etops

[longreach777]

hey there .....could someone please explain as to why the 180 mins etops range on the 777 varies from 415nm to 811nm and 1206nm with every 60 mins shouldnt it be in multiples of 415 as is the case in other twin engines

[airseb]

my guess (and that's all it is) is that when you've had your failure (I think it's calculated at MTOW) your single-engine FL will be lower than the one you'll have an hour later and lower still than the one two hours after.

so even on one engine you'll have (normally) climbed after one hour and higher after two.

so your airspeed will have changed and so the disrtance will not be just simply three times 415 kts.

hope it's clear (and that it's right)

seb

[clevlandHD]

The operator will present his request to the local CAA with a scenario. It could be a multiple of distance or; the first hour is a bit longer because you initialy have a better TAS (you are descending from a higher altitude) and then you add multiple from the distance at the driftdown altitude(fix). All these are made with an assumed average weight (consistent with your ops) and a speed schedule of your choice (there has to be 3 or 4 options in your FCOM). Once this has been approved by your CAA, those numbers will be used to create your areas of operation (60,90,120,138,150,180,207 min) and inserted in your company docs (it is actualy an ops spec granted to you by your CAA).

[longreach777]

thnxs, that pretty much cleared most of it up.