On 29 October 2011, a Boeing 737-800 (ZK-ZGH) being operated by Air New Zealand on a scheduled domestic passenger flight from Auckland to Christchurch as NZ501 continued its approach at destination significantly below the prescribed approach minima in day IMC without any visual reference before subsequently completing an uneventful touchdown. The flight was part of an annual line/route check for the aircraft Captain.
The event was notified to the Transport Accident Investigation Commission (TAIC) by Air New Zealand two days later and after making preliminary inquiries, it was decided to open an Investigation. ATC radio and radar recordings for the approach were obtained but aircraft flight recorder data was not used.
It was found that the Captain under check and in command was 68 years old, had been employed by Air New Zealand for 47 years and had been a Captain since 1974. He had spent 14 years as a Boeing 747 Captain before joining the Boeing 737 fleet in the same rank when reaching the age of 60 in 2003 due to pilot age restrictions applicable in the USA. He had accumulated 23,875 hours total flying time which included 7,210 hours on type. His medical required him to wear trifocal spectacles when exercising the privileges of his ATPL. The 43 year-old First Officer had joined Air New Zealand in 2007 and had accumulated 8420 total flying hours which included 2,320 hours on type. The 49 year old Check Captain had joined New Zealand in 1995 and had accumulated 17,200 total flying hours which included 9,200 hours on type. The Investigation noted that "all three pilots said that they had had about eight hours’ sleep the preceding night and that fatigue had not been a factor" and all three "were familiar with Christchurch and the ILS/DME approach procedure".
It was established that the operating Captain was PF for the sector on which the event under investigation had occurred, which was the first flight of the day. The Check Captain's pre-flight brief advised that he was there "to observe a normal day's work from the flight deck supernumerary crew seat". He stated that he had not elaborated further because of the Captain's experience. It was noted that "the operator’s guidelines stated that Check Captain's "should not generally contribute to the operation except in emergency/abnormal situations when full assistance should be offered.”"
Shortly before commencing descent, the Christchurch ATIS was checked and the weather report found to correspond to that forecast for the ETA which would be suitable for the intended Cat 1 ILS/DME approach to runway 02. The approach brief was given and included the applicable minima of 200 feet aal (323 feet QNH) and the fact that the approach would be flown with the AP engaged and in accordance with the operator’s standard approach procedure which meant the Captain was flying and would look outside the cockpit when approaching the decision height, whilst the First Officer would keep his head down monitoring the instruments.
The aircraft subsequently checked in with Christchurch TWR and after advising that it was established on the ILS was instructed to continue following an ATR 72 ahead. The controller also advised that the cloud had "descended to the ground now" with surface visibility approximately 800 metres and that a late landing clearance should be expected because they would need to get the ATR in sight off the runway before issuing a landing clearance.
The automated 'one thousand' callout occurred which required the PF to respond with either “stable” or go around, in which case the missed-approach procedure was to be initiated. It was found that on the contrary, the Captain "made no response […] although the Check Captain believed he heard him 'grunt'". The First Officer, who had not previously flown with the Captain but said he was "aware of his reputation for not being overly communicative", stated that "the Captain’s lack of a response was not unexpected and because the aeroplane was stable on the instrument approach, he did not challenge".
The ATR landed but with the 737 at "about one and a half nautical miles from the runway threshold", the controller could not yet see it and advised the 737 crew to expect a late landing clearance. A few seconds later, the controller caught sight of the ATR as it turned off the runway approximately 500 metres from the TWR and issued a landing clearance to the 737.
At 100 feet above DA, the automated call 'plus hundred' was annunciated. This should have been followed by the Captain saying “confirmed” but although he later said that he thought he had responded, he could not remember what he said and neither the First Officer nor the Check Captain heard any response. The First Officer stated that "he was about to prompt the Check Captain for a response when the aeroplane reached the decision altitude and the third automated voice call of 'Minimums' was made". The required response was either 'continue' if the prescribed visual reference had been acquired or 'go around' if it had not, but the Captain did not say anything. He subsequently stated that "as they were approaching decision altitude he was looking down at the instruments" and when he looked up after the 'minimums' callout, he had been "confused [surprised] that he was unable to see the runway or the environs".
The First Officer had repeated the 'mimimums' call and had "then looked across at the Captain to check if he was still actively flying". Since he "appeared okay", he "then looked forward, expecting to see the runway ahead, but all he could see was cloud". He stated that as he was about to prompt the Captain again, the runway approach lights became visible with the aeroplane estimated to be about 100 feet below DA. The Captain disconnected the AP and landed the aeroplane without saying anything. The Check Captain later said that he was also about to challenge the Captain’s intentions and "was trying to locate his microphone ‘press-to-talk’ switch when the runway approach lights became visible".
The controller was unable to see the 737 "until it had taxied clear of the runway (abeam the TWR)"'. After the aeroplane had been taxied to its parking position and shut down, the Check Captain informed the Captain that he had failed the Check Flight and he was stood down. It was noted that the next two aeroplanes to make an approach, four and seven minutes later respectively, had both carried out the missed approach procedure.
The Investigation observed that "when an aeroplane is on an instrument approach to a runway, it is a serious safety issue when the pilot continues with the descent below the [[Minimum Descent Altitude/Height |minimum (decision) height]] without having the required visual references". It was noted that approach procedure decision heights "are calculated with safety margins which allow aircraft to initiate safe missed approaches in the event of runway lights or markings not becoming visible" and "if a decision height is not heeded, safety margins are rapidly eroded and there is a real risk of the aeroplane landing with enough force to damage the landing gear" with the likelihood of far worse consequences if the aircraft were not to be properly aligned with the runway at the time. It was noted that "at a standard rate of descent and a standard approach speed, there were only about another five seconds available for either the First Officer or the Captain to react and arrest the rate of descent to avoid striking the ground before initiating a missed approach, or to avoid a heavy landing".
The Investigation considered various reasons which might explain why the Captain had not initiated the mandatory missed approach that was prescribed. One of the reasons discussed was plan continuation bias which involves "the tendency to favour or accept information that supports a pilot’s expectation and ignore or downgrade information that may be contrary to that expectation". It was noted that the crew had received a number of indications during the approach that the cloudbase was lower than had been forecast before departure and had significantly deteriorated from the ATIS weather obtained prior to descent. The chances of being able to continue to a landing were clearly diminishing and whilst it was considered that the effect of these multiple indications "could have been offset by the knowledge that the ATR aeroplane only two minutes ahead had made a successful landing […] the reported information should have prompted a discussion (about) the possibility of a missed approach".
It was also noted that, taken in the context of the Captain's habitually "minimalistic" approach to communication, the failure of the First Officer to challenge three consecutive failures to give [[[SOPs|SOP]] responses to the three automatic callouts had represented a lost opportunity to break a mindset which the Captain may have developed that he would become visual at decision height. It was considered that the addition of a Check Captain to the usual two-pilot dynamic addressed by CRM had the potential to alter the situation in the flight deck. The potential effect of the fact that the flight was a route check was considered and it was possible that other factors may have been contributors to stress. These could have included "his dislike for having his performance evaluated" and "his past experience involving the same Check Captain, which from the Captain’s perspective was a negative experience". However, it was also obvious that "check flights were not new to the Captain" - "according to the operator’s records he had undergone 47 previous route checks and 94 simulator proficiency checks over his 47 years with the company" - but unexpectedly marginal weather conditions during a route check could still have been a new experience.
It was noted that "a common dilemma for Check Pilots is how far they let a situation develop to enable key lessons to be demonstrated before it becomes unsafe" and that the pre-flight briefing was therefore important to both the pilot under check and their colleague who is not. It was considered that the non-intervention by the First Officer when the Captain failed to follow SOP may have been a consequence of doubt in his mind as to what was expected of him and when. For example, a pre-flight statement by the Check Captain that they will not intervene unless there was a direct threat to safety (such as the violation of minima) would have made it clear that he should not have expected any intervention by the Check Captain when the Captain missed responding to the '1,000' and 'plus 100' and "it would have been clear to him that any [such] intervention needed to come from himself" in accordance with SOP.
In respect of the Captain's dis-inclination to follow some SOPs, the Investigation found that Air New Zealand was aware of his "tendency over a period of at least three years to not always follow standard communication procedures" and noted that "the informal method the Company used to address the issue did not result in any measurable improvement" and had been contrary to the process described as applicable in such circumstances. As a result of the investigated event, it was noted that a performance management plan for the Captain had been developed, "but he retired before it could be put into action".
Finally, it was found that in respect of the Captain's age alone, "there was no evidence to support the possibility that it was a factor affecting his performance during the approach to landing".
Six Findings from the Investigation were formally recorded as follows:
- The Captain did not make the appropriate response to two automated calls prior to the aeroplane reaching the point (decision height) at which the flight crew needed to decide whether to continue and land, or initiate a missed approach, and the First Officer did not challenge the Captain for an appropriate response on either occasion.
- The Captain compromised the safety of the flight by not initiating a missed approach when the aeroplane reached the decision height and the meteorological conditions were not suitable to land.
- The only appropriate decision was for the Captain to commence a missed approach. He did not make that decision probably because he was operating under a level of stress, where anxiety was interfering with his cognitive functioning.
- There was no evidence to suggest that the Captain’s age was a factor affecting his performance on the flight.
- The presence of the Check Captain on the flight deck and its effect on crew dynamics and communications had not been thoroughly discussed during the pre-flight briefing, which had the potential to blur the boundaries of individual involvement in the flight deck operations.
- The Operator had not followed its own procedures for managing the previously identified performance issues with the Captain. This resulted in his continuing with non-conforming practices, virtually unchallenged.
One Safety Recommendation was made as follows:
- that the Director of Civil Aviation should note that the pilot check process can interfere with safe flight operations if not properly managed, and raise this potential safety issue with industry in the most appropriate manner. [015/14]
The Final Report of the Investigation was approved for publication in June 2014 and subsequently published on 26 June 2014.