- why would you want to?

If I'm 180-minute EDTO approved, and I have an engine failure right at the ETP, which is exactly 180 minutes from my selected alternates, am I actually required to fly the company’s OEI diversion speed (say .85/340) to remain within the approved 180-minute limit?

The reason I ask is that our operations manual specifically states that the OEI diversion speed is used both to define the area of operation (i.e. max diversion distance) and for “conducting the diversion following an engine failure.”

It’s very rare for the ETP to be exactly 180mins from both airfields. Over the North Atlantic there’s always lots of overlap so you will always have extra fuel even at the ETP. Only the route to the Caribbean have I ever seen extra fuel loaded in order to meet ETOPS requirements. You also have 15mins holding on arrival at the diversion. So you won’t run out of fuel!

No, the ‘fixed speed’ is just used to define the area of ops and the fuel planning requirements. If things all go wrong in reality, then you can fly however you need to, according to the circumstances.

ok, but based on the example I mentioned, wouldn't it make sense to use the approved OEI speed (which is also the same company speed shown in the FMC) to ensure I reach the alternate as quickly as possible, and try to remain within the 180-minute EDTO limit?

If I choose to fly at a slower speed, I might even risk exceeding the cargo fire suppression

Doubtful. Remember, the faster you go, the more drag, the greater the fuel burn. Likewise with lower altitudes. Different operators might use different speeds for the same type of aircraft. When computing ETPs, dispatch doesn’t have to include time and fuel for the turn or decent, nor APU operation. Use your FMC fuel calculations to the fullest extent. Sometimes dispatch planning can overlap “over water, extended overwater, flag and/or ETOPS” requirements, resulting in “re-releases.”

Fire suppression for every aircraft must be rated to exceed the Area of Operation, e.g. 195 minutes for 180 minute approval.

Some companies grant captains greater authority and latitude than others.

thanks for the response. Isn’t the EDTO fuel calculation at the ETP (CP) based on the OEI-approved diversion speed? (the same speed used to define the EDTO area of operation)

In our Ops Manual, this speed is referred to as the “Company Speed” or “OEI Approved Speed”, and we even see it on the FMC > VNAV E.OUT > COSPD prompt. That makes me think it’s more than just a planning tool.

My point is: I’m not totally convinced this speed is only for planning.

My regulator very helpfully expanded on this. The bolding is my emphasis.

If minimum diversion time and getting the aeroplane on the ground as soon as possible are the most critical considerations, a high one-engine inoperative speed strategy may be selected, as permitted by the aeroplane’s fuel state, altitude capability and structural integrity. For two- engine aeroplanes, the time strategy is sometimes considered to be equivalent to the approved one engine inoperative speed, but a higher speed approaching VMO/MMO could be selected if conditions warrant. The flight crew is not bound by the speed assumptions used for EDTO flight preparation purposes.

thanks, this is indeed helpful. Do you happen to have a reference or document where your regulator explained this? I’d be really interested to read more. You can share in a PM id you wish. Cheers!