following article appeared in the February 2014 Issue of
Aviation Safety Spotlight. Reproduced
with their kind permission.]
By Paul Cross. (Deputy Director Safety Communications,
A Mirage at Butterworth in 'landing'
[This photograph dates from the era 1986-88, as it shows 79SQN
markings. 79SQN took over 3SQN's Mirage
aircraft and a large majority of the Mirage personnel on 31 March
1986, as 3SQN was due to re-establish in Australia, introducing
F-18s to RAAF operations.]
About 2pm on 6 July 1976, Mirage A3-64 was
landing from a practice ground-control approach (GCA) and impacted
Mirage aircraft A3-26 which was lined-up on runway 18, waiting for
A3-26 was destroyed and its pilot killed instantly.
A3-64 was also destroyed, but the pilot escaped without
Both aircraft were engulfed in flames almost immediately after
impact. As the aircraft separated, A3-26 continued to burn
fiercely as did A3-64, with the exception of the
partially-broken-away front fuselage section. About three
minutes after impact, the first crash vehicle arrived at A3-64 and
had no difficulty in rapidly extinguishing the fire.
Simultaneously, other crash-rescue vehicles were directed to
A3-26, where the fire in the vicinity of the cockpit area was
quickly controlled. However, considerable difficulty was
encountered in containing and extinguishing the fuselage fire
because of fuel leakage and numerous flashback fires.
ambulance arrived after about seven minutes and the duty medical
officer declared the pilot deceased.
The pilot of A3-26 was a Category B fighter pilot with a total
of 1,187.4 hours, including 761.5 on Mirage and an authorised
squadron test pilot. The pilot of A3-64 was a Category C
fighter pilot and considered most dependable, conservative in his
approach to flying and well aware of his capabilities and
The impact scene.
Following the investigation, the Court of Inquiry
outlined several factors that were integral to the tragic events
of 6 July:
Three days before the accident, the pilot of A3-64 had
returned from a 54-day holiday in Europe. He would have, in
that time, established a sleeping pattern consistent with the
northern hemisphere summer and, having travelled east to return to
Butterworth, would have experienced a time-shift of more than
seven-and-a-half hours. His sleep pattern on return showed
evidence of significant disruption consistent with interference to
the normal circadian rhythm.
The Court noted, “One response to circadian dysrhythmia
relates to the tendency for mental blocking or lapses in
attention. This phenomenon, termed response blocking, has
been under investigation in the analysis of accidents, where
subjects have apparently failed to see, interpret or react to
apparent or dangerous situations”.
Other physiological factors could also have influenced the
pilot’s performance level, including his loss of heat
acclimatisation and sleep deficit. It was accepted that
there would have been a loss of acclimatisation after 54 days in a
temperate climate and that it was very unlikely that the pilot had
re-acclimatised in the three days before the accident.
lengthy sorties and a low fluid intake (one cup of black tea and
a drink of water) would lead to a body-fluid deficit. The
effect of this deficit and loss of acclimatisation would be to
increase the individual’s susceptibility to the effects of heat
with the resultant fatigue.”
On the two nights before the accident, the pilot had only
slept a total of nine-and-a-half hours.
“Sleep deficiency will result in fatigue…
fatigue produces a further decrease in performance in an
individual subjected to time zone shift.”
Following a lengthy break, the pilot of A3-64 was considered
“a little rusty” by his supervisor in a simulator refresher before
flying. His flying of the GCA that culminated in the
accident was flown very accurately. It was thought that the
attention to accuracy could impose a “greater than usual” workload
on top of an already medium-to-high workload situation. “The
pilot was in the habit of checking his glideslope and centreline
at the commencement of the approach then monitoring his approach
on TACAN, which he did. Because of his lack of currency he
only monitored the TACAN range but did not compare expected
height with actual height or monitor approach on the
air-to-ground radar. That is; he was load shedding.”
The pilot of A3-64 at the four-mile point was given an
instruction by ATC to check wheels and to overshoot at
minimas. This call was given amid glideslope and heading
information and was acknowledged by the pilot. However, he
did not obey the overshoot instruction and was confident in his
own mind that after GCA minimas he had been given clearance to
“An important point in regard to the
four-mile call is the fact that there was no laid-down requirement
to read back the key executive word of such a clearance.”
“In this particular case, read back of the
executive ‘overshoot’, firstly, would have confirmed with the
controller that the clearance had been heard and understood and,
secondly would have reinforced the executive in the pilot’s short
term memory, enhancing retrieval or, alternatively, reducing the
probability of substitution.”
“The Court therefore believes that had
overshoot been read back, there is a high probability that the
causation chain would have been broken.”
hand-off call given to A3-64 by the controller was “continue
visually and call the tower on the go.” In contrast, the
standard call, as contained in the manual was, “look ahead and
The hand-off call was non-standard and importantly did not
contain the essential executive word overshoot. This was not
a positive and reinforcing four-mile call and contained the
ambiguous phrase “on the go”. Some pilots interviewed
contended that ”on the go” was consistent with the continuation of
a touch-and-go but all, including the pilot of A3-64, stated they
would not interpret the phrase as a change of clearance but would
respond to the previous instruction to overshoot and at the least
query their clearance.
and Arrival Procedures
It was accepted and common practice at Butterworth to line-up
aircraft with other aircraft on finals. Some controllers
would not have done this with an approaching Mirage within three
miles of touchdown but at the time of this accident no distances
were laid down for visual meteorological conditions (VMC)
operations. In this particular instance controllers thought
the approaching aircraft was beyond four miles—when in fact it was
Had A3-26 been positioned at the runway threshold, there was a
possibility that A3-64 might have cleared it, but A3-26 was some
500 feet further along the runway — close to the touchdown point
for a ground-controlled approach. This would create a visual
problem for the approaching pilot.
Failure to See
The pilot of A3-64 did not perceive A3-26 lining up 500 feet
from the threshold of runway 18 and there were a number of factors
that could account for this.
A camouflage-painted aircraft sitting on the rubber-darkened
section in the centre of the runway is not so easy to see.
It has a very low contrast ratio and added to this would be the
hot gasses emitting from the engine, reducing sharpness of the
aircraft’s outline. A3-26 was stationary, reducing the
approaching pilot’s visual cues that he was on a collision course.
The position of the sun made it unlikely that any glint from
the Mirage’s canopy would be seen by the approaching aircraft.
“During a simulation it was apparent that
the target aircraft became invisible when displaced one to two
degrees from the central vision. Thus, unless A3-26 had been
fixated centrally, the probability of target detection and
recognition would have been very small.
“Although many pilots are unaware of
reflections in aircraft windscreens, this does not alter the fact
that they impose an additional load on the visual system and
reduce contrast ratios of targets seen through these reflections,
thereby reducing the probability of successfully detecting a
low-contrast visual stimulus.”
Another factor is that the pilot of A3-64 did not expect to
see an aircraft lined-up on runway 18, if he thought he was
cleared to land. Further, he did not expect an aircraft to
be lined up 500 feet from the threshold, where A3-26 was
“These factors will affect both the pilot’s
visual search strategy and also the perception formed by the brain
in response to a particular visual stimuli. The probability
of perceiving an aircraft on the runway is likely to be less in
these circumstances for a just perceptible stimulus.”
A3-26 represented a visual target with a low probability of
detection. The effects of fatigue and circadian dysrhythmia
may have aggravated the situation by raising visual thresholds,
particularly in the periphery, where high workload situations can
lead to tunnelling of vision.
The Court concluded that while A3-26 was seeable, the
possibility of it being seen by the pilot of A3-64 was remote.
Approach view on finals at Butterworth with a
camouflaged Mirage holding in the rubberised area.
At the time of the accident, a trainee controller from the
RMAF was under supervision and working in the Tower 1
position. From the time the pilot of A3-26 called “ready”,
there was a delay of one minute before he was given a line-up
clearance. Although there was other traffic in the pattern,
there were opportunities to line up A3-26 and obtain a departure
clearance from approach.
After clearance from the approach controller was given, there
was further delay and discussion about the possibility of an
airborne confliction between A3-26 and A3-64 and the decision was
made to await the overshoot by A3-64 before clearing A3-26 for
“As the controllers had witnessed previous low overshoots, it
was only three or four seconds before impact that they realised
that A3-64 was continuing with the landing. At this point a
controller called ‘overshoot’ into the microphone while another
was attempting to select all frequencies.”
By this stage the accident was inevitable. While the
delay in clearance of A3-26 was a link in the causal chain, under
the circumstances no criticism of the controllers was intended or
The primary cause of the accident was that the pilot of A3-64
landed without clearance, but that landing was the effect of
numerous causal factors that coalesced into a series of events,
any of which by themselves would have been insignificant - but in
this instance came together at one place and at one time for
tragic consequences. This complex chain of events could have
been broken at many points by the removal of just one of those
Deputy Director Safety Communications Comments:
The use of non-standard radio calls by both
aircrew and ATC continue to be contributory in some Defence
aviation safety occurrences (PC9 near CFIT at Albury, April
2013; separation break-down between a foreign military aircraft
and a civilian light aircraft, March 2014) with luck often
playing a large part in averting disaster. If nonstandard
radio calls are detected, it behoves the receiver to question
and clarify the call to ensure that there is no miscommunication
and both parties understand what is meant or expected.
This accident as usual had numerous
contributing factors and failed or absent defences that
culminated in tragedy when the pilot mistakenly landed without
clearance. Could the accident causation chain have been
broken had the other aircraft back-tracked and lined-up at the
threshold rather than the usual practice of simply taxiing out
of the ORP and lining up, or if the upper surface of the Mirage
been fitted with an anti-collision light, or the pilot on
approach realised and questioned the non-standard radio call?
Physiological and psychological factors
were also contributory. Such factors can compromise the
safety of a flight by increasing susceptibility to errors and
degrading decision making and flying abilities. Pilots are
encouraged to use the IMSAFE checklist which is designed to help
pilots check whether any of these factors individually, or in
combination, affect their physical and mental state before each
each flight, ask yourself the following questions:
Illness – Am I sick today? Am I
coming down with a cold or other ailment?
Medication – Am I taking any
medications that would impair my ability to act as Pilot in
Stress – Am I under a lot of
stress right now (work, family, or other pressures)?
Alcohol – Have eight hours, or
more, elapsed since I last consumed alcohol?
Fatigue – Have I had enough
rest or am I feeling sleepy?
Eating – Have I had enough to
eat or am I feeling hungry or thirsty?