Avoiding Shock Cooling in Quick Descent

Dan, Thanks for the pointer. Even more appropriate, since we are
talking about a Turbo aircraft, is the AVWeb article.
http://www.avweb.com/cgi-bin/udt/im....ry.id=1821 07

Very interesting article. One interesting thing about it is that the
guy actually presents hard data to back up his claims (at least for his
aircraft).

-Sami

Dan Luke wrote:
"O. Sami Saydjari" wrote:

I inferred that the right thing to do might be to lower the prop speed
to a minimum and ease back power as slowly as you can. Does that

sound

about right? How quickly can one expect to pull the throttle back and
not risk shock cooling? If one must get down (say, for air traffic
control reasons, or perhaps because one is trying to take advantage of
favorable winds as long as possible), what is the best procedure.

What

about slipping it down? Does that risk the engine or the airframe at
all? I've never done slips at cruise speeds (just on approach), so
please forgive me if this is a naive question.


What is the V-le for your airplane? If it's high enough, drop the gear
and use them as speed brakes to get down while leaving some power on to
keep the engine warm. Slipping is fine.

There is considerable debate about the danger of shock cooling. Google
these groups or see http://www.avweb.com/news/columns/183094-1.html for
more discussion.

O.,

all the engine management columns by John Deakin are a must read. There
are many more at Avweb.

--
Thomas Borchert (EDDH)

Thomas,

Thanks for the pointers. The articles are indeed quite good, but there
is something I do not understand. It seems the whole theory on LOP
operation is conditioned on having GAMI injectors, because the article
implies that you can not do LOP operations on "normal" engines because
of uneven fuel distribution causes roughness due to different cylinders
outputing different powers when you start leaning past peak. Am I
missing something here? What percentage of planes actually have GAMI
injectors?

-Sami

Thomas Borchert wrote:
O.,

all the engine management columns by John Deakin are a must read. There
are many more at Avweb.

"O. Sami Saydjari" wrote:
Thanks for the pointers. The articles are indeed quite good, but there
is something I do not understand. It seems the whole theory on LOP
operation is conditioned on having GAMI injectors, because the article
implies that you can not do LOP operations on "normal" engines because
of uneven fuel distribution causes roughness due to different cylinders
outputing different powers when you start leaning past peak. Am I
missing something here? What percentage of planes actually have GAMI
injectors?

The 1997 Cessna 182S that is new to the club I am in flies LOP quite
easily. To the best of my knowledge, this is a stock engine (not GAMI
equipped). It is only advantagous to fly this way if you are flying LONG
legs. The corresponding drop in cruise airspeed is not suited to short,
fast trips.

"O. Sami Saydjari" wrote in message
...
Thomas,

Thanks for the pointers. The articles are indeed quite good, but there
is something I do not understand. It seems the whole theory on LOP
operation is conditioned on having GAMI injectors, because the article
implies that you can not do LOP operations on "normal" engines because
of uneven fuel distribution causes roughness due to different cylinders
outputing different powers when you start leaning past peak. Am I
missing something here?

No, you're not. You're seeing a good example of just how sloppy the typical
FI systems are.

What percentage of planes actually have GAMI
injectors?

GAMI has sold about 7,000 sets of their GAMIjectors, so figure that against
the entire fleet of FI engines; probably 5%. They cost less than $1000 a
set, but most pilots will spend much more for other toys, never realizing
the fuel cost savings they're missing and the damage they do to their
engines (note how many planes need a top overhaul well before TBO).

http://www.gami.com/gamijectors_order_form.html

I'll be buying an F33A in the next few weeks, and damn sure it will have
GAMI's installed before it goes anywhere.

http://www.gami.com/gamibrochure.html

(Also, I'm itching for a PRISM ignition system.)

http://www.gami.com/prism.html

HTH!!

I agree. I had GAMI's on N100DA (IO-520-B) and now TCM's (so-called)
equivalents on an IO-550 and the CHT's are way out of line.

I'm looking at getting GAMI's when the time is right.

--

Thx, {|;-)

Victor J. (Jim) Osborne, Jr.



take off my shoes to reply

Yeah, too bad they can't do something similar for carbureted engines....

"Victor J. Osborne, Jr." wrote:

I agree. I had GAMI's on N100DA (IO-520-B) and now TCM's (so-called)
equivalents on an IO-550 and the CHT's are way out of line.

I'm looking at getting GAMI's when the time is right.

--

Thx, {|;-)

Victor J. (Jim) Osborne, Jr.



take off my shoes to reply

--
--Ray Andraka, P.E.
President, the Andraka Consulting Group, Inc.
401/884-7930 Fax 401/884-7950
email
http://www.andraka.com

"They that give up essential liberty to obtain a little
temporary safety deserve neither liberty nor safety."
-Benjamin Franklin, 1759

"Victor J. Osborne, Jr." wrote in message
...
I agree. I had GAMI's on N100DA (IO-520-B) and now TCM's (so-called)
equivalents on an IO-550 and the CHT's are way out of line.

I'm looking at getting GAMI's when the time is right.


What time would that be?

Not only is the fuel use better, but there is virtually NO vibration since
the engine runs much more smoothly.

I fly a lot and with a vacation in May for a few weeks. That's the right
time.

Thx, {|;-)

Victor J. (Jim) Osborne, Jr.

"O. Sami Saydjari" wrote in news:100jq2b8dks3j44
@corp.supernews.com:

Thanks for the pointers. The articles are indeed quite good, but there
is something I do not understand. It seems the whole theory on LOP
operation is conditioned on having GAMI injectors, because the article
implies that you can not do LOP operations on "normal" engines because
of uneven fuel distribution causes roughness due to different cylinders
outputing different powers when you start leaning past peak. Am I
missing something here?

Not a lot. The article is not restricted to planes with GAMIjectors, but
it *is* relevant to engines that can operate with acceptable smoothness
LOP. That rules out most every carb'd engine (although sometimes you get
lucky), and most every big-bore TCM engine. Smaller engines and Lycoming
engines are a "sometimes can and sometimes can't" proposition.

Try it at 65% power and see what happens, especially if you have all-cyl.
monitoring. [I did once have an O-320 engine that would run absolutely
smooth all the way to idle-cutoff. Just a fluke.]



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