Although still a relatively small fleet by Boeing standards, the 757-300 has achieved, and sustained, high scheduled reliability levels from virtually the start of operations in early 1999. The first seven aircraft, all in service with Condor, achieved an unprecedented 100% monthly scheduled reliability three times between June 1999 and January 2000. Not since April 1999 has the fleet figure dipped below 99%, with the average running at around 99.4% for the 41-strong fleet in March 2003.
"The 757-300 has around 71% parts commonality with the -200," says Boeing's 757 fleet support chief Sue Evans. Problems are quickly dealt with through Boeing's fleet team resolution process, a web-based interactive system with sites for each model.
"Airlines can post any problems they're having and other airlines can say 'yes, we've had that and this is what we did,' or we can say we can do something about that," says Evans, who partly attributes the early high sustained reliability levels to the interactivity of the system. "All of the operators fly the -200, and most of them have had a very easy introduction because of their familiarity with the -200."
One of the main concerns before service experience was the effect of the longer cabin on turnaround time. Although studies at Condor showed its operation could be regularly achieved in as little as 53min, the average is "around 10-15min greater turn time on the -300 than the -200," Evans says.
Variations depend on the use of door one, or two, or both, interior configurations, ground support differences and the type of route and passenger load. "Different carry-on requirements have a big effect," she adds.
Service anomalies experienced on the 757-300 to date include "a couple" of tyre blowouts on the main gear, says Evans. The tyres were constructed to new double overload requirements in which, if one tyre was lost on take-off or landing, the others were required to pick up the load. "If they were not properly maintained, they would develop leaks at an earlier stage than the -200's. We did eventually have a couple of blowouts before Michelin re-certificated a revised design, and we have had no problems since," she says.
Another unusual issue, and one which Boeing "never completely resolved", concerned pitting of the paintwork right down to the skin under the belly. "It was just one customer, and we even put accelerometers in the aircraft to try and find out where and when it might be happening," says Evans. Boeing believes the phenomenon could be related to destinations where volcanic ash was prevalent, and fixed it by adding a few more millimetres of paint.
From a powerplant perspective, the 757-300 has the same offerings as the -200 - the Rolls-Royce RB211-535E4B and the Pratt & Whitney PW2040/PW2043.
The R-R engine was the lead powerplant, and is configured with the low- emissions Phase 5 combustor that is now standard on all new production -535s. "We've got around 180 Phase 5-equipped engines out there, about 40% of them on the -300," says RB211 product marketing manager Clive Crocker. Related changes to the fuel system also differentiate the engine from the earlier marques found on the -200, and include revised fuel flow governor pumps and bleed valve scheduling unit.
Crocker says: "In terms of reliability we don't split between the -200 and -300 fleets on the E4- and E4B-rated engine. From the engine perspective, the reliability seems to be very good. Condor, for example, went the first year without any engine-related cancellations."
Average time to first shop visit on the -535E4 in general has now reached more than 20,000h, while the family recently passed the 30 million flight hour milestone.
The introduction of the Phase 5 combustor has, however, unearthed issues with igniter plug life. The two Phase 5 combustor igniter plugs are located in a hotter section of the combustor than the previous Phase 2 design. A higher heat resistant igniter was chosen for the Phase 5 design, "but unfortunately the material has a worse spark erosion rate, particularly when operating continuously with the engine running. The igniters are set at continuous upon selection of flaps for anti-icing on etc, and it is this continuous operation which is really reducing the life of the igniter," says Crocker. As a result, igniters are being replaced at
continued on p31the A check (500h). "Although most could go on to double this interval it is not worth the risk of having an igniter fail," says Crocker, adding that the result is roughly half the life of the previous Phase 2 igniter design.
"We have looked at redesigns which could increase the cost, so we are not pursuing this currently. We are also attempting to improve lives by operational considerations - reminding crews not to select flaps too early when leaving the gate, for instance."
The first PW2040-powered 757-300 entered service with Northwest in July 2002, and has since been followed by a further eight siblings. To date the fleet (of 21 engines) has accumulated more than 16,400h over 6,300 cycles and has been "the most flawless entry into service of any aircraft-engine combination they've ever had", says PW2000 model manager Bill Boyes.
The engine maker adds, however, that one engine has been removed because of a "manufacturing issue", in particular tight clearances between the variable vane unit and the case. The engine followed a smooth flight test programme from February to May 2002, culminating in certification to the 43,000lb (190kN) thrust level in June. Northwest, however, elected to use the 40,000lb rating on the PW2000 engine.
Source: Flight International
