Today's Message Index:
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1. 07:39 AM - fuel range of a stock CJ? (Elmar & Manuela Hegenauer)
2. 08:11 AM - Re: fuel range of a stock CJ? (Larry Pine)
3. 09:17 AM - Re: fuel range of a stock CJ? (Brian Lloyd)
Message 1
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| Subject: | fuel range of a stock CJ? |
I have read Brian's recent posting about
the fuel range of a stock 285hp CJ.
As far as I am understanding is that 42 US gal.
would give you 3.5 hrs of flight time + 30 min.
reserve, but these numbers differ from the ones
stated in my handbook and my own experience :-(
What exact speed, rpm and MP would translate
in that kind of range?
Thank you in advance.
cheers
Elmar
Message 2
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| Subject: | Re: fuel range of a stock CJ? |
I think you should find out Scott Andrews' secret.- He has a CJ with an M
14P and always lands with more fuel than he departed with!-- On long jo
urneys he has to crack open one fuel cap to vent the excess fuel.- All th
is while cruising a 175kts and the engine just above idle- :0P
Just giving Scott- some crap!
Larry Pine
--- On Tue, 1/17/12, Elmar & Manuela Hegenauer <samira.h@shaw.ca> wrote:
From: Elmar & Manuela Hegenauer <samira.h@shaw.ca>
Subject: Yak-List: fuel range of a stock CJ?
>
I have read Brian's recent posting about
the fuel range of a stock 285hp CJ.
As far as I am understanding is that 42 US gal.
would give you 3.5 hrs of flight time + 30 min.
reserve, but these numbers differ from the ones
stated in my handbook and my own experience :-(
What exact speed, rpm and MP would translate
in that kind of range?
Thank you in advance.
cheers
Elmar
le, List Admin.
Message 3
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| Subject: | Re: fuel range of a stock CJ? |
On Tue, Jan 17, 2012 at 7:37 AM, Elmar & Manuela Hegenauer <samira.h@shaw.ca
> wrote:
> samira.h@shaw.ca>
>
> I have read Brian's recent posting about
> the fuel range of a stock 285hp CJ.
>
> As far as I am understanding is that 42 US gal.
> would give you 3.5 hrs of flight time + 30 min.
> reserve, but these numbers differ from the ones
> stated in my handbook and my own experience :-(
>
> What exact speed, rpm and MP would translate
> in that kind of range?
>
I found that the CJ6A with a stock engine, is most efficient around
11,500'. I used to operate at full-throttle, 1950 RPM, and leaned to peak
EGT. I would have opted for lean-of-peak operation but the engine would
surge. (I suspect that the carb was out of adjustment but without a
flow-bench to test it, I couldn't verify.) The resulting fuel burn was 11.5
GPH. Assuming a usable fuel load of 40gal, this results in a
duration-to-empty of 3 hours and 28.7 min. (My apologies for stating as 3.5
+ 0.5. The 3.5 stuck in my head.) So the actual number is 3hr + 30 min
reserve. TAS is 130 kts yielding a no-wind range of 390nm. With a
reasonable tailwind of 20kts flying eastbound I would regularly fly 450nm
legs. By flying this way and carefully picking my fuel stops, I could
usually eliminate two stops in a coast-to-coast flight. I could also do
many flights non-stop where otherwise I would be making an intermediate
stop.
So, even though you are flying about 10kts more slowly, eliminating a stop
makes a big difference by eliminating lost time allowing you to arrive at
your destination sooner.
Caveat: you have to verify your own fuel burn over several hops to confirm
you are getting consistent results with these power settings. I also
recommend using these hops to verify the accuracy of your fuel gauge. I
found that mine appeared to be stingy by about 7%, i.e. the fuel in the
tanks was about 7% more than what the gauge read. What this does is make
you nervous about mid-way through the flight as you think you are going to
be about 15min short on fuel. But as you press on (making sure you have
intermediate landing spots) you will find that your fuel burn according to
the fuel gauge is converging on your original calculation. (You do carry an
E6B and do fuel-remaining-at-destination calculations, don't you?) Part of
this is due to the increased fuel-burn during initial climb. Regardless,
the goal is to accurately determine the average fuel burn at maximum range.
It is truly amazing what you can learn about your airplane if you are
diligent about doing your own flight testing and data collection. I find
that most pilots do no know their own airplanes very well and leave a lot
of performance on the table when flying them. Knowing your airplane's real
performance can provide you a substantial safety factor you didn't know was
there.
--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian@lloyd.com
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)
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