Flight History
On February 1, 2010, at about 1512 eastern standard time, a Cessna 402C, registration N121PB, operating as Cape Air flight 1805, was substantially damaged during a runway overrun at Watertown International Airport (ART), Watertown, New York. The airline transport pilot and the six passengers were not injured. Marginal visual meteorological conditions prevailed, and an instrument flight rules flight plan was filed for the scheduled passenger flight under 14 CFR Part 135.
The flight departed Albany International Airport (ALB) and was destined for ART. The initial cruise altitude was 6,000 feet msl, and the flight was subsequently cleared to 7,000 feet msl to remain above clouds. As the flight approached ART, air traffic control issued radar vectors for the instrument landing system approach to runway 7, cleared it to descend to 3,600 feet msl, and then to 2,000 feet msl. The airplane descended out of the clouds at 2,600 feet on a northwest heading, and the pilot sighted the airport about 7 miles northeast. He requested and was cleared for a visual approach to runway 25.
As the airplane descended to traffic pattern altitude, the pilot noticed the airspeed decrease from 140 knots to 85 knots. He pushed the nose down and applied maximum engine power but observed no increase in airspeed. He continued towards the airport at 85 knots indicated. Clouds and snow squalls obscured the runway; he elected to land on runway 7 by overflying the airport and entering a modified left-hand traffic pattern. He considered climbing to troubleshoot the airspeed anomaly but decided to land due to weather. The airplane was responsive to flight controls and did not feel near stall. He did not cross-reference the right-side airspeed indicator and did not report anomalies to ATC.
On a tight left base leg for runway 7, he extended flaps to 15 degrees and gear, resulting in airspeed reduction. He turned onto final between 300 and 400 feet agl; the airspeed indicator still showed 85 knots but he felt groundspeed was higher. On short final, he extended flaps to at least 20 degrees. The airplane touched down about 1,000 feet beyond the threshold, bounced slightly, and nose gear contacted mid-field. After nose gear touchdown, braking action was nil. The airplane departed the paved surface onto snow-covered terrain. The pilot secured switches and may have inadvertently turned off pitot heat and stall warning vane heat. Airport personnel later said there was about 1/2 inch of snow on the runway.
Personnel Information
FAA records showed the pilot held an airline transport certificate with single- and multi-engine land ratings and several type ratings. His most recent first-class medical was issued November 2009. He had 8,223 total flight hours, including 1,374 hours in the accident make and model, 132 hours in the preceding 90 days, and 33 hours in the preceding 30 days.
Aircraft Information
The airplane was manufactured in 1981 and first registered to Hyannis Air Leasing in 1992. It was equipped with two Teledyne Continental TSIO-520 series 325-hp piston engines and three-bladed metal propellers. The most recent inspection was January 23, 2010, with 35 hours since. Total time was 27,611 hours; left engine 2,456 hours; right engine 2,273 hours. The airplane was not equipped with anti-skid braking or reversible-pitch propellers.
Meteorological Information
The 1512 automated observation at ART reported wind from 240 degrees at 10 knots, visibility 3 miles in light snow, scattered clouds at 2,400 feet, broken at 3,500 feet, overcast at 4,700 feet, temperature -6°C, dew point -7°C, altimeter 30.16 inches of mercury. Continuous snowfall began about 2 hours prior.
Airport Information
ART was a non-towered airport with runways 07-25 (grooved asphalt, 5,000 by 150 feet, elevation 325 feet msl) and 10-28. Three instrument approach procedures were published for runway 7; none for other runways.
Wreckage and Impact Information
The airplane came to rest 366 feet beyond the departure end of runway 7, upright, with all three landing gear collapsed or fractured. Main gear tires were flat-spotted. The nose gear area had crush and tearing damage. All six propeller blades were bent aft. The pitot tubes remained attached but were buried in snow. About 600 pounds of fuel remained. Cockpit switches for de-ice boots, stall warning vane, leading edge light, and pitot heat were in the OFF position; they were located close together on the left panel.
Two airspeed indicators were installed, each plumbed independently to a dedicated pitot tube and static ports. A single pitot heat switch controlled both tubes; the system was field-tested and both tubes warmed when switched on. Post-accident, the right pitot tube was pressurized; the ASI moved to maximum and no leaks were detected. The left pitot tube had a severed plastic line at a deformed structure; pressurizing yielded movement and no leaks. No further examination was performed.
Additional Information
According to the pilot's operating handbook, an independent second pitot system was used when copilot instruments were installed. Pitot heat for the additional head was controlled by an adjacent switch. In the event of an airspeed indicator anomaly, the POH stated that if only the airspeed indicator was affected, pitot tube blockage was likely; if icing was possible, activating pitot heat would clear it. The POH instructed referencing copilot instruments or optional angle-of-attack indicator; if not equipped, fly by attitude and power. It was not determined if the accident airplane had an angle-of-attack indicator. No service bulletins regarding the pitot-static system existed.
The pilot had heard of a previous similar anomaly in a newly-painted airplane attributed to paint chips. The accident airplane was painted on November 4, 2009, and had flown 336 hours since. The operator had no records of pitot-static malfunctions from paint chips.