Hawkins & Powers Aviation

The airplane was maneuvering to deliver fire retardant when its left wing separated. Aircraft control was lost and the airplane crashed into mountainous terrain. A witness on the ground took a series of photographs that showed the air tanker's left wing separating at the wing root and the remaining airplane entering a 45-degree dive to the ground in a counterclockwise roll. An examination of the airplane wreckage revealed extensive areas of preexisting fatigue in the left wing's forward spar lower spar cap, the adjacent spar web, and the adjacent area of the lower wing skin. The portion of the wing containing the fatigue crack was obscured by the retardant tanks and would not have been detectable by an exterior visual inspection. An examination of two other air tankers of the same make and model revealed the area where the failure occurred on the accident airplane was in a location masked by the airplane's fuselage construction. The airplane was manufactured in 1945 and was in military service until 1956. It was not designed with the intention of operating as a firefighting airplane. In 1958, the airplane was converted to civilian use as an airtanker and served in that capacity until the time of the accident. The investigation revealed that the owner developed service and inspection procedures for the airtanker; however, the information contained in the procedures did not adequately describe where and how to inspect for critical fatigue cracks. The procedures were based on U.S Navy PB4Y-2 airplane structural repair manuals that had not been revised since 1948.

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 flight had departed Tucson, AZ, on a special VFR ferry flight to Greybull, WY. The airplane was not instrumented for IFR flight. When the flight reported over Winslow, it was advised that VFR flight was not recommended northbound from its present position. Surface weather conditions in southcentral wyoming/northwestern Colorado at the time of the accident were consistent with low ceilings, clouds and snow as reported by witnesses and surface weather observations. The witnesses, located near the Dixon Airport, reported hearing a low flying aircraft travelling west to east, and another witness northeast of the arpt heard an aircraft 'revving' its engines. Radar data shows the aircraft tracking northbound slightly east of the Dixon airport, and executing a clockwise 360° turn northeast of the airport and in the vicinity of one of the witnesses. The last radar target received placed the aircraft approximately one mile north-northeast of the accident site. The aircraft impacted snow covered terrain in a steep nose-down attitude. Both pilots were killed.

The Fairchild C-119G airtanker had been dispatched to a fire about six miles west of Castle Crags State Park, California at 17:05 and departed the Siskiyou County Airport, CA (SIY) shortly thereafter. N48076, another airtanker of the same kind, a leadplane, and an air attack arrived at the fire at the same time. Two more airtankers followed shortly thereafter. The leadplane identified the target, the approach and departure routes, indicated the target was at an elevation of 4,500 feet, that the ridge on final approach was to be crossed at 6,600 feet, advised there was no wind, there was good visibility, and that there was no turbulence except a "1.5g bump" going across the head of the fire. The leadplane directed one of the C-119 airtankers to drop first. That airtanker aborted their first run because of excess speed. On the second pass, it crossed the ridge at a different point, permitting a somewhat longer final approach. That drop was a successful one. The run was made through a saddle then down a creek to the fire some two miles down stream with a planned exit down stream into a larger canyon. The leadplane then directed the mishap C-119G airtanker to drop next. The mishap airtanker used the same approach as the first airtanker. The mishap airtanker reached the uphill side of the fire when the crew reported trouble maintaining proper speed and dropped their retardant on the fire. At about the time the pilot dropped the retardant, a structural failure occurred and the right wing separated from the airframe along with the tip of the left wing and the tail booms. The fuselage with both engines and most of the left wing attached encountered terrain impact and burned as a unit.
Source: https://www.fs.usda.gov/managing-land/fire

The pilot was attempting a takeoff on an airstrip where braking action was considered good during the normal summer season. It was about 3,000 feet in elevation and was snow covered most of the year, as on the day of the accident. The strip accommodated takeoffs to the south only due to grading and obstructions. Frequently, this meant a downwind takeoff. On the day of the accident, there was a 5 knots wind from the north with gusts to 10 knots. The pilot said that nose wheel steering was not effective due to the surface and the rudder was not responsive due to the tailwind. Most pilots used a 25° (right turn) dogleg of the runway at the north end to start their takeoff, especially when tailwinds were present. The accident aircraft went off the runway to the left and collided with a snowbank where it nosed over. All four occupants escaped uninjured.

En route from Bettles to Fort Yukon on a fire fighting mission, the airplane was climbing when the right engine caught fire and exploded. The captain ordered the four passengers (firefighters) and the copilot to evacuate the cabin and the captain, sole on board, attempted an emergency landing on a sandbar located near the Kayokuk River. All six occupants were rescued while the aircraft was damaged beyond repair.

During the takeoff roll at Ramona Airport, the airplane went out of control, veered off runway and came to rest. While both pilots escaped uninjured, the airplane was damaged beyond repair.

The aircraft was engaged in a local test flight at Greybull Airport and was carrying one passenger and three crew members. After takeoff, while climbing, the crew encountered technical problems with the right engine. The captain elected to return and initiated a turn when the aircraft lost height and crashed. All three crew members were killed while the passenger was seriously injured.

During 1975, '13D was under contract to the US Department of the Interior and based at Anchorage, Alaska. Total flight time was approximately 1475 hours. On Friday, 8 August 197 5, the aircraft was being flown back to the lower 48 States from Anchorage with an eventual destination of Greybull, Wyoming. One engine had been shut down due to its running rough, and we understand that a planned fuel stop at Ketchikan, Alaska, was missed because of bad weather. Shortly after midnight on Saturday, 9 August, after seven hours of flight, BuNo 59876 ran out of fuel, and the engines that were still in operation began to quit! Luckily, they were over the northern tip of Vancouver Island, British Columbia, Canada, and below was the 5000 foot paved runway at Port Hardy. Unbelievably , during final approach with only one engine still running, the pilot considered he was too high to land and attempted to go-around! The aircraft struck the ground during the turn, crashed through the airport perimeter fence, crossed the rock and driftwood strewn beach, and came to rest in the ocean, approximately 100 yards offshore! When the radio operator in the control tower lost contact with the plane, he immediately sounded the alarm in the airport fire station. Since no aircraft, nor fire, could be seen, it was felt the plane must have gone down short of the airport, and a search was started in that area. When the aircraft finally came to a stop, the two-man crew was unsure of where they were and what had happened. Almost immediately, the cockpit started to fill with water, and the men struggled to climb out a roof escape hatch. After standing on top of the aircraft for a short while, they spotted a seat cushion floating by, grabbed it, and swam the hundred or so yards to shore. When they arrived on land, their legs were so cold they could not stand. After a short rest, the crew scrambled in the dark over logs and through bushes, and made it to the airport boundary fence. During this same time period, the fire and rescue crews decided the plane must have gone off the runway and into the ocean, so they returned to the airport to resume their search. As the pilot and copilot approached the fence, they saw an emergency vehicle speed toward them down the runway and then continue on by until it stopped at the hole in the fence where the plane had crashed through on its way to the ocean. A short time later, another truck arrived. They were able to get the attention of the driver by shouting and waving. The flight crew was taken to the fire hall where they were given blankets and hot drinks until an ambulance took them to the hospital for examination. Both the pilot and copilot received only minor injuries during their ordeal. The pilot was fired by H&P, but the copilot remained with the company, only to be killed in the crash of a C119 during 1980. N6813D received substantial damage to its nose gear and underbelly, and the left wing tip and flap were destroyed.
Source: http://pb4y-2.org/pdf/all.pdf

Following a fire fighting mission in the region of Wenatchee, the crew was returning to Wenatchee-Pangborn Airport. On short final, the airplane crashed in flames short of runway threshold and came to rest. Both pilots were slightly injured and the aircraft was destroyed.