During commercial pilot training, advanced maneuvers are required to further evaluate the student’s piloting abilities; one such maneuver is eights-on-pylons. In this maneuver, students are required to demonstrate a strong ability to divide attention between precise control of the aircraft while turning around a ground reference at a specific pivotal altitude, which is constantly changing with the groundspeed due to the effects of the wind. Students should not be deterred by these advanced maneuvers as they are indeed achievable once the necessary concepts have been well understood. This guide provides students with the knowledge to help comprehend pivotal altitude and safely execute the eights-on-pylons maneuver.
What is Pivotal Altitude?
Pivotal altitude is the altitude at which, for a given groundspeed, the projection of an imaginary visual reference line to a single point on the ground appears to pivot. This visual reference line should be parallel to the lateral axis of the aircraft and should point to a single landmark on the ground throughout the turn. Often, the wingtip is used to represent this reference line on rectangular-wing aircraft. In the image below, the ground reference (or pylon) used is a small lake.
Pivotal altitude can be determined by the following formula:
*Groundspeed in knots. For miles-per-hour, divide by 15, instead of 11.3.
Groundspeed is adopted, instead of indicated airspeed (IAS), as pivotal altitude is dependent on the horizontal speed of the aircraft relative to the ground. Although the aircraft’s IAS should remain constant in flight, the groundspeed will fluctuate, especially when transitioning from a headwind to a tailwind, or vice versa. It is recommended that you create a table, like the one below, for your local area to keep as a reference on your knee board.
As shown in the table below, the higher your groundspeed, the higher the pivotal altitude will be. The objective is to maintain the proper pivotal altitude so that the wingtip is centered above/below the pylon throughout the turn (depending on whether you are flying in a low wing or high wing airplane). If you find that the wingtip is moving off the pylon, remember to correct toward the pylon. For example, if you are above the pivotal altitude, the wingtip appears to move rearward in relation to the pylon. So, you need to move the yoke forward toward the pylon which will begin a descent back down to the proper pivotal altitude. Conversely, when the airplane is below the pivotal altitude, the wingtip appears to move forward of the point on the ground, so pull the yoke back toward the pylon to initiate a climb.
In a no-wind condition, the pivotal altitude remains constant because groundspeed is also constant. However, no-wind conditions are a rarity and your groundspeed will, more often than not, fluctuate. Therefore, to maintain the reference line on the pylon, you will have to adjust your altitude throughout the turn in tandem with groundspeed fluctuations. This means that when you are in a headwind, the pylon will begin to move ahead of your reference line, and you will have to descend since both groundspeed and pivotal altitude are decreasing. In a tailwind, groundspeed increases causing the pylon to move behind your reference line, and you will have to climb to maintain the proper pivotal altitude.
Success in performing this maneuver depends greatly on the pilot’s ability to maneuver the airplane accurately while dividing attention between the flight path and the selected pylon on the ground.
To effectively carry out eights-on-pylons, you first need to select two prominent landmarks to circle around. An effective way to do this is by first flying upwind (in a headwind). Select your first point by looking for a prominent landmark that lies ahead on your flight path. A standalone tree, a small lake, a brightly-colored barn, or an intersection are effective points to select.
For your second point, fly directly over your first point and look out to the left or right. Any prospective landmark that lies halfway up the wingstrut for a high wing aircraft (or directly off the wingtip for a low wing aircraft) is your second point. The distance between the pylons should allow for the straight-and-level flight segment to last from 3 to 5 seconds. The selected pylons should also be at the same elevation and lie perpendicular to the direction of the wind.
Once you have selected your two points, continue flying upwind before turning 180° and flying downwind toward your second point. At this moment, determine your groundspeed and adjust your altitude to the correct pivotal altitude. When you are 45° from the center of the two points, begin a 45° turn toward the center to commence the maneuver.
Once the wingtip is just behind your first landmark, roll into the turn and begin to circle around the first point, keeping your wingtip on the landmark by descending/ascending to the correct pivotal altitude. Since the maneuver begins with a tailwind, your groundspeed, and therefore pivotal altitude, will be highest at the beginning of the maneuver. This means that you should be slowly descending through the first half of the turn to maintain the pivotal altitude, and climbing through the second half.
After completing the first circle, level off by flying straight and level to your second landmark. Be sure to crab slightly into the wind to maintain the correct flight path. Complete the second circle and exit the maneuver by flying through the center of the two points on the 45° downwind.
Success in performing this maneuver depends greatly on the pilot’s ability to maneuver the airplane accurately while dividing attention between the flight path and the selected pylon on the ground. In order to maintain pivotal altitude, the pilot must develop subconscious control of the airplane to align the lateral axis of the airplane with the pylon throughout the turn. If too much focus is placed inside the airplane on the instruments, the pylon may quickly slip away from the wingtip and the pivotal altitude may be lost. Instead, the pilot should focus outside the airplane, looking at the pylon, and only occasionally return to the instruments to verify proper indications.
The first common error that students make is a mathematical one. Students who train in low elevation areas (like Florida) often assume that including elevation in the pivotal altitude formula is negligible – this is a dangerous assumption. By neglecting to include even 200 feet to your pivotal altitude calculation, you may inadvertently set yourself up too close to the ground.
The next common error is the excessive use of rudder. Rudder should be used to remain coordinated in every phase of the maneuver; however, rudder should not be used to slip or skid the aircraft to maintain the ground landmark off the wingtip. When the visual reference line moves forward with respect to the pylon, many students tend to apply inside rudder pressure to yaw the wing backward. Rudder should only be used for coordination. Altitude adjustments should be made instead to keep the reference line pivoting on the ground landmark.
Lastly, in the straight-and-level phase of the maneuver, a near-direct crosswind should always be expected. Students often forget to crab slightly into the wind as they maneuver toward the second point and this places the aircraft further from the second point than the first.
Remember to divide your attention inside and outside the airplane throughout the maneuver. When performed during your practical test, this is a key point that your evaluator will be looking for. Dividing your attention is not only a key factor in successfully performing the maneuver, it is imperative that you effectively manage risks, in part, by constantly scan the area for obstructions, traffic, and other hazards to flight.
To conclude, the eights-on-pylons maneuver is rather straightforward once you’ve attained a complete understanding of pivotal altitude and how to correctly set up for the maneuver. With practice, control inputs to maintain pivoting around the reference point on the ground may become slight enough to be barely noticeable. For more information on pivotal altitude and eights-on pylons, refer to the Gleim Commercial Flight Maneuvers book.
Written by: Ryan Jeff (CFI, AGI), Aviation Research Assistant