Date: 10 Sep 97 19:38:46
From: kls@ohare.Chicago.COM (Karl Swartz)
Organization: Chicago Software Works, Menlo Park, California
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>After several bad crashes of twin-engine piston airliners in the
>1950s after they lost one engine and burned up the other one trying to
>reach an airport, the FAA (or maybe it was still the CAA) created the
>60-minute rule. Any twin-engine airliner could be no more than 60 minutes
>flying time (on one engine) from a suitable airport at any time during its
>flight.
It actually was an ICAO rule, adhered to by the FAA as well as other
government aviation authorities. It also said nothing about twins --
the rule mandated that an airliner be able to limp to a suitable
airport with one engine out within 60 minutes. The implication for
twins is obvious, but less obvious is that this could also preclude
some operations of three-engined aircraft at high weights. (This may
be why the early variations were called EROPS, for Extended Range
OPerationS, not ETOPS for Extended Twin OPerationS.)
>So the first ETOPS operations were 90 minutes.
While it may not have been called ETOPS, the first such deviation was
for 75 minutes (later 85), granted by the FAA for Carribean flights.
The first ICAO-recognized variation was 90 minutes, though.
>Then 120 minutes, then 150 minutes, and now 180 minutes.
Never heard of 150 minutes. After 120 came 138, which closed a small
"no go" area in the North Atlantic. See details of this at
http://www.chicago.com/airliners/gc-faq.html#etops-138.
--
Karl Swartz |Home kls@chicago.com
|Work kls@netapp.com
|WWW http://www.chicago.com/~kls/
Moderator of sci.aeronautics.airliners -- Unix/network work pays the bills
