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How do you use your Speed Brakes?


MBDiagMan

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23 minutes ago, Oldguy said:

On my post-engine start checklist...

Issue is that (in my aircraft) they get inadvertently triggered during "controls free and correct" pre-takeoff...If you have a yoke switch, I would recommending checking them as one of the final items during pre-takeoff checklist

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2 minutes ago, Stephen said:

Issue is that (in my aircraft) they get inadvertently triggered during "controls free and correct" pre-takeoff...If you have a yoke switch, I would recommending checking them as one of the final items during pre-takeoff checklist

I check my controls before I get in the plane.  I leave the baggage door open so I can see the yoke while I move the elevator.  I can see the yoke through the window while I move the aileron.  No need for me to be moving the yoke prior to takeoff.

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I used to own a '78 J that didn't have them, and never felt I was missing anything. It took a few hours to learn how to manage the energy effectively, but after that I could easily slip into the SJC 30L ILS between two jets in the conga line from LA and "keep the speed up to the middle marker", sidestep to 30R and make the first exit after landing -- all with reasonable maneuvers and power reductions.

Recently, I purchased a '94 J with electric speed brakes and I find that, on occasion, they are handy. But after reading some threads, on speed brake maintenance, and noting that the previous two owners of my airplane had sent them back to Precise Flight for overhaul twice in 1150 hours, I've decided that it may be most cost effective to reserve them for cases where I truly have a need. I remember reading this somewhere:

Controller: Cross XYZ at 10,000

Airline pilot: That's going to be pretty difficult from our present position and altitude

Controller: Don't you have speed brakes on that thing?

Airline pilot: Yes, but those are for my mistakes, not yours.

Skip

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On 2/14/2019 at 10:34 PM, Shadrach said:

Speed brakes are located in the area of boundary layer separation at climb AOA. The reason they work for Don right after touchdown (I’ll take his word for it) is that the wing is at low AOA on roll out. Go out and give it a try, your bird will climb just fine with them deployed.

Thank you Ross.  Your detailed technical and diagrammatic explanation is appreciated as is your knowledge.  Also to everyone else who chimed in.

I'm never too old to learn.

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17 hours ago, Stephen said:

Had an electrical issue and had a single speed break deploy on takeoff. When I do the controls free and correct the speed break deployed on one side due to the placement of the switch on the yoke. The break that deployed was on the down aileron side and I was looking for an up aileron on the other wing so didn't see it since the break was stowed on the wing under observation. After I rotated, really hard yaw into the break... though I got slammed with a X-wind gust, but it persisted and stabilized...didn't feel like a gust. Immediately lowered the nose to keep airspeed and saw the single break out and stowed it. I have now modified my pre-takeoff list to check both breaks. Sent units back to precise flight for overhaul (obviously). When landing with them out with close to no-wind, I can land about on the numbers and stop at the indicated spot to make the first turnoff. It was experimental, 80MPH over the fence and heavier breaking.  You have to drag it in under power, so I thing this would probably be something to think about to limit ground contact energy in making an off-field landing. Wouldn't & don't do it or recommend it for normal course of ops , but was good to know what the plane will do. 

 

1579578359_ScreenShot2019-02-14at11_46_21AM.png.e29243a3e0b778e1e24570082e2bb419.png

I’m surprised to read this. They are placed where they are on the wing so as to prevent adverse yaw at high angles of attack (e.g. lift off).  The speed brakes are in an area of turbulent flow until AOA is reduced as in cruise or descent. 

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47 minutes ago, Shadrach said:

I’m surprised to read this.

Asymmetric board deployment introduces a yawing moment which is noticeable but controllable. More noticeable at higher speeds. The newer ones have an auto-retract feature. It senses a differential in the rates of deployment and will retract them.

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15 hours ago, Stephen said:

Issue is that (in my aircraft) they get inadvertently triggered during "controls free and correct" pre-takeoff...If you have a yoke switch, I would recommending checking them as one of the final items during pre-takeoff checklist

Fortunately/unfortunately, my switch is mounted on the panel right in front of me. I have been looking for the yoke mount for the switch with no success as its current position requires removing a hand from the yoke for deployment and retraction.

Panel (2).jpg

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Been waiting for someone to test asymmetric deployment at takeoff. Thanks for the pirep :)

Speed brakes work by increasing the parasite drag. Parasite drag predominates at higher airspeeds. At best glide speed (L/Dmax) parasite drag and induced drag are equal, and below this speed induced drag predominates. So, adding additional parasite drag from the speed brakes has less effect at lower speeds.

Skip

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1 hour ago, Oldguy said:

Fortunately/unfortunately, my switch is mounted on the panel right in front of me. I have been looking for the yoke mount for the switch with no success as its current position requires removing a hand from the yoke for deployment and retraction.

Panel (2).jpg

I'd be mad that someone slipped with the drill.  Then did not fix it.  And did not use a centerpunch.  And then did not placard it.

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24 minutes ago, PT20J said:

Been waiting for someone to test asymmetric deployment at takeoff. Thanks for the pirep :)

Speed brakes work by increasing the parasite drag. Parasite drag predominates at higher airspeeds. At best glide speed (L/Dmax) parasite drag and induced drag are equal, and below this speed induced drag predominates. So, adding additional parasite drag from the speed brakes has less effect at lower speeds.

Skip

That’s a good point Skip.  Also, I remember reading a Mooney NTSB report (I can’t rememebr which one) where the pilot had veered off the runway on landing and cited a cause as only one speedbrake being deployed which caused a yaw to one side.  Either Precise Flight or Mooney responded by saying the brakes were tested on landing and takeoff with only one in the up position and it did not have a material effect on maintaining directional control.

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ATC at my Home 'Drome seems to think there is no problem having IFR traffic on a VFR day fly a close-in downwind at 3000 feet above pattern altitude and then clear them for a base turn and visual approach.  For Mooney drivers speed brakes are our only chance to salvage the situation and avoid the Penalty Box ("Extend your downwind to follow Airbus traffic on a 10 mile final")  So much for the concept of a stabilized approach!

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7 hours ago, Davidv said:

That’s a good point Skip.  Also, I remember reading a Mooney NTSB report (I can’t rememebr which one) where the pilot had veered off the runway on landing and cited a cause as only one speedbrake being deployed which caused a yaw to one side.  Either Precise Flight or Mooney responded by saying the brakes were tested on landing and takeoff with only one in the up position and it did not have a material effect on maintaining directional control.

9 hours ago, Shadrach said:

I’m surprised to read this. They are placed where they are on the wing so as to prevent adverse yaw at high angles of attack (e.g. lift off).  The speed brakes are in an area of turbulent flow until AOA is reduced as in cruise or descent. 

The speed brakes themselves may not be familiar with the placement theory ;) because it definarely yaws, and that got my attention. It was both noticable and controlable.

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When I teach people to ski they seem to miss that too.   If you ski uphill you will slow down and even go backwards.

Agree with this (currently Myoko Japan)
I will always lower speed brakes once gear is down.
I use them on decent approaching cloud.
Use them at the FAF to get to gear speed.
Use them when given a “reach alt by” (9000 by bla bla)
Definitely don’t use them at night near a thunderstorm at 19000’ to slow due to severe turbulence -they will ice up and won’t retract. Ask me how I know - Atc held me there until I “required lower”
There were heavy jets holding all over the place due to the storms overhead their airport. I was just a bystander traversing their airspace.
It was 75f on the ground and no ice remaining for landing.



Sent from my iPhone using Tapatalk
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8 hours ago, whiskytango said:

ATC at my Home 'Drome seems to think there is no problem having IFR traffic on a VFR day fly a close-in downwind at 3000 feet above pattern altitude and then clear them for a base turn and visual approach.  For Mooney drivers speed brakes are our only chance to salvage the situation and avoid the Penalty Box ("Extend your downwind to follow Airbus traffic on a 10 mile final")  So much for the concept of a stabilized approach!

Mid-bodies handle a full cross controlled slip just fine. You can slow it down and then bring it down (my preference) or you can bring it down and then slow it down. Trying to do both at the same time rarely works out. 

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