Frank van der Hulst wrote:

 However, CNG has several disadvantages over petrol:

1. It doesn't produce as much power from the same engine

We found this offset in my wife's van because it doesn't need a catalytic
converter.

2. A tankful (where the tank is about the same size as the petrol tank
it replaced) gets you about half the distance

Worse than that.  I think a Gas co. employee told me volume wise it's 3
times as much for an equivalent BTU.  FYI, you fill up to 3000 PSI and tanks
are filament (Fglass) wound aluminum.

3. Getting CNG to the airport would be difficult

True.

4. Ignition timing needs to be different

My principal reason for even thinking about a CNG (compressed natural gas)
aircraft was for the reno racer.  The octane rating I see on the pumps at
the gas station says 130.  If you used a pressurized spar to hold your gas,
you would get some extra strength.  In the event of an emergency, you've got
a fuel dump option that actually gives you a few moments of thrust, nozzled
out the back of course (even more thrust if you ignite it ha ha).  And with
a turboed 3 rotor you wouldn't be approching the threshold of the rotary's
weakness, detonation and apex seal failure.  Just thougt of another
advantage, inverted fuel system, no need to design for gravity feed or fuel
pumps.  Plus, it's tough to flood, starts nice on a cold day too.  No nasty
blow by gunk...

Most fleet vehicles here make up for the cost of CNG conversion by not
having to repair/tune up their engines.

Just toying with ideas,

Chris Cosman

 
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