, the rumble alone, and the instant perceived speed reduction makes their deployment quite obvious-and you always look out on the wing.

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[gsengle]

They really do next to nothing at slow speeds/higher angle of attack.... don't get a false sense of security that they do much when landing.

And you won't notice them a bit if left up on go around - that should tell you something...


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[peevee]

to be honest, I'm more concerned about using them at high speed, as they're only connected to the airframe via the screws at the top and two small bolts at the bottom, and only to the wing skin.

[milotron]

I try not to rely on them, but do use them when required. i have accidentally left them on (despite the bright amber indicator light...) during landing on a slam dunk approach with no ill effects.

Very little, if any effect on  the ground though.

The definitely can be used both ways: increase rate of descent at a fixed forward speed OR decrease forward speed at a given rate of descent.

[DVA]

Here's the good news on the speed brakes installed on our Mooney's - they only work when they're suppose to work and that's very well at air speeds higher than you normally see on approach, landing and initial climb out, and at those low speeds the do nothing that will hurt you.

Some would argue that they have a subtle but beneficial effect in the flair and during gusty approaches ... I think I agree with them.

I've landed with them out on purpose and accidentally, windy and calm, fast and slow. I did a "WTF ... deer!" low go around with them out (forgot to retract them ... was busy going to the bathroom) and the plane flew fine.

My opinion is that I'm glad I have them. I would suggest that you experiment on a long runway to see how they affect your style of landing. But I would not make them a routine part of my normal landing procedure - we have enough to do at that very instant.

[jlunseth]

I generally only use them in two situations.  One is the cram down you sometimes get from ATC where they want you to descend several thousand as though you were a pressurized turbo or jet.  The other is if I am at cruise and entering a cloud where I suspect turbulence, and I need to get to design maneuvering speed quickly.  

You can land with them no problem.  Don Kaye, I believe it was, wrote a piece on this site a few years ago about their performance.  His one piece of advice was not to deploy them on short final unless you have some practice, because it can result in an immediate loss of 50 feet or so in altitude.  I have never found it to be a problem, but I have some practice with them.

[LANCECASPER]

1 hour ago, peevee said:

to be honest, I'm more concerned about using them at high speed, as they're only connected to the airframe via the screws at the top and two small bolts at the bottom, and only to the wing skin.

If you are exceeding Mach 1 in your Mooney I'd be concerned. On the six Mooneys I've had, one had vacuum speed brakes and four of them had electric speed brakes. On the 1983 231 I had it would have been nice to have had speed brakes since it was the first time I'd flown in the flight levels and had to deal with slam dunk descents at times.

I've never even noticed a loose screw on any of the speed brakes I've had. They are solid as a rock. Your landing gear doors are much more likely to fly off than your speed brakes. (but that's no reason to leave your landing gear retracted on descent and landing . . lol)

[gsxrpilot]

I have the vacuum driven version (wishing I had electric) and have deployed them at close to cruise speed, which in my 252 is respectable. 

Once when held quite high by ATC over the top of AUS and then handed off to the HYI tower for a straight in to 17.  MP back to 16", speed brakes out until gear speed, then gear out, and dove for the ground at max gear speed. I got to pattern altitude only about a mile off the end of the runway, slowed to flap speed, deploy flaps and with over 5000' of runway, got it on the ground and off at the last taxiway.

They are nice to have and easy to use.

[peevee]

15 minutes ago, LANCECASPER said:

If you are exceeding Mach 1 in your Mooney I'd be concerned. On the six Mooneys I've had, one had vacuum speed brakes and four of them had electric speed brakes. On the 1983 231 I had it would have been nice to have had speed brakes since it was the first time I'd flown in the flight levels and had to deal with slam dunk descents at times.

I've never even noticed a loose screw on any of the speed brakes I've had. They are solid as a rock. Your landing gear doors are much more likely to fly off than your speed brakes. (but that's no reason to leave your landing gear retracted on descent and landing . . lol)

I think my main beef is they're only connected to whatever gauge that wing skin is, it doesn't seem very strong, especially to deploy them at high speed cruise. I figured they'd at least butt up against the spar, they don't.

[DVA]

If you are exceeding Mach 1 in your Mooney I'd be concerned.

Excellent, finally a replacement thread for other beat up controversial issues like LOP, TiT and CHT temps.

I'll start.

When I exceed Mach 1 in my Bravo, my cabin vents leak a bit, anyone else have this problem?

:/)

[midlifeflyer]

2 hours ago, gsxrpilot said:

You should really go out and try them.  First use them at altitude and learn how they affect a decent. Then once comfortable, use them in the pattern or on Final, and then all the way to the runway. It's also useful to know approximately how quick they deploy and retract.

They can certainly be useful with our slippery birds.

That's the plan and the reason for my question. 

Thanks for all the responses. Keep 'm coming  

[gsxrpilot]

Just now, peevee said:

I think my main beef is they're only connected to whatever gauge that wing skin is, it doesn't seem very strong, especially to deploy them at high speed cruise. I figured they'd at least butt up against the spar, they don't.

Is there really that much force against them? With all the holes in them, I figured they were more about disrupting lift, or as @carusoam said, shortening the wing. I can't imagine there's much force from the wind pushing against them.

Just a PP, not an aerospace engineer.

[midlifeflyer]

43 minutes ago, jlunseth said:

Don Kaye, I believe it was, wrote a piece on this site a few years ago about their performance. 

Thank you! I found Kaye's piece on speed brakes on his website, http://www.donkaye.com/donkaye.com/Use_of_Speed_Brakes.html 

[DVA]

Is there really that much force against them?

They're rated for deployment at any speed up to Vne.

[peevee]

12 minutes ago, gsxrpilot said:

Is there really that much force against them? With all the holes in them, I figured they were more about disrupting lift, or as @carusoam said, shortening the wing. I can't imagine there's much force from the wind pushing against them.

Just a PP, not an aerospace engineer.

stick your hand out the window at 180 indicated (ignoring the placard...) and you tell me.

the more stuff I look at on how these things are built, the less I want to fly GA. LoL.

Edited January 29, 2017 by peevee

[midlifeflyer]

27 minutes ago, donkaye said:

All you ever wanted to know about using speed brakes:

http://www.donkaye.com/donkaye.com/Use_of_Speed_Brakes.html

Yep found it and posted it three posts ago. Thanks Don. Just what I was looking for.

[mike_elliott]

5 hours ago, DVA said:

 

 

Excellent, finally a replacement thread for other beat up controversial issues like LOP, TiT and CHT temps.

I'll start.

When I exceed Mach 1 in my Bravo, my cabin vents leak a bit, anyone else have this problem?

:/)

 

You need to get the SB done on the Bravo to replace the cabin vent with the Mach 2 Acclaim cabin vent.

[BradB]

if you want an idea of what the speed brakes do to airflow, put them up in the rain and look at the water flow.