Page 3.28 (6,824)
Ground-Reference
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Contents:
Introduction to Ground Reference;
...Why Ground Reference?; ...Ground
Reference; ...Wind and Groundspeed; ...Thinking Through Patterns; ...Turns
About a Point;
Cheating Your
Way to a Circle;
Spirals about
a Point;
Pylon, on a point
and about a point turns; ...Course Reversal;
...Rectangular Patterns; ...S-Turns;
...Eights; ...River Flying
with Steep Turns; ...Spiral
Descents;
Airspeed
Lesson;
Introduction to
Ground Reference
During the time that I am practicing flap descents and go
arounds I try to make at least one descent over a gently curved
channel or road that heads back home. I try to select one that
will not require steep turns. Flying into the wind reduces the
ground speed and required bank. For the last 'go around' I assign
a recovery altitude of 700 or 800'. I direct the student to follow
the road. He soon finds that the nose of the aircraft is an obstacle.
He must sight ahead and alongside the path desired to select
points of reference. He must anticipate the wind's effect in
turns and straight-a-ways. He must keep his eyes outside the
aircraft with only occasional referral to the altimeter. This
is just a brief introduction but will focus the student's attention
when doing the assigned reading about ground reference. Point
out errors of tracking and altitude but not critically. Help
the student locate rectangles for later use, and possible reference
points as to compliance to the FARs regarding distance from persons
or habitation.
To most efficiently use the flight time to this ground reference
lesson I will climb to altitude en route. I do this so that we
can practice power-off emergencies or descending spirals when
we arrive at the ground reference area. Partial power should
be applied during extended descents to prevent over-cooling.
You could end up with an actual failure. During these descents
help the student select ground reference patterns to be used.
Once at a practice altitude the ground reference maneuvers are
judged by smoothness, symmetry, and constant altitude.
Ground Reference
--Skill in performing ground reference is essential to airport
flying
--Be able to describe the complexities of ground reference maneuvers
before and during the performance.
--The PTS requires ground reference maneuvers and explanation
as to 'why' you do what you do
--Pilot should be able to relate how ground maneuvers are related
to specific flight conditions
--The IFR circle to land instrument requirement is related to
turns about a circle.
--The pilot must be able to demonstrate and explain how the wind
is influencing the ground pattern
--Ground reference requirements are 100 feet of altitude and
10 knots of airspeed.
--Division of attention inside and outside the aircraft are expected
of the pilot during all maneuvers
--The ground track requires constant consideration of effective
drift caused by wind velocity and direction
--A traffic watch at all times is a requirement. Demonstrate
by obvious head movement and remarks
--The pilot must know the latest changes and version expected
by the current PTS and how to perform
--The Airplane Flying Handbook (FAA-H-8083) and the PTS define
how to perform maneuvers
--For example the entry and exit from the rectangular pattern
are related to acceptable pattern entries
--The use of a variable bank is used to correct drift in a turn
--Know how to find and select suitable practice area.
--Know the difference between private pilot and commercial maneuvers
Why Ground
Reference?
One of the weakest parts of flight instruction is the failure
of the instructor to let the student know the 'why' of some of
the maneuvers as they relate to actual flight operations. Ground
reference is but one of these areas of weakness. Every ground
reference maneuver has the potential of being applied in a real
situation in the vicinity of an airport. We perform the four
basics close to the ground so that the student can become familiar
with the visual effects caused by ground movement under the aircraft.
Again, this perception is part of the approach to landing. The
apex of all ground reference maneuvers is the landing.
Flying relatively close to the ground greatly reduces the options
you have in event of an emergency. It's not all bad since in
case of a fire you can get to the ground more quickly. Select
your area for ground reference in a sparsely inhabited area with
plenty of emergency fields. At altitude we have always cleared
prior to every turn. There is no reason not to clear for ground
reference turns and every reason to continue what should be an
ongoing habit. Once you have cleared, look over the nose during
the turn.
As with airports you are learning to divide your attention between
the ground and the airplane while maintaining control. If you
do not properly divide your attention you will have difficulty
maintaining a constant altitude and the desired ground track.
At 4500' a hundred-foot altitude deviation is not as significant
as it is at 500'. As changes in altitude and flight path occur
you will be making cockpit adjustments using the division of
attention skills required close to the ground. Ground reference
maneuvers are performed to increase your comfort level with ground
proximity before you begin intensive training with landings.
Any inability to understand and perform ground reference will
appear again during the instructional phase on landings. Winds
are never, but never, what ATC says they are or will be. The
performance of the airplane in relation to the ground track and
speed tells you the wind. When the airplane does not point where
it is going, it is because of the wind. When the ground speed
on a stabilized approach (correct airspeed) is seemingly too
fast or slow, high or low, it is because of the wind. You must
learn to fly airspeeds during landing approaches and interpret
any variations in pattern and approach angle as due to wind.
When you have soloed and have an opportunity to practice ground
reference on you own you enter a new world of practice. Only
practice of the right kind will lead you beyond rote performance
to competence and finally to confidence. You may recognize that
you are having difficulty, and you may not. (Agnosia: You don't
know what you don't know) Contact the instructor and talk/walk
through the maneuver to make sure you understand the mechanics
involved. This may solve the problem, but if it doesn't, a flight
lesson is going to be the most economic solution. There is nothing
worse you can do in flying than practicing a procedure incorrectly.
Cross-country flying not so apparently utilizes ground reference
skills To fly a given course in any wind you will be required
to make heading adjustments and bank adjustments. The higher
altitudes of cross country make ground track adjustments more
difficult to determine. The more readily you can make heading
corrections for a desired ground track the more efficient will
be your cross-country flying. Some examiners hold a pilot to
1/8 mile of his selected course. ( Good reason to make a 270
takeoff departure. This way you can start your time and course
directly over the airport.
Ground Reference
More often than not ground reference is taught as though it were
the end itself and not a tool for use. We are not trying to teach
how to buzz your friend's front yard. The purpose of ground reference
training is to be able to control the aircraft in coordinated
flight while dividing attention between aircraft control, altitude,
and the ground track. The application of ground reference skills
and perceptions enable the pilot to safely maneuver and fly a
selected ground track while landing. The key to landing is getting
the aircraft configured, keeping visual track with both headings
and reference points, while making wind corrections. Being able
to fly an accurate ground track and altitude about an airport
in a strong wind is an essential skill. As a preliminary exercise,
the patterns can be done by driving around light poles or making
patterns on a large parking lot.
Due to wind, where the nose of the airplane points is not, necessarily,
where it goes. When wind velocities permit a demonstration of
how an airplane is moved by the wind can be done by holding a
360-degree; turn in a 30-degree; bank and noting that you do
not make a circle over the ground but are moved by the wind into
an ellipse. Banks used during ground reference are not all or
nothing. Banks should be smoothly and continuously entered and
removed. Aileron pressure must continuously be both held into
the bank or against the bank any time it leaves 30-degrees. Coordinated
rudder either in anticipation or application is a must. As the
lessons proceed we will devote ever more attention outside the
aircraft. Rectangles require about a 50-50 split. S-turns about
80-20. Eights on pylons for the commercial require near total
outside attention.
When you make a turn that is going to be affected by the wind,
and they all are, you are going to vary your roll rate and bank
angle. How fast and how much takes practice. This practice is
best noted close to the ground. Since entries are usually with
the wind behind you, you must be quicker into the bank and perhaps
with greater angle. Ground track is determined by ground speed
and you have the wind adding to your airspeed. You must get around
further and faster, hence you begin sooner, react more quickly
and bank more. Failure to do so will bend your path around the
turn and require additional corrections further on.
When you are making your turn into a headwind you will again
vary your roll rate and bank angle. This time you will begin
later, react more slowly, and use less bank angle. Because of
the wind you will be flying with a lower ground speed so everything
happens more slowly.
Ground proximity flying creates problems more psychological than
real. All aircraft controls function the same but the ground
movement gives an impression of speed not available at altitude.
This impression is sometimes a deceptive illusion. One real hazard
is a bird. At ground reference altitudes the possibility of a
bird strike is greatly increased. The pilot should become aware
of the seasonal migratory flight of birds and of their presence.
A bird instinctively reacts to an airplane as a 'hawk'. It will
dive. The pilot's best reaction is to climb in the presence of
birds. A defense is to fly with the landing light on. Birds will
react to the light before reacting to the airplane. There is
no practical need to do any ground reference below 300' and during
duck hunting season 500' should be a minimum. 700' is a good
student minimum. There will be little benefit if ground reference
is practiced at altitudes over 1000'.
I suggest that all ground reference maneuvers be performed in
a C-150 at full cruise. This reduces the potential for an inadvertent
stall. The student must be told of any local obstructions such
as poles or wires. A minimum altitude should be assigned for
solo practice. Simulated emergencies or landings should never
be attempted or practiced by the solo student. However, the student
should be made aware of every potential safe landing space in
the practice area in case of an actual emergency. Simulated emergencies
should be experienced during ground reference training.
The student must learn to look for and find wind direction and
velocity indicators. Waves, smoke, tractor dust, windmills, even
the way heard animals face can be indicative of wind direction.
Wind becomes a variable factor which must be anticipated and
estimated to secure a desired ground track. Wind strength normally
varies with altitude, becoming less as altitude decreases. Turbulence,
if encountered, should be introduced gradually both as to duration
and violence.
The FAR's relative to low level operations and altitudes are
covered. Requirements are 500' clear of any person or residence
and always able to make a safe landing without injury to persons
or property. The last part of the FAR makes possible simulated
emergencies from ground reference altitudes as long as a safe
landing area is available. With the mastery of the 'go around'
the student is ready for the low level situations that utilize
that particular skill.
An area with curved roads, rectangles, and straight lines that
is further away may be more effective for teaching. There are
many skills to teach during en route flying. The instructor must
know about any obstructions, wires or other hazards. It is seldom
possible to find exactly the size and shape pattern required.
Be prepared to adapt. The instructor should have several different
practice areas. This is because on a given day you want to have
the best possible wind direction for doing the patterns. Calm
morning winds are best for the introductory ground reference
flight but the stronger afternoon winds are best for student
pilot recognition of the wind effects.
The only real difference between ground reference and other flying
is the difference, caused by wind, between your ground track
and your heading is more apparent. In a wind your ground speed
and track will result from the sum of the vectors with respect
to the ground. First, you must determine the wind using whatever
ground source is available. Second, you must make a decision
as to how much "wind correction" you will apply. Third,
you compare your ground track with the one you want. Fourth,
you make a series of changes in one and two, to get the three
you want. Finding the "drift" is a matter of training
your eye to differentiate between where you are heading and where
you are going.
Wind and Groundspeed
Turning as low levels from a crosswind path to a downwind
path can be hazardous. It leads to the terrible downwind turn
stall accident. When the aircraft turns from a crosswind to a
downwind direction at low altitudes, all at once the ground seems
to go by much faster. In actuality, it is, but the reaction to
the sensation-illusion is that the airspeed has changed as well.
It has not and should not. The wind speed added to your airspeed
has caused an increase in your ground speed. Close to the ground
fly the airspeed not the ground speed. To allow for student errors
in this regard all ground reference should be flown a cruise
power in trainers. The downwind turn illusion will be exacerbated
if the pilot has developed a (bad) habit of trying to look around
the cockpit window post during the turn. (See material on peripheral
vision.)
As a private pilot you are expected to perform a turn about a
point. This means a circle at a constant altitude, of a constant
radius with ground speed a variable as affected by the wind.
As a commercial pilot you are expected to do a turn on a point.
The turn on a point has a constant radius but you are expected
to keep the wing tip on the point while flying the circle. This
can only be done if you fly a constant ground speed. You should
know the difference between the two.
Every ground speed has a critical altitude at which a given radius
circle will allow the pilot to keep the wingtip on a point. As
the circle is flown the wind affects the ground speed differently
at every point. To keep the tip on the point the pilot must vary
his altitude. Changing altitude will vary the ground speed. Enter
a slight dive when the point moves ahead of the wingtip (tailwind
component) and a slight climb when the point moves behind the
wingtip.
Practicing turns on a point at about 640' in a C-150 will give
you an idea of how the wind affects ground speed. With this knowledge
you will be better prepared to cope with the sensations present
in the downwind turn. The best defense is to fly a wide downwind
if the wind direction is forcing you toward the runway. When
you slow the aircraft on the downwind add some more wind correction.
Thinking Through Patterns
Depending on the student or airport weather conditions I
will use paper diagrams and walk through the patterns on the
ramp. I will illustrate turns about a point, rectangular patterns,
course reversals, 8's, and S-turns. I will explain the ground
track as flown in calm conditions in both left and right turns
as well as though in a strong wind with steep and shallow banks
and crab angle. All closed patterns will be initiated in left
turns with right turns to follow.
Once I have covered the turns about a point in both left and
right turns by both diagram and a walk through with course reversal,
I will diagram a rectangle. The bank required throughout each
of the four corners in left and right turns will be the same
as the banks required in the four quadrants of the circles. The
only difference is that the crab angle along the crosswind straight
legs of the rectangle will be held corner to corner. This will
be the same crab angle held at top and bottom of the circle.
From the diagram I will go to a walk through with emphasis upon
entry and exit from each corner. The paper diagram will indicate
the crab positions of the nose best. The walk through with arms
extended for bank will best indicate the bank required to adjust
for ground speed changes due to wind.
It is best that the first full ground reference lesson of the
required patterns be in calm winds. I find that calm winds are
more likely in the early morning. At least one full session should
be in flying the patterns under winds of 15 knots or greater.
Given the choice, I find that calm wind instruction is best in
the morning with stronger winds occurring later.
Turns About a Point
Some students do better if the point is selected at the intersection
of to right angle roads. This, instead of a lone tree helps maintain
orientation. It is important that the student not try to see
under a wing or around the windshield to see the point. The student
must learn to give the wing a quick flip for a look and then
put the wing back down for the turn. Keeping the circle with
a 1/4 mile radius works well.
I help the student select a point and plan the downwind entry.
Water is a good way to tell if any wind exists. I suggest to
him that it is easiest to stay a constant distance by selecting
points to make the desired circle. In the beginning I help with
altitude problems but otherwise let the first left turn or two
go by without comment. Turns to the left are easier because of
pilot position.
Draw your own diagram using the words.
Left turns about a point entry
Shallow banks going upwind
Steep banks going downwind
Aircraft headings to make circle instead of ellipse.
We always (New exception is now rectangles that are entered on
45) try to enter ground reference maneuvers on a downwind leg
since the first turn will have the fastest roll rate and steepest
angle. If you do not bank quickly and steeply for the fastest
rate of turn the wind will extend your flight path out of the
desired pattern. Going upwind, the opposite concerns exist, do
not hurry either the roll rate or the angle of the bank. You
must fly into the wind to counter its effort to keep you inside
the desired turn radius. The intent is to keep a constant-altitude,
quarter-mile circle. It helps if you can select radii points
that form the circle.
With a wind, the first turn will require more than a 90-degree
angle of turn. The angle beyond 90-degrees is used to set up
the crab required by the crosswind. The upwind turn will be gradually
decreased so that when directly upwind the wings will be most
nearly level. This is where the ground speed is slowest. The
bank is gradually increased but crab must be held into the crosswind
to keep the circle from flattening on the top. Once across the
top of the circle, the bank must be gradually increased to make
the circle conform to the added ground speed caused by the tail
wind. The steepest bank is held when we are directly downwind.
All banks are gradually increased and gradually decreased.
Often the student will try to look under or around the wing while
in the turn. Any such tilting or twisting of the head may disrupt
the fluids in the inner ear and often affect altitude control.
I will suggest that a quick flip of the yoke to momentarily raise
the wing is a better way to stay oriented. Once we have flown
left turns we must reverse to fly right turns.
Turns about a point have an airspeed and altitude combination
that keeps the wing tip on the point. In this situation the turn
about a point becomes a turn on a point. The difference is one
of focus. The turn about a point is at a constant altitude while
the turn on a point is made at a constant ground speed.
In a dead calm condition both turns can be the same only if the
pivotal groundspeed and altitude are matched. A between the wingtips
should intersect the desired ground point and stay there throughout
the 360 turn. A coordinated turn will balance all the factors
of speed, angle of bank, radius of turn and altitude. At a constant
ground speed there is an altitude that keeps the sight angle
on the point. If the point moves forward or back because of wind
variations, then the altitude becomes the variable to modify
the ground speed. Any change of radius will require that the
angle of bank be modified.
Chart of ground speed in knots and altitude in feet AGL for Turns
On A Point. (Commercial Maneuver)
70 kt 433 ft
80 ---565
90 ---716
100 --883
The turn about a point can occur in tower controlled situations
as when ATC might require a 360 on downwind or as in a SVFR arrival
clearance which might require reporting over a specific checkpoint
while remaining clear of the airport Class D surface area. The
turn about a point should be basic to many uncontrolled airport
arrivals which require circling over the field at twice pattern
altitude while determining active runway and traffic patterns.
There are two different kinds of turns related to a point. The
private level is 'turns about a point'. in this instance the
turns are to be constant in radius. In this case you can visualize
points at a constant distance from the point and use these to
fly your circle. Wind affects your ability to maintain this circle.
The first lesson is best done in a calm wind. Subsequent flights
require constant adjustment of bank to maintain your wind correction
for flying the circle.
The commercial level is a turn on a point'. The
turn on a point requires that you fly around the point with a
constant ground speed. To fly this constant ground speed you
must dive lower in a head wind and climb in a tailwind. The C-150
has a critical pivot altitude of about 620 feet. This means that
in calm conditions you can fly a turn on a point which keeps
the wing tip on that point. You know where you are flying too
fast, slow, or just right by the tip position relative to the
point. Every plane will have a different critical altitude at
any given speed. Find the critical altitude for the speed you
select and then vary your altitude to keep the tip on your selected
point. Climb if the point falls behind the tip and dive if the
point gets ahead of the tip. How much you vary your altitude
will depend on wind velocity.
Turns around a point
--Selection of altitude
--Speed from approach to cruise
--Entry from downwind with maximum bank
--Angle of bank from 30 to 45
--Angle of bank to vary with ground speed
Cheating
Your Way to a Circle
Turns about a point are constant radius, constant airspeed, and
constant *altitude* maneuvers. It's the commercial 8-s on pylons
that are changing altitude. The initial bank for the downwind
entry of a turn about a point is a maximum of 45-degrees, the
ideal distance away will be the same as you height above the
ground. Turns about a point are the most difficult student maneuver
because of the precision required and the division of attention
needed. Set up your entry for airspeed, altitude and trim before
beginning it and fly it looking mostly out the window.
If you are having difficulty maintaining altitude, you might
try covering the altimeter. This requires that maximum attention
be paid to the nose pitch attitude. Remember that you must understand
the theory of the maneuver that the steepest bank on entry is
followed by varying bank and crab depending on wind direction
and velocity.
Visualize the ground track that will give you your selected radius.
Pick points on the ground that give you a predetermined radius
circle about the center and adjust to fly over these points.
It is just like connecting the dots of a drawing to make a circle.
Spirals
Around a Point
--Start at least at 3000' AGL
--Use constant approach to landing speed
--Expect a wind shift during descent
--Use 90 degree arc checkpoints
--Works great using ADF around a radio tower
Pylon,
on a point and about a point turns
In turns on a pylon, altitude, airspeed, bank angle, and
distance from the pylon all change throughout the maneuver. In
turns about a point, altitude and airspeed are supposed to remain
constant. It requires sometimes steep turns at low altitude,
keeping the projected line of the wing through the pivot point,
and maintaining coordination through the varied airspeed.that
occurs with changes of altitude.
The two maneuvers converge when there is no wind, but the whole
point of turns about a point is to practice and demonstrate using
different bank angles to correct for wind during a turn.
Course Reversal
The course reversal is a new addition to the Private Pilot
Practical Test standards. After the completion of a ground reference
pattern in one direction it is desirable to do the pattern in
the opposite direction. A pilot must be able to maneuver equally
well in either direction. The course reversal is the most efficient
way to do this. I have found that it is best accomplished by
using the heading indicator and some indicator for wind direction.
The course reversal can be performed at any degree of bank as
long as the bank is constant throughout the reversal.
Initially we will fly upwind beyond the ground pattern for about
one minute. For instance, if we have flown a heading such as
030 (Headings are always said as three digits.) At one minute
we will make a left/right 90- degree turn at 30 degrees of bank.
90 degrees from 030 will be either 300 to the left or 120 to
the right. At the 90-degree point reverse the bank for a turn
of 270 degrees in the opposite direction. Come out of this turn
when on the downwind heading. This heading, originally to our
rear, is 210 degrees.
210 degrees will be our final downwind heading taking us into
the previous ground reference maneuver in the opposite direction.
In a no wind condition we should be tracking back over our original
route regardless of direction. If the maneuver is initiated directly
up wind then the completed course reversal should be downwind
over the reverse course. The accuracy of the reversal is directly
related to how well the headings correspond to wind direction.
All banks are at the same angle.
The aircraft should now be entering downwind to the left of the
original point. Abeam the point the right turn is commenced.
If there is a wind this will be the steepest turn. For the student
the right turns are more difficult because the point must be
viewed across the cockpit. If the circle is made too small the
point becomes even more difficult to see. Since there are a number
of other figures to fly, only two or three full circles should
be flown.
To change direction of turns about the point a course reversal
is required. A course reversal is a 90-degree constant angle
bank in one direction followed by a 270-degree constant angle
bank in the other. For best use of space begin the reversal about
one minute flight time upwind of the pattern.
Exit is same line as
entry from
pattern
area
The course reversal procedure in ground reference is used in
uncontrolled airport arrivals as part of the 45-degree entry.
This can be part of a no radio (NORDO) arrival procedure as when
landing at an airport with a tower. It is used as a (not-recommended
by FAA) procedure turn maneuver and can be used to enter traditional
teardrop and parallel entry holding patterns in instrument flying.
Rectangular Patterns
In the latest PTS the rectangular pattern entry has been revised.
You are expected to enter on a 45-degree entry to the downwind
as though for landing. You can expect to be required to fly two
rectangles in each turning direction.. There are various ways
to get the aircraft going in the other direction from a 45-degree
entry. I tend to believe that it can be done by using the same
downwind turn entry point as you used making the expected left
turns. To do this would require that on your second complete
left circuit you would go outbound at right angles to your original
entry. You would proceed outbound, perform a course reversal
and go around twice in right turns. This process is not difficult
to understand when done by diagram.
Under calm conditions almost any rectangle can be used. If there
is a wind, the longest leg of the rectangles should be planned
to be with the wind. The less wind there is the lower the altitude
flown so wind effect and crab angle is more discernible. This
gives greater practice in selecting the crab angle needed to
hold a given ground track. The ground track should held a constant
distance outside the rectangle sides and around the corners.
700 feet is considered a good altitude.
Usually only a couple of left turn rectangles are needed before
doing a course reversal and entering two or more right turns.
It is again important to do as many left turns as right turns.
In the beginning accept some variation of altitude and tracking
distance. On the second and any subsequent lessons be very specific
and critical of variations. Do this because ground reference
is one of the skill lessons that require mastery. Mastery will
allow the pilot to maneuver about an airport pattern on track
and at altitude. This skill must exist to allow sufficient intellectual
energy left over for radio and reconfiguration of the aircraft
for landing.
The rectangular pattern should be flown as though the runway
is parallel with the opposite side of the field. In calm winds
heading and course are the same. It is in crosswinds where we
use the ground reference skills of heading/course differences
to make a desired ground track. The ideal of flying a pattern
is that it be kept rectangular and tight to the airport. Properly
flown the airport traffic pattern provides maximum safe separation
of aircraft in the pattern, arriving aircraft and departing aircraft.
The corners of a ground reference rectangle exactly conform to
the four wind quadrants of the ground reference circle. The execution
of the downwind and upwind turns are performed exactly the same
for the rectangle as for the circle. Downwind straight legs will
have crab angles between ground track (course) and heading to
compensate for wind effect.
Rectangular patterns are flown to the outside of a selected rectangle
so as to give smooth turns at the corners. For best wind correction
practice make the long side of the rectangle 90 degrees to the
wind.
course reversal
entry direction
wind wind
correcting
headings
It is important that the student be aware that flying the rectangular
pattern has a direct relationship with the typical traffic pattern
scenario. A low time pilot in the low and relatively slow pattern
speed is more likely to be turning final too late. The bank angle
seems steeper because the turn radius is tighter at slow speed.
When the final approach line is overshot, rather than make the
apparently steep turn even more so, the pilot hastens the turn
with rudder. This rudder application while increasing the rate
of turn will cause the nose to drop. The back pressure is added
to lower the pitch, the speed drops, and aileron is trying to
decrease the bank angle. At stall the airplane will roll to the
inside of the turn and spin with the rudder. All of the stall
symptoms are the result of sensory illusions too real to be recognized
or corrected. It is too low and too late, you're dead.
The purpose of rectangular patterns is to teach the student that
the turns around a pattern must be planned, adjusted, and shaped
with their straight legs to prevent the initial cause of the
accident above. You must be able to position the aircraft on
to the final approach course without overshooting. Or, if overshooting,
the bank must not be increased nor the airspeed allowed to drop.
You should learn to use "sum of the digits" in than
all four headings at 90 degrees from each other are equal. Using
the four cardinal headings we see that the sum of the digits
for every 90, 180, or 270 degrees are always equal.
North 3 + 6 + 0 = 9
East 0 + 9 + 0 = 9
South 1 + 8 + 0 = 9
West 2 + 7 + 0 = 9
This is also true for headings at 90 degrees to each other as
with 045, 135, 225, 315
S-Turns
The two downwind and two upwind turns of the S-turn combine the
four quadrants of the left and right turns about a point. The
technique calls for the wings to be momentarily level at the
moment of crossing the reference line. The bank angle used just
before leveling the wings will be the same angle but opposite
bank after crossing the reference line. It is important to get
as long a reference line as possible. It helps if the line happens
to have regular division lines to help the student keep the S
as symmetrical as possible. It is a good practice to work the
S to and from both ends of the reference line. In a strong wind
the downwind turns and reversal of bank will need to be quite
abrupt and steep. The upwind turns will be proportionately gradual
and shallow.
One of the best experiences I have every had doing S-turns was
over a slow moving freight train engine. Occasionally, a series
of suitable small fields exist. As with all ground reference
at the private pilot level you are seeking symmetry at constant
altitude.
wind direction
Entry
Common mistakes in making S-turns are such as not varying the
bank angle and forgetting to change the bank angle to correct
for the wind effect. If the pilot does not alternate his scan
in and out of the cockpit then there may be wide variations in
altitude. Keeping track of the wind direction is important in
the correct performance of S-turns.
-Pick a straight road at right angles to the prevailing wind
--Save emergency options must be available throughout the maneuvers.
--Make clearing turns and remember to divide attention inside
and outside
--Watching the horizon will help maintaining altitude
--Fly across one end of the road at 700' AGL In emergencies you
are on base leg for landings.
--PTS calls for first turn to the left so select end of road
accordingly
--Since downwind turn will be steepest begin at about 40/45 degree
bank
--Gradually shallow the bank to cross road at right angles on
completion of half circle
--You use the same angle of bank leaving the road as you did
on arrival.
--Your bank angle on the second half of the S will gradually
increase until reaching the road.
--You reverse this steeper bank at the road and begin the second
S with a steep bank again.
--Performed correctly the S will have the same radius half-circle
on each side of the road.
S-Turns Revisited
--Multi-task flight ground reference
--Pre-landing check
--Clearing turns
--Safe altitude
--Landing site(s)
--Fly a wind circle for wind direction
--Enter downwind at right angles to an extended straight line
and establish maximum bank
--Objective to fly constant radius and altitude turns
--Wind will affect groundspeed and required angles of bank
--Into the wind is shallowest bank and near level wings crossing
road
--Introduce in calm winds, practice in strong winds
--Crosscheck bank, speed and altitude
Eights
Eights combine the skills acquired from doing left and right
turns about a point and S-turns. First find a + with one leg
giving a direct downwind entry. Proceed with a series of left
and right circles in which the downwind turns take you through
the intersection. Your primary effort will be to keep the circles
the same size and the altitude constant. Make your own diagram
.road
shallow turns
wind direction
road steep steep
entry turns turns
steep steep
turns turns
shallow turns
River Flying with
Steep Turns
On some subsequent lesson, it is well to select an upwind
track along a very S shaped course. By flying upwind the relative
ground speed can be reduced with no reduction in airspeed. This
permits relatively steep turns. Any gain in altitude during a
steep turn has a dramatic effect on airspeed and can precipitate
an accelerated stall. I advocate applying full power during these
turns and strict supervision to prevent altitude gain. On completion
of the turn the power is again reduced to cruise. I often give
the student an emergency which results in an off-airport landing.
I have found this particular flight a good student confidence
builder.
Spiral Descents
This particular maneuver is the most difficult of the ground
reference maneuvers. It requires that the student descend over
a selected point, such as the approach end of a runway, The angle
of bank will be constantly changing to adapt to the wind. The
airspeed must be constant. If the spiral is made too tight the
banks become so steep that the student can't control the airspeed.
Just pulling back to reduce airspeed has the effect of increasing
the bank angle and tightening the spiral. This is an interesting
maneuver to do in both left and right turns to show the student
why the left turns are more desirable.
This maneuver and its requirements can best be demonstrated in
an aircraft equipped with an ADF. Tune to a radio station of
NDB in a non-congested area. 990 KKIS near Collinsville is just
fine. Arrive at an altitude of several thousand feet over a radio
station. Reduce power and initiate a descent at best glide speed.
Turn the aircraft so that the ADF needle is pointed to the 270
bearing to the station. The spiral descent is made in left turns
in such a manner
as to keep the needle of the ADF on or near the 270 bearing.
This gives a reference for the student and instructor to gauge
the accuracy of the spiral over the point. Errors show up immediately.
The second descent should be done in right turns with the ADF
on the 090 bearing. Climbs could be made in square patterns so
as to demonstrate the movement of the ADF needle from the front
45 degree position to the rear 45 degree position at the corners
of the square. This is a excellent learning technique for demonstrating
the wind effect and the required flight corrections.
On completion of the above ground reference maneuvers the student
is advised that he should expect and be prepared for 'emergencies'
on any subsequent flight. The student should be advised that
when soloed he will be allowed and expected to practice the ground
reference maneuvers but never emergencies or off airport landings.
The limits of the practice area, the practice altitudes and any
radio procedures and assigned. We are now ready to put the skills
learned in ground reference to work. About this time the student
should realize that he has been practicing the skills needed
for takeoff and landings from the very beginning.
Should you be flying an aircraft equipped with an ADF, it is
rather interesting to perform the spiral about a radio station
antenna. Tune the ADF to the radio station, switch to ADF and
try to perform both
turns and spiral that keep the ADF needle on your wingtip. Not
easy but 'do-able'.
Airspeed
Lesson:
While doing airwork, cover the airspeed indicator and have
the student go through several configurations of flight. This
is to give him a sense of how to estimate speeds using attitude,
power and sound. Fly long enough to obtain stabilized hands-off
flight before making estimate. With practice you will not watch
the IAS, you will only check it to confirm your judgment.
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