California

The pilot entered the left-hand traffic pattern at an uncontrolled airport on a dark moonless night. Witnesses reported observing the airplane in a left descending turn. As the airplane turned onto the base leg, its left bank angle suddenly became steep. The airplane rapidly descended until colliding with level desert terrain 1.63 nm from runway 30's threshold. There were no ground reference lights in the accident site area. An examination of the airplane structure, control systems, engines, and propellers did not reveal any evidence of preimpact malfunctions or failures. Signatures consistent with engine power were found in both the engines and the propellers. The wreckage examination revealed that the airplane descended into the terrain in a left wing and nose low attitude. Fragmentation evidence, consisting of the left navigation light lens and left propeller spinner, was found near the initial point of impact. The wreckage was found principally distributed along a 307- to 310-degree bearing, over a 617- foot-long path. The bearing between the initial point of impact and the runway threshold was 319 degrees. The pilot's total logged experience in the accident airplane was 52 hours, of which only 1.6 hours were at night. The pilot was familiar with the area, but he had made only two nighttime landings within the preceding 90 days. Review of the recorded ATC communications tapes did not reveal any evidence of pilot impairment during voice communications with the pilot.

The airplane was making a fire retardant drop over a mountain drainage valley when the wings separated from the fuselage. A videotape of the accident sequence showed the airplane as it flew down the valley and proceeded to make a fire retardant drop. When the drop was almost completed, the airplane's nose began moving up, and the airplane started to arrest its descent and level out. The nose of the airplane continued to rise, and the airplane's wings folded upward until they detached from the fuselage at the center wing box beam-to-fuselage attachment location. Close examination of the video revealed that the right wing folded upward first, followed by the left wing about 1 second later. Metallurgical examination of the center wing box lower skin revealed a 12-inch long fatigue crack on the lower surface of the right wing beneath the forward doubler, with two separate fatigue crack initiation sites at stringer attachment rivet holes (which join the external doubler and the internal stringers to the lower skin panel). The cracks from both initiation sites eventually linked up to create a single crack. The portion of the wing skin containing the fatigue crack was covered by a manufacturer-installed doubler, which would have hidden the crack from view and, therefore, prevented detection of the crack from a visual inspection of the exterior of the airplane. The investigation found that the airplane was probably operated within the maximum takeoff gross weight limits specified in the airplane flight manual. The airplane was delivered new to the U.S. Air Force (USAF) in 1957 and was retired from military service in 1978. The U.S. Forest Service (USFS) acquired it from the USAF in 1988 for use as a fire suppression tanker. Between 1978 and 1988, it was kept in a desert storage facility. It was transferred to a civilian contractor for firefighting operations and modified for that role, then sold to a Part 135 operator. The airplane was certificated by the FAA in the restricted category under a type certificate held by the USFS. A Lockheed study concluded that firefighting missions were substantially more severe than typical military logistics operations and aircraft operated in this role would require inspection intervals as much as 12 times more frequently than typical military transport usage for meeting damage tolerance requirements. Concerning the detectability of the cracks, Lockheed reported that nondestructive x-ray inspection methods in current industry and military depot level maintenance processes could have detected, with high confidence, the fatigue cracks when they were 0.50 to 0.75 inch long. Inspection intervals appropriate for this detectable crack size can be determined from a damage tolerance crack growth analysis; however, this requires an extensive knowledge of the operational loads environment and internal stresses of the C-130A wing such as would be found in a military depot level maintenance program. The operating limitations accompanying the restricted certificate specified that it be flown and maintained in accordance with the then-current (1988) USAF technical orders for the C-130A. The USAF depot level maintenance program was not included in the maintenance technical orders and was not individually specified on the certificate's operating limitations. The limitations letter did not specify compliance with USAF maintenance program modifications/amendments in technical orders issued after 1988. The operator devised a maintenance and inspection program based on the specified USAF maintenance technical order but did not develop a depot level inspection requirement to ensure continued long-term airworthiness and damage tolerance that would account for the stresses on the airplane resulting from its new firefighting role and the increasing age of the airplanes. Investigation found that there are five separate FAA-issued type certificates owned by five separate firms for the C-130As used as tankers. Although the five certificates have similar maintenance requirements, none are standardized, there is no depot level maintenance program specified for any of them, and none require full compliance with all military airworthiness technical orders. In 1991, the Department of Interior (DOI) began to doubt the continued airworthiness of the C-130A firefighting tanker fleet and was specifically concerned that the lack of a depot level maintenance program or any requirement for compliance with all military airworthiness technical orders could compromise the safety of the airplane. The DOI asked the FAA to standardize the type certificate for the C-130A and mandate improvements in the maintenance and inspection requirements. In a written opinion, the USAF agreed and urged the FAA to mandate that operators establish a depot level type continuing airworthiness program for the airplane and mandate compliance with all technical orders. In a series of meetings held in 1993, FAA management internally agreed that the DOI and USAF positions held merit and began to develop requirements. In late 1993, in a meeting between the FAA, DOI, USFS, and the airplane operators, the USFS and the operators objected to the idea of depot level maintenance programs and full compliance with all technical orders on the basis of the potential economic impact of these requirements. As of the time of the accident, the FAA had not standardized the existing five type certificates nor had they imposed any additional maintenance or inspection program requirements.

The aircraft was on an IFR clearance and climbing through a cloud layer when it broke up in flight following an in-flight upset. The weather conditions included multiple cloud layers from 4,000 to 13,000 feet, with a freezing level around 7,000 feet msl. An AIRMET was in effect for occasional moderate rime to mixed icing-in-clouds and in-precipitation below 18,000 feet. As the airplane began to intercept a victor airway, climbing at about 2,000 feet per minute (fpm), and passing through 6,700 feet, the airplane began a series of heading and altitude changes that were not consistent with its ATC clearances. The airplane turned right and climbed to 8,600 feet, then turned left and descended to 8,000 feet. The airplane then turned right and climbed to 8,500 feet, where it began a rapidly descending right turn. At 1034:33, as the aircraft was descending through 7,000 feet, the pilot advised ATC "four Juliet victor I just lost my needle give me..." No further transmissions were received from the accident airplane and the last radar return showed it descending through 3,200 feet at about 11,000 fpm. Analysis of radar data shows the airplane was close to Vmo at the last Mode C return. Ground witnesses saw the airplane come out of the clouds in a high speed spiral descent just before it broke up about 1,000 feet agl. Examination of the wreckage showed that all structural failures were the result of overload. The aircraft was equipped with full flight instruments on both the left and right sides of the cockpit; however, the flight director system attitude director indicator and horizontal situation indicator were only on the left side. The aircraft was also equipped for flight into known icing conditions, with in part, heated pitot tubes (left and right sides), static sources, and stall warning vanes. During the on-scene cockpit examination, except for the pitot heat switches, the cockpit controls and switches were found to be configured in positions consistent with the aircraft's phase of flight prior to the in-flight upset. The right pitot heat switch was found in the ON position, while the left switch was in the OFF position. The left pitot heat switch toggle lever was noticeably displaced to the left by impact with an object in the cockpit. With the exception of the left pitot heat, the anti-ice and deice system switches were all configured for flight in icing conditions. The pitot heat switches, noted to be of the circuit breaker type (functions as both a toggle switch and circuit breaker), were removed from the panel and sent to a laboratory for examination and testing. Low power stereoscopic examination of the switches found that the right switch was intact, while the toggle lever mechanism of the left switch was broken loose from the housing. Microscopic examination of the left switches housing fracture surface revealed imbedded debris and wear marks indicative of an old fracture predating the accident. The broken left switch could be electrically switched by physically holding the toggle lever mechanism in the appropriate ON or OFF position. The electrical contact resistance measurements of the left switch varied between 0.3 and 1.4 ohms, and was noted to be intermittently open with the switch in the ON position. Both switches were then disassembled. While particulate debris was found in both switches, the left one had a significant amount of large coarse fibrous lint-like debris. The flexible copper conductor of the left switches circuit breaker section had several broken strands, and the electrical contacts were dirty. The laboratory report concluded that the left switches toggle was bent to the left in the impact sequence; however, the housing fracture predated the accident and allowed an internal build-up of large coarse fibrous lint-like debris. The combined effects of the broken housing, the resulting misalignment of the toggle mechanism, the dirty contacts, and the large coarse lint debris prevented reliable electrical switching of the device and presented the opportunity for intermittently open electrical contacts. Continuity of the plumbing from the pitot tubes and static ports to their respective instruments was verified. Electrical continuity was established from the bus power sources through the circuit breakers and switches to the heating elements of the pitot tubes and static sources. The heating elements were connected to a 12-volt battery and the operation of the heating elements verified.

The crew departed Twentynine Palms on a local training flight. Shortly after takeoff, the engine n°1 failed. The aircraft encountered difficulties to gain height when the engine n°4 lost power. The crew attempted an emergency landing in a sandy area located about 4,5 km past the runway end. All eight crew members escaped uninjured while the aircraft was damaged beyond repair.

The airplane collided with mountainous terrain during cruise after encountering turbulence and downdrafts associated with mountain wave conditions. According to Federal Aviation Administration (FAA) records, the pilot called the Reno Automated Flight Service Station at 0941 and filed an IFR flight plan, then asked for the winds aloft forecast, which was provided. The pilot did not request any additional weather briefing information for the flight. No other record was found that the pilot obtained additional weather forecast information from any official source associated with the FAA or the National Weather Service. At the time of the pilot's call to the Reno AFSS, several AIRMET weather advisories had been issued hours prior detailing warnings for turbulence and clear icing along the route of flight. The advisories warned of occasional moderate turbulence below 18,000 feet in moderately strong westerly winds especially in the vicinity of mountainous terrain. Clear Air Turbulence (CAT) between 18,000 and 40,000 feet was forecast over the area of the accident site due to jet stream wind shear and mountain wave activity. The pilot departed under visual flight rules (VFR) and picked up his instrument flight rules (IFR) clearance en route and climbed to 14,000 feet. The pilot later asked if he could maintain 12,500 feet. The controller advised him that the minimum IFR altitude on this segment of his route was 14,000 feet, and the pilot cancelled his IFR flight plan. The controller advised the pilot that he had lost radar contact, and instructed the pilot to squawk VFR and the pilot acknowledged the transmission. The last radar target was about 1/2 mile east of Eagle Peak (elevation 9,920 feet) in the Warner Mountains. Rescuers discovered the wreckage near the crest of Eagle Peak on November 23. Investigators found no anomalies with the airframe, engines, or propellers that would have precluded normal operation. The NWS had a full series of AIRMETs current over the proposed route of flight, which included mountain obscuration, turbulence, and icing. Analysis of the weather conditions disclosed a layer between 9,500 and 11,000 feet over the accident site area as having a high likelihood of severe or greater turbulence. A pilot on the same route of flight reported at 1127 that he was in instrument conditions at 11,000 feet, and experiencing light turbulence and light clear icing conditions. He also reported encountering updrafts of 2,000 feet per minute, which was indicative of mountain wave activity. A company pilot was in a second Aero Commander trailing the accident airplane and he reported that at 1147, at a position near the accident site, he encountered a severe downdraft. He applied full climb power, but as the airplane passed over the accident site position, the airplane continued to lose altitude even at maximum power. At 1159, he was able to gain altitude, and return to his assigned cruising altitude of 14,000 feet. The second Aero Commander was turbocharged, the accident airplane was not. Analysis showed that the topography of the area was critical in this case, given that the accident site was at an elevation of 9,240 feet on the eastern slope of Eagle Peak. The accident airplane's flight track was normal along the airway until immediately downwind of the higher terrain. As the flight approached the lee side of the mountain, it came under the influence of the mountain wave and first encountered an updraft and then a downdraft, which increased in amplitude as the flight progressed towards Eagle Peak. Eagle Peak was the tallest point along the Warner Mountain range and the steep slope of this terrain was significant when the mountain wave action was encountered. Such terrain features have been known to enhance the vertical downdrafts and updrafts associated with the most intense mountain wave turbulence.

During an aborted nighttime takeoff, the airplane continued off the end of the 4,987-foot-long runway, vaulted an embankment, and impacted a guardrail on an airport service road 30 feet below. According to the manufacturer's pilot operating handbook, the takeoff distance required for the ambient conditions was 1,620 feet and the accelerate-stop distance was 2,945 feet. Several witnesses reported observing the airplane traveling along the runway at an unusually high speed, with normal engine sound, and without becoming airborne; followed by an abrupt reduction in engine power and the sound of screeching tires. Skid marks were present on the last 1,000 feet of the runway. In the wreckage, the gust lock/control lock was found engaged in the pilot's control column.

The airplane collided with an airport boundary fence during an aborted landing. The pilot made a normal approach following the visual approach slope indicator (VASI) with gear down and full flaps and touched down just past the numbers and began to decelerate. The pilot selected reverse thrust with both engines. As he added power to decelerate, the airplane suddenly veered to the left and off the runway when the right engine did not go into reverse thrust. He deselected reverse thrust and aligned the airplane with the runway. He was approaching the end of the runway at high speed and elected to attempt a takeoff. The airplane went off the end of the runway onto smooth grass. The pilot rotated the airplane, but the airplane collided with an airport boundary fence and came to rest in a field. In a post accident examination, when the power levers were placed in the full reverse position, the left fuel control measured 4°, while the right measured 0°. The left pitch control measured 10°, while the right measured 0°; the controls should have read 0°. A controls engineer determined that during landing, there would be a 10° propeller pitch control (PPC) angle mismatch, which would be about 2.5° of BETA angle. With matched levers, there would be asymmetric reverse thrust with the left engine lower in torque. This would result in the airplane turning towards the left if both propellers had gone into reverse pitch.

During an aerial fire suppression mission for the California Department of Forestry (CDF), two Grumman TS-2A airplanes, operating as Tanker 92 (N442DF) and Tanker 87 (N450DF), collided in flight while in a holding pattern awaiting a retardant drop assignment on the fire. All of the airplanes fighting the fire were TS-2A's, painted in identical paint schemes. The Air Tactical Group Supervisor (AirTac) was orbiting clockwise 1,000 feet above the tankers, who were in a counterclockwise orbit at 3,000 feet mean sea level (msl). The pilots of both aircraft involved in the collision had previously made several drops on the fire. Records from the Air Tac show that Tankers 86, 91, and 92 were in orbit, and investigation found that Tanker 87 was inbound to enter the orbit after reloading at a nearby airport base. AirTac would write down the tanker numbers as they made their 3-minutes-out call, and usually ordered their drops in the same order as their check-in. The AirTac's log recorded the sequence 86, 91, 21, and 92. The log did not contain an entry for Tanker 87. Other pilots on frequency did not recall hearing Tanker 87 check in. Based on clock codes with 12-o'clock being north, the tankers were in the following approximate positions of the orbit when the collision occurred. Tanker 92 was at the 2-o'clock position; Tanker 86 was turning in at the 5-o'clock position; and Tanker 91 was in the 7-o'clock position. The AirTac's log indicated that Tanker 92 was going to move up in sequence and follow Tanker 86 in order to drop immediately after him. Post accident examination determined that Tanker 92's flaps were down, indicating that the pilot had configured the airplane for a drop. Tanker 92 swung out of the orbit wide (in an area where ground witnesses had not seen tankers all day) to move behind Tanker 86, and the pilot would likely have been focusing on Tanker 86 out of his left side window. Tanker 87 was on line direct to the center of the fire on a path that witnesses had not observed tankers use that day. Reconstruction of the positions of the airplanes disclosed that Tankers 86 and 91 would have been directly in front of Tanker 87, and Tanker 92 would have been wide to his left. Ground witnesses said that Tanker 87 had cleared a ridgeline just prior to the collision, and this ridgeline could have masked both collision aircraft from the visual perspective of the respective pilots. The right propeller, engine, and cockpit of Tanker 92 contacted and separated the empennage of Tanker 87. The propeller chop was about 47 degrees counterclockwise to the longitudinal axis of Tanker 87 as viewed from the top. The collision appeared to have occurred about 2,500 feet, which was below orbit altitude. CDF had no standard operating manual, no established reporting or entry point for the holding orbits, and a tanker could enter any point of the orbit from any direction. While no standardized procedures were encoded in an operating manual, a CDF training syllabus noted that a tanker was not to enter an orbit until establishing positive radio contact with the AirTac. The entering tanker would approach 1,000 feet below AirTac's altitude and stay in a left orbit that was similar to a salad bowl, high and wide enough to see and clear all other tankers until locating the tanker that it was to follow, then adjust speed and altitude to fall in behind the preceding airplane.

During an aerial fire suppression mission for the California Department of Forestry (CDF), two Grumman TS-2A airplanes, operating as Tanker 92 (N442DF) and Tanker 87 (N450DF), collided in flight while in a holding pattern awaiting a retardant drop assignment on the fire. All of the airplanes fighting the fire were TS-2A's, painted in identical paint schemes. The Air Tactical Group Supervisor (AirTac) was orbiting clockwise 1,000 feet above the tankers, who were in a counterclockwise orbit at 3,000 feet mean sea level (msl). The pilots of both aircraft involved in the collision had previously made several drops on the fire. Records from the Air Tac show that Tankers 86, 91, and 92 were in orbit, and investigation found that Tanker 87 was inbound to enter the orbit after reloading at a nearby airport base. AirTac would write down the tanker numbers as they made their 3-minutes-out call, and usually ordered their drops in the same order as their check-in. The AirTac's log recorded the sequence 86, 91, 21, and 92. The log did not contain an entry for Tanker 87. Other pilots on frequency did not recall hearing Tanker 87 check in. Based on clock codes with 12-o'clock being north, the tankers were in the following approximate positions of the orbit when the collision occurred. Tanker 92 was at the 2-o'clock position; Tanker 86 was turning in at the 5-o'clock position; and Tanker 91 was in the 7-o'clock position. The AirTac's log indicated that Tanker 92 was going to move up in sequence and follow Tanker 86 in order to drop immediately after him. Post accident examination determined that Tanker 92's flaps were down, indicating that the pilot had configured the airplane for a drop. Tanker 92 swung out of the orbit wide (in an area where ground witnesses had not seen tankers all day) to move behind Tanker 86, and the pilot would likely have been focusing on Tanker 86 out of his left side window. Tanker 87 was on line direct to the center of the fire on a path that witnesses had not observed tankers use that day. Reconstruction of the positions of the airplanes disclosed that Tankers 86 and 91 would have been directly in front of Tanker 87, and Tanker 92 would have been wide to his left. Ground witnesses said that Tanker 87 had cleared a ridgeline just prior to the collision, and this ridgeline could have masked both collision aircraft from the visual perspective of the respective pilots. The right propeller, engine, and cockpit of Tanker 92 contacted and separated the empennage of Tanker 87. The propeller chop was about 47 degrees counterclockwise to the longitudinal axis of Tanker 87 as viewed from the top. The collision appeared to have occurred about 2,500 feet, which was below orbit altitude. CDF had no standard operating manual, no established reporting or entry point for the holding orbits, and a tanker could enter any point of the orbit from any direction. While no standardized procedures were encoded in an operating manual, a CDF training syllabus noted that a tanker was not to enter an orbit until establishing positive radio contact with the AirTac. The entering tanker would approach 1,000 feet below AirTac's altitude and stay in a left orbit that was similar to a salad bowl, high and wide enough to see and clear all other tankers until locating the tanker that it was to follow, then adjust speed and altitude to fall in behind the preceding airplane.

During a forced landing the left wing struck a light standard pole, and the airplane came to rest inverted after colliding with a fence. The purpose of the flight was to conduct recurrent training to include emergency procedures. On the accident flight the certified flight instructor (CFI) initiated a simulated engine failure after takeoff during the initial climb out. The student advised the tower, and turned crosswind at 700 feet agl. The student set up for landing, which included lowering the landing gear and adding 10 degrees of flaps. On short final, descending through 400 feet agl, both the CFI and student realized they would not make the runway. Both pilot's advanced the throttle, to arrest the descent and perform a go-around. There was no corresponding response from the engine. During the final stages of the emergency descent, the pilot maneuvered the airplane to avoid a work crew at the airport boundary fence and the airplane collided with the light standard pole and a fence. An airframe and engine examination discovered no discrepancies with any system. Following documentation of the engine and related systems it was removed and installed in an instrumented engine test cell for a functional test. The engine started without hesitation and was operated for 44 minutes at various factory new engine acceptance test points. During acceleration response tests, technicians rapidly advanced the throttle to the full open position, and the engine accelerated with no hesitation. A second acceleration response test produced the same results. According to Textron Lycoming, there were no discrepancies that would have precluded the engine from being capable of producing power.