Prop to High RPM on downwind

I can't find it right now, but Lycoming had a publication in which they
advised against going to low prop pitch for deceleration of the airplane.
They said it caused detuning of the dynamic counterweights on the crankshaft
("harmonic balancers"?) and was the demonstrated cause of damage to certain
of their engine models. Although my engine was not listed in the affected
models, it seems that the same principle applies, and I have avoided going
to the high RPM setting until power is reduced on final, for engine
protection as well as noise. Supplement your printed checklist with GUMP
checks, including one on short final ALWAYS.

Stan

"Mitty" wrote in message
...
I've been taught to set the prop to high RPM on final, but I don't like
this very much because then, when I run my checklist for the first time on
downwind, I have to leave one item "open."

So what's wrong with doing it on downwind? (This in a Cherokee 6 or and
Arrow) It seems to work fine, does not disarrange the engine, etc. I
suppose there is some small noise increase, but hardly much.

So (1) is everyone taught to do it on final? (2) Why? (3) What's wrong
with doing it on downwind?

TIA

On Sun, 21 Nov 2004 23:51:25 GMT, Mitty wrote:

I've been taught to set the prop to high RPM on final, but I don't like this
very much because then, when I run my checklist for the first time on downwind,
I have to leave one item "open."

So what's wrong with doing it on downwind? (This in a Cherokee 6 or and Arrow)
It seems to work fine, does not disarrange the engine, etc. I suppose there
is some small noise increase, but hardly much.

So (1) is everyone taught to do it on final? (2) Why? (3) What's wrong with
doing it on downwind?

TIA


Full forward (high RPM) is in case of a go around. Going high pitch
mid-field will create a really loud racket on the ground. Waiting
until short final is too late in my opinion since we're human and can
forget things. To avoid this I go full forward (high RPM) when I make
my initial power reduction (generally abeam the numbers). This causes
no noise increase, and time for me to double check as I fly the
pattern.

Hope this helps.
z

Do you do a final gear check on final? If so, then how much extra work
is it to push the prop to forward on final? This will only become an
issue if you are performing a go-around *and* you forget to push the
prop forward. Even if you forget the prop on final, I don't see how you
can forget it again on a go-around. The go-around procedure calls for
everything forward, and you will catch it if the prop is out.

Going prop forward after the governor has hit the limit is a good
practice. It makes less noise, and it demonstrates that you are smooth
at the controls.




zatatime wrote in
:

On Sun, 21 Nov 2004 23:51:25 GMT, Mitty wrote:

I've been taught to set the prop to high RPM on final, but I don't
like this very much because then, when I run my checklist for the
first time on downwind, I have to leave one item "open."

So what's wrong with doing it on downwind? (This in a Cherokee 6 or
and Arrow)
It seems to work fine, does not disarrange the engine, etc. I
suppose there
is some small noise increase, but hardly much.

So (1) is everyone taught to do it on final? (2) Why? (3) What's wrong
with doing it on downwind?

TIA


Full forward (high RPM) is in case of a go around. Going high pitch
mid-field will create a really loud racket on the ground. Waiting
until short final is too late in my opinion since we're human and can
forget things. To avoid this I go full forward (high RPM) when I make
my initial power reduction (generally abeam the numbers). This causes
no noise increase, and time for me to double check as I fly the
pattern.

Hope this helps.
z

On 21 Nov 2004 20:04:44 -0600, Andrew Sarangan
wrote:

Do you do a final gear check on final?
Yes
If so, then how much extra work
is it to push the prop to forward on final?
For my philosophy the final check, should be just that - only a check,
no work unless an error has occurred. Subtle I'm sure, but the less
"work" on short final the better IMO.

This will only become an
issue if you are performing a go-around *and* you forget to push the
prop forward. Even if you forget the prop on final, I don't see how you
can forget it again on a go-around. The go-around procedure calls for
everything forward, and you will catch it if the prop is out.
If in your mind you think you pushed it forward you'll probably
realize it isn't only after the throttle has been pushed full forward.
(I know not an absolute, but more likely than not for an average
person). If it does happen you'll be way "over square" and
potentially do alot of engine damage. Not withstanding the damage
potential, you could get alarmed by the condition, fixate on
rectifying it, and relax the pitch control. In heavier airplanes you
could get enough of a pitch up that it's hard for a person to recover.
I'm not being sexist, but I had this happen to a woman I was flying
with, lets just say it was a good learning experience for her. g
This was in a 172RG so heavy is a relative term.


Going prop forward after the governor has hit the limit is a good
practice. It makes less noise, and it demonstrates that you are smooth
at the controls.
Now i"m confused. It seems like we agree. I may not have been clear,
or may have missed something, but this is what I meant when I said to
go full forward after throttle reduction.

z

zatatime wrote in message . ..
On 21 Nov 2004 20:04:44 -0600, Andrew Sarangan
wrote:


Going prop forward after the governor has hit the limit is a good
practice. It makes less noise, and it demonstrates that you are smooth
at the controls.
Now i"m confused. It seems like we agree. I may not have been clear,
or may have missed something, but this is what I meant when I said to
go full forward after throttle reduction.



I was not specifically responding to your comment. It was in response
to the original poster who wanted to bring the prop forward on
downwind prior to power reduction. Whether the prop is brought forward
at downwind, base or final is not important as long as it is done
after power reduction. Earlier the better I suppose. On a VFR traffic
pattern, I bring the prop forward after power reduction just as I am
turning base. On an instrument approach, I would do that after the
power reduction at the final approach fix.

"zatatime" wrote in message
...
On 21 Nov 2004 20:04:44 -0600, Andrew Sarangan
wrote:

Do you do a final gear check on final?
Yes
If so, then how much extra work
is it to push the prop to forward on final?
For my philosophy the final check, should be just that - only a check,
no work unless an error has occurred. Subtle I'm sure, but the less
"work" on short final the better IMO.

This will only become an
issue if you are performing a go-around *and* you forget to push the
prop forward. Even if you forget the prop on final, I don't see how you
can forget it again on a go-around. The go-around procedure calls for
everything forward, and you will catch it if the prop is out.
If in your mind you think you pushed it forward you'll probably
realize it isn't only after the throttle has been pushed full forward.
(I know not an absolute, but more likely than not for an average
person). If it does happen you'll be way "over square" and
potentially do alot of engine damage. Not withstanding the damage
potential, you could get alarmed by the condition, fixate on
rectifying it, and relax the pitch control. In heavier airplanes you
could get enough of a pitch up that it's hard for a person to recover.
I'm not being sexist, but I had this happen to a woman I was flying
with, lets just say it was a good learning experience for her. g
This was in a 172RG so heavy is a relative term.


Almost every turbocharged airplane engine ever built operates "over square"
on every takeoff and many operate "way over square". "Square" and
"oversquare" are myths that need to be buried alongside "the step". The
whole notion of "square" is simply an artifact of the units we choose for
MP. If we used inches of water or psi or anything besides the height of a
colum of a particular metal which conviently happens to be a liquid are room
temperature, the whole notion of "square" would never have come about. I'll
step down from my soapbox now.

Mike
MU-2
Helio Courier.

On Tue, 23 Nov 2004 21:08:45 GMT, "Mike Rapoport"
wrote:

Almost every turbocharged airplane engine ever built operates "over square"


We're not talking turbocharges airplanes for this one, however I do
understand the over square concept in takeoff, and other operations.
Aside from that, its a relationship that has been established. When
flying at 2200 RPM or so and going full power you run a greater risk
of breaking something than at full pitch (high RPM). This is all I
was trying to say.

z

Zatatime,

If it does happen you'll be way "over square" and
potentially do alot of engine damage.


Proof? Numbers? At least a working theory? "Oversquare" is a myth.
Operating out of allowed limits isn't, but "oversquare" is irrelevant.

--
Thomas Borchert (EDDH)

zatatime wrote in message . ..
On Sun, 21 Nov 2004 23:51:25 GMT, Mitty wrote:

I've been taught to set the prop to high RPM on final, but I don't like this
very much because then, when I run my checklist for the first time on downwind,
I have to leave one item "open."

So what's wrong with doing it on downwind? (This in a Cherokee 6 or and Arrow)
It seems to work fine, does not disarrange the engine, etc. I suppose there
is some small noise increase, but hardly much.

So (1) is everyone taught to do it on final? (2) Why? (3) What's wrong with
doing it on downwind?

TIA


Full forward (high RPM) is in case of a go around. Going high pitch
mid-field will create a really loud racket on the ground. Waiting
until short final is too late in my opinion since we're human and can
forget things. To avoid this I go full forward (high RPM) when I make
my initial power reduction (generally abeam the numbers). This causes
no noise increase, and time for me to double check as I fly the
pattern.

Hope this helps.
z


This one seems to work best for Me. Reduce Power, Increase RPM
setting. No Noise increase due to reduced power and it is already set
when I get to final.

Brian

"Mitty" wrote in message
...
I've been taught to set the prop to high RPM on final, but I don't
like this very much because then, when I run my checklist for the
first time on downwind, I have to leave one item "open."

So what's wrong with doing it on downwind? (This in a Cherokee 6 or
and Arrow) It seems to work fine, does not disarrange the engine, etc.
I suppose there is some small noise increase, but hardly much.

So (1) is everyone taught to do it on final? (2) Why? (3) What's wrong
with doing it on downwind?

TIA

There's ALWAYS a problem if one learns to do something mechanical
without understanding the reason for it. Not recommended. Here are some
possibilities, pro and con:

If your engine quits, you want the propeller the prop already at low
rpm, to lower drag. On the other hand if you have to abort the landing
and go around, you want it on high rpm for added low-speed thrust.

Always ask WHY? (You may have to try several instructors until you get a
reasonable answer.) Don't just memorize checklists mindlessly.

John Lowry
Flight Physics