Bill Freeman wrote:

"There is little to be gained by advancing beyond 22 BTDC"?!?  Are certified
aircraft engine engineers really this stupid??  I know they are at the bottom
of their engineering classes (OTW they'd be making real money with real
companies) but geez.  Unfortunately, their expertize is in generating
certification reports -- not in engines.

Long live LSE and Electorair.  Digital electronic ignitions for homebuilders
in the $1K range.  They advance well beyond 22 BTDC under appropriate
circumstances (low MAPs) and, at altitude, there is much to be gained.

Absent the ignition advance, there is little to no advantage in this system,
other than (theoretically) a bit less maintenance.

In reality, I suspect that the FAA doesn't understand ignition advance (those
lovable, bungling beaurocrats) and wouldn't allow Continental to do it.
"Little to be gained" is just putting a best face on their delimna, which
will be taken at face value by most of the ignorant GA public.

Hornet Ball

Who is that masked man? :-)

Paul Lamar

Your are right about the gains from large spark advance when at very low
MAP (high altitude, typically).  My guess is that most std aircraft never
operate in this condition,  and (you're probably right again) with a need to
spend a *lot* of time and money on recertification of every single engine that
FADEC might be used on - the (rarely used) gain wasn't anywhere near the
(FAA induced) pain.  I would hazard a guess that most NA singles NEVER
go above 12,000  (don't have oxygen) - actually, I would even hazard that most
cannot attain an altitude that would bring substantial benefits from more spark
advance.  The ones that can and do go high are mostly turbo'd and therefore
do not have low MAP, ergo no large advance.  Klaus's Vari- Eze is a LOT more
efficient, and can take advantage of his extra advance.   I don't know any
certified powerplant engineers, but I doubt that they are just stupid,
probably
working on a limited budget and had to save money somewhere.  This means
lopping off the unused corners of the envelope - esp if those corners are where
the largest certification expenses lie.  Sticking to known safe max spark
advance
is much cheaper than proving to the FAA that the spark advance can't cause
detonation.

As to whether the system has advantages lacking the large spark advance,
this is a valid question.  What killed the gee-whiz Porsche system was that
even with all the "junk" and "low tech"  and "outdated" systems (typically
what unknowledgable people throw at all certified engines), the actual gains
in fuel economy were very small for skilled users, and with a less than
optimum cooling drag design (due to fan cooling) the Porsche-Mooney
was slightly slower than the Lyc-Mooney.

What is the lesson here?   For a motor operating at essentially fixed load
for very
long intervals, the capacity to instantly adjust mixture, timing, etc. is
not extremely
useful.  An intelligent user can lean to 50 deg lean of peak at <75% power
just as
well as the computer can.  A lot of pilots LIKE fiddling with the engine
controls.

The gains will be for users that don't want to be a flight engineer and want
the engine
to take care of itself.  The other possible gain is in top end life by
avaoiding
running the engine incorrectly and causing wear/damage.  The huge question is
how much are we willing to pay for this automation?  People wouldn't pay for a
Porsche-Mooney with slightly better fuel burn, much simpler and more reliable
systems (multiple backups, more than std systems) if the airplane was 5 kts
slower in cruise.  This is real, actually been done, so I really wonder how
well
the FADEC will sell as an option for a lot of money.  This is why it hasn't
been
done sooner.  The '68 VW Type 3 had electronic fuel injection, so 32 yrs later
it comes to airplanes (the second time,Porsche was first).  Be careful what you
ask for, you might get it and not like what it costs ($ and performance)

As much as they are maligned, std certified aircraft engines are pretty darned
good at their job.  This really points out how well done a rotary
installation must
be to be as good as a Lyc or Cont.  Several folks have proved it possible, which
is a *very* big thing.  Tracy Crook's system with all the elctronics is only
a single
wonderful example of what can be done by avoiding the costs of
certification, and
accepting some personal responsibility for testing and development.

Bill

PS I assume "Hornet Ball" is a 'nasal radiator'  (what my all Naval Aviator
family
normally calls it), since this is the call (if all is well) turning final
for the carrier
in an F18.

 
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