On August 24, 1996, a Cessna 441 (registration N832AD) operated by Donald A. Fehrenbach was involved in an aviation accident near Phoenix, AZ. Investigators recorded the probable cause as: blockage of the fuel vent system due to mud from wasp nest(s). Inadequate maintenance was a related factor. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A pilot experienced uncommanded wing deice boot inflation at FL240, could not cycle them. At 5,000 ft MSL, a loud bang and jolt occurred, the right wing imploded, and aileron control was affected. Emergency landing followed. Postaccident examination revealed wasp nest mud blocking bleed air and fuel vents, and defective fuel cap components.
Flight Events
While cruising at flight level 240, the pilot observed that the wing deice boots were fully inflated despite not having activated them. He consulted the pilot operator handbook but was unable to cycle the boots. During descent, at approximately 5,000 feet mean sea level, a loud bang accompanied by a jolt occurred. The pilot noticed that the right wing had imploded or caved in, and that aileron control had been affected. He declared an emergency, was vectored to the nearest airport, and landed without further incident.
Postaccident Examination
Examination of the aircraft after the incident revealed several blockages in critical systems. The engine bleed air control valve overboard lines were both plugged with mud about 18 inches up inside from the overboard opening. Both NACA underwing fuel vents were found plugged with mud about 36 inches from the underwing opening. The mud originated from wasp nests. Additionally, secondary fuel vents were present in the fuel filler caps. The right fuel cap vent was 50 percent restricted due to a recent wing repaint. Both fuel cap flutter valves were defective. The aircraft had been parked outside for 30 days prior to the flight.