GRAHAM WARWICK / WASHINGTON DC Two sets of rules seem likely covering airworthiness and operations far from diversions

Airworthiness and operations regulations for aircraft flying far from diversion airfields are about to get two updates.

The US Federal Aviation Administration's rulemaking advisory group has proposed a single regulation for "extended operations" by two-, three- and four-engined aircraft. Boeing believes the regulation as proposed would "level the playing field" for operations involving diversion times beyond 180min with one engine failed. Europe, meanwhile, is planning to maintain a distinction between twinjets and three/four-engined aircraft on operations far from diversions.

The draft notice of proposed rulemaking (NPRM) presented to the FAA by an Aviation Rulemaking Advisory Committee (ARAC) working group codifies existing guidelines for extended twin-engine operations (ETOPS) and extends the rules to cover flights by two-, three- and four-engined aircraft involving diversion times of 240min and beyond.

"All aircraft on extended routes fly in the same operating environment," says the ARAC, recommending "one uniform standard be applied to those operations". This includes the requirement for all operators to establish a plan for recovering passengers and crews from diversions in inhospitable regions. The ARAC's findings will spawn an NPRM expected in 2003, but the FAA indicates that rulemaking will probably take until 2005.

Europe is updating its own rules, meanwhile, and a notice of proposed amendment is planned for October. Despite the fact that Joint Aviation Authorities representatives were on the ARAC, JAA certification director Yves Morier says it is certain that there will be considerable differences in the two sets of rules. Under the ARAC proposal, ETOPS would apply to twinjet airline operations with diversion times over 60min, as now, but beyond 180min the rules would not depend on the number of engines but the onboard equipment specification, and they would also apply to FAR Part 135 on-demand operations. The JAA's LROPS upgraded requirements would apply to three- and four-engine aircraft and business jets flying beyond 180min diversion time, but ETOPS limits are expected to apply to commercial airline twins.

Airbus and Boeing believe the European and US requirements are similar for hardware, with the differences mainly operational. Boeing is keen to eliminate any disadvantage for the twin-engined 777 against the four-engined A340, and Airbus is keen to maintain the twin/quad distinction.

The JAA demands a fourth electrical generator for LROPS, while ARAC insists on useable diversions in polar areas regardless of the aircraft's approved one-engine-failed diversion time; ETOPS-level engine maintenance of trijets and quads; and would apply US Part 121 rules requiring a diversion if an engine fails even if the aircraft has four engines. Beyond 180min, the allowable engine inflight shut-down rate will be halved to 0.01/1,000h - a level that Boeing claims the 777 meets today.

Source: Flight International