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From: William R. Bayne [mailto:[EMAIL PROTECTED]
Sent: Sunday, December 25, 2005 11:51 AM
To: Ed Burkhead
Subject: WRB Re: [COUPERS-TECH] Usable fuel / Datum
RLYTECH
Hi Ed,
I doubt if the fuel pickup point in the fuselage tank would change sufficiently to materially affect usable fuel; and I would expect any such change would be an increase as fuel moves aft. Nose angle might make more difference in usable wing tank fuel, and I would certainly rock the wings and trim the plane nose high in the process of coming down so as to get the last possible drops from that source. Anthing you get in this manner is additional...a gift. I would not consider such "additional" fuel as "usable" for flight planning or fuel management purposes.
Perhaps it's because I have been through the experience described that I want to be aware of my fuel consumption, progress along course, and emergency options realistically within range. I know where I am, how much fuel I am burning that day on that course at that altitude and my ground speed. Even over the rough areas between Albuquerque and Phoenix there are airports, strips and open areas well within range if I know within 1/2 gallon of when I'm "on" the nose tank and have a chart.
I have considered putting a flow sensor on the fuel pump outlet activating a light on the panel and an audio warning in the headset when flow ceased. This "alarm" system would annunciate automatically each flight between the time the switch is "On" and the engine starts, initiating such flow. It would be of primary advantage to the complacent, though.
On the other hand, if I were Pilot In Command over water en route to the Bahamas and suddenly aware of a fuel pump failure, I'd switch to maximum range speed to stay aloft as long as possible and lean as much as possible (experimenting with a bit of carb heat) while keeping the engine going. I'd probably elect to stay at cruise height so as to have the best glide range and accept the challenge of landing in the water without power.
At that point, and with that scenario, I would be so far out of my documented operational experience as to acknowledge being unable to predict with any precision when the fan "should" quit. On the other hand, that event would have been delayed to to the extent within my power and well beyond when it would otherwise occur. The laws of physics will ultimately prevail.
Regards,
William R. Bayne
<____|-(o)-|____>
(Copyright 2004)
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On Dec 25, 2005, at 9:07 AM, Ed Burkhead wrote:
Bill,
Excellent procedure for accurate measurement of the unusable fuel.
Here’s a thought: If I’m low on fuel, flying on the nose tank and the gauge is visibly headed downward, I’m probably NOT going to fly at cruise speed.
Most likely, I would be flying at maximum range speed, somewhere between 75-90 mph. Naturally, I’d be much more nose-up. Perhaps it’d also be worth making the unusable fuel measurements at that angle-from-level, if you’re going for the really accurate measurements anyway.
Just a thought.
As a second thought, I’d probably be making a precautionary landing on a highway or in a nice field with the assurance of continued power long before the difference in angle-from-level of the tanks becomes important.
Ed Burkhead
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