Quantitative analysis of aircraft height on final approach

• As advised in the Aeronautical Information Manual (AIM) Section 7–3–6, in visual operations flight crews of smaller trailing aircraft can stay at or above a larger leading aircraft´s final approach flight path for wake encounter risk mitigation • Quantitative data shows that smaller trailing aircraft generally follow this guidance — The smaller the aircraft, the higher they ride • Small and “lower larges” (e.g., CRJ´s) fly higher than the lead aircraft when following Heavies, 757s or “upper larges” (e.g., B737, A320) — Heavies, B757s and “upper larges” generally do not ride higher than the lead aircraft behind Heavies, B757s or “upper larges” — The closer the aircraft is to the leader, the more pronounced is the effect • This effect is seen even when distances are greater than standard radar and wake turbulence separations • Similar behavior is observed for operations on parallel runways • This effect is greatly diminished in IMC and during SOIA operations at SFO • New procedures (e.g., CDTI enhanced delegated separation, or CEDS) could be introduced that take advantage of this behavior by allowing for flying high in lieu of adding spacing behind larger aircraft even in less-than-visual conditions