On November 27, 1984, a Cessna 421B (registration N41097) operated by Skytrak Aviation was involved in an aviation accident near Mason City, IA. Investigators recorded the probable cause as: The pilot's decision to fly into known icing conditions in an aircraft not certified for such operations, which resulted in ice accumulation that the deicing system could not remove, leading to a stall during landing. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A pilot aware of surface icing risks flew into the area, resulting in a stall at 30 feet during landing. The manufacturer states the aircraft is not certified for flight into known icing conditions.
What happened
The ATP pilot-in-command was fully aware that the flight would encounter an area of surface icing. Despite this knowledge, the aircraft continued its approach. During the final phase of the landing, while over the runway at approximately 30 feet above the ground, the aircraft stalled and impacted the runway hard.
The investigation
Examination of the aircraft revealed that the boots on the horizontal stabilizer did not remove ice effectively during the flight. Deicing and anti-icing equipment had been installed at the factory during the manufacturing process, yet it failed to prevent the accumulation that led to the stall.
Findings
The manufacturer states that this specific aircraft type cannot be certified for flight into known icing conditions. The failure of the deicing system on the horizontal stabilizer contributed directly to the loss of control at a critical altitude.
Probable cause
The pilot's decision to fly into known icing conditions in an aircraft not certified for such operations, which resulted in ice accumulation that the deicing system could not remove, leading to a stall during landing.