The Bell Helicopter Company, JetRanger III helicopter was engaged in water-bombing in support of fire fighting operations in the vicinity of Bendora Dam, about 37 km southwest of Canberra. A Bell 412 helicopter, with a pilot and crewman on board, was conducting water-bombing operations in conjunction with the JetRanger. An Aerospatiale A350 Squirrel helicopter had recently returned to the area of operations and was conducting a survey of the Bendora fire zone.
The pilots of the two water-bombing helicopters had seen each other as they passed on opposite legs of a racetrack pattern between the fire and the dam. As the Bell 412 returned to the dam for water pick-up, the pilot noted the absence of the JetRanger during that pattern. At about 1238 Eastern Standard Time, the Bell 412 pilot unsuccessfully attempted to contact the JetRanger pilot on the radio. A short time later, the pilot of the Bell 412 noticed the upturned fuselage of the JetRanger in the water. He immediately broadcast a PAN call, and contacted the Squirrel pilot to advise that the JetRanger was in the water.
The Bell 412 pilot released his water bucket on the shore of the dam and established a hover close to the upturned helicopter. The crewman entered the water and freed the unconscious pilot from the wreckage. The Squirrel arrived at the dam and landed on the shoreline and two of the occupants entered the water to assist the crewman, who was experiencing difficulty keeping the pilot afloat during the rescue. Once on the shore, the pilot was resuscitated before being transported to a Canberra hospital. There were no known witnesses to the accident.
The JetRanger helicopter was substantially damaged in the accident. Examination of the helicopter indicated impact with the water in a slightly right side down, nose-low attitude. Damage to the main and tail rotor systems indicated that both rotors had been under power when the helicopter impacted the water. Rotational damage to the engine compressor and turbine assemblies confirmed engine operation on impact with the water. Advice from the engine manufacturer indicated that the engine was probably producing above flight idle power at that time. There was no evidence of any pre-impact engine or other aircraft abnormality that would have contributed to the development of the occurrence.
A main rotor blade impacted the pilot's upper doorframe, and the right upper overhead window. There was also impact damage evident on the pilot's helmet, consistent with the helmet being struck either by the door frame structure or a main rotor blade.
An estimated 135 L (107 kg) of fuel was on board the helicopter at the time of the occurrence, which was sufficient for the planned flight. A sample of that fuel was sent to a laboratory in Melbourne, Victoria, for analysis. That analysis confirmed that the fuel was free from contamination and of the correct type. Along with a number of other helicopters, the JetRanger had been refuelling from a mobile tanker. None of the pilots of those helicopters reported any fuel-related problems during the day's operation.
The occurrence bucket attached to the JetRanger was placarded as a `Bambi Bucket' model 1012. The company operations manual did not list the 455 L capacity, 1012 model bucket for use and instead described the 545 L capacity, 1214 model bucket for use by company aircraft when conducting water-bombing operations. The bucket manufacturer left the choice of bucket for use when fire-bombing with the operator. However, the bucket manufacturer did not suggest either of the 1012 or 1214 buckets for use with the JetRanger. Instead, the manufacturer recommended use of the 410 L capacity, 9011 model bucket.
The bucket was attached to the JetRanger's cargo hook by a 24 m steel cable. Electrical wiring was fixed to the cable to allow operation of the water release mechanism by the pilot and, when required, to enable the addition of fire retardant foam. The cargo hook unit included a manual and electrical release, to enable pilot-activated release of the bucket and cable. The helicopter's cargo hook electrical release circuit breaker was found in the open-circuit position. As part of the investigation, the circuit breaker was reset and the cargo hook release was tested electrically and manually. While it could not be determined whether the as-found position of the circuit breaker resulted from pilot selection or the accident, both release mechanisms operated normally during subsequent testing.
An internal `cinching strap' controlled the volume of an `as-manufactured' `Bambi Bucket' via a series of metal `D' rings positioned along the length of the strap. That allowed selection of 70%, 80% or 90% of bucket capacity. Nylon webbing loops stitched to the inside of the collapsible synthetic bucket positioned the strap inside the bucket. The bucket strap fitted to the occurrence bucket was non-standard and did not include any `D' rings. Instead, the strap had been tied off with a knot. That was contrary to the bucket manufacturer's Repair Assessment Manual1 that stated that it was not an acceptable practice to tie knots on the strap. The manufacturer cautioned that such actions may result in a false indication of the actual maximum volume of water in the bucket. Following consultation with the bucket manufacturer, it was determined that the bucket was of a non-standard construction.
Examination of the occurrence bucket revealed that several of the nylon webbing loops had been torn from the inside of the bucket. The investigation was unable to determine when the webbing loops failed. The bucket's capacity was 420 L measured in the as-found condition. During that test it was noted that the `cinching' strap exerted no influence on the bucket's volume due to the torn webbing loops. Post accident testing of the bucket's electric water release mechanism was carried out utilising the helicopter's electrical system. That test revealed that the bucket's mechanism operated normally.
The JetRanger pilot held a current Commercial Pilot (Helicopter) License and a valid medical certificate. He had a total of 6,713 hours total flying experience, with in excess of 2,917 hours on type. He was appropriately endorsed for, and very experienced in, fire fighting and long-line operations. The pilot was reported to be medically fit for the flight.
The pilot sustained traumatic head injuries and was submerged for an undetermined period. During subsequent interviews he was unable to recall any details of the accident.
The all up weight for the helicopter, including the 420 L of water carried in the non-standard 1012 model bucket, was estimated to be about 3,309 lbs. The maximum take off all up weight for the ambient conditions was estimated to be about 3,320 lbs.
The helicopter's centre of gravity was estimated to have been within limits.
The Bureau of Meteorology forecast for the Bendora Dam area indicated an east-northeasterly wind at a speed of 15 kts. Other helicopter pilots operating in the area on the day reported winds that varied in direction and strength. Visibility was reported as `good', with some smoke in the area. The investigation was unable to determine the actual wind direction and speed at the time of the accident.
Federal Aviation Administration Advisory Circular AC90-95 described the conditions under which a loss of tail rotor effectiveness (LTE) can occur. Included among those conditions were: high all up weight; out of ground effect hover; low forward airspeed; high power settings; and a wind direction from the left or rear of the helicopter. LTE can result in a loss of control.
The `Bambi Bucket' Manufacturer's Operator's Manual2 warned pilots not to execute 90 degree pedal turns when the helicopter was close to the water and towing the bucket. That warning highlighted the danger of the bucket suspension lines becoming caught on the rear of a landing gear skid, resulting in a dynamic rollover when lifting the bucket. Federal Aviation Administration Advisory Circular AC 90-87 indicated that dynamic rollover normally occurred during slope landings and take-offs, with some degree of bank angle or side drift, with one skid in contact with the ground. In that case, the in-contact skid acted as a pivot point. If an excessive roll rate was permitted to develop around that pivot point, a critical bank angle could be reached where roll could not be corrected, even with full lateral cyclic. The helicopter would then roll over onto its side.
Other water-bombing pilots reported that, on previous sorties, the JetRanger pilot had been lowering the bucket vertically into the water to fill from an out of ground effect (OGE) hover, and then lifting it clear vertically before transitioning to forward flight. Underwater photographs of the helicopter showed that the bucket cable was not positioned over the rear of the skid assembly. Examination of the helicopter's landing gear skids did not reveal any damage from the bucket cable.
There was no system in place to track the fitment and maintenance of the company's cargo hooks.
Civil Aviation Order (CAO), 20.11, 5.1.1(a), stated that:
`Aircraft shall be equipped with one life jacket for each
occupant when the aircraft is over water at a distance from
(a) in the case of a single engine aircraft - greater that that which would allow the aircraft to reach land with the engine inoperative...'
Para 5.1.7 of the CAO stated, in part:
`Where life jackets are required to be carried in accordance with subparagraph 5.1.1(a) each occupant shall wear a life jacket during flight over water...'
The pilot was reported to have been conducting his water pick-ups from close to the shoreline of the dam. The pilot was not wearing a personal flotation device (PFD) at the time of the accident.
A Flight Safety Foundation report - External Loads, Powerplant Problems And Obstacles Challenge Pilots During Aerial Fire Fighting Operations, based on USA accident reports from 1974 to 1998, stated in part:
`Research has shown that the average person, when immersed in cold water, can hold [their] breath for 17.2 seconds, plus or minus 3.7 seconds. Studies of water accidents involving military helicopters and civilian helicopters, however, show that successful underwater escape requires 40 seconds to 60 seconds'.
Helicopter underwater escape training (HUET) teaches pilots, other aircrew and passengers an instinctive escape procedure providing them with an improved chance of survival in the event of a helicopter ditching into water. The pilot reported that he had not undertaken HUET.
The pilot was qualified and authorised and had recent experience for the operation.
The helicopter had sufficient fuel of the correct type on board for the flight. Rotational damage to the main rotor system and engine was consistent with engine operation at the time of impact.
The helicopter was at high all up weight and operating close to maximum predicted performance in an area with reported variable winds. While those conditions would have increased the risk of encountering LTE, the pilot was highly experienced in long-line and water-bombing operations and had been operating in the area of Bendora Dam for most of the day. That experience should have mitigated the risk that LTE was a factor in this occurrence.
Although of a non-standard construction, the occurrence bucket was assessed as being capable of normal operation, and was able to be carried by the helicopter at its post-accident assessed capacity. There was no evidence that it contributed to the accident.
While the manufacturer of the 'Bambi Bucket' warns of the possibility of dynamic rollover when conducting water-bombing operations, the use of a 24m long-line by the pilot, and vertical water pick-up would have diminished the likelihood for that to have occurred in this occurrence.
The investigation could not confirm the position of the cargo hook release circuit breaker prior to the accident. Had the circuit breaker been in the open-circuit position the rapid release of the bucket by the pilot, such as in an emergency situation requiring jettison of the load, would not have been possible.
The nature of the helicopter's impact with the water, and the resulting damage sustained by the pilot's helmet, reinforced the protective benefits of the use of flightcrew helmets.
It is possible that, during the water pick-up, the pilot may have been at a distance from the shoreline from which, had an engine failure occurred, the helicopter would not have been able to reach land. In that case, the provisions of CAO 20.11 would have applied, requiring the pilot to wear a PFD. That would have greatly eased the difficulty experienced by the helicopter crewman and others performing the rescue and, potentially, lessened the severity of the pilot's injuries.
Given the absence of pilot recollection and witness reports of the accident, and the lack of detailed indications of operation of the helicopter at impact, the reason(s) for the accident could not be established.
While recognising that, in this accident, the pilot was rendered unconscious and therefore unable to exit the helicopter without assistance, the ATSB draws attention to the benefits of HUET. Studies have shown that escape from helicopters involved in water accidents can take longer than the average time that a person can hold their breath. HUET has been shown to decrease exit times from an immersed helicopter, and increase the likelihood of a successful exit by an uninjured occupant. The provision of HUET to pilots, aircrew and passengers regularly operating over significant expanses of water would maximise the possibility for the successful exit of occupants from an immersed helicopter.
Local safety action
The operator has amended the company's operations manual to correctly reflect the types of fire buckets used on the company's individual helicopter types.
The operator has standardised the position of the external load jettison switch on the different helicopter types used by the company in fire fighting operations.
The company's operations manual now details the type of safety clothing to be worn by pilots when engaged in water-bombing operations in company helicopters. The clothing specified includes the wearing of cotton or better, flying suits, approved helmets and comfortable fitting life jackets. Inflatable life jackets have been positioned in each helicopter for that purpose.
The operator has introduced a system for tracking the fitment and maintenance history of cargo hooks fitted to company helicopters.
ATSB safety action
In a briefing to the Civil Aviation Safety Authority, the ATSB drew attention to the fact that the occurrence bucket was not of standard manufacture, and highlighted the possible effects of the use of non-standard buckets by helicopters during fire fighting operations.
As a result of this occurrence, the Australian Transport Safety Bureau issues the following safety recommendations:
The Australian Transport Safety Bureau recommends that the Civil Aviation Safety Authority, in conjunction with the relevant industry associations, highlight the safety benefits to helicopter pilots and crew of the wearing of personal protective equipment, such as helmets and personal flotation devices when carrying out water-bombing in support of fire fighting operations, through safety promotion initiatives.
The Australian Transport Safety Bureau recommends that the Civil Aviation Safety Authority, in conjunction with the relevant industry associations, assess the desirability of a requirement for Helicopter Underwater Escape Training for specialist aerial work operations, such as water-bombing in support of fire fighting operations.
The Australian Transport Safety Bureau recommends that the Civil Aviation Safety Authority, in conjunction with the relevant industry associations, consider advising Australian helicopter operators involved in water-bombing in support of fire fighting operations, of the need to review the type of fire-buckets used to ensure that they comply with the bucket manufacturer's guidance for use on helicopter types and to ensure that the fire-buckets are appropriately maintained.
Related Documents: | Media Alert |
|Date:||13 January 2003||Investigation status:||Completed|
|Time:||1313 hours ESuT|
|State:||Australian Capital Territory||Occurrence type:||Collision with terrain|
|Release date:||16 December 2003||Occurrence class:||Operational|
|Report status:||Final||Occurrence category:||Accident|
|Highest injury level:||Serious|
|Aircraft manufacturer||Bell Helicopter Co|
|Type of operation||Aerial Work|
|Damage to aircraft||Substantial|
|Departure point||Canberra, ACT|
|Departure time||1204 hours ESuT|
|Role||Class of licence||Hours on type||Hours total|