REFLECTOR: Questions for those already flying

[Rene Dugas]

I think if I were plumbing my heat system I would make my Heater flapper
in the front oil cooler duct seal completely and make another that is in
front of the cooler the place a bilge blower in the air line between the
pilot and copilot footwells and suck air out of the cabin thru the hot
oil and back into the cabin.  This would save the addition of another
cooler in the cabin and accomplishes the same thing by only adding an
aluminum flapper upstream to the nose cooler.

Rene'

 

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of John Dibble
Sent: Thursday, March 15, 2007 10:29 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Questions for those already flying

 

  

Jack Prock wrote: 

Hi, A couple questions for those already flying... If you didn't install
a speedbrake, if you were to do it again would you install it? 

I didn't build, so I don't know how much work is involved to install.  I
did use the speed brake at first when I was learning how to land.  After
over 300 hours, I haven't used the brake in probably over 150-200 hours.
The only time I might use it is on a short field with an obstacle to
clear.  So to answer your question, you will probably wish you had it at
first, and not care later on. 
  
  If you did install a speedbrake, are you glad you did? Do you use it
often? I have heard that with RG's it is hard to heat the cabin at
altitude and/or winter. If you could doit again, would you still cut the
NACA for the oil cooler? I have heard people using two coolers,one near
the engine to be used during the summer,  and another in the nose thatis
used as a heater during the winter. Any thoughts? 

This is a complicated issue. 

I have the Franklin, 220 hp.  I can think of  2 factors that affect the
oil cooling requirment. 
1)  The higher the CHTs, the hotter the oil going to the cooler.  I have
very good cooling with CHTS in the 120-140 C range in summer.  I have 4
1/2" ducts for the cooling air and I think larger ducts (and scoops) are
a good idea. 
2) The higher the rpm that you run at, the more cooling you will need,
because the oil pump is a constant displacement pump, so the amount of
oil going to the cooler is porportional to the rpm that you operate at.
I run the Franklin at 2600-2700 rpm.  At first I ran it at 2400 rpm and
my oil temps were about 5-10 C cooler. 

Adequate cabin heating for an RG needs these 3 things. 

1) The flap in the cooler air exit duct must fully close to get maximum
heat from the cooler. 

2) The edges of the nose gear doors must be "sealed" with silicone
sealant. 

3) The engine CHTs must not go too low (>80 C) during the winter. 

I'm still working on #3.  Trying do decide if I want to make something
to restrict engine cooling air in the winter that works automatically,
or something I install each winter and remove in the spring. 

As far as oil cooling is concerned, I think 2 coolers are necessary.  I
am currently installing an ADC oil filter which also functions as a
cooler.  Although the installation would have been easier, I decided not
to install one near the engine because 1) when solo I am at the aft cg
limit and I don't want to add more weight in the rear.  Further
installing the filter in the nose is a plus for cg considerations.  2)
I need all the heat I can get from the oil, so it has to be in the nose.
I am mounting it on top of the standard oil cooler and tieing the exit
air in with the existing exit duct.  I believe the existing duct is
large enough to handle the additional air flow.  The fresh air is coming
from a NACA on the co-pilot side that currently isn't used for anything.

  
Hope this helps. 

John 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  Thanks, Jack Prock 

 





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