Pilot Pete, hi there.
The question was: “In Jar Ops 1, is there a distance limit for the destination alternate from destination aerodrome in terms of time/distance?” My answer is: yes there is, using the mentioned rule JAR-OPS 1.245 Maximum distance from an adequate aerodrome for two-engined aeroplanes without an ETOPS Approval, a time limit is 60 min/ distance for instance A330 is 422 NM, based on speed 330 knots and reference weight of not less then 220 tonnes, one engine out. Everything else beyond, those limits is ETOPS. Regulations regarding the selections of destination airdrome: JAR-OPS 1.295 Selection of aerodromes
(a) An operator shall establish procedures for
the selection of destination and/or alternate
aerodromes in accordance with JAR-OPS 1.220 when
planning a flight.
(c) An operator must select at least one
destination alternate for each IFR flight unless:
(1) Both:
(i) The duration of the planned
flight from take-off to landing does not
exceed 6 hours; and
(ii) Two separate runways are
available and useable at the destination and
the appropriate weather reports or forecasts
for the destination aerodrome, or any
combination thereof, indicate that for the
period from one hour before until one hour
after the expected time of arrival at
destination, the ceiling will be at least 2 000
ft or circling height + 500 ft, whichever is
greater, and the visibility will be at least 5
km. (see IEM OPS 1.295(c)(1)(ii)); or
(d) An operator must select two destination
alternates when:
(1) The appropriate weather reports or
forecasts for the destination, or any combination
thereof, indicate that during a period commencing
1 hour before and ending 1 hour after the
estimated time of arrival, the weather conditions
will be below the applicable planning minima; or
(2) No meteorological information is
available.
(e) An operator shall specify any required
alternate(s) in the operational flight plan.
[Amdt. 3, 01.12.01]
Amendment 7 1-D-7 01.09.04
In other words, whenever your destination is further than 6 hours you need a destination alternate, which has to be usable for planning purposes and adequate for operation. The regulations prescribe the limitation in time and distance based on worst case scenario, which is for TWO ENGINE A/C is one engine out. Those limitations for instance for 3 or 4 engines airplane are two hours. Generally we are not speaking about one engine out diversion as such, but in order to specify criteria for limitation, the authorities prescribe worst case scenario. The same rule applies by the way for departure aerodrome. That’s my way of understanding that could be wrong.
Cheers.