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.