Ever wondered how far from the next airport an airplane can go?
Technically: as far as fuel on board permits.
Legally: 60 mins at 1 engine inop speed – if it’s a twinjet.
The logic behind that restriction of course is safety: 2 engines – 1 fails – no more redundancy; so you’d better have an airport in reach.
Not a big issue if flying across US or Europe: so packed with “ADEQUATE” aerodromes (i.e. AD providing all required facilities to allow for a safe landing) that the 60 min radii around’em overlap (image A).
But then, how come so many twinjets cross the NAT and its large gaps between the few available airports?
One magic word: “ETOPS” – defined in 1985 by @icao as “Extended Twin OPerationS” (or snarky: “Engines turn or passengers swim”).
Its requirements target enhancing operational safety in twin-engine ops (e.g. by plane/engine design, airline & maintenance processes) – if fulfilled, approval is given for diversion times >60 mins even with a twin.
Consequently, special provisions apply also for ETOPS #flightplanning.
My ATL-FRA flight was operated by a beautiful Airbus #a330 approved ETOPS 180 min at my company. So apart from the “normal” #flightplan stuff, I performed the following steps.
- close look at HIL (hold item list) – ETOPS requires double and triple redundancy for several systems (and all need to be operative prior DEP).
- check for “adequate” airports along route. curfews ok, approaches / RWYs available, NOTAMs, Rescue/firefighting category meeting the requirements etc..? E.g. BGSF is closed at night – so there‘s a gap in the „adequates“ over Greenland.
- select ETOPS alternates. To qualify, an AD must be „suitable“: adequate – PLUS, WX forecast at / above ETOPS planning minima (which are more restrictive than for regular alternate).
Winter is coming ❄️😱 – and the AD’s closest to route and Atlantic coast were “unsuitable” or close to. So I had to move further inland both sides of the pond to EIDW and CYJT (obviously increasing diversion times) – which is why I added LPLA on the Azores.
- ETOPS OFP calculation I.e. assuming a „worst case“ scenario with pressurization failure at the most critical point, resulting emergency descent to FL100 and diversion to an ETOPS Alternate – with both engines turning (“DC case”), and with one engine inop (“DX case”). We determine extry/exit/duration of the ETOPS flight portion, the most critical point, ETP(s) (equal time points between returning and continuing). Then, we compare the fuel required for DC and DX with expected remaining fuel from our „normal“ OFP – and if required, pack in ETOPS Additional fuel. (My ATL flight did not use the full 3 hours diversion time, nor did it require ADDFUEL.)
- file the FPL – including the ETOPS alternates – to ATC and generate briefing package for the #pilot(s).