REFLECTOR: barn door speed brake

michalk michalk at awpi.com
Tue Oct 17 17:59:31 CDT 2006 

This was discussed a long time ago.

How about a force activated switch.
Think of a spring that can travel about 1 inch, and when compressed that 
inch, exerts the maximum force you would want to subject to your 
brake/actuator.

When the spring is extended, it let's you do whatever you want to the 
speed brake.  When it's compressed, a switch is triggered that tries to 
retract the brake.

One could easily test the maximum forces worst case on the ground.  Just 
press against the farthest edge of the brake until you hear crackling 
noises, and set your switch to actuate before you get to that point.

That said, unless the hinges fail, I don't think the brake would break 
in half.  It would crumple in compressive failure across the line of the 
actuator hardpoint.

Terry Miles wrote:
> Geez.  I was thinking the opposite...to re-enforce the panel with 
> embedded whatever to keep it from snapping in two aft of the jackscrew 
> attach point.
> Terry
> 
>     -----Original Message-----
>     *From:* reflector-bounces at tvbf.org
>     [mailto:reflector-bounces at tvbf.org] *On Behalf Of *Scott Derrick
>     *Sent:* Tuesday, October 17, 2006 10:29 AM
>     *To:* Velocity Aircraft Owners and Builders list
>     *Subject:* Re: REFLECTOR: barn door speed brake
> 
>     Scott,
> 
>     Actually I was considering drilling some large holes through my
>     existing brake to reduce the pressure but allow for a higher speed
>     brake.   But decided to work on increasing the gear extension speed
>     instead.. 
> 
>     Scott
> 
>     Scott Baker wrote:
> 
>>I'm thinking that a "half" size speed brake for RG models, with a higher 
>>deployment speed, might be a drag option for enroute descents.
>>Anyone else have thoughts on this?
>>SB
>>
>>----- Original Message ----- 
>>From: "Terry Miles" <terrence_miles at hotmail.com>
>>To: "'Velocity Aircraft Owners and Builders list'" <reflector at tvbf.org>
>>Sent: Monday, October 16, 2006 8:55 AM
>>Subject: Re: REFLECTOR: barn door speed brake
>>
>>
>>  
>>
>>>John,
>>>
>>>Thanks for the comprehensive reply on the SB issues.  It sounds like our
>>>situations are similar.  To add to your knowledge base, and as best I
>>>recall the conversation with Scott Baker, the factory encourages the
>>>"all or none" on speed brake deployment, but I too have a momentary "on"
>>>for the deploy side and will probably count in my head over having a
>>>gauge showing degree of deployment, but that's a good idea.
>>>
>>>I also asked SB, and I would guess many have before me, on the notion
>>>about lessor angle ought to mean higher speed limit.  Baker declined to
>>>speculate, and added a warning to me about the panel going thru the prop
>>>if the envelope was pushed beyond tolerance.  He did mention no attempt
>>>was made by Velocity to test the high end of the speed range for the SB.
>>>As I recall it he said that they decided 110 was safe and pegged it at
>>>that.  ...or you might say a traffic pattern speed control device and
>>>not designed for arrival descent use, or ATC requests to increase rate
>>>of descent.
>>>
>>>Terry
>>>
>>>-----Original Message-----
>>>From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
>>>Behalf Of Paula & John Schoorl
>>>Sent: Thursday, October 12, 2006 12:50 AM
>>>To: Velocity Aircraft Owners and Builders list
>>>Subject: Re: REFLECTOR: barn door speed brake
>>>
>>>
>>>Terry:
>>>Too add a little more info to Craig's reply about our XL-5FG with speed
>>>brake:
>>>Our max extension angle is about 75 degrees.  Chap 14 recommends not to
>>>exceed 60 degrees.  How we ended up that way was we converted to the
>>>cutdown keel halfway through the build and had to adjust our actuator
>>>position to make it work.  It resulted in more extension angle than we
>>>originally had. It also resulted in the actuator being installed in a
>>>nearly vertical position which makes for a not very good load path from
>>>door through actuator to keel.  On my to do list is to do the math and
>>>figure what loads our actuator is seeing in our configuration versus the
>>>book installation.
>>>
>>>Our test pilot likes to fly his final approach with the speed brake
>>>extended so he can keep more power in and have better engine response.
>>>I tried the same technique but was not very comfortable with it and my
>>>landings showed that.  I went back to flying without it like I was
>>>primarly taught at the factory and my landings improved greatly.  Once I
>>>am more comfortable in the airplane I will probably go back and
>>>experiment with the speed brake some more, especially to shorten landing
>>>distance.
>>>
>>>As a side note to the discussion about rapid descents with gear or
>>>brakes
>>>extended:  The factory airplane wires the speed brake so it is either
>>>fully extended of fully retracted.  I assume this air load on the door
>>>and into the actuator and keel is what drives the 110kts speed brake
>>>limitation. Craig and I wired our speed brake so the brake only extends
>>>while you hold the switch down so we can extend to any angle we want by
>>>how long we hold the switch (we have a position indicator on the panel).
>>>Flip the switch up and the brake retracts completely for a go-around, in
>>>case your wondering. While I'm figuring out loads on the brake, I also
>>>intend to look at whether I can get away with a shallower speed brake
>>>angle at a higher speed than 110 and get the benefit of the drag for a
>>>higher rate of descent.  Thats an engineering problem for down the road
>>>if I don't convince myself its a bad idea before then.
>>>
>>>Hope that wasn't too much information....
>>>John Schoorl
>>>XL-5FG
>>>Palmdale, CA
>>>
>>>-----Original Message-----
>>>From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]On
>>>Behalf Of Terry Miles
>>>Sent: Wednesday, October 11, 2006 1:31 PM
>>>To: 'Velocity Aircraft Owners and Builders list'
>>>Subject: Re: REFLECTOR: barn door speed brake
>>>
>>>
>>>Thanks you guys.  ...and thanks Jorge.  The only one I could half way
>>>measure looked to be between 55 to 60. Terry
>>>
>>>-----Original Message-----
>>>From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
>>>Behalf Of Craig and/or Denise Woolston
>>>Sent: Wednesday, October 11, 2006 8:32 AM
>>>To: 'Velocity Aircraft Owners and Builders list'
>>>Subject: Re: REFLECTOR: barn door speed brake
>>>
>>>
>>>I'd say our extension angle is around 60 degrees.  I honestly can't
>>>remember right now if the manual said to limit it or not.  The test
>>>pilot landed with it down every time, but I haven't used it yet.
>>>
>>>Craig
>>>XL-5FG Flying in Palmdale, CA
>>>
>>>
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>>
>>
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>>
>>
>>  
> 
> 
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> 
> -
>     "Just because I sound like an idiot doesn't mean I agree with the president."....from an ad on Air America Radio
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