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

I have been trying to determine the length of a runway that would be
considered a "short field" for my Archer II.
The two instructors that I work with on occasions disagree on the amount of
flaps to use for takeoff at gross weight.
One guy says my airfield with a 2,800ft runway is a "short field" and I
should use 25deg flaps as per the POH for takeoff at gross weight.
The other says 2,800ft is not a short field and I should use 10 deg flap at
gross weight and that 25 deg increases drag too much.
It does not help that the instructors have a low opinion of each other.
The POH is clear about using 25 deg for a short field but I have failed to
find what runway length puts in a short field category.
These guys also instruct in a PA28-140 based here and you can guess that
some students are using 1 notch of flap, while the other set use 2 notches.

So the question is.
How long is a "short field" for a PA28-181 ? And for that matter how does
that relate to a PA28-140 with 30 less horses.

--
Roy
N5804F - PA28-181

On Thu, 18 Nov 2004 02:34:16 GMT, "Roy Page"
wrote:

One guy says my airfield with a 2,800ft runway is a "short field" and I
should use 25deg flaps as per the POH for takeoff at gross weight.
In the summer, heavily loaded I'd say he's right. In the summer with
obstacles at the end of the runway I'd also say he's right.

The other says 2,800ft is not a short field and I should use 10 deg flap at
gross weight and that 25 deg increases drag too much.
In the winter, or fall with a headwind I'd say he's right. At a field
with no obstacles and fields beyond the end of the runway, I'd also
say he's right.



There is no cut and dry answer to this. You need to learn your
airplane. Look at the POH and make a determination of what you feel
is appropriate for your skill level. It's pretty obvious these two
are fighting for fighting sake since they are arguing over something
that is situationally dependant, and one of the "finer" points of
flying. If you're completely in doubt use the 25 the POH says and you
should get close to what the charts depict for short field performance
assuming a descent engine and airframe.

HTH & Good luck with those two.

z

Try taking the landing and take off distances over a 50 ft obstacle and
doubling them. Anything at or under those distances I'd consider using the
short field techniques.

I just grabbed an old Archer II POH and ran my finger across the table I
come up with a rough guess short field take off over a 50 ft obstacle
distance of 1500 ft from a dry paved runway with 25 degrees of flaps at
standard conditions. Double that and you get 3000 ft. Under 3000 ft I'd
use the short field technique. Flaps up, same conditions takes 1850 feet.
Double that and you get 3700 ft.

Between 3700 and 3000 ft of runway, it would depend more on the
circumstances and conditions.

I'd apply the same rule of thumb to landings.

These numbers may sound way to conservative, but they give you a lot of
fundge factor on the safe side and I'd rather be safe than sorry. Most of
us don't fly factory fresh airplanes and most of us aren't test pilots.

Jim



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And don't forget density altitude!

Look at the POH and determine what the take off distance is over a 50ft
obstacle, normal take off (no flaps) Then compute the landing distance over
a 50ft obstacle. This will give you a very conservative Accelerate / Stop
distance estimate. If the runway in use is shorter than that, then you may
not be able to accelerate to rotation speed, chop the throttle and safely
stop. I would use the short field take off procedure.

If the POH does not list take off data for 1 notch of flaps, and states to
use 2 notches for a short field. Then I would use 2 notches and not pay
attention to the instructor that says to use only one notch.

With no data in the POH for a "modified short field technique", then you are
a test pilot and only can reasonably estimate that the required distance to
clear the 50ft obstacle is somewhere between the no flap (normal) departure
and the prescribes short field (2 notch) departure.

I can read the NTSB report now, pilot attempting take off from a short field
did not follow the prescribed takeoff procedure and failed to outclimb the
obstacle on departure. Causal factor: Pilot error.

jmho
BT

"Roy Page" wrote in message
nk.net...
I have been trying to determine the length of a runway that would be
considered a "short field" for my Archer II.
The two instructors that I work with on occasions disagree on the amount
of flaps to use for takeoff at gross weight.
One guy says my airfield with a 2,800ft runway is a "short field" and I
should use 25deg flaps as per the POH for takeoff at gross weight.
The other says 2,800ft is not a short field and I should use 10 deg flap
at gross weight and that 25 deg increases drag too much.
It does not help that the instructors have a low opinion of each other.
The POH is clear about using 25 deg for a short field but I have failed to
find what runway length puts in a short field category.
These guys also instruct in a PA28-140 based here and you can guess that
some students are using 1 notch of flap, while the other set use 2
notches.

So the question is.
How long is a "short field" for a PA28-181 ? And for that matter how does
that relate to a PA28-140 with 30 less horses.

--
Roy
N5804F - PA28-181

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

"BTIZ" wrote in message
news:2VUmd.106033$bk1.85623@fed1read05...
Look at the POH and determine what the take off distance is over a 50ft
obstacle, normal take off (no flaps) Then compute the landing distance
over a 50ft obstacle. This will give you a very conservative Accelerate /
Stop distance estimate. If the runway in use is shorter than that, then
you may not be able to accelerate to rotation speed, chop the throttle and
safely stop. I would use the short field take off procedure.

If the POH does not list take off data for 1 notch of flaps, and states to
use 2 notches for a short field. Then I would use 2 notches and not pay
attention to the instructor that says to use only one notch.

With no data in the POH for a "modified short field technique", then you
are a test pilot and only can reasonably estimate that the required
distance to clear the 50ft obstacle is somewhere between the no flap
(normal) departure and the prescribes short field (2 notch) departure.

I can read the NTSB report now, pilot attempting take off from a short
field did not follow the prescribed takeoff procedure and failed to
outclimb the obstacle on departure. Causal factor: Pilot error.

jmho
BT

"Roy Page" wrote in message
nk.net...
I have been trying to determine the length of a runway that would be
considered a "short field" for my Archer II.
The two instructors that I work with on occasions disagree on the amount
of flaps to use for takeoff at gross weight.
One guy says my airfield with a 2,800ft runway is a "short field" and I
should use 25deg flaps as per the POH for takeoff at gross weight.
The other says 2,800ft is not a short field and I should use 10 deg flap
at gross weight and that 25 deg increases drag too much.
It does not help that the instructors have a low opinion of each other.
The POH is clear about using 25 deg for a short field but I have failed
to find what runway length puts in a short field category.
These guys also instruct in a PA28-140 based here and you can guess that
some students are using 1 notch of flap, while the other set use 2
notches.

So the question is.
How long is a "short field" for a PA28-181 ? And for that matter how does
that relate to a PA28-140 with 30 less horses.

--
Roy
N5804F - PA28-181

Mike Rapoport wrote:
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.

I don't have any documentary evidence, but this is counterintuitive and contrary
to my unquantified experience. The Cherokees feel like they go up at a much
steeper angle with the flaps. Is it an illusion?

"Dave Butler" wrote in message
...
Mike Rapoport wrote:
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.

I don't have any documentary evidence, but this is counterintuitive and
contrary to my unquantified experience. The Cherokees feel like they go up
at a much steeper angle with the flaps. Is it an illusion?


I think so. The Helio Courier flight manual gives different flap settings
for minimium ground run vs. minimiunm 50' obstacle clearance with a lower
flap setting for the obstacle clearance distance. These airplanes have more
sophisticated flaps than a Cherokee (single slotted fowler flaps on the
Helio) so I assume that the Cherokee is even more disadvantaged as the flaps
are deployed since they are creating relatively more drag for each increment
of increased lift. Of course, if the runway is not hard and dry, anything
that reduces ground roll will likely reduce the obstacle distance.

Also, the maximium performance takeoff in a Super Cub is to accelerate with
the flaps retracted and then deploy full flaps to break ground, then to
reduce flaps while accerating in ground effect to Vx and then to climb at
Vx. It is impressive to see someone do this well.

You will need more pitch with the lower flap setting.

Perhaps someone with a newer Cherokee could look in the manual and see if
there are obstacle clearance charts for the different takeoff
configurations?

Mike
MU-2

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

"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