Hi! Nigel/all
My two pennyworth .....I also tried a cowl exit flap but not to close
off. My Jabiru cooling system of course was ALL air cooled and the
theory ventured by the Jab dealer and Factory was to extend it into the
air stream and create a low pressure area aft of the cooling exit to
suck out the hot air..... needless to say it made no improvement
whatever. However what I did find was that it was important to maintain
top cowl pressure high to promote the mass down flow of air past the
engine, I even collected my cabin heating air(when not being used for
purpose) and dumped it in the cowl top which also assisted. Since all
the high pressure oil cooling air was directed under the sump cooling
fins(Rotax oil and water cooling likewise) to leave it "floating" in the
lower cowl restrained the downward flow of engine cooling air.
You may ask why am I "rabbitting on" about damn Jabiru's ?.... so to my
question:-
What purpose do the Europa "Gills" serve?
Has anyone flown with them blocked off to check the effects?
As it happens, against most advice, I have decided to fit an intercooler
on my 914 Turbo which of course has a huge discharge of warm air mostly
into the top cowling and I'm not sure it's the right philosophy to let
it exit out the "gills", with my Jabiru experiences I'm suggesting that
to increase the down flow of air, even with water and oil cooling on the
engine, it would be best maintaining the top cowl pressure.
I never had any top cowl exits on my Jabiru set up ...all air was
discharged out the lower cowl exit plus the lower cowl was "jacked" off
the fuselage by approx 1" increasing the discharge annulus considerably.
Any help with these questions would be gratefully received.
I also would have liked to have the Rotax oil flow to its cooler
selectable and/or meterable which I achieved on the Jabiru by a hand
control valve operated from the P1 Position allowing most flying to be
accomplished without the cooler being in circuit. The resultant warm air
(even with no oil circulating though the cooler) was a primary source
of cabin heat and with the oil cooler in full flow I could fry the
passenger, I get the feeling that a number of Europa Rotax owners would
dearly like such a facility !
Regards
Bob Harrison G-PTAG (Still prepared to learn!)
-----Original Message-----
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of nigel
charles
Sent: 15 November 2006 09:38
Subject: RE: Europa-List: Oil cooler thermostat
>It is best to place a flap at the exit of the cowl/radiator duct.
Placing an obstruction in the front destroys dynamic pressure. An we
need to recover as much pressure as we can to persuade the air to flow
across the rad core.<
For what its worth I tried a cooler flap at the rear of the radiators.
With it fully closed it cut off nearly all the airflow and it made
little difference to the CHT and oil temperatures.
When I was at Vichy this year I met one of our French owners (sorry I
forgot his name). He has a very clever inlet cowl flap. It is part of
the lower cowl in front of the radiators and has a hinge at the rear of
it. In very hot weather it is lowered below the normal cowl allowing
more cooling air in. In cold weather it is raised impeding airflow to
the radiators. This is all controlled from the cockpit so that inflight
adjustments can be made. From what he told me it works very well.
I appreciate that normally control of cooling air is best done at the
outlet but in this case it seems it is better to use the inlet.
Nigel Charles
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