REFLECTOR: Questions for those already flying

[John Dibble]

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
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>   Thanks, Jack Prock
>
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