Engine out practice

Matt Whiting wrote in
:

Bertie the Bunyip wrote:
Matt Whiting wrote in
:

Bertie the Bunyip wrote:
Matt Whiting wrote in news:foeQi.309$2n4.18956
@news1.epix.net:

Stefan wrote:
Matt Whiting schrieb:

And Lycoming benefits if your engine lasts fewer hours.
So avoiding shock cooling actually lowers its life span? Wow.
You have no evidence that following Lycoming's recommendations
avoids the mythical shock cooling demon or that it lengthens
engine life. My experience is that the engines that are run the
hardest also last the longest. I'm basing this on everything from
chainsaws to lawnmowers
to
motorcycles to cars to trucks to off-road heavy equipment (dozers,
skidders, etc.) to airplanes (trainers, air taxi operations,
cargo).

I'm personally not convinced that Lycoming's recommendations
lengthen engine life.

Matt


Shock cooling isn't mythical. It's a fact. It's a physical law.
A physical law, eh? I've had 8 years of engineering school and
haven't seen this law. Can you provide a reference to the law of
shock cooling?
I searched for the "law of shock cooling" in Google and came up
empty...


Any component subject to heating is subject to this law. If you
take a piece of metal and heat it rapidly on one side, that side
will expand more rapidly than the other. This gradient of temp will
cause a difference in physical size one side to the other. The
elastic stress induced by this is cyclically compounded and the
resultant locked stress points that build up in the material,
particularly if it's a brittle material like cast iron, will
eventually fail, given time. The speed at which these stresses are
imposed are critical. Speed because if you introduce the heat
gradually (decrease the speed of the overall temp change), it's
given a chance to get to the other side and expand the other side
at a rate not quite so dramatically different as the side the heat
is applied to. Simple eh? The quicker you insert heat on one side
of the material, the greater the load on the opposite side and the
more likely minor damage events (cracks on a near molecular leve)
are occuring. These tiny bits of damage will become stress risers
for the next time th ematerial is loaded and the cracks will
continue to expand until a failure of the component occurs.
Yes, I'm well aware of thermal expansion and its affects. When an
engine is pulled to idle, the cylinders and heads are getting cooled
from both sides, the outside via airflow and the inside via airflow
through the engine. The far greater differential is under full
throttle during the first take-off when the engine has not yet
reached thermal equilibrium and you are heating it intensely on the
inside and cooling it on the outside.

If people wanted to talk about shock heating, then I'd be much more
willing to believe them and this fits the physics a lot better in my
opinion. Shock cooling is much less an issue from both a physics
perspective and an experience perspective.


It's the same either way. Cooling and heating are two sides of th
esame coin. It takes time to disapate heat and it's not so much the
passage of heat from one area to another (or the disappation, it's
irrelevant) but the speed at which the cooling or heating is taking
place and thus the gradient across the material.
In short, you take a frozen lump of metal and apply a torch to one
side you have a problem.
Take a cherry red pice of metal and put some ice on side and you have
the same problem (more or less, and disregading crystalisation)

It is the same if the same delta T is present, but my point is that it
is easier to heat something quickly than cool it quickly. Even at 250
C, you are only 523 degrees above absolute zero. So, this the
absolute largest delta T you can induce for cooling, and it is very
hard to get absolute zero, so you are more likely to have a cool temp
closer to 0 C yielding a delta T of only 250 degrees.

On the hot side things are more open-ended. It isn't too hard to get
450 C exhaust gas temperatures. For an engine that is started at say
20 C ambient temperature, you now have a delta T of 430 degrees which
is much greater than the 250 likely on the cooling side of the cycle.

That is one reason why I suspect that "shock heating" is more likely
to be an issue than "shock cooling." I suspect you can induce a
higher delta T during a full-throttle initial climb than you can
during an idle descent from a cruise power setting.


Right, I'm with you now. yeah, I can buy that. Froma strictly clinical
viewpoint it absolutely makes sense. My experience with damage says
otherwise, though I can offer no explanation why that should be the
case. Years ago I towed gliders with Bird-dogs and we cracked a lot of
cylinders when we just closed the throttle after release. When we moved
to gradual reduction to ultimately 1500 RPM the problem disappeared
completely. Later, when I flew big pistons,the procedures for cooling
down the cylinders on the way down. You were almost gaurunteed a crack
if you yanked the taps closed. Can't see how we went from cold to hot
any more than you would just starting up and taking off.
I've just bought an aerobatic airplane with a Lycoming. We're not
expecing to get to TBO with the engine because we'll be doing aerobaics
with it, but of course we're prepared to live with that.
I suppose the point I'm making is that even if shick cooling is over-
rated, it certainly does no harm to observe trad practices as if it did.

Bertie the Bunyip wrote:
Matt Whiting wrote in

It is the same if the same delta T is present, but my point is that it
is easier to heat something quickly than cool it quickly. Even at 250
C, you are only 523 degrees above absolute zero. So, this the
absolute largest delta T you can induce for cooling, and it is very
hard to get absolute zero, so you are more likely to have a cool temp
closer to 0 C yielding a delta T of only 250 degrees.

On the hot side things are more open-ended. It isn't too hard to get
450 C exhaust gas temperatures. For an engine that is started at say
20 C ambient temperature, you now have a delta T of 430 degrees which
is much greater than the 250 likely on the cooling side of the cycle.

That is one reason why I suspect that "shock heating" is more likely
to be an issue than "shock cooling." I suspect you can induce a
higher delta T during a full-throttle initial climb than you can
during an idle descent from a cruise power setting.


Right, I'm with you now. yeah, I can buy that. Froma strictly clinical
viewpoint it absolutely makes sense. My experience with damage says
otherwise, though I can offer no explanation why that should be the
case. Years ago I towed gliders with Bird-dogs and we cracked a lot of
cylinders when we just closed the throttle after release. When we moved
to gradual reduction to ultimately 1500 RPM the problem disappeared
completely. Later, when I flew big pistons,the procedures for cooling
down the cylinders on the way down. You were almost gaurunteed a crack
if you yanked the taps closed. Can't see how we went from cold to hot
any more than you would just starting up and taking off.
I've just bought an aerobatic airplane with a Lycoming. We're not
expecing to get to TBO with the engine because we'll be doing aerobaics
with it, but of course we're prepared to live with that.
I suppose the point I'm making is that even if shick cooling is over-
rated, it certainly does no harm to observe trad practices as if it did.

I suspect, as with most "real world" problems, that there is more in
play than delta T induced stress. Probably geometry and other factors.
Maybe having the thin fins on the outside vs. thick metal on the
inside is making a big difference in the stress profile.

I've not had experience with the larger engines or with radials.
However, my experience with O-470 and smaller engines is that shock
cooling just isn't an issue and many folks are paranoid for nothing.

Operating the engine as if shock cooling was an issue is probably not a
problem in most cases, but if it causes you, as it has with Jay, to not
practice essential emergency procedures, then I disagree that it causes
no harm. This may be very harmful should Jay experience an engine
failure for real.

Matt

Matt Whiting wrote in
:

Bertie the Bunyip wrote:
Matt Whiting wrote in

It is the same if the same delta T is present, but my point is that
it is easier to heat something quickly than cool it quickly. Even
at 250 C, you are only 523 degrees above absolute zero. So, this
the absolute largest delta T you can induce for cooling, and it is
very hard to get absolute zero, so you are more likely to have a
cool temp closer to 0 C yielding a delta T of only 250 degrees.

On the hot side things are more open-ended. It isn't too hard to
get 450 C exhaust gas temperatures. For an engine that is started
at say 20 C ambient temperature, you now have a delta T of 430
degrees which is much greater than the 250 likely on the cooling
side of the cycle.

That is one reason why I suspect that "shock heating" is more likely
to be an issue than "shock cooling." I suspect you can induce a
higher delta T during a full-throttle initial climb than you can
during an idle descent from a cruise power setting.


Right, I'm with you now. yeah, I can buy that. Froma strictly
clinical viewpoint it absolutely makes sense. My experience with
damage says otherwise, though I can offer no explanation why that
should be the case. Years ago I towed gliders with Bird-dogs and we
cracked a lot of cylinders when we just closed the throttle after
release. When we moved to gradual reduction to ultimately 1500 RPM
the problem disappeared completely. Later, when I flew big
pistons,the procedures for cooling down the cylinders on the way
down. You were almost gaurunteed a crack if you yanked the taps
closed. Can't see how we went from cold to hot any more than you
would just starting up and taking off. I've just bought an aerobatic
airplane with a Lycoming. We're not expecing to get to TBO with the
engine because we'll be doing aerobaics with it, but of course we're
prepared to live with that. I suppose the point I'm making is that
even if shick cooling is over- rated, it certainly does no harm to
observe trad practices as if it did.

I suspect, as with most "real world" problems, that there is more in
play than delta T induced stress. Probably geometry and other
factors.
Maybe having the thin fins on the outside vs. thick metal on the
inside is making a big difference in the stress profile.


I think that has more to do with the gradient along the cylinder as the
combustion chamber expands and the gasses cool. There's a lot more heat
produced up top, thus the intricate finning all over the head. In fact,
in the early days , it was improved casting techniques that alowed this
finning which in turn gave large horsepower boosts to the engines back
then. This was particulalry true in the 20s and thirties, but it still a
widely putsued goal today. the better the cooling, the more fire you can
make and the more fire..
I'll still hold to my original thoughts on it, though. I think the
difficulty in getting heat away from some parts as opposed to others
makes the temp gradient across the cylinder walls uneven in spots and
since I consider I've seen the proof of the pudding I can't shake the
habits of a lifetime as easily as al that!


I've not had experience with the larger engines or with radials.
However, my experience with O-470 and smaller engines is that shock
cooling just isn't an issue and many folks are paranoid for nothing.

I'm not paranoid about it, I just don;t think it;s a myth.

Operating the engine as if shock cooling was an issue is probably not
a problem in most cases, but if it causes you, as it has with Jay, to
not practice essential emergency procedures, then I disagree that it
causes no harm. This may be very harmful should Jay experience an
engine failure for real.



I agree and I don't subscribe to that stance in any way shape or form. I
was only picking a nit about shick cooling being a myth.
You have to do what you have to do in an airplane. You have to have some
respect for the engine, but you don;t have to go nuts!
UI mentioned earlier a place I worked did ab initio training in a J-3
(BTW, with no radios, starter or intercom) and, as you might imagine the
engine was up and down a lot.
Standard practice in airplanes like that is to chop the power on
downwind opposite the touchdown point and regualte your approach by
varying the size of your pattern from that point. Now, with some regard
towards rapid cooling we reduced to about 1200 rpm initially and then
chopped it a bit later.
Needless to say the students had very little trouble doing forced
landings when it came to that time in their training.
I've also taught just the same in Cherokees and Cessnas, although
teaching relatively recently within flying clubs I've had to go with the
flow because somewhere some asshole back in the '70s got it in his head
that since airliners do power stabilised approaches it;s a good idea in
a lightplane as well. "Makes the whole trianing experience more
professional" you know.
Now there's a new thread!


Oh, and the J-3? Last time I saw it it had over 4,000 hours on the
engine and hadn;t even had a top.
I think it;s stil flying, though hopefuly it's had a bit of work since
then. Poor old thing!


Bertie

Oh, and the J-3? Last time I saw it it had over 4,000 hours on the
engine and hadn;t even had a top.

Those things run forever. Of course, they've got no compression or
power to begin with, so you won't notice any further loss...

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

Jay Honeck wrote in news:1192454721.367225.108920
@i13g2000prf.googlegroups.com:

Oh, and the J-3? Last time I saw it it had over 4,000 hours on the
engine and hadn;t even had a top.

Those things run forever. Of course, they've got no compression or
power to begin with, so you won't notice any further loss...

;-)

There wasn't any further loss. I did the compression checks on it myself
sometimes, and they were still in the 70s then. We rented it out and we
couldn;t have done that if it wasn't sound.
the rest of the airplane, however, was a bit of a mess!
Still it held together the whole time I flew it. Mostly.

Bertie

Bertie the Bunyip wrote:
You have to do what you have to do in an airplane. You have to
have some respect for the engine, but you don;t have to go nuts!
UI mentioned earlier a place I worked did ab initio training in a J-3
(BTW, with no radios, starter or intercom) and, as you might
imagine the engine was up and down a lot. Standard practice in
airplanes like that is to chop the power on downwind opposite the
touchdown point and regualte your approach by varying the size
of your pattern from that point. Now, with some regard towards
rapid cooling we reduced to about 1200 rpm initially and then
chopped it a bit later. Needless to say the students had very little
trouble doing forced landings when it came to that time in their
training.

That's the method my CFI used.

I've also taught just the same in Cherokees and Cessnas, although
teaching relatively recently within flying clubs I've had to go with
the flow because somewhere some asshole back in the '70s got
it in his head that since airliners do power stabilised approaches
it;s a good idea in a lightplane as well. "Makes the whole trianing
experience more professional" you know.
Now there's a new thread!

I'll bite (re the new thread)...

In an accident here last year, two pilots (CFI and a student) flying an
A-36 from a local airline-pilot factory came over the fence at around
120 and bounced after their initial touchdown. The CFI finally attempted
to take control (too late) without announcing the exchange of controls
while the student applied power (presumably for a go-round). The plane
veered off the runway at high speed, across the ramp, miraculously
missed tied-down planes in the first couple of rows and then slammed
into a V-tail Bo tied-down on the ramp, completely cutting it up w/the
prop, ripping the chains out of the ground, pushing it into the middle
of the rows, and destroying it. The two pilots were shaken but fine, and
the A-36 had substantial damage but nothing like the V-tail.

After the accident, their excessive over-the-fence speed was discussed,
and it was said that the school does not teach airspeeds during
approaches -- since the students are largely airline-bound individuals,
they teach "descent-rate". Much discussion ensued in the following weeks
about teaching the proper approach *for the airplane you're in at the
time* vs teaching airliner approaches in small, single-engine aircraft.

Your comment caused me to do some Googling. This had some in interesting
stats for a limited accident database.

archive.aya.org/safety/levyhibbler200207.pdf

On Oct 15, 6:20 am, Bertie the Bunyip wrote:

Standard practice in airplanes like that is to chop the power on
downwind opposite the touchdown point and regualte your approach by
varying the size of your pattern from that point. Now, with some regard
towards rapid cooling we reduced to about 1200 rpm initially and then
chopped it a bit later.
Needless to say the students had very little trouble doing forced
landings when it came to that time in their training.
I've also taught just the same in Cherokees and Cessnas, although
teaching relatively recently within flying clubs I've had to go with the
flow because somewhere some asshole back in the '70s got it in his head
that since airliners do power stabilised approaches it;s a good idea in
a lightplane as well. "Makes the whole trianing experience more
professional" you know.
Now there's a new thread!

That's what I was taught in the early '70s when I got my PPL.
When I went for the CPL in the '90s the whole syllabus had changed,
and so had the forced-approach proficiencies of the students and PPLs.
In the instructor refresher courses the forced approach comes up as
the most frequently failed item on both private and commercial flight
tests. The students simply don't know how to adjust glidepath using
nothing more than airspeed, with a slip thrown in if necessary. They
don't get the idea that they can glide farther if they drop the nose
and maintain best glide, drop it farther and go faster if they're
bucking a headwind, pull the nose up and sink if they're high, or get
into ground effect and skim along to the touchdown point if they're a
little short. If no fences are in the way, of course. I once did that
on an instructor checkride and the examiner told me that this was
acceptable. Your mileage may vary.

As far as the preoiler, I made no drawings. I was always an
eyeball engineer, with a basic preliminary sketch if necessary. I made
my living designing, building, rebuilding and inventing stuff for 12
years and this comes easily enough. Maybe, when I get back from a trip
to Africa for the next three weeks, I'll draw something up and submit
it.

Dan

Bertie:
Oh, and the J-3? Last time I saw it it had over 4,000 hours on the
engine and hadn;t even had a top.

Jay:
Those things run forever. Of course, they've got no compression or
power to begin with, so you won't notice any further loss...

;-)

Bertie:
There wasn't any further loss. I did the compression checks on it myself
sometimes, and they were still in the 70s then. We rented it out and we
couldn;t have done that if it wasn't sound.
the rest of the airplane, however, was a bit of a mess!
Still it held together the whole time I flew it. Mostly.

How does that work with regard to the 100-hr and annual inspections for
a rental aircraft? When I worked at the flight school, our mechanics
said you can run an engine past TBO, but they won't sign off an annual
or 100-hr beyond the manufacturer's published TBO. Is signing it off
after TBO not a direct violation of mechanic regs but just a matter of
finding a mechanic willing to take the risk (ours wouldn't do it)?

Shirl wrote in news:Xmnushal8y-
:


I'll bite (re the new thread)...

In an accident here last year, two pilots (CFI and a student) flying
an
A-36 from a local airline-pilot factory came over the fence at around
120 and bounced after their initial touchdown. The CFI finally
attempted
to take control (too late) without announcing the exchange of controls
while the student applied power (presumably for a go-round). The plane
veered off the runway at high speed, across the ramp, miraculously
missed tied-down planes in the first couple of rows and then slammed
into a V-tail Bo tied-down on the ramp, completely cutting it up w/the
prop, ripping the chains out of the ground, pushing it into the middle
of the rows, and destroying it. The two pilots were shaken but fine,
and
the A-36 had substantial damage but nothing like the V-tail.

After the accident, their excessive over-the-fence speed was
discussed,
and it was said that the school does not teach airspeeds during
approaches -- since the students are largely airline-bound
individuals,
they teach "descent-rate". Much discussion ensued in the following
weeks
about teaching the proper approach *for the airplane you're in at the
time* vs teaching airliner approaches in small, single-engine
aircraft.

Your comment caused me to do some Googling. This had some in
interesting
stats for a limited accident database.

archive.aya.org/safety/levyhibbler200207.pdf


Thank you!
And kudos to your instructor.

This is exactly the sort of crap I'm talking about. I fly lightplanes
and I also fly jets. I've flown five of your more poplualr sorts of jets
weighing anything up to 350,000 lbs.
they fly just like airplanes. The only tow things that are even half
true are the neccesisty for stabilised approaches, and even then you can
fudge it a bit, and the "kck it straight n a crosswind " thing. Which is
only the case for some airplanes and even then is widely misunderstood.
In the former instance, the main reason we get stabilised is because in
big swept wing airplanes, it can be hard to control the speed and rate
of descent fo ra couple of reasons. One, the swept wing has a very flat
drag curve, and two, the engines are sometimes slow to spool up (not so
much wiht newer engines) however, you can still do practice deadstick
landings all day in them if you want. They will do them, no problem. We
don't, though. however, n a light single, I think it's a very good idea
to at least keep it on the high side if nothing else and even better,
leave the final a deadstick every time. And yes, I've fown Bonanzas,
Commanches, all sorts. They are all better off doing approaches like
this, at least once you pass below the altitude where all other options
are closed off to you.
Even in light twins, guys tend to drag them in over the fence if the
field is anyways short. Completely unneccesary and very poor technique..

The "they don't put a wing down in a crosswind" thing is complete crap.
There are several jets you have to land wings level (and th ercoupe, of
course, shudder! ) and they are most of th efour engine thingies, the
727 and DC-9/MD80s
( very low wing and outboard flaps) and a couple of other for various
ground contact reasons.
However, corrct technique for this entails crossing the controls as you
would as if you had just done a slip to touchdown and maintaining it
though the landing roll. It feels awful when you do it first, but you
get the hang of it. If you land some of the long ones, like the 727 in a
max crosswind and the runway is narrow, you are acually out over the
edge of the runway as you touch down! You have to squeeze the nose
straight while it is still in the air whilst adding oppistie aileron.
Feels funny but works.
Everything else I've flown lands much better with a wing down and the
fuselage tracking straight down the runway. No question about it. In
fact the autoplit will cross the controls from about 300 feet down when
you're autolanding in most of them nowadays.


End rant.

Shirl wrote in
:

Bertie:
Oh, and the J-3? Last time I saw it it had over 4,000 hours on the
engine and hadn;t even had a top.

Jay:
Those things run forever. Of course, they've got no compression or
power to begin with, so you won't notice any further loss...

;-)

Bertie:
There wasn't any further loss. I did the compression checks on it
myself sometimes, and they were still in the 70s then. We rented it
out and we couldn;t have done that if it wasn't sound.
the rest of the airplane, however, was a bit of a mess!
Still it held together the whole time I flew it. Mostly.

How does that work with regard to the 100-hr and annual inspections
for a rental aircraft? When I worked at the flight school, our
mechanics said you can run an engine past TBO, but they won't sign off
an annual or 100-hr beyond the manufacturer's published TBO. Is
signing it off after TBO not a direct violation of mechanic regs but
just a matter of finding a mechanic willing to take the risk (ours
wouldn't do it)?



Dunno nowadays. but then it was legal. I think it probably still is.
Our operation, though commercial, was part 91 and I'm not aware of any
changes in that rule.
Nowadays I'm only ever involved with club activity and that strictly on
condition. I'd tear down an antique engine every now and again myself,
though.They're too valuable to put a leg out of bed on.

Someone here will know for sure, though.

Interestingly, if you wanted to goto the boundaries of what's legal
commercailly, and someone will certainly correct me if I'm wrong, but
you could still buy an old OX-5, get a set of drawings and a dataplate
for something like a Waco9 or Alexander Eaglerock, build it, certify it
and then operate it out of a cow pasture with your commercial licence,
all legally. #

Oh yeah, no radio.

And why not?
If the operator knew what he was doing why not indeed?

Mind you , I'd get the OX-5 millerised first.


Bertie