Bell 206B(II), VH-TMR

History of flight

Following an earlier flight from the mainland and a brief shutdown on a floating pontoon at Norman Reef, the Bell Jetranger II 206B departed in a south-south-east direction into the prevailing wind. On board with the pilot were four passengers scheduled for a scenic flight around Norman Reef and return to the pontoon. Immediately following the takeoff, the pilot initiated a right banking turn. While in the turn, with a quartering tailwind, the helicopter began an uncommanded yaw to the right. The pilot reported that he lowered the collective and pushed the tail rotor pedals left and right in an attempt to regain control of the helicopter. Following those actions, and after two complete 360-degree rotations to the right, the yaw abated. After a momentary pause, the helicopter again began to yaw to the right. The pilot broadcast a MAYDAY on CTAF frequency, armed and inflated the emergency flotation gear, and initiated a water landing. The helicopter impacted the water and rolled to the right. The pilot and three occupants successfully exited the helicopter unassisted. One passenger occupying the right rear passenger seat was momentarily trapped in the helicopter by her seatbelt, as the seatbelt release latch had become reversed. The pilot and onlookers from a nearby pontoon eventually assisted her from the helicopter. The helicopter sustained substantial damage.

Weather

The forecast for the area was for isolated showers along the seacoast with winds from the south-east at 15 knots, with broken Stratus 1000 to 2000 feet in showers. Observations of the weather at the nearby pontoon recorded at 0700 hours Eastern Standard Time indicated wind from the south-southeast at 15 knots with no cloud and a temperature of approximately 22 degrees Celsius.

Wreckage examination

All flotation bags of the emergency flotation gear activated upon selection. The helicopter had impacted the water with approximately 10 degrees nose-down attitude, little forward airspeed, and a slight right-bank. The advancing main rotor blade contacted the water causing separation of the main rotor hub and displacement of the main transmission. The retreating blade impacted and severed the tail boom, tail rotor controls, and the tail rotor driveshaft. The transmission-to-engine driveshaft, transmission upper deck, and forward engine firewall were also damaged following transmission displacement. The damage was indicative of at least partial drive train continuity at the time of impact. No pre-existing mechanical defect was discovered that would have resulted in loss of tail rotor control. It was determined that the helicopter was capable of normal operation prior to the accident.

Helicopter information

The Bell 206B II Jetranger helicopter was manufactured in 1973 and was first entered on the Australian Civil Register on 17 April 1973. The part number 206-016-201-133 tail rotor blades had been installed in March 1999. Those blades were longer length than the standard blades, with improved performance, and therefore believed to be less susceptible to loss of tail rotor effectiveness (LTE). The helicopter was last reweighed on 4 October 1996. The empty weight of the helicopter, according to the last weight and balance calculations of 20 May 2000, was 897.6 kilograms. The maximum allowable gross weight of the helicopter was 1,451 kilograms. The estimated takeoff weight using the May 2000 calculations was 1,357 kilograms. The helicopter's flight manual was not recovered to permit confirmation of the flight manual weight and balance documentation.

Personnel information

The pilot had a total of 1,281.3 hours on rotary wing aircraft, including 751.8 hours on type. He had recorded 114.4 hours on this particular helicopter. The pilot held a valid Commercial Pilot's License (Helicopter), Bell 206 type endorsement, and Class One medical certificate. The endorsement was issued on 15 November 1997. The pilot's last flight review was completed on 20 August 1999. He had completed a 0.3 hour basic introduction check ride with the company chief pilot on 11 April 2000. Thereafter, he accompanied other company pilots operating in the local area, until he was permitted to fly as pilot in command.

The pilot had been on duty for six hours leading up to the accident and had 15 hours off duty before the work period, including 8.5 hours sleep the night prior to the accident. He had flown this particular helicopter 5.2 hours the day before the accident, with a total duty time that day of 8.5 hours. He had a rostered day off two days prior to the day of accident.

Loss of Tail Rotor Effectiveness

The phenomena of LTE, also known as unanticipated right yaw, has been identified as a contributing factor in several helicopter accidents. According to United States Army testing, OH-58 series helicopters (the Bell 206 series is the civilian variant) have proven in the past to be susceptible to LTE under certain low speed manoeuvres. LTE is not related to a maintenance malfunction and is associated with single main rotor, tail rotor configured helicopters. LTE is a result of the tail rotor losing aerodynamic efficiency due to a combination of several factors. Those factors include main rotor vortex interference and tail rotor vortex ring state (related to airflow disruption over the tail rotor), helicopter weathercock stability, and the loss of translational lift. The regimes in which LTE may be encountered include low airspeed (less than 30 knots) when translational lift is lost or reduced, high power, and in the case of the United States designed helicopters, operating in a left crosswind or tailwind or with a high yaw rate to the right.

There is greater susceptibility for LTE on United States designed helicopters in right turns and more so in right turns overwater. This is especially true during flight at low airspeeds when the pilot is looking out the right window (not viewing the instrument panel) and is unaware of the airspeed dropping to a low value. The turn is commonly done with reference to the ground where the pilot attempts to keep a constant groundspeed by referencing ground cues. Flying overwater, the pilot does not have the visual cues available as when flying overland.

In turbine powered helicopters, the frame of reference for the engine power governor is the main rotor RPM (Nr) with reference to the airframe. Once the helicopter begins spinning rapidly to the right as during the onset of LTE, the governor will sense a false increase in Nr and reduce fuel flow to the engine in order to maintain what it believes to be a constant Nr with reference to the airframe. Any reduction in Nr will result in a corresponding reduction in tail rotor RPM, with an associated reduction in the effectiveness of the tail rotor.

Recommended LTE recovery techniques

Correct and timely response to the uncommanded right yaw associated with LTE by immediately applying full left pedal and decreasing power and main rotor blade pitch requirements, will usually counter the condition. However, if the pilot's response is incorrect or slow, the yaw rate may rapidly increase to a point where recovery is not possible. The pilot expressed no knowledge of recommended recovery techniques to counteract the onset of LTE.

In response to several reports of unanticipated right yaw incidents, the Federal Aviation Administration circular AC 90-95 recommends the following recovery techniques:

a. If a sudden unanticipated right yaw occurs, the pilot should perform the following:
(1) Apply full left pedal. Simultaneously, move cyclic forward to increase speed. If altitude permits, reduce power.
(2) As recovery is effected, adjust controls for normal forward flight.
b. Collective pitch reduction will aid in arresting the yaw rate but may cause an increase in the rate of descent. Any large, rapid increase in collective to prevent ground or obstacle contact may further increase the yaw rate and decrease rotor rpm.
c. The amount of collective reduction should be based on the height above obstructions or surface, gross weight of the aircraft, and the existing atmospheric conditions.
d. If the rotation cannot be stopped and ground contact is imminent, an autorotation may be the best course of action. The pilot should maintain full left pedal until rotation stops, then adjust to maintain heading.

Furthermore, Bell Operational Safety Notice (OSN) 206-83-10 states that "An unanticipated right yaw may occur under certain conditions not related to a mechanical malfunction. These conditions may include high power demand situations while hovering, and/or when relative wind affects airspeed versus ground speed." The OSN recommends recovery techniques as follows:

1. Apply full left pedal.

2. Apply forward cyclic.

3. If altitude permits, reduce power.

Organisational Factors

The company did not have systems in place to address the organisational aspects that were identified as factors contributing to the accident. These were:

1. The company had no formal pilot induction program. Newly inducted pilots were not required to perform flight checks in areas reflective of actual operating conditions.
2. The Chief Pilot did not document and maintain individual files on each line pilot. Line pilots were not required to perform flight checks in areas reflective of actual operating conditions.
3. Flight checks were not regularly scheduled and were of short duration.
4. The company had no Flight Safety Program in place.
5. The company had no formal system of maintenance control and no assigned maintenance controller. Non-compliance with maintenance requirements and unapproved maintenance was reported on company helicopters.

These were not required by regulation.

CASA surveillance

This operator was also involved in a fatal accident in March 1999. CASA Flying Operations Surveillance Guidelines-Variations to Normal Surveillance includes significant safety related incidents as typical triggers justifying long-term increases in scheduled surveillance. No special audit of the organisation was completed following the fatal accident. A Flight Operations Inspection completed on 29 January 1999 identified several discrepancies. The inspector's report included a note recommending increased surveillance of the organisation. CASA regional management also requested authorisation from the CASA central office for increased surveillance of the organisation, however, the surveillance level of the organisation remained the same.

An Airworthiness Inspection (ramp check) was completed on 12 April 2000. During that inspection, three discrepancies were noted against the helicopter. Included among these was one noting "flight manuals contain expired weight control documents". Prior to the accident, there was no documentation on the CASA files to indicate acquittal of the discrepancy.

Following this accident, a CASA team completed a special audit of the organisation during 11-17 August 2000. The special audit resulted in the CASA team issuing a safety alert to ensure all required maintenance was completed on company helicopters and six requests for corrective action to resolve safety concerns. The company corrected these discrepancies and continued charter operations following the audit.

CASA surveillance documentation

CASA utilised the ASR (Aircraft Survey Report) Aviation Safety Surveillance Program (ASSP) 604 form to outline discrepancies noted during airworthiness inspections of aircraft and helicopters. According to the CASA ASSP manual, inspectors and team leaders were responsible for the monitoring of acquittals of ASRs. The forms did not require the Certificate of Registration holder to carry out rectification action within any particular timeframe.

CASA utilised a form called the Safety Trend Indicator to analyse significant factors related to the operator's risk level. That form included a question concerning the non-acquittal of Non-compliance Notice (NCN) ASSP 603 forms within the last 12 months. No response was required concerning non-acquittal of ASR ASSP 604 forms.

When the pilot began the right banked turn, he exposed the helicopter to firstly, a left crosswind, then a quartering tail wind. Flying at low airspeeds and operating out of ground effect, the helicopter was satisfying several of the operational conditions necessary to experience an uncommanded right yaw or LTE as outlined in Bell OSN 206-83-10.

The pilot indicated no awareness of operational conditions necessary to experience LTE, or knowledge of recovery techniques to counteract the onset of LTE. The failure of the helicopter to recover from the LTE condition following the pilot's reported corrective actions, was probably a result of his lateness to recognise the onset of LTE in sufficient time to permit recovery.

Organisational Factors

CASA's audit of August 2000 found that the checking of line pilots by the Chief Pilot was irregular and ineffective. Pilot flight checks were conducted in areas unreflective of actual operating conditions. In addition, those flight checks were of insufficient duration to appropriately assess the pilot's skills. Safety awareness training of personnel was considered inadequate. The operator had not established a sufficient maintenance control program. This resulted in the operation of company helicopters with overdue maintenance requirements. The lack of a formal pilot induction program, adequate checking of line pilots for currency, adequate documentation of line pilot training, a company Flight Safety Program, and a formal system of maintenance control all contributed to a less than adequate safety culture within the company.

CASA surveillance

The March 1999 fatal accident may have justified an increase in surveillance as per CASA guidelines. CASA management however, did not revise surveillance of the operator following recommendations from area managers and Flying Operations Inspectors. As a result, the safety oversight of the operator by CASA may have been less than recommended in CASA guidelines. Following this latest occurrence, CASA subsequently increased its level of surveillance of the operator.

CASA surveillance documentation

Examination of the CASA aircraft file for this helicopter and other aircraft files, has identified a trend of non-compliance by operators to resolve discrepancies noted on the ASR ASSP 604 form. Non-acquittal of ASRs could also display a trend of non-compliance to airworthiness issues.

1. The pilot did not have adequate knowledge in recognition of operational conditions that could have induced LTE.

2. The pilot did not correctly identify operational conditions that could have induced LTE.

3. The pilot did not implement adequate recovery techniques to counteract the onset of LTE.

As a result of this investigation the Australian Transport Safety Bureau has identified a safety deficiency related to pilot training. The results of the investigation of this safety deficiency will be published on the Australian Transport Safety Bureau website.

As a result of this investigation on 9 March 2001, the Australian Transport Safety Bureau issued the following recommendations to the Civil Aviation Safety Authority.

R20010015

The Australian Transport Safety Bureau recommends the Civil Aviation Safety Authority consider revising Civil Aviation Safety Authority Safety Aircraft Survey Report 604 form to require a response date for acquittal of discrepancies.

CASA response to recommendation R20010015 dated 10 April 2001.

The ASR (Aircraft Survey Report) can be assigned either Code A, B or C.

Code A identifies a defect or damage to the aircraft, and requires that maintenance to rectify the defect or damage must be carried out before further flight. This acquittal requirement is very specific in relation to the aircraft operational requirements. However, if the Certificate of Registration (CoR) holder removes the aircraft from service, an actual acquittal date has no relevance. The requirement to perform the maintenance before further flight remains.

Code B is a direction under CAR 38(1) to have defects or damaged assessed and rectified as necessary. The Code B direction is used to bring a defect or damage to the attention of the CoR holder, the pilot or operator where:

- A defect or damage to the attention of the CoR holder, the pilot or operator where:

- The inspector considers the defect or damage to be minor, or; The inspection carried out on the aircraft does not enable proper determination if the defect or damage is major. In which case the C of R holder, the pilot or operator is responsible to have an assessment carried out to determine the true nature of the defect or damage, and have appropriate rectification carried out. While the assessment needs to be done prior to further flight, the rectification might not be accomplished for some time in the future, where, for instance, the defect is minor and falls within the provision of Permissible Unserviceabilities.

Code C is used to give the C of R holder formal notification of a non-compliance with a requirement or condition imposed under the regulations and is judged, on the basis of the inspection, not to have an immediate adverse effect on safety. However, the matter is required to be assessed and rectified at the earliest opportunity.

As can be seen from the above discussion, it is often the case that an acquittal date cannot practically be imposed at the time of issue of the ASR. However, CASA is currently reviewing the ASR process to see how that process might be more closely monitored.

ATSB actions concerning CASA response to R20010015

The ATSB classifies this recommendation OPEN- MONITOR, pending CASA review of the ASR process.

As a result of this investigation on 9 March 2001, the Australian Transport Safety Bureau issued the following recommendations to the Civil Aviation Safety Authority.

R20010016

The Australian Transport Safety Bureau recommends the Civil Aviation Safety Authority consider revising Civil Aviation Safety Authority Safety Trend Indicator form to indicate organisational non-acquittal of Aircraft Survey Report ASSP 604 forms within the last 12 months.

CASA Response to Recommendation R20010016 dated 10 April 2001.

Non-acquittal of an ASR within a particular time period does not necessary reflect poorly on an operator. Consequently, for ASR acquittal information to be meaningful, in regards to Safety Trending, would need complex and prescriptive criteria to be developed and followed by CASA inspectors in the field.

Depending on the outcome of the review mentioned in Para 2 above, CASA would also explore what useful application that information might have in regard to the Safety Trend Indicator.

ATSB actions concerning CASA response to R20010016

The ATSB classifies this recommendation OPEN- MONITOR, pending CASA review of the ASR process.