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

Newps wrote:


kage wrote:


On any standard light aircraft wing, all best climbs (rate of climb
Vy, and angle of climb Vx) are achieved with a clean wing. Adding
flaps causes the climb angle and rate to decrease.


Not on my 182. The manual says, and I quote...

Using 20 degree wing flaps reduces the ground run and total distance
over the obstacle by approx 20 percent.

And while I certainly don't have accurate instrumentation in the plane
my seat of the pants obsevation tells me that if I have to clear an
obstacle I want 20 flaps. I get off a lot shorter and climb to a given
altitude in a lot less real estate.

Yes, that is my recollection from when I owned a Skylane. It's takeoff
and climb with 20 flaps was impressive and I believe the speed
recommended in this configuration was something ridiculously low like 51
knots. I did this a few times for practice and the deck angle was
scary, but the old girl flew just fine.

I don't know the ins and outs of Vx and Vy, but it may be that they are
simply the best angle and rate with a clean wing, not that a clean wing
produces the best angle or rate. There is a difference...


Matt

kage wrote:

"Newps" wrote in message
...


kage wrote:


On any standard light aircraft wing, all best climbs (rate of climb Vy,
and angle of climb Vx) are achieved with a clean wing. Adding flaps
causes the climb angle and rate to decrease.

Not on my 182. The manual says, and I quote...

Using 20 degree wing flaps reduces the ground run and total distance over
the obstacle by approx 20 percent.



Yes over an obstacle. But that is a compromise. On a short strip the
compromise is less climb for shorter takeoff distance.

Your 182 manual NEVER says that Vx is with flaps. NOWHERE!

Vx in a 182 is clean wing. Read the POH.

Yes, but just because a clean wing has a certain velocity that provides
the best rate or angle in that configuration (no flaps), doesn't
necessarily mean that this is the best rate and angle that the airplane
is capable of achieving in other configurations. I don't know why Vx
and Vy are provided only in the clean configuration, but that may simply
be by definition and may not imply that this is the best that the
airplane is capable of.


Matt

kage wrote:

"Dave Butler" wrote in message
...

kage wrote:

"Newps" wrote in message


I don't see what is difficult to understand.
Vx is defined as best angle of climb. Do you have a hard time understanding
that concept?


The Cessna's and Piper's discussed here have POH's. The older ones have
owners manuals. In each of these documents Vx is listed. It is always listed
as a clean wing speed. Do you have difficulty with "clean wing?"

Thus, anytime you lower flaps, climb angle is reduced. I know you don't want
to believe that, and you are just playing dumb. Are you too lazy to just
look in your POH?

I believe Newps WAS quoting his POH? What part of that didn't you
understand? You also are aware that Vx and Vy aren't constants, right?
They vary with aircraft weight for one thing. And steady state best
angle and best rate of climb aren't necessarily correlated with the
takeoff regime and clearing an obstacle.


Matt

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

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


This doesn't make sense to me. How can the plane take off shorter if the
rotation is made at the same speed and the plane accelerates slower (with
the flaps down.)

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)


This sounds more like what I would expect. The question I now have is
whether the distance figures you gave earlier are for the "short field
with obstacle" or without the obstacle. Also the speeds I am interested
in are the speeds at the 50' obstacle.

The basic theory that I am espousing (supported by several POHs) is that a
certain amount of energy is added to the airplane between being stationary
on the ground and being 50' higher and moving at some speed. Since flaps
do nothing except increase the drag on the ground roll and have a lower
l/d, less energy is availible to accelerate and climb with the flaps down.
This is only valid if the speeds at the 50 obstacle are equal.

Mike
MU-2

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

BT.

Mike.. like I said, it's a 1973 manual... so details are not very forth
coming.

Previous distances were for normal (10degree flap) and short field (25
degree flap)
Speeds at the 50ft mark based on the text would not be the same.
Normal take off, 10degree flap, plane will lift off at about 65-70 and
allowed to accelerate in climb to enroute cruise climb speed of 115. The
50ft speed should be somewhere between 70 and 115.
Short field, lift off as soon as possible, accelerate in ground effect to 95
(Vx) and maintain Vx until clear of obstacle, so the 50ft speed should be
95.

The distance charts are not easy to interpolate, but the Max GW at Sea Level
differences are not much more than 100ft.

BT

"kage" wrote in message
...

"Dave Butler" wrote in message
...
kage wrote:

Vx is without flaps. Period!

OK, my batting average is not very good on this thread, what with flying
in the face of physics and all.

Please explain what your emphatic statement above means. I'm trying to
learn from this, but I'd like a little more detail than just defining
Vx by fiat.


On any standard light aircraft wing, all best climbs (rate of climb Vy,
and angle of climb Vx) are achieved with a clean wing. Adding flaps causes
the climb angle and rate to decrease.

Another way to look at it is the airspeed indicator. Anytime the IAS in
the green range, climb is best achieved with no flaps.

Aircraft that come to mind where this is not true are weird one's like the
DHC-2 Beaver and possibly the MU-2.

Karl


The MU-2 has a conventional wind for an airplane in its speed range and
definately climbs best with flaps up.

Mike
MU-2

Matt Whiting wrote:


Yes, that is my recollection from when I owned a Skylane. It's takeoff
and climb with 20 flaps was impressive and I believe the speed
recommended in this configuration was something ridiculously low like 51
knots. I did this a few times for practice and the deck angle was
scary, but the old girl flew just fine.


And I have VG's so I can climb well below the white arc.

Newps wrote:



Matt Whiting wrote:


Yes, that is my recollection from when I owned a Skylane. It's
takeoff and climb with 20 flaps was impressive and I believe the speed
recommended in this configuration was something ridiculously low like
51 knots. I did this a few times for practice and the deck angle was
scary, but the old girl flew just fine.


And I have VG's so I can climb well below the white arc.

I fly a 180 HP club Arrow now and boy do I miss the Skylane during
take-off and climb. The Arrow is marginally faster in cruise, but it is
a pig on take-off and climb, especially at lower airspeeds. It doesn't
climb well at all until above 80 knots.


Matt

"Matt Whiting" wrote in message
...
Newps wrote:


kage wrote:


On any standard light aircraft wing, all best climbs (rate of climb Vy,
and angle of climb Vx) are achieved with a clean wing. Adding flaps
causes the climb angle and rate to decrease.


Not on my 182. The manual says, and I quote...

Using 20 degree wing flaps reduces the ground run and total distance over
the obstacle by approx 20 percent.

And while I certainly don't have accurate instrumentation in the plane my
seat of the pants obsevation tells me that if I have to clear an obstacle
I want 20 flaps. I get off a lot shorter and climb to a given altitude
in a lot less real estate.

Yes, that is my recollection from when I owned a Skylane. It's takeoff
and climb with 20 flaps was impressive and I believe the speed recommended
in this configuration was something ridiculously low like 51 knots. I did
this a few times for practice and the deck angle was scary, but the old
girl flew just fine.

I don't know the ins and outs of Vx and Vy, but it may be that they are
simply the best angle and rate with a clean wing, not that a clean wing
produces the best angle or rate. There is a difference...


Matt


Maximium rate and angle of climb are both achieved with flaps up at Vx and
Vy. That doesn't mean that the best climb angle or rate at speeds below Vx
are with the flaps up. Take the extreme case where the speed is such that
the wing is stalled with flaps up but not with them down. Clearly in that
case the airplane will climb better with flaps down.

Mike
MU-2

Kage,

I guess it is you who is lazy. Too lazy to read the topic or think about it
straight. The majority will understand the concept of a clean wing and Vx.
But I do hope you understand the difference between the concepts of Vx and
Short Field Take Off, as they most certainly are not the same!

TMG

"kage" wrote in message
...

"Dave Butler" wrote in message
...
kage wrote:
"Newps" wrote in message

I don't see what is difficult to understand.
Vx is defined as best angle of climb. Do you have a hard time
understanding
that concept?


The Cessna's and Piper's discussed here have POH's. The older ones have
owners manuals. In each of these documents Vx is listed. It is always
listed
as a clean wing speed. Do you have difficulty with "clean wing?"

Thus, anytime you lower flaps, climb angle is reduced. I know you don't
want
to believe that, and you are just playing dumb. Are you too lazy to just
look in your POH?

Karl