Recent spate of accidents reinforces importance of following procedures

 - January 29, 2007, 10:08 AM

Why, when the safety record of professionally flown turbine twins is so impressive, did four business aircraft experience fatal accidents during a five-week period late last year? Three were fan-powered–a Learjet 35A, a Gulfstream III and a Challenger 601–and one was a King Air 200. There was a highly qualified two-person crew at the controls of each aircraft. Three of the four airplanes were operating in accordance with Part 91. Only the Challenger was operating under Part 135 regulations.

If you expect to find in this column an explanation of why these mishaps occurred, you will be disappointed. It probably will be months before the NTSB releases findings of probable cause.

But each accident offers a lesson for all aviators, even if not all the facts are available immediately. While the shock of four fatals within 35 days reverberates throughout our community, reminding even the most complacent that aviation safety can never be assumed, it provides an opportunity to reflect on what we do know.

On October 24 the King Air 200 collided with upsloping terrain after initiating a missed Localizer 30 approach to the Martinsville/Blue Ridge Airport (MTV) in Martinsville, Va., in IMC during daylight hours. (See December, page 6.) Reported weather at the time was 600 overcast, five miles visibility and calm winds, with a ground temperature of 57 degrees F. Minimum descent altitude for the LOC 30 approach at MTV is 1,340 feet (which equates to 415 feet agl), provided the pilot is receiving a DME signal, and the missed approach point (map) is one mile DME.

ATC initially advised the crew to expect a delay of about 30 minutes at 4,000 feet upon reaching the published holding pattern, which extends from the bales outer compass locator outbound along the localizer course. The aircraft received its approach clearance about the same time the crew reported entering its hold. The crew elected to continue its right-hand entry turn for the holding pattern and intercept the inbound localizer course, simultaneously initiating its descent for the approach and crossing abeam bales at 3,900 feet. The minimum descent altitude at bales, which is on the intermediate segment of the approach and 5.0 DME from the MAP, is 2,600 feet.

ATC radar indicated the aircraft gradually descended while on the final segment of the LOC 30 approach and leveled at 2,600 feet in the vicinity of the MAP. About one mile beyond the MAP, over the runway, the King Air began descending again while continuing on the inbound heading of 305 degrees rather than initiating a climbing right turn and returning to bales at 2,600 feet as specified by the missed approach procedure.

About three miles beyond the airport, the King Air descended to 1,800 feet, at which time ATC’s altitude readout was lost. About three minutes later the crew advised ATC that they were initiating a missed approach; ATC responded with clearance to climb to 4,000 feet and hold at bales. A few seconds later all communications with the aircraft ceased.

The Gulfstream accident also involved an approach in IMC. The aircraft struck a 156-foot-high pole located more than two miles from the threshold of Houston Hobby International’s Runway 04, which was served at the time by a functioning ILS, according to NTSB investigators. Weather conditions were reported as one-eighth of a mile visibility in fog, scattered clouds at 100 feet, ceiling 600 feet broken and 5,500 feet overcast. Just before the accident, ATC advised the Gulfstream crew that the aircraft’s altitude was 400 feet, which if correct was well below the glideslope.

These two approach accidents remind us of the necessity to follow procedures. Assuming that the avionics on the ground and in the aircraft were functioning properly, and there was no aircraft malfunction or other emergency, these accidents should not have happened. Yet they did. Why, and what can be learned from reviewing these accident scenarios?

Earlier on the same day as the King Air’s controlled flight into terrain accident near Martinsville, a Learjet 35 repositioning after a medevac flight also flew into terrain shortly after departing VFR from Brown Field Municipal Airport (SDM), near San Diego. Weather conditions at the time of departure, which was shortly after midnight, were overcast at 2,100 feet agl with eight miles visibility. The Learjet crew departed on Runway 08, maintained runway heading and was in communication with the Southern California Tracon, awaiting clearance for a previously filed IFR flight plan, when it struck the western slope of a mountain ridge at 2,256 feet msl.

Approximately one minute before the CFIT accident, Tracon radar identified the Learjet, gave the crew a discrete transponder code, instructed them to fly a heading of 020 degrees but to remain VFR, and to expect their IFR clearance above 5,000 feet. Tracon’s minimum safe altitude warning system sounded its alarm during the radar’s last two sweeps of the aircraft.

Departing VFR when weather or darkness impairs visual separation from obstacles is a procedure fraught with risk and should be used with extreme caution. Obtaining an IFR clearance before departure is certainly safer.

The fourth accident, a departure gone wrong of the Challenger at Montrose, Colo., which claimed three lives on November 28, is a stark reminder that nothing can be taken for granted. Snow was reported at Montrose Regional Airport along with one mile visibility and 1,100-foot ceiling, apparently a decision was made not to deice the Challenger, and stopping conditions on the 7,500-foot-long runway certainly were not optimum if the pilot attempted an abort.

As the NTSB conducts its investigations, more information will be available about these accidents, which accounted for the worst five-week period of business aviation accidents I can recall. Each should reinforce the need for strict adherence to procedures that minimize risk, and remind us that much can be learned from others’ mishaps.