Buffet Onset & Flight Envelope

081-03-02Pablo Asensio Martínez2026-04-011 min

Buffet Onset Boundary

The boundary in the flight envelope where buffet occurs.

  • Low Speed Buffet: Caused by airflow separation at high angles of attack (approaching stall).
  • High Speed Buffet: Caused by shock waves forming on the wing (approaching Mach limit).

Aerodynamic Ceiling (Coffin Corner)

As altitude increases:

  1. Low Speed Stall Speed (IAS) increases (due to compressibility effects).
  2. High Speed Buffet Speed (Mach) decreases (Local Speed of Sound decreases).
  • At a certain altitude, these two speeds converge.
  • The pilot has a very narrow margin between stalling (too slow) and overspeeding (too fast).
  • This point is the Aerodynamic Ceiling.

Load Factor ($n$)

Increasing Load Factor (e.g., in a turn or turbulence) increases the Stall Speed. $ V_{stall_{new}} = V_{stall_{1g}} \times \sqrt{n} $

  • Therefore, the margin to buffet decreases when maneuvering.
  • 1.3g Buffet Boundary: Altitude where the aircraft can pull 1.3g (40° bank turn) before encountering buffet. This is typically the practical operating altitude limit.
Written and reviewed by

Pablo Asensio · 2026-04-01

Aeronautical engineer. Passed the thirteen EASA ATPL(A) theoretical knowledge exams studying from these very notes. Writes and reviews each topic against the Part-FCL Learning Objectives.

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