Bob,
My comment was a rather facetious throw-away, but as so often happens on
this forum, it sparked an interesting and well informed debate.
I had not considered the new generation of extremely lightweight
high-pressure wound-carbon composite tanks used for diving and
fire-fighting breathing apparatus.
If I think more seriously about applying LPG to aviation, there are a
number of drawbacks. LPG has a lower calorific value than AvGas
(producing about 45,000 kJ/Kg), meaning that you would have to burn
about 15% more to achieve the same work and that equates to a reduced
range or the need for a larger capacity tank to achieve an equivalent range.
Most auto installations have to be started on petrol (gas) before
switching to LPG, meaning that two fuel sources with appropriate
switching would need to be fitted.
I haven't even begun to consider how you would actually get LPG to your
aircraft!
Talking of alternative fuels/engines, I once got very excited when I saw
an APU turbine buried in the tail of a Chinook helicopter. This
minuscule engine belted out around 150 HP and weighed nothing. I
pictured it sitting in the nose of a Europa. Then I heard how much fuel
it burnt in an hour and realised that if it ever did power a Europa, the
endurance would be around half an hour with existing tanks.
Aviation is a pile of clever ideas finely balanced on top of
compromises. Just when you think you have found the perfect solution,
physics creeps up from behind and bites you on the bum!
Nigel
On 19/04/2011 15:36, Robert Borger wrote:
> --> Europa-List message posted by: Robert Borger<rlborger@mac.com>
>
> Nigel,
>
> In all seriousness, an LP tank can be constructed from composite materials
> and,
thus, be kept quite light. The issue with an LP thank is more form factor
than weight. It must be cylindro-spherical in shape making locating it within
an airframe more an issue. LP is also quite energy dense, even more than
diesel,
so it could be much smaller, lower volume, than a normal AvGas tank. Same
with LNG, another option in the same category.
>
> Frans,
>
> You may be correct that there will be composite LP (or LNG) tanks of more
> random
sizes. I have not seen them over here yet. Now all we need is to talk our
FBOs into storing another fuel type and figure out how to meter it so you don't
over fill. But that's all technical stuff and can probably be worked out.
I doubt you will see switch fuel aviation engines. Too much complication with
multiple carbs, plumbing, multiple fuel tanks, etc.
>
> Diesel engines, if it weren't for their weight issues, would be great as aero
engines. Gobs of torque at low to moderate RPM lets you swing a big fat air
mover at efficient RPM without complications like PSRUs.
>
> AvGas, as 100LL, isn't going away real soon. There just isn't a suitable
> replacement at this time and this fact has been recognized by the EPA and
> other organizations. 100LL WILL go away at some point in the future, but
> that point has not been set and, hopefully, won't be set till there is a
> suitable replacement. There are a few contenders for the title of 100LL
> replacement but only one appears to be making headway in the effort. 100SF
> (100 Swift Fuel) appears to be in the lead at the present time. It is in the
> production pilot plant stage of evaluation. More information can be obtained
> through the Wikipedia (search avgas) and at http://www.swiftenterprises.net/
> if you are interested.
>
> Bob
>
> On Apr 19, 2011, at 3:23, Nigel Graham wrote:
>
>> --> Europa-List message posted by: Nigel Graham<nigel_graham@m-tecque.co.uk>
>>
>>
>>
>> On 19/04/2011 07:32, Frans Veldman wrote:
>>> .....snip......
>>> ..... go straight to Diesel or propane. Here in the Netherlands about 1/3th
of the
>>> gas cars has been converted to run on propane (LPG)
>> .........and just how much does a propane tank weigh and what would that do
for the Europa's C of G and performance? ;-)
>>
>> Nigel
>
>
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