Saturday, November 1, 2008
Take weather briefings seriously
There’s never been so much pre- and in-flight weather information available for pilots. If you can’t gather the raw data, forecasts and current airport observations by yourself, a briefer at a Flight Service Station (FSS) can do it for you. Unfortunately, some pilots continue to experience trouble applying the wealth of data and meteorological analyses to the realities of flight. Investigators often find that clues about what a flight would later encounter were readily available in a preflight weather briefing. In some cases, the pilot being briefed seemed to show an understanding of what he or she was being told, yet the import didn’t register. Earlier this year, the NTSB finished investigating some accidents involving weather encounters.
At 9:04 p.m. on February 16, 2007, a Cessna 340A crashed 3 nm south-southeast of Council Bluffs Municipal Airport (CBF) in Council Bluffs, Iowa. The Part 91 business flight was operating on an IFR flight plan; night instrument meteorological conditions prevailed. The pilot and all three passengers were killed. The flight left Northwest Arkansas Regional Airport in Fayetteville, Ark., two hours prior to the crash. Earlier that day, the aircraft flew from CBF to Jasper County Airport (JAS) in Jasper, Texas, with an intermediate fuel stop at Fort Smith Regional Airport in Fort Smith, Ark.
Investigators determined that an FSS weather briefer had informed the pilot that the flight might encounter moderate icing conditions and turbulence. The 1977 Cessna 340A was equipped with inflatable deice boots to provide in-flight icing protection. Knowing this, it’s possible that the pilot discounted the importance of the icing forecast.
The first leg of the return flight departed JAS at 5:29 p.m., stopped at Fort Smith for fuel and then departed for CBF. At 8:43:56 p.m., the flight established radio contact with Omaha Terminal Radar Approach Control (TRACON), and the pilot reported that the airplane was level at 11,000 feet. The flight was cleared to descend, at the pilot’s discretion, to 5,000 feet and proceed to the Omaha VOR. The pilot requested the VOR-A approach into CBF. The controller told the pilot about reports of light to moderate icing below 9,000 feet, and cleared the pilot to maintain 3,000 feet until established on the approach. At 8:55:34 p.m., the pilot leveled at 3,000 feet, at which time the aircraft was 15 miles south of the airport. The controller released the pilot to CBF’s CTAF at 8:58:20 p.m.; the flight was 10 miles south of CBF at that time. No further communications were received from the airplane.
The pilot held an ATP certificate with single-engine and multi-engine land ratings. He had a flight-instructor certificate with single-engine, multi-engine and instrument ratings, as well as a ground instructor certificate with an advanced rating. The pilot’s first-class medical certificate had no restrictions or limitations. Investigators determined that the pilot had accumulated about 3,275 hours of total flight time.
Weather conditions recorded shortly after the accident by CBF’s AWOS, located about three miles north of the accident site, indicated wind from 330 degrees at 25 knots, gusting to 36 knots; visibility at ¾ mile in unknown precipitation; an overcast cloud ceiling at 1,000 feet AGL; temperatures of minus-1 degree C; a dew point of minus-3 degrees C; and altimeter at 29.61.
An AIRMET issued five hours before the accident warned of moderate turbulence below 18,000 feet, with conditions ending in the vicinity of the accident site around the time of the crash. The AIRMET also warned of the potential for low-level wind shear, with conditions continuing well beyond the time of the accident. Another AIRMET noted the possibility of moderate icing below 16,000 feet until 1:00 a.m. National Weather Service data indicated that the probability of icing increased between 9,000 feet and 3,000 feet, with a greater than 70% probability of icing conditions. The data was consistent with a high probability of moderate to likely severe icing conditions in the area of the accident.
The NTSB determined that the probable cause of the accident was the pilot’s continued flight into adverse weather, and his failure to maintain altitude during the instrument approach. Contributing factors were the presence of severe icing, moderate turbulence and low-level wind shear.
At 9:10 a.m. on April 21, 2007, a twin-engine Piper PA23-250 crashed into the Atlantic Ocean, about 26 miles east of Fort Lauderdale, Fla. Instrument meteorological conditions prevailed; a VFR flight plan had been filed for the Part 91 flight from Fort Lauderdale Executive Airport (FXE) to Fresh Creek Airport (YAF) on Andros Island, Bahamas. The airplane was destroyed and the certificated private pilot and the four passengers were killed.
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