REFLECTOR:LOP Ops

[Jim Sower]

I need some help with some specifics on how FADEC works.
<... FADEC system meters the fuel-air mixture to ... power ... 100 degrees Rich of
peak ... cruise ... 100 degrees Lean of peak ...>

Is it safe to assume that this FADEC feature is driven by EGT sensors?

Is it further safe to assume that FADEC varies fuel delivery from one cylinder to
another according to individual EGTs (which of course are caused by uneven air
delivery through the non symmetric intake runners)?

IIRC, EGT probes tend to fail by degrees, giving increasingly erroneous readings for a
while until they quit altogether.  How does FADEC [allege?] to deal with partial
failures of EGT probe?  Total failure?

Inquiring minds need to know .... Jim S.


Scott Baker wrote:

> Many of you have read John Deakin's "Pelican's Perch" articles in Avweb.com
> regarding the subject of LOP (Lean of Peak) operations.  For those who have
> missed these excellent articles, you can find them at the following links:
> http://www.avweb.com/news/columns/182084-1.html
> http://www.avweb.com/news/columns/182131-1.html
> http://www.avweb.com/news/columns/182135-1.html
> Just to throw in some additional information ... Continental's FADEC system
> has two automatic mixture operating modes - Power and Economy.  The FADEC
> system controls the fuel injection to each cylinder.  In the Power mode, it
> meters the fuel-air mixture to obtain 100 degrees Rich of peak.  In the
> Economy mode (69% power or below), the FADEC system meters the fuel-air
> mixture to 100 degrees Lean of peak.
> Aerosance (the designers of the Teledyne-Continental FADEC system) says that
> the FADEC system does such a great job of running Continental engines Lean
> of peak, that Continental may be increasing the recommended TBO in the near
> future as a result.
> I questioned the folks at Aerosance about the machine v. human element at
> managing Lean of Peak operations.  They (perhaps with a degree of bias)
> reported that the "good" fuel-air mixture range is quite narrow when running
> Lean of Peak - meaning that a little mixture control movement (rich or lean)
> will create significant changes in EGT's ...which calls for the human to
> keep a close eye on EGT's to keep temperatures at the desired level.
> Aerosance says that humans often forget to enrich the mixture during
> descents, which may cause an overly lean situation, and which may cause the
> engine some damage if the over lean situation is ignored.  They use this
> argument to say that the FADEC, which keeps on eye on things and atomically
> adjusts mixture during all phases of flight, is the better way to go and
> avoids harmful overly lean engine situations.  Sounds like a good sales
> pitch to me.  (I liked it!)
> Duane Swing is a staunch advocate of LOP ops - especially with Lycoming
> 6-cylinder engines.
> I confess that over the years I've listened to the folks at Lycon in
> Visalia, California (who did the last overhaul on the C210 that I owned at
> the time).  Lycon preaches going no further than 100 degrees Rich of peak,
> reportedly because of the poor quality of av-fuel these days (apparently
> octane ratings change from batch to batch at the fuel pump - even though
> av-fuel is sold as 100LL - so says Lycon).  To keep the reman engine in
> warranty, I burned a LOT of gas!  I've experimented with LOP ops, but not to
> the degree that the diehards like Duane and others have.
> Scott B.
>
> ----- Original Message -----
> From: <RJohn15183@aol.com>
> To: <reflector@tvbf.org>
> Sent: Thursday, December 18, 2003 5:09 PM
> Subject: Re: REFLECTOR:Lyc injection
>
> >... I go faster AND burn less fuel AND keep my engine cooler AND keep it
> cleaner.
> >
> > I never try to talk anyone into LOP ops but the ONLY logical reason
> suporting by the data not to do it is just because you don't feel like
> dinking with it.
> >
> > Rob
>
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--
Jim Sower
Crossville, TN; Chapter 5
Long-EZ N83RT, Velocity N4095T