Ramon Lopez/WASHINGTON DC
THE US FEDERAL Aviation Administration admits that it has made a mistake in approving modifications by GATX Airlog, which turned ten Boeing 747 passenger aircraft into freighters, and it has proposed an airworthiness directive (AD) severely restricting cargo weights.
The FAA is seeking comments from affected cargo air carriers and GATX Airlog before imposing the weight restrictions, pending planned modifications to correct unsafe conditions.
The ten 747-100Fs and 747-200Fs are operated by American International Airways, Evergreen International, Polar Air Cargo and Tower Air. The affected cargo carriers have until 4 March to suggest alternatives to the restrictions outlined in the AD, published on 3 January in the Federal Register.
After determining that the main-deck floor and the structure, which surrounds the main deck side cargo door, are inadequate the FAA says, that it can not delay issuing the proposed AD as requested by GATX Airlog.
The aircraft refurbishment-company had sought to hold up the rule-making action, until a corrective modification had been developed, designed and approved. The FAA has ruled, however, that delaying the AD "...will be inappropriate since the level of risk associated with these unsafe conditions, including the potential for total loss of the aircraft, is so great that a delay cannot be justified".
In effect, the AD would limit payload to 54,480kg, from a maximum of 99,880kg, pending aircraft floor and fuselage strengthening.
The FAA says that the affected operators have indicated that they will remove the ten aircraft from service by 31 January.
Since 1988, the aviation agency has approved several supplemental type certificates (STCs) allowing aging 747-100/200 passenger aircraft to be converted into freighters.
The first STC allowed addition of a main-deck side cargo-door on the 747-100. The second STC further modified the aircraft by adding a cargo floor. In 1994, the FAA allowed GATX Air-log to convert 747-200s from a passenger configuration to a special freighter configuration.
The FAA now says that the STCs approved by the Atlanta Aircraft Certification Office were "...based on an incorrect finding that the design was identical to the previous FAA-approved modification of the Model 747 special freighter".
The ten modified 747s, have logged more than 83,000h without incident, and two of them, have survived traumatic incidents. In one case, an Evergreen aircraft lost an engine when it encountered severe turbulence while leaving Anchorage. The modifications, which concern the FAA, were not involved, however.
Source: Flight International
