CorvAircraft> Primer -Cold Weather

[Dave Morris "BigD"]

Hi Doug, I'll give you the only data point I can at this time, which 
is my 47 year old Lycoming O-360-A1A four cylinder engine, built in 
1960 (pre-Corvair even!) and fed with an MA-4SPA carb underneath the 
engine.  This is a carb with an accelerator pump (or throttle pump 
for purists) and no separate primer.  It has been overhauled twice, 
and now has 1300 hours since the last major overhaul, so it's not 
exactly a spring chicken any more.

I've started the engine cold without any problems, including in New 
Mexico in temperatures that were so cold, my high-tech ADC oil filter 
went into Bypass mode, sending the oil directly through a bypass 
without filtering it, because it was too thick to pass the 
filter.  On a couple of occasions it was 25 degrees and I did not 
have the advantage of having my oil sump heater plugged in.  (I now 
plug it in anytime it's even threatening to be near freezing, just to 
keep the oil thin.  Some Alaskan pilots heat their oil at home and 
pour it into the plane warmed up.)

I have always been able to start the engine the same way, whether it 
is hot or cold:  Mixture full rich, electric fuel pump on, pump the 
throttle 3 times (which in the cold weather takes some effort!), wait 
about 15 to 30 seconds, then set the throttle to about 1/2 inch open, 
and hit the starter.  It has never failed to start.  I won't say it 
starts the way a VW does on the first half blade, but it starts well 
before I would start getting uncomfortable.

But William Wynne would have a lot more data on starting a Corvair 
engine with an accelerator pump.  I was encouraged to read in his 
manual his recommendation that one dispense with the primer and use 
the SPA carb instead, because it eliminates the need to have 
pressurized fuel in the cockpit.  Now he does live in Florida, but I 
imagine he knows people who have used that configuration in much 
colder places as well.  Call his hangar and ask him about it.

Dave Morris
www.N6030X.com


At 08:19 PM 1/9/2007, you wrote:
>I'm curious what the general consensus is of using a MA3-SPA for 
>starting a Vair motor in cold weather conditions.  Quoting the late 
>great Tony Bingelis from his book "On Engines" (p.164), "An aircraft 
>engine is almost impossible to start in cold weather without the 
>help of a primer system.  This is true even of the engine equipped 
>with a carburetor that has an accelerator pump."  Are there 
>significant differences between Vair motors and true aircraft 
>engines that make the Vair easier to start in cold weather with only 
>a accelerator pump equipped carb like the MA3-SPA?  I'd prefer to 
>use my MA3-SPA without the additional weight and complexity of a 
>primer system, but maybe the cold weather/emergency benefits of 
>having a seperate primer would outweigh the cons.
>
>Doug N.
>Wittman Buttercup -Got Plans
>Arkansas
>dugnaylor at yahoo.com
>
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