REFLECTOR: IFR Flight

Lawrence Epstein ljepstein at hotmail.com
Mon Oct 31 15:56:37 CDT 2011


Remember, the fuel is vaporized in the carb and therefore the heat of
vaporization is consumed and the temperature drops. Increased fuel
flow=decreased temperature. In addition, as air passes thru the Venturi, it
accelerates, also cooling it.

OAT is only marginally relevant below about 50 deg F. Ambient Vapor content
is the critical factor.

Larry Epstein (Not the same Larry, although I think he was saying this as
well)

On Mon, Oct 31, 2011 at 12:02 PM, Jones Nick <nick.jones at volvo.com> wrote:

> Larry,****
>
> ** **
>
> I agree completely except for the cool damp air thing. About a hundred
> years ago when I started flying a C-150 doing a cross country during summer
> over central Virginia, just passed KRIC on the way to the mountains.
> Noticed the RPM going down, tried leaning, engine ran rough, richened the
> mixture, engine ran rough. Left it alone and turned back to RIC for a
> precautionary landing. When I was within gliding distance pulled carbheat, engine stumbled and roared to life. It was 80°F at altitude, 98%
> humidity. It was like flying in a milk bottle. Carb ice can happen in
> warm air too.****
>
> ** **
>
> Best regards,****
>
> ** **
>
> Nick and Connie Jones****
>
> Velocity XL-RG****
>
> N10CN****
>
> 99% done 90% to go****
>
> ** **
>
> *From:* reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] *On
> Behalf Of *Laurence Coen
> *Sent:* Friday, October 28, 2011 1:26 PM
> *To:* Velocity Aircraft Owners and Builders list
> *Subject:* Re: REFLECTOR: IFR Flight****
>
> ** **
>
> John,****
>
>  ****
>
> Water doesn't freeze at 11C.  If it did you'd have ice on the wings, not
> in the carb.  The vaporizing of fuel drops the temperature in the carb and
> causes two things to happen.  Since you were flying in rain it's pretty
> safe to assume that the humidity was high.  The cooling from the fuel
> vaporizing  condenses water vapor into super cooled droplets which freeze
> instantly when they come into contact with the internals of the carb.  Cool
> dry air, no problem.  Cool damp air, carb ice.****
>
>  ****
>
> Larry Coen****
>
> N136LC****
>
> ** **
>
> *From:* aminetech at bluefrog.com ****
>
> *Sent:* Thursday, October 27, 2011 4:34 PM****
>
> *To:* Velocity Aircraft Owners and Builders list <reflector at tvbf.org> ****
>
> *Subject:* REFLECTOR: IFR Flight****
>
> ** **
>
> Today I did my first real IFR flight direct from McPherson, KS to Ocean
> Springs, MS.  There was VFR weather at both ends and IFR in the middle.  I
> learned a few things.  In the clouds my speed decreased by 5 kn.  Is this
> typical?  My IVO prop performed flawlessly and helped a lot with the speed
> variations.  I replaced the motor brush torsion springs with stronger ones
> and that seems to keep the motor working, so far.  In rain the plane
> pitched up and down a lot.  In moderate to heavy rain the A/P couldn't
> maintain altitude within 100 feet and I had to assist it.  The rain showers
> lasted only 10-15 min, each.  I was happy about that as I didn't want to
> have to fight it for an hour.  Also, water dripped on my feet during the
> heavy rain.  I'll have to seal the canard joints somehow.  The OAT and carb
> temps were both 6 C initially and gradually increased to 11 C as I
> progressed farther south.  I was wondering about carb icing, but it was
> raining, so I figured I was ok.  My MAP began at 20.5", and slowly
> decreased over 1 1/2 hours.  When it go to 19", I knew something was wrong
> because I've never seen it that low at 9000'.  So I applied carb heat and
> the MAP immediately dropped 1/2".  Then it slowly increased for several
> seconds.  Then the engine stumbled for 1/2 sec and then the MAP jumped to
> 21".  So there was some ice there.  Now I know that water freezes at 11 C
> in OK and AR.  My understanding is that you can't fly IFR through MOAs, yet
> I went through 2.  The last hour I was out of the rain and could have
> climbed and went VFR, but I decided to continue going in and out of cloud
> tops for experience.  It was quite bumpy and next time I'll climb and go
> VFR.****
>
>  ****
>
> I met a guy at the McPherson airport who knows someone who just bought a
> Velocity with a rotary engine.  Is that your's, Al?****
>
>  ****
>
> John****
> ------------------------------
>
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