REFLECTOR: Speed brake usage question

[Scott Baker]

Great question.  When N94VA (the factory training aircraft) was based in California, the speed brake was hooked up with a momentary down switch with a spring return to the middle (neutral) position - the switch had an up position that stayed in position.  I liked the ability to select partial speed brake deployment (ala the older Cessna's with the "one thousand one, one thousand two, one thousand three ... that aught to be about 20-degrees" wing flap switch).  When I joined Velocity in Florida, N94VA has a new speed brake switch - that being an all-or-nothing selector.  This started a series of discussions between the various pilots as to which type of switch is best.  The consensus boiled down to this -
1) Since the aircraft can do a go-around and climb with the speed brake fully deployed - it was agreed that the "full down" speed brake posed no safety problem.
2) The speed brake is most effective when it is in the full-down position - and marginally so when partially deployed - giving fuel the "all or nothing" vote.
3) The flight instructors liked the idea of the "set it and forget it" (all or nothing) switch to keep pilot training load to a minimum.
4) Unless there is microswitch in place to alert the pilot that the speed brake is down (or partially down), it would be easy for a pilot to forget that the speed brake is partially deployed (having the switch in the center position adds to the possibility of this oversight) - This was brought up in argument of the "all or nothing" switch.

Both systems will work.  I think that most builders select the all or nothing system.
Best regards,
Scott B.
  ----- Original Message ----- 
  From: Kufalk 
  To: reflector at tvbf.org 
  Sent: Sunday, November 07, 2004 11:12 AM
  Subject: REFLECTOR: Speed brake usage question


  I have never flown an airplane with a speed brake.  Is there ever a situation where you would want to extend the speed brake only partially down?

  I am looking at switches to actuate the speed brake and I am thinking about one that has a spring return to center for the down position.  Then I could run it just like the flap switch on a Cessna 150.  If I want 30 degrees of brake, I would hold the switch for 3 seconds.  (The actuator moves the brake panel about 10 degrees per second to a maximum of 60 degrees)  In the up position it would stay there and retract all the way on it's own.  I would install the switch just above the throttle so I could reach it with my left index finger when my hand is on the throttle.




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