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XL V-speeds

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a.s.elliott(at)cox.net
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Posted: Fri Jan 02, 2009 10:36 am Post subject: XL V-speeds

Gang:

  

 I have completed some testing on my 190 (3.1L) Corvair-powered  XL taildragger and have some V-speed numbers to report.  These were taken  with the wheel pants on, but no intersection fairings.  Tests were done  around 4000' DA, at a weight near to 1120#.  My plane has an empty weight  of ~790#.   

  

 It seems that the large, relatively thick wing gives very  tightly grouped V-speeds more like a Cub than an RV.  Note  that the deck angles for V_x  and V_y are quite high (> 20°) and  uncomfortable to maintain.  I tend to use 90-100 MIAS for normal operations  climbs, which still gives plenty of climb rate.  Note that response curves  are also very tight, and the performance falls off very rapidly, even  just a few MPH from these speeds, so airspeed control would be *very*  important in an engine-out situation.

  

 Also note that control authority, and therefore also trim  response, is very dependent on power setting at all airspeeds.   It is not possible in my plane to trim off the elevator at low glide speeds with  the power off, but the stick loads are light.  It is possible to trim off  the low climb speeds.  Anyway here you are:

  

 V_md (minimum descent rate) = 68 MIAS

 V_bg (best glide ratio)     = 70  MIAS

  

 V_x  (best climb angle)     = 72  MIAS

 V_y  (best climb rate)       = 74 MIAS

  

 FWIW,

 Andy Elliott, Mesa, AZ

N601GE,601XL/TD,Corvair

  

   [quote][b]

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amyvega2005(at)earthlink.
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Posted: Fri Jan 02, 2009 12:47 pm Post subject: XL V-speeds

Dr. Elliott

If in power off the plane should trim at best glide automatically at 70 mph. most planes will as mine does.  IN an emergency you should be able to trim all the trimm to full up, and focus on correcting the problem.  Are you saying yours does not trim to  Vx or Vb? (should be the same)



I have on mine with 750 lb empty weight,   Vx 52 mph,  Vy 71 mph. Vy equals Best glide. 71 mph.

 stall no flap is 48.   Best glide should be 1.30x Vx or 52x1.30= 68 mph.



Juan



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