Bell Helicopter Co 47G-4A, VH-MTX

1. The pilot was not recently experienced on the occurrence
   helicopter type.
2. The pilot in command allowed the helicopter to move laterally
   during the lift-off to the hover.
3. The pilot in command did not raise the helicopter to a hover
   height sufficient to prevent contact with the mobile platform.

Post-occurrence technical examination of the helicopter did not
reveal any evidence of an airframe, engine or system fault that may
have contributed to the accident. In addition, examination of the
mobile platform did not reveal any evidence of it having moved
throughout the rollover sequence.

The circumstances of the accident are consistent with the
phenomenon known as dynamic rollover. Scrape marks from the
helicopter's right skid were found on the lip along the right side
of the mobile platform. That indicated that the helicopter was not
raised to a height sufficient to clear the platform in the event of
lateral movement. There was no wind reported at the time of the
occurrence that could have contributed to the lateral movement. The
pilot had extensive flying experience and normally flew a mix of
different types, including a mix of European and North American
types. Due to that experience, the investigation considered that
confusion with respect to correct flight control input to control
yaw was unlikely.

If the pilot had prevented the lateral movement of the
helicopter during the lift off to the hover, and had raised the
helicopter to a hover height sufficient to clear the platform,
dynamic rollover would most probably have not occurred. Therefore,
the investigation considered that the design or use of the mobile
platform was not a factor in the occurrence.

The pilot had not flown a Bell 47 type helicopter during the
preceding three months, and had not previously flown a
turbine-powered Bell 47. It is likely that the pilot's lack of
recency in the helicopter type, combined with his not having flown
a turbine-powered Bell 47 previously, contributed to his:

• not making sufficient flight control input to correct the right
  lateral movement during the lift-off to the hover
• not raising the helicopter to a hover height sufficient to
  prevent contact with the platform.

The pilot's injuries were consistent with him being struck by
the main transmission assembly as it separated from its mount as a
result of the dynamics associated with main rotor ground
contact.

History of the flight

At approximately 0830 EST, the pilot of the Bell 47G-4A
turbine-powered (Soloy) helicopter, registered VH-MTX, was
conducting a lift-off to the hover from a mobile helicopter landing
site (HLS)¹ at Caboolture aerodrome, when the helicopter
rolled onto its right side. Weather conditions at the time of the
occurrence were reported to be '…little or no wind, warm and humid,
some cloud but clearing.' The helicopter was substantially damaged
and there was no post-occurrence fire. The pilot, who occupied the
left seat², was fatally injured and the passenger, who
occupied the right seat, sustained minor injuries.

Pilot in command

The pilot held an Airline Transport Pilot (Helicopter) Licence,
a Commercial Pilot (Aeroplane) Licence, a Command Multi Engine
Instrument Rating (CMEIR) (Helicopter), a CMEIR (Aeroplane), and a
Grade 1 Instructor (Helicopter) Rating. According to his pilot
flying logbooks, he had accumulated approximately 8,293 hours total
flying experience, of which approximately 7,180 hours was on
helicopters, including 14.8 hours on the Bell 47G helicopter type.
He had flown 2.0 hours in the last 30 days and 15.7 hours in the
preceding 90 days. His last flight prior to the occurrence flight
was nine days previously in a Bell 206 type helicopter. He had last
flown a Bell 47G type helicopter on 19 December 2002, including
taking off from and landing back on the mobile platform involved in
the occurrence. He had not previously flown a turbine-powered Bell
47G helicopter.

The pilot was endorsed to fly Bell 47G type helicopters in
accordance with Section 40.3.0 of the Civil Aviation Orders (CAO).
In accordance with paragraph 3.3 of those orders, he was permitted
to fly turbine-powered Bell 47G helicopters without further
endorsement. The operator also reported that, in accordance with
paragraph 3A.4 of CAO 40.3.0, prior to the occurrence flight, the
pilot was offered refresher training in the turbine-powered Bell
47G type, however the pilot declined that offer.

The pilot met the recency requirements of Civil Aviation
Regulation 5.178, having completed CMEIR (Helicopter) and
Instructor (Helicopter) Rating renewals on 13 May 2002, in a Bell
412 helicopter type.

Due to the nature of his employment, the pilot had flown 10
aircraft types in the preceding 12 months, of which 7 were
helicopters. Those helicopter types included a mix of European and
North American types, a mix of single engine and multi-engine
types³, and a mix of turbine and piston engine types.
Most of the pilot's helicopter flying experience was in turbine
engine types. The pilot was experienced in operating helicopters
from mobile platforms.

Passenger

The passenger was employed by the same organisation as the pilot
in command. He was an experienced helicopter pilot, who reported
that he had accumulated approximately 4,700 hours total flying
experience, of which approximately 4,500 hours was on helicopters.
He reported that he was not in current flying experience. According
to witnesses, he did not have his hands or feet near the flying
controls during the occurrence.

Medical information

The pilot's aviation medical certificate was valid and carried a
restriction for him to have available reading vision correction. A
review of his medical records, investigation interviews, results of
the post-mortem examination and toxicological testing, found no
evidence of pre-existing medical conditions or the presence of any
substance that may have influenced his performance.

Survival information

Four-point restraint harnesses with inertia reel shoulder straps
were fitted at the pilot and right side passenger positions.
Post-occurrence technical examination revealed that they were
firmly secured to their mounts, and the inertia reels appeared to
operate normally. The pilot occupied the left seat and remained
restrained during the rollover sequence. He sustained severe impact
injuries to the rear of the upper torso and lacerations to the back
of the head.

Helicopter information

Type: Bell 47 helicopter

Model: 47G-4A (Soloy)

Registration: VH-MTX

Serial Number: 7765

Year of manufacture 1971

Engine: Rolls Royce 250-C18

Total time in service: Approximately 5,570 hours

Maintenance release: Number 09425 issued 14/03/03 at 5,549.7
hours

The helicopter had been imported from Japan in October 2002,
receiving an Australian Certificate of Airworthiness in December
2002. The helicopter was maintained in accordance with the
manufacturer's and CASA approved documents and schedules, and had
flown approximately 20 hours since its last 100-hourly
inspection.

Damage to the helicopter

The helicopter came to rest on its right side, with its right
skid landing gear resting on the right rear corner of the platform.
The canopy bubble had shattered. The main rotor, mast and
transmission assembly had detached from the helicopter as a single
unit and was located next to the helicopter. The 'white' main rotor
blade⁴ was lying across the cockpit. Evidence, in the
form of multiple main and tail rotor impact marks, was observed in
the ground with an area of burned grass beneath the helicopter's
engine exhaust. One of the tail rotor blades had detached and was
located approximately 30 metres from the helicopter. The tip of the
'red' main rotor blade was found approximately 150 metres to the
east of the helicopter. Both arms of the main rotor stabiliser bar
had fractured and were found within 20 metres of the helicopter.
All major components were located and identified at the site.
Post-occurrence technical examination of the helicopter did not
reveal any evidence of an airframe, engine or system fault that may
have contributed to the accident.

Mobile platform information

The mobile platform was a flat-based metal construction on
wheels, measuring 365 x 300 cm and was approximately 22 cm above
the ground. A 5 cm high metal lip ran along both sides of the
platform. There were no metal lips at the front or rear of the
platform. The front wheels were positioned forward of the base and
were approximately 27 cm in diameter. The rear wheel axles were in
line with the platform base, allowing the 38 cm-diameter wheels to
sit approximately 18 cm above the base. There were two prominent
worn strips along the base approximately 38 cm from the side lips,
which indicated the usual positioning of the helicopter skids on
the platform. At the time of the occurrence, the platform was
connected to a small tractor. The tractor brake was engaged and
there was no evidence of the tractor having moved throughout the
accident sequence.

Civil Aviation Regulation 92 (1) states that:

An aircraft shall not land at, or take-off from, any place
unless:

(d) the place… is suitable for use as an aerodrome for the
purposes of the landing and taking-off of aircraft;

and, having regard to all the circumstances of the proposed
landing or take-off (including prevailing weather conditions), the
aircraft can land at, or take-off from, the place in safety.

GEN 2.2 of the Aeronautical Information Publication,
defines an aerodrome as:

A defined area of land or water (including any buildings,
installations and equipment) intended to be used either wholly or
in part for the arrival, departure and movement of aircraft.

Guidelines for the establishment and use of HLS are at Civil
Aviation Advisory Publication (CAAP) 92-2 (1), which defined an HLS
as:

…a place that may be used as an aerodrome for the purposes of
landing or taking off of helicopters.

The definition of '…place…' in CAAP 92-2 (1) included '…on a
structure…'.

There is no CASA regulation or guidance concerning the design or
use of mobile platforms. Additionally, international standards and
recommended practices contained in Annex 14 to the International
Civil Aviation Organization (ICAO) Convention on International
Civil Aviation, Aerodromes, Volume II - Heliports, do not
refer to mobile platforms. A search of international regulatory
authorities found no documentary guidance regarding design or use
of mobile platforms.

The investigation found that mobile platforms of varying design
are used throughout the Australian civil helicopter industry. Some
of those designs incorporated side lips and others had no
protrusions above the platform surface. Most of the platforms were
tractor-towed.

Damage to the mobile platform

Examination of the mobile platform revealed two fresh scratch
marks on the right lip approximately 50-85 cm from the rear of the
platform. Also evident were fresh gouges on the rear edge of the
platform, adjacent to the right wheel axle, which indicated that
the helicopter had been moving rearwards as it contacted the lip.
Examination of the platform did not reveal any evidence of it
having moved throughout the rollover sequence.

Organisational information

Pilot employees from the same organisation as the occurrence
pilot reported that they each received funding for up to 40 flying
hours each financial year to maintain recency on selected aircraft
types. They also reported that, due to the nature of their
employment, some pilots had a requirement to maintain recency on a
number of types simultaneously.

Dynamic rollover

The phenomenon known as dynamic rollover was described in
helicopter textbooks, training manuals and industry and safety
publications. It was included at:

• items 10.7 and 12.1 of the CASA Day (VFR) Syllabus -
  Helicopters, Issue 3, January 1999, which applied from Student
  through to Commercial Helicopter Licence standard
• item 2.1.14 of the Air Transport Pilot (Helicopter) Licence
  - Aeronautical Knowledge Syllabus, Issue 3, January 1999.

Dynamic rollover has been defined as:

The occurrence of a rolling motion, while any part of the
landing gear is acting as a pivot that causes the aircraft to
exceed a critical angle and roll over⁵.

Another definition states that:

Put simply, dynamic rollover is the result of the helicopter
developing excess angular momentum about the skid in
contact⁶...

Dynamic rollover typically occurs when a critical rollover angle
is exceeded. That angle is dependent upon control limits and in
most helicopters is in the order of 15 degrees. Accidents
attributed to dynamic rollover have occurred previously on a number
of surfaces, including open flat grassed surfaces.