Guy Norris/LOS ANGELES
Early results from the Boeing 717-200 flight test effort are indicating "nominal or better" drag and specific fuel consumption (sfc) performance, leading to expectations that the baseline range and payload may be increased, says the company.
The build-up of 717 test hours and sorties is accelerating with the arrival of the second aircraft (T-2), which joined the first 717 at Yuma, Arizona, on 26 October. T-2 is being used to develop the advanced common flightdeck systems, autoflight and Category III automatic landing systems.
"We have been pleasantly surprised with some of the results," says director of 717 test and validation Michael Delaney. "We have lower than expected weight and good drag, and the BMW Rolls-Royce BR715 engine has been showing good thrust SFC results," he adds.
The early results coincide with the completion of pivotal stall tests, which began on 28 October and included over 200 stall manoeuvres. Most of these will be repeated, starting from 20 November, when the initial phase of the concurrent co-operative certification initiative gets under way. Under this scheme, the 717 will become the first airliner to be authorised under a single certification basis after just one regulatory validation demonstration, combining US Federal Aviation Administration and European Joint Aviation Authorities approval.
To date, the first 717 - the performance and envelope expansion aircraft - has reached Mach 0.8 at a maximum altitude of 35,000ft (10,600m). It has reached Vd speed (maximum dynamic pressure) of 400kt (740km/h) at 11,000ft. Maximum take-off weight (MTOW) achieved so far has been 57,200kg (126,000lb) - 2,270kg over weight - to allow heavyweight stall speed to be assessed "on station" at close to standard MTOW.
Climb and take-off performance tests are about to start, including further tests of the anti-skid braking system, which has been modified with new energy-absorbing linings after earlier problems.
Other hitches with the spoiler control, which was modified before flight tests began to eliminate any chance of inadvertent in-flight deployment, have been solved, says Boeing. The modification, completed by early October, solved a "spoiler float issue", which cropped up when flaps were set at the 50¼ landing position.
By 5 November, the two test aircraft had amassed more than 140h between them on almost 80 test flights. Testing with four aircraft is due to be completed next June.
Source: Flight International
