Andrzej Jeziorski/SINGAPORE Max Kingsley-Jones/LONDON
Although Airbus Industrie pioneered the widebody twinjet concept in the early 1970s, its rival Boeing has developed the configuration to its ultimate size and weight, with the 777 family.
When it flew in June 1994, the 777-200 was the world's largest and heaviest twinjet, taking over the mantle from the Airbus A330, and it offers the greatest range for such a design. It is powered by the highest thrust turbofan engines ever certificated - 75,000-98,000lb thrust (334-436kN) - and was the first twinjet to have 180min extended range twin-engined operations (ETOPS) approval in place at service entry. The latter was part of the manufacturer's intense effort to provide a mature, service-ready airliner at introduction.
These twinjet achievements were taken over by the 777-300 when it flew in October 1997, along with another record: its length of 73.8m (242.3ft) makes it the longest airliner built (a full technical description of the 777-300 appeared in Flight International, 3-9 December, 1997).
The introduction of a stretched derivative three years after the 777-200 arrived in 1995 was planned from the start, so when Cathay Pacific Airways received its first 777-300 in May 1998, it was part of a Boeing master plan set at the start of the decade. Boeing probably wishes the much delayed ultra-long-range 777-200X/300X derivatives had been able to follow their original development timetable as closely.
The higher capacity -300 stretched version was aimed specifically at the Asian market and at operators looking to replace Boeing 747-200s. It was no surprise that when the stretched model received its go-ahead in June 1995, the four airlines which had placed 31 launch commitments were All Nippon Airways (ANA), Cathay Pacific, Korean Air and Thai Airways International.
The aircraft features a 19-frame, 10.1m stretch over the baseline -200, increasing typical seating to 368 (three-class) or 451 (two-class). Typical range with 368 passengers up to 10,545km (5,700nm). The 60.9m span is retained, but the larger model has strengthened fuselage sections, inboard wing and nose/main landing gear.
Boeing has offered the stretched version with powerplants from each of the "Big Three", including the Pratt & Whitney PW4090/4098, Rolls-Royce Trent 892, and the General Electric GE90, although no airline has specified the latter. Ironically, the planned longer-range version, the -300X, is only available with the GE powerplant.
The first 777-300 to fly, on 16 October, 1997, was the R-R-powered version, which received US Federal Aviation Administration certification in May 1998. Launch customer Cathay Pacific took delivery of the first Trent 892-powered example the same month, while ANA was the first P&W customer, receiving its first -300 in June 1998.
By January, 31 777-300s were operating with eight airlines, and 17 more were on backlog. Sales for the stretched twinjet have slowed since the flurry at launch, with few new orders announced in recent years. Emirates has, however, chosen the model for its trunk routes to Europe and recently introduced the first two of four -300s it is acquiring on lease.
Stretch supporter - Cathay
Cathay had been eager for a larger 777 model from the start of the programme. Its initial order in April 1992 for up to 22 777-200s (11 firm orders/11 options) included the right to convert some options to the stretched version. "It's almost a two-engined [747] Classic. The Classics were to be phased out and this is a big aircraft with the economies of a twin on regional routes," says Cathay engineering director Derek Cridland.
The Hong Kong-based carrier operates the type on high-density routes such as those to Bangkok, Seoul, Singapore and Taipei, as well as to destinations in Japan.
Cathay was among the "Working Together" airlines that had input into the 777's design. Cridland says that the airline insisted on the installation of three external cameras - one in each wingtip and one under the fuselage - to help pilots manoeuvre the long aircraft on the ground. The airline was also involved in ETOPS trials and on the maintenance side.
The engine selection was influenced by the carrier's experience in operating the R-R Trent 700 on its Airbus A330-300s. "It made sense to build on the Trent family," says Cridland. Flight operations director Kenneth Barley adds: "Bearing in mind the role we specified [for the 777-300] we are extremely happy [with the powerplant]."
The engine's thrust - rated at 92,400lb, although Cathay says it uses only 84,000lb on take-off - is more than adequate for Cathay's operational maximum take-off weight of 263t, says Cridland.
He says the type is "a very easy aircraft to maintain", adding that "there is nothing that irritates". Cridland is especially pleased with the flightdeck maintenance access terminal, through which all aircraft information can be accessed. "It's a very honest aircraft," he says.
While he believes there are "no particular concerns" with the aircraft's maintenance, Cridland notes that Cathay had originally worried about engine transportation due to the Trent 800's bulk. However, the airline has found that removing the engine cowling allows it to fit on the main deck of a Boeing 747-400 freighter - in contrast to the General Electric GE90, where the fan must be split from the engine core.
Cathay claims an above-average dispatch reliability of 99.03% in 1999, using the aircraft an average 8.1h a day, with average sector lengths of about 2.6h by December statistics. The airline says it is happy with its dispatch reliability: "Obviously, if anything should fail, we want to improve it," says Cridland.
Cathay has experienced back-up generator problems, as have many other 777 operators, but Cridland says "there is a modification which changes the design of the [generator drive] shaft." The shaft is designed to fail in shear in the event of a mechanical failure to minimise damage and has been redesigned to fail at lower loadings. Cathay introduced an oil-level inspection procedure to monitor the problem "before it became an airworthiness directive[AD]", he says.
Barley says flight handling is "very, very good, be it a -200 or -300-particularly in crosswinds, and particularly the -300". Crosswinds were an issue at the old Hong Kong Kai Tak Airport and have been at the new Chek Lap Kok.
He mentions the asymmetric compensation system as a particularly welcome development in the flight control system. As to ground handling, Barley says the length of the aircraft "was an issue for a week, and then forgotten".
Japan dichotomy - ANA and JAL
Japanese carriers ANA and Japan Airlines (JAL) were members of the 777 customer advisory group from the start and early customers for the baseline 777-200 as well as launch customers for the -300. ANA operates 16 777-200s, one -200ER and five -300s that are flown mainly on its intra-Asian routes. The airline's 477-seat 777-300s ply routes previously operated by the 747-100SR, including mid-to-high volume domestic routes such as Tokyo-Hiroshima, Tokyo-Osaka and Tokyo-Sapporo. The carrier says each aircraft is averaging 6.08h daily use, or 4.85 cycles a day, on average stage lengths of 1.25h. ANA says it is "pleased" with the aircraft's dispatch reliability, which it quotes as 99.67% on domestic routes and 99.39% on international routes last December.
JAL, like ANA, operates P&W PW4000-powered 777s, flying five 777-200s and five -300s. It received its first -300 in July 1998. "We needed a new aircraft for domestic services to replace our [McDonnell Douglas] DC-10-40s and the 747-100s," says JAL.
The airline operates the aircraft with 480-520 seats on its domestic routes - compared with the -200's 389-seat capacity, the DC-10's 318 seats and the 747-100's 568-seat maximum. "Both types of 777 fit our major regional and trunk route needs. The 777-300 in particular fills a niche between the 777-200 and the 747-400D," says the airline.
About 40 JAL engineers were involved with the design programme, in Seattle and Tokyo. In Japan, four groups worked on the flightdeck design, stretch developments and maintenance manual requirements and the application of advanced technology systems. JAL highlights the 777's 15-volume maintenance manual as an example of the effect that operators' input can have. Although the manual runs to almost 15,000 pages, it is a "model of clarity, practical and well-illustrated," says the airline.
Above average reliability
The carrier's 777s are returning an average 6.8h daily utilisation on sectors averaging 1.5h. The fleet operates at a dispatch reliability of 99.5% - above the global average.
"This is almost up to our expectations. However, we look for an improvement in dispatch reliability of between 0.1% and 0.2%," says JAL. The most frequent causes of aircraft unserviceability have been problems with the pneumatic system, electrical power and air conditioning, although other operators say that this does not suggest any inherent flaws.
Both ANA and JAL do their own fleet maintenance, although the Japanese "Big Three" carriers, including -200 operator Japan Air System (JAS), have a joint programme for buying and repairing parts. They share the use of an ANA C-check hangar and engine test cells. JAL says the 777-300 has "better maintainability than other Boeing aircraft", partly because of operator input into access panel design.
According to ANA: "Once you learn about and get used to the size of the huge components, there are no critical issues for the 777 concerning maintainability. One characteristic-is the large and heavy main landing gear with three axles. Since it was the first time that Boeing has introduced such huge landing gear, they conducted in-depth studies to develop a special tool for working on it. We have been working closely with Boeing to improve the maintenance process and minimise the elapsed time for changing the shock strut seal. We think we can manage to do the work within the same elapsed time as for other aircraft."
The airline notes that when changing the engine pre-coolers, the powerplant has to be removed unless a special tool is used. This is "unusual" compared with other types, the airline says, and ANA is considering introducing the Boeing tool for the job.
Engine replacement was initially "challenging" because of the size of the derated P&W PW4090s that power the airline's aircraft, but ANA says it can do the job "almost in the same timeframe as other types of engine installed on other types of aircraft such as the Boeing 767".
JAL describes the aircraft's key strengths as safety, low fuel consumption and easy maintainability. "Of course, a very big factor is fuel efficiency - the 777 uses up to one-third less fuel and it is 40% cheaper to maintain than a 747-400." ANA adds that it is pleased with the cockpit design, and the aircraft "gives passengers a very smooth ride thanks to 'g-force control'".
JAL believes the type overall has "no particular weaknesses", but adds that "the reliability of the electrical system, including the [Hamilton Sundstrand variable-speed constant frequency] back-up generators, is still lower than we expect." The carrier says it has experienced "many back-up generator failures", adding that "the manufacturer's response has been a little slow" in resolving this issue.
A series of back-up generator failures has caused damage to engine gearboxes on some 777s (Flight International, 18-24 August, 1999), and the problem threatened to impose ETOPS restrictions on the aircraft.
Another problem for JAL has been the integrity of flight control wire bundles, the subject of an AD. "Boeing issued a service bulletin to replace some of the bundles, which requires 25h of aeroplane down time," says JAL.
ANA says its dispatch reliability is comparatively high, but adds that "the pressure relief shut-off valve has caused some challenges, but we expect to resolve this problem in the near future." ANA adds that the lack of a humidifier can make the cabin environment slightly dry, but says this is a minor quibble because of the short sector lengths the aircraft is used on.
JAL says there is "nothing exceptional" about the day-to-day maintenance of the engines - a task shared with ANA. Each airline focuses on maintaining different engine modules.
JAL has experienced problems with the PW4000's tendency to suffer compressor stall, but this has not led to any in-flight shut-downs since the 777 was introduced. The carrier adds that P&W is preparing service bulletins to reduce the frequency of engine stalls. ANA adds that it is also "working with the manufacturer to learn more about the compressor stall phenomenon and to address any potential issues".
JAL seems satisfied with the aircraft's flight handling and says that it is easy to handle on the ground, except that its 74m overall length introduces "spot and taxiway limitations". ANA adds that "the steering is slightly different from other aircraft types" because of the 777-300's length, but this simply requires getting used to. Both Japanese operators are pleased with the cockpit's layout and function and flight control system, noting in particular that the cockpit displays are easy to read, reducing pilot fatigue. ANA adds that the computerised checklists are useful and innovative.
According to JAL, the aircraft falls short only in two areas. The engine power is "a little weak" for the weights at which JAL operates - each PW4090 generates up to 91,700lb thrust, while JAL operates at take-off weights up to 237t. ANA operates its 777-300s at weights of up to 234t. Second, JAL adds that brake temperature gets "a little high" during summer, "probably because the wheel size on the landing gear is the same as the 777-200".
JAL says the -300's operating costs are "lower than we expected, based on our studies of the aircraft's economics before we decided to order it - especially in maintenance costs". ANA says operating costs are about 25% lower than those of the 747-400 "largely due to the 777's fuel efficiency".
Singapore Airlines (SIA) is Boeing's largest 777 customer, with orders and options for 61 R-R-powered examples, of which 18 have been delivered. The airline's initial examples were the smaller -200, the first of which was delivered in May 1997. The first -300 arrived in December 1998 and five are in service, with six more to be delivered through to 2001. The -300s are configured with a three-class 332- seat layout and are operated from Singapore on key Asian trunk routes such as Bangkok, Hong Kong, Jakarta and Manila, as well as to Australia (Perth and Melbourne), Japan (Fukuoka and Hiroshima) and the Middle East (Dubai and Cairo).
SIA's experience
SIA says it participated in ground manoeuvrability exercises and provided feedback into the installation of the 777-300's ground manoeuvring cameras. The Singaporean carrier highlights the aircraft's spacious cabin interior, the design of the cockpit and the architecture of the avionics - which it says are "almost similar in feel and instrumentation to a 747-400" - as the 777-300's strengths. It points to ground manoeuvring restrictions on such a long aircraft as a weakness, saying that this causes problems at some airports "such as in Shanghai" when a 180í turn is required on a 150ft-wide runway.
"The aircraft's performance is up to expectations-[although] the cabin noise level is high at the rear end, which is also subject to a 'fishtailing' effect," says SIA. It says improvements are required to reduce the rear cabin noise level and the hum, audible in the cabin, from the electric hydraulics pump in the centre fuselage. Further, the airline highlights the lack of humidifiers as a weakness.
The carrier says the aircraft's fuel economy "has been satisfactory and up to expectations".
As a major derivative of a design which was promoted as "service ready" at introduction, it is no surprise that the operators are generally satisfied with the 777-300's initial performance and reliability. The aircraft's recent sales success has probably not matched Boeing's original target, but this reflects more the Asian downturn and the current trend away from high-capacity aircraft than an underlying fault with the concept. Developing the longer range -300X model is vital, however, if this giant twinjet is to realise its true potential as a 747 successor.
Source: Flight International
