Episode 56: MacRobertson Miller Airlines Flight 1750

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Summary:

When MacRobertson Miller Airlines Flight 1750 took off from Perth, Australia on December 31, 1968, there had been 64 air disasters worldwide during the year. No one knew that the year would end with 65 plane crashes— or that MMA Flight 1750 would be the final addition to the list. In this week's episode of Take to the Sky: the Air Disaster Podcast, Stephanie takes us through the timeline to understand what happened and what surprising information the investigation uncovered. It's a lesser-known story with a powerful legacy!



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When Did MacRobertson Miller Airlines Flight 1750 Crash?

1968 was a pretty quiet year for aviation in Australia. Globally, there had been 64 accidents that had claimed the lives of 1,363 people worldwide. None of those accidents had happened in Australia, and air disasters were certainly the furthest thing from the minds of the 22 passengers and 4 crewmembers who boarded MacRobertson Miller Airlines Flight 1750 on December 31: it was New Year's Eve.

What Was MacRobertson Miller Airlines?

MacRobertson Miller Airlines (MMA) formed in 1927 and became MacRobertson Miller when Australian aviator Horrie Miller partnered with chocolate millionaire Macpherson Robertson; Robertson is credited with bringing chewing gum and cotton candy from the USA to Australia, and his company eventually acquired by Cadbury's. The airline found some early success when it won a government mail contract to provide airmail services, and by the mid-1950s the airline serviced airports in the Northern Territories and Western Australia, and they had expanded into commercial flights as well.

Where was MMA Flight 1750 Going?

Flight 1750 was scheduled to fly from Perth to Port Hedland in Western Australia, and the flight plan on file showed the aircraft would shuttle the passengers and crew on a three-hour journey that would take them from Australia's southwestern corner to its northwestern coast.

Who Were the Pilots of MMA Flight 1750?

In command of the aircraft that day was Captain Brian Beverly Bayly, who was 47 years old. Captain Bayly had a military background; he had served as a World War II bomber pilot before earning his first class airline transport license in 1947, and he joined MacRobertson Miller Airlines in 1954. Captain Bayly was the fourth most senior pilot at MacRobertson Miller; he had 19,129 flight hours of experience as a pilot with a staggering 17,877 of those hours as the pilot in command, so his experience was extensive.

First Officer Michael Nelson joined Captain Bayly in the cockpit that day. He was 31 years old and possessed a second class airline transport license which he earned shortly after his employment at MacRobertson Miller began in 1965. He had a total of 2,660 hours of flying experience in his career with 620 of those hours in command.

Who Were the Flight Attendants on MacRobertson Miller Airlines 1750?

In the passenger cabin, there were three flight attendants onboard; they had the title of hostess. The senior hostess was 24-year-old Georgette Frances Bradshaw, who had been working for the airline for two years and was a training hostess, which meant she was qualified to manage and train fellow hostesses. One of those hostesses, 23-year-old Gail Sweetman, had just finished her first year on the job and had been promoted to the senior hostess role. Gail had been Western Australia's entrant into the 1965 Miss Australia Quest, which was a pageant and charitable event. The other hostess, 23-year-old Kay Aubery, was a trainee. She was traveling on a passenger ticket for his flight as she learned the ins and outs of her new role, and Flight 1750 marked just the fourth flight of her career. Kay was actually scheduled to fly on a different flight that day, but a last-minute schedule change brought her to Flight 1750.

Who Were the Passengers on MacRobertson Miller Airlines Flight 1750?

As for the passengers, like most flights, there were a mix of business and pleasure fliers onboard; while some people were heading to Port Hedland for New Year's Eve and vacation, there were also a number of mining staff on the flight. The year before, in 1967, iron ore deposits were found in the area, so it was quickly becoming a big mining location. Johnny Colombres was traveling in place of his colleague, Gary Silcock; Gary had given Johhny his seat on the plane so he could get home to spend New Year's Eve with his kids. And for one passenger, 67-year-old Keith Dyke, it was a bit of a momentous occasion: it was his very first flight.

What Type of Plane Was Used for MacRobertson Miller Airlines Flight 1750?

The aircraft that day was a Vickers Viscount Type 720. The Vickers Viscount was built for comfort and for international flights; with seating for up to 48 passengers in most configurations, it could reach a cruising speed of 308 miles per hour and was lauded for the improvements it offered to the flying public and the aviation industry. Its operational costs were lower than many similar types of aircraft at the time, and it was much quieter than some of its predecessors. The plane had four Rolls-Royce Dart turboprop engines, which were much quieter than some of the piston engines used on other aircraft; turboprop engines are turbine engines that drive propellers. It also offered a smoother ride for passengers, so just a better experience all around. Passengers liked the Viscount quite a bit; it was comfortable for some of the longer flights, it is was known for having especially large windows, which of course are great for visibility and for allowing light into the cabin. All in all, the Vickers Viscount was a popular plane throughout the traveling public and with airlines.

For Flight 1750, the specific aircraft had a total of 31,746 flight hours since it entered into service in November 1962— about 6 years earlier. Before boarding, Captain Bayly filed his flight plan, which he did at 7:49 AM; he indicated that the flight would take 189 minutes, would fly at a cruise altitude of 17,000 feet, and that he had enough fuel for 295 minutes of flight, which was 33 minutes more than the minimum permissible fuel endurance for the flight. He signed off on the aircraft load statement, indicating that he knew how heavy the aircraft was and that it was both operating within the acceptable take-off weight range, and with that, at 8:29 AM, the flight was ready for departure. The aircraft was started, and they taxied to runway 2.

What Was the Flight Like for MacRobertson Miller Airlines 1750?

The flight took off at 8:36 AM on a day that the official accident report referred to as "fine." There were no meteorological concerns as far as weather along the flight route was concerned. By 8:39, Captain Bayly reported that the flight was climbing at 155 knots, which was slower than the 175 knots indicated in his flight plan. There was some turbulence in the area that slowed them down a bit, and Captain Bayly told air traffic control, "the turbulence is light with patches up toward moderate to about 8,000 feet — we're still getting slight turbulence at ten but there are a couple of nasty patches round about five."

First Officer Nelson reported another diversion from the flight plan to air traffic control; he let them know the flight would be climbing to 19,000 feet instead of 17,000 feet. This would not have been a major issue; the service ceiling was 25,000 feet, so the plane was operating safely below that maximum. And for about two-and-a-half hours, Flight 1750 continued on as planned, transmitting its position to the Perth Flight Service Centre, the Meekatharra Flight Service Unit, and the Port Hedland Flight Service Centre. About 30 minutes before landing, at 11:14 AM, the flight crew confirmed they would arrive in Port Hedland at 11:42. They also requested information about weather conditions in Perth, which indicated they were already preparing for their return flight.

A few minutes later, at 11:17, Port Hedland contacted the flight crew to let them know they should be aware of a Cessna 310 aircraft that had just taken off from the airport and was climbing to their cruising altitude of 9,500 feet. The flight crew made direct contact with the Cessna's flight crew and confirmed they were not close to each other and were not at risk of collision. Three minutes later, the flight crew let air traffic control know they would begin their descent from 19,000 feet at 11:23; air traffic control confirmed receipt of the transmission and also confirmed the weather information in Perth that the flight crew had requested. About 10 minutes later, Port Hedland also provided the surface wind and temperature conditions at the airport to help inform landing preparations, which included the altimeter setting for landing. The flight crew didn't acknowledge receipt of the information.

How did MacRobertson Miller Airlines Flight 1750 Crash?

It was around that time that Colin Brierly looked up into the sky and saw smoke drifting upward. He said, "My working boys, two Aboriginal boys helping me, they said, 'oh look, there's some smoke over there', and we knew there shouldn't have been anything going on down there so we decided to go and investigate. When we got within a few kilometres, we could see that there was a tail [of a plane] so we knew it was an airplane [that] had crashed."

In the control tower, Pat Seymour also knew something was wrong. He said, “When I didn’t get a response from the crew, I knew something had gone terribly wrong with the aircraft. Crews always respond promptly during this stage of flight." He also saw the smoke as it began to rise.

There were two known eyewitnesses to Flight 1750's final moments, and both reported that the aircraft descended rapidly and steeply. One woman described it as, "a silver aircraft spinning in the air." No one saw the plane make impact with the ground, and the fact that it did, indeed, crash was not confirmed until 11 minutes after impact, when the pilot of a Cessna 337 Skymaster that departed from Port Hedland saw the burning wreckage and reported it. It took more than an hour for a ground party that departed from Port Hedland to arrive at the scene. Colin Brierly was one of the first people to reach the scene by foot; he said, "We rushed around to have a look to see if anybody was alive and needed help, but there was just quietness and the fire making noises."

It was immediately clear that there were no survivors to be rescued from the crash site of MacRobertson Miller Airlines Flight 1750. The wreckage was widely scattered across a distance that extended more than 7,000 feet by 2500 feet. The right wing, including the number four engine, came to rest more than 3,000 feet away from the tail and rear portion of the fuselage. And that part of the plane was about 1600 feet away from the majority of the wreckage, including most of the passenger cabin and the cockpit. There was significant fire damage to most of the plane with the exception of the right wing, which was damaged but did not show any evidence that fire had played a role. In total, investigators found more than 90 significant pieces of wreckage outside of the main impact areas. And this provided them with a chilling clue as to what brought flight 1750 out of the sky too soon: the plane had broken apart in midair.

Why Did MacRobertson Miller Airlines Flight 1750 Crash?

Both the Flight Data Recorder and the Cockpit Voice Recorder were recovered from the crash site, and both contributed to the story of Flight 1750's final moments. The FDR confirmed that the airplane had been operating normally until just after the flight crew's final transmission to air traffic control. It indicated that, 12 seconds after 11:34 AM, as the plane was passing through 7,000 feet, there was some kind of catastrophic event that led to a complete loss of control. The FDR stopped recording at the point of impact, which was just 24 seconds later.

The official accident report stated, "It is apparent that the cockpit voice recorder continued to operate until the aircraft struck the ground. That part of the cockpit conversation which could be deciphered in the period prior to the aircraft reaching 7, 000 feet in the descent, indicates that the operation of the aircraft was completely normal and that the flight crew received no warning of the event which obviously induced a complete loss of control on reaching 7, 000 feet. Between this point and the completion of the recording at ground impact, there is no record of any cockpit conversation but, at 7,000 feet, a distinct change in the frequency and volume of background noise in the cockpit can be heard, and this continued until the ground impact occurred. The ambient noise recorded in this period seems to be consistent with that which might be produced by an aircraft moving at high speed and out of control."

Wing Damage and MMA Flight 1750

To the investigators, the right wing was the most suspicious aspect of the crash site; the wing was pretty isolated from most of the wreckage, which was an indicator that it may have failed first. Working backward, when the investigators looked at the part of the wreckage that contained the tail and the rear part of the fuselage, they determined that it had been impacted by overload; it wasn't a defect or a structural issue, it was a symptom of something else: the real cause of the crash. And so it was the wing that drew their attention and where they hoped answers might emerge. When the wing landed, a good portion of it was driven into the ground by the force of the impact; after all, it fell from 7,000 feet above the earth. It took two days for crews to dig the first part of the wing out of the ground in order to analyze it; parts had been driven three feet into the ground. It was heavily damaged, but beyond the damage caused by the impact, it was evident that there was something else at play. Across the wing's most inner section, where the break from the aircraft occurred, investigators found signs of metal fatigue.

MacRobertson Miller Airlines Flight 1750 Metal Fatigue

On the wing of a plane, there is a structural component called the spar, which plays a big role in carrying the weight of the plane itself. On the Vickers Viscount, the spar also has rims that are known as booms; they are basically protrusions from the spar, and the engine was attached to it. These parts are made of metal, and that means when metal fatigue came into play it caused the spar to fail in midflight. Because the spar carries so much of the weight of the plane, when the spar was out of commission the wing could not withstand the load, and so it separated from the plane. Without a wing, the plane could not sustain flight, and so it crashed.

The recovered wing was analyzed by Aeronautical Research Laboratories, and they determined that the metal fatigue observed by investigators was severe: it extended across 85% of the spar lower boom. They also discovered that the metal fatigue started before the plane ever took off from Perth, and it was not the result of any of the common reasons often associated with metal fatigue such as defects or corrosion. Knowing that metal fatigue seemed to be a major contributor to the crash and that these particular issues were in place for some time before December 31, 1968, investigators turned to the plane's maintenance records.

As with all components of airplanes, the spar lower boom wasn't designed to last forever. The plane's manufacturer and the certifying body, the Air Registration Board of the United Kingdom, had determined that the boom would reach its retirement age after 11,400 flights. However, the boom had  only 8,090 flights in its career. That's only 71% of its expected lifespan. Why would the part have failed so early? Investigators continued to look into the condition of the spar and boom, focusing on everything from design to maintenance, and as it turned out all they needed was a visual inspection of the part to zero in on what might have caused the boom to fail.

MMA Flight 1750 Maintenance Issues

On the Vickers Viscount, the spar boom attached to the wine in a location known as Station 143. Station 143 is a bolt hole; there were five bolt holes that connected the engine to the lower boom, and Station 143 was found closest to the back of the structure. According to maintenance records, the bolt at Station 143 was a replacement part that was supplied by the manufacturer, so it was an official part. It was installed when the previous spar boom had reached the end of its useful life.

Investigators found that, in 1964, the fitting for the boom was reinstalled as part of the replacement process, which was very much in line with what was recommended by the manufacturer; the airline wasn't required to replace everything on the wing when one only one piece reached its retirement age, so they replaced only the portion that required replacement, which was the fitting for the spar boom. But according to the accident report, when mechanics attempted to reinstall the old fitting with the new boom, there was a spacing issue with the holes that were predrilled for the bolts. They didn't all line up. Four of the bolts seemed to line up well, but the fifth bolt— the one at Station 143— didn't align with the predrilled hole in the attachment. And when investigators took a close look, they found that hole was counter drilled; the maintenance team basically attempted to force the fitting into place even though the alignment was off. That was further confirmed by evidence of deformation caused by what the report described as a conical tool as opposed to a machining process; it looked as though the piece had been hammered into place.

Investigators quickly ruled out a number of factors that could have contributed to the crash of MacRobertson Miller Airlines Flight 1750. They found no evidence of human error on behalf of the flight crew, no weather issues, and no weight and balance issues that could have brought the aircraft down just 10 minutes before its scheduled landing. All that was left was something the report called irrefutable: evidence of structural failure on the right wing. It was, in technical terms, "the failure of the boom at Station 143 was preceded by fatigue cracking at this point such that some 85% of the cross-sectional area of the boom was affected. The signs of progressive failure under cyclic loads are unmistakable, even to the naked eye, and the residual strength of the boom in its final state would have been such that it may well have failed under steady flight loads." In layman's terms, it was a misaligned bolt forced into place by a mechanic.

One big question that emerged was when this might have happened and why no one would have noticed the metal fatigue; even after the crash, the cracks in the boom were clear and obvious to the naked eye. Unfortunately, this part of the wing would never have been inspected without a full disassembly, which only happened during a full disassembly of the wing itself, which would only happen during a pretty major routine maintenance effort. Along those lines, the report noted that there really wasn't technology in place that could have aided inspections without a full disassembly, such as radiographic or ultrasonic techniques; this was 1968, and inspections didn't benefit from some of the more modern safety options we have now.

The biggest question, though, was why the boom fitting seemed to have been forced into place. Investigators attempted to find out why this happened, and more importantly, who was responsible. Ultimately, they were not able to identify a single person or group of mechanics who made the deadly decision to hammer the fitting into place, setting in motion the early failure of the part, the metal fatigue, and the catastrophic wing separation that sent Flight 1750 into a crash sequence. The crack in the metal that stemmed from Station 143 most likely started 4 to 5 years before the crash, and it was impossible to assign responsibility to whomever made that horrific mistake. And the final accident report did not hold back in the clear frustration related to this note: it said, and this is a direct quote from the report, "The second difficulty was to imagine a situation, arising either in manufacture or in the installation of the boom, which would induce any responsible tradesman to use the type of tools or to follow the practices that the physical evidence reflects."

What is the legacy of MacRobertson Miller Airlines Flight 1750?

In Australia, the Department of Civil Aviation temporarily grounded all of the Vickers Viscount aircraft in the country. Eventually, this grounding became permanent. And for those planes still in the air outside of Australian airspace, the British Aircraft Corporation and the UK Air Registration Board lowered the retirement age of the lower boom from 11,000 flights to 7,000 as a precaution. After inspecting other booms, they found evidence of metal fatigue in 16 of 19 booms inspected, and while the fatigue was not necessarily because of shoddy maintenance practices, it did encourage them to take action.

More than 50 years after the crash, in 2019, a plaque was unveiled at Port Hedland's Dalgety House museum to remember the 26 people who perished with the Vickers Viscount. And yes, you heard that right: for half a century the victims of this air disaster did not have a permanent memorial in place to remember them. Port Hedland Historical Society vice-president Julie Arif said, “This was a devastating event for the townsfolk of the small town of Port Hedland, as it impacted everyone— people they knew on the plane, or people who were assisting in the recovery of the bodies and investigation.” Every person's name is inscribed on the plaque. This brought peace to Colin Brierly, who along with his workers were the first people to arrive at the accident scene.

For years, Colin Brierly— who worked the land near the crash site for more than half a century— continued to find pieces of the plane and passenger belongings. One of the most haunting finds was a victim's watch, with the hands frozen at 11:35 AM— the time of impact. The watch was found 40 years after the disaster occurred. On the property, not very far from the crash site, there is a sign that reads: “This memorial was moved from the original crash site because of mining activity in the area, and it was thought that this would be a more serene and beautiful place to remember those who died on that fateful day.”

Show Notes:

We start this week's episode with a story shared by a fellow listener, Sarah, who told us about an unlikely item that saved a man's life during a plane crash. We might be investing in foam hats after reading this one!

Credits:

Written and produced by: Shelly Price and Stephanie Hubka
Directed and engineered at: Snow Monster Studios
Sound editor: Stephanie Hubka
Producer: Adam Hubka
Music by: Mike Dunn
MacRobertson Miller Airlines Flight 1750

MacRobertson Miller Airlines Flight 1750 crash site. Source: ABC)

MacRobertson Miller Airlines Flight 1750

Wreckage of MacRobertson Miller Airlines Flight 1750. Source; WA news

MacRobertson Miller Airlines Flight 1750

MacRobertson Miller Airlines Flight 1750 Memorial. Source: Monument Australia

MacRobertson Miller Airlines Flight 1750

A watch found at the crash site, frozen at the time of impact. Source: ABC