NTSB Factual Report

HISTORY OF FLIGHT

On November 16, 2004, at 1611 mountain standard time, a Cessna 337B, N133JW, collided with terrain while scouting for elk in the vicinity of Drake, Arizona. The airplane was operated by the commercial pilot under the provisions of 14 CFR Part 91. The pilot and two passengers were fatally injured, and the airplane was destroyed. Visual meteorological conditions prevailed, and a flight plan had not been filed. The personal flight originated at Clark Memorial Airport, Williams, Arizona, at 1459.

A witness reported to the National Transportation Safety Board investigator that he had observed the airplane flying low and slow, in and out of the local canyons and valleys over the previous few days and on the day of the accident. He also stated that he had talked to another witness who said the airplane had flown about 100 feet over his camp on the morning of the 16th. The owner of the airplane said that the pilot routinely used the plane for approved activities, and that the pilot had been taking hunters on elk scouting flights in the local area over the last couple of days.

The Cocino County Sheriff and the Civil Air Patrol located the wreckage on the morning of November 17th. The Yavapai County sheriff took control of the accident location after the wreckage was located. A local individual told the sheriff that they had seen a plume of smoke in the area of the wreckage the previous evening around 1630.

PERSONNEL INFORMATION

A review of Federal Aviation Administration (FAA) records from Oklahoma City, Oklahoma, revealed that the pilot held commercial and flight instructor certificates with airplane single engine land, airplane multiengine land, and airplane instrument ratings. The pilot held a second-class medical dated May 26, 2004, with no limitations.

The pilot's current flight logbook was in the airplane and was destroyed in the ensuing the post accident fire. The pilot's family provided a current resume that summarized his flight hours. He last updated the resume on October 2, 2004. The pilot had 4,100 hours of total pilot-in-command time, 2,200 hours in complex aircraft, 600 hours of multiengine time, 74 hours of actual instrument time, 375 hours of nighttime, and 1,550 hours of cross-country time.

The owner of the airplane allowed the pilot to use the airplane for personal activities. These activities were approved by the airplane owner on a case-by-case basis. The owner of the airplane was aware of the pilot's use of the airplane for game scouting flights.

AIRCRAFT INFORMATION

The airplane was a twin-engine Cessna 337B, serial number: 3370612, which is a centerline thrust airplane with the engines configured ahead and behind the wing, along the centerline of the fuselage. Examination of the maintenance logbooks revealed the airplane had accumulated a total of 4,108.7 hours of operating time as of September 14, 2004. The forward engine's operating time since maintenance overhaul (TSMOH) was 560.9 hours and the aft engine's TSMOH was 238.1 hours, as of September 14, 2004. The most recent annual documented in the logbooks was completed on November 7, 2003.

WRECKAGE AND IMPACT INFORMATION

The Cocino County sheriff located the wreckage on the morning of Wednesday, November 17. The terrain surrounding the wreckage was a flat desert flood plain populated with scrub trees, prickly pear cactus, and dried desert grass. The ground was soft mud and rock. The wreckage coordinates were 35 degrees 01.258 minutes north latitude by 112 degrees 21.662 minutes west longitude, at an elevation of 4,750 feet mean sea level (msl).

The initial point of ground impact was identified at the northern end of the debris field by two green glass lens fragments. The energy path was identified by a lengthy ground scar, which extended from the green lens fragments on a magnetic bearing of 132 degrees. A narrow ground scar extended along this bearing for 36 feet 7.5 inches to an 8-foot-wide circular area of disturbed ground. The main wreckage was another 59 feet away along the 132 bearing line. Plexiglas debris was scattered outward from the circular ground scar on the south side of the debris field. Around the debris field midpoint laid the right main landing gear strut and the forward engine's propeller. The main debris field extended a total length of 124 feet 10 inches.

The center of the airplane wreckage consisted of the remains of the cockpit, both engines, the left wing, the right wing, the right rudder and tail boom, and horizontal stabilizer/elevator. The cockpit was thermally destroyed, and consisted mostly of ash, charred and melted aluminum. The engine control levers were located and the control cables were traced to both engines' throttle, mixture, and propeller governor linkages. The cockpit engine instrumentation gages were in the right side of the instrument panel and exhibited minor thermal damage. Most of the other cockpit instrumentation was destroyed. The left main landing gear strut protruded inverted into the cockpit area along with the wing carry-through spar. Folded under the cockpit area was the extended strut of the nose landing gear. The aileron, rudder, and elevator flight control cables were traced from the cockpit control linkages to their respective control surface attachment points. The elevator trim jackscrew was measured as 1.4 inches in extension. A flap cable end had a broomstrawed appearance. The flap jackscrew was measured as extended 3.2 inches, which according to the manufacturer's technical representative, corresponds to 10 degrees of flaps. Both fuel selector valves were identified and exhibited similar valve selector positions.

The left wing laid inverted on the right side of the wreckage as viewed from the cockpit. The wing exhibited a chordwise crease 4 feet inboard from the wing tip. The wing was thermally damaged at the wing root and the wing surface was discolored black and brown. Mud streaks and scrapes were in the spanwise direction on the outboard 4 feet of the wing. The flap was in its appropriate location on the wing and was bent at mid length. The wing fuel cell was plastically deformed in a ballooned fashion. The left tail boom was destroyed by fire; only the steel flight control cables that run along its length and the lower right rudder hinge were identifiable.

The right wing separated into two sections and laid on the left side of the wreckage as viewed from the cockpit. The outboard section of the wing was under the right tail boom and was extensively thermally damaged. The right wing fuel cell was ballooned, plastically deformed, and the weld seam attaching the two halves split on one side. A 5-foot-long outboard section of wing exhibited substantial 45-degree creases and wrinkles across the skin. The wing tip position light fixture was present but missing the green glass lens. The wing skin along the wing root exhibited tearing at the rivet locations. The inboard 4-foot section of the wing aft of the aft spar was a few feet away and not damaged by fire. The flap was attached to the outboard flap guide hinge.

The right tail boom was bent 90 degrees about 2/3 along its length back into the main wreckage. The horizontal stabilizer and elevator were attached to the tail boom and appeared thermally damaged and positioned above the right wing.

The forward engine was a Continental IO-360-CB, serial number: 236535-R. The propeller was not attached to the crankshaft flange. The induction system and air filter were intact. The exhaust manifold exhibited signs of plastic deformation and crushing. The forward propeller was located separately approximately midway between the main wreckage and the initial point of impact. The propeller exhibited S-type sinusoidal bends in the trailing edges of both blades. The leading edge of both blade tips had numerous 1- and 2-inch divots of missing material. The spinner's metal was twisted in the direction of propeller rotation.

The aft engine was a Continental IO-369-CB, serial number: 236539-R, and was laid inverted in the wreckage. The propeller was attached to the crankshaft flange. The induction system was intact and the air filter had been thermally destroyed leaving only the metal liner. The exhaust manifold was intact and both exhaust pipes were pinched partially closed. The aft propeller was missing about 8 inches of blade tip from one blade, sheared off in the chordwise direction. The other blade was bent aft with dime-sized divots in the leading edge and slight chordwise striations.

The ELT was outside of the main wreckage area. The switch was in the arm position, and the antenna/antenna cable was not present on the coaxial antenna fitting.

MEDICAL AND PATHOLOGICAL INFORMATION

The Yavapai County Medical Examiner completed an autopsy of the pilot. The FAA Bioaeronautical Sciences Research Laboratory performed toxicological analysis from tissue samples obtained during the autopsy. The toxicology results were negative for ethanol and tested drugs.

FIRE

A post impact fire consumed most of the airframe. The accident occurred in a remote location and local rescue agencies were not aware of the event at the time.

TESTS AND RESEARCH

Forward Engine Exam

The forward engine was removed from its mounts and examined in the field. The engine crankshaft was rotated and thumb compression was achieved on cylinders 2, 3, 4, and 6. The rocker arm covers of cylinders 1 and 5 were crushed. Both magnetos produced sparks in firing order. The spark plugs were Champion RMH 38E's; the electrodes were gray in color, and exhibited no signs of mechanical damage. The fuel pump was removed and examined. All rotor vanes were intact and no score marks were identified on the interior of the pump case. The vacuum pump was removed and disassembled. All vanes were intact, similar in size, and the rotor had fractured into wedges. Engine oil was present in the engine and in the oil pan. The fuel distribution valve was disassembled and a petroleum fuel smell was identified. The gascolator was disassembled and the screen examined. The screen contained no debris.

Aft Engine Exam

The aft engine was removed from its engine mount and examined in the field. The propeller and crankshaft was rotated and thumb compression was achieved on cylinders 1, 3, 4, 5, and 6. The number two cylinder had a seized exhaust valve. Both magnetos were thermally damaged and removed from the engine for examination. Both magnetos were seized and could not be rotated by hand. The spark plugs were Champion RHM 38E's. The spark plugs from cylinders 1, 3, and 5 were oil soaked. The ones from cylinders 2, 4, and 6 were gray in color. All spark plugs examined exhibited no mechanical damage. The fuel pump was removed and the drive shaft rotated freely. The vacuum pump was removed and disassembled. All rotor vanes were intact, similar in size, and the rotor was fractured in half. The gascolator was disassembled and the fuel screen examined. The screen contained no debris.

Examination of Video Footage

A sheriff's deputy had been in the vicinity of where the airplane was operating on November 14th and took some video footage of the airplane flying low over the terrain. Examination of the video shows a white and red Cessna 337 flying slightly above the horizon over the desert with its landing gear extended. The duration of the video is 30 seconds.

Aircraft Stall Characteristics

The Cessna Super Skymaster Pilot Operating Handbook includes a stall speed table for a Skymaster at a gross weight of 4,300 pounds on a standard day. According to the stall speed table, an airplane configured with the landing gear down and flaps at 1/3, the stall speed at zero angle of bank is 71 mph (62 kts) calibrated air speed (CAS). At 30 degrees angle of bank the stall speed is 76 mph (66 kts) CAS.

According to the manufacturer, 1/3 flaps corresponds to the flaps being extended 8 degrees and full flaps corresponds to 25 degrees.

GPS Information

During the on scene phase of the Safety Board's accident investigation a Garmin GPS receiver, model 12 XL, serial number 35333605, was located approximately 30 feet from the main airplane wreckage. The GPS receiver was intact with its power off. The GPS receiver was recovered to the Safety Board's Southwest Regional Office where it was turned on and the data in its memory downloaded. The receiver's display screen indicated its software version was 4.00 and the time zone was set to the Alaska time zone (UTC -9). Garmin's MapSource software program, version 6.3, was used to download the receiver's stored waypoints, tracks, and routes.

Two tracks records were present. Track 1 was dated 11/16/04 from 0604 to 0718. Track 2 was dated 11/16/04 from 1359 to 1511. Track 2 corresponded to the day and time of the accident and was examined in detail. Corrected for mountain standard time, the GPS receiver started recording data points at 1459, and soon after recorded points heading in a northerly direction. The track then leads in a southwesterly direction until 1523. At this point the track commences a series of 14-statute mile long north to south (true direction) courses until 1610. The track then enters a left turn and proceeds in an easterly direction. During the eastbound flight the average ground speed decreased from 90 to 80 kts. About 1611, the track reverses course and proceeds westbound. At 1611:28, on the westbound track, the average ground speed decreases from 80 to 67 kts. At 1611:44, the track starts to reverse direction and the average ground speed decreases from 70 to 59 kts. Three seconds later, at 1611:47, the track's average ground speed was 19 kts, and its direction changed from 129 to 293 degrees magnetic. The GPS receiver's next recorded position records a ground speed of zero mph. At 1611:50, its location was N35 degrees 01.252 minutes by W112 degrees, 21.669 minutes. The full GPS track file and graphic depiction of the GPS track is included in the official docket of this report.

ADDITIONAL INFORMATION

Aeronautical Handbook, FAA-H-8083-3, Chapter 5- Slow flight, stalls, & spins

"Accelerated Stalls"

Though the stalls just discussed normally occur at a specific airspeed, the pilot must thoroughly understand that all stalls result solely from attempts to fly at excessively high angles of attack. During flight, the angle of attack of an airplane wing is determined by a number of factors, the most important of which are the airspeed, the gross weight of the airplane, and the load factors imposed by maneuvering.

At the same gross weight, airplane configuration, and power setting, a given airplane will consistently stall at the same indicated airspeed if no acceleration is involved. The airplane will, however, stall at a higher indicated airspeed when excessive maneuvering loads are imposed by steep turns, pull-ups, or other abrupt changes in its flight path. Stalls entered from such flight situations are called "accelerated maneuver stalls," a term, which has no reference to the airspeeds involved."

The Safety Board investigator-in-charge released the wreckage on November 19, 2004.

NTSB Probable Cause

the pilot's failure to maintain airspeed above stall speed while maneuvering at low altitude, which resulted in an accelerated stall and spin. A factor in the accident was the pilot's performance of maneuvering flight at an altitude insufficient to allow for recovery from an accelerated stall.