Variations in soft field landings

Maxwell wrote:
I was taught to lift the flaps immediately upon touch down on soft field
landings. My instructors stated getting more weight on the brakes as soon as
possible, would facilitate a quicker stop than leaving the flaps down for
drag, and loosing some braking power to the extra lift.

However, during my last BFR, the instructor corrected me very sharply. He
insisted you get more drag from the flaps by leaving them down until you
slowed to taxi speed, than the benefit of more weight on the brakes.

What is the general consensus of the group? Flaps up or down, after
touchdown on a soft field landing?

First of all, have you checked your POH for clues?

Second, I think you have short and soft confused.

Soft fields slow the plane without brakes with surface drag. You don't
really want to STOP on a soft field, as you might even sink in. I was
taught to think ahead, so I didn't have to stop while taxiing on soft
conditions. I'd leave the flaps deployed while I concentrated on using
the elevator to keep the nose gear off the turf as much as possible,
which will also provide plenty of aero braking.

Short, paved fields are a different story. My Beech Sundowner has much
less braking ability with the flaps deployed, so I raise them as a
course of habit on pavement. The Piper PA-28 variations I've flown had
much better braking with the flaps out, raising the flaps didn't offer
anywhere near the braking improvement as with the Beech.

It's the old "my instructor said..." story instead of reading the book. The
Airplane Flying Handbook says, on page 8-20, "If flaps are used, it is
generally inadvisable to retract them during the after-landing roll because
the need for flap retraction is usually less important than the need for
total concentration on maintaining full control of the airplane."

Gotta wonder (1) why the flaps-up instructor doesn't go by the book, and (2)
why you swallow his story without asking for documentation for his method.

Bob Gardner


"Maxwell" wrote in message
m...
I was taught to lift the flaps immediately upon touch down on soft field
landings. My instructors stated getting more weight on the brakes as soon
as possible, would facilitate a quicker stop than leaving the flaps down
for drag, and loosing some braking power to the extra lift.

However, during my last BFR, the instructor corrected me very sharply. He
insisted you get more drag from the flaps by leaving them down until you
slowed to taxi speed, than the benefit of more weight on the brakes.

What is the general consensus of the group? Flaps up or down, after
touchdown on a soft field landing?

"Bob Gardner" wrote in message
news
It's the old "my instructor said..." story instead of reading the book.
The Airplane Flying Handbook says, on page 8-20, "If flaps are used, it is
generally inadvisable to retract them during the after-landing roll
because the need for flap retraction is usually less important than the
need for total concentration on maintaining full control of the airplane."

Gotta wonder (1) why the flaps-up instructor doesn't go by the book, and
(2) why you swallow his story without asking for documentation for his
method.


Gotta wonder what page Bob, my copy doesn't specify under short field
landings. And a lot of inquiring minds here seem to disagree.

On Apr 25, 2:54 pm, "Maxwell" wrote:
I was taught to lift the flaps immediately upon touch down on soft field
landings. My instructors stated getting more weight on the brakes as soon as
possible, would facilitate a quicker stop than leaving the flaps down for
drag, and loosing some braking power to the extra lift.

However, during my last BFR, the instructor corrected me very sharply. He
insisted you get more drag from the flaps by leaving them down until you
slowed to taxi speed, than the benefit of more weight on the brakes.

What is the general consensus of the group? Flaps up or down, after
touchdown on a soft field landing?

Please ignore my comments about soft-field landings (although I still
think you should use your reference material when your instructor says
something questionable instead of accepting it as gospel). The
Airplane Flying Handbook is silent on retracting flaps after touching
down on short field...go by the POH recommendation.

Instructors are often wrong...I know because I are one.

Bob Gardner

On Wed, 25 Apr 2007 16:54:23 -0500, "Maxwell"
wrote:

I was taught to lift the flaps immediately upon touch down on soft field
landings. My instructors stated getting more weight on the brakes as soon as
possible, would facilitate a quicker stop than leaving the flaps down for
drag, and loosing some braking power to the extra lift.

However, during my last BFR, the instructor corrected me very sharply. He
insisted you get more drag from the flaps by leaving them down until you
slowed to taxi speed, than the benefit of more weight on the brakes.

What is the general consensus of the group? Flaps up or down, after
touchdown on a soft field landing?


Hopefully here won't be a consensus. It depends on the airplane,
pilot, and technique.

The short field landing which you are describing, rather than soft
field usually has a recommendation in the POH which may, or not give
the shortest landing possible including roll out. However that
landing was done using the best possible application of normal
techniques with a very good pilot who knew the specific make and model
far better than the average pilot.

One thing short field landings have in common is a STEEP final where
energy/speed is bled off in the round out. In some planes this means
carrying considerable power on the final just prior to the round out.
Dragging it in with the ability to set it down and stop on a postage
stamp is not a normal short field unless you are a bush pilot landing
on sand bars, or dragging it in over your neighbor's bean field. Even
then a good portion of the final (in ground effect) should be
considered as part of the landing.

There is one thing in normal short field landing I've heard with which
I disagree and that is holding the yoke back all the time. I plant
the mains on, immediately let the nose gear down, get on the brakes,
and THEN bring the yoke back again.

Something to remember in planes with electric flaps is the time it
takes to retract them and how much added lift you get during the
retraction. With most planes most of us are flying the last portion
of flap extension adds drag without adding lift. So when removing
flaps we remove drag, then add lift for a time before the flaps have
retraced enough to reduce the lift. I've found some planes where the
POH recommends raising the flaps can be almost brought to a stop
before the flaps are all the way up. That means in the latter portion
of the ground roll it didn't matter if the flaps were up or down. In
some of those cases raising the flaps adds lift right when you want to
get rid of it and removes drag right when it will do the most good.

One plane or rather group of planes where the retraction of the flaps
can be quite effective in shortening the rollout is the Cherokee
family that has the Johnson bar flaps (Mechanical). Actually it's the
only plane I've flown where the difference is quite noticeable.

"I believe" which is a personal opinion based only on my experience in
the specific 150s, 172s, Cherokees, Debonairs, and Bonanzas I've
flown, that it is possible to make the shortest landing possible by
leaving the flaps at full and a lot of practice. OTOH With the 150s
and 172s I doubt if most pilots are going to be able to see much if
any difference whether the flaps are raised or left down.

Roger (K8RI) wrote:


There is one thing in normal short field landing I've heard with which
I disagree and that is holding the yoke back all the time. I plant
the mains on, immediately let the nose gear down, get on the brakes,
and THEN bring the yoke back again.


Then you're too fast to start with. A short field landing is a
bang-bang play. Bang, the mains hit, then bang the nose wheel hits.
Stick position is irrelevant and won't really affect what happens with
the nosewheel because if you have your speed right any additional drag,
such as the mains hitting, means she's all done flying. The nose is
coming down and nothing short of a lot of power is going to change that.





Something to remember in planes with electric flaps is the time it
takes to retract them and how much added lift you get during the
retraction. With most planes most of us are flying the last portion
of flap extension adds drag without adding lift. So when removing
flaps we remove drag, then add lift for a time before the flaps have
retraced enough to reduce the lift.




Not correct. From full flaps, retracting any amount of flaps will
always reduce the total amount of lift the flaps are providing. On your
typical Cessna the majority of the lift comes in the first 20 degrees
with not a lot of added drag. But going from 20 to 40 degrees does add
lift, that's why the stall speed is lower at 40 flaps than at 20. So
reducing any flaps reduces lift, it raises the stall speed thereby
putting more weight on the wheels.

"Maxwell" wrote in
m:

I was taught to lift the flaps immediately upon touch down on soft field
landings. My instructors stated getting more weight on the brakes as
soon as possible, would facilitate a quicker stop than leaving the flaps
down for drag, and loosing some braking power to the extra lift.

However, during my last BFR, the instructor corrected me very sharply.
He insisted you get more drag from the flaps by leaving them down until
you slowed to taxi speed, than the benefit of more weight on the brakes.

What is the general consensus of the group? Flaps up or down, after
touchdown on a soft field landing?

I think it depends more on how fast you land...

If you land right at stall speed, retracting the flaps might help you break.
If you are faster, retracting the flaps will probably extend your rollout.

There are also a lot of people who say you shouldn't be under there during
that part of the landing phase in case some day you are flying a retract and
grab the wrong lever. Of course then those people go on to do go arounds and
touch and goes and do it anyway.