Christchurch

The following findings were identified:
Findings are listed in order of development and not in order of priority.
- The crew was appropriately licensed and fit to conduct the flight.
- The captain was an experienced company line-training captain, familiar with the aircraft and route.
- The co-pilot while new to the Convair 580 was, nevertheless, an experienced pilot and had flown the route earlier in the week.
- The aircraft had a valid Certificate of Airworthiness and was recorded as being serviceable for the flight.
- The estimated aircraft weight and balance were within limits at the time of the accident.
- With a serviceable weather radar the weather was suitable for the flight to proceed.
- The captain was the flying pilot for the flight from Christchurch to Palmerston North.
- The flight proceeded normally until the aircraft levelled after passing Paraparaumu NDB.
- Why the aircraft was levelled at about 14 400 ft was not determined, but could have been because of increasing or expected turbulence.
- The weather conditions at around the time of the accident were extreme.
- The aircraft descended through an area of forecast severe icing, which was probably beyond the capabilities of the aircraft anti-icing system to prevent ice build-up on the wings and tailplane.
- The crew was probably aware of the presence of icing but might not have been aware of the likely speed and the extent of ice accretion.
- The rate of ice accretion might have left insufficient time for the crew to react and prevent the aircraft stalling.
- The transponder transmissions were impaired probably due to ice build-up on the aerials.
- The aircraft probably stalled because of a rapid build-up of ice, pitching the aircraft nose down and probably disorientating the crew. This could have resulted from a tailplane stall.
- Although the aircraft controls were probably still functional in the descent, a very steep nose down attitude, high speed and a potentially stalled tailplane, made recovery very unlikely.
- Under a combination of high airspeed and G loading, the aircraft started to break-up in midair, probably at about 7000 ft.
- Although there was no evidence to support the possibility of a mechanical failure or other catastrophic event contributing to the accident, given the level of destruction to ZK-KFU and that some sections of the aircraft were not recovered, these possibilities cannot be fully ruled out.
- The crew of AF 642 not being advised of the presence of a new SIGMET concerning severe icing should not have affected the pilotsí general awareness of the conditions being encountered.
- Had the crew been aware of the new SIGMET it might have caused them to be more alert to icing.
- Pilots awareness of the presence of potentially hazardous conditions would be increased if other pilots commonly sent AIREPs when such conditions were encountered.
- Operatorsí manuals, especially for IFR operators, might contain inadequate and misleading information for flight in adverse weather conditions.
- The search for the aircraft and pilots was competently handled in adverse conditions.
- The regular mandatory checks of the CVR failed to show that it was not recording on all channels.
- The lack of any intra cockpit voice recordings hampered and prolonged the investigation.
- The DFDR data and available CVR recordings provided limited but valuable information for the investigation.
- Had more modern and capable recorders been installed on ZK-KFU, significantly more factual information would have be available for the investigation, thus enhancing the investigation and increasing the likelihood of finding a confirmed accident cause, rather than a probable one.
- Had suitable ULB tracking equipment been available, the finding of the wreckage and recovery of the recorders would have been completed more promptly.
- The lack of tracking equipment could have resulted in the recorders not being found, and possibly even the wreckage not being found had it been in deeper water.

Findings:
- The pilot was appropriately licensed and rated for the flight.
- The pilotís previously unknown heart disease probably would not have made him unfit to hold his class 1 medical certificate.
- The pilotís ability to control the aircraft was probably not affected by the onset of any incapacitation associated with his heart condition.
- Although the pilot was experienced on the PA 31 type on VFR operations, his experience of IFR operations was limited.
- The pilot had completed a recent IFR competency assessment, which met regulatory requirements for recent instrument flight time.
- The aircraft had a valid Certificate of Airworthiness, and the scheduled maintenance which had been recorded met its airworthiness requirements.
- The return of the cabin heater to service by the operator, after the maintenance engineer had disabled it pending a required test, was not appropriate but was not a factor in the accident.
- The cabin heater was a practical necessity for IFR operations in winter, and the required test should have been given priority to enable its safe use.
- The 3 unserviceable avionics instruments in the aircraft did not comply with Rule part 135, and indicated a less than optimum status of avionics maintenance. However there was sufficient
serviceable equipment for the IFR flight.
- The use of cellphones and computers permitted by the pilot on the flight had the potential to cause electronic interference to the aircraftís avionics, and was unsafe.
- The pilotís own cellphone was operating during the last 3 minutes of the flight, and could have interfered with his glide slope indication on the ILS approach.
- The aircraftís continued descent below the minimum altitude could not have resulted from electronic interference of any kind.
- The pilotís altimeter was correctly set and displayed correct altitude information throughout the approach.
- There was no aircraft defect to cause its continued descent to the ground.
- The aircraftís descent which began before reaching the glide slope, and continued below the glide slope, resulted either from a faulty glide slope indication or from the pilot flying a localiser approach instead of an ILS approach.
- When the aircraft descended below the minimum altitude for either approach it was too far away for the pilot to be able to see the runway and approach lights ahead in the reduced visibility at the time.
- The pilot allowed the aircraft to continue descending when he should have either commenced a missed approach or stopped the aircraftís descent.
- The pilotís actions or technique in flying a high-speed unstabilised instrument approach; reverting to hand-flying the aircraft at a late stage; not using the autopilot to fly a coupled approach and, if intentional, his cellphone call, would have caused him a high workload and possibly overload and distraction.
- The pilotís failure to stop the descent probably arose from distraction or overload, which led to his not monitoring the altimeter as the aircraft approached minimum altitude.
- The possibility that the pilot suffered some late incapacity which reduced his ability to fly the aircraft is unlikely, but cannot be ruled out.
- If TAWS equipment had been installed in this aircraft, it would have given warning in time for the pilot to avert the collision with terrain.
- While some miscommunication of geographical coordinates caused an erroneous expansion of the search area, the search for the aircraft was probably completed as expeditiously as possible in difficult circumstances.

The failure of the left main undercarriage to fully extend was caused by the seizure of the piston rod within the undercarriage jack assembly. The piston rod and the spring housing through which it passed had become scored, eventually resulting in the seizure. The piston rod had been installed, new, in the jack assembly some seven months earlier and had completed 787 landings. Further investigation found that the synthetic wiper ring had been installed incorrectly and would allow foreign material to find its way into the spring housing when the undercarriage was retracted. Additionally, hydraulic components on the undercarriage may have become contaminated during cleaning in an inadequately filtered cleaning booth, which was also used for general cleaning involving the use of abrasive pads.

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 following findings were reported:
- Icing conditions,
- The aircraft was not equipped with deicing systems,
- The pilot was tired due to a duty period more than 18 hours,
- The pilot loaded and unloaded more than 10 tons of cargo during the day,
- The pilot was soaked by rain while doing so because no foul weather gear was provided,
- The pilot did not have sufficient rest time,
- The pilot did not have a proper brake time and meal,
- The pilot was not properly trained concerning indoctrination course and suffered hypoxia in flight.

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.

Due to lack of evidences, the exact cause of the accident could not be determined. However, the following causes have not been ruled out: a loss of control after the pilot suffered a spatial disorientation while trying to deal with an emergency situation in limited visibility (clouds), a loss of control because of airframe ice build-up, a structural failure with a severe fire in the engine bay, an explosion in hazardous cargo, a failure of the flying control system or a possible criminal mischief.

Due to lack of evidence, the cause of the accident could not be determined.