Despite strong schedule uncertainty with Boeing's 747-8 freighter, the airframer continues to press on with assembly of its first -8I passenger aircraft.

Boeing now says a "very high probability" exists that first deliveries of the new jumbo freighter to Cargolux will slip into 2011, but an official shift in the schedule has yet to be announced.

The compounded effect of three issues have virtually eliminated any remaining margin in the aircraft's flight test schedule, with two of the three outstanding.

The first, now solved, was a "very apparent" vibration in the outboard landing gear door when the aircraft's flaps were at the 30 setting. The second and third, an oscillation in the aircraft's inboard aileron caused by an under-performing actuator, as well as a structural flutter at mid-weight just below cruise, are slowing the flight test campaign considerably.

Meanwhile, the 747-8F test fleet has completed 740h over more than 270 flights. RC501, which just emerged from a week of planned maintenance following stability and control testing, is now pressing forward with wing twist evaluations.

RC521 was ferried to Colorado Springs, Colorado on 20 August for high altitude ground testing of the aircraft's engines and auxiliary power unit.

RC522 is currently undergoing community noise testing in Glasgow, Montana while RC503, the newest member of the flight test fleet, is performing High Intensity Radiated Fields (HIRF) evaluations in Palmdale, California.

As these issues slow the certification of the freighter variant of the jumbo, Boeing is continuing to press forward with assembly operations for its first 747-8I flight test aircraft, RC001.

While Boeing achieved 100% design release for the 747-8I in late June, the airframer intends to incorporate design changes honed on the -8F into the -8I during assembly, including the revised outboard landing gear door and strengthened inboard aileron actuator.

Any changes developed for the 747-8F to resolve the structural vibration may not be required for the -8I and its stretched upper deck, though early flight tests will work to clear RC001 of any structural flutter.

The company is planning for a shorter flight test programme than the 1,600h campaign being undertaken by the 747-8F, as aerodynamic data from the freighter is expected to be carried over to the passenger variant.

Boeing aims to begin final body join on RC001 in late September or October, and is currently joining the forward fuselage sections 41 and 42 that make up the jumbo's iconic hump, inside the 40-23 building at the company's Everett, Washington facility. 

Additionally, the company is building up fuselage section 46, which abuts the aircraft's centre wing box and bonnet section 44. Boeing is also nearing the stub join that will see the aircraft's wings mated to the centre wing box.

Boeing expects to roll out RC001, the first of two flight test aircraft, in January 2011 with first flight to follow later in the first quarter. First delivery, which will be in VIP configuration, is expected in the fourth quarter of 2011 when the aircraft is handed over to a completion centre. Lufthansa expects its first 747-8I in early 2012.

Source: Air Transport Intelligence news