What is a "short field" for a PA28-181

Archer II
Take off ground roll flaps 25 degrees is about 875 ft standard conditions,
dry, paved, level..... Lift off speed 49 knots, barrier speed 54 knots at
gross weight 1850ft over an obstacle

Flaps up is about 975 ft standard conditions, dry, paved, level.....Lift off
speed 53 knots, barrier speed 58 knots at gross weight, about 1550 ft over
an obstacle



"Jim Burns" wrote in message
...
I thought of that question also and I'll check tonight when I get home. I
would think that a "normal" takeoff would be to Vy and a short field to
Vx.
But then again sometimes "normal" has many definitions!

Jim

"Mike Rapoport" wrote in message
hlink.net...
Thanks. Are both takeoffs to Vx?

Mike
MU-2


"Jim Burns" wrote in message
...
The one I looked at was an Archer II POH.

25 degrees of flaps, standard conditions, dry, paved, level runway was
about
1500 ft over 50 ft obstacle

0 flaps, same conditions takes about 1850 ft over a 50ft obstacle

Those were the only two configurations given.

I didn't compare ground roll distances but that would indeed be
interesting.

And you are correct, the Super Cub is impressive. I did my tailwheel
checkout in a SC. We never used the flaps off, flaps on, flaps off
technique, but even so, once you break ground you can pull the stick
back
as
far as you want and it just goes UP!

Jim


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PaulaJay1 wrote:
: In article PM7nd.527035$mD.5173@attbi_s02, (Ben Jackson) writes:

:I fly a warrior. If I am not doing a short field technique I usually
:take off with one notch of flaps.
:
:In the Comanche one notch of flaps makes for a much crisper transition
:from rolling to flying. The takeoff angle is noticably steeper, too.
:

: With my Archer if I put in 2 notches of flaps at 60 knots, I rise
: like a helo.

Ditto with my Cherokee 180 (straight wing Archer).
--
Aaron Coolidge

On Thu, 18 Nov 2004 15:32:32 -0500, Dave Butler
wrote:

Mike Rapoport wrote:
wrote in message
...

Mike Rapoport wrote:
: Keep in mind that the short field settings shorten the ground run but
: generally increase the distance to clear a 50' obstical.

Isn't that the *point* of short field technique... to get off and over in
the
shortest distance? There would appear to be a logical flaw to that
statement.

I would agree that it will take more *time* to get to a given altitude at
(e.g. 50' obstacle clearance)... Short field performance is defined to
give the best
obstacle clearance per *distance*. I would agree that soft-field
technique will
increase distance, but short is short.

Am I missing something?


Maybe :-) If the short field takoff is using a higher drag, higher lift
configuration (more flaps) to get off the ground at a lower speed (shorter
roll) it then takes longer (in both time and distance) to make the climb
over the obstacle because of the higher drag configuration. I hope this
makes sense.

Yes, it makes sense, but I don't think it always holds up in practice. For
example, in my Mooney, the recommended obstacle clearance technique is to not
retract the gear until the obstacle is cleared. More drag gives a greater
-angle- of climb.

I really have a problem with that, and would like to see some quantitative
evidence. It flies in the face of all the laws of physics that I am
familiar with.



In the Helio, the shortest ground roll is with 40 degrees of flaps but the
shortest distance over a 50' obstacle is with 30 degrees of flaps.

It seems the configuration for best angle is model-specific.

On 18 Nov 2004 22:28:49 GMT, (PaulaJay1) wrote:

In article PM7nd.527035$mD.5173@attbi_s02, (Ben Jackson) writes:

I fly a warrior. If I am not doing a short field technique I usually
take off with one notch of flaps.

In the Comanche one notch of flaps makes for a much crisper transition
from rolling to flying. The takeoff angle is noticably steeper, too.


With my Archer if I put in 2 notches of flaps at 60 knots, I rise like a helo.

For how long?


Chuck

Mike is correct. Only "close in" obstacles are best cleared with flaps in
any GA airplane.

That is because all GA aircraft have only one Vx and Vy and they are ALWAYS
attained with ZERO flaps.

Climbing at a lower speed with flaps to clear obstacles is a compromise. In
order to get off the ground in the shortest distance flaps are used. But one
has to then climb at a speed that is lower than Vx. There becomes a point at
which you are better off to accelerate to Vx and retract the flaps. Then you
will be climbing at BEST angle, which is impossible to do with any flap out.

For instance, say you are taking off from a short strip in the Snake River
canyon. There are trees at the end of the runway. Most likely you will use
the short field procedure in the POH for takeoff, which will probably
include flaps. But, once clear of the trees you will want to get rid of the
flaps in order to clear the distant obstacles, such as a ridge five miles
away. Best angle is WITHOUT flaps.

On the kind of Cessna, Piper and Beechcraft airplanes discussed here, Vx and
Vy are "clean wing" numbers. The exceptions are some VERY unusual STOL wings
like on a DHC-2 Beaver, which does use some flap for all normal climbs.

Karl
"curator" Cessna A185F, N185KG


"BTIZ" wrote in message
news:%tcnd.106330$bk1.58516@fed1read05...
Well Mike, I do not have a PA-28-181 POH handy so I checked my old
PA-32-300
At sea level, At Max GW
Normal take off, 10degree flap setting, Ground Roll, 1050ft, 50ft
clearance 1500ft
Short Field take off, 25degree flap setting, Ground Roll, 950ft, 50ft
clearance, 1400ft.

Say again?

BT

"Mike Rapoport" wrote in message
ink.net...
The problem with this logic is that the 50' obstical distance is
genarally greater with the short field flap setting. Only the ground run
is shorter.

Mike
MU-2

I won't argue with your POH! Does it give the speeds on both takeoffs?

Mike
MU-2

1.2 Vs for both conditions, premature raising of the nose or raising it to
an excessive angle will result in a delayed takeoff. Normal takeoffs are
with 10degree flap settings. At MAX GW, accelerate to 65-70mph, slight back
pressure to let the airplane fly itself off the ground. Accelerate to normal
climb. Enroute climb speed is 115mph, gets the nose down for visibility and
air cooling into the engine and better forward speed.

Short Field no obstacle, 25degree flap settings and lift off at the same
65-70mph at MAX GW. The text does state that with no obstacle, accelerate to
best rate (Vy) 105mph

Short Field With an obstacle, 25 degree flap, lift off at lowest possible
airspeed and accelerate in ground effect to 95mph, (Vx), climb at 95mph
until the obstacle is cleared, then accelerate to 105mph (Vy)

I should add that this is from the 1973 PA-32-300, fixed gear, fat wings.

BT.

Jay Somerset wrote:
On Thu, 18 Nov 2004 15:32:32 -0500, Dave Butler
wrote:


Mike Rapoport wrote:

wrote in message
...


Mike Rapoport wrote:
: Keep in mind that the short field settings shorten the ground run but
: generally increase the distance to clear a 50' obstical.

Isn't that the *point* of short field technique... to get off and over in
the
shortest distance? There would appear to be a logical flaw to that
statement.

I would agree that it will take more *time* to get to a given altitude at
(e.g. 50' obstacle clearance)... Short field performance is defined to
give the best
obstacle clearance per *distance*. I would agree that soft-field
technique will
increase distance, but short is short.

Am I missing something?


Maybe :-) If the short field takoff is using a higher drag, higher lift
configuration (more flaps) to get off the ground at a lower speed (shorter
roll) it then takes longer (in both time and distance) to make the climb
over the obstacle because of the higher drag configuration. I hope this
makes sense.

Yes, it makes sense, but I don't think it always holds up in practice. For
example, in my Mooney, the recommended obstacle clearance technique is to not
retract the gear until the obstacle is cleared. More drag gives a greater
-angle- of climb.


I really have a problem with that, and would like to see some quantitative
evidence. It flies in the face of all the laws of physics that I am
familiar with.

It doesn't fly in the face of the laws of physics, if you remove the
erroneous part of his comment. More drag doesn't give a greater angle
of climb. The reason you don't retract the gear in most cases is that
the drag of the gear is highest during the retraction process. If you
could retract it instantly, then you would, but given that many
airplanes take several seconds to retract, you don't want that extra
drag between lift-off and the height of the obstacles you are trying to
clear.


Matt

Jay Somerset wrote:
Dave Butler wrote:
Yes, it makes sense, but I don't think it always holds up in practice. For
example, in my Mooney, the recommended obstacle clearance technique is to not
retract the gear until the obstacle is cleared. More drag gives a greater
-angle- of climb.

I really have a problem with that, and would like to see some quantitative
evidence. It flies in the face of all the laws of physics that I am
familiar with.

OK, I probably shouldn't have inferred the "more drag" statement from the POH
instructions. I retract that. Much as I like flying, into the face of the laws
of physics is not where I like to do it.

Nevertheless, as others have pointed out, Cherokees have a steeper angle of clib
with flaps than without, which supports my original observation.

"Dave Butler" wrote in message
...
Jay Somerset wrote:
Dave Butler wrote:
Yes, it makes sense, but I don't think it always holds up in practice.
For example, in my Mooney, the recommended obstacle clearance technique
is to not retract the gear until the obstacle is cleared. More drag gives
a greater -angle- of climb.

I really have a problem with that, and would like to see some
quantitative
evidence. It flies in the face of all the laws of physics that I am
familiar with.

OK, I probably shouldn't have inferred the "more drag" statement from the
POH instructions. I retract that. Much as I like flying, into the face of
the laws of physics is not where I like to do it.

Nevertheless, as others have pointed out, Cherokees have a steeper angle
of clib with flaps than without, which supports my original observation.

Didn't you read Jim Burns post? He reported the following:

Archer II
Take off ground roll flaps 25 degrees is about 875 ft standard conditions,
dry, paved, level..... Lift off speed 49 knots, barrier speed 54 knots at
gross weight 1850ft over an obstacle

Flaps up is about 975 ft standard conditions, dry, paved, level.....Lift off
speed 53 knots, barrier speed 58 knots at gross weight, about 1550 ft over
an obstacle

Clearly, if his POH is to be believed, the Archer climbs better with flaps
up.

Mike
MU-2

"Dave Butler" wrote in message
...

Nevertheless, as others have pointed out, Cherokees have a steeper angle
of clib with flaps than without, which supports my original observation.


No.

They do not.

Vx is without flaps. Period!

Karl