Pratt & Whitney remains on track to secure certification of its GTF Advantage version of the PW1100G geared-fan engine in the first half of 2025, after being granted US relief from strict compliance with certain go-around thrust requirements.
The powerplant is being developed for the long-range Airbus A321XLR and other models in the single-aisle family.
Pratt & Whitney says it expects deliveries of the engines to begin “in the back half of the year”.
The engines feature updates which reduce thrust for go-around operations, but the manufacturer acknowledges that an “unintended consequence” of this modification is an inability to comply strictly with thrust requirements following a bird-strike.
US Federal Aviation Administration (FAA) rules require engines to deliver a specific level of go-around thrust after a bird-strike. But with the maximum allowable bird-strike damage, the GTF Advantage does not meet the requirement to deliver 75% maximum thrust if the aircraft has commanded the lower go-around thrust setting.
The engine manufacturer formally sought exemption from this regulation in September.
According to the exemption request filing, Airbus has stated that the relevant aircraft models will comply with European certification requirements for rate-of-climb.
The filing points out that, for the aircraft to demonstrate this steady-climb gradient, the engine must perform at a sufficient thrust level.
Pratt & Whitney argues that, by meeting this aircraft-level thrust requirement, the engines must be exceeding the level of safety intended by the bird-strike regulation.
The European Union Aviation Safety Agency (EASA) has remarked that the reduction in go-around thrust should be addressed “only during the certification of the aircraft”, rather than the engine, and “not be accounted for” when considering bird-strike rule compliance.
But while the FAA, in a 27 November ruling, says EASA’s view has “technical logic”, it adds that the software programming for the full-authority digital engine control “nevertheless remains part of the engine type design” – and that an exemption is necessary for certification.
The FAA nonetheless says Pratt & Whitney has shown that – under a one-engine inoperative scenario – the loss of thrust would still permit the aircraft to meet minimum climb gradients.
As a result, it has granted the exemption on the basis that it “would not adversely affect safety” even though the engine will not directly comply with the bird-strike thrust requirement.
