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Last updated: 14 November 2018
Statuts:Enquête Officielle
Date:lundi 2 mai 2005
Type/Sous-type:Silhouette image of generic SW4 model; specific model in this crash may look slightly different
Swearingen SA227-AC Metro III
Compagnie:Airwork, NZ
Immatriculation: ZK-POA
Numéro de série: AC-551B
Année de Fabrication: 1983
Heures de vol:29010
Moteurs: 2 Garrett TPE331-11U-611G
Equipage:victimes: 2 / à bord: 2
Passagers:victimes: 0 / à bord: 0
Total:victimes: 2 / à bord: 2
Dégats de l'appareil: Perte Totale
Conséquences: Written off (damaged beyond repair)
Lieu de l'accident:6 km (3.8 milles) E of Stratford (   Nouvelle-Zélande)
Phase de vol: En vol (ENR)
Aéroport de départ:Auckland International Airport (AKL/NZAA), Nouvelle-Zélande
Aéroport de destination:Blenheim-Woodbourne Airport (BHE/NZWB), Nouvelle-Zélande
Numéro de vol: 23
Metro III ZK-POA was scheduled to depart from Auckland (AKL) at 21:00 on an NZ Post return flight to Blenheim (BHE). The payload comprised 1790 kilograms (kg) of courier packs and parcel mail. Loading of the freight was delayed, being completed at about 21:15. The crew ordered 570 litres (about 1000 pounds or 450 kg) of additional fuel and instructed the refueller to put it all into the left wing tank, rather than put half of the ordered amount into
each tank, as was company practice. Refuelling was completed at 21:30. Two minutes later the flight taxied out to runway 23R. Takeoff was performed at 21:36. The aircraft climbed to an altitude of FL220 with the autopilot engaged for the climb and cruise. At cruise altitude the climb power remained set for about 15 minutes in order to make up some of the delay caused by the late departure. At about 22:12:28, after power was reduced to a cruise setting and the cruise checks had been completed, the captain noted some fuel imbalance and decided to carry out further fuel balancing. He said, "We’ll just open the crossflow again ..sit on left ball and trim it accordingly". The captain repeated the instruction 5 times in a period of 19 seconds, by telling the first officer 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 first officer 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".
These instructions resulted in the aircraft being flown at a large sideslip angle by the use of the rudder trim control while the autopilot was engaged. 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.
The autopilot had probably disengaged automatically because a servo reached its torque limit, allowing the aircraft to roll and dive abruptly as a result of the applied rudder trim. The crew was unable to recover control from the ensuing spiral dive before airspeed and g limits were grossly exceeded, resulting in the structural failure and in-flight break-up of the aircraft. The flying conditions of a dark night with cloud cover below probably made it more difficult to notice the developing upset at an early stage.
The break-up probably started when the aircraft was quite high, perhaps FL199. The wreckage was scattered over a large area of at least two to three sq km of rural farmland.

Probable Cause:

PROBABLE CAUSE: The investigation report did not contain a probable cause paragraph as recommended in ICAO Annex 13.

Accident investigation:
Investigating agency: TAIC New Zealand
Status: Investigation completed
Duration: 1 year and 3 months
Accident number: 05-006
Download report: Final report


Opérations de secours
On 30 May 2005, the operator issued a Notice to Pilots advising that forthwith the SOP was to give the refueller the volume of fuel to be put into each wing tank to achieve a balanced load prior to engine start, in accordance with the Pre-Start checklist, Metro Training Manual and AFM.
On 30 June 2006 the operator amended the Metro checklist to add to the Line-up and Approach checklists the item "crossflow closed".
On 4 July 2006 the operator amended the autopilot Standard Operating Procedures section of the company Metro Training Manual to include two cautions on the use of the fuel crossflow switch.

TAIC issued 1 Safety Recommendation

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photo of Swearingen SA.227AC Metro III ZK-POA
photo of Swearingen SA.227AC Metro III ZK-POA
ZK-POA on close final to Rwy 23 AKL the friday before the accident
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Ce plan montre l'aéroport de départ ainsi que la supposée destination du vol. La ligne fixe reliant les deux aéroports n'est pas le plan de vol exact.
La distance entre Auckland International Airport et Blenheim-Woodbourne Airport est de 506 km (316 miles).
Accident location: Exact; as reported in the official accident report.

Les informations ci-dessus ne représentent pas l'opinion de la 'Flight Safety Foundation' ou de 'Aviation Safety Network' sur les causes de l'accident. Ces informations prélimimaires sont basées sur les faits tel qu'ils sont connus à ce jour.
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