OPERATORS ARE playing down the impact of payload restrictions to be imposed on Boeing 727 freighter conversions under four airworthiness directives (ADs) proposed on 14 July. The ADs, which cover over 300 727s converted from passenger to freighter configuration by third-party modification companies, will require operators to fit strengthened floor beams to prevent possible floor-structure failure.

The US Federal Aviation Administration will also require the maximum payload per cargo container to be reduced from 3,630kg to 1,360kg, within two days of the ADs being finalised in October and until the modifications are made. The 727-100 freighter can accommodate 11 containers, while the longer -200 can take 12, and a total payload of around 19t. Payloads up to 2,180kg per container would be allowed for up to 120 days after a final rule, provided side restraints are used.

The ADs, resulting from concerns that third-party conversions were engineered without Boeing's load-path data, only address the main-deck floor structure. Other modifications will be the subject of a second set of proposals. ADs covering cargo doors, restraint systems, and electrical and hydraulic- design deficiencies are expected.

A total of 32 operators is affected, and the FAA estimates that the modifications for US-registered aircraft alone will cost about $25 million. FedEx is hit hardest, with 120 of its 163 727s possibly requiring modification. DHL has 20 727s, 13 of which are affected. Only seven of UPS' ten 727-200s are believed subject to the limits. Its 51 727-100s are unaffected, as freighters created by Boeing, or using its STC, are not included.

FedEx, which operates half of the 244 US-registered aircraft affected by the ADs, says that more than 90% of the containers used weigh less than the FAA's limits, although it will seek approval for smaller "demi" containers not addressed in the proposed ADs. "We expect to be able to manage any impact of the proposed weight limits," says senior vice-president for air operations, Gilbert Mook.

In Europe, 727 freighter operators such as Hunting Cargo Airlines and TNT Express will be affected. "We should be able to meet the interim side-restraints requirement, which will mean that the AD will not seriously affect our payloads," says David Robinson, TNT's general manager for aircraft development.

"The good news is that the FAA hasn't gone off the deep end like it threatened to, and they're giving responsible operators a chance to fix their aircraft," says Phil Boughton, Air Transport Association vice-president engineering, maintenance and materiel.

"The repairs themselves are straightforward," says Gordon Hamilton, president of Arizona-based Hamilton Aviation, which teamed on the 727 modification effort with Pemco, responsible for converting many of the 727s affected. "What's more complex is the creation of a finite-element model [FEM] that accurately predicts the loads, and we've done that. Using the FEM, we'll do a survey of each individual aircraft then run it through the model and generate a kit for the repair," he says.

Source: Flight International