REFLECTOR: Riddle me this...

[Scott Baker]

Hiroo,
Question: Is the speed information that you give really true air speed, or the observed Indicated Air Speed?
If you are referencing indicated air speed, then one would expect lower figures at higher altitudes.
Note: If you have a Blue Mt. Avionics system (or other EFIS system) that calculates True Air Speed, please check the accuracy of the OAT sensor.  An inaccurate OAT will result in errors in TAS readouts. 
SB
    ----- Original Message ----- 

    From: Hiroo Umeno 

    To: Velocity Aircraft Owners and Builders list 

    Sent: Wednesday, May 30, 2007 2:39 PM

    Subject: REFLECTOR: Riddle me this...

     

    I put the wheel pants on and went out for another morning of flying.  As sky was severe clear, I took it up to 7500ft altitude (9300DA) and let the plane fly full-bore.  I clocked 165KTAS burning 11.5GPH but had to pull back as my #6 was getting too hot again.

     

    Here is when thing turned "interesting".  I backed down to the power settings that I "thought" produced 150KTAS a few days ago and found that I was getting only 140KTAS or so.  Since I put the pants on, I would have thought I would see some gains.

     

    The only thing I can think of is the fuel burn.  By then, I had 1/3 tank left on both tanks and the plane should be quite a bit lighter.  So, would a lighter plane fly slower?  Would CG have impact on my top speed?  I noted that I had to keep a bit of "down" trim during cruise (about a finger's worth at the elevator tip).  So part of me believes that when the nose gets lighter, the plane gets slower (to a point) because I am fighting the lift the canard makes to keep going straight.

     

    But the other part of me thinks that's bunk since how, given the same power input at the back, a heavier object can travel faster.

     

    Now I am totally confused.

     

    Hiroo


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