Prop to High RPM on downwind

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,

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).


How?

--
Thomas Borchert (EDDH)

Thomas Borchert writes:

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).

How?

Some airplanes have limitations on the space of usable RPM-vs-MP
settings. For example, on the pair of IO-540s in mine, prohibit
operation at MP25 with RPM2300, or MP20 with RPM2000. (I believe
the reason relates to resonance.) That is I push the blue levers
forward from 2200RPM (cruise) to do approaches at 2400RPM: this allow
harsher throttle swings if needed.

- FChE

Frank,

very interesting, thanks. Of course, as the first set of limitations
show, this has nothing to do with "oversquare", since the limit starts
at a "serious oversquare" condition.

--
Thomas Borchert (EDDH)

On Fri, 26 Nov 2004 18:23:13 +0100, Thomas Borchert
wrote:

Frank,

very interesting, thanks. Of course, as the first set of limitations
show, this has nothing to do with "oversquare", since the limit starts
at a "serious oversquare" condition.


Does this mean yo now understand my "way over square" comment, and why
I put over square in quotes?

z

Zatatime,

Does this mean yo now understand my "way over square" comment, and why
I put over square in quotes?


I think the word oversquare should never be used in this context, ever.
Too much mischief has been wrought by doing that.

--
Thomas Borchert (EDDH)

On Mon, 22 Nov 2004 13:59:04 -0800, "Peter Duniho"
wrote:

"Chris" wrote in message
...
[...]
With the 182, it is 80 knots turning from the 45 to downwind, 75 on base,
and 70
on final. I don't understand why pushing the prop to full flat has any
noise
effect whatsoever.

Exactly

Exactly, except for those airplanes that cannot maintain level flight at
pattern speed with gear and flaps out at final descent power settings.


You should hear me on a circle to land. Gear out, bout 20-25 deg of
flaps and go to cruise power until within about 30 degrees of the
landing runway heading. Then back to about 12" and full flaps. Turning
with everything hanging out while maintaining altitude takes about
22-23" of MP at 2400 RPM. At that power setting and low altitude
~500' AGL I try to keep it over the airport for the full circle to
land.

Which is, by the way, all airplanes with a constant speed prop. The power
setting for final descent is necessarily lower than that required for level
flight within the pattern, even if you slowed ALL the way to your final
approach speed. RPM will thus be higher, assuming the pitch is set to full
fine pitch (high RPM). Higher RPM means more noise.

For a VFR pattern: On my old Debonair they taught; slow to 110-100 on
down wind, 90 on base and 80 minus 1 MPH for each 100# under gross on
final. This produces quite a steep final, but with the consequences
of a relatively short roll out.

I generally start the descent after gear down at the end of the runway
on down wind. Prior to that with the old 2-blade prop would have been
noisy.

Some airports want you to keep pattern altitude much longer. Some till
you start final.

I would add that I'm usually coming down hill just prior to the 45
entry (pattern alt one to two miles out) and the Deb takes its time
slowing down. I probably have the MP back to the point where the prop
is already turning slower prior to pattern entry.

Sooo... power is back (but a long way from idle) prior to pattern
entry, down wind is basically low power (16"-17")with the Deb slowing
down. Gear down at the end of the runway and a bit of flaps down to
about 100 MPH, MP about 12". Turn base, add flaps, retrim for the
slower speed of 90, Turn final, full flaps, speed ~75-80, prop full
in. Adjust MP to maintain aiming point.

Actually if I enter a bit on the fast side while slowing down I use
less power in the pattern than I would if I entered the pattern at 110
as I'd have to apply power on down wind while I'm normally reducing
power.

If I didn't put the gear down until I had the runway made it'd be one
mighty big pattern power off. Almost as big as some of the local
Cessnas and Cherokees fly. (sorry, I couldn't help it) :-))

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
If Jim's 182 flies along level in the pattern at the same airspeed and prop
RPM that he uses for final descent, I have no idea how he accomplishes a
final descent at all. A plane like that would be stuck up in the pattern
indefinitely.

Pete

In article ,
Roger wrote:

On Mon, 22 Nov 2004 13:59:04 -0800, "Peter Duniho"
wrote:

"Chris" wrote in message
...
[...]
With the 182, it is 80 knots turning from the 45 to downwind, 75 on base,
and 70
on final. I don't understand why pushing the prop to full flat has any
noise
effect whatsoever.

Exactly

Exactly, except for those airplanes that cannot maintain level flight at
pattern speed with gear and flaps out at final descent power settings.


You should hear me on a circle to land. Gear out, bout 20-25 deg of
flaps and go to cruise power until within about 30 degrees of the
landing runway heading. Then back to about 12" and full flaps. Turning
with everything hanging out while maintaining altitude takes about
22-23" of MP at 2400 RPM. At that power setting and low altitude
~500' AGL I try to keep it over the airport for the full circle to
land.

I much prefer the 360 overhead pattern:

1) flying at cruise down the runway at pattern altitude from about 2
miles out (Initial) to just past the threshold,

2) break to downwind (traffic permitting), pulling power as you break,

3) Keeping at least 45 deg bank, drop gear and flaps when appropriate
speed is reached (usually at the 180 deg point),

4) slow to approach speed, while turning and keeping TD point in sight,

5) touch down on full 3-point attitude on the numbers.

Properly done, you don't add power any time after the break -- it is a
continuous circle to touchdown. It is the easiest way to recover a
formation -- each plane breaks at 2 - 4 second intervals. I do this all
the time in my Johnson Rocket; I have done it in a Zlin 242 and a
friend's big-engined T-34. The whole "pattern is within a 1/4 to 1/2
mile of the runway.

Prop goes in when you reach approach speed.

On Sun, 28 Nov 2004 04:39:45 GMT, Orval Fairbairn
wrote:

In article ,
Roger wrote:

On Mon, 22 Nov 2004 13:59:04 -0800, "Peter Duniho"
wrote:

"Chris" wrote in message
...
[...]
With the 182, it is 80 knots turning from the 45 to downwind, 75 on base,
and 70
on final. I don't understand why pushing the prop to full flat has any
noise
effect whatsoever.

Exactly

Exactly, except for those airplanes that cannot maintain level flight at
pattern speed with gear and flaps out at final descent power settings.


You should hear me on a circle to land. Gear out, bout 20-25 deg of
flaps and go to cruise power until within about 30 degrees of the
landing runway heading. Then back to about 12" and full flaps. Turning
with everything hanging out while maintaining altitude takes about
22-23" of MP at 2400 RPM. At that power setting and low altitude
~500' AGL I try to keep it over the airport for the full circle to
land.

I much prefer the 360 overhead pattern:
Circle to land is an instrument procedure. 360 overhead is not an
option. I was commenting on the noise aspect. Also you are required
to maintain at or above MDA until within about 30 degrees of the
runway. (which can be about half the VFR pattern altitude.)

In the Deb the recommended approach speed is 120 while the VFR pattern
is *usually*: slow to 100-110 on down wind, gear down at the end of
the runway,. Flaps 10-15 degrees, MP about 12 to 14" until gear
down. base 90 with 20-25 degrees of flaps, final is 80 minus 1 MPH for
each 100# under gross which for me is normally around 75 -76 MPH. MP
is around 10" (give or take) and produces a steep descent "Prop on
final", Flaps go full usually just prior to the round out. There is
no trim change with flaps and by the time I reach the round out it's
usually full nose up trim.


1) flying at cruise down the runway at pattern altitude from about 2
miles out (Initial) to just past the threshold,

Doesn't that put you at odds with other traffic on cross wind or
departing? I hit pattern altitude right at the end of the runway on
climb out. (3800 ft runway) and we'd be in each others blind spots.

I almost took a plane head on at MOP while on an instrument approach
when he turned upwind over the runway at pattern altitude. I was
under the hood and all I heard from the instructor was, "Ohhhhh ****!
Pull up! Pull UP!". I hit the power and bout stood the old Deb on
end, bringing the nose down to hold Vx. He never would tell me how
close we were, but I did gather it was a matter of only a few feet.

I thought the 360 overhead with the break was done above pattern
altitude.

2) break to downwind (traffic permitting), pulling power as you break,

3) Keeping at least 45 deg bank, drop gear and flaps when appropriate
speed is reached (usually at the 180 deg point),

4) slow to approach speed, while turning and keeping TD point in sight,

5) touch down on full 3-point attitude on the numbers.

In a nose dragger?:-)) Albeit I usually touch down in the
appropriate attitude for a 3 point in a tail dragger. When I flew
with an AirSafety Foundation instructor he asked if I flew tail
draggers a lot after my first full stall landing.

Nor am I a proponent of touching down on the numbers unless it's a
short runway. Except on short runways I go for the touch down zone.
If it's a log way to the first turn off I ask to land long.

Properly done, you don't add power any time after the break -- it is a
continuous circle to touchdown. It is the easiest way to recover a
formation -- each plane breaks at 2 - 4 second intervals. I do this all
the time in my Johnson Rocket; I have done it in a Zlin 242 and a
friend's big-engined T-34. The whole "pattern is within a 1/4 to 1/2

The Deb is just a streamlined T34 with a door instead of a sliding
canopy. (It doesn't get airstream separation over the vertical stab
due to the canopy like the T-34) However a typical final takes a bit
of power. Power off is faster and uses quite a bit more runway. To
quote the POH, the extra speed when power off is to add enough energy
to flare. Power off is 90 to 95 while power on is 80 minus the one MPH
for each 100# under gross which makes for a much steeper descent and
shorter roll out. That extra 10 to 15 MPH will pretty much double the
required runway.

mile of the runway.

Prop goes in when you reach approach speed.

As most of my VFR pattern is decelerating I have no need to add power
and as the MP is low enough the prop control is no longer controlling
the RPM... Unless you pull it way out . I also fly a very tight
pattern, but try to keep it conventional due to a lot of students in
the pattern. They get a big enough surprise with instrument
approaches that come in at half their altitude.

OTOH I do not do the tight, steep approaches when carrying passengers.
Those are the gentle turns with gentle descents.

I do fly the occasional, stabilized pattern, but prefer to vary each
time which helps to know the airplane. If I do a stabilized pattern I
will have to add power as in the circle to land.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

In article ,
Roger wrote:
The Deb is just a streamlined T34 with a door instead of a sliding
canopy.

Yeah, but that canopy makes all the difference in terms of coolness.
Is there an STC to put a canopy on the Deb? ;-)

--
Ben Jackson

http://www.ben.com/