United States of America

The airplane was destroyed by impact forces and post-impact fire when it impacted the terrain about 1/3 mile northeast of the departure end of runway 20 during takeoff. The airplane was cleared for a right turnout after takeoff, but witnesses observed the airplane climb to about 100 feet, veer left, enter a left bank, go inverted, and then impact the terrain in a nose low attitude. The airplane's left and right wings, fuselage, and cockpit were largely consumed by fire. Inspection of the airplane revealed the flaps and landing gear were retracted. There was aileron control continuity from the control yoke to the aileron bellcranks. There was elevator and rudder control cable continuity from the bellcranks at the forward bulkhead to the control surfaces. Inspections of the engines and propellers indicated the right engine and propeller was producing power in the middle to high power range at impact, and the left engine and propeller was producing power in the low to middle range of power at impact. The 60-year old pilot had flown 942 hours in the accident airplane, and was described as a very safety conscious, conservative pilot, who performed very thorough preflights and adhered to all checklists. The 22-year old pilot rated passenger had not received ground or flight instruction in the make and model of the accident airplane. The toxicology reports were negative for all substances tested. There were no remarkable findings in the autopsies.

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 destroyed by impact forces and fire after it impacted the intersection of runway 23 and 32 while attempting a missed-approach. The pilot's crew day started at 1300 and the 14 hour duty limit was 0300 the following morning. The second leg of the flight was delayed 1 hour and 36 minutes due to a freight delay. The operator reported the pilot exceeded his 14 hour crew day by 45 minutes as a result of the freight delay. The flight was cleared for the runway 23 ILS instrument approach. A witness, who was monitoring the Unicom radio frequency, reported that he heard clicking sounds on the Unicom frequency (to bring up the runway light intensity), but the pilot did not make any radio transmissions. The witness reported the ground fog was very thick. Two witnesses reported they heard the airplane's engines. They then heard the engines go to "full power," and then they heard the airplane impact the ground. They saw an initial flash, but could not see the airplane on fire from 2,500 feet away. FAR 135.213 requires that, "Weather observations made and furnished to pilots to conduct IFR operations at an airport must be made at the airport where those IFR operations are conducted." The destination did not have authorized weather reporting, and the operator's Operating Specifications did not list an alternate weather reporting source. At 0253, the observed weather 20 miles to the north, indicated the following: winds 190 at 4 knots, 1/4 statute mile visibility, fog, indefinite ceilings 100 feet, temperature 22 degrees C, dew point 22 degrees C, altimeter 30.00. From the initial point of impact (POI), the wreckage path continued for about 210 feet on a heading of about 180 degrees. The outboard section of the left wing outboard of the nacelle was found on runway 32, about 85 feet from the POI. Separated, unburned, portions of the left aileron and left flap were also found on the runway. The remaining pieces of the left wing were located with the main wreckage. The right wing was located with the main wreckage and the entire span of the right wing from the wing root to the wingtip exhibited continuity. The inspection of the airplane revealed no preexisting anomalies.

The commercial pilot of the float-equipped airplane was transporting passengers to a lodge at a remote lake. When the airplane did not arrive at the lake, a search was initiated, and two days later the wreckage of the airplane was located on the side of a box canyon about the 2,400 foot elevation level. The canyon is oriented approximately east-west, and the wreckage was distributed along a 100 foot debris field on the north flank of the canyon. Ground scars and wreckage distribution were consistent with the airplane impacting terrain in a steep left bank while executing a turn to reverse direction. No evidence of any preimpact mechanical anomalies was discovered.

A witness reported hearing the distinctive sound of a radial engine just before the crash, and right after that a loud crashing noise. The witness observed a large cloud of dust forming, subsequently saw the plane parts scattering from west to east across the pasture, and then observed the fuselage come to rest. A second witness saw the airplane hit the ground and a cloud of dust form about one-quarter of a mile long and as high as a highline wire. The witness said that after the dust settled he saw scattered plane parts, a highline wire down, and a wing part spilling fuel. The witness also stated that the airplane was traveling from west to east and looked horizontal at impact At 12:59:57, approximately 10 minutes prior to the time of the accident, air traffic control radar identified a target 8 nautical miles northwest of the accident site at an altitude of 5,500 feet mean sea level (MSL). However, this target could not be positively identified as the accident airplane. A postmortem examination of the pilot by a Medical Investigator reported significant natural disease findings included coronary atherosclerosis (hardening and narrowing of the arteries), and chronic thyroiditis (inflammation of the thyroid gland). Both of these diseases can cause sudden cardiac problems including an arrhythmia or heart attack.

An airplane impacted the runway shortly after takeoff. According to the pilot, the airplane rolled sharply to the left immediately after liftoff from the runway. The passenger in the back seat stated the airplane banked sharply to the left after takeoff. The pilot then applied right rudder and aileron to stop the roll. Unable to level the airplane with the horizon, the pilot elected to reduce power to idle on both engines and land on the remaining runway. The airplane impacted the runway, slid into the grass and erupted into flames.

An annual inspection had been completed on the airplane the same day, and on its first flight after the annual inspection, as the airplane was departing from runway 05, at Naples Municipal Airport, witnesses said the engine ceased operating. They also said that the propeller was rotating either slowly or had stopped, and they then observed the airplane enter a steep turn, followed by an abrupt and uncontrolled nose-low descent and subsequent impact with the ground. The airplane came to rest in a nose-low, near vertical position, suspended at its tail section by a fence and some trees along the eastern perimeter of the airport. It had incurred substantial damage and the pilot and two passengers who were onboard the airplane were fatally injured. Postaccident examination of the airframe, flight controls and the engine did not reveal any mechanical failure or malfunction. The flaps were found to have been set to 10 degrees, and the propeller showed little or no evidence of rotation at impact. The FAA Toxicology Laboratory, Oklahoma City, Oklahoma, performed toxicological studies on specimens obtained from the pilot and the results showed that diphenhydramine was found to be present in urine, and 0.139 (ug/ml, ug/g) diphenhydramine was detected in blood. Diphenhydramine, commonly known by the trade name Benadryl, is an over-the-counter antihistamine with sedative side effects, and is commonly used to treat allergy symptoms. Published research (Weiler et. al. Effects of Fexofenadine, Diphenhydramine, and Alcohol on Driving Performance. Annals of Internal Medicine 2000; 132:354-363), has noted the effect of a maximal over the counter dose of diphenhydramine to be worse than the effect of a 0.10% blood alcohol level on certain measures of simulated driving performance. The level of diphenydramine in the blood of the pilot was consistent with recent use of more than a typical maximum single over-the-counter dose of the medication.

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 pilot of N9143B had asked the controller if he could deviate about 12 miles west, because he thought he saw "a hole" in the weather. The radar ground track plot showed the pilot had observed a 3 to 5 mile gap between two thunderstorm clusters and attempted to fly through an area of light radar echoes between the two large areas of heavier echoes. N9143B departed level flight, and radar showed that a cluster of thunderstorms, level three to four were present in the vicinity of N9143B's ground track position. Radar data showed that N9143B started an uncontrolled descent from FL260 (about 27,500 feet msl). Witnesses reported hearing the engine make a winding noise, then observed the airplane come out of the clouds about 300 feet above the ground, in a nose low spiral, and the right wing was missing. The right wing was not found at the crash site, but was located 1.62 miles from the main wreckage. The pilot of N9143B had requested and received a weather briefing. He was advised that the weather data indicated that an area forecast for his route of flight predicted thunderstorm activity and cumulonimbus clouds with tops as high as FL450 (flight level 45,000 feet), and a weather system impacting the Florida Gulf Coast, consisted of "looming thunderstorms" in that area. The pilot had contacted the Enroute Flight Advisory Service (EFAS, commonly known as "Flight Watch") for enroute weather advisories, and advised of "cells" east of St. Augustine, advised of convective SIGMET 05E in effect for southern Florida, and was advised that a routing toward the Tampa/St. Petersburg area and then southward, would avoid an area of thunderstorms.

The crew was completing a local post maintenance test flight at Laredo Airport. After several touch-and-goes, the aircraft was in initial climb when the left engine lost power, followed shortly later by the right engine. The crew reduced his altitude and ditched the aircraft in the Casa Blanca Lake, about 50 feet from the shore. All three crew members were evacuated safely while the aircraft sank in six feet of water.