FACTUAL INFORMATION
History of the flight
At about 1730 Eastern Standard Time on 15 August 2004, the pilot
of a Mooney Aircraft Corporation M20K aircraft, registered VH-DXZ,
departed Cobar, NSW, on a private flight to Caloundra, Qld. The
flight was conducted under the visual flight rules (VFR), with the
latter part at night.
At about 2015, several people saw and heard the aircraft, with
its wing tip strobe lights flashing, flying low in a northerly
direction over Bokarina, 8 km north-north-east of Caloundra
aerodrome. One witness said that the engine sounded as though it
was 'struggling and cutting out'. Two other witnesses described the
engine sound as a 'steady drone', while another said it sounded
like it was 'turning at low [revolutions], as if it was powered
down for a landing'.
The aircraft was then observed to turn east and cross the coast
before descending steeply and impacting the water. The impact was
accompanied by a bright flash. The aircraft wreckage was located 4
days later, approximately 1.5 km east of Bokarina beach, at a depth
of about 16 m. The pilot, who owned the aircraft and was the sole
occupant, did not survive the impact.
Earlier that afternoon, the pilot had flown from Caloundra to
Cobar with one passenger. The passenger remained at Cobar and
reported that the flight from Caloundra had been uneventful and
that they arrived at Cobar at about 1700. The refueller advised
that the pilot refuelled the aircraft with 156 L of avgas
(apparently to full tanks) and checked the engine oil before
departing on the return flight to Caloundra.
The pilot lived at Bokarina and family members reported that he
did not normally fly over his home on returning from a flight. They
indicated that the pilot's car was at the aerodrome, so he did not
need to be met and driven home. They assumed that the purpose of
flying over the house was to let them know that he would be home
soon.
Recorded information
The pilot was not required to report to air traffic control
during the flight and there was no record of him having done so.
The Caloundra Common Traffic Advisory Frequency did not have a
recording capability.
A pilot conducting a VFR flight was required to operate the
aircraft's secondary surveillance radar (SSR) transponder on code
1200 in airspace not subject to air traffic control. The Mooney's
SSR track for the flight was recorded by The
Australian Advanced Air Traffic System. That data showed that
the aircraft first appeared on radar at 1903, north of Moree, NSW,
on the direct track from Cobar to Caloundra at 11,300 ft. The
aircraft maintained that altitude until 1937, when it commenced
descent, passing through 10,000 ft at about 1940, and 5,000 ft at
about 1958. It maintained a steady track and descent profile, and
was overhead Caloundra at 2014, at 1,140 ft. The aircraft then
maintained a relatively constant altitude, and tracked north
towards Bokarina (Figure 1).
At 2015, the aircraft commenced a further descent and when
overhead Bokarina, turned right and headed east-north-east, towards
the ocean. Radar data indicated that the aircraft descended to 442
ft about the time it flew over the beach. The aircraft's altitude
then increased, reaching a maximum of 742 ft. The last valid radar
information was recorded at 2016:13, and indicated that the
aircraft had entered a descending right turn. The recorded radar
data did not reveal any abrupt or abnormal changes in the
aircraft's altitude, groundspeed, or track. The recorded speeds
were consistent with normal cruise and descent speeds for the
aircraft type (Appendix A).
Figure 1: The aircraft's radar-recorded
track
Pilot information
The pilot purchased the aircraft in May 1994, and was issued
with a private pilot (aeroplane) licence in July 1994. His logbook
recorded his total flying experience at the time of the accident as
about 1800 hours, 142 of which were at night. In April, May and
June 2004, the pilot logged 5, 0.5 and 5.4 hours night flying
respectively, all in DXZ. In those same months, he also logged
20.8, 12.3, and 25.4 hours day flying. The pilot last flew at night
on 19 June 2004, and in actual or simulated instrument
meteorological conditions, during 1998. His total instrument flight
time was recorded as 32.4 hours.
The pilot was issued with a night VFR rating on 11 June 1998.
There was no evidence that he had ever held an instrument rating.
His three most recent flight reviews were completed on 29 March
2003, 18 November 2001, and 24 November 2000. They were logged as
day flights, with no instrument or night flight recorded.
The pilot's family reported that he was well rested before the
flight, was not affected by any illness and had never smoked
cigarettes.
A person who spoke to the pilot while he was at Cobar reported
that he said that it had been a busy day, and that he had not had
any lunch, but was carrying some nuts and a drink on the
aircraft.
Aircraft information
The aircraft was manufactured in the US in 1988, and was
imported into Australia in the same year. At the time of the
accident, it had accumulated about 2,868 flight hours. The aircraft
was equipped and maintained in the instrument flight rules (IFR)
category. It was fitted with a turbo-charged, piston engine which
had accumulated about 180 hours since the last overhaul.
The aircraft cabin was not pressurised, but was fitted with a
supplemental oxygen system. The organisation that maintained the
aircraft reported that the supplemental oxygen system tank was
empty. There was no indication that the oxygen tank had been
charged at Cobar.
A review of the aircraft's maintenance records revealed that the
requirements of Airworthiness Directives (AD) RAD/43 and
RAD/471 were due to be completed in
July 2004, but had not been carried out. No other discrepancies
were noted, and no defects had been recorded on the maintenance
release.
The aircraft was fitted with an electrically-driven standby
vacuum system for providing pneumatic power to the gyroscopic
instruments, and a Century 2000 autopilot system.
Meteorological information
Information provided by the Bureau of Meteorology indicated that
the weather conditions in the Bokarina area at the time of the
accident were benign. Smoke areas were forecast below 6,000 ft with
visibility reducing to 4,000 m in smoke, and 1,000 m in thick
smoke. The terminal area forecast for Maroochydore aerodrome (15 km
north-north-west of Bokarina), issued at 1813, predicted visibility
greater than 10 km and scattered cloud at 3,000 ft. None of the
witnesses reported that smoke, cloud or haze affected their ability
to see the aircraft.
The QNH2 recorded by the automatic
weather station at Maroochydore at 2020 on the day of the accident
was 1014 hPa.
On 15 August 2004 at the accident location, astronomical
twilight occurred at 1846 and the moon set at 16373. Two cargo ships were located east of
Maroochydore at the time of the occurrence, at least one of which
was at anchor, and therefore displaying lights4. Several hours after the accident,
witnesses observed two large ships moored east of Maroochydore
which were displaying deck lights.
Wreckage and impact information
The wreckage was raised from the seabed on 28 August 2004
(Figure 2). Most of the aircraft was recovered, including the
engine, fuselage, left wing, all three propeller blades and the
propeller hub. The right horizontal stabiliser, right elevator, and
parts of the right wing were not recovered.
An examination of the wreckage indicated that:
- The aircraft was banked right, and in a nose-down attitude of
approximately 45 degrees when it struck the water. - The nature of the damage to the engine crankshaft and the
propeller blades was consistent with the engine delivering high
power at impact. - The frangible plastic drive shaft of the engine driven vacuum
pump had failed under a sideways load. The drive shaft of the
electrically-driven vacuum pump was intact. - Damage to the gyroscopes in the artificial horizon and
directional indicator flight instruments was consistent with
gyroscopic rotation at impact. - The light globes in the artificial horizon and the directional
indicator flight instruments were receiving electrical power at
impact. - The landing gear was retracted, and the wing flaps were
extended about 10 degrees, at impact. - The altimeter subscale was set at 1015.
- There was evidence of a short duration, post-impact fire.
Impact and salt water corrosion damage precluded a determination
of the serviceability of the automatic pilot system and its
operational status during the final stages of the flight. None of
the windscreen was recovered. There was no evidence in the
recovered wreckage that the aircraft had struck a bird or a bat
during flight.
The extent of airframe disruption and the missing parts of the
right wing, horizontal stabiliser and right elevator prevented a
comprehensive assessment of the functionality of the flight
controls at impact.
Figure 2: Recovery of the main wreckage
Regulatory aspects
The pilot's night VFR rating authorised him to act as pilot in
command of private or aerial work flights at night under the VFR.
Civil Aviation Order (CAO) 40.2.2 detailed the flight tests and
other requirements for the issue of a night VFR rating. The test
requirements included recovery from unusual attitudes, basic turns,
and straight and level flight, which were required to be conducted
solely by reference to flight instruments. The CAO also required
that training for the issue of a night VFR rating included at least
one landing at an aerodrome 'that is not in an area that has
sufficient ground lighting to create a discernible horizon'.
Once issued, a night VFR rating remained permanently valid. To
exercise the privileges of the rating, a pilot needed to meet
certain minimum recent experience requirements. There was no
requirement for the holder of a night VFR rating to have any recent
instrument flight time prior to conducting a flight at night
5.
Except during takeoff, landing, or radar vectoring, the pilot of
a night VFR flight was required to ensure than the aircraft
remained at or above the calculated lowest safe altitude (LSALT)
while further than 3 NM from the destination aerodrome. The minimum
LSALT for the Bokarina area was 1,500 ft. Aircraft operating over
populated areas were generally required to remain at or above 1,000
ft.
A pilot was required to satisfactorily complete an aeroplane
flight review every 2 years. There were no published requirements
or guidance material regarding theoretical knowledge or practical
skills (such as flight conducted solely by reference to flight
instruments) required to be demonstrated by pilots undergoing an
aeroplane flight review.
Medical and pathological information
The pilot held a valid Class 2 Medical Certificate at the time
of the occurrence. His medical records indicated that he had
undergone a stapedectomy6 operation
on his left ear about 22 years before the accident. He underwent a
stapedectomy on his right ear on 11 April 2002 because of hearing
loss. However, due to a post-operative decline in hearing and
persistent balance problems, the prosthesis was removed on 24 April
2002. During two subsequent telephone conversations with the
surgeon in June and July 2002, the pilot reported that he was still
dizzy, couldn't look up and down quickly, and was still
unsteady.
The pilot underwent a Class 2 aviation medical examination on 1
March 2004. The designated aviation medical examiner who performed
that examination reported that the pilot had advised of no ongoing
dizziness, disorientation, or other related problems.
A pathological examination did not identify any indication of a
pre-existing medical condition that could have contributed to the
development of the accident. It was not possible to establish when,
or what, the pilot had last eaten.
Hypoxia
Hypoxia is a condition in which there is reduced oxygen supply
to the body. Available oxygen decreases with increased altitude,
such that at 12,000 ft, brain oxygen saturation is approximately
87%, compared with sea level saturation of 96%.
The investigation calculated that if the entire cruise segment of
the flight had been conducted at 11,300 ft, the aircraft would have
been at that level for almost 2 hours.
The US Federal Aviation Administration7 (FAA) recommended that pilots use
supplemental oxygen when flying above 10,000 ft during the day and
above 5,000 ft at night when the eyes become more sensitive to
oxygen deprivation.
The Mooney M20K Aircraft Flight Manual stated that 'supplemental
oxygen should be used when cruising above 12,500 feet. It is often
advisable to use oxygen at altitude lower than 12,500 feet under
conditions of night flying, fatigue, …'.
Civil Aviation Order (CAO) Part 20.4 paragraph 6.1 stated:
A flight crew member who is on flight deck duty in an
unpressurised aircraft must be provided with, and continuously use,
supplemental oxygen at all times during which the aircraft flies
above 10,000 feet altitude.
An article8 in Flight Safety
Australia magazine stated '[a]fter vision, the tissues most
affected by hypoxia are those areas of the brain associated with
judgement, self-criticism and the accurate performance of mental
tasks'. An associated article9 in the
same magazine indicated that the use of oxygen during night flight
below 10,000 ft resulted in an increase in alertness and cognitive
function, and a reduction in fatigue. Studies of the effects of
exposure to altitudes between 10,000 ft and 15,000 ft have
consistently shown small to moderate effects on human performance.
Those effects included a reduction in night and peripheral vision,
increased drowsiness, decreased response time, decreased short-term
memory capacity, and poorer performance on complex and reasoning
tasks.
The FAA Civil Aerospace Medical Institute Human Factors Research
Laboratory in Oklahoma City, USA advised that restoration of a sea
level atmosphere following exposure to hypoxic conditions caused
rapid physiological recovery, but that cognitive recovery was
slower.
Fatigue
Fatigue results from inadequate rest over a period of time, and
leads to physical and mental impairment. The effects of fatigue
include decreased short-term memory, slowed reaction time,
decreased work efficiency, increased variability in work
performance, a tendency to accept lower levels of performance and
not correct errors. Not consuming food regularly is known to
exacerbate the effects of fatigue.
Based on previous flights recorded in the pilot's logbook, the
total flight time for the trip from Caloundra to Cobar and return
to Caloundra would probably have been between 6.4 and 6.9
hours.
Stapedectomy
Stapedectomy involved a small risk of ongoing episodes of
dizziness and hearing loss10.
However, according to an article published in 1998 in the journal
Otolaryngology - Head and Neck Surgery11,
The FAA [Federal Aviation Administration] has always had the
most experience with aircrew returning to flying duties after
stapedectomy. The civilian track record is excellent with no
reported cases of sudden incapacitating vertigo, sudden hearing
loss, or other poststapedectomy related sequelae.
Spatial disorientation
Spatial disorientation describes an in-flight situation in which
a pilot does not correctly sense the position, motion or attitude
of the aircraft, and may be unable to tell which way is up. A pilot
operating under the VFR determines the attitude of an aircraft by
reference to the natural horizon or surface features. If these
references are not visible, the pilot must use the flight
instruments to determine the aircraft's attitude.
The risks of non-instrument rated pilots flying in conditions in
which they are not able to orientate the aircraft by visual
reference have been well known for over 50 years. During testing
conducted on a group of non-instrument rated pilots, the average
time before loss of control of the aircraft, after visual reference
was lost, was 178 seconds12. An
article titled 'Fatal Night Flight' in the Civil Aviation Safety
Authority (CASA) magazine Flight Safety Australia (May-June 2005)
stated that:
[v]isual disorientation is a distinct possibility on dark nights
or away from areas of extensive ground lighting. Disorientation can
be caused by sudden loss of visual reference such as when turning
away from a well lighted area towards an area without ground
lighting.
The article also stated that 'it is imperative that Night VFR
pilots are competent and current in instrument flight'.
US FAA Advisory Circular 60-4A, Pilot's Spatial Disorientation,
was published in 1983 and was intended to inform pilots of the
hazards associated with disorientation caused by loss of visual
reference with the surface. It included the following
information:
Tests conducted with qualified instrument pilots indicate that
it can take as much as 35 seconds to establish full control by
instruments after the loss of visual reference with the
surface.Surface references and the natural horizon may at times become
obscured, although visibility may be above visual flight rule
minimums. The lack of natural horizon or surface reference is
common on over water flights, at night, and especially at night in
extremely sparsely populated areas, or in low visibility
conditions.
Recent night VFR accident
On the evening of 17 October 2003, an
air ambulance Bell 407 helicopter descended into the sea near
Mackay, Qld. The ATSB investigation (200304282) was unable to
determine, with certainty, what factors led to loss of control of
the helicopter. The investigation considered that although the
forecast weather conditions did not necessarily preclude flight
under the night VFR rules, the lack of a visible horizon and
surface lighting, and the pilot's limited instrument flying
experience may have contributed to the accident. The investigation
concluded that the circumstances of the accident were consistent
with loss of control due to the pilot becoming spatially
disoriented.
- AD/RAD/43 required a biennial altimeter and
encoder check and AD/RAD/47 required a biennial transponder
check. - Sea-level atmospheric pressure.
- Information obtained from Geoscience Australia
website http://www.ga.gov.au/nmd/geodesy/astro/ - Vessels
over 100 m long and at anchor are required to display white lights
at either end of the vessel and available working lights or
equivalent to illuminate the decks. - In
contrast, the holder of an instrument rating was required to
undergo an annual instrument flight test, and comply with flight
and instrument approach recency requirements, in order to keep the
instrument rating current. - Stapedectomy is an operation to remove the
fixed stapes [the third middle ear bone] and to replace it with a
prosthesis. That allows sound vibrations to be transmitted properly
to the inner ear for improved hearing.
http://www.bcm.edu/oto/clinic/educate/stapled.html - Federal
Aviation Administration. 2003. Advisory Circular AC 61-107A
Operations of Aircraft at Altitudes Above 25,000 feet MSL
and/or Mach Numbers (MMO) Greater than .75. - Brock,
J. & Bencke, R. 1998. Hypoxia. Flight Safety
Australia. Volume 3 Number 1. Civil Aviation Safety Authority.
Canberra. - Thom,
A. 1998. Improved Performance. Flight Safety Australia.
Volume 3 Number 1. Civil Aviation Safety Authority. Canberra. - http://www.bcm.edu/oto/clinic/educate/stapled.html
- Thiringer, J.K. & Arriaga, M.A. 1998.
Stapedectomy in Military Aircrew. Otolaryngology - Head
and Neck Surgery. Volume 118 Number 1. January 1998. - Bryan, L.A., Stonecipher, J.W. & Aron, K.
1954. 180-degree turn experiment. University of Illinois
Bulletin. 54(11), 1-52.