When comparing operation on one engine during the departure phase to the same during the approach phase one must remember the following very important facts;
1. At departure the weight is higher than during the approach at the end of (or later in) a flight;
2. During an approach, the attitude is low and a simple slight lowering of pitch can regain any lost speed without significant alteration of the profile;
3. During departure, the nose attitude is high, drag is relatively high and potential energy loss when an engine fails is significant
4. Many light multi engine aircraft have negative climb gradients at Max take-off weight
5. During the approach phase, the pilot is minded towards getting the aircraft on the ground and simply closing both throttles and gliding is not totally alien.
6. During the departure phase, the pilot is minded towards gaining height and closing both throttles can be very alien.
When departing, if no positive flight path can be constructed following engine failure then there are ceiling and visibility limitations that provide some posibility of a successful forced landing.
Regards,
DFC
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Pilot Bear,
Don't forget that blue line is best rate of climb speed single engine. Just like a single engine aircraft, it can be possible to climb at speeds above and below that speed but the rate is reduced. Of course if the gradient is negative at blue line then just like the best glide speed in a single, either side will vary the rate of descent.