The ETOPS Extended-range Twin-engine Operational Performance Standards or EXTENDED RANGE OPERATIONS (EROPS). A two-engine aeroplane obviously loses 50% of its available power whenever there is an engine shutdown in flight. Further, with only one engine operating, safety margins are much reduced since if the other engine should fail than an accident is almost inevitable. One of most known ETOP aircraft is Boeing 777 ER or 77W
With the very good reliability of modern turbine engines it has become possible to approve transoceanic flights with certain two-engine aeroplanes without compromising safety requirements. Three levels of approval can be given to a particular aeroplane type with each level being designated by:
the time in flight which a twin engine aeroplane might be from a suitable emergency airfield at normal single engine cruise speed.
The levels are 60 minute, 120 minutes and 180 minutes.
Historically such approvals have only been given after considerable time in service when sufficient evidence of reliability has been achieved. Experiences of granting and monitoring such approvals, advances in reliability and proven MSG procedures have led to the situation where up to 120 minutes ETPOS approval can be given for a new type in-service evidence.
Initially the onus is on the design of the aircraft with engine reliability, adequate redundancy, alternative electrical supplies, a more restrictive MEL(Minimum equipment list), etc. being given due attention.
A maintenance programme for aeroplanes used for an ETOPS operation will be based on the same maintenance programme as for aeroplanes used for other operations. The programme will, however, be enhanced and amended to ensure that the operations are safe. Procedures will prevent identical action being taken on the same item on both engines, for example a fuel control unit change on each engine. Maintenance personnel must be aware of the special nature of ETOPS and qualified persons used to sign for checks identified as being significant for ETOPS.
