Aircraft

Nine airlines have placed orders and options for more than 300 Boeing-developed short-field performance improvement packages for installation on 737-800s and -900ERs, the first of which will enter service later this year.

The package, first launched to enable Brazilian airline GOL to operate the 737-800 into the restricted 1,465m (4,800ft) runway of Rio de Janeiro’s Santos Dumont airport, is aimed at giving -800/900ER operators runway performance similar to that of the shorter-bodied -700. The kit, which will be standard on all -900ERs and optional on the -800, includes a variety of aerodynamic and system changes, and has been undergoing flight tests since mid-February.

© Boeing / Jennifer Henderson

Landing performance tests of the 737-800 with and without winglets were completed at Roswell, New Mexico

“It’s about 60% of the way through flight tests,” says 737 chief project engineer Mike Delaney. “We’ve done drag tests, we have performed stalls, and have done stability and take-off performance tests as well as some of the early autopilot development.”

By early April, the test 737-800 YK721 had accumulated 140h of testing and some 275 flight cycles. “Our plan is to finish flight tests at the end of May,” Delaney adds.

As a result of initial testing, Boeing has decided to withdraw a proposed Krueger flap seal actuation device from the package after “we didn’t get the CLmax [coefficient of lift] benefit we wanted”.

Tests showed only around one-third of the hoped-for performance derived specifically from the Krueger modification and, after a cost-benefit analysis was conducted, the option was dropped. “It just wasn’t worth it, so we have eliminated an actuator and a part,” says Delaney, who adds the overall target is still within reach because “the rest of the package is performing better than expected”.

The “most powerful” part of the remaining package is the two-position tailskid that allows safe use of higher angles of attack and rotation, while others include sealed slats for all take-off flap positions to 25º and increased flight spoiler deflection on the ground to close to that of the ground spoilers, which deflect to 60º.

Landing performance tests with and without winglets were completed recently at Roswell, New Mexico, following earlier test phases at various sites, including Edwards AFB, California, Kona, Hawaii and Moses Lake, Washington. The initial short-field package-equipped 737-800s will be delivered to GOL this year.

GUY NORRIS / LOS ANGELES