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air safety

Feb 21, 2013


Taking forward the US reports of the hour of a 787 fix to its battery problems being formally offered to the FAA on Friday US time, what would its acceptance by the safety regulator do to the Dreamliner’s previous approval to fly a long way from emergency airfields while making oceanic or polar flights?

This would be a crucial question for all of the early customers hit by the January grounding, as JAL, ANA, United, Air-India and LOT Polish all want to fly the jet under so called ETOPS rules for up to 180 minutes single engine speed distance from such alternative landing sites.

But ETOPS approvals, which are required by all twin engined jets if they are to operate efficiently over oceans, deserts and frozen arctic wastes, are very strict about engine and electrical systems reliability, and even if the FAA allows the 787s back in air using an ‘interim’ fix to its battery problems, there are real concerns that discovering and permanently fixing the cause of the January battery crises on a JAL and ANA 787 will be a lengthy process.

While all modern twin engined jets are built to ETOPS standards, airlines can only use them if they have the approval of their national safety regulators and those approvals are conditional on such things as preventing the same maintenance team being responsible for both engines, so that any systemic mistakes aren’t made on both engines by the same engineers.

ETOPS 180, the industry standard, is theoretically needed even to fly as straight a path as possible across some parts of the Australian interior where jet fields are few and far between.

Boeing has long pushed the capability of the 787 to do ETOPS 330, that is, to be as far from an alternative field as it would take to reach it in 330 minutes on one engine, even though no airline is known to be using ETOPS 330 for any scheduled service today in any twin engined airliner.

The rules require a twin engined jet to land at the first available airport in the event of one engine failing or having to be idled. There are several motivations for this being a matter of urgency, unlike the case where an airliner has three or four engines.

One urgent reason is that if the cause of the first engine failure is going to affect the other engine, landing as soon as possible reduces the risks of that happening.

Another is that a twin engined jet flying on only one engine cannot sustain a high cruising altitude, and its forced descent to a sustainable altitude may infringe the safe minimum height rules over very high mountains, will adversely impact the fuel consumption of the remaining engine , and can result in the jet being at altitudes where its anti-icing system is called on to deliver maximum performance but with reduced bleed air or electrical systems capacity.

The complications are very well known and planned for by airlines using big twin engined jets, but the efficiency and reliability of such airliners as the 777 and A330 is such that emergencies like this are extremely rare, and mitigated by the strict ETOPS rules that apply to them.

But, those questions of engine and electrical system reliability will come back to the fore in the case of the 787, no matter whether an immediate temporary fix is approved, or when a permanent fix is devised and applied.

For Qantas which plans to use its first 787-8s under the Jetstar brand, ETOPS 180 is an essential prerequisite for efficient operations.


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