Engine out practice

As previously noted (in the thread about Paul's wife getting scared),
Mary and I had virtually stopped doing this kind of flying for fear of
harming our (very expensive) engine. A lively debate ensued as to
whether or not repeated high-to-low-to-high power applications would
wear out your engine any faster than would normal operations.

I eventually agreed that gradual power changes would not unduly harm
an air-cooled engine, and vowed that I would endeavor to practice this
most-important skill on our next flight. And we did.

We were on a flight back from Galesburg, IL when I started the
procedure, and very gradually began a power reduction whilst in cruise
flight at 3500 feet. I took a full minute to reduce the power to
idle, watching our (newly reinstalled) JPI EDM-700 engine analyzer for
signs of stress.

As RPMs dropped below 1000, the "shock-cooling alarm" suddenly went
off, flashing its dire warnings that EGTs had dropped beyond (and
faster) than recommended limits. (I can't remember what the threshold
is for that alarm -- it's preset.)

This despite my most careful power reduction, which (obviously) wasn't
slow enough.

Since the damage (so to speak) had already been done, I continued the
descent toward an Illinois corn field. With the harvest under way, I
had my choice of:

- Freshly harvested corn stubble, not plowed
- Freshly harvested crops, plowed dirt
- Unharvested corn or winter wheat

I opted for the corn stubble, as the stalks would hold the soil
together firmly and not present as much "flip force" to the landing
gear as the plowed or unharvested field. I took it down to 200 AGL
before applying power and heading home, satisfied that we would have
survived and giving the farmer a nice show.

For you aircraft owners who do this regularly, how slowly do you
retard the throttle to prevent shock cooling? (I know -- does shock
cooling really exist? For purposes of this discussion, I'll pretend
that it does.)

Given that the power reduction must be incredibly gradual, do you feel
that this exercise is realistic? There really is no chance to
simulate how you must "suddenly" find best glide speed (after your
engine has presumably just crapped out), since you're gradually
reducing your speed along with your power. Or do you put the plane
into a shallow dive as you reduce power, so as not to lose airspeed?

It's funny -- as renters we practiced this all the time. Now, after 9
years of ownership, we haven't practiced it in ages -- and didn't even
realize this lack until Shirl's comments in Paul's thread. Another
good thing about "belonging" to this newsgroup...

Thoughts?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

"Jay Honeck" wrote:

As RPMs dropped below 1000, the "shock-cooling alarm" suddenly went
off, flashing its dire warnings that EGTs had dropped beyond (and
faster) than recommended limits. (I can't remember what the threshold
is for that alarm -- it's preset.)

EGTs don't matter. Sure you don't mean CHTs? What temps. were you seeing?

IIRC, you can modify alarm limits. Check the manual.

This despite my most careful power reduction, which (obviously) wasn't
slow enough.

Does the bird have cowl flaps?


--
Dan
T-182T at BFM

"Jay Honeck" wrote in message
ups.com...
...
As RPMs dropped below 1000, the "shock-cooling alarm" suddenly went
off, flashing its dire warnings that EGTs had dropped beyond (and
faster) than recommended limits. (I can't remember what the threshold
is for that alarm -- it's preset.)
...
Jay Honeck

What happens when you do a normal pattern? Given your explaination, I would
assume that you get a shock cooling alarm everytime you do power reductions
as part of a normal landing. If not, use the same technique at altitude to
get into a power idle glide.

I don't have any engine analyzer. But, on a normal approach, I will reduce
throttle in two or three steps to get to 15" or 16". That supports my
minimum, flaps up, holding altitude speed. Then, with gear out and flaps
down, I'm descending on extended downwind, base and final, with the power
gradually coming off to flare. (I'm not describing this as the ideal
technique. I'm stating it so that others can say - "Are you crazy! That
technique is an engine killer.")

Engine out practice for me is very similar. From cruise, reduce throttle in
a couple of steps to 15". Maintain altitude. Then gradually pull off power
pitching over to maintain best glide. You're right, it's all very methodical
and does not present a sudden engine loss scenario. Maybe only do that once
or twice a year. For me, the engine out practice is all about picking the
spot and making it without power. Practicing that without instaneous loss of
engine power still has a lot of value.

Now, in my Lake, I've got other concerns. Several times a year and during
every annual insurance checkride, a sudden loss of engine power on takeoff
is a required demonstrated skill. With a top-mounted, pusher engine, in a
takeoff configuration, close to the ground, sudden engine loss and anything
but immediate response is deadly. The sudden loss of nose down thrust will
cause pitch up at a speed already close to stall with not much altitude to
recover. An immediate (and I mean immediate) push over is absolutely
critical. Critical enough that practice is necessary regardless of any harm
it might be doing to the engine.

So, for me, the engine-out on takeoff gets me practice responding quickly.
The more gradual throttle to idle and then a practice off-field approach
completes the scenario.

-------------------------------
Travis
Lake N3094P
PWK

Hey, if you're worried, go rent a plane that will glide in a similar
manner, and take a good instructor too.

john

Jay Honeck wrote:
As previously noted (in the thread about Paul's wife getting scared),
Mary and I had virtually stopped doing this kind of flying for fear of
harming our (very expensive) engine. A lively debate ensued as to
whether or not repeated high-to-low-to-high power applications would
wear out your engine any faster than would normal operations.

I eventually agreed that gradual power changes would not unduly harm
an air-cooled engine, and vowed that I would endeavor to practice this
most-important skill on our next flight. And we did.

We were on a flight back from Galesburg, IL when I started the
procedure, and very gradually began a power reduction whilst in cruise
flight at 3500 feet. I took a full minute to reduce the power to
idle, watching our (newly reinstalled) JPI EDM-700 engine analyzer for
signs of stress.

As RPMs dropped below 1000, the "shock-cooling alarm" suddenly went
off, flashing its dire warnings that EGTs had dropped beyond (and
faster) than recommended limits. (I can't remember what the threshold
is for that alarm -- it's preset.)

This despite my most careful power reduction, which (obviously) wasn't
slow enough.

Since the damage (so to speak) had already been done, I continued the
descent toward an Illinois corn field. With the harvest under way, I
had my choice of:

- Freshly harvested corn stubble, not plowed
- Freshly harvested crops, plowed dirt
- Unharvested corn or winter wheat

I opted for the corn stubble, as the stalks would hold the soil
together firmly and not present as much "flip force" to the landing
gear as the plowed or unharvested field. I took it down to 200 AGL
before applying power and heading home, satisfied that we would have
survived and giving the farmer a nice show.

For you aircraft owners who do this regularly, how slowly do you
retard the throttle to prevent shock cooling? (I know -- does shock
cooling really exist? For purposes of this discussion, I'll pretend
that it does.)

Given that the power reduction must be incredibly gradual, do you feel
that this exercise is realistic? There really is no chance to
simulate how you must "suddenly" find best glide speed (after your
engine has presumably just crapped out), since you're gradually
reducing your speed along with your power. Or do you put the plane
into a shallow dive as you reduce power, so as not to lose airspeed?

It's funny -- as renters we practiced this all the time. Now, after 9
years of ownership, we haven't practiced it in ages -- and didn't even
realize this lack until Shirl's comments in Paul's thread. Another
good thing about "belonging" to this newsgroup...

Thoughts?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Jay Honeck wrote:
As previously noted (in the thread about Paul's wife getting scared),
Mary and I had virtually stopped doing this kind of flying for fear of
harming our (very expensive) engine. A lively debate ensued as to
whether or not repeated high-to-low-to-high power applications would
wear out your engine any faster than would normal operations.

I eventually agreed that gradual power changes would not unduly harm
an air-cooled engine, and vowed that I would endeavor to practice this
most-important skill on our next flight. And we did.

We were on a flight back from Galesburg, IL when I started the
procedure, and very gradually began a power reduction whilst in cruise
flight at 3500 feet. I took a full minute to reduce the power to
idle, watching our (newly reinstalled) JPI EDM-700 engine analyzer for
signs of stress.

As RPMs dropped below 1000, the "shock-cooling alarm" suddenly went
off, flashing its dire warnings that EGTs had dropped beyond (and
faster) than recommended limits. (I can't remember what the threshold
is for that alarm -- it's preset.)

When I practiced in my Skylane and also in the club Arrow, I retarded
the throttle smoothly in probably 2-3 seconds. I didn't worry about
shock cooling and never saw any signs of distress in either the O-470 or
the O-360.

The issue with shock cooling isn't the rate of cooling per se, but
rather stress induced by differential cooling. Most engines see far
higher temperature differentials during start-up than they do during
cooldown. Jay, have you timed your engine heat up rate? It would be
interesting to watch how fast your engine heats up from say a 50 degree
cold start and then compare that to the cool-down rate when you pull the
throttle for engine out practice. I'm assuming this would be fairly
trivial with your engine analyzer.

I'm not sure what your normal operating temps are, but I assume it is a
much larger delta between ambient and your normal operating temps than
between your normal operating temps and the temps you see during a glide
at idle. I also suspect that the rate of heat-up during take-off is at
least as high as the rate of cooling during an idle glide. However, it
would be very interesting to see the data if you are inclined to collect
it some day.

Matt

Travis Marlatte wrote:
"Jay Honeck" wrote in message
ups.com...
...
As RPMs dropped below 1000, the "shock-cooling alarm" suddenly went
off, flashing its dire warnings that EGTs had dropped beyond (and
faster) than recommended limits. (I can't remember what the threshold
is for that alarm -- it's preset.)
...
Jay Honeck

What happens when you do a normal pattern? Given your explaination, I would
assume that you get a shock cooling alarm everytime you do power reductions
as part of a normal landing. If not, use the same technique at altitude to
get into a power idle glide.

I don't have any engine analyzer. But, on a normal approach, I will reduce
throttle in two or three steps to get to 15" or 16". That supports my
minimum, flaps up, holding altitude speed. Then, with gear out and flaps
down, I'm descending on extended downwind, base and final, with the power
gradually coming off to flare. (I'm not describing this as the ideal
technique. I'm stating it so that others can say - "Are you crazy! That
technique is an engine killer.")

Have you killed any engines yet doing this?

Matt

On 2007-10-13 06:57:56 -0700, Jay Honeck said:

As previously noted (in the thread about Paul's wife getting scared),
Mary and I had virtually stopped doing this kind of flying for fear of
harming our (very expensive) engine. A lively debate ensued as to
whether or not repeated high-to-low-to-high power applications would
wear out your engine any faster than would normal operations.

Most flight schools practice engine out emergencies frequently, even on
high performance aircraft. The engines typically make it to TBO.

The things that seem to shorten engine life have little to do with
shock cooling. The biggest factor seems to be how much the engine is
used.

If the engine is flown in accordance with the manual, you should not
have any problems with shock cooling.



--
Waddling Eagle
World Famous Flight Instructor

The issue with shock cooling isn't the rate of cooling per se, but
rather stress induced by differential cooling.

Actually, I think it is the rate of cooling *and* the differential
cooling -- if it exists at all. Like you, I am skeptical -- but am I
willing to bet $25K on it? Nope.

Therefore, I fly as if it exists.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

EGTs don't matter. Sure you don't mean CHTs? What temps. were you seeing?

Whoops. Right you are.

IIRC, you can modify alarm limits. Check the manual.

Roger that.

This despite my most careful power reduction, which (obviously) wasn't
slow enough.

Does the bird have cowl flaps?

Nope.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

On Oct 13, 8:57 am, Jay Honeck wrote:
As previously noted (in the thread about Paul's wife getting scared),
Mary and I had virtually stopped doing this kind of flying for fear of
harming our (very expensive) engine. A lively debate ensued as to
whether or not repeated high-to-low-to-high power applications would
wear out your engine any faster than would normal operations.

I eventually agreed that gradual power changes would not unduly harm
an air-cooled engine, and vowed that I would endeavor to practice this
most-important skill on our next flight. And we did.

We were on a flight back from Galesburg, IL when I started the
procedure, and very gradually began a power reduction whilst in cruise
flight at 3500 feet. I took a full minute to reduce the power to
idle, watching our (newly reinstalled) JPI EDM-700 engine analyzer for
signs of stress.

As RPMs dropped below 1000, the "shock-cooling alarm" suddenly went
off, flashing its dire warnings that EGTs had dropped beyond (and
faster) than recommended limits. (I can't remember what the threshold
is for that alarm -- it's preset.)

This despite my most careful power reduction, which (obviously) wasn't
slow enough.

Since the damage (so to speak) had already been done, I continued the
descent toward an Illinois corn field. With the harvest under way, I
had my choice of:

- Freshly harvested corn stubble, not plowed
- Freshly harvested crops, plowed dirt
- Unharvested corn or winter wheat

I opted for the corn stubble, as the stalks would hold the soil
together firmly and not present as much "flip force" to the landing
gear as the plowed or unharvested field. I took it down to 200 AGL
before applying power and heading home, satisfied that we would have
survived and giving the farmer a nice show.

For you aircraft owners who do this regularly, how slowly do you
retard the throttle to prevent shock cooling? (I know -- does shock
cooling really exist? For purposes of this discussion, I'll pretend
that it does.)

Given that the power reduction must be incredibly gradual, do you feel
that this exercise is realistic? There really is no chance to
simulate how you must "suddenly" find best glide speed (after your
engine has presumably just crapped out), since you're gradually
reducing your speed along with your power. Or do you put the plane
into a shallow dive as you reduce power, so as not to lose airspeed?

It's funny -- as renters we practiced this all the time. Now, after 9
years of ownership, we haven't practiced it in ages -- and didn't even
realize this lack until Shirl's comments in Paul's thread. Another
good thing about "belonging" to this newsgroup...

Thoughts?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993www.AlexisParkInn.com
"Your Aviation Destination"

I'm not an expert, but it seems to me that the important thing is to
reduce airspeed immediately when reducing power. It's the wind
whistling through an idling engine at 140 knots that's going to do
some serious shock cooling.
--
Gene Seibel
Tales of Flight - http://pad39a.com/gene/tales.html
Because I fly, I envy no one.