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

"Dave Butler" wrote in message
...
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.


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.


More drag, by itself, can't improve angle of climb. They must have had
another reason.

Mike
MU-2

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 did some extensive testing in a Beech Sierra and discovered that gear
up or down makes extremely little difference below Vy. Less than I
could reliably notice.

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.

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

Mmm, like others have said, I would think this is model specific.
You know when you accelerate for take-off...the increase in speed
takes proportionately longer as you get faster, so you use up much
more runway getting from 55 to 60 knots than 0-5 knots (basic
physics)...thus I would think that (for instance) if you start your
climb by lifting off at 55 knots rather than at 60, you've saved a
fair bit of runway. Usually I would guess that this distance saved
more than compensates for the slight decrease in climb angle with
flaps.

Paul

"Roy Page" wrote in message ink.net...
I have been trying to determine the length of a runway that would be
considered a "short field" for my Archer II.

Whether or not a field is short depends quite a bit on the density
altitude. A 2800 ft. runway at sea level and 69F isn't a short field
for the Archer. The same runway at 7,500 ft. and 100F is probably to
short even for the short field procedure.

Basically, the POH takeoff calculation for the particular runway
will tell you how much runway you'll need for a particular
runway/altitude/temperature combination. Do the calculation, add a
fudge factor, then decide whether or not the POH short field procedure
should be used.

John Galban=====N4BQ (PA28-180)

"Roy Page" wrote in message ink.net...
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.

At sea level or up to maybe ~ 1500MSL field elevations and at
"reasonable" density altitudes, I'd say short field would in an Archer
would be runways under 2500' long. A few years ago before I got my
PPASEL, I used to ride often with a fellow who operated a Cherokee 140
out of a 2000' private grass strip in the middle of Texas. Even in the
summer time, the 140 had no problems with the two of us on board with
fuel to the tabs. We were nowhere near max gross however, and had no
obstacles to clear at either end of the airstrip.

Gentlemen,

I really appreciate all the informed and learned replies to my question.
I know my Archer pretty well, and have flown rental Archers for a number of
years.
The POH is totally clear on the techniques regarding take-off and the use of
flaps.
I did not intend to ask questions which the POH properly covers.
My question is much more simple.
Where can I find the definition for a "Short Field" as referred to in my
POH.
The POH makes no attempt to define the length of the short field.
That's all I need guys, Where can I find either a defined formulae or Piper
specific definition of a "Short Field"

Thanks for all the great input that this question has created.

--
Roy
N5804F - PA28-181



have pored a POH and
"One's Too Many" wrote in message
om...
"Roy Page" wrote in message
ink.net...
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.

At sea level or up to maybe ~ 1500MSL field elevations and at
"reasonable" density altitudes, I'd say short field would in an Archer
would be runways under 2500' long. A few years ago before I got my
PPASEL, I used to ride often with a fellow who operated a Cherokee 140
out of a 2000' private grass strip in the middle of Texas. Even in the
summer time, the 140 had no problems with the two of us on board with
fuel to the tabs. We were nowhere near max gross however, and had no
obstacles to clear at either end of the airstrip.

Roy Page wrote:

Where can I find the definition for a "Short Field" as referred to in my
POH.

No such thing.


The POH makes no attempt to define the length of the short field.

Because it's a moving target. Weight, wind and air density all affect
performance.

Roy Page wrote:

Gentlemen,

I really appreciate all the informed and learned replies to my question.
I know my Archer pretty well, and have flown rental Archers for a number of
years.
The POH is totally clear on the techniques regarding take-off and the use of
flaps.
I did not intend to ask questions which the POH properly covers.
My question is much more simple.
Where can I find the definition for a "Short Field" as referred to in my
POH.
The POH makes no attempt to define the length of the short field.
That's all I need guys, Where can I find either a defined formulae or Piper
specific definition of a "Short Field"

Thanks for all the great input that this question has created.


I don't think "short field" is meant to be a definition of an airport.
It is meant to mean a takeoff or landing technique that minimizes either
the ground roll (in the case of no obstacles) or the total takeoff or
landing distance over an obstacle of a given height. It isn't a
specific length of runway as the capability of the airplane will vary
with density altitude, aircraft weight, CG location, etc.


Matt

On Sat, 20 Nov 2004 00:04:45 GMT, "Roy Page"
wrote:

Gentlemen,

I really appreciate all the informed and learned replies to my question.
I know my Archer pretty well, and have flown rental Archers for a number of
years.
The POH is totally clear on the techniques regarding take-off and the use of
flaps.
I did not intend to ask questions which the POH properly covers.
My question is much more simple.
Where can I find the definition for a "Short Field" as referred to in my
POH.
The POH makes no attempt to define the length of the short field.
That's all I need guys, Where can I find either a defined formulae or Piper
specific definition of a "Short Field"

Thanks for all the great input that this question has created.

"Short field" is any field that feels, or looks short to you. It will
vary with your competency/currency in techniques.

I land my Deb at a friends sod strip and think nothing of it. OTOH I
hear: "You landed on that short little strip? Good Lord, I was
stopped in half the strip length and well over 300 feet above the
trees on the way out without straining".

That was in a conversation with a 172 pilot.
To him it was a short field. To me it wasn't.

Bring in Cherokee in steep at book speeds and it'll use very little
distance to land and stop. Probably a lot less than it'll take to get
out.

Get the book out. Do the weight and take off distance over any
obstacles for the temperature. If the take off distance at the
current conditions is going to require good short field techniques to
get out, then it is a short field. IF you are proficient on short
field techniques (and I don't mean having done them a few times) it's
no big deal, but it will leave little margin for error, or for an
engine not developing full HP.

So there are two definitions of short field. If the field seems short
enough to make the pilot consider it short (whether it is or not), or
if the TO calculations show it to require short filed techniques then
it's a short field.

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