Cessna 172N N109DP

Summary

On 4 July 2011 at about 19:30 local time, a Cessna 172N registered N109DP, operated by Gulf Coast Aerial Advertising Inc, was involved in an accident near Orange Beach, Alabama, United States. 2 people were on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

4 July 2011 at 19:30

Classification

Accident

Location

Orange Beach, Alabama, United States

Coordinates

30.2856, -87.5358

Aircraft

Cessna 172N

Registration

N109DP

Category

Airplane

Engines

1

Operator

Gulf Coast Aerial Advertising Inc

Operating rule

Part 91: General Aviation

Purpose of flight

Banner Tow

Phase of flight

Not recorded

Route

Foley → Foley

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

ERA11LA388

Nobody was injured.

The operation of the airplane using unapproved fuels, which resulted in abnormal combustion and subsequent damage to the No. 3 cylinder. Contributing to the accident was the inadequate 100-hour inspection because the mechanic failed to note the lack of placards by either fuel filler cap specifying the minimum automotive fuel grade and no alcohol allowed as specified by the installed STC’s.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

The airplane had been modified by several Supplemental Type Certificates (STCs) allowing the use of 91 minimum octane alcohol-free fuel, or a combination of 100LL and 91 minimum octane ethanol-free fuel. After takeoff while operating the engine on a mixture of 100LL and 87 octane automotive fuels with 10 percent ethanol additive, the engine experienced abnormal combustion in the No. 3 cylinder, which burned a hole through the cylinder near the lower spark plug hole. The resulting loss of engine power necessitated a forced landing in water. Postaccident examination of the engine revealed no discrepancies with the power train, ignition, lubrication, or air induction systems that would have led to the event. Metallurgical examination of the No. 3 cylinder revealed no manufacturing defects that would have damaged to the cylinder. No placards were noted by either fuel cap; these were required by the installed STCs specifying minimum octane rating of 91 without alcohol; however, on the day of the accident, the airplane underwent a 100-hour inspection by the pilot-in-command who held a mechanic certificate with airframe and powerplant ratings and inspection authorization; he had also performed the modification allowing the airplane to use automotive fuel. Although no fuel samples were retained for testing, the damage to the cylinder was consistent with the usage of unapproved fuel with too low an octane rating.

Quoted verbatim from the NTSB record.