NTSB Factual Report

HISTORY OF FLIGHT

On December 5, 2004, at 1228 Pacific standard time, a Cessna 185F, N532PC, impacted the Boeing Aircraft Company 737 post-production parking ramp soon after lifting off from a touch-and-go landing at Renton Municipal Airport, Renton, Washington. The private pilot, who was the sole occupant, received fatal injuries, and the aircraft, which was owned and operated by the pilot, was destroyed by the impact sequence and the subsequent fire. The local 14 CFR Part 91 pilot proficiency flight, which began about 40 minutes prior to the crash, was being operated in visual meteorological conditions. There was no report of an ELT activation. No flight plan had been filed.

According to family members and a close acquaintance, it had been at least about six or seven weeks since the pilot had last flown his aircraft, and he had come to the airport on the day of the accident with the intention of practicing his takeoffs and landings to maintain his proficiency and currency. According to the tower controller who was on duty at the time, the pilot called for taxi clearance from the north tower parking area at 1145. At that time the pilot advised the tower that he had information Echo, and that he would be staying in the traffic pattern. He was then cleared to taxi to Runway 15, and after a short period of time at the run-up area adjacent to the approach end of Runway 15, the pilot called for a takeoff clearance. After takeoff, the pilot stayed in the traffic pattern and executed five or six touch-and-go landings. On the last touch-and-go, the aircraft touched down on the runway surface, rolled an undetermined distance, and then lifted back into the air. Up to that point, neither the tower control nor any witnesses had noticed anything out of the ordinary with the aircraft's flight profile or the pilot's transmissions. But, about the time the aircraft reached an altitude of 100 feet above ground level (AGL), the pilot transmitted "I've got a problem here." The pilot did not give a specific indication as to what the problem was, nor did he make any further transmissions. The controller therefore immediately cleared the pilot to land on any runway, and the aircraft was seen banking to the left, in what appeared to most of the witnesses to be a normal pilot-initiated turn, although at a very low altitude. The aircraft's bank angle continued to increase, its pitch attitude initially increased and then decreased, and it susequently descended into the tarmac about 400 feet east of the runway centerline. According to a photo from a Boeing tarmac security camera, when the aircraft was approximately one wing span above the surface, it was in a left bank of more than 80 degrees, its nose was approximately 40 degrees below the horizon, and it had completed about 135 degrees of turn from the runway heading. The camera also revealed that the aircraft's flaps were deployed, although the photo was not clear enough to determined the setting they were at. After the aircraft impacted the tarmac surface between two Boeing 737's, it slid approximately 120 feet before impacting a jet-blast fence, whereupon it burst into flames.

METEOROLOGICAL INFORMATION

According to the 1153 surface aviation weather observation at the Renton Airport, the winds were 190 degrees at six knots, the visibility was 10 statute miles, there was a broken ceiling at 2,800 feet agl, and overcast layer at 3,000 feet agl, a temperature of six degrees Celsius, a dew point of two degrees Celsius, and an altimeter setting of 29.70 inches of Mercury.

WRECKAGE AND IMPACT INFORMATION

At the initial impact point there was an area of white paint transfer onto the concrete surface measuring about one foot wide and approximately 15 feet long. At the southwesterly end of this area, there were numerous very small pieces of pulverized red glass that appeared to be consistent with the material from the left wing navigation light lens. Approximately 17 feet passed the southwesterly end of the initial impact mark, there was another area of white and red paint transfer. This area measured approximately four feet by four feet, and contained small sections where the concrete surface itself had been chipped or gouged. At the northwesterly end of this impact area there were six well defined propeller strike marks/lines. The first four of these marks were 12 inches apart. The next one was separated by 15 inches, and the last was 21 inches from its predecessor. From that point to where the aircraft came to rest, there were a few very light paint transfer lines, and three small pieces of unidentified aluminum. The magnetic heading from the initial point of impact to where the aircraft came to rest was 015 degrees.

At the point where the aircraft impacted the blast fence, its engine had come in direct contact with one of the four-inch diameter steel support posts. The post itself had been displaced/bent about eight inches by the force of the impact. The forward portion of the fuselage, from the front of the engine compartment to a point just aft of the rear side windows, was consumed by fire. The right main gear leg was still attached within its gear strut attach box, but the left main gear leg had been torn loose from the fuselage structure. The left wing leading edge was crushed directly aft along its entire span, and the outboard two-thirds of the span was bent upward about 35 degrees. The most outboard one-third of the span had been ripped and torn away as far aft as the rear spar. The inboard two-thirds of the left wing retained most of its original airfoil shape, and although it suffered minor exterior fire damage, it still contained approximately 15 to 20 gallons of fuel. The right wing, which had come to rest on top of a chain link fence located just aft of an opening in the blast fence, had been totally consumed by fire, except for its associated steel components. Flight control continuity was established to all flight controls from the control yoke/rudders to each flight control bellcrank or attach fitting. Both the upper and lower flap activation cables were traced from their attach point on the manual flap handle to their attachment to the flap actuation pushrods. The manual flap handle support structure had melted in the fire, but the handle itself was found in the handle full-up/ flaps full-down position (flap handle latch positioned in the upper notch of the flap handle ratchet plate). The horizontal stabilizer jack screw was measured at 7.6 inches, which was later determined to be one-third of the distance forward of the travel between takeoff and full nose up.

After the aircraft was moved to the facilities of AvTech Services, LLC., in Maple Valley, Washington, both the airframe and engine underwent further examination. During that examination there were no non-impact induced anomalies found in the aircraft's primary structure or engine, nor were there any apparent anomalies in the aileron, rudder or horizontal stabilizer systems.

Because the flap actuation mechanism had been found in the flaps full-down position, the manual flap handle assembly was also subjected to further examination. That examination revealed that eight out of the nine rivets that pass through the handle at different locations still remained in part or in whole. Some of the rivets remained in there entirety, including the one upon which the handle latch assembly return spring rests, while the shafts of others had melted away, and only their heads and/or bucked ends remained. All eight had suffered extensive heat damage, and all eight had deposited varying amounts of aluminum slag residue near the edge of the holes that they passed through. The ninth rivet, which originally passed through the flap latch pivot inner bushing was not present. In addition, the two washers and the pivot inner bushing itself, which are normally held in place by the ninth rivet, were missing. The outer pivot busing, which pivots around the inner pivot busing, and is an integral part of the latch itself, was still present at its normal location, but it was no longer being retained by the inner busing, and was therefore free to move around within the handle. There was no evidence of aluminum slag around the edge of the hole that the inner bushing passed through. The investigation determined that according to the Cessna design, the outer-most portion of the inner bushing (approximately .040 inch) rests in the sheet metal that makes up each side of the handle structure, and transfers the load of the flaps to the ratchet plate at this location. Further inspection revealed that the two holes in the handle sides that the outer edges of the inner bushing rest in had worn to an oblong shape (see photo #6). According to Cessna, at the time of manufacture the holes were drilled to a diameter of .257 inch, plus or minus .003 inch. The hole on the right side (passenger side) of the handle had worn to the extent that its greatest diameter was .269 inch, and the hole on the left side (pilot side) of the handle had worn to the extent that its point of greatest diameter was .337 inch. The metal that formed the two sides of the handle structure recovered from the subject aircraft was measured to be .040 inch thick (.0396 equals 20 gauge sheet metal).

It was further determined during the investigation that due to the design of the subject flap handle, if the holes in the 20 gauge steel that makes up the handle sides wears to a point that allows the steel latch assembly inner bushing to slip out of a hole in the handle, the load that is normally carried by that bushing as it sits in the handle side would be transferred to the aluminum MS20470AD-5 rivet that is used to retain the inner busing in the handle (see diagram #1). It was also determined that if one or both of these holes wore to the point where the inner bushing slipped out of the handle side, it would be very difficult for the pilot or maintenance personnel to detect this visually, since the AN960-4 washers that are placed under both the head and the bucked end of the rivet would cover any such elongated holes until it was approximately twice its original diameter (see photo #7).

MEDICAL AND PATHOLOGICAL INFORMATION

The Federal Aviation Administration's Bioaeronautical Sciences Research Laboratory performed a forensic toxicology examination of the pilot, and all results were negative for carbon monoxide, cyanide, ethanol, and all specified drugs.

An autopsy was performed by the King County Medical Examiner, and the cause of death was determined to be accidental due to blunt force injuries to the head and neck as the result of the aircraft accident.

ADDITIONAL INFORMAITON

In a check of ten other aircraft (one Cessna 170 and nine Cessna 180/185's) at local airports in Washington, California, and Alaska, the NTSB found that six of those aircraft had issues directly related to the manual flap handle latch pivot point. In four instances there were elongated holes in the handle sides. In two instances both the inner bushing and the retaining rivet had been replaced by an AN hex-head bolt secured with a castellated nut. In one instance the inner bushing and retaining rivet had been replaced with an AN 23/27 type clevis bolt, which was retained with only a cotter pin (no nut).

The aircraft, excluding the flap handle mechanism, was released to AvTech Services, LLC., a representative of the pilot's family, in Maple Valley, Washington, on September 21, 2005.

NTSB Probable Cause

The pilot's failure to maintain aircraft control when the flaps became jammed/stuck in their full-down position during a takeoff from a touch-and-go landing. Factors include a worn/disconnected flap latch mechanism, and the flaps being unable to be retracted.