Auckland

Loss of height and hard landing due to windshear on short final.

Findings are listed in order of development and not in order of priority.
- The engine propeller assembly separated from the right engine of ZK-LOU in flight and struck the fuselage when the crankshaft failed at the flange that connected it to the propeller hub.
- High-cycle fatigue cracking on the flange that had developed during normal operations from undetected corrosion had reached a critical stage and allowed the flange to fail in overload.
- The crankshaft had inadvertently passed its overhaul service life by around 11% when the failure occurred, but the company had not realized this because of an anomaly in the recorded overseas service hours prior to importation of the engine to New Zealand. Ordinarily, the crankshaft would have been retired before a failure was likely.
- The crankshaft was an older design that has since been progressively superseded by those with flanges less prone to cracking.
- There was no requirement for a specific periodic crack check of the older-design crankshaft flanges, but this has been addressed by the CAA issuing a Continuing Airworthiness Notice on the issue.
- The CAA audit of the company had examined whether its engine overhaul periods were correct, but the audit could not have been expected to discover the anomaly in the overseas-recorded engine hours.
- This failure highlighted the need by potential purchasers of overseas components to follow the guidelines outlined in CAA Advisory Circular 00-1 to scrutinize overseas component records to ensure that the reported in-service hours are accurate.

Findings are listed in order of development and not in order of priority.
- The flight crew was appropriately licensed and rated for the aircraft, and qualified for the flight.
- The captain was experienced on the type and the operation, and approved as a line training captain, while the FO was recently trained and not very experienced on the type.
- The aircraft had a valid Certificate of Airworthiness and records indicated that it had been maintained in accordance with its airworthiness requirements. There were no relevant deferred
maintenance items prior to dispatch of the accident flight.
- Although the aircraft had been refuelled in one tank only, it probably took off with the fuel balanced within limits.
- Some fuel imbalance led the captain to decide to carry out further fuel balancing while the aircraft was in cruising flight.
- The captain’s instructions to the FO while carrying out fuel balancing resulted in the aircraft being flown at a large sideslip angle by the use of the rudder trim control while the autopilot was engaged.
- The FO’s reluctance to challenge the captain’s instruction may have been due to his inexperience and underdeveloped CRM skills.
- The autopilot 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 in-flight fire which occurred was a result of the break-up, and not a precursor to it.
- The applied rudder trim probably contributed to the crew’s inability to recover control of the aircraft.
- The crew’s other control inputs to recover from the spiral dive were not optimal, and contributed to the structural failure of the aircraft.
- The flying conditions of a dark night with cloud cover below probably hindered the crew’s early perception of the developing upset.
- The AFM limitation on use of the autopilot above 20 000 ft should have led to the crew disconnecting it when climbing the aircraft above that altitude.
- The crew’s non-observance of this autopilot limitation probably did not affect its performance, or its automatic disengagement.
- If the aircraft had been manually flown during the fuel-balancing manoeuvre, the upset would probably have not occurred.
- The operator should detail the in-flight fuel balancing procedure as a written SOP for its Metro aircraft operation.
- The AFM for the SA 226/227 family of aircraft should include a limitation and warning that the autopilot must be disconnected while in-flight fuel balancing is done, and should include a procedure for in-flight fuel balancing.

The following findings were identified:
- The pilot was suitably qualified and authorised to conduct the flight.
- The aircraft was airworthy and its records indicated it had been maintained correctly.
- The aircraft encountered weather conditions conducive to the formation of engine intake icing.
- The engine air intakes probably became blocked by sleet, ice or hail, which caused both engines to lose power.
- The pilot probably developed a mindset that dismissed engine intake icing as a cause of the double engine power loss and omitted to apply the necessary corrective action.
- Had the pilot selected each engine’s alternate engine intake air on, engine power should have been restored.
- The Partenavia P68B flight manual warning concerning the use of alternate engine intake air should be amended to require the in-flight use of alternate air at ambient temperatures above freezing, in a high-humidity environment.

The captain not ensuring the aircraft intercepted and maintained the approach profile during the conduct of the non-precision instrument approach, the captain's perseverance with his decision to get the undercarriage lowered without discontinuing the instrument approach, the captain's distraction from the primary task of flying the aircraft safely during the first officer's endeavours to correct an undercarriage malfunction, the first officer not executing a Quick Reference Handbook procedure in the correct sequence, and the shortness of the ground proximity warning system warning.

The probable cause of this accident was the training captain’s failure to monitor the aircraft’s climb flightpath during the critical stage of the climb after take-off.

The probable cause of this accident was the decision of the captain to continue the flight at low level toward an area of poor surface and horizon definition when the crew was not certain of their position and the subsequent inability to detect the rising terrain which intercepted the aircraft’s flight path. The following findings were reported:
- The flight planned route entered in the company’s base computer was varied after the crew’s briefing in that the position for McMurdo on the computer printout used at the briefing was incorrect by over 2 degrees of longitude and was subsequently corrected prior to this flight.
- The system of checking the detailed flight plan entries into the base computer was inadequate in that an error of 2° of longitude persisted in a flight plan for some 14 months,
- Some diagrams and maps issued at the route qualification briefing could have been misleading in that they depicted a track which passed to the true west of Ross Island over a sea level ice shelf, whereas the flight planned track passed to the east over high ground reaching to 12,450 feet AMSL,
- The briefing conducted by Air New Zealand Limited contained omissions and inaccuracies which had not been detected by either earlier participating aircrews or the supervising Airline Inspectors,
- The crew were not aware of the VHF R/T callsigns in use in the area and these are not published in the briefing notes, the NZAIP, or the US Department of Defence documents which were available to the crew. They were however specified in US Navy instruction CNSFA INST 3722.1, a copy of which was held by Operation Deep Freeze Headquarters,
- The question of making a landing near McMurdo on either the ice runway or the skiways at Williams Field and the type of emergencies which might require such a diversion was not discussed at the company’s briefing,
- The Civil Aviation Division Airline Inspectors had formally approved the audio visual stage of the route qualification briefing for the flight and one had witnessed a typical audio visual segment of the briefing for an Antarctic flight, twice, without requiring any amendments or detecting the errors contained in the briefing. They had also confirmed that it was no longer necessary for captains to carry out a supervised flight as required in the Operations Specifications in view of these briefings and the flight simulator detail,
- Civil Aviation Regulation 77 1(a) had not been complied with,
- The operator departed from the stated undertaking to carry two captains on each flight and substituted an additional first officer in lieu of the second captain,
- Of the flight deck crew only one engineer had flown to the Antarctic previously,
- The crew were not monitoring their actual position in relation to the topography adequately even though a continuous readout of the aircraft’s latitude and longitude and distance to run to the next waypoint was continuously available to them from the AINS,
-The crew did not observe the transition level in use in the McMurdo air traffic control area for resetting this aircraft’s altimeters and this procedure was not published in either the briefing notes or the US Department of Defence documents which were made available to the crew. The procedure used was that prescribed in US Federal Aviation Regulation 91.81 which required the QNH to be set basically at FL 180 during descent but this was modified in low pressure areas,
- The captain’s altimeter was not set to the correct QNH until the aircraft reached 3,500 feet,
- The captain initiated a descent to an altitude below both the IMC (16000 feet) and VMC (6000 feet) minima for the area in a cloud free area but in contravention of the operator’s briefing and outside the sector approved for the descent to 6000 feet by the DCA and the Company,
- The co-pilot was devoting a significant proportion of his time in an endeavour to establish VHF contact with the McMurdo ground stations and did not monitor the decisions of the pilot in command adequately in that he did not offer any criticism of the intention to descend below MSA in contravention of company restrictions and basic good airmanship,
- The descent was intentionally continued below the VMC limit specified by CAD and Air New Zealand Limited, of 6000 feet to an indicated 1500 feet,
- The crew were distracted but not preoccupied by their failure to raise the Ice Tower or any local ground station on VHF, the failure of the DME to lock on to the TACAN and the lack of any identification of the aircraft on radar,
- The company deleted an earlier requirement for VMC descents to be monitored by radar and substituted the alternative procedure of contacting the radar controller for co-ordination of the descent,
- The failure of the aircraft’s systems to establish satisfactory VHF contactor to “lock on” to the McMurdo TACAN was probably due to the aircraft’s low altitude in conjunction with significant high ground between the aircraft and the ground equipment,
- The flight engineers endeavoured to monitor the progress of the flight and expressed their dissatisfaction with the descent toward a cloud covered area,
- Although the route selected by Air New Zealand for the approach to McMurdo crossed almost directly over a 12450 ft active volcano just 20 miles from destination in preference to the normal approach path of military aircraft which was across the sea level ice shelf the Air New Zealand route was safe provided the crew observed the minimum altitudes stipulated for the flight and no extraordinary activity occurred in the volcano,
- Despite the shortcomings of some aspects of the route qualification briefing, this flight and Antarctic flights in general were not unacceptably hazardous, if they had been conducted strictly in accordance with the route qualification briefing as presented,
- The CAD procedure of reapproving Antarctic flights each season on the condition that they complied with the constraints of the previous season’s flights led to some items being discontinued without formal notification or agreement, e.g. the carriage of 2 captains on each flight, and the requirement for a briefing by ODF Headquarters,
- The on board navigation and flight guidance system operated normally during the latter stages of the flight,
- The aircraft’s GPWS operated in accordance with its design specifications,
- CAD had not implemented effectively the section of the ICAO standard detailed in Annex 6 of the convention which requires appropriate life-sustaining equipment to be carried on flights across land areas which have been designated by the State concerned as areas in which search and rescue would be especially difficult. Although the Commander of the USN Antarctic Support Force stated that “limited SAR capability existed over land and very little over water”, this may not constitute “designation of the area” as being especially difficult for search and rescue activities by the State concerned,
- Although some notes on Antarctic survival were given to the Chief Purser immediately before this flight no additional life-sustaining equipment was carried or training given to the crew members to facilitate survival following an emergency landing on the ice or in the polar waters of Antarctica,
- Neither the passengers nor the crew were expecting the collision and all received fatal injuries on impact with the ice,
- The search and rescue organisation was mobilised and co-ordinated in a competent manner despite the difficult environment and the aircraft was located as soon as practicable, (11 hours) after the collision occurred,
- The aircraft was not fitted with a self activated ELT but such equipment is not at present required,
- The aircraft’s CVR and DFDR operated as intended and provided an excellent record for the investigators of this accident. The CVR system however could be significantly improved as discussed in recommendation 8.
- The aircraft’s radar would have depicted the mountainous terrain ahead.

The accident was probably caused by the crew being misled, by a visual illusion in conditions of reduced visibility, into believing they were at a safe height and consequently failing to monitor the flight instruments sufficiently to confirm their aircraft maintained a safe approach path. The accident was the consequence of a controlled flight into terrain.

The pilot was unable to cope with an in-flight emergency initiated by a power plant malfunction and compounded by poor weather conditions, as a consequence of which the aircraft stalled and the pilot lost control at too low an altitude to effect recovery. Autopsy of the pilot revealed acute interstitial myocarditis conducive toward destruction of the cardiac muscle fibers. It is a silent disease prone to cause irregularities in cardiac rhythm, fainting, and occasionally sudden death. The possibility that the pilot had become physically incapacitated to some degree could not be entirely discounted.