Great Frans
"I advanced the
throttle to 100% (not 115%) and got over 155 knots
IAS worth out of it
on my freshly calibrated ASI,"
Congratulations for that; next upgrade your very
speedy cannon to Mono and meet even VNE (165
knots) during the low level flight.
"broke my smallest toe by bumping into
my wife unintentionally (honestly!)"
I recommend you to try next time your biggest tool
intentionally instead of a smallest toe
unintentionally.
Raimo
do archive
-----Alkuperinen viesti-----
From: Frans Veldman
Sent: Tuesday, March 13, 2012 10:01 PM
Subject: Europa-List: Rotax 914 starting problems
when hot
<frans@privatepilots.nl>
Hi everyone,
I guess I'm not the only one having this problem.
The main problem here
is that I don't understand why it is happening.
If I arrive at an airfield in hot weather, I can
restart either right
away, or after a considerable time. If I just
refuel without having a
meal, I get into a time window where the engine
has difficulties starting.
It is a vapour lock problem of some sort, but I
don't know how this can
happen. Sure, the inside of the cowling is hot and
residual heat from
the turbo is, without the large fan upfront
turning, cooking the fuel.
But I thought that the 914 is supposed to be
immune from the problem.
Up to the pressure regulator the fuel is recycling
when I switch on the
electric fuel pump. Any vapour up to the pressure
regulator is directed
back into the tank and being replaced by fresh and
cold fuel.
The carb bowls might have been cooked empty, but
then the floats will
have dropped and fresh fuel will pour in as soon
as I switch on the
pumps. The fuel line between the pressur regulator
is not recycled but
if it contains vapour then it will escape via the
opened carb needle and
not raise the floats, so it will gently escape
until being replaced by
liquid fuel, being driven there by the electric
pumps.
So... why won't then darn thing just start?
Yesterday I was exactly experiencing this problem.
After arriving at an
airport to go to the service center for the
bi-annual pitot and static
systems test, and with the engine switched off for
about ten minutes I
couldn't restart it. No matter how long I kept the
fuel pumps running,
applied choke, (just in case the mixture was too
lean) or was just
cranking with the throtthle wide open to vent the
cylinders (in case it
was too rich), the engine would just crank without
even a faint single hit.
So I abandoned the plan to taxi to the refueling
station, and had a
lunch instead. Of course after that the engine
started up right after
just a half turn of the prop...
So... why is this happening? I'm interested in
solving this problem, but
primarily I want to know why this is happening
because according to my
reasoning it shouldn't be happening in the first
place. What am I
missing here?
Oh BTW, on the return home I got caught by non
predicted early set in of
night fog, with a very rapidly dropping cloud base
(never seen it
falling that fast). With my home base being the
closest and most
promising airfield once I got forced down to 500
feet I advanced the
throttle to 100% (not 115%) and got over 155 knots
IAS worth out of it
on my freshly calibrated ASI, which was quite an
experience so low over
the ground. At my homefield I arrived less than 15
minutes later with
the local cloud base still at 1000 feet (as
announced/predicted by ATC
half an hour earlier), but I was thankful
nevertheless to have been able
to speed out of that threathening situation that
fast. If it weren't for
the obligatory static/pitot test to renew my
airworthiness review
certificate I wouldn't have been flying at all
that day, so much for the
bureaucrats that want to enforce my safety this
way. Anyway, the
pitot/static systems worked flawless (I would have
had noticed it myself
it if they weren't) and I'm good to apply for
renewal of the desired
certificate.
All this while I had unwittingly broke my smallest
toe by bumping into
my wife unintentionally (honestly!) and was
undergoing this flying
experience with some discomfort to enhance the
flying experience even
further. At least the latter problem has been
diagnosed correctly today,
so now I just want to get diagnosed the vapour
lock problem as well. Who
can shine some light on this mystery?
Frans
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