Contents:
...Downwind Landing; ...Downwind
in a Crosswind; ...Base in a Crosswind;
...Demonstrated crosswind capability;
…Dutch roll; …Learning
the Dutch roll; ...Crosswind Landing;
...Crosswind Landing Instruction; One Wing Low Landings; …Opinions;
...Crosswind Landing Skills; ...Crosswind proficiency; …Crosswind
Capability; ...With a Crab and a
Kick; ...Landing in Turbulence;
...Unusual wind landings; ...Difficult
Wind Landings; …Rules of Thumb
for Landings; …Risks Related
to Landings; …When Things Go
Wrong; …
Downwind
Landing
The entire downwind approach, even with full flaps, is unexpectedly
flat. Flying the familiar pattern results in a go around. The
aircraft will be moved by the air mass too tight in the pattern.
Trying to adjust the approach and apparent ground speed so that
it is "normal" will not work. Further, if we are not
in the habit of making full stall landings and even if we are,
the landing roundout, flare and roll will require much more runway
length than we would ever expect. It is this unexpected distance
that often makes the inexperienced pilot try to force the airplane
to the ground before it is ready. The resulting flat or hard landing
extends the distance required even more. The controls on the ground
must be held correctly especially if there is a quartering tailwind
during rollout. If you expect to be going into a one-way airport
be sure to get some downwind practice first.
The difficulty with downwind landings is the conflict of previous
performance and perceived performance. We are used to landing
into the wind and the reversal of wind makes things happen differently.
Pilot judgment is impaired by the perplexing unfamiliar ground
speed being greater than airspeed. By failing to fly an exceptionally
extended downwind the full flaps, power off, and minimum approach
speed does not get us down. The C-150 requires at least 50% more
runway with a 10-kt tail wind added to the normal approach speed.
Busy airports frequently will maintain the use of a runway after
the winds reverse direction because of traffic or noise considerations.
Some airports have a calm-wind runway. This calm wind may exist
at ground level but not infrequency the entire approach will be
with a tail wind. The IFR straight in ILS with a tail wind may
be your only option someday. The increased ground speed caused
by the tail wind will make for a very flat approach and a long
landing roll.
While the inadvertent downwind landing may occur during near calm
conditions, it may be required at a one-way airport. This is an
airport for which there is only one landing direction regardless
of wind. Ruth, the northern most airport on the S. F. sectional
is such an airport. This landing as well as cross wind landings,
can be practiced at a non-busy tower airports.
ATC is authorized to use any runway when the 'calm wind is less
than five knots where it is operationally preferred or requested.
ATC will advise of the downwind condition. Pilot requests are
usually honored by ATC.
Downwind in
a Crosswind
The beginning of a good crosswind landing is determined in how
well the pilot maintains the downwind leg a desirable distance
from the runway. If the left pattern crab is toward the runway
then the right pattern crab must be away from the runway. The
key to avoiding any problems in the turn from base to final is
dependent upon not letting the downwind track shorten the base
leg. The decision should be to keep your downwind legs very wide
for all crosswind landings. Skill in maintaining pattern spacing
is acquired during ground reference training. A wide base lets
you adjust your turn to final if high or low.
Base in a Crosswind
Whether a crosswind adds or detracts from your base ground speed
and track, it is important that you plan accordingly. The base-to-final
turn in a crosswind requires specific procedures to allow you
to smoothly align the plane with the runway. If the cross wind
is adding to your ground speed, then the turn will have the correct
wing low and require opposite rudder to align the nose. If the
crosswind is slowing your ground speed, it will be necessary for
you to reverse the turn bank immediately on final and apply opposite
rudder for alignment. Because the turn to final in each case is
so different, it is important to practice both left and right
pattern landings in the same flight and wind conditions. Anytime
the aircraft is in a cross-control configuration on final, significant
forward yoke pressure will be required to maintain the indicated
approach speed.
Even when the base to final is properly turned for runway alignment,
there is considerable difference in how the turn concludes. Unlike
most turns that are completed with the wings level, the crosswind
landing turns from base to final are completed with a wing low
and opposite rudder to align the nose parallel with the runway.
If the base leg has a tailwind adding to your ground speed the
turn to final requires only that the opposite rudder he held for
nose alignment while the wing continues to be held low into the
wind. If the base leg has a headwind the turn to final must be
quickly reversed to the opposite bank from entry while the rudder
is depressed to keep the nose straight with the runway. The more
constant the airspeed the more consistent will be rudder pressures
and aircraft performance. Any time the aircraft is in a cross
control configuration on final, significant forward yoke pressure
will be required to maintain the correct indicated approach speed.
Demonstrated
crosswind capability
When an aircraft is certified by the FAA, it includes a demonstrated
crosswind capability. The capability is based only on the winds
available for that time and day. Some capabilities are based on
relatively light winds. This means that an average pilot with
average competence will be able to land without difficulty. This
is a very poor method of determining the flying limits of an airplane.
It is normal and students should expect to have trouble with all
the variables of airspeed, wind velocity, bank angle and rudder
application when learning crosswind landings. Of all standard
flight maneuvers the crosswind landing requires the greatest variety
of contradictory control applications. Only mastery of the Dutch
roll prepares the student for what is going to happen. The Dutch
roll removes the intellectual process from the uncoordinated used
of controls. If you must think of what to do, you will always
be behind the plane.
The crosswind slip to a landing uses the opposite rudder, as applied
to keep the aircraft centerline parallel to the runway centerline.
The opposing aileron is used to tip the wings so as to slide and
maintain the aircraft centered on the runway approach line. The
greater the crosswind component the more flaps application is
reduced.
Once the crosswind component exceeds that which was used during
the certification demonstration the pilot is advised to adjust
the use of flaps and speed to suit the conditions. Any time the
full application of the controls and increased speed is unable
to maintain directional control the go-around is the only option.
Low touchdown speed gives each knot of crosswind additional effect
so that additional aileron and rudder deflection--and more bank
angle-- is needed to get the slip angle needed to hold runway
alignment. Whatever deflection is needed on final approach is
only 2/3 of what is needed at flare and touchdown.
A student would be ill advised to self-instruct crosswind landings.
Wind gusts can occur that will make the go-around as the only
viable option. Without experience a student is apt to be too late
with too little.
Has been defined as a second order composite stability characteristic
that results for the lateral-direction cross-axis coupling of
two separate responses to a sideslip. Since there is a coupling
between the roll axis and the yaw axis is often considered as
a lateral-directional oscillation. Actually the Dutch roll is
a relatively easy to control rocking of the wings while holding
the nose straight with the rudder. Undesired, the Dutch roll is
a nuisance that can occur in turbulence or on an instrument approach.
What can create a problem is the fact that it is an uncoordinated
maneuver. You can create a Dutch roll problem just by trying to
fly with only the rudder. While trimmed for level flight, displace
the rudder and then put your feet on the floor. The aircraft will
waver back and forth and finally return to level flight. Doing
the same thing while trimmed at approach speed will aggravate
the Dutch roll and make it take longer to smooth out. Do this
again but try to use the ailerons only to hold a heading. The
adverse yaw of the down-deflected aileron will cause the aircraft
to perform Dutch rolls.
Dutch roll introduction:
Students to first plant feet on the floor. Sight a reference point,
straight ahead or a heading. Rock the wings back and forth between
about 45-deg bank left and right. Hold the nose on the reference
point or heading. No rudder. Now try it with rudder. Rock back
and forth and back and forth, rhythmically for a minute using
the rudder.
A student typically uses on the wrong rudder and wrong pressures
in the beginning. It will take a few sessions to get it right.
When the Dutch roll finally falls into place you have mastered
the basic control skill required for doing crosswind landings.
Learning
the Dutch-Roll
UNCOORDINATED FLIGHT---A NECESSARY SKILL
While the controversy continues over spin training, I feel that
a much more practical and useful flight skill is being neglected.
I write thus of the Dutch-roll. I suppose that just as much of
our aviation language originated from naval terms, the origin
of the Dutch-roll could have come from the peculiar sideways shift
of the stern of an apple-bowed caravel (Dutchman) when running
before a following sea. As the stern was lifted by the oncoming
wave it would swing to one side, the hull would roll as the swell
passed, and the stern would swing back onto the course-line as
the breaker moved under the bow and the hull rolled upright.
In an aircraft, especially those with V-tails, it is a tendency for the tail to wander off the line-of-flight far enough to generate a straightening force, but overshooting the correction only to repeat the excursion on the other side. If accompanied with a pitch variant, the tail may oscillate in a circle. The Dutch-roll in ship and aircraft is an undesirable characteristic.
The basic Dutch-roll consists of rocking the wings with the ailerons smoothly through a series of 10, 20, or 30 degree banks while keeping the nose on a point or heading with the rudder. If done while the aircraft is climbing most of the rudder application will be more or less right rudder with an occasional tap of left rudder. This does not detract from the value of the exercise.
To the student pilot, to whom the coordinated use of rudder and aileron has become a sacred ritual, the contradictory control pressures required for the Dutch-roll ranks as sheer heresy. The control pressures required equate with patting the head while rubbing the stomach. The skill acquisition compares with that of roller skating. It is best not to intellectualize it. Just do it until all by itself it seems to fall into place. Remember when you learned to skate?
Just as the four basics are skills essential in normal flight situations, so is the Dutch-roll an essential additional skill for successful crosswind landings and use of the rudder. In the off chance that the reader may be unacquainted I will endeavor to describe the maneuver and suggest an instructional sequence.
The Dutch-roll can be flown level, climb, or descent. You select a point or heading and try to keep on that heading. Beginners seem to do the series of banks too quickly. This increases the yaw effect and makes necessary abrupt usage of the rudder. At a slower pace the rudder use can be better anticipated. If the nose swings the rudder is being misused. Start over. The nose should not move during the banks. Maintain a constant airspeed. The rudder must be applied or relaxed sometimes in anticipation and at other times in conjunction with the ailerons.
A suggested instructional or practice sequence would be to use the climb time from pattern altitude to cruise altitude. This time is often under utilized and the Dutch-roll serves to clear the flight route. The student can begin with a series of rhythmical 10 degree wing movements while the instructor applies rudder to maintain heading. It is vital that airspeed be maintained relatively constant so that rudder application and effect will also be constant. Then the roles can be reversed between student and instructor. The third step would be the student performing both functions with the instructor monitoring. If, for any reason, banks and nose movements become erratic--start over. See, just as in roller skating. It seems to be best to initiate the first banking of the wings to the left followed quickly with a solid application of right rudder before the nose has a chance to swing.
The left turning-factors of the climb is a constant that requires right rudder. The banking causes yaw which is a variable depending on amount and quickness. When the bank begins toward the right the rudder pressure is gradually relaxed but not removed because of the left turning-factor and adverse yaw in climb. The banking movements must be continuously smooth and rhythmical, as in waltz time. All efforts to control heading must be done with rudder while the banks are maintained in rhythm. Rudder amounts and timing of release or application is done in anticipation of heading changes.
The student will experience extreme frustration with this exercise in the beginning. As the student becomes visually aware of the nose on the horizon and how rudder is a control he will improve. It is vital that expectations of proficiency be planned over at least five flights. If air sickness is a problem, approach the exercise in gradually extended time periods from twenty seconds to three minutes. The most common difficulties seem to be making the banks too quickly and of unequal angle, holding the yoke tightly, not making airspeed adjustments, not recognizing heading changes, belated rudder applications, and attempting to salvage a blown exercise. If the nose begins to wander, start over.
Even though we are in uncoordinated flight there is still a required coordination between foot and hand, rudder, aileron, and airspeed. Coordination, even in uncoordinated flight, is a basic skill required for slips and crosswind landings.
Now what do we get from this. We get a pilot who can enter final for a crosswind landing with one half of a Dutchroll and the visual coordination skills required to maintain runway alignment, the nose position and the airspeed. The pilot can do this with those Dutch-roll skills that enable him to anticipate rather than react. He is ahead of the plane, not behind. If, because of wind velocity and direction or control problems, the half Dutchroll cannot be held on final--GO-AROUND.
Crosswind
Landing
Everything you need to do in a crosswind is in your imagination.
The use of rudders in a crosswind just involves doing what it
takes. You make the airplane do what it is supposed to do. What
you experience is more what you think has happened and what actually
did happen. Imagine what is supposed to happen and then make it
happen.
As a student working on crosswind landings, or any landings for
that matter, you must be asking yourself an infinite variety of
questions about the process. High, low; close, far; fast, slow;
up, down, in, out; it doesn't matter you must never focus on one
item, the whole process must be put together to make the landing.
As in a poker game, each landing is a new hand that must be bet
and played with the cards you are given
The necessity for a stabilized approach even applies to crosswind
landings. You should hold the crossed controls throughout the
final approach. The crabbing approach, which requires a sudden
application of rudder and aileron during the flare, seems to pose
an unnecessary risk.
The problem of crosswind instruction is not with students; it
is with instructors. All to often I take my students up in a moderate
15-knot 60- degree crosswind for an hour. We are lonely. The FBOs
with their cadre of young instructors have flight restrictions
to protect their equipment. How is a student to learn to cope
with the adversity of a crosswind if the opportunity of exposure
is denied? A crosswind is a learning opportunity. An event to
be challenged, studied, and conquered. If the student should discover
that he is incapable of handling a specific wind, then that, too,
is a valuable lesson. We must learn our limits, how better to
learn them under experienced instruction?
I have had occasion, of late, to fly with several mid-time pilots
who show weaknesses while making crosswind landings. On each occasion,
my first query is as to whether or not they have been taught Dutch
rolls. They may have heard of the Dutch roll or may even be able
to describe it. None of these pilots admit having had instruction,
proficiency, or awareness of the Dutch roll relationship to cross
wind landings. Proficiency in the Dutch roll takes the mystery
out of how much rudder and aileron to apply for a crosswind landing.
Become sensitive to signs that will give wind direction and velocity.
Check the windsock on final.
There are two distinct cross wind landing patterns for a given
wind. Left or right patterns in less than 90 degree crosswind
affects the amount of turn required to hold runway heading on
takeoff, the turn and heading to maintain crosswind track, as
well as the amount of turn required for downwind and base legs.
The pilot must learn to take into consideration the velocity of
the crosswind as it influences the ground track of the traffic
pattern. The 90-degree crosswind does not affect track on crosswind
or base except in terms of speed. In a crosswind landing this
runway alignment is doubly important. Each turn from base to final,
left or right will require a completely different rudder/wing
low technique in a crosswind. This can best be practiced where
parallel runways exist or where left/right patterns can be flown
to the same runway. When practicing crosswind landings it is very
important that both left and right patterns be flown to teach
planning of the crosswind, downwind, and base legs as well as
turning to final with the proper wing low/rudder position. The
initial practice of runway alignment can be done in calm to slight
crosswind conditions. Later practice should be done in increasingly
strong crosswinds even to the point of requesting a crosswind
runway not currently in use.
Aircraft that are certified under FAR Part 23.233 requires the
aircraft to be safe for operations in 90-degree winds up to 0.2
Vso. Vso is the slowest speed an aircraft is controllable in landing
configuration, at approach speed, no brakes and no special pilot
skills. For a 60-knot speed with the C-150 this equates at 12
kts. These are minimums. This means that anything beyond a 12-kt.
90-degree crosswind exceeds the design expectations for an average
pilot. If during the certification trials of a given aircraft,
only ten-knot winds were available then that is the limit of the
demonstrated crosswind component. This does not appear to be a
very realistic criteria.
Crosswind Landing
Instruction
To begin with we must assume that the student pilot has flown
the pattern in such a manner as to arrive on the final approach
with appropriate flaps for wind angle and velocity, on glide slope,
and on airspeed.
The basic training exercise for the crosswind landing is the Dutch
roll. The presumption is that mastery of the Dutch roll has
prepared the pilot to keep the aircraft parallel to the runway
at all times on final, while maintaining runway alignment with
left-right side slips as required. My preference is to maintain
a constant airspeed regardless of the slip. This means that the
greater the slip the greater the forward yoke pressure.
In the ideal approach the wind would remain as a constant. This
would mean that the slip angle and required rudder would
remain constant. It doesn't happen. The wind is a constantly changing
approach factor both as to angle and velocity. This
means that the pilot must constantly adjust aileron, rudder, and
yoke to maintain a stabilized approach with constant
heading, runway alignment and airspeed. The essential skill is
the previously mentioned Dutch roll and anticipation of
changing conditions before radical adjustments are required. I
very much recommend that extended straight in approaches
as a planned training exercise to give smoothness to the control
applications.
The wind velocity usually decreases during the descent so that
less cross control application is required as the flare
approaches. The actual flare is much as with any other landing
but since generally less than full flaps will be applied greater
care must be used to avoid ballooning. At this point full attention
must be paid to prevent any sideways movement of the
aircraft. Landing gear are exceptionally strong and resilient
but they are most subject to damage when side loads are applied.
If everything goes well the touchdown is made at minimum speed
on the upwind main wheel with the nose wheel and
downwind main still flying. This configuration can be bothersome
to passengers and should be explained as normal before
the landing. The wing low need not be of concern if the aircraft
is kept going parallel to the runway centerline. As the aircraft
decelerates the yoke should be held ever more into the wind and
back. The downwind tire will touch to be followed by
the nose wheel. Use rudder as required in holding a straight course
down the runway after the first touchdown. Correctly
done you are now in the proper configuration for taxiing on the
runway.
A crossword on landing will increase stopping distance. The tire
surface contact area provides only so much friction. In a
crosswind this total friction is divided between the effect of
the crosswind creating side-load friction and the braking
friction working against the forward momentum. For this reason
expect crosswind rollouts to be longer.
One Wing
Low Landings
Half a Dutch roll is basic to all wing low/opposite rudder
crosswind landings. It is a matter of pilot judgment to decide
what to do if rudder authority is insufficient to allow the pilot
to hold the nose aligned with the runway. In my experience
I have applied full rudder and wing low and then eased off with
rudder if the situation allows. Should the rudder lack
sufficient authority, I will lower the nose or add power to the
point where full rudder application will straighten the nose.
I will increase my approach speed as needed so long as runway
length will be sufficient to let me float until this excess
speed is lost in the flare.
I have never been concerned with excess bank angle because
the closer the tip gets to the surface the greater the resistance
due to ground effect. The primary concern is to keep the nose
straight with the runway centerline. I do not believe you
can make the tip touch so long as the nose is straight. I have
landed Cessnas in 45 knot 90-degree crosswinds without
touching the tip. Once on the ground, I always hold the yoke full
over into the wind and it often seems I will catch a wingtip
but I have always backed off without touching the ground.
I have found that even at airports with multiple runways, ATC
is willing to allow those who ask to use the crosswind runway
so long as traffic conditions will allow. I have used the crosswind
runway at non-tower airports with as many as four other aircraft
in the preferred runway pattern. With proper radio procedures
they have spaced out so that my student and I have been able to
get the practice required to give the student the confidence that
was previously lacking. It is surprising how easy it is the handle
crosswinds once you have extended your personal crosswind limits
up into the 20-knot region.
Just the other day I took a student into some crosswind landings
at a non-tower airport. Student made four landings where touchdown
occurred power off and near the numbers. I did one to demonstrate
that the student was working too hard to keep runway alignment
and drift countered. The last two approaches I deliberately set
up the situation were the touchdown was half-way down the 4000'
runway abeam a small grove of trees. All at once the student's
landings became more difficult. The trees changed the previous
steady wind into a series of swirling gusts. The difference in
the landings showed that more practice is needed. There is no
time to add speed, you have to land with what you've got or go
around.
Other Opinions:
Opinion
The rate of (aileron) reduction depends on the absolute magnitude
of the crossword component and the developing forward speed.
Opinion
I have a different viewpoint. I do not want anyone that I have
taught to arrive at a destination with crosswinds that they have
not been exposed to.
Opinion
My suggestion to you is to get with your instructor on the windiest
day you can and practice x-wind takeoffs and landings to determine
what your maximum capability may be.
Crosswind Landing
Skills
Were I to have all the control I wanted in the teaching of crosswind
landings I would make the first instructional requirement to be
that they should be taught in sailplanes. The necessity fomented
by only getting one shot at a narrow runway would be sure to focus
a student pilot's attention. Ground reference maneuvers in airplanes
do not provide the realism that is required for students to sense
winds in the pattern. The crosswind landing begins on the downwind.
Only by flying the appropriate (wind corrected) downwind can the
base and final be readily adapted to the wind conditions. The
other legs of the approach only compound the problems of an inappropriate
downwind.
In very light crosswinds of 5 kts or less the use of full flaps
should not be a problem. However, I find that most students are
not able to detect, counteract, or otherwise compensate for the
subtle effects of a light crosswind. Dutch roll weakness seems
to be the culprit. I would suggest that under light wind conditions
a student should be set up on an extended final approach to do
the following. Practice side slipping the aircraft left and right
across each side of the centerline. Next sideslip to each side
while stopping momentarily on the centerline to assure that the
nose is being kept parallel and approach speed maintained. This
could be done all the way to the landing as a confidence builder.
Crosswind landings can best be practiced where parallel runways
exist or where left/right patterns can be flown to the same runway.
It is very important that both left and right patterns be flown
to teach the differences in planning for the crosswind, downwind,
base leg, and final. Skill in getting the wing low and opposite
rudder applied is related to how well Dutch rolls can be performed.
Initial practice can be with light crosswinds but true confidence
and capability requires practice in winds of 18 kts or greater.
Towers are usually obliging in the use of crosswind runways.
The velocity of winds usually decrease with altitude. This is
true even for winds below 1000'. If the indicated approach speed
is held along with power and flaps as constants in the approach,
the variable becomes rudder and ailerons. Rudder is used to hold
the nose parallel initially and varied as aileron inputs are used
to maintain runway alignment. Any change in the rudder requires
a change in the ailerons and vice versa. While this is uncoordinated
flight, there is coordination between them predicated upon keeping
the aircraft nose both straight and aligned with the runway. In
this configuration the landing touchdown will be on the upwind
wheel first, then the downwind wheel and then the nosewheel.
Every pilot flying has assumed a degree of responsibility for
his presumption of ability and skill in making crosswind landings.
As a pilot you are expected to have read and understood the significance
of the demonstrated crosswind capability of your aircraft. This
means that at the time of certification a certain velocity crosswind
existed. At this velocity an average pilot would be able to land.
Beyond that velocity you should be a better than average pilot.
Whenever you taxi, takeoff, or land in conditions that exceed
the maximum demonstrated crosswind component you become a test
pilot. FAR 91.13 applies.
Knowing when a wind exceeds your piloting capability is usually
not discovered until too late. You, as a pilot can determine the
wind by entering the wing-low opposite rudder approach early on.
If the approach cannot be stabilized on the approach then a decision
to go-around is a good one. Making the go-around decision before
the press of circumstances adds additional problems, requires
that the pilot think ahead of the airplane. An early go-around
is an indication that the pilot is ahead of the situation and
ready to select a more favorable landing situation. Turbulence
and wind shear are to be expected when winds are active.
The wing-low opposite rudder is an uncomfortable configuration
for most pilots. Being proficient in the Dutch roll makes for
greater proficiency and comfort. It is proficient in the Dutch
roll that makes getting the control input needed automatic. Only
frequent practice will maintain proficiency.
As an instructor I seek out crosswinds. I don't want a student
to be faced with wind conditions that have not been encountered
during dual flight. Each pilot will need to recognize his limits
in a particular aircraft.
The 'demonstrated' limits in the POH are not the limits of a proficient
pilot.
Crosswind proficiency
(Instructor)
Once a student has mastered the basic full flap landing and go-around
it is time to introduce the variations that will be required for
crosswind conditions. The landings will be introduced when there
is no crosswind and may be in only one turn direction. The first
landing is a no-flap power on, the second a no-flap power off
with a slip as required. The next three will be with 10, 20 and
40 degrees of flap. The idea is to develop a student's perception
of how 'high' or 'low' on approach is related to the aircraft
configuration. 60-knot airspeed is used on all approaches. Each
change in configuration requires a slightly differing round out
and flare technique.
A good crosswind flight depends on getting the desired crosswind
at a velocity up to 18 knots. The same series of landings are
discussed on the ground by walking the headings. The variations
of pattern size required by the configurations, even though 60
knots is flown throughout, is a major student learning experience.
The different configurations are flown. Instructor demonstrations
may be required to give the student a 'break'. This lesson should
remove wind limitations from the student logbook. A later short
session should include even stronger winds.
Crosswind
Capability
The maximum crosswind capability for an airplane depends on
the capability of the pilot. The POH crosswind given as "demonstrated"
is in no way related to what can be done with the airplane.
When a pilot has applied full rudder. accepted a somewhat diagonal into the wind runway alighnment, increased both power and airspeed and still cannot keep the nose aligned with the diagonal centerline it is time for a go-around. I have yet to have an airplane being held straight with the rudder to scrape a wing tip. some say it is possible but I have yet to meet such a wind.
The most likely problem making a crosswind landing is when the
winds are light and variable. A steady wind is relatively easy
to set up. The variable wind keeps changing. When you have a light
constant velocity crosswind you can set your correction all the
way down final. You don't become aware of a variable wind immediately.
After several changes in rudder and wing, you begin to appreciate
acquired skills in Dutch roll. Into the flare your control applications
become critical. Get it right or you will side-load the landing
gear. together REAL fast, that initial swerve will turn into an
pilot induced lateral oscillation that promptly ends in a ground
loop or an "off runway" excursion!
Winds normally decrease with decrease in altitude but in the flare at low airspeeds you may need far more control input than you think. Do what ever it takes. This is not because of the crosswind but because of the decrease in airspeed.
With
a Crab and a Kick (Instructor)
There are two different ways to do crosswind landings, the slip
and the crab. Both can be successful. The crab requires greater
precision, experience, and luck. The crab is a "more comfortable"
approach. The runway comes from the side and does not give the
over-the-nose perspective of most approaches. You will be able
to crab down to the runway in much more wind than you have control
power to slip-kick-land in. An incorrectly timed kick to straighten
the nose or a gust can excessively stress the side load capabilities
of the landing gear box. (The mounting brace in the fuselage.)
The experience required for such timing may be acquired too slowly
or too late for really strong wind conditions. The crab does not
handle gusty conditions well. The go around should be initiated
before the slip-kick else the rapid application of power may cause
loss of directional control.
Instructors planning to teach the crab and kick to slip method
may wish to prepare the student by practicing the slip/opposite
rudder configuration on long final approaches. The slip technique
is relatively difficult to learn to the point of mastery. This
additional practice along with Dutch rolls done on climbout provides
additional exposure.
I do not teach the 'crab' method of crosswind landings because
I feel the method offers too much potential for aircraft damage.
Landing from a side slipping approach does not require such precise
judgment and timing. In a crosswind use a power-on approach and
flaps according to wind angle and velocity. Use additional airspeed
only if needed to increase rudder power. The 1/2 Dutchroll method
keeps both the aircraft path and nose aligned with the runway.
The upwind wing is lowered to intercept and maintain the runway
path and rudder aligns the nose. This method will correct for
any wind velocity or angle up to the control limit of the rudder.
On ground contact the lowered wing and aileron position protects
against gust effects and the ailerons are correctly positioned
for taxi. Full aileron should be applied in the landing roll even
after the downwind wheel makes ground contact.
While there are still advocates (surviving) of the crab and kick
method, the tri-cycle gear aircraft lends itself to the wing low
opposite rudder slip technique. This method allows the pilot to
determine and adjust to the crosswind during descent. Constant
adjustment, similar to those used for a Dutch roll, must be made
to maintain heading and alignment with the runway. The wind is
changing constantly both as to direction and velocity during descent
so the timing of the kick must be just right.
Landing
in Turbulence
Don't use flaps. This will keep the nose higher and closer
to the proper landing attitude. Touchdown speed may tend higher
as the wind angle approaches 90-degrees. This should be recognized
and avoided since a 90- degree crosswind makes airspeed the same
as ground speed. Any increase in ground contact speed will multiply
any side load effects. Failure to correct for a crosswind will
cause damaging sideloads and directional control problems.
The potential sideloads of a crosswind increases as the square
of the velocity. Even at low wind speeds the effects can be dramatic.
2 kt. wind 2x2 = factor of 4 sideload; 3 kt. wind 3x3 = factor
of 9 sideload; 4 kt wind 4x4 = factor of 16 sideload. Double the
number gives quadruple the sideload.
Keep power on during the approach and add one-half of the gust-factor
to your approach speed. Do not seek a full stall landing. Fly
the aircraft on to the runway, pull the power off and don't get
any more weight on the nosewheel than may be required for steering.
Remove any flaps. Permitting weight to be applied to the nosewheel
will transfer weight from the main landing gear. Too much of such
a transfer will cause the main wheels to lift off and lose traction.
You are now steering a wheelbarrow with the rudder. Your safest
option is to go-around. Salvaging a wheelbarrowing landing is
not for the faint of heart.
Unusual wind
landings
Last week, as I walked up to the plane, I momentarily stopped
and felt the wind. It was very light but could be perceived as
a tail wind for the noise abatement runway currently in use. I
had my student, sitting in the plane, get out and asked him to
feel the wind. What followed was an analysis of what happens when
a wind is classified as "calm". Even more importantly,
we covered all the effects for the even greater probability that
the wind would be "light and variable". We did some
watching of aircraft making their landings. Landings were consistently
long on the 5000' runway. Also, the landings were usually off
to the side of the centerline.
On average, landings are made into runways with the twelve-knot
relatively constant velocity and direction winds. Most of our
practice and landings are into such winds plus or minus a knot
or two. This experience has taught us to make the adjustments
to the pattern and aircraft configuration required producing a
satisfactory landing. "Calm winds" do not provide the
clues the inexperienced pilot has come to expect. The light tail
wind will increase the ground speed and shallow the approach angle.
The usual changes in flaps, power, and airspeed fail to produce
the desired results. This is caused by the fact that, while the
tail wind may exist from 600 feet down to 100 feet the winds higher
and lower will be from different directions and velocities. Even
the tail wind will vary in velocity on final. The momentary truly
calm wind compounds the difficulties.
The solution I offered my student was to extend the down wind
leg of the pattern by twenty to thirty seconds any time the ATIS,
wind sock, or AWOS indicates a calm wind condition. This adjustment
allowed for the more shallow approach angle caused by the increased
ground speed. The student was on a good approach but a new "calm
wind" problem arose. In the flare the aircraft would begin
a barely perceptible drift off the center line.
It seems that the intensity of the landing itself often so focuses
the attention of the student that he/she is completely unaware
of drift unless it is either pronounced or occurring just before
touchdown. The likelihood or probability of this condition occurring
must be pre-registered into the mind of the pilot any time the
"calm" condition exists. With the runway out of sight
in a proper flare the pilot must get his clues from the peripheral
vision and the horizon. This takes both practice and experience
especially in calm conditions. A failure to correct even the slightest
side load on the landing gear is potentially very harmful to the
aircraft since this is the weakest area of landing gear geometry.
The instructor who does not foresee this area of landing difficulty
is not properly anticipating an area of difficulty.
A few day prior to this flight another student and I had winds
at 23 knots with higher gusts 40 degrees off the runway heading.
Once again I proceeded to talk and walk through the headings for
both left and right traffic that would produce an appropriate
pattern. Just to get into the plane and start doing landings in
these conditions would have been most inappropriate. We were transitioning
the student from a C-150 to a C-172. This was his third C-172
flight but his first since getting his license.
In the pattern walk through, I gave the student the needed opportunity
to see that some operational adjustments would be required. The
initial takeoff would cause us to gain altitude over less distance
so that our crosswind would need to be flown angled well into
the wind and extended somewhat to create a wider downwind. The
turn downwind would need to be angled away from the runway since
it was necessary to fly a somewhat wider downwind leg both because
of being in right traffic and because the wind direction would
produce a an effectively shorter base leg due to a higher ground
speed. The power reduction would begin before the numbers and
even more angle into the wind would be taken to counter the increased
wind effect at a slower airspeed. The wider downwind would give
us a base leg sufficiently long to allow adjustments in the length
and height of our final approach. The instructional emphasis here
is that the pilot's control over the final approach must begin
on the downwind leg if not sooner.
Under these or similar conditions the landing must be considered
an option not a necessity. The go-around is the first choice option
if the stabilized final approach cannot be established.
Flying the same runway in left hand traffic in the same wind conditions
requires the pilot to make a shorter crosswind to help counter
the wind's efforts to drift the aircraft away from the runway.
The downwind leg must be angled toward the runway. The base leg
again must be sufficient to allow adjustments to the height and
length of the final approach course.
The instructional process for landings is not complete unless
it exposes the student to the wind conditions described above.
The opportunity to fly both left and right patterns in the same
crosswind conditions is essential. Variety of pattern and conditions
can be created by going to controlled airports with multiple runways.
ATC will honor requests for crosswind runways and different patterns
when traffic conditions allow. Changing the time of day is a good
way to obtain varied wind velocity.
Training and recurrent training will not provide competence unless
the pilot puts the training to work as a foundation for building
experience. Training should not be confused with competence. Training
is but a path for the pilot to follow to achieve competence. Do
not believe that training will do the job for you that more flying
will. Training does not lead to competence. Competence comes mostly
from experience gained in flying.
Difficult
Wind Landings
I have read that world-wide the average wind has a velocity of
about twelve knots. At each end of this reference are wind extremes
that can and do cause pilots pattern and landing difficulties.
One extreme the strong winds are expected while the other extreme,
the so called calm wind, has unexpected capabilities. A student
should be exposed early to runways of varied widths and lengths
in both left and right patterns Each of these extremes offer specific
problems that can be solved only by a varied exposure. Once exposed
a pilot will better avoid problems by using the skills of anticipation
he has acquired.
Last week, as I walked up to the plane, I momentarily stopped and felt the wind. It was very light but could be perceived as a tail-wind for the noise abatement runway currently in use. I had my student, sitting in the plane, get out and asked him to feel the wind. What followed was an analysis of what happens when a wind is classified as "calm". Even more importantly, we covered all the effects for the even greater probability that the wind would be "light and variable". We did some watching of aircraft making their landings. Landings were consistently long on the 5000' runway. Also, the landings were usually off to the side of the center line.
On average, landings are made into runways with the twelve knot relatively constant velocity and direction winds. Most of our practice and landings are into such winds plus or minus a knot or two. This experience has taught us to make the adjustments to the pattern and aircraft configuration required to produce a satisfactory landing. "Calm winds" do not provide the clues the inexperienced pilot has come to expect.
The light tail wind will increase the ground speed and shallow the approach angle. The usual changes in flaps, power, and airspeed fail to produce the desired results. This is caused by the fact that, while the tail wind may exist from 600 feet down to 100 feet the winds higher and lower will be from different directions and velocities. Even the tail wind will vary in velocity on final. The momentary truly calm wind compounds the difficulties.
The solution I offered my student was to extend the down wind leg of the pattern by twenty to thirty seconds any time the ATIS, wind sock, or AWOS indicates a calm wind condition. This adjustment allowed for the more shallow approach angle caused by the increased ground speed. The student was on a good approach but a new "calm wind" problem arose. In the flare the aircraft would begin a barely perceptible drift off the center line.
It seems that the intensity of the landing itself often so focuses the attention of the student that he/she is completely unaware of drift unless it is either pronounced or occurring just before touchdown. The likelihood or probability of this condition occurring must be pre-registered into the mind of the pilot any time the "calm" condition exists. With the runway out of sight in a proper flare the pilot must get his clues from the peripheral vision and the horizon. This takes both practice and experience especially in calm conditions. A failure to correct even the slightest side load on the landing gear is potentially very harmful to the aircraft since this is the weakest area of landing gear geometry. The instructor who does not foresee this area of landing difficulty is not properly anticipating an area of difficulty.
A few day prior to this flight another student and I had winds at 23 knots with higher gusts 40 degrees off the runway heading. Once again I proceeded to talk and walk through the headings for both left and right traffic that would produce an appropriate pattern. Just to get into the plane and start doing landings in these conditions would have been most inappropriate. We were transitioning the student from a C-150 to a C-172. This was his third C-172 flight but his first since getting his license.
In the pattern walk through, I gave the student the needed opportunity to see that some operational adjustments would be required. The initial takeoff would cause us to gain altitude over less distance so that our crosswind would need to be flown angled well into the wind and extended somewhat to create a wider downwind. The turn downwind would need to be angled away from the runway since it was necessary to fly a somewhat wider downwind leg both because of being in right traffic and because the wind direction would produce a an effectively shorter base leg due to a higher ground speed. The power reduction would begin before the numbers and even more angle into the wind would be taken to counter the increased wind effect at a slower airspeed. The wider downwind would give us a base leg sufficiently long to allow adjustments in the length and height of our final approach. The instructional emphasis here is that the pilot's control over the final approach must begin on the downwind leg if not sooner.
Under these or similar conditions the landing must be considered an option not a necessity. The go-around is the first choice option if the stabilized final approach cannot be established. Flying the same runway in left hand traffic in the same wind conditions requires the pilot to make a shorter crosswind to help counter the wind's efforts to drift the aircraft away from the runway. The downwind leg must be angled toward the runway. The base leg again must be sufficient to allow adjustments to the height and length of the final approach course.
The instructional process for landings is not complete unless it exposes the student to the wind conditions described above. The opportunity to fly both left and right patterns in the same crosswind conditions is essential. Variety of pattern and conditions can be created by going to controlled airports with multiple runways. ATC will honor requests for crosswind runways and different patterns when traffic conditions allow. Changing the time of day is a good way to obtain varied wind velocity.
Rules
of Thumb for Landings
1. Downwind speed is at top of white arc.
2. Reduce power abeam numbers
3. 1.3 of Vso on final.
4. 1/2 gust speed to Vso
5. Flaps to increase rate of descent requires trim change.
6. Reduce power after desired flaps to increase rate of descent.
7. Use 45-degree key position. (Conflict between official FAA
and experts.)
9. Add power flattens slope; reduce power increases slope
10. A constant slope requires relative coordination of pitch and
power.
11. The landing variables should be only wind and configuration.
12. Never fly below pre-selected airspeeds and altitudes.
13. Full flap landings are normal.
14. Don't add flaps below 200' AGL; Don't take off flaps on final.
15. Trim for every change of configuration and power.
Risks
Related to Landings
1.Undershoots have more serious accidents than overshoots.
2. Full power is best undershoot option.
3. Frequent pilot problem is stretching glide without use of full
power.
4. Aiming (judgment) ability is best from a steep approach
When
Things GoWrong
1. The go-around is the first and best option.
2. Trim for a constant airspeed.
3. Let the airplane land itself; don't force it.
4. Salvaging a landing is more luck than skill.
5. Excess airspeed creates problems
6. Directional control problems arise from premature touchdown.
7. Anticipation is an acquired skill honed by practice.
8. Slow down straight-ahead, not in a turn.
9. Practice yoke position skills in all winds.
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