Tuesday, June 23, 2009

Into the Storm - the Flight of Tango Victor Charlie

At quarter past seven in the evening of 30th November 1961, the scheduled Australian National Airways (ANA) flight Sydney to Canberra began running up its engines on the east-west runway at Sydney Airport.

This was a Vickers Viscount Series 700 aircraft, with the call-sign VH-TVC or Tango Victor Charlie, and at the controls was Captain Stan Lindsay, assisted by First Officer Ben Costello, and accompanied by air hostesses Elizabeth Hardy and Aileen Keldie.












Above: A Viscount with identical ANA livery to

VH-TVC at Mascot Airport in 1965.
Image courtesy of AussieAirliners
http://www.aussieairliners.org
(click image to enlarge)

Also aboard were 11 other passengers, all but one Canberra residents returning home after a stay in Sydney. As the aircraft rolled into position, lightning flashed to the west and south, and almost immediately after, a huge crack of thunder shook the airport, indicating the nearby presence of a thunderstorm cell.

At 7.17 pm, Lindsay released the brakes, applied full power to the four Rolls-Royce Dart engines, and the big airliner began gathering pace down the runway. Liftoff was on schedule and Tango Victor Charlie climbed quickly and soon vanished into a low overcast cloudbase at around the 250 metre level.

The events of the next 5 minutes will never be precisely known, but the outcome was a watershed event, which changed the course of Australian domestic aviation, and still leaves a footprint on aircraft operating regulations today, mainly in the area of aviation radar.

Radar was originally designed to detect approaching aircraft during the Battle of Britain in the early 1940’s, but it was soon noticed that showers and thunderstorms could also be detected on a radar display. Initially this was seen as a nuisance, with weather “echoes” sometimes masking aircraft movement and making detection and monitoring of aircraft traffic more difficult.
But then it became obvious that radar could also be used as a short-term weather forecasting aid, and it was to eventually become standard equipment in meteorological offices around the world.

Back in 1961, Sydney Airport was equipped with an Air Traffic Control (ATC) radar which was designed and used almost exclusively for directing incoming and outgoing aircraft movements.
Although this radar could also “see” weather, it was not used for this purpose, and the meteorological team at the airport had no direct access to the radar display. In those days, the meteorological team at any one time consisted of three forecasters from the Bureau of Meteorology, two to prepare aviation forecasts for domestic flights and one for International.

Before departure, the airline captain would receive a briefing and written weather forecast from the “Met Office” and then submit a flight plan to the Senior Operations Officer (SOO) for approval. This flight plan was then passed on to the Air Traffic Control Tower so that a firm knowledge of all outbound operations was always available.

The 30th November 1961 was a day of particularly unsettled weather. A low pressure trough was located over central NSW during the morning, and this moved steadily east during the day, triggering a large area of thunderstorm activity across eastern parts of the state.

Late in the afternoon, some of this activity reached Sydney, with numerous official and unofficial observations reporting the approach of thunderstorms from the west, from across the Blue Mountains.

An interesting report was received from a pilot at 6.40 pm from Sylvania, who witnessed “ a thunderstorm overhead, base 1200-1500 feet. There was a half mile diameter circular opening in the base. The cloud forming the base of the thunderstorm was moving towards this opening from all directions at an estimated 50 knots. Above the opening was an inverted funnel which extended a considerable distance vertically”.

Numerous other reports were received from aircraft during the afternoon, with one of the most telling from Tango Victor Charlie itself. Earlier in the day, the aircraft had flow from Canberra to Sydney, and then during the afternoon, back again, and on the approach to Sydney, at around 5.40 pm, reported “Severe continuous turbulence of a jolting nature in which the air speed indicator was fluctuating up to 15 knots either way”

Captain Linsday himself would have been aware of at least some of these reports, and certainly the nature of the turbulence encountered by Tango Victor Charlie would have been relayed back to him before his flight began. A warning of widespread thunderstorm activity across eastern NSW had also been distributed by the Met Office to the Department of Civil Aviation (DCA),and this was then widely promulgated throughout the airline companies, including Australian National Airways. Captain Lindsay’s formal pre-flight weather briefing at the Met Office also indicated the possibility of thunderstorms and heavy turbulence en-route.

All in all this looked like a stand-out dangerous situation, but in fact this sort of weather was not all that unusual for November around southeast Australia, and several similar events could generally be expected at around this time each year. And for a modern aircraft like the Viscount, which was to be flown that night, such situations were thought to be well within the limits of safe operations.

The Vickers Viscount was one of the success stories of post war British aviation. It was a sturdy four- engined turbo-propeller driven passenger aircraft, one of the earliest to be equipped with a fully pressurised interior, and it could cruise comfortably at 8000 metres at about 510 kph.
One of the main features enjoyed by the passengers was the large window area along both sides of the cabin, which allowed for panoramic views during the flight. These windows were nearly 50% larger than those we see today, in the modern jet aircraft.

The Viscount could also carry more than 50 passengers over a range of around 1500 km, and this of course meant it was ideal for the intercity runs from Sydney to Melbourne, and in this case, Sydney to Canberra. This sort of performance is modest compared with that of the modern jet airliner, but back in 1961, the Vickers Viscount was state of the art, and really had only one notable weakness. This was the lack of an on-board radar system, which enables the Captain to precisely locate thunderstorms and to avoid them in flight.

Thunderstorms have long been known as an aviation safety hazard. The technical term for this form of cloud is “cumulonimbus” and in aviation circles they are known as the dreaded CB’s or “ Charlie Bravos” - the monster of the cloud family.

These giant clouds frequently extend above 14 km in height, which is much higher than Mount Everest, and contain about the same energy as a small-scale nuclear weapon. Within the cloud itself there are violent up and down drafts, lightning, heavy rain and often hail also, producing a very aircraft-unfriendly environment.



















A large cumulonimbus formation viewed

from the Space Shuttle (NASA image)
(Click image to enlarge)

Aviation hazards produced by thunderstorms include severe turbulence, airframe icing and possible lightning strikes, and pilots therefore avoid penetrating CB’s whenever possible. During the day, when standing in isolation, these clouds can be seen from many kilometers away and are easily avoided, but at night, when hidden by other surrounding cloud, and with no radar image to act as a guide, they become invisible hazards to all aviation operations.

Soon after Tango Victor Charlie entered the cloud, there were several radio exchanges between the cockpit and the control tower, and the aircraft was instructed to begin a long, climbing, left turn out over Bondi, before returning in the opposite direction and passing back across Botany Bay at about 2500 metres, before tracking out towards Canberra. This manoeuvre was requested because of other in-bound aircraft approaching the area, and was designed to provide a safe separation distance between all the flights. But it didn’t take into account the massive thunderstorm that was still boiling over Botany Bay......

Abruptly, soon after 7.22pm, all transmissions from the aircraft ceased, and DCA then declared a Search and Rescue Operation to be in operation. With all the lightning around it was still believed that the most likely problem was a radio malfunction, but when the aircraft failed to arrive in Canberra at the expected time, it was apparent that something much more serious had occurred and the Distress Phase of the Search and Rescue Operation was declared. No progress was made that night, but soon after first light next morning some wreckage was found on the south shore of Botany Bay, and then later in the morning, the main fuselage debris was located in about 8 metres of water, in the northeast corner of the Bay. It was quickly established that there were no survivors, and the wreckage was then salvaged and taken to a hangar at the airport for analysis.

A Board of Accident Inquiry was established the determine the cause of the disaster, under the Chairmanship of Mr. Justice Spicer, and the final report was made public in August 1962, after a very thorough investigation had been completed. This became known as “The Spicer Report”, and it was to have far reaching implications for aviation in Australia.

After analysis of all the available evidence, Justice Spicer concluded that Tango Victor Charlie was still climbing over Botany Bay when it suddenly encountered extreme turbulence associated with the interior of a thunderstorm cell. This had caused the aircraft to descend rapidly, and in an effort regain control, Captain Stanley had applied correctional action which resulted in severe stress on the airframe.

At around 2000 metres, the starboard wing failed, and a large outer section of this separated from the aircraft. Soon after, the starboard tailplane also broke off, and the aircraft became totally out of control. With all engines still under power, the aircraft entered into a tumbling dive and struck the water at high speed, killing all aboard instantaneously.

Two eyewitness accounts of what could have been the actual crash were also included in the report, although they originated from different locations and also varied considerably in their descriptions.

At Penshurst, at about 7.15 pm, a witness observed “a violent electrical storm centred between Cronulla and Kurnell. At 7.25 pm there was a terrific flash of lightning, followed by two dull red objects falling slowly from the sky.”

And from Chatswood at about 7.22 pm, “ there was fairly heavy electrical storm activity with thunder and lightning at frequent intervals, and heavy rain. A heavy detonation was heard, and out at 156 degrees (that is to the southeast) witness saw a yellow and blue-white glow lasting several seconds and descending fairly fast”.

After sifting through the mountain of information, Justice Spicer concluded that all officers of the Department of Civil Aviation and Bureau of Meteorology had performed their duties correctly and as prescribed by the regulations, but that the regulations themselves needed changing.

In particular, he recommended the development of a specialised radar weather watch at Sydney Airport, with formalised communication between Air Traffic Control and the Met Office during times of severe weather. Air Traffic Control were to then take into account the position of thunderstorms in their deliberations on traffic control, and not just consider aircraft separation alone. Another result was the requirement that all commercial passenger aircraft must carry on-board radar, to allow the Captain to be precisely aware of the position of any thunderstorms near the aircraft track.

These recommendations were accepted, and eventually became part of the structure of Australian commercial aviation. A disaster of this type has never occurred again in Australia, highlighting the foresight of Justice Spicer and his Board with their work.

The safety record of aviation in Australia is excellent, but as with aviation all around the world, this safety has come at a price. Tragically, the flight crew and passengers of Victor Tango Charlie had to pay a big slice of the Australian safety bill on the night of 30 November 1961.

To see one of the last operational Viscounts (taken in 1996) go to

http://www.youtube.com/watch?v=78bhm5gCd8Q

Reference: Australia's Natural Disasters, Richard Whitaker
New Holland Publishers, ISBN 1877069043

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