When All the Holes Lined Up

On November 28, 1979, Air New Zealand Flight TE901, a sightseeing flight over Antarctica, crashed into Mount Erebus, killing all 257 people on board. The Mount Erebus disaster remains one of the worst in New Zealand’s history.

The cause? A chain of errors, which tragically lined up in a way that allowed this catastrophe to occur.

In accident analysis, this concept is often referred to as the “Swiss Cheese Model”—an illustration of how multiple layers of defences can be breached if there are holes in each layer. The disaster unfolded as a result of several such errors, each one aligning to form the perfect storm.

Hole 1: Incorrect Flight Path Coordinates

One of the most critical errors was a change in the flight coordinates that led the aircraft directly toward Mount Erebus.

Air New Zealand had been operating sightseeing flights over Antarctica since 1977. Two weeks prior to the crash, The Captain designated for that flight attended a briefing in which he was shown a copy of the previous flights plan which, as in all previous flights before that,  contravened the official plan, taking the flight safely down over the sea into McMurdo Sound.

On the morning of the disaster, the navigation system for TE901 was loaded with the coordinates from the approved flight plan that were 2 degrees off from the original route. This change was made without the knowledge of the flight crew. The original route would have taken the aircraft safely over McMurdo Sound, but the new coordinates guided the plane directly into the path of Mount Erebus.

None of the previous 13 flights had followed the official route in the approved flight plan which plotted a path almost directly over Mount Erebus to the McMurdo Non Directional Beacon (NDB), which was one of only two navigational aids in the region (the other aid, the TACAN was very near to the NDB). The minimum altitude to clear the mountain would have been 13,000 feet, and the approved flight plan indicated a minimum altitude of 16,000 feet.

It has never been satisfactorily explained why the route, from the start of these flights, was changed to a more ‘sightseer friendly’ route, other than it was a ‘mistake’.

Hole 2: Whiteout Conditions

Antarctica’s unique atmospheric conditions played a key role in this disaster. Mount Erebus is a 12,448-foot active volcano covered in snow, which makes it blend into the white backdrop of Antarctica’s terrain. On that particular day, the crew encountered what is known as “sector whiteout.” This phenomenon occurs when the sky is overcast and the snow-covered ground reflects the same light, making the horizon indistinguishable.

Believing they were flying over McMurdo Sound, the pilots were flying visually under the cloud cover. However, the whiteout obscured the mountain, and they did not realize they were flying directly toward the slope of Mount Erebus.

Hole 3: Lack of Updated Information

The pilots were not informed of the change in coordinates, nor were they aware of the updated flight path that would take them dangerously close to Mount Erebus. Moreover, there were no alerts or warnings from the ground-based systems to indicate a change in terrain as the plane approached the volcano. In essence, they were flying blind, without any updates from Air New Zealand or proper terrain radar to warn them of the imminent danger.

While the pilots relied on their navigation instruments, they were also expecting a visual flight over what they believed to be a flat expanse of McMurdo Sound.

Hole 4: Insufficient Ground Support

At the time of the disaster, the air traffic control team in Antarctica was only able to offer basic advisory services. While the McMurdo Station had radar capability, it was not actively monitoring TE901’s altitude and exact flight path. Additionally, when the aircraft made its descent to 1,500 feet (believing it was flying over safe terrain), no alerts were sent from ground control regarding the hazardous altitude over Mount Erebus.

The lack of active guidance from the ground allowed the plane to descend dangerously close to the slope without corrective intervention.

Hole 5: Crew Decision-Making and Visual Cues

The captain of TE901 was highly experienced, but the decision to descend to 1,500 feet for better sightseeing visibility was based on a false assumption of the terrain beneath them. The pilots had no reason to suspect that their navigation systems were incorrect due to the unknown change in coordinates. As they descended further, the whiteout conditions gave no visual clues of the approaching mountain.

To give perspective to the altitude that the aircraft was cruising at during the final moments, 1,500 feet is the height a jet aircraft is at when approximately 2 minutes away from landing.

By the time they realized they were flying directly toward Mount Erebus, it was too late. The terrain warning system was insufficient to provide the necessary lead time for avoidance, and the crash occurred at approximately 12:49 PM local time on the slope of Mount Erebus at a height of 1,500 feet.

Hole 6: Organizational Failures and Miscommunication

The accident report, conducted by Justice Peter Mahon, famously described Air New Zealand’s handling of the flight plan changes as “an orchestrated litany of lies.” The inquiry uncovered that crucial changes, like the flight path shift, were not properly communicated to the crew. Furthermore, the airline had not adequately briefed the pilots on the unique risks associated with flying in Antarctica, nor had they been informed of potential whiteout conditions that day.

This organizational failure, from lack of proper communication to inadequate risk assessment, sealed the fate of TE901. The airline’s internal breakdowns created the final gap in safety, aligning all the other holes.

Conclusion: The Lessons of the Erebus Disaster

The Mount Erebus disaster teaches a sobering lesson about the cumulative effects of small errors. When all the holes in safety defences align, disaster becomes not just possible, but inevitable. From the changed coordinates and sector whiteout to organizational failures, TE901’s tragedy was a result of multiple layers of oversight failing simultaneously.

The Erebus disaster has led to significant changes in aviation safety, including more rigorous flight path reviews, the development of advanced terrain-warning systems, and improvements in communication between flight crews and ground support.

Footnotes: The guide for the flight was originally meant to be Sir Edmund Hillary who, having other commitments, asked his friend Peter Mulgrew to step in.

Edmund Hillary married Peter Mulgrew’s widow.

The wreckage of the aircraft is still there on the mountain. Due to its position and remoteness, it was decided that it was too dangerous to remove it. It’s visible at times during summer when the snow melts.
 

© Dixie 2024