creightonious
Joined: 10 Mar 2007
Posts: 40
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 Posted: Thu Jun 07, 2018 4:15 pm Post subject: Leaning the 912/912S w/Airmaster and HACman |
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This is a diary of my experience with a Classic 912 over 2 years and several long cross countries and multiple legs at around 10,000ft msl.
They are my experiences only and might serve as a starting point for you.
ENSURE YOUR CARBS ARE WELL SYNCHRONIZED.
I raised the needles to richen the mixture slightly. The manual says that might be necessary.
Bing carbs provide a good mixture up to 4500msl.
The HACman links the venturi vacuum and the pressure (vacuum) in the float bowl through a tapered needle valve which varies the mixture as the pressures stabilize. This is not an instantaneous process. (Lest you think this is a non-aviation method of leaning, the Stromberg carbs fitted to all A-series Continentals used this system.)
At part throttle there is a significant vacuum at the venturi and mixture adjustment is positive.
At full throttle (WOT) there is very little vacuum at the venturi so the valve will be opened more in order to get a vacuum in the float chamber.
To lean:
1). Establish a stable cruise. Note MAP, EGT&RPM.
2) Maintain a stable cruise. SWITCH PROP TO MAN. Note MAP, EGT and especially
RPM.
3) Maintain a stable cruise.
Slowly screw out the mixture control, pausing every 1/2 turn or so. You want to
sneak up on the peak and as previously mentioned the response takes a few
seconds for the pressures to equalize.
Note RPM and EGT. Continue to screw out the mixture control, pausing every 1/2
turn.
4). Maintain a stable cruise. Note RPM and EGT.
When RPM drops JUST A BIT, note EGT and screw the mixture control in slowly
until RPM is restored. Note EGT and RPM. Peak EGTs will vary day to day.
Return prop control to AUTO.
Rotax are not approved for LOP operation so I go at least 50deg F rich.
My experience is that my 912 (at) 10,000MSL (at) WOT is all the mixture control can handle. Retarding the throttle a bit in order to get a little vacuum might increase the vacuum over the float and allow a bit more leaning, but then you haven’t got WOT any more.
Richen before changing power or altitude. If you forget once you won’t forget again.
It won’t hurt anything, but it is an attention-getter.
My experience is that at 10k and close to 1450 gross the burn is on the order of 3.8gph US at 123-128KTAS.
Need I point out that your mileage may vary?
Creighton Smith N96EG
| Quote: |
________________________________ Message 4 _____________________________________
Time: 05:31:28 PM PST US
From: Bud Yerly <budyerly(at)msn.com>
Subject: Re: Fuel management
Creighton uses the FC10.
Bud Yerly
Custom Flight Creations
From: owner-europa-list-server(at)matronics.com <owner-europa-list-server(at)matr
onics.com> on behalf of Mike Christine Duane <DuaneFamly(at)aol.com>
Sent: Tuesday, June 5, 2018 3:59:10 PM
Subject: Re: Fuel management
>
If I might ask, which totalizer did you chose?
Sent from my iPhone
> On Jun 5, 2018, at 7:27 AM, crouto <crouton(at)well.com> wrote:
>
>
> I tried it with just the footwell lndicator. Bubbles made it inaccurate.
I could purge it by horsing the airplane into a very steep zoom. The bub
bles could be seen climbing the gauge tube but in addition to the anxiety s
uffered by the passenger, it did not always completely purge the gauge syst
em.
> So I put in a totalizer and 1 red cube thinking I could factor in the ret
urn amount. I couldn=92t.
> So in went another red cube in the return line and, hey presto, fuel adde
d equals fuel used. I have a straight 912 and a long ranger tank. In a 24
gallon burn (indicated) the added fuel is within 0.3gallon less than indic
ated. I consider this a safety margin and have no plans to mess with it.
> The footwell tube is useful for indicating the aircraft is fueled, but in
the monowheel tail down stance it is not an accurate quantity gauge. By t
he way, since the installation of the long ranger the bubble problem seems
to have nearly disappeared. Go figure.
> Creighton Smith
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_________________
Creighton Smith
A 036 |
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