Landing: Part III, The Flair
Alexander Burton, CFI
Pacific Rim Aviation Academy Inc.
Pitt Meadows Regional
Airport
“An artist’s flair is sometimes
worth a scientist’s brains.”
--Anton Chekhov--
In the last couple of months,
we have taken a look at the first stage of the landing process: the approach
and at the visual information flow affecting our performance as a pilot. We
discussed the idea that a good landing begins with a good approach and the
importance of understanding and knowing how to deal with the flow of visual
information our eyes provide our brain.
If our
approach is stabilized, we are well in control of airspeed, power, altitude,
attitude, rate of sink, and are making all the necessary corrections for
wind drift. Now we’re ready to initiate the flair phase of our landing. This
phase is a critical aspect of the landing process and will determine whether
we make a pretty and successful landing or whether we need to power up and
give the approach process another try.
As the
flair begins, we are on the verge of contact with the ground. Things are in
a dynamic state of change. We must be focused and alert but not fixated. As
hard as it may seem to be relaxed and open so close to the critical moment
of touchdown, this is the time to do just that. The less mental distance we
create between perception and response, the better equipped we will be to
deal with a rapidly changing situation.
Animals,
people, aircraft, or other vehicles can suddenly appear on the landing
surface. The wind, as we approach the ground, typically becomes more
uncertain and often varies its direction as a result of its interaction with
the ground and other physical barriers, buildings and trees, for example.
We must
appreciate the changing environment, remain alert and focused and be able to
respond moment to moment during this phase of flight.
Pilot
decision-making about visual focal points is a product of our training and
experience. Knowing where and how to look at things is an important factor
in ensuring a safe landing.
On
approach our major focal point has centred on our round-out point.
Maintaining a stabilized approach has assisted in this process. As we reach
the moment of flair, we will be adjusting the pitch attitude of the aircraft
from the descent attitude to the landing attitude and our visual focal point
must shift to accommodate this change in attitude.
Research
has demonstrated that by directing our central vision during flair at a
shallow downward angle, between 10 to 15 degrees toward the runway, we can
achieve good results. As the aircraft’s attitude changes during the flair,
our focal point will shift accordingly and progress down the runway as the
flair and descent continues (1).
When do we
commence the flair? Frequently, the answer is something like “At just the
right moment.” This, of course, is not a very satisfactory or helpful
answer.
Flair
height is a function of the speed and weight of an aircraft. The larger the
machine, the more time and distance is required to transition from the
descent attitude to a flight path roughly parallel with the runway surface.
For light, training aircraft, something in the neighbourhood of 20 feet
works very well.
So how in
the world do we know when we have reached that magic height? Our altimeter
is not really able to give us the precise information we need. Certainly it
is of some help, but our main clues will always come from outside unless, of
course, we are equipped with an auto-land system. Not a likely scenario in a
light, training type aircraft.
As we
discussed last time, the visual flow of information coming to us through our
eyes is subject to a number of illusions and our depth perception is working
at a low level as we approach at relatively high speed that onrushing
concrete, grass, or gravel surface. We must depend a great deal on our sense
of perspective and our peripheral vision to appreciate height and distance.
We all
know that objects of the same size, located at different distances, appear
to be different in size. The farther object will appear smaller than the
nearer. This capability—the capacity to evaluate distance in relation to
perspective—is vital to our appreciation of where we are and what comes
next. In addition, we obtain height information relative to any object with
a vertical dimension, for example, trees, buildings, vehicles, people,
through our peripheral perceptions.
Many
pilots will speak about the moment when the runway appears to begin to move.
This sense of relative motion occurs at just about the right moment to begin
our flair, as well. One of the most lucid accounts of this process is
provided by Wolfgang Langewiesche in his classic book, Stick and Rudder,
first published back in 1944 (2).
I can
highly recommend this excellent book, a delightful reading experience for
pilots of all ages.
Of course,
if we have taken the appropriate steps and established a controlled and
stabilized approach, our problem at the point of flair is greatly
simplified. We will arrive at our round-out point in good order at the
correct altitude, airspeed and rate of descent and be well compensated for
any crosswind drift and gust factors; all will flow naturally.
As we
begin our transition from approach to flair, essentially a levelling out of
the aircraft just above the runway surface, we may also begin to reduce
power. Depending on the type of landing we are setting up for and the type
of aircraft we are flying, we may need to carry some power until or perhaps
beyond the moment when the aircraft has touched down.
It is
important to keep in mind the two main effects of reducing power: left to
its own devices, the aircraft will drop its nose and yaw to the right,
assuming we are not flying behind a Russian or English built engine that
turns in the opposite direction from North American built engines.
If you are
alert and ready to compensate for these built-in tendencies, you will not be
surprised by them or come to grief.
Initially
we gently bring the aircraft to a level or cruise-type of attitude just
above the runway surface. Using a combination of pitch, yaw, and roll
compensations as required, we will, for a brief time, simply fly the
aircraft straight and level at a very low altitude down the centre of the
landing surface giving the aircraft time to dissipate some of its kinetic
energy.
Remembering from our high school physics that kinetic energy = (M/2)V2,
where M represents the Mass of the aircraft and V represents its velocity,
we see the heavier the aircraft and the greater its speed, the more energy
we will have to dissipate for the aircraft to land. Velocity, since it
increases by its square, is a very significant factor. Another good argument
for that controlled and stabilized approach.
As the
aircraft begins to dissipate its kinetic energy, it will lose lift. One of
two things will occur: it will descend or it will slow down. It takes energy
to maintain flight.
We can
compensate for one or the other of these tendencies but not both. Our
preference at this point is to opt for slowing down; we don’t have much
altitude to give up. In order to remain in level flight, however, we must
maintain necessary lift. We can produce lift either through speed or angle
of attack. Since our speed option is rapidly diminishing and our altitude is
minimal, increasing our angle of attack is the only option open to us.
As the
aircraft slows, we will gradually and deliberately increase our angle of
attack to maintain flight. Increasing our angle of attack, as we know well,
also increases induced drag, further slowing our now very underpowered
aircraft. As long as this process is kept under control, all is well.
The two
major errors people tend to make during the flair phase of the landing
process are to either over-flair or under-flair. Over-flaring produces what
we refer to as ballooning: the aircraft turns its excess kinetic energy into
climb. This is neither desirable nor safe and must be corrected immediately.
We are low and slow. We do not want to risk a stall 10 feet above the
landing surface.
At the
first indication of ballooning, we must gently lower the nose and regain a
level flight attitude just above the landing surface. It may become
necessary, if the balloon is too great, to add some power to reduce our rate
of sink. If the balloon is at all extreme, it may be a more positive step to
abort the landing: establish the aircraft in level flight, add full power
and initiate a go-around or balked landing procedure.
The other
common error during flair is failing to level off above the runway, to
under-flair. This is hard on the undercarriage and can produce some very
exciting and expensive consequences. It is frequently the result of allowing
ourselves to visually fixate on the touchdown point losing reference to the
perspective and peripheral visual information helping us judge height and
position.
The flair
phase of landing allows us to dissipate the aircraft’s kinetic energy
sufficiently for the next phase: touchdown. Ideally, we will run out of
airspeed and altitude at just about the same moment. Correctly executed, the
flair transitions us smoothly from approach to touchdown. It is a critical
aspect of the landing process and deserves our full attention and focus.
Many students and, indeed, experienced pilots tend to rush this process.
Take your time; do it right. The aircraft will let you know when it is ready
to proceed with landing.
Notes
- 1. Hasbrook, A. Howard,
Anatomy of a Landing – Cue by Cue, Business and Commercial Aviation
Magazine, August 1971 issue, McGraw-Hill, New York – London
- Langewiesche, Wolfgang,
Stick and Rudder, McGraw – Hill Book Company, New York – London,
1972
PRINCIPAL AIR
Main Terminal Chilliwack Airport
2-46244 Airport Road, Chilliwack, B.C. V2P 1A5
Phone: (604) 795-7861 Fax: (604) 795-7867
E-mail
|
