WPR09LA453

Structural failure of the right wing during the landing approach due to the separation of the wing's fabric covering.

The pilot of the experimental light-sport airplane had just completed a 40-minute-flight, and was turning from the downwind to base leg when at 450 feet above ground level, the airplane rapidly descended and collided with terrain below. The damage to the forward section of the fuselage, the position of the main wreckage, and the minimal damage to surrounding trees indicated a near vertical impact attitude. The location of the right wing, along with the aft downward bending damage observed to its main spars and tensile failure of the forward spar attach point, indicated that the wing separated from the airplane in a down and aft motion during flight. The airplane's flight profile was not conducive to a negative overload failure of the right wing. The outboard right wing ribs failed in tensile overload, and the wing fabric material was observed attached only at the aft spar, and in-trail of the wing. These signatures indicated that the material had become separated from the wing structure in flight. The separation most likely created a high drag, ‘parachute’ effect with resultant failure of the wing. The airplane was built about 18 years prior to the accident, and appeared to have been flown as an unregistered airplane prior to purchase by the two pilots. New wing covering had been installed by the pilots the year prior to the accident, and cursory tensile testing of fabric samples revealed that the material had a breaking strength comparable to similar light aircraft fabric. The pilot-rated passenger was an insulin-dependent diabetic, however, it was not possible to determine whether his condition had any relation to the circumstances of the accident.

HISTORY OF FLIGHT On September 16, 2009, at 1642 Pacific daylight time, an experimental light-sport airplane, Quad City Challenger II, N732LS, collided with terrain in a citrus grove during the landing approach to Redlands Municipal Airport, Redlands, California. The pilot was operating the airplane under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The commercial pilot/co-owner and private pilot co/owner passenger were killed. The airplane sustained substantial damage. The local personal flight departed French Valley Airport, Murrieta/Temecula, California, at 1602, with a planned destination of Redlands Municipal Airport. Visual meteorological conditions prevailed, and no flight plan had been filed. A witness, who was flying in the traffic pattern at Redlands airport, stated hearing a pilot report on the Common Traffic Advisory Frequency (CTAF) that he was approaching the left downwind for runway 26. He described the pilot’s voice as, “shrill” and, “excited.” The witness stated that the call was also unusual because Redlands airport uses a right-hand traffic pattern for that runway. The witness then landed his airplane on runway 26 and began to taxi east on the adjacent taxiway. He then heard a pilot report on the CTAF that he was on left base for runway 26. He then observed a high wing, “ultralight” airplane at an elevation of about 300-500 feet agl at a position that corresponded to left base of runway 26. He observed the airplane descend at a 45-degree angle behind trees and out of his view. An impact damaged Garmin GPSMAP 96C global positioning systems receiver (GPS) was recovered from the accident airplane. The unit was sent to the National Transportation Safety Board Office of Research and Engineering for data extraction. The data revealed the entire flight sequence beginning at French Valley Airport, and continuing on towards the accident site. The airplane departed French Valley and climbed to about 2,300 feet mean sea level (msl) (GPS reported altitude). For the next 38 minutes the airplane continued on a northerly heading at altitudes ranging between 2,300 and 3,000 feet, and ground speeds ranging between 40 and 75 knots. The airplane then entered the left downwind for runway 26 at an altitude of approximately 2,400 feet (800 feet agl). It continued on the downwind leg while maintaining a 1 mile separation from the runway. While on downwind the airplane's ground speed varied between 57 and 69 knots, and its altitude remained constant. The airplane then began a left turn to the base leg, about 1 mile southeast of the arrival end of runway 26. For the next 42 seconds it maintained a groundspeed of about 58 knots, while descending to 2,200 feet. The final recorded GPS position occurred 4 seconds later, at an altitude of 2,151 feet (450 feet agl), and a ground speed of 64.5 knots. The wreckage was located about 300 feet northwest of the final GPS position. PERSONNEL INFORMATION Front Seat Pilot A review of Federal Aviation Administration (FAA) airman records revealed that the 66-year-old pilot held a commercial pilot certificate with ratings for airplane single-engine land, and glider. The pilot held a third-class medical certificate issued in May 2008, with the limitation that he must wear corrective lenses. An examination of the pilot's flight logbook indicated that as of September 3, 2009, he had amassed a total flight time in airplanes of 1,020 hours since his first logbook entry dated 1961. He had accumulated 4.1 hours of flight experience in a Quad City Challenger II, all of which took place in the accident airplane. Review of his glider logbook revealed that between October 1999 and August 2009 he accumulated 168.1 hours of total flight time in gliders, over the course of 494 flights. Aft-Seat Pilot Rated Passenger The 36-year-old pilot held a private pilot certificate with ratings for airplane single-engine land. He received a special issuance third-class medical certificate in November 2003, based on his prior history of diabetes and use of insulin. The certificate was bound by the limitations that it was not valid for any class after August 31, 2004, and not valid outside the borders of the United States. An examination of the pilot's flight logbook indicated that as of September 3, 2009, he had amassed a total flight time in airplanes of 143.5 hours since his first logbook entry dated 1991. He had accumulated 7.5 hours of flight experience in a Quad City Challenger II, all of which took place in the accident airplane. AIRCRAFT INFORMATION The airplane was a two-seat tandem, high-wing, pusher configuration, with a primary structure that consisted of fabric-covered metal tubing. The airplane was of the ‘long-wing’ configuration, with a wingspan of the 31 feet 6 inches. It was configured with dual aileron, elevator, and rudder controls, and a single set of wheel brake controls located on the forward control stick. The airplane was not equipped with a parachute recovery system, and was not equipped with side doors. FAA records indicated that the airplane was manufactured in 1991. In July 2006 it was sold to the pilots, and on January 20, 2008, it was issued an experimental light-sport special airworthiness certificate. At the time of the application, the pilots reported that the airplane was an existing aircraft that did not hold an airworthiness certificate, and had not been operated as an ultralight as defined in 14 CFR 103.1. According to the maintenance logbooks, the airplane received its first and only condition inspection on July 18, 2009. The logbook was new, and the condition inspection was the first and last entry. Prior aircraft flight time was not noted, and no other logbooks were recovered. The Rotax 503, two-stroke engine was mounted above and aft of the cockpit, and equipped with a two-blade composite Warp Drive propeller. The engine data plate was not present on its mounting panel on the crankcase, and could not be located. According to the mechanic who performed the condition inspection, the pilots removed the airplane's original fabric covering, and replaced it with new covering about 2 months prior to the inspection. The mechanic also stated that prior to purchase by the pilots, the airplane was used to perform surveying flights in the Salton Sea area of Southern California. METEOROLOGICAL INFORMATION The closest aviation weather observation station was San Bernardino International Airport, San Bernardino, California, which was 5.5 miles west of the accident site. The elevation of the weather observation station was 1,159 feet msl. An aviation routine weather report (METAR) was recorded at 1651. It reported: winds from 270 degrees at 9; visibility 10 miles; few clouds at 11,000 feet; temperature 34 degrees C; dew point 9 degrees C; altimeter 29.88 inches of mercury. WRECKAGE AND IMPACT INFORMATION The accident site was located within a citrus grove about 1 mile southeast of the arrival end of runway 26. The main airplane structure came to rest at the base of a citrus tree. The trees surrounding the airplane were spaced approximately 20 feet apart, and were undamaged. The outboard 10-foot-long section of the right wing had become separated from the fuselage, and was located about 30 feet east of the main wreckage. The left wing remained partially attached to the fuselage. The horizontal and vertical stabilizers, along with their respective control surfaces were observed comingled in the immediate vicinity of the tail section. An FAA inspector who responded to the accident site reported that the fuel tank had ruptured, but still contained about 2 gallons of fuel. Fluid was observed in the clear fuel lines leading to the engines carburetors. MEDICAL AND PATHOLOGICAL INFORMATION According to the San Bernardino County Sheriff’s Department Medical Examiner, the cause of death for both occupants was reported