Air New Zealand Flight 901 and Polar Whiteout

Abstract

On 28 November 1979 on a sightseeing flight to Antarctica, the Air New Zealand Flight 901 crashed on the slopes of Mount Erebus. All 237 passengers and 20 crewmembers perished on the impact. Two investigations that followed both agreed that due to the Polar Whiteout the crewmembers of Flight 901 had not seen the mountain. This article offers a discussion on whiteouts in general and in regards to the accident. It explores other phenomena that could have led to the tragedy, namely spatial disorientation illusions.

1. Introduction

On the early afternoon on 28 November 1979, sightseeing Air New Zealand Flight 901 (TE-901) was approaching Ross Island, Antarctica. They were not going to land there. Instead, they planned to fly under a cloud base so that passengers could enjoy the wonders of the forbidden landscape below from the comfort of the plane. A low overcast was hanging over Ross Island. However, the Mac Centre advised TE-901 that below 2000 feet (around 600 m) the visibility is 40 miles (more than 60 km). Seventeen minutes before the crash, TE-901 captain Jim Collins requested permission to go below the cloud base in visual meteorological conditions (VMC), and the Mac Centre approved his request. E verybody thought that TE-901 was flying over flat sea ice of the McMurdo Sound. Nobody knew that actually TE-901 was approaching McMurdo station, flying over Lewis Bay, and that the plane was on a collision course with the active volcano Mount Erebus, the God of Darkness in Greek mythology .

The cockpit voice recorder (CVR) demonstrated that the TE-901 had descended from 17,000 feet (about 5,000 meters) to 1,500 feet (457 meters), but no one had ever seen a 12,444 feet (3794 meters) mountain directly in front of the plane. The investigators, the Chief Inspector of Air Accidents R. Chippindale (1979) and the Justice of the Royal Commission of Inquiry, Peter Mahon (1981), both attributed this invisibility to Polar Whiteout phenomena. However, Chippindale and Mahon understood the visibility-related consequences of Polar Whiteouts somewhat differently. Chippindale concluded that the accident was caused by descent in conditions of poor definition of the surface and horizon (as it usually is the case in the Polar Whiteouts conditions). Mahon (1981) argued that the Polar Whiteout conditions had deceived the pilots into believing that “the rising white terrain ahead was in fact quite flat and that it extended on for many miles” . Mahon partly based his conclusion on the theory introduced by a pilot for Air New Zealand’s Gordon Vette. Vette alleged that TE-901 encountered so-called “sector whiteout” (a Polar Whiteout that affects only one sector of terrain). Since then virtually every author writing about the tragedy (including a Weather Channel documentary “Sudden Impact” (Fraser, 2015)) adopted this “sector whiteout” theory.

This article offers scientific explanations and eyewitnesses’ descriptions of Polar Whiteouts. It discusses Chippindale (1979) and Mahon (1981) reports. It provides some arguments that speak against the presence of a Polar Whiteout at the scene of the tragedy, and suggests other phenomena that could have caused the TE-901 pilots to be deceived into control flying into terrain.

2. Polar Whiteouts

The term “whiteout” is used to describe the lack of visibility arising in various meteorological conditions, including blizzards, fogs, etc. In this article, we will discuss the true whiteout (the Polar Whiteout) that is alleged to be responsible for the disaster.

The Polar Whiteout is, “a phenomenon of diffuse reflection and scattering by cloud and ground” Fritz (1957). The Polar Whiteouts occur

when clouds are so thick and uniform that light reflected by the snow is about the same intensity as that from the sky. No object casts a shadow, the surface of the snow merges into the sky, and no horizon, ground, or sky features can be recognized (Harker, 1958) .

Writing in Weather Fritz (1957) emphasizes that true Polar Whiteouts are always associated with clear air:

It should be emphasized that Polar Whiteout is independent of any ordinary meteorological obstructions to vision. It occurs in pure , clean air. Thus Stefansson (1945) states that ' under the conditions where a (polar) bear is invisible a hundred yards off, a blue fox might be visible at a mile or more '. The whiteout should not be confused with fog or haze; the air is clear during whiteout, but the combination of complete snow cover and overcast sky removes all chance of shadows or contrasts so that white objects are not discernible against their background, while dark objects can be seen readily.

American military scientists have been very interested in studying whiteout conditions, and have tried to find ways to dispel whiteout-making clouds.

The U.S. Naval Institute (1956) writes:

Some observers believe that the light intensity is even "magnified" or increased during whiteout , stating that the light reflects and re- reflects in all directions independent of the normal laws of reflection, refraction, and polarization, which during white -out seem to be inoperative.

Schlichting et al. (1980) write:

When there is little in the environment except fields of snow and low cloud cover, the light is reflected back and forth until the distribution from all angles is uniform; in fact, physical measurements of the light, in a full 360 degrees around an individual reveal no differences whatsoever.

Some eyewitness accounts help us to understand how it feels to be caught in a Polar Whiteout. In her book “Alone in Antarctica”, Aston (2014) writes:

There is no structure to focus on, no variation in shade or texture, no sense of distance, dimension or scale.

In his book “ The Ice: A Journey to Antarctica” Pyne provides a rather poetic description of Polar Whiteouts:

[...] the whiteout—in metaphoric Russian, the white darkness. Loosely, a whiteout is any condition in which visibility vanishes. But more precisely, a whiteout occurs whenever light becomes so diffused, scattered, and reflected that all shadows disappear and the horizon as an identifiable feature is lost. Clouds at all levels can produce the effect, though high cirrus clouds are perhaps the most notorious because they appear so innocuous. The whiteout is the ultimate intensification of the reductionism that is the essence of The Ice. Light becomes an obscuring rather than an illuminating medium. Everything is brightened and nothing can be seen. All contrasts dissolve in a fog of light—a “milky, trembling nothingness”.

So hazardous is a whiteout that travel becomes impossible, but other properties make it the quintessence of Antarctic atmospherics. Unlike the blizzard, which is more common along the coast, whiteouts occur in the interior and are ominously passive, not active.”

In a true Polar Whiteout a person could see his own boots (if they are not white of course), but no surface he is standing at (Frost, 2011). In his book “Мир вертолета: Helicopter universe” Савинский (2014) quotes a Russian pilot who worked in Antarctica. He described the Polar Whiteouts conditions on the ground and in the sky:

A person in such conditions completely loses the ability to assess the scale of objects and the distance between them. A match stuck into the snow at a distance of only one or two meters from him seems to be a telegraph pole, moreover, it appears it is standing a kilometer from him.

[...]

Soon we reached the area [flying in a helicopter] where the sky and snow merged into a single whole, and in the sky, as sometimes happen during the “whiteout”, several suns shone, and it was impossible to determine which one was real [it appears the pilot was describing solar halos (Zinkova, 2018)] .

Other authors describe t he difficulty of determining the size of an object and distance to it under Polar Whiteout conditions:

Al described seeing an oil drum at some distance near White Island left by the British Commonwealth Antarctic Expedition. On close examination it revealed itself to be a five-inch ration box.

[...]

Someone else told of an article by Sir Raymond Priestley in which his colleagues had seen a driver and a dog team semaphoring at some distance, until the truth emerged. It was a tribe of penguins , waddling away. And Captain Robert Falcon Scott is said to have once thought he saw a dog team that turned out to be a piece of film wiggling in the breeze (Weihaupt et al ., 2012).

Writing in the National Geographic the famous polar explorer Richard E Byrd (1956) recalls how copter pilot Lt John Bacon described flying in the whiteout conditions:

In the air again , the " choppers " plunged into whiteout conditions , the dread of polar flyers, when ground, sky , and horizon all are lost in a milky haze. "I felt like a fly trapped inside a ping-pong ball.”

It is rather rare to experience a scene with totally diffuse illumination. Usually some objects interrupt its milky harmony. The images presented in Figure 1 were all taken in Antarctica, and although none shows either horizon or shadows and there are hardly any differences between the colours of the sky and the ground, none of them depicts a true Polar Whiteout.

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Figure 1. Upper frame: Tourists are exploring an iceberg that was frozen in the sea ice in the Ross Sea, middle frame: Colony of Adélie penguin at Cape Royds; lower frame the memorial Cross at Wind Vane Hill (Cape Evans) with Robert Falcon Scott’s Discovery Hut. Both images are the author’s own work.

The image presented in Figure 2 is not an image of a Polar Whiteout either. This is a picture of a lighthouse surrounded by fog, photographed in San Francisco . However, this image could serve as a good visualisation of the signatures of Polar Whiteouts we discussed above ( except that this white lighthouse would not be visible under Polar Whiteout conditions ), namely the indistinguishable horizon, the same colour of the sky and the ground, and the absence of shadows. In addition, it is impossible to determine how far or how large the structures are. In the absence of any other visual landmarks, it is impossible to say whether these structures are toys located a few meters from the camera, or real buildings located a few kilometres away.

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Figure 2. Point Benito Light House in fog. The author’s own work.

3. Meteorological condition in the area of the disaster

In his report Chippendale (1979) relisted the meteorological conditions in the area of the disaster. General situation was described as follows:

O n 28 November 1979 at 0100 hours (Z) [11 minutes after the accident] the McMurdo area was under the influence of a surface low pressure [...] the surface definition at the time [was reported] as poor and the horizon definition fair. Mountain tops in the area were covered in cloud.

None of the flight crews located in the immediate vicinity of the disaster zone described the conditions as a Polar Whiteout. Eleven minutes after the crash an American Navy plane was located around 80 miles (around 128 km) from McMurdo. They reported:

[...] continuous stratoform layer covering Ross Island with cloud “domes” over Mt Erebus and Mt Terror which concealed the mountains from view. The cloud layer extended to the north of Ross Island. A lenticular “cap cloud” was over Mt Erebus above the main cloud layer.” [...]

The lowest layer was solid overcast with a ragged base. The visibility was good below the cloud base but the surface definition was poor (Chippendale ,1979) .

One hour eleven minutes after the crash a helicopter

landed on the beach 10 km from the accident site and the conditions at that time were overcast with light snow but the sun could be “made out” through the cloud occasionally. The surface definition at the time was very poor to nil. [...] They were not able to distinguish that the slopes to the south [the slopes of Erebus] were elevated or separately identify cloud and snow. No bare rock was visible on the slopes but the rocky coastline below the ice cliffs was visible ( Chippindale ,1979) .

A United States Air Force was following approximately 45 minutes after TE-901. The captain of this aircraft described the clouds as “ordinary cumulus or stratocumulus ” with a good visibility below the base. (Chippendale ,1979) .

Opinions vary widely on what kind of clouds give rise to Polar Whiteouts. Fritz (1957) appears to agree with Hedine that Polar Whiteouts occur with cirrostratus and/or altostratus clouds. Other authors state that low-level stratus clouds could make whiteouts as well. Most authors agree that Polar Whiteouts can occur under any level of stratus overcast. Cumulus and/or stratocumulus as described by an American pilot do not look promising for the formation of a Polar Whiteout. Furthermore, the helicopter’s pilot could not see bare, black rocks on the slopes of Erebus, which probably means they were behind meteorological clouds. At the same time, lenticular clouds (Figure 3) are common in Antarctica, especially around Erebus and they cast deep shadows https://antarcticfudgesicles.files.wordpress.com/2010/11/dsc_1054.jpg. The presence of lenticular cloud might have prevented a Polar Whiteout from forming.

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Figure 3. Lenticular clouds in Antarctica. The author’s own work.

4. CVR

In this section, we will discuss visibility-related statements made by the crewmembers in the cockpit in the last minutes of the flight.

All times below are in UTC.

The plane crashed at 0049:50.

0047:06 captain: “Down to two thousand feet.”

At about the same time, or later, a passenger took a picture http://photobucket.com/gallery/user/turricaned/media/cGF0aDovaWVfcGFzc2VuZ2VyX3NiX2Rlc2MucG5n/?ref= Chippindale (1979) described the weather associated with the image:

Over Northern Victoria Land the weather was clear with an almost complete absence of cloud at any altitude. The aircraft flew over continuous cloud layers from about Franklin Island to just north of Beaufort Island where the aircraft was able to descend through an obvious break in the cloud cover. Several photographs show a clearly defined cloud base beyond and above the Lewis Bay coastline of something less than 2000 feet.

0047:43 Captain: “We might have to pop down to fifteen hundred here I think”. Second pilot: “Yes, OK. Probably see further in anyway”.

0047:49 Second pilot: “It’s not too bad”.

0048:46 Captain: “Actually those conditions don’t look very good at all – do they?” Somebody: “No, they don’t.”

0049:08 Tour guide: “That looks like the edge of Ross Island there”.

0049:30 Captain: “We’re twenty six miles north we’ll have to climb out of this”.

0049:33 Second pilot: “It’s clear on the right and (well) ahead”. Captain “is it?” Second pilot: “yes”.

0049:35 Tour guide: “You can see (Ross Island) Right Fine!”

0049:38 Second pilot: “Yes you’re clear to turn right there’s no high”. Captain: “No, negative.” Second pilot: “No high ground if you do a one eighty”.

In his report, Chippindale (1979) described the last seconds of the flight before the impact:

After the captain’s decision to climb the aircraft out of the area he and the co-pilot were discussing the most suitable climb out path when the ground proximity warning system sounded instructing the crew to “Pull up”. The crew responded to the alarm without undue hesitation, the flight engineer calling off the heights of 500 and 400 feet indicated on the radio altimeter and the captain calling for “Go-round power”. The warning 6½ seconds before the impact was, however, too late for the crew’s action to make any significant effect on the aircraft’s level flight path. Their reaction time was established as very similar to or better than that of experienced crews placed in a similar situation in the training environment of the flight simulator. It is likely however that as a result of a whiteout the go-round attempt was procedural in response to the warning rather than a desperate attempt to avoid a readily apparent obstacle.

A pilot for Air New Zealand Arthur Cooper listened to the original record and he stated that he has heard no alarm in any voice up to the end (Cleal, 2009).

The weather conditions in Antarctica can turn from a clear horizon definition to a no horizon definition in a matter of seconds. In 2015, an Australian helicopter crashed in the ice shelf, when suddenly the horizon definition was lost and surface definition was reduced. However, the helicopter crashed after the pilot sounded an alarm, and tried to turn back (Commonwealth of Australia, 2015). The absence of alarm in the TE-901 situation indicates that the crew did not experience the loss of visible horizon at any time.

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