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Cooling before shutdown

 
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dischenko(at)gmail.com
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PostPosted: Mon May 28, 2007 6:49 am    Post subject: Cooling before shutdown Reply with quote
Hi All

I suspect this has been discussed here before, but I can't find it in the archive...

What is the danger of shutting down the engine before it cools to 150C? The book says it is allowed to shut down not above 170C, but then such occasions should be noted in the logbook. I have only a limited experience with my M14P, but it seems that if the ambient temperature is over 20C (68F) it takes ages to cool the engine to 160C, let alone 150C. Reaching 170C though takes only a few minutes, so I am wondering if this can be done routinely without damaging the engine. Or, put another way, what's worse -- shutting down too hot or running on idle for 10 minutes?

Also, in Lithuania my instructor showed me an unwritten trick they used in the Soviet air force in such occasions -- squirting one primer of gas into the cylinders while simultaneously pulling the throttle to idle and killing the mags; this would supposedly provide extra cooling to the cylinders (but of course this was not noticeable on the CHT gauge). Wondering if other people are using this technique...

Thanks in advance for any comments!

Denis
Yak-18T
London, England
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martin(at)buzzardaviation
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PostPosted: Mon May 28, 2007 12:33 pm    Post subject: Cooling before shutdown Reply with quote
At 15:47 28/05/2007, Denis Ischenko wrote:
Quote:
Hi All

What is the danger of shutting down the engine before it cools to
150C? The book says it is allowed to shut down not above 170C, but
then such occasions should be noted in the logbook. I have only a
limited experience with my M14P, but it seems that if the ambient
temperature is over 20C (68F) it takes ages to cool the engine to
160C, let alone 150C. Reaching 170C though takes only a few minutes,
so I am wondering if this can be done routinely without damaging the
engine. Or, put another way, what's worse -- shutting down too hot
or running on idle for 10 minutes?

I find I rarely get that hot (I believe the spinner on my 18T aids
cooling) but if I am running hot (above 170) usually after some
energetic maneuvering, then I just loiter near the circuit for five
minutes at 59% and she soon cools down. I also make a point of not
using the brakes unless necessary on landing as a slow taxi back to
the tie downs allows things to cool and stabilize. No point wearing
out brakes only to sit there parked waiting for things to cool off.

Quote:
Also, in Lithuania my instructor showed me an unwritten trick they
used in the Soviet air force in such occasions -- squirting one
primer of gas into the cylinders while simultaneously pulling the
throttle to idle and killing the mags; this would supposedly provide
extra cooling to the cylinders (but of course this was not
noticeable on the CHT gauge). Wondering if other people are using
this technique...

Not heard of that one. Where are you based Dennis? WW? I'm at EGHU

Happy Landings
____|____
\O/
o'o Martin Robinson

Yak 18T HA-YAV

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dischenko(at)gmail.com
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PostPosted: Mon May 28, 2007 2:24 pm    Post subject: Cooling before shutdown Reply with quote
Martin

Thanks for you comment, it made me think and look in the manual again. I am trying to keep CHT at above 170 on final for the fear of shock-cooling and not having power available quickly for a go-around. The book prescribes 160-180 during descent, but the same book says 140 is the minimum for prolonged operation, so may be I am running it too hot... What temperatures do other people keep on final?

I agree of course about the use of brakes after landing, but I have to taxi on some rough up-sloping grass bits to get to my spot (at Elstree -- EGTR), so can't keep it at idle...

Denis
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aerobaticgirl(at)yahoo.co
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PostPosted: Mon May 28, 2007 5:26 pm    Post subject: Cooling before shutdown Reply with quote
My book says don't shut down above 140 degrees.

I must be babying my engine because if it gets to 170 degrees, I start to shallow my climb so I don't overtemp and pull back throttle/prop. I try to run it for acro no higher than 160-170 and cooler than that when coming in for landing so I can shut down below 140.

I use a minimun of 120 for run up and takeoff settings.

Smash

Denis Ischenko <dischenko(at)gmail.com> wrote:
[quote]Martin

Thanks for you comment, it made me think and look in the manual again. I am trying to keep CHT at above 170 on final for the fear of shock-cooling and not having power available quickly for a go-around. The book prescribes 160-180 during descent, but the same book says 140 is the minimum for prolonged Luggage? GPS? Comic books?
Check out fitting [url=http://us.rd.yahoo.com/evt=48249/*http://search.yahoo.com/search?fr=oni_on_mail&p=graduation+gifts&cs=bz] gifts for grads[/url] at Yahoo! Search. [quote][b]

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martin(at)buzzardaviation
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PostPosted: Tue May 29, 2007 1:24 am    Post subject: Cooling before shutdown Reply with quote
At 23:21 28/05/2007, Denis Ischenko wrote:
Quote:
Martin

Thanks for you comment, it made me think and look in the manual
again. I am trying to keep CHT at above 170 on final for the fear of
shock-cooling and not having power available quickly for a
go-around. The book prescribes 160-180 during descent, but the same
book says 140 is the minimum for prolonged operation, so may be I am
running it too hot... What temperatures do other people keep on final?

Denis,

I usually try to get temps down to around 150 for the circuit and
landing. I haven't seen the 170 on final in any of my manuals and she
runs really well doing what we've been doing. Fancy meeting up at
Elstree one day? I need to connect with Harry Winter who I think is
instructing there and also meet with Tim Debois (at) Flight Logistics re
filming work.

Cheers

M
Happy Landings
____|____
\O/
o'o Martin Robinson

Yak 18T HA-YAV

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