A aviation & planes forum. AviationBanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » AviationBanter forum » rec.aviation newsgroups » Owning
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Avoiding Shock Cooling in Quick Descent



 
 
Thread Tools Display Modes
  #1  
Old January 7th 04, 07:03 AM
O. Sami Saydjari
external usenet poster
 
Posts: n/a
Default Avoiding Shock Cooling in Quick Descent

My engine operating manual (for my Piper Turbo Arrow III) strongly
discourages pulling the power back and doing a quick descent -- it warns
of engine-killing shock cooling. Sounds reasonable to me...but it (and
my airplane manual) does not really seem to say how best to do a fast
descent when you have to.

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.

-Sami
N2057M
Piper Turbo Arrow III

  #2  
Old January 7th 04, 09:30 AM
Jeff
external usenet poster
 
Posts: n/a
Default

I read an article that said that if you dont go below 20' MP pressure you
should be ok.
Personally, I reduce power enough where I can do a 500 fpm decent and stay
under the yellow, usually this puts me at about 140 kts IAS, but only if its
smooth air, if I need to stay below Va or if they are trying to slam dunk me
then I drop the landing gear, that and about 25' MP and 2300 rom will give
you around a 800 fpm decent, sometimes faster if you let it. But I try my
best to only do 500 fpm decents.

I was taught to pull power off at about 1' MP per minute.

BTW how is that new T-arrow of yours doing.

"O. Sami Saydjari" wrote:

My engine operating manual (for my Piper Turbo Arrow III) strongly
discourages pulling the power back and doing a quick descent -- it warns
of engine-killing shock cooling. Sounds reasonable to me...but it (and
my airplane manual) does not really seem to say how best to do a fast
descent when you have to.

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.

-Sami
N2057M
Piper Turbo Arrow III


  #3  
Old January 8th 04, 01:51 AM
O. Sami Saydjari
external usenet poster
 
Posts: n/a
Default




BTW how is that new T-arrow of yours doing.


Still undergoing an avionics upgrade (Garmin 430, GDL 49 weather uplink,
and GTX 330 transponder with TIS....pretty cool). Will be ready Friday
(I can't wait!!!). Flying it home 12 January (Reno to Central
Wisconsin)...Wish for good weather! If I end up taking a southerly
route, I will wave as I pass overhead

-Sami
N2057M

  #4  
Old January 8th 04, 03:10 AM
Jeff
external usenet poster
 
Posts: n/a
Default

one other thing, dont lean the engine on take off or during climb.
Wait untill your at your cruise altitude to do any leaning.
and make sure you get the new power settings, the book settings no longer
apply since that intercooler was installed. If you fly it at book settings,
you will be running at a higher power setting and will burn up cylinders.


"O. Sami Saydjari" wrote:


BTW how is that new T-arrow of yours doing.


Still undergoing an avionics upgrade (Garmin 430, GDL 49 weather uplink,
and GTX 330 transponder with TIS....pretty cool). Will be ready Friday
(I can't wait!!!). Flying it home 12 January (Reno to Central
Wisconsin)...Wish for good weather! If I end up taking a southerly
route, I will wave as I pass overhead

-Sami
N2057M


  #5  
Old January 8th 04, 05:47 AM
Mike Rapoport
external usenet poster
 
Posts: n/a
Default

Is it at Aviation Classics?

Mike
MU-2


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



BTW how is that new T-arrow of yours doing.


Still undergoing an avionics upgrade (Garmin 430, GDL 49 weather uplink,
and GTX 330 transponder with TIS....pretty cool). Will be ready Friday
(I can't wait!!!). Flying it home 12 January (Reno to Central
Wisconsin)...Wish for good weather! If I end up taking a southerly
route, I will wave as I pass overhead

-Sami
N2057M



  #6  
Old January 8th 04, 07:28 AM
O. Sami Saydjari
external usenet poster
 
Posts: n/a
Default

Yes, as a matter of fact it is. Do you want to stop by and check on it
for me? Just don't bug them...its a big job and they are trying to
get it done by Thursday night so they can do a certifying flight on
Friday

-Sami

Mike Rapoport wrote:
Is it at Aviation Classics?

Mike
MU-2


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


BTW how is that new T-arrow of yours doing.


Still undergoing an avionics upgrade (Garmin 430, GDL 49 weather uplink,
and GTX 330 transponder with TIS....pretty cool). Will be ready Friday
(I can't wait!!!). Flying it home 12 January (Reno to Central
Wisconsin)...Wish for good weather! If I end up taking a southerly
route, I will wave as I pass overhead

-Sami
N2057M





  #7  
Old January 7th 04, 01:24 PM
Dan Luke
external usenet poster
 
Posts: n/a
Default

"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.
--
Dan
C172RG at BFM
(remove pants to reply by email)


  #8  
Old January 7th 04, 11:43 PM
O. Sami Saydjari
external usenet poster
 
Posts: n/a
Default

VLE is 129 KIAS...Cruise is around 140-150 KIAS. To avoid stess, I
would probably not drop gear until I was about 115 KIAS. Still, it is a
good suggestion once I slow to that speed. Thanks.

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.


  #9  
Old January 8th 04, 03:17 AM
Jeff
external usenet poster
 
Posts: n/a
Default

if you wait till you slow down to 115 to drop the gear, you better start way
way the heck out, its hard to get it slowed down that much with the gear up.
Especially if your up high.

If your to fast, the gear wont come down, your red unsafe light will come on.

once I hit 129 kts I pop the gear .. then you turn into a rock.

"O. Sami Saydjari" wrote:

VLE is 129 KIAS...Cruise is around 140-150 KIAS. To avoid stess, I
would probably not drop gear until I was about 115 KIAS. Still, it is a
good suggestion once I slow to that speed. Thanks.

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.


  #10  
Old January 8th 04, 03:56 AM
O. Sami Saydjari
external usenet poster
 
Posts: n/a
Default

I read somewhere recently that making a habit of doing things like
dropping gear and flaps right at the edge of the allowed speed puts too
much stress on them...so I was trying to be conservative. Since this is
probably not a typical maneuver, I guess it makes sense to drop it right
at 129.

-Sami

Jeff wrote:
if you wait till you slow down to 115 to drop the gear, you better start way
way the heck out, its hard to get it slowed down that much with the gear up.
Especially if your up high.

If your to fast, the gear wont come down, your red unsafe light will come on.

once I hit 129 kts I pop the gear .. then you turn into a rock.

"O. Sami Saydjari" wrote:


VLE is 129 KIAS...Cruise is around 140-150 KIAS. To avoid stess, I
would probably not drop gear until I was about 115 KIAS. Still, it is a
good suggestion once I slow to that speed. Thanks.

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.




 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT +1. The time now is 07:41 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 AviationBanter.
The comments are property of their posters.