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

"BTIZ" wrote in message
news:lmfnd.106367$bk1.76106@fed1read05...

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


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.

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