On Feb 14, 10:15*am, Peter wrote:
WingFlaps wrote

Yes I've heard that argument but I'd like to add/offer a different
POV. What is really stressful for engines is constant power changes
and the temperature fluctuations that involves. Therefore if your
engine can do 150 mph on a german autobahn for an hour or two it
should have no trouble doing it for a 4 hour flight in a plane.

IMHO it is a matter of degree. No road car will be actually run at say
75% power for more than minutes - you would kill yourself. Rally cars
get through engines at great rates, often breaking one in one race.
Whereas an aero engine just sits there the whole time at that power
setting. This may be just a matter of duty cycle but the end result
will be more stress and more wear.

The weakness of the certification regime is that the engine only has
to show 2000hrs at 100% power, and TBH you could probably get a lawn
mower engine to do that. Any engine that doesn't actually break (and
that is easy to achieve by design) and which meets the criteria (e.g.
starting at the certified ceiling) will be certified.

AFAIK there is no reliability requirement - that certainly applies to
avionics too.

I also
agree that marine installations pay no/little attention to weight
(some performance boat installations aim to keep weight low) but tha's
just a design thing. The natural rpm/torque curve for diesels seems to
match a prop better too. *

It may be but diesels have a lot more high frequency components in
their torque spectrum which plays havoc with props and gearboxes. So
they tend to need rubber shock absorbers.

The metals exists to make a diesel about the
same weight as a petrol engine so with a bit more hours under their
belt to identify weaknesses I can't see diesels not becoming the (?)
engine of choice (more range, less fuel quality issues). One more
think, no mixture control just rpm and pitch!

I agree but that is FADEC, not diesel. With FADEC on a Lyco you would
have similar benefits.


I was under the impression that diesels work by a governor that sets
RPM. The difference between desired rpm and actual rpm determines fuel
injected... In that case you could just set rpm and just adjust pitch
for speed/power. A single power knob (fadec) sets pitch and rpm
together?

Cheers