The Threshold Of Immediate Control

This article discusses an interesting landing technique. Does anyone
use it?


http://www.aopa.org/members/files/pi.../ltol0508.html

License to Learn
The threshold of immediate control
BY ROD MACHADO (From AOPA Pilot, August 2005.)

....

And that's the way it was years ago when I was a very young flight
instructor in the right seat of a Cessna 210, where I witnessed a very
unusual behavior. The fellow I observed doing the deed looked like he
was performing miniature push-ups on the yoke, moving the elevator
forward and aft in small increments during the landing flare. It
appeared that he was pumping himself up to get down, and he continued
these shenanigans until the wheels kissed the concrete.

Stranger than the act was the action. While he was doing his tiny Jack
LaLanne biceps routine, and despite the forward and aft elevator
movement, I hardly felt the airplane pitch up or down, nor did I feel
his subsequent smooth landing. Equally remarkable was the fact that
his landings were consistently smooth nearly every time I flew with
him.

What was 210 Man doing here? Why would someone push and pull on the
elevator control during the landing? And why would this behavior
result in little or no pitch acceleration during the flare, much less
a smooth touchdown? The answer lies with a concept that I later came
to call the threshold of immediate control.

One of the reasons that pilots have difficulty making smooth landings
is their failure to anticipate and compensate for ground effect during
the flare. As an airplane approaches the runway surface, the wing's
downwash on the tail decreases, resulting in the nose pitching
forward. The manner in which downwash affects the airplane is
sometimes irregular and inconsistent, making it difficult to
anticipate, much less control, the downward-pitching nose.

It's as if the downward pitch of the nose sneaks up on a pilot and
doesn't allow much time for reaction. The result is often a series of
over- and undercorrections and eventually a hard landing. If it were
possible to compensate for the change in downwash by a linear increase
in back-pressure on the yoke, pilots would land more smoothly more
consistently, because most of us routinely attempt to pull back
steadily on the yoke as we flare. That's what we were taught to do.
But there's nothing linear about elevator control forces during the
flare, especially when flying larger single-engine airplanes.

There are many variables affecting the rate and degree to which the
nose pitches forward in these conditions (weight, center of gravity,
aircraft type, control surface size, and perhaps, phase of the moon).
To compensate for these variables (and make smoother landings as a
result), 210 Man manipulated the yoke with small back-and-forth
movements. His constant probing let him find the sweet spot where any
further pull would cause the nose to rise and any less would cause it
to fall. He was on the threshold of immediate control.

His technique prevented the natural forward pitching of the nose from
catching him unaware. By manipulating the flight controls in this way,
he knew precisely when to pull aft on the elevator and the precise
amount of pressure with which to pull to maintain the desired closure
rate with the runway.

To better understand this technique, here's another way of looking at
how you can apply it.

After the roundout and during the flare, apply continuous elevator
back-pressure, but do so in small pull-and-release motions. Think
about pulling just far enough aft so that the nose would rise beyond
the desired pitch if you pulled even a tiny bit more. As you begin to
release a tiny bit of elevator pull, you'll find a point where the
nose would drop with any additional release of pressure. You've
arrived at the threshold of immediate control. But the threshold is
always moving, so you have to keep testing. It's the constant
recalibration resulting from this pull-release motion that allows you
to make the airplane's nose stay right where you want it to stay and
lets you retain immediate control of the airplane's attitude. This
means that the airplane's nose shouldn't unsuspectingly pitch downward
without your being able to immediately stop its motion.

Now, you'd think that the airplane would be jumping up and down like
one of those mechanical bulls in a Texas bar. If done correctly, the
pull-release motions are small enough that no one in the cockpit will
feel any vertical pitch acceleration. This is especially true in
heavier single-engine airplanes, where small elevator movements don't
result in the airplane's immediate vertical acceleration. On the other
hand, the lighter the airplane, the more immediate will be the
vertical acceleration from even small elevator movements. The proper
application of this technique requires proportionally smaller
forward-and-aft yoke movements to remain in the threshold of immediate
control when flying airplanes in the weight class of a Cessna 150 or
Piper J-3 Cub.

Despite the lack of pitch acceleration, you'll still see the controls
moving forward and aft during the flare. That's what propelled my
eyebrows when observing 210 Man many years ago. This movement doesn't
matter as long as the airplane isn't pitching up and down and annoying
anyone on board. Remember, there are many ways to fly an airplane, and
this is just one technique to help some pilots make smoother landings.

Over the years, I've observed this technique being used by pilots who
I suspect had experienced a decline in their kinetic, visual, or
tactile sense (perhaps because they counted sunspots for recreation
and/or manicured their fingernails with power tools). It took me a
while to realize that what they were really doing was amplifying their
sense of elevator response. In this way, they were seldom surprised by
a sudden change in attitude because they were continuously making
micro control adjustments on the yoke and thus compensating for the
tail's aerodynamic surrender as it neared the runway.

As an aside, this pull-release technique is often used by pilots
making extreme short-field landings. Pilots operate deep in the region
of reversed command during these landings. Slight forward-and-aft
movement on the elevator lets them know how much (if any) aft elevator
travel is still available, as well as how effective the elevator
response is at that instant. The moment the elevator hits the stops,
the pilot knows he's reached the limit of the pitch envelope and must
now compensate with a change of power or forward pitch.

By practicing with the threshold of immediate control during a few
landings, you will gain a better idea of how best to flare your
airplane. I've used this strategy successfully with students
transitioning to larger machines, where the stick forces are
noticeably heavier throughout the flare.

Ideally, you should apply one continuous increasing pull on the
elevator during landing. As you get to know your airplane by using the
pull-release technique, you'll be in a better position to approach the
ideal.

Or not. Some people have a difficult time making landings any way
other than pull-release. So be it. While it may look a bit strange to
a close observer or new flight instructor, at least they'll land as
softly as a butterfly with sore feet.

Larry Dighera wrote:

This article discusses an interesting landing technique.Â*Â*DoesÂ*anyone
use it?


I've never heard of it. However, that does mimic the "dance" I do on the
pedals in a gusty xwind.

- Andrew

I think I have subconsciously done this at times. I'll pay more
attention; it makes a lot of sense to me.

Jose
--
Quantum Mechanics is like this: God =does= play dice with the universe,
except there's no God, and there's no dice. And maybe there's no universe.
for Email, make the obvious change in the address.

Sounds like over-analysis to me.

I remember being struck by a similar phenomenon while sitting in the
front seat of a biplane as a friend made an approach on a perfectly
calm day. I couldn't see my friend, but I could watch as the stick
did quite a little dance as settled toward the turf -- even though the
the air wassmooth and burble-free.

That in turn put me in mind of the tics and jerks and pattings of
furniture my blind friends exhibit, and which have been explained to
me as adaptations of proprioception that help them maintain their
equilibrium absent the visual input that the rest of us rely on.

In the cockpit, I think that many fliers unconsciously do something
like what Machado describes in order to maintain the "feel" of the
airplane in the flight regime where the ship does not respond to
control inputs as crisply as it does in cruise. Following the analogy
think of it as "flying blind with your eyes wide-open."

I'd bet that thinking about it would tend to screw you up.

Don

Yes, especially on the rudder in tailwheels.

Larry Dighera wrote:
This article discusses an interesting landing technique. Does anyone
use it?

I don't recognize the name, but the face is familiar (g).

Bob Gardner

"Larry Dighera" wrote in message
...
This article discusses an interesting landing technique. Does anyone
use it?


http://www.aopa.org/members/files/pi.../ltol0508.html

License to Learn
The threshold of immediate control
BY ROD MACHADO (From AOPA Pilot, August 2005.)

...

And that's the way it was years ago when I was a very young flight
instructor in the right seat of a Cessna 210, where I witnessed a very
unusual behavior. The fellow I observed doing the deed looked like he
was performing miniature push-ups on the yoke, moving the elevator
forward and aft in small increments during the landing flare. It
appeared that he was pumping himself up to get down, and he continued
these shenanigans until the wheels kissed the concrete.

Stranger than the act was the action. While he was doing his tiny Jack
LaLanne biceps routine, and despite the forward and aft elevator
movement, I hardly felt the airplane pitch up or down, nor did I feel
his subsequent smooth landing. Equally remarkable was the fact that
his landings were consistently smooth nearly every time I flew with
him.

What was 210 Man doing here? Why would someone push and pull on the
elevator control during the landing? And why would this behavior
result in little or no pitch acceleration during the flare, much less
a smooth touchdown? The answer lies with a concept that I later came
to call the threshold of immediate control.

One of the reasons that pilots have difficulty making smooth landings
is their failure to anticipate and compensate for ground effect during
the flare. As an airplane approaches the runway surface, the wing's
downwash on the tail decreases, resulting in the nose pitching
forward. The manner in which downwash affects the airplane is
sometimes irregular and inconsistent, making it difficult to
anticipate, much less control, the downward-pitching nose.

It's as if the downward pitch of the nose sneaks up on a pilot and
doesn't allow much time for reaction. The result is often a series of
over- and undercorrections and eventually a hard landing. If it were
possible to compensate for the change in downwash by a linear increase
in back-pressure on the yoke, pilots would land more smoothly more
consistently, because most of us routinely attempt to pull back
steadily on the yoke as we flare. That's what we were taught to do.
But there's nothing linear about elevator control forces during the
flare, especially when flying larger single-engine airplanes.

There are many variables affecting the rate and degree to which the
nose pitches forward in these conditions (weight, center of gravity,
aircraft type, control surface size, and perhaps, phase of the moon).
To compensate for these variables (and make smoother landings as a
result), 210 Man manipulated the yoke with small back-and-forth
movements. His constant probing let him find the sweet spot where any
further pull would cause the nose to rise and any less would cause it
to fall. He was on the threshold of immediate control.

His technique prevented the natural forward pitching of the nose from
catching him unaware. By manipulating the flight controls in this way,
he knew precisely when to pull aft on the elevator and the precise
amount of pressure with which to pull to maintain the desired closure
rate with the runway.

To better understand this technique, here's another way of looking at
how you can apply it.

After the roundout and during the flare, apply continuous elevator
back-pressure, but do so in small pull-and-release motions. Think
about pulling just far enough aft so that the nose would rise beyond
the desired pitch if you pulled even a tiny bit more. As you begin to
release a tiny bit of elevator pull, you'll find a point where the
nose would drop with any additional release of pressure. You've
arrived at the threshold of immediate control. But the threshold is
always moving, so you have to keep testing. It's the constant
recalibration resulting from this pull-release motion that allows you
to make the airplane's nose stay right where you want it to stay and
lets you retain immediate control of the airplane's attitude. This
means that the airplane's nose shouldn't unsuspectingly pitch downward
without your being able to immediately stop its motion.

Now, you'd think that the airplane would be jumping up and down like
one of those mechanical bulls in a Texas bar. If done correctly, the
pull-release motions are small enough that no one in the cockpit will
feel any vertical pitch acceleration. This is especially true in
heavier single-engine airplanes, where small elevator movements don't
result in the airplane's immediate vertical acceleration. On the other
hand, the lighter the airplane, the more immediate will be the
vertical acceleration from even small elevator movements. The proper
application of this technique requires proportionally smaller
forward-and-aft yoke movements to remain in the threshold of immediate
control when flying airplanes in the weight class of a Cessna 150 or
Piper J-3 Cub.

Despite the lack of pitch acceleration, you'll still see the controls
moving forward and aft during the flare. That's what propelled my
eyebrows when observing 210 Man many years ago. This movement doesn't
matter as long as the airplane isn't pitching up and down and annoying
anyone on board. Remember, there are many ways to fly an airplane, and
this is just one technique to help some pilots make smoother landings.

Over the years, I've observed this technique being used by pilots who
I suspect had experienced a decline in their kinetic, visual, or
tactile sense (perhaps because they counted sunspots for recreation
and/or manicured their fingernails with power tools). It took me a
while to realize that what they were really doing was amplifying their
sense of elevator response. In this way, they were seldom surprised by
a sudden change in attitude because they were continuously making
micro control adjustments on the yoke and thus compensating for the
tail's aerodynamic surrender as it neared the runway.

As an aside, this pull-release technique is often used by pilots
making extreme short-field landings. Pilots operate deep in the region
of reversed command during these landings. Slight forward-and-aft
movement on the elevator lets them know how much (if any) aft elevator
travel is still available, as well as how effective the elevator
response is at that instant. The moment the elevator hits the stops,
the pilot knows he's reached the limit of the pitch envelope and must
now compensate with a change of power or forward pitch.

By practicing with the threshold of immediate control during a few
landings, you will gain a better idea of how best to flare your
airplane. I've used this strategy successfully with students
transitioning to larger machines, where the stick forces are
noticeably heavier throughout the flare.

Ideally, you should apply one continuous increasing pull on the
elevator during landing. As you get to know your airplane by using the
pull-release technique, you'll be in a better position to approach the
ideal.

Or not. Some people have a difficult time making landings any way
other than pull-release. So be it. While it may look a bit strange to
a close observer or new flight instructor, at least they'll land as
softly as a butterfly with sore feet.

Don Tuite wrote:

I'd bet that thinking about it would tend to screw you up.

Very possibly.

I was fencing for a little while before college. The fencing coach in
college had us really "study" what we did; something I'd never done before.

As a result, I recall one bout where I tried to move both forward and
backward at the same time. The result was remarkable like a stall: I
dropped like a rock.

Onlookers feared for my health, and not because I'd hit the ground grin.

- Andrew

P.S. The end result of that "study" was significant improvement.
It also let me to be able to improve my own style. But it
had a cost laugh.

"Larry Dighera" wrote in message
...
This article discusses an interesting landing technique. Does anyone
use it?


http://www.aopa.org/members/files/pi.../ltol0508.html

License to Learn
The threshold of immediate control
BY ROD MACHADO (From AOPA Pilot, August 2005.)

...

And that's the way it was years ago when I was a very young flight
instructor in the right seat of a Cessna 210, where I witnessed a very
unusual behavior. The fellow I observed doing the deed looked like he
was performing miniature push-ups on the yoke, moving the elevator
forward and aft in small increments during the landing flare. It
appeared that he was pumping himself up to get down, and he continued
these shenanigans until the wheels kissed the concrete.


Before I started lessons, my previous couple of flights were as pax in a
C-180 on floats. The pilot used that exact technique for water landings.

The first time my instructor had me "land by myself", I tried to approximate
the same small back-and-forth in the flare, believing this to be a standard
technique.

He nearly took my head off.

I thought I was the only one until I read Rod's article today! I have
used this technique, more or less subconsciously when flaring larger
low wing singles, to coax a greaser out of the landing. If you are
slightly on the fast side and you encounter ground effect this comes in
handy. If you are slow or right on your desired touchdown speed then I
find I use it less.
That being the case, I too have found hostility from some instructors
or check airmen. "Don't do that....you'll end up porpoising." "Don't
do that its poor technique."
"But...the landing was perfect?" "Doesn't matter it's poor technique!"
(I think thats why I gave up piano lessons years ago...had an
instructor who loved to say "that's poor technique")

I'm sticking with Rod on this one.
PTB

In article ,
Larry Dighera wrote:

This article discusses an interesting landing technique. Does anyone
use it?

Yeah, I do that sometimes...when I'm really working for a super greaser.
I've watched others do it also.

--
Dale L. Falk

There is nothing - absolutely nothing - half so much worth doing
as simply messing around with airplanes.

http://home.gci.net/~sncdfalk/flying.html