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Ground Reference Maneuvers in Wind

This month we will cover the ground reference maneuvers necessary to get through your check ride. This applies to fixed wing, weight-shift control trikes, and powered parachutes.

First off, why are ground reference maneuvers required to become a sport pilot? They are simply used to demonstrate a level of pilot proficiency. These specific maneuvers are not performed typically during every flight, but the principles and elements are used to develop the pilot's skill in analyzing the effect of wind and other forces acting on the aircraft in flight.

Ground reference maneuvers require a higher level of skill because your altitude and track can easily be measured to references on the ground. Even if you are going to stay within the ultralight arena, the ground reference maneuvers enhance your airmanship and mastery of the aircraft.

Generally all of the practical test standards (PTS) checkride ground reference maneuvers should: Be conducted so that the minimum altitude over the ground for any part of the maneuver should be 600 feet AGL for airplanes, 400 feet AGL for Weight Shift (trikes), and 200 feet AGL for PPC. An important note on this: This means that the maneuver must be started at least 100 feet above this minimum value to allow for altitude tolerances of minus 100 feet from the starting altitude .

• Maintain a constant ground track in calm conditions or high winds
• Maintain airspeed +/- 10 knots (for airplanes and weight shift control only)
• Roll into and out of headings +/- 10 degrees
• Divide attention in and out of the cockpit to adequately maintain ground track and watch for other aircraft

Most competent ultralight pilots welcome the opportunity to increase their flight skills and enjoy learning precision ground reference maneuvers.

As a FAA examiner screening sport pilot applicants to take check rides, I have heard many times, "I am not worried about the flight portion of the checkride, I have been flying ultralights twenty years, I know how to fly". Yes, knowing how to fly is one thing, but performing specific ground reference maneuvers to sport pilot tolerances is another. Simply, if you do not know what the specific maneuvers are and have not practiced them, you will fail the practical test. Here is your opportunity to get started.

If you are going to be taking your sport pilot check ride, start practicing these maneuvers when you go flying. Find an instructor who knows how to perform the maneuvers and can critique you. Do not show up for a checkride unprepared.

Low Pass

We are going to start with a ground reference maneuver not required for the checkride, but I feel is the best maneuver to start with near the ground. The rest of the maneuvers will build in this technique. This is typically known as a "low approach" to general aviation pilots, or simply a "low pass" down the runway. This is what I use to get students used to flying near the ground and have them develop the proficiency for determining their height above the ground. This is the exercise learned before performing landings. It is simply flying down the center of the runway at a constant altitude following a straight line. Airports or your landing strip is a good place to do this.

The objective is to stay over directly over the center line at a constant altitude and not drift side to side. Powered parachutes do not have to worry about airspeed since they have no airspeed control. However, airspeed for trikes and fixed wing should be at approach speed or at least 1.3 times stall speed at a minimum and typically 1.5 times stall speed. You should always be flying well above stall speed any time you are flying close to the ground.

Start in calm air twenty feet high. Precise power adjustments are needed plus slight pitch changes are needed for trikes and airplanes. You start practicing high but work your way down in altitude as you master the technique, until you can touch a wheel at will as you skim inches high right over the center line. As you develop the technique, you can expand to crosswinds and more active air. This exercise is fun and the foundation to learning how to fly in reference to the ground.

Practical Test Ground Reference Maneuvers - As you start practicing these maneuvers you start in calm wind. After mastery with little wind, the maneuver becomes more difficult as the wind increases. Ground reference maneuvers wind considerations:

• Ground speed will be the same when the airplane has the same headwind component.
• Ground speed will be the same when the airplane has the same tailwind component.
• Steepest angle of bank is required at the points where the airplane is flying downwind.
• Shallowest angle of bank is at the points when flying upwind Crab angles.
• Aircraft will have to be crabbed into the wind the greatest amount where it is flying crosswind.
• There is no crab angle when the airplane is flying directly upwind or downwind.

Rectangle Course

The most basic ground reference maneuver that is a TASK in the Sport Pilot Practical Test Standards for all categories is the rectangular course. This is where you learn to fly straight ground tracks to form a rectangle. The maneuver simulates a typical airport pattern. How this becomes a precision maneuver is maintaining a specific altitude, performing the turn to exit on the precise heading, and maintaining a precise ground track in the rectangular box accounting for wind. Fixed wings and weight shift control must maintain a constant airspeed plus or minus 10 knots from the reference airspeed started at the beginning of the maneuver. This maneuver is first practiced in calm winds, but eventually you must become proficient in windy conditions. Objectives for the maneuver are:

• Timing the start of a turn so that the turn will be fully established at a definite point over the ground.
• Timing of the recovery from the turn so a definite ground track is established.
• Estimation of a ground track and the determination of the appropriate "crab" angle.

Weight shift control, powered parachutes, and open cockpit fixed wings can plan the maneuver straight over selected roads, fences, or other course because you can easily see the ground in front. For best results when planning a rectangular course for the typical enclosed airplane, the flight path should be positioned outside the field boundaries just far enough that they may be easily observed from either pilot seat by looking out the side of the aircraft.

The smaller the rectangular course or closer the track of the aircraft is to the field boundaries, the steeper the bank necessary at the turning points.

We will look at the rectangular course diagram to discuss the maneuver in wind. You would typically enter down wind, entering at a 45 degree angle from the left and enter at the position between numbers 2 and 3. After you enter the down wind, you have no crab angle. This is equivalent to entering the downwind leg of an airport pattern. Your turn at position 3 must be more than 90 degrees to roll out to the precise crab angle into the wind. Between position 3 and 4 you maintain a ground track parallel to the course leg.

Note that you must be dividing attention inside the cockpit to monitor altitude and adjust throttle to maintain the altitude, and outside the cockpit to maintain the proper course and look for other aircraft.

Your turn at position 4 is less than 90 degrees because you are first crabbed into the wind as you turn up wind where there is no crab angle. From position 4 to 1 is the up wind or equivalent to the final approach of an airport pattern. This is the slowest ground speed since you are flying directly into a head wind.

Your turn at position 1 is less than 90 degrees since you must establish a crab to account for the right cross wind. You maintain your ground track by adjusting the crab angle into the wind for this cross wind leg. Your turn at position 2 must be more than 90 degrees since you started with a crab angle and must turn extra to enter the down wind leg of the rectangular course. You roll out into the down wind with the fastest ground speed since you are going down wind. Before you get to position 3, you exit he course by turning 45 degrees to the right. Note that throughout maintaining your ground track accounting for the wind, you must monitor altitude and adjust throttle to maintain plus or minus 100 feet, plus the fixed wing and weight shift must monitor and control airspeed plus and minus 10 knots.

This is a great practice exercise you can do while doing touch and goes or just flying around your field.

S-Turns

The next step in developing proficiency with ground reference maneuvers is the S-turns over a road or straight line. The aircraft ground track is semi circles of equal radii on each side of a selected straight line on the ground. Here we build off rectangular course objectives with constant turning in alternate directions, compensate for wind drift during turns, orient the flight path with ground references, follow an assigned circular ground track, and arrive at specified points on assigned headings.

We will use the S-Turns over the road diagram to describe this maneuver in wind. You establish your altitude and airspeed and enter from the down wind to establish the first semi circle radius. You fly directly perpendicular over the straight line and go into your turn. Since you are flying down wind this will be the greatest bank angle of this maneuver just after you cross the road, At position 2 you are crabbed into the wind and continue your semi circle so that between positions 3 and 4 you fly perpendicular over the road.

Flying from position 4 to 5 you are into a head wind so your bank angle will be much shallower to fly upwind and maintain the same size semi circle during this upwind leg. At position 5 you are crabbed into the wind and must turn more abruptly and increase your bank angle as you go downwind. You need to roll out and be perpendicular to the straight line to complete the maneuver. Many times during the Checkride Test I have the applicant continue with four total semi circles .

Turns Around A Point

• Build off S-turns objectives in a continuous turn.
• Further perfect turning technique.
• Understand the radius of the turn is a distance which is affected by the degree of bank used in turning with relation to a definite object.
• Develop a keen perception of altitude.
• Perfect the ability to correct for wind drift during turns.

Using our turns about a point diagram we enter at position 7 down wind and establish the steepest bank angle since we are traveling downwind. At position 5 we are crabbed to the left and decreasing bank as we head up wind. At position 3 the bank is the least and continues to shallow until it starts to increase from position 1 through position 7 where it becomes the steepest flying down wind.

A good technique is once the maneuver is started at position 7, you locate points that you should be over for positions 5, 3 and 1 so you can cross check your distance from the center point. Many times it might be hard to determine the wind direction and the objective of the task is to stay an equal distance from the point. This is the most difficult maneuver to fly in wind because if you start your up wind turn to soon, you will drift over the center point. This is the most common mistake flying in wind.

Common errors for all ground reference maneuvers:

• Failure to clear area before performing maneuver
• Failure to establish proper banks in turns
• Failure to recognize wind drift
• Failure to maintain altitude within tolerance
• Failure to maintain consistent airspeed (weight shift and airplane only)
• Inadequate visual look out for other aircraft

In Summary

Learn and practice ground reference maneuvers to become a better pilot and be able to get through these tasks of the Checkride. These maneuvers are new for most ultralight pilots and must be practiced to become proficient. We used a perfect world in our descriptions above with wind directions exactly parallel or perpendicular to the reference lines and flight directions. The wind is usually not exactly this perfect, so you must make adjustments to maintain the proper ground tracks. This adapting to real life wind is part of your ability to master that aircraft. Have fun flying!

Pictures

	A powered parachute pilot making a left hand turn during an S-turn maneuver getting ready to fly perpendicular over the straight line.
	A weight-shift control trike pilot making a left hand turn during an S-turn maneuver getting ready to fly perpendicular over the straight line.
	An airplane making a left hand turn during an S-turn maneuver getting ready to fly perpendicular over the straight line.
	Weight-shift control trike crossing over straight line perpendicular to line during S-turns maneuver.
	Weight-shift control trike lined up on road performing a rectangular course with no wind.
	Practicing ground reference maneuver 1000 feet AGL perpendicular above straight line.
	Airplane performing rectangular course. Note rectangular course lines in the background.
	Paul referring to checklist after maneuver was performed.
	1. Powered Parachute sequence showing the four corners of a turn around a point. Notice the shadow of the sun for position and distance from point in each picture.
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	Rectangular Ground reference maneuver in wind.
	S-Turns ground reference with wind.
	Turns about a point ground reference maneuver in wind.