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

Mike Rapoport wrote:

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

sigh back to my reading comprehension class... Thanks.

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.

"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.

"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

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.

"kage" wrote in message ...

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.


Excellent point. I do a lot of flying from high DA, short, canyon
strips with tall trees at each end, and I've found that the POH
directions don't really account for all of the combinations of
conditions. Where I fly, a short field is often also a soft field.
In that case, one needs to get the wheels off the draggy surface as
soon as possible in the ground roll. This requires a combination of
the short (with obstacle clearance) and soft field procedures.

In my Cherokee, flaps definitely make a difference for clearing 75
ft. trees at the end of a grass strip. Whether it's shorter because
it gets the wheels out of the tall grass, or because of a better angle
of climb, I don't know. I do know that without flaps, the trees are
much closer to the wheels as I pass over.

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

Over an obstacle figures should be reversed.
1850 OAO with flaps UP
1550 OAO with 25 degrees of flaps
mistake on my part, remainder of the post is correct.

Jim

"Jim Burns" wrote in message
...
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



---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.788 / Virus Database: 533 - Release Date: 11/1/2004

Jim Burns wrote:
Over an obstacle figures should be reversed.
1850 OAO with flaps UP
1550 OAO with 25 degrees of flaps
mistake on my part, remainder of the post is correct.

Thanks for the correction, Jim! That's more in line with my unscientific
observations.

Mine too. Sorry for the mistake, I had too many things going on when I
looked up that info.
Jim

"Dave Butler" wrote in message
...
Jim Burns wrote:
Over an obstacle figures should be reversed.
1850 OAO with flaps UP
1550 OAO with 25 degrees of flaps
mistake on my part, remainder of the post is correct.

Thanks for the correction, Jim! That's more in line with my unscientific
observations.



---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.788 / Virus Database: 533 - Release Date: 11/1/2004

"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.

Karl