The US Federal Aviation Administration is giving affected cargo carriers a final chance to express their views on four proposed airworthiness directives (ADs) that would severely limit the payloads of Boeing 727 freighters converted by third party maintenance organisations.

The FAA has scheduled public meetings in Seattle on February 18-19 and April 1-3 in an effort to gather more data to resolve conflicts between operators and the safety agency over the ADs.

More than 30 operators would be affected, with FedEx one of the worst hit - up to 120 of its 163 727s would require modification. Most operators have played down the impact of the proposed ADs, but have questioned how the FAA arrived at the weight limits.

The agency will decide on the cargo floor loading issues this year. The FAA expects the meetings to resolve the methodology and technical assumptions used in calculating allowable loads on the floor structure of modified aircraft.

Inspections and subsequent analysis by the FAA of modified floor structures using the so-called non-original equipment manufacturer conversions raised concerns that the support structures may not be strong enough to allow the aircraft to carry safely the present maximum payload.

The ADs proposed in July 1997 cover 300 aircraft not converted using Boeing's supplemental type certificate, including 244 registered in the USA. If adopted, the directives would require strengthened floor beams on aircraft modified by third parties, including Pemco, FedEx Aviation Services and Aeronautical Engineers.

The ADs are designed to prevent the possibility of floor structure failure on the converted aircraft, pending corrective modifications. The 727-100 can hold 11 cargo containers and the larger -200 can carry 12.

The ADs would require operators to reduce payloads from 3,632kg to 1,360kg per container until the modifications are made. Payloads up to 2,180kg per container would be allowed if side constraints were used.

Source: Flight International