FAA Flight Instructor Airplane (FIA)Flight Maneuvers and EndorsementsHard
A commercial pilot applicant is performing eights-on-pylons with a groundspeed of 150 knots. Using the pivotal altitude formula, approximately what altitude AGL must the pilot maintain to keep the pylon on the reference line?
- A1,991 feet AGL
- B2,265 feet AGL
- C1,274 feet AGL
- D1,495 feet AGL
Show answer & explanationAnswer & explanation
Correct answer: A. 1,991 feet AGL
Pivotal altitude (ft AGL) = groundspeed (kt)^2 / 11.3. With 150 knots: 150^2 = 22,500; 22,500 / 11.3 ≈ 1,991 feet AGL. This is the altitude at which the pylon appears to pivot on the wingtip reference line, and it varies only with groundspeed, not bank angle.
Why the other options are wrong
- B. This value corresponds to a groundspeed of about 160 knots, not 150.
- C. This value corresponds to a groundspeed of about 120 knots, not 150.
- D. This value corresponds to a groundspeed of about 130 knots, not 150.
Pivotal Altitude
The altitude AGL at which, for a given groundspeed, the projected line of sight to a pylon remains fixed, allowing the pylon to appear to pivot on the wingtip during eights-on-pylons.
- Formula: PA (ft AGL) = GS(kt)^2 / 11.3
- Pivotal altitude changes with groundspeed, not bank angle
- Wind requires constant altitude adjustment during the maneuver as groundspeed changes
Memory trick: 'GS Squared over 11.3' pins the pylon under the wingtip.