In contemplating a reserve tank the following considerations arise. If the
tank reaches to the bottom of the baggage compartment and a siphon arrangement
is used, clearly this can only equalise the levels. To transfer all the fuel
it would be necessary to proceed in a sequence of ever decreasing steps
(theoretically an infinite number !). It would therefore appear to be
desirable to mount the tank entirely above the top of the main tank (over the
baggage compartment), freeing the baggage space, leaving accessibility from
both sides and allowing the use of a standard type tank instead of a
specially shaped one. (I am waiting for Europa to tell me if there is a
vertical consideration in the c.of.g position)
An alternative is to provide some way of pressurising the reserve tank. This
is not at all difficult and would allow the tank to be at any height. e.g. I
have just run wifey's car vacuum cleaner into a manometer and it produces a
head of 8 inches, which is deeper than the full 25 ltr tank. Or one could
tap off the pitot line - the same pressure is available there at 110kts.(with
a non-return valve in case something goes wrong and the ASI flills with fuel
!)
More than 25 ltr in the baggage compartment makes the c.of. g. go too far aft
(in G-EMIN) if solo, and above AUW if 2-up. But with a pressure system and a
tank on the passenger seat one could carry a "passenger worth" of fuel (23
gal/51 ltr) before using any of the baggage allowance. That makes a total of
150 ltrs on board, good for 12 hrs and 1200 nm ! Now where's the portajohn ?
Graham G-EMIN
PS I have a feeling there have been many solutions to the problem of moving
fuel about since the aeroplane was invented.
|