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N82383 accident description

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Crash location 42.569723°N, 83.778334°W
Nearest city Brighton, MI
42.529477°N, 83.780221°W
2.8 miles away
Tail number N82383
Accident date 01 Sep 2012
Aircraft type Aeronca 7AC
Additional details: None
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NTSB Factual Report

HISTORY OF FLIGHT

On September 1, 2012, approximately 0830 eastern daylight time, an Aeronca 7AC single-engine airplane, N82383, sustained substantial damage when it impacted terrain following a loss of control during initial takeoff climb from the Brighton Airport (45G), Brighton, Michigan. The private pilot sustained serious injuries, and the passenger sustained fatal injuries. The airplane was registered to and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed and a flight plan was not filed. The local flight was originating at the time of the accident.

According to local authorities who spoke to witnesses, the pilot was taking the passenger for a local flight. Witnesses observed a normal engine run-up prior to takeoff, and a normal takeoff from runway 22. Shortly after takeoff, the engine did not sound like it was developing full power and the airplane was struggling to climb. Subsequently, witnesses observed the airplane make a 180-degree turn and then descend toward the terrain in a nose down attitude.

PERSONNEL INFORMATION

The pilot, age 79, held a private pilot certificate with ratings for airplane single-engine land, airplane multi-engine land, and instrument airplanes. The pilot held a valid driver's license for operation of light-sport aircraft. The pilot's most recent third class medical certificate was issued on August 10, 2005.

The Aeronca 7AC is defined by Federal Aviation Administration (FAA) as a light sport aircraft (LSA). Pilots flying LSAs are only required to possess a valid driver's license and comply with 14 Code of Federal Regulations 61.53(b), which states that no person may act "as pilot in command, or in any other capacity as a required pilot flight crewmember, while that person knows or has reason to know of any medical condition that would make the person unable to operate the aircraft in a safe manner."

A review of the pilot's logbook showed the pilot had accumulated 2,686.5 flight hours, and 7.8 hours in the last 60 days. The pilot's most recent flight review was completed on August 4, 2012.

AIRCRAFT INFORMATION

The Aeronca 7AC, serial number 7AC-1016, was manufactured in 1946, and registered to the owner on June 10, 2008. The airplane was a two place, tandem, high wing monoplane. Basic construction consisted of welded tubes, and a fabric covered fuselage. The airplane was powered by a Continental A-65-8, 65-horsepower reciprocating engine and a fixed pitch wood propeller. The pilot's operating handbook listed a clean stall speed of 38 miles per hour (mph).

Review of the maintenance records showed that the most recent annual inspection was completed on November 22, 2011, at a total time of 2,391.5 hours. At the time of the accident, the airplane had accumulated 27.2 hours since the annual inspection.

Although the airplane held a standard airworthiness certificate, it met the definition of a Light Sport Aircraft as contained in 14 Code of Federal Regulations Part 1.1.

According to friends of the pilot, the pilot routinely fueled the airplane with automotive gasoline. The airplane records did not show the supplemental type certificate (STC) for the use of automotive gasoline. According to an Experimental Aircraft Association flight manual supplement, "When using unleaded automotive gasoline, the onset of carburetor ice may occur earlier under the same atmospheric conditions then when using 80/87 minimum grade aviation gasoline. There is no change in the techniques for recognizing and correcting for carburetor ice."

According to weight and balance information contained in the airplane's maintenance records, the airplane had an empty weight of 765.5 pounds (lbs), and a maximum allowable gross weight of 1,220 lbs. Medical records indicated the pilot/owner's weight was 176 lbs, and the autopsy report listed the passenger's weight as 127 lbs. The total fuel on-board at the time of the accident was unknown. Based on the occupant weights, the remaining useful load without fuel was 151 lbs. The total fuel capacity for the airplane was 13 gallons (or 78 lbs).

On November 10, 2010, Aero Fabricators shoulder harness and seat belt assemblies were installed in the front and rear seats per STC number SA1768GL, and Aero Fabricators Installation Instructions AF-41. Aero Fabricators was issued STC SA1768GL for shoulder harness and seat belt assembly on July 1, 1992.

According to an individual who owned a hangar near the pilot's hangar, during the most recent annual inspection, the pilot prepped the airplane for the inspection, which included the removal of the seats and lap restraints. Upon completion of the annual inspection, the seats and lap restraints were reinstalled by the pilot.

METEOROLOGICAL INFORMATION

At 0815, the Livingston County Airport (OZW), Howell, Michigan, automated weather observing system, located 9 miles west of the accident site, reported calm wind, visibility 10 miles, clear sky, temperature 19 degrees Celsius, dew point 13 degrees Celsius, and an altimeter setting of 30.15 inches of Mercury.

The FAA icing probability chart indicated there was potential for serious carburetor icing at glide power at the time of the accident.

AIRPORT INFORMATION

Brighton Airport was a non-towered, public-use airport equipped with one runway oriented in a 04/22 configuration. According to FAA records, runway 04/22 measured 3,120 feet in length and 24 feet in width. Obstructions included 48-foot trees 700-feet from the end of runway 22.

WRECKAGE AND IMPACT INFORMATION

The airplane came to rest upright in swampy terrain approximately 1,000 feet from the departure end of runway 22. The engine was found buried within the terrain and displaced aft into the firewall. The fuselage was crushed upward and aft. The empennage was partially separated and displaced to the right.

Examination of the airplane showed that flight control continuity was established from all flight control surfaces to the cockpit area. The wooden propeller remained attached to the engine and displayed leading edge gouges and splintering. The crankshaft was rotated by hand and continuity was confirmed from the propeller to the rear accessory gears and to the valve train. The carburetor remained partially attached to the engine, but was impact damaged. The carburetor float bowl contained fuel and water. The carburetor float was undamaged, and the fuel intake screen was clear. The carburetor heat control at the engine was found in the OFF position.

MEDICAL AND PATHOLOGICAL INFORMATION

Pilot Injuries

Accident site photographs, medical records, as well as autopsy, and toxicological reports were reviewed by the National Transportation Safety Board (NTSB) Chief Medical Officer, in an effort to determine the extent and severity of the pilot's injuries.

According to medical records released to the NTSB by the pilot's family, the pilot was found with a decreased level of consciousness, responding only to painful stimulation. On arrival to the hospital, the following injuries were identified: a posterior dislocation of his left hip prosthesis with a fracture of the hip socket (acetabulum), a fracture of his left elbow (olecranon), bruising of the soft tissue around his right eye with a fracture of the floor of the orbit, compartment syndrome in his right forearm, and "bruising over bilateral shoulders, right greater than left with associated right sided bruising over lateral chest, abdomen, hip"; the physician notes remarked "seatbelt sign". According to Computerized Tomography (CT) scan of his head, he had bleeding around and swelling within his brain.

Passenger Injuries

An autopsy was performed on the passenger by the Sparrow Forensic Pathology facility, Lansing, Michigan. According to the autopsy report, the cause of death was "multiple injuries."

SURVIVAL ASPECTS

Pilot Seat

The pilot seat was found with its four seat posts attached to the aircraft floor, and the seat frame was bent down, forward, and to the right.

Pilot Restraint

The pilot restraint was manufactured by Aero Fabricators (model number H-702-300) and installed on the accident airplane on November 11, 2010. The restraint was manufactured on May 27, 2010. The shoulder harness label stated the restraint system was a FAA-PMA part with a "rated strength of assembly [of] 1,500 pounds."

The lap belt was attached to the seat at the back seat posts. The lap belt fitting was pinned between the installation bolt and the seat frame, which prevented the lap belt from swiveling forward and aft. The lap belt webbing was pinned between the lap belt fitting and the seat frame, which prevented the seat belt from being able to be adjusted for proper fitting. The left side lap belt had been cut by rescue personnel, and the tongue end of the lap belt was missing from the wreckage.

The shoulder harness had been removed from the airplane by FAA inspectors. The shoulder harness was separated at the stitched "Y" junction that connected the two shoulder straps and the fuselage attach strap behind the occupants head.

Passenger Seat

The passenger seat was found with its four seat posts attached to the aircraft floor, and the front frame tube was creased down approximately 10 inches from the forward left seat post.

Passenger Restraint

The passenger restraint was manufactured by Aero Fabricators (model number H-702-300) and installed on the accident airplane on November 11, 2010. The shoulder harness portion of the restraint was manufactured on May 27, 2010, and the lap belt portion was manufactured on August 25, 2010. The shoulder harness label stated the restraint system was a FAA-PMA part with a "rated strength of assembly [of] 1,500 pounds."

The lap belt was attached to the seat at the back seat posts. The lap belt fitting was pinned between the installation bolt and the seat frame, which prevented the lap belt from swiveling forward and aft. The lap belt webbing was pinned between the lap belt fitting and the seat frame, which prevented the seat belt from being able to be adjusted for proper fitting.

The shoulder harness had been removed from the airplane by FAA inspectors. The shoulder harness was intact.

Seat Restraint Installation

The NTSB Survival Factors Group inquired to the mechanic who installed the seat belts and shoulder harnesses into the airplane about the pinned lap belts found in the accident airplane. He explained that he installed bushings into the attachment fittings for the lap belts. The bushings would allow the bolt at the attach point to be fully tightened while also allowing the seat belt to be adjusted and swivel forward and aft. The bushings are not provided by Aero Fabricators in the installation kit for a new restraint system or detailed as required parts in the installation instructions.

During the examination of the airplane, the bushings were not found in the lap belt attachment fittings, thus pinning the hardware and lap belt webbing in one position.

Shoulder Harness Restraint System Testing

Webbing Breaking Strength Testing

On March 18, 2013, an independent research lab conducted a breaking strength test using an exemplar webbing sample provided by Aero Fabricators. In accordance with the Society of Automotive Engineers Aerospace Standard (SAE AS) 8043B, the breaking strength of the webbing was measured approximately 20.9 kilonewtons (kN), which met the breaking strength requirement for upper torso of 17.8 kN, but did not meet the breaking strength requirement for the pelvic of 22.2 kN.

Technical Standard Order (TSO) C22f, dated January 1, 1990, was effective at the time Aero Fabricators applied for the seat belt STC. TSO C22f stated "new models of safety belts that are to be identified with applicable TSO markings and that are manufactured after May 1, 1972, must meet the standards set forth in National Aerospace Standard (NAS) Specification 802 revised May 15, 1950. NAS 802 stated that the rated minimum breaking strength of the complete belt assembly, i.e. 1,500 pounds (lbs). Therefore, the pelvic breaking strength requirement at the time of Aero Fabricators STC application was 2,250 lbs (10kN).

Although the breaking strength of the webbing did not meet the TSO pelvic requirements currently effective as detailed in SAE AS 8043B, the webbing breaking strength met TSO C22f standards in effect at the time of STC approval.

Thread Testing

On March 8, 2013, and April 8, 2013, an independent research lab conducted thread tensile strength and elongation testing using a black and white thread sample provided by Aero Fabricators. In accordance with the test standard, both the black and white threads met the minimum breaking strength and minimum elongation per the specifications.

March 2013 Shoulder Harness Static Testing

On March 20, 2013, an independent research lab conducted a series of 3 static tests, under the supervision of NTSB and FAA personnel. Two exemplar should harness restraint assemblies manufactured by Aero Fabricators, and the aft occupant shoulder harness from the accident airplane were tested.

The shoulder harness restraint was installed on a loading block per the SAE AS 8043B, and load was applied through three attachment points to obtain the load profile described in the standard. The attachment points were one on each side of the lap belt fitting and the third on the shoulder harness fitting. The loading profile included evaluation of the restraint system at 612 lbs (equivalent load at 9g's), 1,500 lbs (rated strength depicted on restraint label), 2,500 lbs (per SAE AS 8043B), and to restraint failure.

The first test conducted used an exemplar shoulder harness restraint system ordered from Aero Fabricators in November 2012. This restraint system reached a maximum load of 1,239 pounds at the point of failure of the restraint. The restraint experienced a stitching failure at the "Y" shoulder harness junction at the maximum load.

The second test conducted used the aft occupant shoulder harness from the accident airplane. This restraint system reached a maximum load of 1,202 pounds at the point of failure of the restraint. The restraint also experienced a stitching failure at the "Y" junction at the maximum load.

The third test conducted used a second exemplar shoulder harness restraint system ordered from Aero Fabricators in March 2013. This restraint system reached a maximum load of 1,281 pounds at the point of failure of the restraint. The restraint also experienced a stitching failure at the "Y" junction at the maximum load.

August 2013 Shoulder Harness Static Testing

On August 29, 2013, an independent research lab conducted another test, under the supervision of NTSB and FAA personnel. This testing was conducted using a mock-up of the accident airplane seat structure obtained from measurements taken during a postaccident examination and from an exemplar Aeronca airplane. The seat was constructed to achieve the proper seat pan angle to closely mimic the seat installed in an Aeronca airplane.

This test was conducted similar to the test conducted during the original STC certification for the Aero Fabricators shoulder harness conducted in March 1992, the loads were calculated using 40 percent of a 9g load of a 170 lb person. A limit load of 408 lbs and an ultimate load of 612 lbs were tested.

The test blocks used by Aero Fabricators during STC certification testing were borrowed for this testing and were used as described in FAA Advisory Circular (AC) 23-4, Static Strength Substantiation of Attachment Points for Occupant Restraint System Installations. The lap and torso blocks were placed on the rigid seat and the shoulder harness restraint assembly was installed. The load was applied through the torso and lap locations, and then evaluated at the specified intervals.

The test conducted used an exemplar shoulder harness restraint system ordered from Aero Fabricators in August 2013. The restraint system reached a maximum torso belt load of approximately 1,105 lbs at the point of failure of the restraint, and a maximum lap belt load of approximately 1,645 lbs at the point of failure. The restraint experienced a stitching failu

NTSB Probable Cause

The pilot’s failure to maintain airspeed following a partial loss of engine power for reasons that could not be determined during postaccident examination, which resulted in an aerodynamic stall and loss of airplane control. Contributing to the severity of the pilot’s head injuries was the failure of the shoulder harness assembly.

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