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N117WM accident description

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Tail numberN117WM
Accident dateMarch 02, 1997
Aircraft typeBeech 200
LocationSalt Lake City, UT
Additional details: None

NTSB description

HISTORY OF FLIGHT

On March 2, 1997, approximately 1913 mountain standard time, a Beech 200 Super King Air, N117WM, registered to Coast Hotels and Casinos Inc. of Las Vegas, Nevada, collided with terrain approximately 1.3 nautical miles short of the runway while on an instrument landing system (ILS) approach to runway 34R at Salt Lake City International Airport, Salt Lake City, Utah. The airplane was substantially damaged and, of the airplane's four occupants, one passenger was fatally injured and the airline transport pilot-in-command and the aircraft's other two passengers were seriously injured. The 14 CFR 91 executive/corporate flight originated at McCarran International Airport, Las Vegas, Nevada. Night instrumental meteorological conditions existed at the time, and the flight was on an instrument flight rules (IFR) flight plan.

The pilot reported that the flight proceeded uneventfully to the Fairfield VOR, and initial approach fix (IAF) for the ILS runway 34R approach. The pilot stated that he was then given a vector by air traffic control (ATC) to intercept the runway 34R localizer. A transcript of the communications between N117WM and Salt Lake Approach indicated that at 1859:56, after the pilot of N117WM checked in at an altitude of 15,000 feet, Salt Lake Approach instructed N117WM: "...roger two six miles from plage turn right heading zero one zero cross plage at or above one one thousand cleared ILS runway three four right approach." (NOTE: PLAGE, SCOER, and KERNN intersections are successive fixes on the ILS approach. All are located on the runway 34R localizer course, with KERNN being collocated with the outer marker.) The Salt Lake approach controller then advised "lear seven whiskey mike" that the runway visual range (RVR) for runway 34R was out of service, and that the visibility was 1/2 mile. According to the ATC transcript N117WM replied "(unintelligible) seven whiskey mike" to this. ATC recorded radar data indicated the N117WM began its descent from 15,000 feet at 1901:45, 18 nautical miles south of PLAGE. The pilot indicated in his report of the accident that the aircraft's autopilot was coupled in the approach mode for the approach.

At 1901:48, Salt Lake Approach asked N117WM to "say air speed", and the pilot of N117WM replied that he was "indicating one eight zero." Salt Lake Approach then instructed N117WM to "maintain best forward speed." According to the ATC radar data, N117WM subsequently started a left turn to the localizer, at about 1903:45. At 1904:49, Salt Lake Approach instructed N117WM to "...maintain best forward speed until ah score [sic] cross kernn at one seven zero knots contact tower now one one niner point five." The transcript indicated that the best possible interpretation of the pilot's reply was, "(score [sic] forward speed) best forward speed till score [sic].

At 1905:25, N117WM checked in with Salt Lake Tower, reporting out of 12,500 feet for 11,000 feet. Salt Lake Tower instructed "king air one one seven whiskey mike" to continue, at 1905:25, then corrected the call sign at 1906:16, instructing "king air one seven whiskey mike" to continue. The pilot of N117WM replied "say again" to this, at 1906:23 and again at 1906:28, and the controller repeated the instruction to continue at 1906:40. The ATC radar data indicated the N117WM passed abeam PLAGE about 1906:32, at an altitude of 11,800 feet (800 feet above the minimum altitude specified in the ATC clearance and 1,300 feet above the published minimum altitude at PLAGE) and abeam SCOER about 1907:55, at an altitude of 10,500 feet (1,500 feet above the minimum altitude at SCOER depicted on the published approach procedure.) At 1910:17, Salt Lake Tower called: king air one one seven whiskey mike caution wake turbulence boeing seven fifty seven six miles ahead wind three six zero at one five runway three four right cleared to land." (N117WM was following DAL616, a Boeing 757 [B-757] aircraft, on the ILS approach. ATC radar data showed that at the time DAL616 arrived over the runway threshold, N117WM was approximately 5.4 nautical miles behind the B-757. ATC minimum radar separation distance for landing, for a small aircraft following a B-757, is 5 miles.)

The approach procedure specifies that a descent to a glide slope intercept altitude of 7,100 feet (minimum) is initiated at SCOER. Based on the published glide slope angle of 3.00 degrees, threshold crossing height (TCH) of 53 feet, and touchdown zone elevation (TDZE) of 4,222 feet, glide slope intercept at 7,100 feet altitude was computed by investigators to occur approximately 8.9 nautical miles from the runway threshold, or about 6.5 nautical miles past SCOER. ATC radar data indicated that N117WM crossed KERNN, the outer marker, at 1910:51, at 7,00 feet and a radar-indicated speed of 163 knots. The glide slope altitude at KERNN, as depicted on the approach procedure profile view, is 6,095 feet.

At 1911:14, Salt Lake Tower informed N117WM of an Embraer EMB-120 aircraft holding in position on the runway; the acknowledgment of this call by N117WM, at 1911:20, was the last reported radio transmission from the accident aircraft. ATC radar data indicated that the aircraft remained above the glide slope from KERNN until attaining the glide slope from above about 1.8 nautical miles from the threshold, at 1912:42, 4,900 feet altitude (478 feet above decision height) and a radar ground speed of 103 knots. The aircraft remained generally on the glide slope for 28 seconds, from 1912:42 until 1913:10, at which point its radar ground speed indicated 73 knots. During the 28-second period the aircraft was on the glide slope, its average rate of radar groundspeed decay increased from 0.54 knots per second (between KERNN and the time of glide slope capture) to 1.07 knots per second.

At 1913:14, the aircraft dropped well below the glide slope and its radar speed reached its minimum value of 70 knots. The loss of 200 feet of altitude (from 4,700 to 4,500 feet) from 1913:10 to 1913:14, in combination with the radar ground speed of 70 knots during this interval, was computed to correspond to an average downward vertical flight path angle during the interval of 20.3 degrees below the horizontal. The last radar return recorded was at 1913:18, at 4,400 feet altitude (approximately 200 feet above the touchdown zone elevation) and 71 knots. The crash site was approximately 1.3 nautical miles short of the runway 34R threshold, about 1/4 mile left of the localizer centerline.

The pilot's recollection of the accident sequence, as given in the narrative in his report of the accident, was as follows:

...Being slightly above the glide slope, the auto-pilot did not capture the altitude. The rate of descent was increased and the auto-pilot captured the glide slope.

At this time, the aircraft was entering the cloud deck, all anti-icing and de-icing systems were verified on, approach flaps were lowered and the gear was extended. Power was adjusted to approximately 600 ft. lbs. [torque] per engine in order to maintain 140 [k]nots IAS. From this point until the last few seconds of the flight I have no memory recall.

My next recollection is descending through 400 ft. AGL on the radar altimeter.

The aircraft did a sudden, uncommanded, skidding yaw to the left, with a following nose down, wing down roll to the left. My instinctive reaction was full right aileron, full right rudder, full power and nose up pitch. At this time I had visual outside the aircraft. The control input slowed the rate of roll and the aircraft started to return to level flight.

As I began to relax the controls [inputs], the rolling motion returned. At this time I could see a large, white space in front of me, and I could visually see that the aircraft was descending. I had full control input in, attempting to level the aircraft prior to impact. I do not recall the impact.

The two surviving passengers, one of whom was sitting in the copilot's seat, reported that the approach initially seemed normal to them, and that they could see objects on the ground at first (the reported weather at the time consisted of an obscuration with 1,100 feet vertical visibility). They reported that at some point after the point which ground objects became visible (none were visible directly out the front of the windscreen, according to the copilot's seat passenger), the aircraft suddenly rolled left and struck the ground. One passenger, who was sitting in the back of the aircraft (on the right side, across the aisle from the fatally injured passenger) at the time of the accident, reported that the aircraft rolled left, straightened out, then rolled left again (more severely) and struck the ground. The other passenger, who was sitting in the copilot's seat at the time, reported that the airplane rolled left and struck the ground approximately 2 to 3 seconds after the left roll, and that the aircraft rolled left despite the pilot moving the control yoke noticeably to the right. Both passengers reported briefly hearing what they thought was a warning horn of some type during the event, but could not recall noting any significant changes in the engine noise during the accident sequence.

The accident occurred during the hours of dusk, approximately 53 minutes after local sunset and 7 minutes before the end of the evening twilight (as computed by a U.S. Air Force astronomical data program), at approximately 40 degrees 45.1 minutes North and 111 degrees 58.4 minutes West.

PERSONNEL INFORMATION

The pilot was the chief pilot for the El Cortez Hotel in Las Vegas, and also flew part-time for Coast Hotels & Casinos, which owned the accident aircraft. He held an airline transport pilot certificate with airplane multiengine land rating, and was type-rated in the Cessna 500, Mitsubishi 300, and Beech 400 turbojet aircraft. The pilot was also a certificated flight instructor with airplane single engine and instrument instructor ratings. According to his accident report, he had 8,172 hours total time, of which 1,841 were in the Beech 200 aircraft. The pilot stated in an interview with investigators on April 28, 1997, that he received initial training on the type in 1986 and recurrent training on the aircraft in 1987, both from Flight Safety International of Long Beach, California. The pilot stated that he had not received any formal training of the Beech 200 since the 1987 recurrent training. He reported that his most recent pilot proficiency check was a pilot proficiency evaluation conducted in a Beech 400 jet aircraft simulator on April 6, 1996. The pilot stated during the April 28, 1997, interview that he had flown 39.8 hours in the Beech 200 (approximately 1/3 of which was instrument time) during the 6 months prior to the accident; and on his report of the accident, the pilot indicated that he had flown 61 total hours in the past 90 days, including 6 hours in the Beech 200, 20 hours at night, and 10 hours of actual instrument time.

Log book information supplied by the pilot indicated that he was current for night, instrument and multi-engine flight at the time of the accident, but had not flown into or out of Salt Lake City within the past 6 months.

AIRCRAFT INFORMATION

The Beech 200 has a maximum takeoff weight of 12, 500 pounds for operations under 14 CFR 91, and does not require a type rating to operate as pilot-in-command. The aircraft is approved for operation by a single pilot in operations under 14 CFR 91. The accident aircraft was found to be equipped with a Sperry SP-200 automatic flight control system with Sperry AZ-241 air data computer, a King KNC-610 area navigation system, and a Collins VIR-30A VOR/ILS receiver installed as NAV-1. The accident aircraft was not equipped with a cockpit voice recorder (CVR) or flight data recorder (FDR).

An estimated weight-and-balance computation for the aircraft at the time of the accident was performed by investigators. The following parameters were used for the computation: aircraft empty weight of 8,242 pounds (from aircraft maintenance records); pilot weight of 210 pounds (from FAA records); passenger weights of 210, 235, and 132 pounds (from surviving passenger interviews and medical examiner report); cargo weight of 360 pounds (weighed after accident); fuel load of 2,400 pounds at takeoff (reported by pilot); and estimated fuel burn of 983 pounds (based on reported time airborne and cruise fuel flow data in Raisbeck supplemental pilot's operating handbook.) Using these values, the estimated gross weight of the aircraft at the time of the accident was computed to be 10,811 pounds. Based on the above weights and reported aircraft loading, the aircraft was estimated to be within center of gravity limitations at the time of the accident.

The accident aircraft was modified in accordance with supplemental type certificates (STCs) held by Raisbeck Engineering INC. of Seattle, Washington. Modifications to the aircraft included installation of four-bladed Hartzell propellers, enhanced performance leading edges, a ram air recovery system in engine intakes, fully enclosed main landing gear doors, and dual ventral strakes on the aft fuselage. According to the FAA-approved Raisbeck supplemental pilot's operating handbook (POH) for the aircraft, a Raisbeck-modified Beech 200 at gross weight of 11,000 pounds and flaps extended 40% (the approach flap setting) has a stall speed of 81 knots calibrated airspeed (KCAS). At a density altitude of 3,700 feet (the computed Salt Lake density altitude at the time of the accident, based on reported temperature and altimeter setting), 81 KCAS was computed to correspond to a true airspeed of 86 knots. Based on the radar ground speed of the aircraft from the 1913:10 and 1913:14 radar returns (73 and 70 knots, respectively) and the wind reported by Salt Lake Tower to N117WM at the time of landing clearance (360 degrees at 15 knots), N117WM's true air speed at 1913:10 (immediately before it was recorded well below glide slope) was computed to be 88 knots, dropping to 85 knots at 1913:14 (at which time it was recorded well below glide slope)

The Raisbeck supplemental POH states that altitude loss experienced while conducting stalls in accordance with 14 CFR 23.201 was 800 feet. At 1913:10, the aircraft's altitude (as recorded by radar) was 4,700 feet or 478 feet above the TDZE of 4,222 feet.

The Raisbeck supplemental POH gives landing approach speeds at 11,000 pounds gross weight of 113 KIAS at 0% flaps, and 90 KIAS at 100% flaps.

According to the Beech 200 FAA-approved POH, the normal operating range of engine torque (marked by a green arc on the engine torque indicators) is 400 to 2,230 foot pounds.

The FAA-approved airplane flight manual supplement for the Sperry SP-200 automatic flight control system states that in the event of an autopilot malfunction, the autopilot may be disengaged by one of five different methods, or may be overpowered by the pilot. The supplement states that maximum altitude losses during malfunction tests were 80 feet for coupled ILS approaches.

According to the aircraft maintenance records, the airplane was on a manufacturer-approved airworthiness inspection program. No discrepancies were noted in the aircraft maintenance records regarding required inspections, to include the altimeter and static system tests required for IFR operations.

METEOROLOGICAL INFORMATION

An 1845 Salt Lake City SPECI observation gave the conditions as: obscuration with 1,300 feet vertical visibility; visibility 1 statue mile in light snow showers; temperature 1 degree C; dewpoint 0 degrees C; and wind 350 degrees at 23 knots.

The 1851 Salt Lake METAR hourly observation gave conditions as : obscuration with 1,100 vertical visibility; visibility 1/2 statute mile in snow showers; temperature 1 degree C; dewpoint 0 degrees C; and wind 340 degrees at 18 knots.

During N117WM's approach, Salt Lake Approach advised "lear seven whiskey mike" that the runway 34R RVR was out of service, and visibility was 1/2 mile. Salt Lake Tower advised N117WM at the time of landing clearance that winds were from 360 degrees at 15 knots.

Conditions reported in a Salt Lake SPECI observation taken at 1927, appro

(c) 2009-2011 Lee C. Baker. For informational purposes only.