Decision point

[Black_Dawn]

Hello everyone ,my first post!

I have a question about the legal aspect of the decision point you must have during crossing high altitudes terrain with two engine airliners in case of one engine failure.Let's say you got defined a decision point during crossing the Alps (your aircraft is heavy, you need it) and ATC gives you a short cut,that deviates you from the DP.Do you accept it or not?

[Slick]

This was always a problem on the 1-11, we had simple drift down tables, I also seem to recall a requirement to make a note of your single-eng level off height on the plog.

As far as a decision point goes, well thats down to you like most things in life ! and so much depended on the day. There was a chart floating about,(think I may still have one) with beacons and various radials and distances, which used to show the best route to fly during the drift down, I don't know who produced it but I think simular charts have been constructed in the past for route aproval from the authority.

Best regds

[john_tullamarine]

Requirements are straight forward

(a) 1000 ft clearance
(b) 2000 ft on driftdown if (a) is not achievable

If your original planning is tossed out the window with a rerouting .. then the sums must be considered again for the new route ...or else be very sure that the motors keep going ...

[Slick]

Yes, JTs quite correct, but while the requirements are straightforward the reality is not. In older twinjets, (I refer in particular to the 1-11 because I know it) complying with the legal requirements stated by JT above would have imposed an unrealistic weight peniltly. It was not uncommon to have a single-eng stablizing altitude in the very low teens sometimes lower. Hence the reason why the charts I refered to earlier were produced for approval to opperate in/over mountainious areas.

Going back to reality for a mo, re-routings flying lower than you might was/is of course common, the trick was planing for the worst knowing where you are and what you were going to do should you lose an engine, this was of course part of the en-route briefing. Having said that your risk exposure, when considering the alps and the 1-11 was not unreasonably high, it just needed a bit of thought thats all.

Best regds

[Black_Dawn]

Thanks JT and Slick
what i understand is that you will accept a re-routing: only if your aircraft altitude (single eng) can be stabilized at grid min safe alt along new route, otherwise you will not.