I thought a recent flight from Perth to Mauritius provided a great basis to highlight the impact of ETOPS restrictions on airline operations in the Southern Hemisphere.

There is no trans-polar or oceanic route in the Northern Hemisphere that requires more than ETOPS 240 approval (four hours from flying time from a suitable airfield), and more than 90% of routes require no more than ETOPS 180.

ETOPS speed schedules are designed assuming a MTOW at departure with highest gross weight and enroute weather conditions at critical points enroute determining diversion speed and endurance. Speeds vary by operator, and other factors including carriage of additional passenger oxygen allowing operations at an intermediate level above FL140 are also taken into account.

Down south ETOPS restrictions have arguably a much greater operational impact as this Perth – Mauritius sector highlights.

Air Mauritius’ previous A340 operation to Australia tracked along a flight path relatively close to the great circle routing (see map below). Now operated by its A330-200 fleet – approved for ETOPS 180 (for arguments sake roughly 1,000nm) – the aircraft must track significantly to the north of the great circle route. Flying north-west after departing Perth to remain within diversion flying time of Learmonth, the Cocos Islands and then Diego Garcia, before tracking to the south-west for Mauritius.

The result is a longer flight time – the previous 8:30 minute block time westbound, is now an 8:30 minute flight time – approximately 45 minutes to one hour longer airborne.

The associated impact on flight economics is substantial as Virgin Australia learnt the hard way in its brief foray into Boeing 777-300ER operations between Melbourne and Johannesburg. To remain with ETOPS 180 restrictions the 777 operated a more northerly, inefficient routing – maps of westbound and eastbound flights – resulting in a flight time 1:15 longer than Qantas’ 14 hour Sydney – Johannesburg service.

The lightest grey shade on the map indicates ETOPS 180 limits. If Air Mauritius were to gain approval for ETOPS 207 or even 240 it would allow a more efficient southerly routing. But would you really be comfortable knowing you are that far from land on the off chance your Royce does stop Rolling.