Guy Norris/Seattle
Load tests on winglets for the Boeing Business Jet (BBJ) are due to begin this month. Boeing believes that the addition of winglets could result in a 5% improvement in performance on the long-range corporate jet.
A BBJ prototype is being instrumented for the trials. If successful, the winglets will be standard from late 2000.
The tests will help determine the extent of structural strengthening required for the outboard wing section that supports the 2.3m (7ft)-tall winglet.
A separate modification kit is also being developed as a retrofit for BBJs which have already been delivered with the standard wing. Seattle-based Aviation Partners, designer of the blended winglet, is obtaining the supplemental type certificate (STC) for the kit and will manage the retrofit.
To meet demand for more engine performance to reduce field length, the BBJ will also be offered with the highest-thrust CFM56-7B27 option. This raises take-off thrust to 27,300lb (121.4kN) versus the 26,400lb of the current engine. "Everyone wants more thrust," says BBJ president Borge Boeskov, who adds that the extra 900lb thrust per engine "-will lower field length and will really increase range on a hot day".
The bulk of the price rise pays for the winglets, which bring a 5% range increase - 160km (300nm) - or 5% more fuel. With the wing strengthening, adding winglets adds around 230kg (500lb) to the overall weight of the aircraft.
Meanwhile, the company is re-shuffling its delivery sequence following delays over certification of the auxiliary fuel tank system. Problems have been caused by software issues with the flight management system computers that integrate the fuel calculations for the main and auxiliary fuel systems.
The tanks have been designed by Maryland-based PATS, with installation work undertaken at the company's Georgetown site in Delaware. PATS, recently acquired by Decrane Aircraft Holdings, has a seven year, $180 million, contract to install them.
"It's created a bit of a bottleneck for us," admits Boeskov, who says that the plan is to fly completed airframes from Renton to the completion centres. PATS will then send a team to install the tanks on-site. In the meantime, BBJs already fitted with the tanks have been provisionally certificated, with the tanks non-useable. "We expect to get an STC on the tank system about mid-March," he adds.
By early February, 10 BBJs had been delivered, three of which are at PATS, with the rest at various completion centres. In all, 29 BBJs are due to be handed over in 1999, rising to 37 by year-end. Total firm sales stand at 46.
Source: Flight International
