Lesson Plan
Ground Reference Maneuvers: Eights-on-Pylons
Purpose
Eights-on-pylons were first used during early days of military aviation. Skilled First World War pilots could keep targets on the ground in a consistent position for airborne artillery.
The purpose of eights-on-pylons is to develop the pilot's ability to maneuver the airplane accurately while dividing attention between the flight path and the selected points on the ground. Eights on pylons teach, develop, and test the pilot's subconscious control of the airplane.
Elements
"Subconscious control": Eights-on-Pylons is a maneuver that allows the pilot to demonstrate a "subconscious control of the airplane."
Division of attention: Eights-on-pylons is not a ground-track maneuver, but instead a demonstraton of how the pilot flies with divided attention.
The reference is maintained by altitude, not bank angle: While ground reference maneuvers at the priate pilot level train pilots to maintain a ground reference using varying bank angles at a consistent altitude, eights-on-pylons maintains the ground reference with a "pivotal" altitude.
Bank is based on distance: Pivotal altitude does not vary with angle of bank. Rather bank is variable based on how far the maneuver is flown from the pylon.
A figure eight: After calculating and establishing pivotal altitude for a given airspeed, a figure-eight pattern is flown around two ground-reference points, which serve as the "pylons," with the airplane's wing positioned on the pylon throughout the turn.
The pilot may use any sighting reference that parallels the airplane's lateral axis.
Calculating pivotal altitude: Pivotal altitude can be determined by taking the square of the airspeed and dividing by either 11.3 (knots) or 15 (MPH). Thus, if flying the maneuver at 90 knots:
90(90) = 8,100
8,100 ÷ 11.3 = 716.8.
For eights-on-pylons flown at 90 knots, an AGL pivotal altitude of 700 feet would be good starting point.
Groundspeed, not airspeed: While the initial calculation typically is done with airspeed, pivotal altitude is determined by groundspeed, not airspeed, so airspeed can be adjusted in accordance with winds in order to maintain a constant groundspeed (or altitude can be adjusted to a new pivotal altitude).
Always AGL: Pivotal altitude is always expressed as AGL, so the difference between AGL and MSL must be determined in order to hold the pylons correctly. With pylons at 200 MSL, the maneuver at 80 knots would be flown at 1,209 feet MSL.
Quick reference: Pilots may consider flying with a groundspeed table to quickly estimate pivotal altitude for a range of groundspeeds.
| Knots | MPH | Pivotal Altitude (AGL) |
| 80 | 92 | 566 feet |
| 85 | 98 | 639 feet |
| 90 | 104 | 717 feet |
| 95 | 109 | 799 feet |
| 100 | 115 | 885 feet |
Maintain the reference with pitch: Elevator (pitch) is used to hold the pylons. If flying ahead of the pylon, the pilot should climb; conversely, falling behind the pylon requires descent. Practically speaking, climb and descent can be used to find pivotal altitude in absence of prior calculation.
Catch up and fall away: As an example, in properly coordinated eights-on-pylons, if the reference point is behind the pylon, it means the airplane is above the pivotal altitude. The airplane needs to reduce altitude to create the "catch up" effect. Flying high has caused the reference point to "fall away."
Common Errors
A common pilot error is to introduce a rudder input to "hold" a moving pylon during the maneuver. Rule of thumb: Misuse of rudder while attempting to hold the pylon will result in a slip when above pivotal altitude and a skid when below pivotal altitude.
- If the wing moves behind the pylon during properly coordinated eights-on-pylons, the airplane is above pivotal altitude. The appropriate correction is to reduce altitude: "Fly low — let's go." The incorrect input is outside rudder, which will move the wing forward. However, this also will introduce a slipping turn, as airplane will exhibit adverse yaw.
- If the wing moves in front of the pylon during properly coordinated eights-on-pylons, the airplane is below pivotal altitude. The appropriate correction is to increase altitude: "Fly high — fall behind." The incorrect input is inside rudder, which will move the wing back. However, this also will introduce a skidding turn, as the airplane will overbank.
Common errors in the performance of eights-on- pylons include:
- Application of inside rudder pressure to yaw the wing backward when the projection of the visual reference line moves forward.
- Failure to adequately clear the area above, below, and on either side of the airplane for safety hazards, initially and throughout the maneuver.
- Poor selection of ground references.
- Failure to establish a constant, level altitude prior to entering the maneuver.
- Failure to maintain adequate altitude control during the maneuver.
- Failure to properly assess wind direction. Failure to properly execute constant radius turns.
- Failure to manipulate the flight controls in a smooth and continuous manner.
- Failure to establish the appropriate wind correction angles.
- Failure to apply coordinated aileron and rudder pressure, resulting in slips or skids.
- Failure to maintain orientation as the maneuver progresses.
Completion Standards
Commercial Pilot & CFI Practical Test Requirements
- Determine pivotal altitude
- Enter maneuver downwind and the steepest point (30º - 40º bank)
- Hold rope on pylon throughout turn
- Maintain awareness inside and outside the aircraft
- Hold pivotal altitude throughout maneuver
More Details
More details are available in the Airplane Flying Handbook