N732LSQuad City CHALLENGER II · 1991

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.

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.

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.

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.

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.

According to the San Bernardino County Sheriff’s Department Medical Examiner, the cause of death for both occupants was reported as multiple blunt force injuries. The Medical Examiner reported that the aft-seat pilot was equipped with an insulin pump, which appeared to be connected to the pilot subcutaneously with a cannula. The insulin pump did not have recording capabilities.

A relative of the aft-seat pilot stated that the pilot was an insulin-dependent diabetic who was compliant with medical treatment, and diligent in making sure he both ate and had an insulin pump for his medication administration. The relative was unaware of any other medical conditions of the pilot.

Toxicological tests on specimens from both pilots were performed by the FAA Civil Aeromedical Institute. Analysis revealed no findings for carbon monoxide, or cyanide. The results were negative for all screened drug substances and ingested alcohol.

The clinical report for the aft-seat pilot reported the following:

>> 2470 (mg/dl) GLUCOSE detected in Urine

>> 12 (mg/dl) GLUCOSE detected in Vitreous

Refer to the toxicology reports included in the public docket for specific test parameters and results.

Fuselage

The forward cabin sustained crush damaged and had become fragmented from the nosecone through to the engine. The aileron, elevator, and rudder controls for the forward and aft pilot positions were noted still attached at their respective fuselage mount points, and were still connected to their control cables and push-pull tubes. The aileron control and balance cables were continuous to the flaperon mixer, but had sustained multiple broomstraw pattern failures. The flaperon push-pull tubes were affixed to the mixer and their respective flaperon horns, which had become separated from the flaperon roots. The flap mixer mechanism had sustained crush damage; the flap adjustment jack screw was noted at approximately the mid-travel position. The forward/aft rudder interconnect tubes, as well as the rudder control cables at the foot pedals, were still connected at their respective attach points. The cables sustained multiple broomstraw type failures throughout their travel, and were still attached at the rudder horns. The elevator push-pull tube was continuous from the cable bellcrank through to tail-mounted bellcrank. The left and right elevator push-pull tubes were affixed at their respective ends, but had both become severed with granular fracture surface features.

Empennage

No indications of chaffing, binding, or fabric separation were noted in the empennage section. The horizontal stabilizer and its associated strut attach points had separated in multiple areas. The fracture surfaces of these separations exhibited granular surface features. The vertical stabilizer forward and aft spars had become fractured from their fuselage attachment fixtures. Examination of the internal forward spar surfaces revealed white and brown deposits consistent with corrosion. The fracture surfaces did not display any signatures of fretting, and the aft spar displayed a crumple to its aft fracture surface consistent with a forward failure at impact.

Left Wing

The left wing remained partially attached at the forward/aft wing struts and the aft spar. The flaperon was still attached at its hinge points. The majority of the wings fabric covering was intact.

Right Wing

The outboard 10-foot-long wing section consisting of the wing, flaperon, and wing lift struts, had separated from the fuselage. The inboard wing sections remained partially attached at the aft spar, and forward lift strut.

The fabric covering for both the top and bottom wing surfaces had become detached along the entire length of the leading edge, and was observed at the accident site to be draped in-trail of the aft spar. The fabric remained attached to the aft spar, and an approximate 2-inch-wide strip of fabric was still bonded along the front edge of the leading edge for the full length of the outboard wing section. Three of the outboard wing former ribs had failed about 12 inches forward of the trailing edge. The aft sections of the ribs remained attached to the trailing sections of fabric. The fracture surfaces of the ribs were elongated in a ‘necking’ pattern, the origin of which was centered around the fabric attachment rivet holes.

The aft spar and flaperon separated about 50 inches from the root. The fracture surfaces exhibited buckling compression signatures on their lower surfaces, along the airplane's longitudinal axis, consistent with downward bending of the outboard wing section. Additionally, the aft spar exhibited a downward curve from the failure point through to the wing tip.

The forward spar failed at a similar location from the root, with compression signatures facing down and aft. The remaining inboard section of the forward spar had become separated from its fuselage attach fitting. The fitting and its associated wing and frame bolts were still in place; the holes in the spar that connected it to the attachment bracket had become elongated and pulled open, consistent with the spar trailing aft and away from the fuselage. The wing cable brace remained attached at its strut and fuselage mount points, but had separated about 30 inches from the root. The separation exhibited broomstraw pattern features.

The forward and aft lift strut were buckled and separated from the root about 64 and 85 inches, respectively. The fracture surfaces exhibited compression signatures on their upper surfaces along the airplane's longitudinal axis.

No damage was observed to the wing tip or leading edge of the wing outboard of the spar failures.

The inboard aft wing spar and flaperon section sustained a diagonal 1/2-inch-deep scar to their lower surfaces, about 30 inches from the root. The scar contained traces of black material consistent in color and appearance of propeller material. Examination of the propeller tip revealed leading edge nicks and blue paint transfer marks consistent in color to the wing spar.

Photographs of the wing and its associated failure points are contained within the public docket for this accident.

Engine

The engine was examined by the NTSB investigator-in-charge (IIC) and a representative from Rotax Aircraft Engines. The engine did not exhibit any indications of catastrophic internal failure, and examination did not reveal any faults that would have precluded operation. Disassembly of the engine driven pneumatic fuel pump revealed the presence of liquid similar in odor and color to automotive fuel; additionally, the pumps clear pulse diaphragm appeared intact and free of cracks. The Rotax representative stated that the propeller will not ‘windmill’ following a loss of power of this engine type.

A full report of the engine exam is contained within the public docket for this accident.

Weight and Balance

According to the airplane's weight and balance sheet, the basic empty weight was 470 pounds and the maximum gross weight was 1,010 pounds, with a center of gravity range between 80 and 90 inches. According to medical examiner records, the measured weight of the front seat pilot was 232 pounds, and 163 pounds for the aft-seat pilot. Based on these values, and assuming 2 gallons of fuel were in the tank, the calculated center of gravity was about 83 inches.

The Challenger II builders manual states, ‘The typical two-seater with standard covering, wheel pants, brakes, instruments and the 503 engine usually comes out about 320-325 pounds.’

Performance

A performance card located onboard the airplane reported the following aircraft speed limitations:

Vne Never Exceed (Dual): 90 MPH (78 knots)

Va Maneuvering (Dual): 70 MPH (61 knots)

Vs Stall (Dual): 35 MPH (30 knots)

GPS Data

The GPS unit contained partial flight information for various segments of prior flights. The only other complete flight recording occurred on September, 3, 2009. On that date the airplane departed from French Valley Airport, about 0700, arriving at Perris Valley Airport, Perris, California, about 40 minutes later. The data revealed that the airplane approached Perris on a similar flight profile as the accident flight. Corroborating logbook entries for both pilots were noted on this date; additionally, this was the last recorded flight in their logbooks prior to the accident.

Airplane Construction Observations

The tailwheel assembly was noted affixed to the aft fuselage with household ‘drywall’ screws. An automotive paper type fuel filter was observed in-line with the fuel tank pickup. The Rotax 503 installation manual expressly prohibits the use of paper fuel filters. Multiple drilled holes were observed throughout the fuselage and wing load-bearing structures; these holes did not correspond to locations referenced in the airplane plans. Varying degrees of corrosion were noted on multiple parts throughout the airplane. Examples of corroded areas included the vertical stabilizer and its fuselage attach points, main landing gear brake and hub assemblies, and fuselage mounted wing strut support structures. The use of ‘Duct Tape’ was noted as a material for sealing the wing/flaperon gap.

Fabric Covering Material

Sections of the wing fabric material were removed for testing. No manufacture markings were noted on any of the wing material surfaces, and as such, the exact type and origin could not be determined. Samples of the material were taken to Consolidated Aircraft Coatings, under the supervision of the IIC. A representative from Consolidated stated that the material appeared to be of a ‘light weight’ uncertified type. A tensile breaking strength test was performed on six, 1-inch-wide strips of the material utilizing a calibrated load cell. The materials yielded at a force of between 60 and 66 pounds. The test was performed on similar strips of Poly Fiber uncertified light grade material, with results ranging between 60 and 68 pounds.

Further examination of wing material revealed the inclusion of drain grommets that had not been opened to allow for draining. The fabric material was observed affixed to the ribs with rivets, and fabric reinforcement material was noted in these areas. Examination of the reinforcement revealed that it was comprised of a layer of material similar to fiber packaging tape overlaid with painter’s masking tape.

According to FAA Advisory Circular AC 20-27F, Certification and Operation of Amateur-Built Aircraft, "Amateur builders are free to develop their own designs or build from existing designs. We do not approve these designs and it would be impractical to develop design standards for the wide variety of design configurations, created by designers, kit manufacturers, and amateur builders."