Earning its upkeep

This story is sourced from Flight International
Subscribe today »

Guy Norris/LOS ANGELES Max Kingsley-Jones/LONDON

THE BOEING 777 WAS launched into revenue operations on 7 June, 1995, with United Airlines, when the US airline began to operate its first Pratt & Whitney PW4000-powered aircraft between London Heathrow and Washington DC. For several months United was the sole 777 operator, but, in November 1995, British Airways introduced a General Electric GE90-powered version on its routes to the Gulf. In March this year, a Rolls-Royce Trent-powered 777 was handed over to Thai International, and by the beginning of September, some 35 aircraft were in service with eight operators around the world.

Boeing and United, which launched 777 production in October 1990, view the first year of operations with mixed emotions. Both agree that the 777's initial reliability has been outstanding compared to that of any airliner before it, but both also admit that the year revealed unexpected snags, despite intensive efforts to "wring out the bugs" before delivery.

In particular, both are anxious to heal the wound caused by the leak of a letter to the Wall Street Journal in March in which United fiercely attacked the reliability of the 777. The letter from fleet operations executive vice-president, Joseph O'Gorman to Boeing 777 general manager, Ron Ostrowski, said that the aircraft's performance had been "a major disappointment" (Flight International, 13-19 March).

Although United tried immediately to play down the letter, much of the damage had been done - at least publicly. Privately, Boeing and United believed that they had most of the outstanding problems well in hand by the time the letter was published.

Part of the problem was that Boeing, and the small group of launch-customer airlines, which helped to define the 777, set stiff performance targets from the outset. The "service-ready" initiative was aimed at delivering the 777 with built-in despatch reliability of 98% and above from the beginning. Consistently high levels like this are normally expected after three years in operation, and "service ready" became a fundamental driver of 777 development. Equally demanding, and just as unusual, was a pledge to deliver the aircraft ready to be flown on extended-range twin operations (ETOPS).

United now admits that it may have set its sights too high. Its Boeing acquisition programmes manager, Gordon McKinzie, says: "Our expectations were very high, and we suffered some unexpected mechanical problems. We had super-optimistic results in mind and we may have been unrealistic." In terms of mechanical schedule-reliability, United's 12 aircraft were measured at 97.9% a year after the type's introduction. "Our target is 98.5% and it's starting to stabilise towards that already," says McKinzie, who adds that the lowest figure was 96.5%. Boeing assesses cumulative schedule reliability based on data reported by the 777 operators, and says: "The 777 is about two years ahead of the 767 and even further ahead than the 747-400. We're on target for 98% schedule reliability within 18 months."

McKinzie is quick to point out that the 777 was "-thrown in at the deep end", and that United flies a fleet average of 10.5h/aircraft a day. If intra-US flights are excluded, the airline's 777 daily utilisation, rises to an average of 12h per aircraft. "It's working very hard for us. We didn't 'baby' this aircraft like we did others. Instead, we put it straight into a very busy day-to-day schedule."

Boeing and United admit that some things were omitted from the rigorous ETOPS qualification flights, which would have helped uncover subsequent problems. "We had no people flying and working in the cabin on the ETOPS runs. If we had, we'd have discovered a few things a bit earlier. The cargo-loading system has given us problems and we didn't move any cargo, either, during the trials," says McKinzie.



One cabin problem, which cropped up in the first few months of winter operations, was a frozen passenger-door arm/disarm mechanism. "We never opened those doors [passenger door No.4] in the ETOPS trials. We ended up using the flight-attendant's hair dryers to defrost them," he adds. The problem was traced to an undetected moisture path, which led to water collecting around a cable seal. "It ended up causing a lot of heartburn," says Boeing 777 service engineering manager Fred Mazzitelli. "We did some rerigging and improved the sealing, which cleared it up," he adds.

The cargo-system problem relates to pop-up flanges, which guide cargo containers inside the hold. Springs, which activate the guides, have been breaking, but these will be replaced with new hardware beginning in mid-1997. "We didn't appreciate the cargo-loading environment as much as we could have," says Mazzitelli. "We got some priorities for redesign items from a cargo-loading seminar which we held."

Another problem with failing springs is also being tackled, this time in the main undercarriage. Dual-redundant springs, which help the landing gear to retract, "-have been cracking from day one", says McKinzie. "We didn't have it on the minimum equipment list, so we have had to replace them before flying. We therefore got involved with the FAA [US Federal Aviation Administration], to show that we could despatch with one spring," says Mazzitelli. "We're also redesigning it and will soon flight-test the new one."

Boeing is also flight-testing a "modal suppression," or high-rate damper system, which will correct the yaw oscillation experienced in cruise on some flights. "It only happens after [the aircraft] encounters turbulence," says McKinzie, and aircraft are expected to be fitted with the modification from September. The system "-will take the wag out of the tail" and is similar to that fitted to the 747, 757 and 767, says Mazzitelli.

Another change now under way is the relocation of one of the aircraft's three VHF (very high frequency) communications antennas from the belly to a site on the roof of the aircraft. Antenna reception was being affected by electromagnetic interference "-leaking through a crack in the electronic bay door," says McKinzie. "The FAA said we could not despatch if all three antennas were not operating and we took some cancellations because of it."

The affected antenna was moved to the upper aft fuselage and flight-tested. "We've briefed the airlines and are looking at speeding up that change," comments Mazzitelli.

United's original list of "around 100" open items had been reduced to 30 by mid-1996 and all these were being attended to. McKinzie expects the last to be cleared up by the end of the third quarter. "That's why I was a little concerned about the O'Gorman letter. Work on all those points [11] was already in hand, and nearly all of them have now been worked out."

In most cases, United reports "pleasant surprise" at the lack of problems from sophisticated systems, such as the aircraft information-management system (AIMS) which was widely expected to be a maintenance headache. "We're not finding any new things now. Things like AIMS are working fine. If there are any false alarms they're usually tied to the sensor itself."

Engine reliability has been the single most important element of the 777's first year in service. With so much emphasis placed on "out of the box" ETOPS, and service-ready delivery, the performance of the power plant has been under the microscope from day one.

The Pratt & Whitney PW4084-powered 777, was the only one of the three versions to be cleared for 180min ETOPS before service entry. Over 40% of the revenue flights operated by PW4084-powered aircraft have been flown under ETOPS conditions.

The engine has also been shown to have dispatch-reliability levels of 99.9% with no in-flight shutdowns, a feature which potential 777 users "-are beginning to look a bit closer at now", says Robert Wolfe, president of large commercial engines at Pratt &Whitney. Service introduction was not without its problems, however, and P&W has response teams stationed at every major hub into which PW4084-powered 777s are now operating. Early issues related to cracking oil lines, slow engine starting and higher-than-expected oil consumption have "largely been overcome", says the company.

While P&W considered itself under intense scrutiny, General Electric's GE90 engine was watched perhaps even more closely as it entered service with BA. The engine experienced an unexpected surge, during a pre-delivery shake down flight in early December 1995 and blade-tip clearance was increased by 1.3mm as a result.



BA was forced to ground temporarily two of its three 777s on 31 January, shortly after services began, after tears were discovered in kiss seals on the thrust-reverser ducts, for which Boeing holds responsibility. The airflow seals were deteriorating more quickly than expected, and the resulting problems "-caused a few headaches". A seal change was introduced, and a vane is being installed which will correct airflow through the duct and eliminate vibration.

David Cooper, BA's 747/777 fleet development consultant and, throughout the development and introduction of the aircraft, the airline's 777 engineering manager, says that since that early grounding, close monitoring of the kiss seals has enabled a high level of reliability to be attained, and the airline's 777 operations have since been "running very smoothly".

BA describes the big twin as "-a robust aircraft, free from the problems which have accompanied previous new types from both US and European manufacturers". Cooper points out that Boeing effectively delivered "-a mature aircraft from day one, with none of the nightmares that had been anticipated by engineering actually occurring".

Cooper says that the airline experienced "nil-reliability problems" with the avionics, which he attributes to Boeing's use of a system-integration laboratory. "This ironed out all the bugs before the aircraft went into service," he says.

BA's 777s are unique in that the airline specified a para-visual director guidance system for the aircraft, which provides steering commands during low-visibility take-offs. The system, which dates back to the airline's Category III all-weather operations with the Hawker-Siddeley Trident and Lockheed TriStar, is now fitted, in electro-mechanical form, to its 747-400s and 767s. Smiths, has developed a liquid-crystal-display version for the 777, and this is installed in the glareshield.



The airline's involvement in the joint effort to achieve "instant ETOPS" enabled the engineering team to work with the aircraft during the flight-test programme, says Cooper. "In March 1995, a team of BA engineers visited GE's plant at Peebles, Ohio, where we undertook a number of line-replaceable-unit changes in front of FAA inspectors as part of the ETOPS validation process...this kind of direct involvement with the aircraft at such an early stage provided a good grounding in maintenance procedures," he adds.

Capt Kevin Mottram, BA's 777 flight-manager technical, has been with the programme since 1991, and joined the aircraft from the 747-400. "Initially, when we introduced the aircraft, we had 15 [sets of] flightdeck crews trained [ie 30 pilots], all of which came from the 757/767 so that they had two crew/glass-cockpit/ETOPS experience. We now have 35 crews, with the more recent arrivals converting from all over the fleet".

Mottram says that the flightcrews are "delighted" with the handling, reliability and performance of the 777. "We like the way the flight-control system removes the pitch couple when changes are made to power, flaps or speedbrake settings...the aircraft trims out beautifully with good speed stability," he says, adding that "-the [ground] steering is 'unfaultable', as are the wheelbrakes, which are a lot better than the other Boeing twinjets."

Mottram says that although the original specification anticipated a cruise speed of Mach 0.83, in practice "-the aircraft seems to be most comfortable at Mach 0.84". He adds that the take-off/climb performance of the aircraft is "-excellent, we regularly depart Dubai [for London] with a full fuel and passenger load, ie at a weight of around 235,000kg, and climb straight to FL390 [39,000ft]-this enables us to avoid the lower-altitude operating restrictions in the Saudi Arabian airspace".

The 777 is unique among airliners in that it is equipped with a pilot's "mouse" (or cursor control device - CCD) which is used to select items on the multi-function displays, electronic checklist, and the aircraft communications and reporting system. Mottram says that the CCD works well, providing "excellent control of the pointer, even in severe turbulence".

Most of BA's early problems relate to the functionality of the GEC-Marconi InFlight Systems IFE system, and the airline is running at about 96% technical despatch reliability (TDR). David Hamilton, BA's 777 project manager, says that the airline is now testing a new modification for the IFE system, which "-should eliminate most of the problems and bring the system close to the original performance and reliability specifications by the end of September".

The TDR for the engines, is running at 99.9%, "-the envy of the other engines we have in the BA fleet," says the carrier. The engine's fuel efficiency and environmental impact have also been noted by the airline. According to measurements by BAA, the UK-based airport group, the GE90-powered 777's "quietness co-efficient" is 0.5 for arrivals and 1.0 for departures. BA says that this is quieter than its turboprop-powered British Aerospace ATPs, and its 757s and "United Airlines' 777".

Four 777-200As (ie, low-gross-weight version) are now in service with BA, which are operated mainly to the Gulf. The airline's fifth and final -200A, which is now undergoing test flying with the higher-thrust GE90-92B engine, will be delivered in March 1997 after refurbishment. With ETOPS approval yet to be granted, BA's 777s have initially been flown on services from London to the Gulf and to Paris. When the long-delayed ETOPS certification is granted in October, BA will begin 777 services to the USA, initially serving Boston.

BA will receive the first of 13 777-200IGWs (increased gross weight) in February, and expects to be operating a fleet of 14 777s by the end of 1997. These longer-range models will enable the airline to serve the US West Coast with the aircraft.



R-R, as the third engine manufacturer to fly its engine on the 777, is still in the early days of its operational experience, with seven Trent-powered aircraft in service with three airlines, Cathay Pacific, Emirates and Thai Airways International. Some early problems with a cracked radial drive shaft and oil leaks on the Thai aircraft have affected the manufacturer's initial record, although solutions have quickly been developed.

The auxiliary power-unit (APU), the traditional villain of all airline-reliability statistics, has proved to be a steadfast performer during the aircraft's first year. "In what may be an industry milestone, AlliedSignal Aerospace's 331-500 APU has completed more than 30,000h of revenue service while demonstrating record reliability," says the APU maker.

Before its introduction, BA had been concerned about the potential embarrassment of an APU failure at an outstation, and the lack of any starter unit capable of turning a GE90, but, in practice, the airline has been happy with the unit's reliability. AlliedSignal says that its mean time between failure "...is 33,000h, and continues to grow".

The APU was subjected to a rigorous test effort before service entry and was the first APU to show 180min ETOPS capability before the June 1995 entry-into-service date. More than 20,000h of testing and 22,000 starts were achieved before its operational start.