Return alternate single engine distance.

[Zoyberg]

Assuming you have an engine failure and cannot get back into your departure aerodrome (say it is below cat 1 minima) how should the distance be worked out.

Our SOPs say within one hour single engine but does not advise on a distance. Some trainers use the 400NM figure used for 737 NG ETOPS.

If you have an engine failure in the cruise I am not convinced you could average 400 knots with your potential energy...that aside here are my totally unscientific ballpark figures.

20 mins in the climb at 220 knots...10 mins on approach averaging 200 knots and a max single engine speed for 30 mins of cruise of less than 400 knots = closer to 300 miles.

I assume there has to be some guidance (or at least some better empirical data than above) somewhere.

Any help much appreciated.

[TyroPicard]

I seem to recall the rules saying "one hour at the single-engine flying speed" and that speed would be quoted somewhere in the Flight Manual. It does not mean you can get there inside one hour!

[BOAC]

Some trainers use the 400NM figure used for 737 NG ETOPS. Although the figure, is as TP says, for PLANNING purposes only, the ETOPS figure is wildly inaccurate (but perhaps 'convenient'?) since it is based on a cruise/emergency descent and then a cruise segment. Typical 737 take-off alternate figures are 345/355nm and again as TP says - it SHOULD be specified in your manual as part of your company operating licence documentation, as should the s/e 'over-water' speed for route planning plus the ETOPS figure you quote. Whatever the book says that is what it is, not what some 'trainer' says.

[Todders]

Our figure for diversion en route your looking at one hour single eng cruise speed defined as 395kts(737-800/900). This is the non etops figure obviously.

From personal experiance you would have no prob maintaining this as a single eng cruise speed even on the under powered -900 but you won't be able to maintain cruise fl if you have anyone on board we had to drop to fl160. But performance wise no probs at all. You should have tables you can use for max cont. and fuel planning that are worked out on standard drift downs if you want to get an idea of worst case they have been thinking of. But if you getting involved in these when the "blank" is hitting the fan No. 1 your not using your fmc enough and No. 2 you a better man than me.

But as you said if it doesn't happen in cruise then that doesn't really work also you have to remember these are still air figures. Now if you are in the climb, are you gonna continue to climb??? i should think not if you can clear terain and are going to divert within afore mentioned dist. so basically you looking at leveling off at a suitable speed any sugestions??? I'd say you could easily achieve standard 250kts or if you wanna make it even easier you could go for 220kts (clean but already slowed to start an approach). These are poss figures you could use for youself and for preplanning on the ground. But this is by no means standard and therfore if you are using it i suggest you get your buddy on the flight deck with you in the picture. Remember of course losing an eng is not the end of the world level off settle yourself and dont rush it set up and hold somewhere if you need the time to prepare in europe you should have a prob with a diversion within and hours flying.

[Henry VIII]

Apt located within :
- One hour flight time at one-engine inop cruising speed according the AFM, still air conditions based on actual TO mass.
- The operator's approved ETOPS diversion time up to a max two hours, at one-engine inop cruising speed according the AFM, still air conditions based on actual TO mass for acft and crew authorized for ETOPS and subject to any MEL.

[Checkboard]

The single engine cruise speed used for ETOPS calculations varies from airline to airline, as each airline can choose the cruise speed they will use for their calculations. The trade-off is in choosing a faster single engine cruise (and hence a wider area of operations) the fuel flow increases significantly (and the amount of fuel carried to cover the worse case diversion.)