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ASN Wikibase Occurrence # 148028
Last updated: 18 June 2020
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Date:29-AUG-2012
Time:18:00
Type:Silhouette image of generic PA23 model; specific model in this crash may look slightly different
Piper PA-23-150 Apache
Owner/operator:Private
Registration: N1486P
C/n / msn: 23-555
Fatalities:Fatalities: 2 / Occupants: 2
Aircraft damage: Substantial
Category:Accident
Location:3 1/2 miles southwest of Canton, Lewis County, MO -   United States of America
Phase: En route
Nature:Private
Departure airport:Pinckeneyville, IL (PJY)
Destination airport:Blakesburg, IA
Investigating agency: NTSB
Narrative:
A witness, who was a private pilot, stated that he observed a twin-engine airplane flying overhead on a northerly heading. He reported that the airplane was about 2,000 feet above ground level in level flight and that the left propeller blades were not rotating. The accident site, located in an open field with obstacles, including rolling hills, woods, and roads, was about 6.5 miles from the private pilot’s location. Evidence indicated that the airplane struck a tree in a near wings-level attitude. Larger fields and flatter terrain with fewer obstacles were located northwest of the apparent route of flight (the airplane’s actual flight route was unknown), and, if the pilot had landed in one of these areas, he would have had a greater opportunity for a successful forced landing. However, the airplane was near or exceeded its maximum takeoff weight upon departure. According to the accident airplane’s climb chart, the airplane was unable to maintain altitude when the left engine lost power due to its excessive weight and single-engine performance, the existing high-density altitude (2,963 feet), and, possibly, the pilot's execution of single-engine flight procedures, which left the pilot fewer options to reach a more suitable landing location.
Evidence indicates that the left engine experienced a total loss of power. The spark plugs in the Nos. 1, 2, and 4 cylinders, which had fuel primer lines attached, exhibited carbon-fouling, indicating that a rich-fuel mixture existed at the time of the accident and that the pilot most likely unsuccessfully attempted to regain the left engine’s power by using the fuel primer to prime the cylinders.
The left wing gascolator bowl was removed and a blue silicon jell-type sealant was found covering about two-thirds of the area of the bowl's circumference and the area where a gasket is typically placed; however, no gasket was found in the gascolator. The blue silicon jell was consistent with Permatex Blue Silicon Gasket Maker, which has the following note in its directions: "NOTE: Not recommended for use on head gaskets or parts in contact with gasoline." If the gascolator seal is breached, air can enter the fuel system and possibly unport the carburetor, which would cause an uncommanded engine shutdown due to fuel starvation. The pilot was also an airframe and powerplant mechanic with inspection authorization. He performed the last annual maintenance inspection of the airplane and subsequent aircraft maintenance. He likely improperly used the blue silicon sealant during maintenance operations. 
Although the autopsy and toxicological examinations revealed that the pilot possibly had significant health issues, no evidence was found indicating that the pilot was incapacitated during the flight.
 
Probable Cause: The pilot's improper decision to attempt to execute a forced landing to an open field with obstacles. Contributing to the accident was the left engine’s total loss of power due to fuel starvation as a result of the introduction of air into the fuel system through a gascolator seal breach and the pilot’s use of an improper substance on the left wing gascolator bowl during maintenance operations, which led to the gascolator seal breach.

Sources:

NTSB: https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20120830X73434&key=1
http://www.whig.com/story/19413474/emergency-response-teams-responding-to-plane-crash-in-lewis-county
http://www.examiner.com/article/two-die-canton-mo-vintage-piper-pa-23-plane-crash

http://www.airport-data.com/aircraft/N1486P.html
https://flightaware.com/photos/view/741840-1bb0420f1b2c636596b7ea6bc04d11f190bb0264/aircrafttype/PA23


Revision history:

Date/timeContributorUpdates
29-Aug-2012 23:53 gerard57 Added
30-Aug-2012 13:34 gerard57 Updated [Aircraft type, Registration, Departure airport, Destination airport, Source]
30-Aug-2012 14:23 Geno Updated [Time, Cn, Location, Departure airport, Destination airport, Source, Narrative]
30-Aug-2012 16:56 Geno Updated [[Time, Cn, Location, Departure airport, Destination airport, Source, Narrative]]
30-Aug-2012 16:56 Geno Updated [[[Time, Cn, Location, Departure airport, Destination airport, Source, Narrative]]]
21-Dec-2016 19:28 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
28-Nov-2017 13:17 ASN Update Bot Updated [Operator, Other fatalities, Departure airport, Destination airport, Source, Narrative]

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