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There are four  rules to making a hot start without making a fool
out of yourself:

1) Get the fuel pump cooled off; and

2) Make a normal start.

3) Any other method **may** work. That includes Voodoo.  
No other method is inherently designed to work.  

4) See Rule 1 & 2.



If the magnetos are working properly,  then hot starting problems are NOT a
function of which magneto or gizmo you are using on the spark end of the
deal.

I have investigated this issue in some detail, using an appropriate
engineering approach and scientific method.

A recently shut down hot engine will cause the accessories to rise to a
temperature of about 210 to 220F about 30 minutes after shutdown in a closed
hangar with no ventilation when the OAT is about 100F. Been there, done
that, measured that.  That includes the fuel pump.  The core of the fuel
pump is even hotter.  Avgas flashes to vapor at a temperature lower than
that.  If you put your bare pinkies on the case of the fuel pump you will
burn yourself!


The *****************  ONLY   *************   issue with respect to an
engine being harder to start when very hot verses when not very hot is that
the fuel pump core is so hot that it flashes fuel to vapor rather than
pumping liquid.

Period.  Parade rest.  That is, honest folks... the
ONLY issue.

You cure that issue by  pumping fuel through the
fuel pump for .... NOT 15 or 30 seconds,  but at least 60 seconds and maybe
as much as 90 or more.  When it is cool enough, you can momentarily put your
finger on it without burning yourself.  You simply must cool off the
interior core of the fuel pump sufficiently so that it will not flash fuel
to vapor when it starts to pump when the engine fires.

That is the problem.  The only problem.  If you think it is something else,
then  I would like to hear an explanation of what it is and why.

Really....   this is the only problem.   I fly an average of four to six
different turbocharged Bonanzas (and a further variety of other high powered
turbocharged certified and experimental aircraft ) each month during turbo
installs and R & M here in Ada, Oklahoma.  It is about 100F outside today.

In almost every case, I have to start them right after the mechanic has been
out on the runup pad operating the engine at full power in order to verify
the fuel flow and manifold pressure set up.   Worse, he has to get the oil
temp fully up to operating temperature in order to properly set the absolute
pressure controller.   In the summer time,  I typically "enjoy" the
advantage of getting into the airplane about 20-30 minutes after that full
power ground run up,  and at least  two or three mechanics are standing
around with their hands over their mouths watching to see if I will make a
"hot start fool" out of myself, and worse, often the owner is in the
airplane with me when I say  ".... let me show you hot to do this...it works
every time..." and then I have to prove it.

I am sure it is going to fail me... sometime.  And I will become
embarrassed, no doubt!  

But so far, it has not.

Regards,  George Braly


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