Avoiding Shock Cooling in Quick Descent

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.

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.

once the gear comes down, your going to slow down in a few seconds. your also going
to start decending so you need to trim the airplane to how fast your wanting to
decend. If you have taken to much power off to slow down to gear speed then you
will need to be ready to add power once it comes down also.

You will get the hang of it after a few times.
BTW I also keep the auto extend off, most people I have talked to if theirs hasnt
been disabled, put it on manual so you can get the gear up at a slower speed on
take off and it dont fall out if you slow down to much. You will want to ask if
your auto extend has been disabled or if it still works, There is a service
bulletin on it I think.


"O. Sami Saydjari" wrote:

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.