NTSB Identification: SEA97LA030.
The docket is stored in the Docket Management System (DMS). Please contact Records Management Division
Accident occurred Tuesday, November 19, 1996 in OLYMPIA, WA
Probable Cause Approval Date: 08/21/1997
Aircraft: Cessna 421B, registration: N8005Q
Injuries: 3 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The pilot stated that during climbout on an IFR flight, he frequently checked the wings for ice accumulation, noting what appeared to be a 'mere' trace of ice. At about 13,000 feet msl, with almost no climb at 125 knots indicated airspeed, the pilot pulled the yoke back a little to climb, and the aircraft began to shudder. The pilot then decided to divert, again checking the wings, seeing what he described as a trace of ice. He said he cycled the deice boots with no apparent change in wing appearance. While on approach, he again cycled the boots between 3000 and 2000 feet msl. The pilot stated that about 20-30 feet above the surface, he started a slight roundout, but when he eased back on the yoke, the airplane shuddered and the nose did not raise. At that point, he was ready to touch down, so he pulled back on the yoke while adding power; however, the airplane landed hard and was damaged. Later, the surface deice system was tested. The boots did not hold pressure due to multiple wing boot holes and a shuttle valve internal leak. Functional tests revealed that the control valves did not direct proper pressure to the system, and that the shuttle valves did not direct pressure properly to the boots (there was leakage to the vacuum side of the valves).

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

inoperative deicing equipment, due to multiple wing boot holes and malfunctioning control/shuttle valves; subsequent build-up of airframe (wing) ice; and failure of the pilot to maintain adequate airspeed during the flare for landing. Factors relating to the accident included: the adverse weather (icing) conditions, and inadequate maintenance concerning the deicing equipment.

Full narrative available

Index for Nov1996 | Index of months