REFLECTOR: Riddle me this...

[Chuck Jensen]

Hiroo,
 
The OAT should be accurate on the ground but at speed, you may be 2 or 3
degrees warmer than ambient because of heat of compression.  The
high-dollar, sophisticated temp sensors on big jets compensate for this
and it may be coming near us in the future.

Chuck Jensen 
 
 -----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Hiroo Umeno
Sent: Thursday, May 31, 2007 1:02 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Riddle me this...



It is TAS.  I will have to see the OAT sensor.  It is located in the
fresh air intake NACA so it should be exposed to a lot of outside air.
The only reason it might be off that I can think of is that the
back-side is exposed to the nose area where the temp heat from the oil
cooler may heat up the back.  

 

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Scott Baker
Sent: Wednesday, May 30, 2007 7:29 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Riddle me this...

 

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 <mailto:humeno at microsoft.com>  

		To: Velocity Aircraft Owners and Builders list
<mailto:reflector at tvbf.org>  

		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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