SEATTLE, WA, USA
N38GF
Cessna 172P
The accident aircraft was in a right-hand traffic pattern for runway 31R, approaching for a touch-and-go landing just after a Boeing 767 (B-767) landed on parallel runway 31L (the two runways are spaced about 360 feet apart.) The wind was from 290 degrees magnetic at 7 to 12 knots, yielding a cross-runway wind component of approximately 2 to 4 knots in the 31L-to-31R direction during the accident time frame. Three on-duty tower controllers reported that the aircraft overshot final for runway 31R and lined up on the runway 31L final approach course behind the landing B-767, and that the accident aircraft was low on its approach for runway 31R. The airplane subsequently rolled to an extreme bank attitude and crashed, coming to rest in the runway 31L displaced threshold area. The pilot had 173.7 hours total pilot time, including 69.9 hours as pilot-in-command.
On April 11, 2000, approximately 1439 Pacific daylight time, a Cessna 172P, N38GF, operated by Galvin Flying Service of Seattle, Washington, was substantially damaged in a collision with terrain at Boeing Field/King County International Airport, Seattle, Washington. The private pilot-in-command, who was the airplane's sole occupant, received minor injuries in the accident. Visual meteorological conditions prevailed and no flight plan had been filed for the 14 CFR 91 local personal flight from Boeing Field. The accident aircraft was in the traffic pattern for runway 31R, approaching runway 31R for a touch-and-go landing just after a Boeing 767 (B-767) aircraft landed on parallel runway 31L. The pilot reported that while she was on downwind, the tower came on and said that winds were from 290 degrees at 12 knots, that she was cleared for touch and go, and to watch for wake turbulence from an incoming "727" (the pilot identified the aircraft landing on the parallel runway 31L as this type throughout her accident report narrative.) She stated that she noticed that the "727" was on approach, and that she could still see the "727" on approach as she turned base. She stated that as she turned base-to-final, the "727" was landing on runway 31L. She further reported: ...I was on [approach] for 31R with full (30 [degrees]) flaps. My altitude was approx[imately] 700'. With [sic] a few seconds my plane turned quickly to the left at about 90 [degrees]-I quickly turned my ailerons right & overcorrected. I then turned again to correct the sudden movement & realized I was in the wake turbulence of the 727. I attempted to pull up on the yoke but found myself nose in at the beginning of & adjacent to 31L and had skidded across the grassy area onto the chevrons at the base of 31L.... Three on-duty tower controllers indicated in written statements that they observed the accident aircraft overshoot the runway 31R final approach course and line up with the runway 31L final approach course. The two local controllers reported in their statements that the aircraft was low on its approach to runway 31R at that time. The Local Control-West (LC-W) controller (controlling traffic on runway 31L) reported that he then advised the Local Control-East (LC-E) controller (controlling traffic on runway 31R, including the accident aircraft) to issue a wake turbulence advisory for the landing B-767. The LC-E controller reported that she issued this advisory. The controllers stated they subsequently observed the airplane abruptly roll to a high bank angle (the LC-E controller reported the airplane's wings went perpendicular to the ground) and crash onto the approach end of runway 31L. A transcript of ATC tower communications provided by the FAA indicated that the accident aircraft was cleared for a touch-and-go landing on runway 31R at 1437:15. At 1439:10, the tower controller instructed the pilot to verify that she was landing on runway 31R, and the pilot replied, "31 right, 8GF." At 1439:20, the tower controller cautioned the pilot of N38GF about possible wake turbulence from a heavy Boeing 767 (B-767) aircraft landing on runway 31L. Sixteen seconds later, at 1439:36, the tower controller asked the pilot of N38GF, "are you OK". The controller subsequently made three additional attempts to contact N38GF before the pilot responded, "I'm OK." The controller then advised the pilot of N38GF that "we have the fire trucks coming to check on you." The aircraft came to rest in the displaced threshold area of runway 31L. Boeing Field has two parallel runways, 31L (10,000 feet long, with an 800-foot displaced threshold) and 31R (3,710 feet long, with a 365-foot displaced threshold.) The runway 31R threshold is approximately 4,800 feet beyond the runway 31L threshold, and the runway centerlines are approximately 360 feet apart. Runway 31L is equipped with a precision approach path indicator (PAPI) system set to a glide path angle of 3.1 degrees and threshold crossing height of 71 feet, and runway 31R is equipped with a visual approach slope indicator (VASI) system set to a glide path angle of 4.0 degrees and threshold crossing height of 26 feet. A right-hand traffic pattern is utilized for runway 31R. The 1353 Boeing Field METAR observation reported winds from 310 degrees true (equivalent to 290 degrees magnetic, at Boeing Field's magnetic variation of approximately 20 degrees East) at 7 knots. A special observation taken at Boeing Field at 1445 reported winds from 310 degrees true (290 degrees magnetic) at 9 knots. The Aeronautical Information Manual (AIM), paragraph 7-3-4b, states: "A crosswind will decrease the lateral movement of the upwind vortex and increase the movement of the downwind vortex. Thus a light wind with a cross runway component of 1 to 5 knots could result in the upwind vortex remaining in the touchdown zone for a period of time and hasten the drift of the downwind vortex toward another runway....Pilots should be alert to large aircraft upwind from their approach...flight paths." The pilot reported that she had 173.7 hours total pilot time, including 69.9 hours of pilot-in-command time.
The pilot's failure to attain proper alignment with the landing runway, and her failure to maintain proper glide path for the landing runway, resulting in an encounter with vortex turbulence from a preceding heavy aircraft landing on a parallel runway and subsequent loss of aircraft control. Factors included the pilot's lack of total flying experience, and crosswind conditions conducive to a vortex turbulence encounter.
Source: NTSB Aviation Accident Database
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