N402BPCessna 402B · 1973

On March 10, 2009, at 0740 central daylight time (cdt), a Cessna 402B, N402BP, piloted by a commercial pilot, was substantially damaged during a hard landing on runway 31 (6,901 feet by 100 feet, concrete) at the Aberdeen Regional Airport (KABR), Aberdeen, South Dakota. Instrument meteorological conditions prevailed at the time of the accident. The cargo flight was operating under the provisions of 14 Code of Federal Regulations (CFR) Part 135 on an instrument flight rules (IFR) flight plan. The pilot was not injured. The flight departed from Joe Foss Field Airport (KFSD), Sioux Falls, South Dakota, at 0639 cdt.

According to the pilot, the airplane encountered moderate icing conditions during initial climb to 8,000 feet mean sea level (msl). He requested and was subsequently cleared to climb to 12,000 feet msl due to the persistent icing conditions at 8,000 feet msl. The deice boots, pitot tube heat, stall vane heat, propeller deice, and windshield hot plate were used throughout the flight. The pilot stated that the wing deice boots functioned normally during the climb to cruise altitude. While at 12,000 feet msl, the airplane remained above the cloud tops and it did not accrue any additional ice while it remained at that altitude for about 20 minutes.

The pilot noted that the unprotected areas of the wings and windshield were still contaminated with ice when he initiated the descent into KABR. The unprotected areas of the airplane continued to accrue ice while being vectored to join the instrument landing system (ILS) approach to runway 31. The deice boots were cycled several times during the descent and instrument approach. The pilot reported seeing the runway approach lights about 3/4 mile from the runway threshold. The runway was partially obscured by blowing snow due to a strong crosswind. The pilot had difficulty aligning the airplane with the runway because the windshield was obscured by ice, except for a narrow section protected by the hot plate. The airplane crossed over the runway threshold at 120 knots indicated airspeed. The pilot stated that immediately prior to touchdown he had the sensation of a high sink rate, which was followed by the hard landing.

After the flight, there was 1 to 1-1/2 inch of ice accumulation on the unprotected areas of the airplane. The protected areas of the wing, tail, windshield, and propeller blades were free of any appreciable ice contamination. The right wing primary structure, including the main wing spar and engine nacelle assembly, was substantially damaged during the hard landing.

The destination airport was equipped with an automated surface observing system (ASOS). At 0746 cdt, the KABR ASOS reported: Wind 360 degrees true at 22 knots, gusting to 30 knots; visibility 1 mile with light snow and mist; few clouds at 600 feet above ground level (agl), broken ceiling at 1,400 feet agl, and overcast ceiling at 2,300 feet agl; temperature -16 degrees Celsius; dew point -18 degrees Celsius; altimeter setting 30.08 inches of mercury. The report noted a peak wind from 010 degrees true at 30 knots was recorded at 0737 cdt.

During the accident flight, there was an active advisory for instrument flight rules (IFR) weather conditions that encompassed the entire route of flight. The IFR advisory warned of ceilings below 1,000 feet agl and/or visibility below 3 miles in precipitation, mist, and fog. There was also an active advisory for moderate icing conditions below 15,000 feet msl and a freezing level at the surface. The pilot stated that before departure he reviewed the current weather conditions using a commercial computerized weather service. He noted that before departure he was fully aware of the icing advisory, as well as multiple pilot reports of icing conditions. He stated that based on available weather information, he expected to encounter light-to-moderate icing conditions while en route.

The Federal Aviation Administration (FAA) issued Type Certificate No. A7CE, on August 17, 1964, for the Cessna 402B airplane. According to the type certificate data sheet, the accident airplane, a 1973 Cessna 402B, s/n 402B0353, was certified under then Civil Aviation Regulations (CAR) Part 3.

Advisory Circular (AC) 91-74A, Pilot Guide: Flight In Icing Conditions, states that prior to 1973, small airplanes were approved for flight in icing if they were equipped with a minimum suite of ice protection equipment. The approval for flight in icing conditions was further discussed in Bureau of Flight Standards Release No. 434, issued November 2, 1959. Release No. 434 noted that the deicing equipment usually provided on "current models of non air-carrier airplanes cannot be expected to cope with heavy or prolonged moderate icing conditions. The latter can be expected to tax the equipment beyond its capacity."

In 1973, the FAA amended 14 CFR Part 23 to require analysis and testing to demonstrate if an airplane could safely operate in icing conditions. Although the accident airplane was built in 1973, it was manufactured in accordance with its previously issued type certificate. As such, the 1973 Cessna 402B model did not require analysis and testing to demonstrate its ability to safely operate in icing conditions. The 1973 Cessna model 402B Owner's Manual notes that the deicing systems do not provide adequate protection for the entire airplane, and thus "known icing conditions should be avoided whenever possible."

Beginning with the 1975 model year, the Cessna 402B, serial numbers 402B0801 and up, demonstrated its compliance with ice protection in accordance with 14 CFR Part 23.1419 of Amendment 23-14 effective December 20, 1973. Compliant airframes were manufactured with ice protection equipment in accordance with Cessna Drawing 5114400, Factory Kit No. 194. Earlier aircraft which have been modified in compliance with Accessory Kit No. 421-106 are considered to be equivalent to those with Factory Kit No. 194.

According to Cessna delivery documentation, the accident airplane was originally equipped with deice systems installed on both wings, and the horizontal and vertical stabilizers. Additionally, the airplane was equipped with electrically heated propellers, an alcohol deice windshield system for left and right windshields, fuselage ice protection plates, dual heated pitot tubes and static sources, electrically heated stall warning vane, and an ice-detection light system.

In 1996, the airplane's owner removed the factory installed alcohol windshield deice system, p/n 5114136-3, and installed an electrically heated windshield plate. The heated windshield plate was installed on the left windshield, leaving the right windshield unprotected. The corresponding FAA Form 337 noted that the installation did not allow the airplane to be flown into known icing conditions.

According to 14 CFR Part 135.227(c), Icing Conditions: Operating Limitations, an airplane is approved for flight into known or forecast light or moderate icing conditions if one of the following applies:

(1) The aircraft has ice protection provisions that meet part 135, appendix A, paragraph 34.

(2) The aircraft has ice protection provisions that meet the requirements for transport category airplane type certification.

(3) The aircraft has functioning deicing or anti-icing equipment protecting each propeller, windshield, wing, stabilizing surface, control surface, airspeed instrument, altimeter, rate of climb instrument, and flight attitude instrument system.

After the accident, the FAA evaluated the accident airplane’s compliance with 14 CFR Part 135.227(c). The FAA determined that the accident airplane did not meet the regulatory requirements set forth in 14 CFR Part 135.227(c) because the right windshield was not equipped with deicing or anti-icing equipment.

During the accident investigation, the National Transportation Safety Board (NTSB) investigator-in-charge asked the FAA what criteria is used to determine if deice and/or anti-icing equipment, certified prior to 1973, will provide adequate protection to ensure the safety of flight in light-to-moderate icing conditions during 14 CFR Part 135 operations. The FAA responded that the only requirement for airplanes certified prior to 1973 was to have associated equipment listed in 14 CFR Part 135.227(c)(3) be operationally functional. Compliance with this requirement would be satisfied by a functional test upon installation and prior to dispatch on each flight.

On March 24, 1997, Cessna issued mandatory service bulletin MEB97-4 that cited several affected aircraft models and serial number ranges, including the subject airplane. The service bulletin called for the installation of a placard stating "Flight In Known Icing Is Prohibited" within 100 hours or 3 months, whichever occurred first. The service bulletin noted that the affected airplanes may have been "originally equipped with anti-ice and/or deice equipment that could make the airplane appear to be certified for flight in known icing conditions when in actuality it is not." The service bulletin further states that failure to avoid flight in known icing conditions can result in adverse performance/flight characteristics of the airplane that could result in serious injury and/or death to the pilot, crew, and/or passengers.

The accident airplane was operated by the current owner when service bulletin MEB97-4 was issued. The operator contended that compliance with the service bulletin was not required because it was not an airworthiness directive. Additionally, the operator contended that the airplane was equipped with the deice/anti-ice systems required by 14 CFR Part 135.227, and guidance for their operation was included in the company's Operation Manual and training modules.