Engine problems almost grounded many early Boeing 747s as airlines grappled with huge teething problems with the giant jet.

All new aircraft designs go through teething problems as airlines introduce and get to know them – their virtues and vices.

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The Boeing 747 however, was to be much, much, worse as it was a quantum leap in size with a massive new - and unreliable - engine and at the same time as its introduction traffic tanked around the world. 

All of a sudden the 747 appeared to be blamed for everything that was wrong with the industry.

However, the problems with the 747 were real, with a survey done by Aviation Week in early 1972 revealing that every 747 airline had major gripes about the P&W engine with too-high fuel consumption, premature removal rates and difficult inspections.

However, at the time Boeing pointed out that no aircraft – either commercial or military – had achieved what the P&W JT9D had of powering the 747 feet for 616,500 hours, 277 million miles and carrying 19 million passengers all in under two years.

By November 1971 the reliability rate had climbed to 95.4 per cent.

However, one of the big selling points of the 747 was its cruise speed of Mach 0.90 and cruising altitude of over 35,000ft.     

Airlines were finding that the cruise speed was Mach 0.84 and the altitude was more like 32,000ft, down in the 707 and DC-8 traffic, so the 747 couldn’t fly over the slower single-aisle jets that cruised at Mach 0.82. Also, the time to climb performance was not as specified. Engine improvements over time would address the issues.

But airlines were reluctant. National had its 747s up for sale when it first took delivery, Eastern was to return its as soon as Tristars were delivered, while United, JAL and Iberia had all delayed delivery. Braniff mothballed one of its two 747s, while Pan Am was only operating 27 of its 33.

Lounges were a factor in swaying passengers back to the 747.

In a survey done by American Airlines, and reported by Aviation Week in February 1971, before economy class lounges were introduced, only 52 per cent of passengers preferred the 747, with 32 per cent preferring other jets with 16 per cent having no preference.  In May of that year, American introduced lounges and the numbers preferring the 747 leapt to 76 per cent with only 9 per cent preferring another jet type and 15 per cent having no preference.

And 3 out of 4 said they would delay their departure by up to three hours to get on a 747.

American’s load factor jumped from a paltry 29.4 per cent in the first quarter of 1971, to 44.8 per cent in the second to 53.6 per cent in the third. Part of that is due to the decrease in seating by installing of the lounges.

The hard US industry passenger numbers for the 747 for the first three quarters of 1971 were: 113.7, 140.2 and 167.8, with seating dropping from 348.8 to 342.3 to 335.6 as most airlines added lounges.

Most airlines were very high in praise for the attention Boeing and P&W addressed the engine problems.

There is no question that early 747 deliveries were the worst, with airlines such as SAS, Swissair and Qantas that opted for much later – 14 months – delivery which were very high in praise for the jumbo jet. In fact, SAS, told Aviation Week that the 747 was the best for reliability of any new aircraft it had introduced.

By contrast, United which took delivery of its first seven months after the first for Pan Am was not happy.

“We expected it to be better than any previous aircraft, United’s SVP-engineering and maintenance Marvin Whitlock told Aviation Week. “We thought we had the right to expect mechanical reliability to improve with each successive new model as the start of the art improves.”

Continental was also unhappy threatening to ground its 747s at one stage.

Problems with the engine were unprecedented and in fact, caused P&W’s parent United Aircraft Corp to lose money for the first time in its history with airline officials saying in early 1972 that it would take another five years to get the engine right. The gravity of the situation at the time was highlighted by Air Canada’s 747 Program Manager Duncan Marshall, who told Aviation Week that the airline had to do an inspection of first-stage turbine blades every 100 hours, and second-stage every 200 hours, with borescopes to find cracks; inspections of outside fan rotor blades for cracks; inspection of diffuser case for cracks and first stage compressor stators checks.

Marshall blamed the new titanium alloy used in the turbine and compressor blades.

And the problems would have been far, far worse had it not been for the invention of the borescope, which had been invented in the 1960s by Indian-born American physicist Narinder Kapany and American optical physicist Brian O'Brien.

United’s Whitlock, joked to P&W that the borescope had saved the JT9D. “I told P&W that they ought to find the guy who invented it and give him some kind of medal.”

Pan Am bore the brunt of the engine problems with its VP of maintenance saying that when things went wrong – which was often – the airline was “hard-pressed not to ground the entire fleet.”

By early 1972, P&W had fixes in hand and was shipping the vastly improved JT9D-7. Solutions had been found to the stall margins, many inspections had been eliminated and fuel consumption was much better. At the time it cited the JT9D-7 at 13,000 hours as having just two inflight shutdowns and one removal compared to the  JT9D-3A having 14 removals and 8 inflight shutdowns.

On the flip side one area that airlines thought would cause problems – ground handling – did not.

The overall experience was far better than expected, due to the huge amount of time and money put into the preparation for the 747. Major airports across the globe spent millions on the expansion of facilities to handle the 747 passenger loads with that investment paying off.

By the close of 1972, three years after its introduction the 747 was bringing smiles to all and of course, would go on to be the most loved of all the jets.