Boeing's 777-300 reliability figures are the best for a widebody introduction

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Boeing's 777-300 reliability figures are the best for a widebody introduction

Guy Norris/LOS ANGELES Max Kingsley-Jones/LONDON

Boeing says its experience with the introduction of the 777-300 has been a case of "no news is good news". Mike Fleming, Boeing's 777 fleet support chief, says: "In terms of performance in service, it's been remarkably quiet, which is really an indication of its success. The airlines just wanted a 'carry more people' aircraft, and it appears that is what they have."

Although a relatively small fleet, particularly in Boeing terms, the 777-300's reliability figures stand out as the most successful of any new twin-aisle airliner on entry into service: scheduled reliability of a 12-month rolling average stands at 99.3%, while the three-month rolling average is 99.46%. "It is certainly the highest reliability of any widebody, but the key is sustained reliability. Anyone can have a 99% month now and then, but keeping it at that level or higher is the difference. If anything, it seems to be trending up slightly," says Fleming.

Since the first aircraft entered service with Cathay Pacific in May 1998, only once has any three-month rolling average dipped below 99%, to 98.7%. "We are satisfied with this rate, although we are not stopping," says Fleming. He adds that the company has a goal of keeping scheduled reliability of the 777-200/300 family as a whole at 99%. "We just have to keep working at it."

Among the potential in-service issues for which Boeing braced itself with the -300 was the ground manoeuvring capability of the aircraft - the longest airliner ever produced. Even here, Boeing says, there have been "no issues". The ground manoeuvre camera system, installed to help crews negotiate turns on taxiways and ramps, "is working and has not been a problem", says Fleming. Apparently, the only issues that have surfaced are those encountered by the 777 fleet as a whole, including recent troubles with the Hamilton Standard variable-speed constant-frequency generator system, fitted to all makes and models of the engines that power all 777s.

Turnaround times, another potential issue, have been "slightly longer in general", says Fleming, who believes this to be due largely to the shorter routes, and denser intra-Asian route network on which the 777-300 is predominantly used. Overall, average use of the -300 is 7.5-8h a day, versus 10-10.5h for the -200. "When you factor that in, no operator has reported having difficulty in turnaround times relative to the -200," Fleming says.

By the start of this year, Boeing had delivered 31 -300s to seven operators. Total fleet hours reached 68,737 by 31 December, and were expected to have passed 70,000h as this article was prepared. Another two -300s are to be delivered this year, including one to Korean Air and another to Emirates - the only non-Asia-based operator of the type.

Fleming attributes the -300's overall service reliability to the pathfinding "lessons learned" on the -200, and the philosophy of the simple stretch that underlined the larger model's development. "It really is a tribute to the baseline aircraft and the fact that it essentially entered service as a mature aircraft. We did not have to change much in the way of systems, and this is the result," he adds.

The aircraft also appears to be robust in terms of the effect of updates and in-service modifications such as the Honeywell-developed AIMS-99 (aircraft information management system) improved software load. This was introduced at the end of last year and, "so far, we have not had any reports of problems", he adds.

Although the Rolls-Royce Trent 800 was the last engine to be certificated on the baseline 777-200, the R-R powered -300 was the first version of the new model to enter service, with Cathay Pacific in May 1998.

The aircraft is offered with the 90,000-92,000lb-thrust (400-410kN) Trent 890/892, and the engine has been specified by four of the seven 777-300 operators, including Cathay, Emirates, Singapore Airlines, and Thai International. The engine is common to both the 777-200 and -300.

Eighteen Trent-powered 777-300s were in service by the end of January, with the fleet having accumulated 26,376 cycles, with dispatch reliability running at 99.897%. The latter figure represents six engine-related delays, says the manufacturer.

The company says the engine has recorded zero in-flight shutdowns on the 777-300. No unscheduled engine removals or aborted take-offs since the aircraft's introduction have been reported.

Having put the 92,000lb-thrust PW4090 into operation with 777-300s All Nippon Airways (ANA) and Japan Airlines (JAL) in 1998, Pratt & Whitney developed the more powerful 98,000lb-thrust PW4098 for the -300.

This powerplant, which is the most powerful engine yet put into service on the 777, suffered most of its problems well before its entry into service last August with Korean Air (KAL).

The 10 PW4090-powered 777-300s in service with JAL and ANA since mid-1998 have been reliable, says P&W, which reports an in-flight shutdown (IFSD) rate of zero for the fleet.

More PW4090s are in service with the -200s, and some problems have resulted in removals and shutdowns with their 113 engines.

Dispatch reliability for the PW4090 fleet as a whole, including the -300s, is 99.93%, while unscheduled engine removal rate is 0.26% and shop visit rate 0.030%. The IFSD rate stands at 0.007%, while total engine time was 592,000h by the start of February.

The engine maker encountered severe development issues with the high thrust PW4098 version, which subsequently slipped behind schedule by almost a year.

P&W PW4098 model manager John Danielson reports, however, that the limited fleet of three PW4098-powered 777-300s in service with KAL has proved to be dependable in service, with a dispatch reliability of 100%. Unscheduled engine removals and IFSD rates are therefore at zero.