Accident Cessna 501 Citation I/SP N804ST,

ASN Wikibase Occurrence # 320074

Date:	Monday 23 May 2016
Time:	21:56
Type:	Cessna 501 Citation I/SP
Owner/operator:	Eagle II Aero LLC
Registration:	N804ST
MSN:	501-0146
Year of manufacture:	1980
Total airframe hrs:	7424 hours
Engine model:	Williams International FJ44-2A
Fatalities:	Fatalities: 0 / Occupants: 4
Aircraft damage:	Substantial, written off
Category:	Accident
Location:	near Texarkana, AR - United States of America
Phase:	En route
Nature:	Private
Departure airport:	Perryville Municipal Airport, MO
Destination airport:	San Antonio International Airport, TX (SAT/KSAT)
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
A Cessna 501, N804ST, lost cabin pressurization during cruise at flight level 430 and entered an uncontrolled descent near Texarkana, Arkansas. The pilot regained consciousness and control of the airplane about 7,000 feet mean sea level and landed without further incident. The airplane sustained substantial damage to both wings due to the excessive loads on the wings during the descent/recovery. The pilot and two passengers sustained minor injuries and one passenger was uninjured.
Night meteorological conditions prevailed at the time of the accident.

Post-accident examination of the airplane revealed that the primary pressurization duct into the cabin was separated from its connection to the water separator. The duct's metal retaining clamp was present with its retaining screw in place. The clamp was not fractured and was resting around the metal duct leading to the separator.

PROBABLE CAUSE: "The pilot's failure to use supplemental oxygen as required during high-altitude flight, which resulted in his loss of consciousness following a loss of cabin pressurization. Contributing to the accident was the separation of the air conditioning system's primary pressurization duct and the subsequent failure of the aft pressure bulkhead check valve flapper due to progressive weakening from age."

Accident investigation: