The Comet and the Dawn of the Jet Age

The story of the de Havilland Comet, the first commercial jet, is one of a great national triumph, great tragedy, and a giant missed opportunity.

Welcome to the Jet Age

On July 27, 1949, test pilot John Cunningham flew the British Comet prototype straight into the history books. The Americans had emerged from World War II dominating civil transport with Douglas producing countless DC-3s and DC-4s and Lockheed selling as many L-1049 Constellations as it could produce. But these were propeller-based aircraft, not jets; who would dominated the Jet Age? The British might very well have thought they would watching the de Havilland D.H.106 Comet fly that day. It was after all the first civilian jet transport and would remain so for five years - an incredible lead in such an important industry sector.

Success

Nearly three years of work had gone into the Comet by the time of that first flight and nearly three more years would pass before the first passenger flight by BOAC (British Overseas Airways Corporation, the government owned overseas airline). The aircraft that emerged was powered by four Rolls-Royce Ghost engines, could carry 36 passengers at altitudes of 40,000 feet (for comparison, a brand new 2003 Boeing Next Generation 737-900 has a ceiling of 39,000 feet!) and had a cruising speed of almost 500mph.

The first flight with paying customers came on May 2, 1952, with a BOAC flight from London to Johannesburg. Existing route times were halved and load factors were 90%. Now everyone wanted one. Orders from Air France as well as Canadian, Australian and Middle-Eastern nations poured in.

By September, a confident de Havilland announced the longer range Comet 3, which would be used for transatlantic flight. This brought an order from Pan Am. At last, an order from an elusive American airline! Soon thereafter, Capitol Airlines placed an order for the Comet 2 for regional service.

The Comet not only gave the British, who were still recovering and rebuilding after a second World War in as many generations, a great sense of accomplishment, but they loved flying it. Its incredible speed was unrivaled, it flew high above the turbulent weather and its smooth jet engines caused far less vibrations than contemporary aircraft. Orders and acclaim for the remarkable aircraft continued to flow from all over the world until...

Tragedy

On October 26, 1952, the first in a series of misfortunes which were to prove the Comet's undoing occurred on a flight leaving Rome. The flight was part of the London to Johannesburg service and Rome was a scheduled stop. On this night, the captain apparently pulled back too far too early on takeoff and attempted to abandon the takeoff too late resulting in the aircraft's destruction beyond the end of the runway. Remarkably, there were no fatalities among the 43 on board.

An investigation blamed the pilot and new instructions were given to all Comet crews, but the British Airline Pilots Association was not pleased with the finding believing it was fundamentally a problem with the new Comet.

Then in early March of 1953, Canadian Pacific Airways (CPA) agreed to allow their newly-built Comet to be delivered to them via Australia so the de Havilland sales force could "wow" the Aussies (Qantas was in love with the Lockheed Constellation). On March 3, 1953, while taking off in Pakistan for Rangoon, the pilot put a Comet in a early nose-high attitude during takeoff (just as in Rome) and was unable to gain altitude. This time the aircraft exploded on impact beyond the runway killing not only the crew of five but six de Havilland support personnel sent to aid CPA with their new Comet.

The Indian investigation revealed that the captain had been made aware of the Rome incident and the new takeoff procedures, but was probably unable to determine his nose-up attitude until it too late due to the crude (relative to today's standards) instruments available to him and the dark haze he was flying through. In any case, a pattern was emerging. While the trip was intended to boost confidence in the Comet, it obviously ended up being a PR nightmare. Not only was Qantas unimpressed, but CPA promptly cancelled its orders as well.



		Metal Fatigue Metal fatigue is a phenomenon first discovered by railroad engineers in the 1880s. A number of accidents involving failed train axles led engineers to describe the parts as being "tired," or "fatigued." Today we understand metal fatigue as the development and spreading of micro-cracks in the matrix of metal atoms and crystals. These cracks spread when forces less than the force needed to tear or crush the metal are applied and released over and over. The cracks eventually grow so large that there is not enough uncracked metal to take even the low loads. You can see metal fatigue in action by taking a spoon and bending it back and forth until it breaks (kids: do get your parent's permission first!). Each time an airplane takes off, the cabin is pressurized for passenger comfort. This causes the skin of the aircraft to expand and contact each time. Airlines must monitor their aircraft for such wear and not fly them beyond their expected durability rating. Cracks in the Comets started at the edges of the square windows and led to explosive decompression at altitude. That's why today's jets have rounded windows and doors.
		References: Brent Wellman of NASA

Even so it was only two crashes, and no paying passengers had been killed and it was still possible to blame the pilots; the Comets continued to fly. However, May 2, 1953 - one year to the day after the first passenger flight - brought forth a new deadly pattern: A Comet flew into a storm with a crew of six and 37 passengers and exploded over India at 30,000 feet. The investigators assumed it was as a result of flying into severe turbulence. The next tragic event would have them reconsidering this finding.

On January 10, 1954, a flight crew of six and 29 passengers departed Rome's Ciampino Airport for London on the final leg of journey that had started in Singapore. This aircraft was the same that made history on May 2, 1952 inaugurating jet travel. At about 27,000ft the aircraft exploded with debris falling into the ocean off the coast of Italy. This time weather could not be blamed. But what was the cause and had it also brought down the earlier Comet?

Now that there really seemed to be a problem with the Comet, the British Ministry of Transport and Civil Aviation was brought in to investigate and every piece of wreckage that could be located was brought to a hanger for scrutiny. Additionally, a Comet fuselage was set up in what was essentially a large swimming pool to simulate the effects of pressurization that happens each time the Comet flies. If there was a problem with metal fatigue, these tests should show it. (Before the Comet ever flew, de Havilland ran similar tests which showed a Comet should be able to handle 18,000 flights. The latest Comet to crash had only 1200.)

In the meantime, BOAC and de Havilland officials met to decide what, if anything, should be done to existing Comets before putting them back in service. All Comets were flown without passengers to London and investigators made some fifty recommendations to be carried out before returning the Comet service.

Investigators required stronger casings around the engines on the unsubstantiated notion that perhaps a blade from one of the engines had broken free and ruptured the fuselage. At the end of March, 1954, with no real progress being made in solving the case and with the fuselage in the "swimming pool" showing no signs of failure, British officials agreed with BOAC that there was no reason to keep the Comet grounded and flights resumed on March 23rd as the investigation continued.

That decision proved deadly shortly thereafter when on April 8th, a BOAC Comet on a charter flight for South African Airways left Rome for Cairo carrying a crew of seven plus 14 passengers. The Comet made a routine call to Cairo air traffic control 32 minutes after takeoff at about 35,000 feet and was never heard from again.

What little wreckage could be found floating in the ocean revealed that this was once again a case of a Comet breaking up in flight and once again weather was not a factor. Even for British officials keen on keeping the Comets flying, this was too much; all Comets were grounded by Prime Minister Winston Churchill on April 12, 1954. Churchill said, "The cost of solving the Comet mystery must be reckoned neither in money nor in manpower." The most extensive and expensive air investigation to that point in history was undertaken.

Meanwhile on the other side of the world Boeing was rolling out what would become the 707 prototype, the Dash-80 and Douglas - though quite busy filling orders for its highly successful DC-6 and DC-7 - was working on plans for the DC-8. Closer to home, the French were busy catching up (and relaunching their post-WW2 aviation industry) with the Caravelle jet. Even the Soviets were rumored to have a jet in the works. The world was not going to wait while the Brits worked out their Comet issues.

The wreckage of the latest Comet causality lay buried in 2000 feet of water. No problem for late-20th century equipment but impossible for mid-20th century technology. All hope in finding the cause lay with the previous wreckage... and the fuselage still being tested in the water tank.

Mystery Solved

In late May, an important discovery was made. The tail section of the second Comet to explode was found and had carpet from the inside of the aircraft embedded in it. As the tail section landed far away from the rest of the plane, this could only have happened as a result of a rapid decompression. Had it been the result of metal fatigue?

Then in June, the fuselage in the water tank finally failed after the equivalent of 9,000 hours of flying. An eight foot long crack developed below a window and escape hatch. But none of the recovered debris had shown such cracks. Finally in July more debris was brought up from the ocean and this time such a fracture was found.

Aftermath

The lessons learned were incorporated into future designs of the Comet, as well as all of its competitors. In fact, in the fifty years since these accidents, not one civilian airliners has crashed as a result of this particular phenomenon (cabin pressure fatigue failure).

The British aviation industry never recovered and instead were left to contemplate what could have been. The five remaining Comet 1s remained permanently grounded and only a few Comet 2s were sold to the Royal Air Force.

de Havilland continued to improve the Comet line even as the investigation wore on, but only one Comet 3 was completed and it was used only for testing. The Comet 4 was the last attempt at getting this once-proud bird back on top and it just couldn't compete with the Douglas DC-8 and especially the Boeing 707. The final blow came when the government owned BOAC gave in and ordered 707s in 1958.

The British went on to produce jets such as the BAC One-Eleven, the Trident, and Vickers VC-10 and they participated both in the joint development with the French on Concorde and in the European consortium Airbus, but they never again led the industry they not only dominated but created in the early 1950s.

Could It Have Been Prevented?

It has been suggested countless times that the Comet failed as a result of the previously unknown phenomenon of metal fatigue. It was not previously unknown to movie star Jimmy Stewart.

Stewart starred in the underrated 20th Century Fox movie No Highway in the Sky, in which he portrayed an absent-minded professor who has come up with an novel theory on metal fatigue as it pertained to these new pressurized jetliners. This movie premiere in the US in September 1951 - a full three years before the first Comet failed!

The fictional professor (a scientist in the book) calculates that a particular aircraft will fail within a certain number of cycles (takeoffs and landings) and that a particular aircraft is about to exceed that number! He tries to warn officials but no one takes him seriously. I won't ruin the ending for you but suffice it to say that metal fatigue of the kind the Comet was suffering from may have been a new concept, but it certainly was not "previously unknown."

In fact, this movie was based on Nevil Shute's novel No Highway, which of course predates the movie. Shute, a former Vickers aeronautical engineer wrote it as a cautionary tale due to his concern that British aviation officials were not taking the problem seriously enough.