BILLINGS, MT, USA
N691A
Short Brothers SD3-60
The Short Brothers SD3-60 cargo flight was being vectored for the VOR/DME RWY 28R approach to the Billings Logan International airport during instrument meteorological conditions. Weather conditions one minute before the accident were winds 020 at 13 knots, light snow and mist, and visibility was deteriorating rapidly. The co-pilot (occupying the right seat) was flying the aircraft, and the PIC (occupying the left seat) was handling radio communications. At 0812:25, having crossed the final approach fix, the aircraft descended through 100 feet above the MDA (3,940 feet or 426 feet above the runway threshold), and immediately thereafter the crew visually acquired the runway. At 0813:01 the aircraft's GPWS alert of 'SINK RATE' was heard, followed 2 seconds later by the PIC calling for 'POWER,' and a 2 second delay to ground impact. The co-pilot had logged a total of 103 hours in the SD3-60 (all within the previous 90 days,) while the PIC had just begun flying the aircraft in Montana's late fall weather after a 6 year assignment flying in the Hawaiian islands. The left main landing gear collapsed in overload during the ground impact.
HISTORY OF FLIGHT On November 25, 1997, at 0813 mountain standard time, a Short Brothers SD3-60, N691A, operated by Corporate Air, and crewed by an airline transport pilot-in-command (PIC) and a commercially rated first officer (co-pilot), was substantially damaged when the left main landing gear collapsed on landing at the Billings Logan International airport, Billings, Montana. Both pilots were uninjured. Instrument meteorological conditions existed at the time, and an IFR flight plan was in effect. The flight, which was an unscheduled, domestic cargo flight from Great Falls, Montana, to Billings, was to have been operated under 14CFR121, and departed Great Fall approximately 0715. The flight, Airspur 814, departed Great Falls and upon approaching Billings was given a vector to fly 100 degrees (magnetic) for the VOR/DME RWY 28R approach. The aircraft was subsequently stepped down to 5,700 feet MSL (procedure turn/ARC minimum altitude - refer to DIAGRAM I) and given a heading of 140 degrees. At 0806:56, the aircraft was given a right turn to 180 degrees and shortly thereafter the crew received ATIS information "Charlie" (refer to CVR Report and ATTACHMENT AT-I) At 0808:17, Billings approach control advised Airspur 814 "four miles from Musty (final approach fix), turn right heading 290, maintain 5,700 till established on the final approach course, cleared for the VOR/DME runway 28R approach." At 0809:08, Billings approach control advised Airspur 814 "I show you two miles from MUSTY now, you gonna be able to intercept OK?" The PIC acknowledged "yeah, it's fine for us" and the controller then switched the flight to the Billing ATCT (air traffic control tower). At 0809:38, Airspur 814 contacted Billings ATCT advising "we're one from MUSTY now on the VOR/DME runway 28 right" and the aircraft was cleared to land. At 0811:20, the Billings ATCT advised Airspur 814 "traffic on the roll now is a Beech airliner" which was acknowledged by the PIC. At 0810:14, the aircraft's cockpit voice recorder (CVR) recorded "and there's MUSTY and we're just about on course, 3,940 right?" which was confirmed. Over the next two minutes the CVR recorded the two pilots executing the landing checklist. At 0812:25, the aircraft's CVR recorded "hundred to minimums, instruments are normal and we've got uh, less than a mile to go." Ten seconds later the CVR recorded "there's minimums, thirty nine hundred (unintelligible), I got the ground...that's about it" followed by "there's the runway." At 0812:49, the aircraft's CVR recorded "got it, should we land?" followed by "yeah, go ahead." At 0813:01, the aircraft's CVR recorded "sink rate" generated by the aircraft's ground proximity warning system (GPWS), followed one second later by an intermittent warning horn and vibrating sound. At 0813:03, the aircraft's CVR recorded the PIC calling "power, power, power" followed one second later by a sound similar to an increase in propeller RPM, and one second later by the sound of impact. PERSONNEL INFORMATION PIC: The PIC reported a total of 8,850 flight hours of which 8,200 were logged as pilot-in-command and 2,800 hours were logged (all pilot-in-command) in the SD3-60 aircraft. Federal Aviation Administration (FAA) records showed he had received a type rating in the SD-3 series aircraft. The PIC, who was handling the aircraft radios at the time of the accident, occupied the left seat in the cockpit. The PIC's most recent first class medical exam was conducted 11/03/97 and showed an address of Ewa Beach, Hawaii. According to personnel at Corporate Air, the PIC had been hired by the company in 1987 and flew out of Grand Forks, Nebraska. He was subsequently transferred to Honolulu in September 1991 where he flew the SD3-30/60 aircraft. He was reassigned to Billings in September of 1997 attending ground school and completing his final PIC check flight in the SD3-60 aircraft on 11/17/97, eight days before the accident. CO-PILOT: The co-pilot reported a total of 1,484 flight hours of which 511 were logged as pilot-in-command and 103 hours were logged (all co-pilot within the last 90 days) in the SD3-60 aircraft. The co-pilot, who was flying the aircraft at the time of the accident, occupied the right seat in the cockpit. WRECKAGE AND IMPACT INFORMATION The aircraft first touched down on runway 28R in the vicinity of the taxiway "B" intersection and continued down the runway coming to rest off the south side of the runway in the taxiway "D" throat area (refer to DIAGRAM II). Post-crash examination revealed that the left main landing gear assembly had broken and the left stub wing had contacted the ground (refer to photograph 1). The left wingtip was observed to have ground contact scratches and the underside of the fuselage was observed to be buckled in compression (refer to photographs 2 and 3). METEOROLOGICAL INFORMATION The Billings aviation surface weather observations reported the following conditions at the noted times: 0803 special observation: Wind 010 true at 11 knots, visibility 2 statute miles, light snow and mist, sky condition 300 foot scattered, ceiling 900 foot broken, 1,600 foot overcast, temperature 01 degrees C., dew point 0 degrees C., altimeter 29.88 inches Mercury. 0812 special observation: Wind 030 true at 13 knots, visibility 1/2 statute mile, light snow and mist, sky condition 200 foot scattered, ceiling 700 foot overcast, temperature 1 degrees C., dew point 0 degrees C., altimeter 29.86 inches Mercury. 0825 special observation: Wind 010 true at 10 knots, visibility 1/4 statute mile, snow and fog, ceiling 200 foot broken, 700 foot overcast, temperature 0 degrees C., dew point 0 degrees C., altimeter 29.87 inches Mercury. At 0807:15, the flight crew of Airspur 814 received the following ATIS (Automatic Terminal Information Service)radio transmission: "Information Charlie; 1454 zulu; wind 350 at 11; visibility 3, light rain, snow and fog; 500 scattered; ceiling 1,600 broken; 3,000 overcast." At 0809:54, the flight crew of Airspur 814 received the following weather information in a radio transmission from the Billings ATCT: "Wind is 010 at 11." The climatological conditions in central Montana, as characterized by the previously documented aviation surface weather observations (crosswinds, snow, freezing temperatures and low ceilings) are substantially different from those characteristic of the Hawaiian Islands (relatively constant easterly trade winds, warm temperatures, and rain showers). COMMUNICATIONS A request to the FAA for a formal air traffic package including radar data was made following the accident, but was not provided (refer to ATTACHMENT ATR-I). A written transcript of radio communications between the Billings approach control/ATCT facility and the flight crew of Airspur 814 was provided and is included (refer to ATTACHMENT CT-I). AERODROME INFORMATION The Billings Logan International airport is served by three runways of 5,500 feet or less in length, along with a single 10,528 foot long, asphalt runway (10L/28R). Runway 28R/10L provides all the non-circling instrument approaches into Billings and is 150 feet in width (refer to DIAGRAM II). The only precision approach at Billings is an ILS to runway 10L. Both ends of the runway are served by non-precision approaches. The VOR/DME RWY 28R approach is a non-precision approach and is predicated upon the Billings VOR located 4.6 nautical miles west of the threshold of runway 28R, and 10.1 nautical miles from MUSTY intersection, the initial/final approach fix for the VOR/DME RWY 28R approach (refer to DIAGRAM I). FLIGHT AND COCKPIT VOICE RECORDERS The aircraft was equipped with a CVR (cockpit voice recorder) and an FDR (flight data recorder). The CVR was read out at the NTSB's Vehicles Recorder Division, Washington, DC. A written transcript of the recording between 0806:36 until 0813:05 mountain standard time was provided (refer to Specialist's Factual Report of Investigation - CVR Report). A readout of the FDR data was attempted at the NTSB's Vehicles Recorder Division, Washington, DC. However, the data could not be accurately correlated with the accident flight. No useful FDR data were obtained (refer to Specialist's Factual Report of Investigation - FDR Report). ADDITIONAL INFORMATION The aircraft's CVR (serial number 26336) and FDR (serial number BF5107) were returned to the owner/operator from the NTSB's Vehicles Recorder Division, Washington, DC, in April 1998.
The co-pilot's failure to maintain the proper descent rate on final approach, the pilot-in-command's delayed remedial action, and overload of the left main landing gear assembly. Factors contributing were snow, crosswind conditions and deteriorating visibility.
Source: NTSB Aviation Accident Database
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