GATX-Airlog is preparing to "re-enter" the Boeing 747 freighter conversion market after the USFederal Aviation Administration approved company-developed service bulletins (SBs) which will finally allow operators to revive the prospects of several grounded 747Fs.

The event marks a major breakthrough for Airlog, which has been fighting to clear modifications to 747s converted using its supplemental type certificates since they were effectively grounded by the FAA more than two years ago.

The FAA has approved an initial batch of 12 SBs which, once performed, will allow affected operators to raise weight restrictions to levels that would permit economically viable operations.

Under restrictions imposed in the original airworthiness directive issued by the FAA in January 1996, total payload was reduced to 54,500kg, or almost half the normal 100,000kg payload.

The initial SBs will allow "-operators to enjoy more payload, but will still suffer versus the original freighter," concedes GATX-Airlog president Rick Hatton. A further four SBs are close to completion, however, which Airlog says will allow the restrictions to be lifted completely. "There are no guarantees yet, but I'm certain as I can be that there are no technical risks left," he says.

The initial SBs cover "all but one of the five points agreed with the FAA" says Hatton. They include all door surround modifications, clearance of floor beams, validation of structural changes, stiffening in the front body, removal of beams and configuring the aircraft to meet standards devised using a finite element structural analysis model developed by Israel Aircraft Industries.

The subsequent SBs will focus on frame stiffeners to strengthen the area where vertical posts intersect with circumferential frames carrying loads around the fuselage. Modifications have already been started on four of the 10 aircraft affected. Evergreen is expected to have its first aircraft flying as soon as July, says Hatton.

Source: Flight International