PAGOSA SPRINGS, CO, USA
N91AL
Bell 212
During support of forest fire fighting operations, the helicopter was conducting water drops and was on it's fifth drop of the flight. While proceeding upslope and down wind, at near maximum gross weight for hover out of ground effect, the helicopter began to settle. The pilot attempted to jettison the water load and reverse course. Jettisoning was unsuccessful and the helicopter settled into trees in the fire zone. The pilot sustained minor injuries and the helicopter sustained substantial damage from impact and post impact fire. During transport to storage by another helicopter, using a long line, the accident aircraft was dropped from approximately 700 feet, resulting in total destruction of the aircraft.
On June 18, 1996, at 1548 mountain daylight time, a Bell 212, N91AL, collided with trees while maneuvering during a fire suppression flight 15 miles south of Pagosa Springs, Colorado. The helicopter sustained substantial damage during the accident and was later destroyed during movement to storage. The commercial pilot received minor injuries. Visual meteorological conditions prevailed, and a company flight plan was filed for this public use aircraft flight being conducted under Title 14 CFR Part 133. The helicopter departed a helibase 17 miles south southwest of Stevens Field in Pagosa Springs, at 1511. According to the operator and pilot, the pilot had made four passes over the fire. On the fifth pass, which was up slope and downwind, the aircraft began to settle and the pilot reported he could not get the tank doors open. The helicopter settled into the trees within the drop zone. Density altitude at the time was approximately 12,200 feet. On scene examination of the aircraft was conducted by the Office of Aircraft Services (OAS), and the U. S. Forest Services with assistance from Bell Helicopter Textron under the guidance of the National Transportation Safety Board (NTSB). Testing of equipment was conducted by the NTSB, Denver Field Office. According to information provided by the above on scene entities, the accident site was a wooded area on the side of a hill, on the edge of the fire zone, at an elevation of 8,720 feet above mean sea level (msl). All portions of the wreckage were accounted for within the accident site area and the aircraft was laying on it's left side about 30 degrees left wing down. Slashes were found in portions of downed trees, located near the aircraft, which were consistent with rotor blade slash marks and portions of the main rotor blades were found in the same area. The helicopter exhibited fire damage in the area of the engine inlets, main gear box, and upper aft area of the passenger compartment; however, no fire damage was observed on the surrounding vegetation. The fire was extinguished by a water drop from another helicopter. The helicopter was equipped with an Isolair liquid drop system which remained attached to the under side of the fuselage. The tank and surrounding plumbing were crushed under the wreckage. The fuselage and main cabin exhibited impact damage mainly on the right side of the belly. The cabin interior and cockpit exhibited no impact damage. According to information provided by the on scene persons, the main transmission was displaced downward and both landing skids were separated from the cross tubes which were rotated aft. The lower wire cutter was separated from the fuselage with aft tearing and the tail boom was still attached to the fuselage with no evidence of main rotor blade impact. Both elevators were attached and damaged. Both engines were mounted in the fuselage. There was no evidence of exterior mechanical damage and all lines remained attached and connected. The forward portion of the power section on both engines had fire damage. The upper inlet cowling, fuel lines, electrical lines, and the cowling exhibited scorching. The main transmission was tilted forwarded approximately 20 degrees and the four lugs on the support case were fractured. The lift link was connected to the lift beam and the sump was separated from the transmission but remained in position in the airframe. The main drive shaft was disconnected at the forward end and the female coupling was fractured. The forward male coupling remained attached to the drive shaft; however, the teeth were chipped from angular over-travel of the coupling. The forward end of the drive shaft was scored from rotation and exhibited heat damage. The aft end of the main drive shaft remained connected to the combining gear box and drive continuity through the coupling was established. The main rotor hub and blade assembly remained attached to the mast and exhibited tree strike damage with wood particles compressed into the damaged areas. Both blades had pieces of the after body missing and exhibited span wise fractures. Both pitch horns were separated from the grips from the inserts being pulled out. Both of the scissors-to-stabilizer bar control tubes were fractured. Flight control continuity was established from the cockpit to the swashplate with upper components of the control system showing fire damage. The tail rotor system remained attached to the tail boom and was intact. Tail rotor drive system and tail rotor control continuity was established from the tail rotor forward. The transmission sump coupling on the drive train was pulled out. The Isolair belly tank was mounted to the fuselage and exhibited crushing. The data plate on the tank indicated it was manufactured by the Isolair Corporation in Oregon. The tank was model number 46212-0, serial number 9344. The tank was manufactured on May 5, 1993. The snorkel filling assembly was attached and the dump doors, tank and actuating mechanism sustained vertical crush damage. Water marks under the helicopter were present and according to available information, the tank contained 765 pounds of water at the time of the accident. The electrical control system for the tank including the control box, harness, and cyclic mounted switch assembly were removed by OAS and Forest Service personnel. They were transported to the NTSB, Denver Field Office, for further examination. Following on scene documentation, the wreckage was removed for storage by the owner's representative. Removal was conducted by helicopter using a long line. During transit to storage, the lifting helicopter encountered uncontrollable oscillation of the load and dropped the helicopter from approximately 700 feet agl. The owner's representative stated the fuselage was destroyed by ground impact. The weight of the helicopter at the time of the accident was calculated using data supplied by OAS. EMPTY WEIGHT 7,142 LBS WATER TANK 360 LBS WATER 765 LBS PILOT + BALLAST 170 LBS FUEL 520 LBS MISC EQUIPMENT 40 LBS TOTAL WEIGHT 8,997 LBS According to the attached flight manual performance chart, this helicopter should have been able to hover out of ground effect at its weight of 8,997 pounds under no wind, down draft, or turbulence conditions. The chart is based on pressure altitude corrected for temperature. Weather at the time of the accident was recorded at a remote portable site located 1.32 miles and 288 degrees from the accident site. 6/18/96 1545MDT - Temperature 78 degrees Fahrenheit, wind from 281 degrees magnetic at 10 knots with gusts to 22 knots. The wiring harness, cyclic mounted switches, and control box were tested at the facilities of Century Helicopter, Fort Collins, Colorado. A continuity check was performed on the above items and they were then installed on a Department of Energy Bell 412 helicopter which had the same drop system installed. With the accident controls and harness installed on the Bell 412, the system functioned normally. It was noted during the test that the cyclic mounted switch required high dexterity to manipulate. The normal system on the Bell 412 had the control switches mounted within the cyclic and were easier to operate. In addition, it was learned that the Department of Energy required two pilots on all flights using the Isolair drop system with the second pilot handling the duties of operating the control box. The tank doors and associated equipment could not be tested due to impact damage. Following examination of retained components, they were returned to the owner's representative, Mr. Dennis Jason, of Jason and Associates.
The pilot's failure to comply with performance data for hover out of ground effect. A factor was not attaining load jettison.
Source: NTSB Aviation Accident Database
Aviation Accidents App
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