On December 15, 1993, the crew of an IAI 1124A Westwind being operated by Martin Aviation on a passenger charter flight from La Verne CA to Santa Ana CA lost control of their aircraft and it crashed about 3.5 nm north of Santa Ana Airport. The aircraft commander, acting as pilot flying (PF) was making a visual night approach behind a Boeing 757-200. The aircraft was destroyed by the impact and all five occupants were killed.
An investigation carried out by the National Transportation Safety Board (USA) (NTSB) found that:
"The (Boeing) 757 & the WW (Westwind) were sequenced for visual approaches behind (a) Beech. Before being cleared for visual approach, the WW was closing 3.5 miles from the 757 on a converging course. The 757 & WW crews were told to slow to 150 kts. The 757 slowed below 150 kts & was high on final approach with a 5.6 degree descent. The WW continued to converge to about 2.1 mi behind the 757 on a 3 deg apch. ATC did not specifically advise, and was not required by ATC handbook to advise, the WW pilots that they were behind a Boeing 757. (The Captain of the WW) discussed possible wake turbulence, flew (the) ILS 1 dot high, noted closeness to the 757 & indicated there should be no problem. While descending (through) approximately 1100 ft amsl, the WW encountered wake turbulence from the 757, rolled into a steep descent & crashed". Subsequently, an anti-histamine medicine not approved for flying was found in the lung tissue of the pilot-in-command.
It was found that the crew had not had any specific wake turbulence training.
The NTSB determined that the probable cause of this accident was:
The pilot-in-command's failure to maintain adequate separation behind the Boeing 757 and/or remain above its flight path during the approach, which resulted in an encounter with wake vortices from the 757.
It also found that Factors related to the accident were:
- an inadequacy in the ATC procedure related to visual approaches and VFR operations behind heavier airplanes
- the (consequent) lack of information to the Westwind pilots for them to determine the relative flight path of their airplane with respect to the Boeing 757's flight path.
The Final Report of the Investigation was adopted on 10 June 1994. No Safety Recommendations were made.