The Airbus A320 (A320) departed Sydney for Coolangatta carrying
sufficient fuel for the planned flight. In addition to the flight
fuel, there was provision for a 10 per cent variable reserve, 60
minutes fixed reserve, 30 minutes holding fuel, plus 200 kg for
contingencies. The Coolangatta terminal area forecast (TAF)
indicated intermittent (INTER) periods of visibility reducing to
3,000 m in heavy showers. The term INTER is used to indicate a
change in prevailing conditions expected to occur frequently for
periods of less than 30 minutes duration, the conditions
fluctuating almost constantly, between the times specified in the
forecast. The Brisbane TAF was similar, with no indication of
thunderstorms at either location.
Near Williamtown, en route to Coolangatta, the crew received an
"Airport Warning" for Brisbane. An Airport Warning is issued by the
Bureau of Meteorology (BoM) to advise airport users of approaching
severe weather conditions; it is not a forecast intended for
flight-planning purposes by flight crews. The warning indicated
that a line of thunderstorms was approaching from the west towards
Brisbane, and the crew noted that the Brisbane weather was expected
to deteriorate coincident with their arrival at Coolangatta.
However, the TAF was not updated until an hour after the BoM became
aware of approaching thunderstorms, and the amended TAF was never
passed to the crew.
The crew calculated that should a missed approach become
necessary at Coolangatta a diversion to Tamworth could be carried
out. Tamworth is listed as an "adequate airport for twin engine
operations" in the operator's A320 operating manual This listing is
relevant to extended range twin-engine operations. Notes appended
to the listing indicate that the list is a guide, and that the
suitability of the airport should be checked prior to its use. The
fuel required to divert was based on a fixed reserve of 30
minutes.
The crew contacted Coolangatta Approach then Coolangatta Tower
prior to commencing a descent, and were advised that the weather
conditions would be suitable for an approach and landing, but that
thunderstorms were approaching from the west. A decision was then
made by the pilot in command to continue to Coolangatta, but divert
to Tamworth if necessary. Constant updates on the weather at
Coolangatta were passed to the crew during the descent, and
aircraft radar returns indicated a clear approach path with storms
cells still to the west of Coolangatta. Advice was received by the
crew that Brisbane weather was deteriorating rapidly at this time,
with rain and lightning close to the airport.
A runway 32 VOR/DME approach was commenced to Coolangatta and
the crew became visual at approximately 1,500 ft. The approach
proceeded normally, with the full length of the runway being
visible in light to moderate rain. The co-pilot was the handling
pilot, and the pilot in command considered the weather conditions
exceeded company requirements for a co-pilot approach and landing.
However, at about 800 ft, the co-pilot unexpectedly commenced a
missed approach, commenting that he did not like the conditions.
Due to the rapidly deteriorating weather the pilot in command
decided there was no option but to carry out the diversion to
Tamworth.
The crew was subsequently advised by company central operations
to divert to Williamtown rather than Tamworth as the company did
not have a standing pavement concession for the use of Tamworth,
and the airport was not included in the company's air operator
certificate. As the aircraft would not arrive at Williamtown with
the required fuel reserves intact, the crew declared a fuel
emergency to air traffic control. The aircraft arrived at
Williamtown with fuel equivalent to a fixed reserve of 27
minutes.