Stratford

The crew requested engine start at 2128 and Post 23 taxied for runway 23R at about 2132. The flight data recorder (FDR) showed that during the taxi a left turn through about 320° was made in 17 seconds. Post 23 departed at about 2136 with the first officer (FO) the pilot flying (PF). The planned cruise level was flight level (FL) 180 but the cockpit voice recorder (CVR) showed that in order to get above turbulence encountered at that level the crew requested, and were cleared by air traffic control (ATC), to cruise at FL220. The autopilot was engaged for the climb and cruise. There were 2 CVR references to the crew’s use of the de-icing system to remove trace or light icing from the wings. CVR comments also indicated that stars were visible, and that the aircraft’s weather radar was serviceable. At 2159 ATC cleared Post 23 to track from near New Plymouth very high frequency (VHF) omni-directional radio range (VOR) direct to Tory VOR at the northeast end of the Marlborough Sounds, and at 2206 ATC transferred Post 23 to Christchurch Control. The CVR recorded normal crew interaction and aircraft operation, except that climb power remained set for about 15 minutes after reaching cruise level in order to make up some of the delay caused by the late departure. At about 2212:28, after power was reduced to a cruise setting and the cruise checks had been completed, the captain said, “We’ll just open the crossflow again…sit on left ball and trim it accordingly”. The only aircraft component referred to as “crossflow”, and operable by a flight deck switch or control, was the fuel crossflow valve between the left and right wing tanks. The captain repeated the instruction 5 times in a period of 19 seconds, by telling the FO to, “Step on the left pedal, and just trim it to take the pressure off” and “Get the ball out to the right as far as you can …and just trim it”. The FO sought confirmation of the procedure and said, “I was being a bit cautious” to which the captain replied, “Don’t be cautious mate, it’ll do it good”. Nine seconds later the FO asked, “How’s that?”. The Captain replied, “That’s good – should come right – hopefully it’s coming right.” There was no other comment at any time from either pilot about the success or otherwise of the fuel transfer. During this time, the repeated aural alert of automatic horizontal stabiliser movement sounded for a period of 27 seconds, as the stabiliser re-trimmed the aircraft as it slowed from the higher speed reached during cruise at climb power. Forty-seven seconds after opening the crossflow, the captain said, “Doesn’t like that one mate… you’d better grab it.” Within one second there was the aural alert “Bank angle”, followed by a chime tone, probably the selected altitude deviation warning. Both pilots exclaimed surprise. After a further 23 seconds the captain asked the FO to confirm that the autopilot was off, but it was unclear from the CVR whether the captain had taken control of the aircraft at that point. The FO confirmed that the autopilot was off just before the recording ended at 2213:41. The bank angle alert was heard a total of 7 times on the CVR before the end of the recording. During the last 25 seconds of radar data recorded by ATC, Post 23 lost 2000 ft altitude and the track turned left through more than 180°. Radar data from Post 23 ceased at 2213:45 when the aircraft was descending through FL199 about 1700 metres (m) southeast of the accident area. Commencing at 2213:58, the ATC controller called Post 23 three times, without response. He then initiated the uncertainty phase of search and rescue for the flight. The operator had a flight-following system that displayed the same ATC radar data from Airways Corporation of New Zealand (ACNZ). The operator’s dispatcher noticed that the data for Post 23 had ceased and, after discussing this with ACNZ, he advised the operator’s management. There were many witnesses to the accident who reported noticing a very loud and unusual noise. Some, familiar with the sound of aircraft cruising overhead on the New Plymouth – Wellington air route, thought the noise was an aircraft engine but described it as “high-revving” or “roaring”. Witnesses A were located about 3 kilometres (km) south of the southernmost part of the track of Post 23 as recorded by ATC radar, and about 6 km south of the accident site. They described going outside to identify the cause of an intense noise. As they looked northeast and upwards about 45°, they saw an orange-yellow light descending through broken cloud layers at high speed. A “big burst” and 3 or 4 separate fireballs were observed “just above the horizon” about 5 km away. No explosion was heard. The biggest fireball lasted the longest time and was above the others. The night was dark and it had been drizzling. Witness B, almost 7 km to the northeast of the accident site, observed light and dark cloud patterns moving towards the northwest. She thought the moon caused the light variation; however moonrise was almost 3 hours later. This witness also first observed a fireball below the cloud at an elevation of about 6°. She described it as “a big bright circle” followed by 2 smaller fireballs that fell slowly. No explosion was heard. Witness C, who was less than 1000 m from the aircraft’s diving flight path, described seeing the nose section falling after an explosion “like a real big ball of fire”. The wings were then seen falling after a smaller fireball that was followed by a third small fireball. The witness said it was a still night, with no rain at that time, and the fireballs were observed below the lowest cloud. The fireballs illuminated falling wreckage and cargo. Witness D, also less than 1000 m from the accident site, described parts of the aircraft falling, illuminated by the fireball. Witnesses generally agreed that the first and biggest fireball was round and orange, and then shrank away. Descriptions of the smaller fireballs varied, but were usually of a more persistent, streaming flame that fell very steeply or straight down. A large number of emergency service members and onlookers converged on the accident area. Those who got within about 1000 m of the scene reported a strong smell of fuel. The first item of wreckage was located at about 2315. The main wreckage field was on hilly farmland 7 km northeast of Stratford at an elevation of approximately 700 ft.

The pilot had arranged to topdress properties for three clients, one of whom had three separate blocks to be treated. He departed from Stratford Aerodrome at 0653 hours in ZK-LTF for the first airstrip, located some 7 km to the north-east. After an initial reconnaissance flight, he began topdressing at 0722, and finished this block at 1034 hours. Via brief landings at Stratford and another airstrip 11 km to the north, he positioned the aircraft to a strip near Huiroa. The remainder of the day’s work was carried out from this strip. Four blocks were treated from this location: the first was 8 km to the north-west of the strip, the second immediately to the north, the third some 3 km west and the last 4.5 km to the south, adjacent to the Strathmore Saddle. A reconnaissance of the fourth block was flown at 1518, but actual spreading on this property was not commenced until 1755 hours. Two loads of urea were spread on the fourth block between 1755 and 1812 hours, with a 12-minute pause until the final take-off at 1824. During this break, the last of the urea was loaded, the fertiliser bins secured and the loading vehicle parked. It is not known if the aircraft was refuelled at this time. The loader driver boarded the aircraft after completing his duties, the apparent intention being to accompany the pilot back to Stratford on completion of the last drop. On arrival over the property at 1825, the pilot performed one run towards the south, made a left reversal turn, spread another swath on a northerly heading, and pulled up to commence another reversal turn to the left. At some time after this pull-up, the aeroplane struck the ground heavily on a south-westerly heading, killing both occupants on impact. Later in the evening, the pilot’s wife reported the aircraft and its occupants overdue, and a ground search was commenced, initially by friends and associates. The wreckage and the bodies of the crew were found about half an hour after midnight. The accident occurred during evening civil twilight, at approximately 1830 hours NZST, adjacent to the Strathmore Saddle, at an elevation of about 530 feet.