Page 3.28 (6,824)
Return to whitts flying Home Page

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
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

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

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

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 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
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.

Return to whittsflying Home Page
Continued on Page 3.305 Hood Flying and Illusions