Originally Posted by
misd-agin
Normal gear retraction is as soon as a known, stabilized, rate of climb is achieved. For non pilots that typically confirmed prior to 50' AGL. With an engine failure, unless the plane is very light, the ability of an airliner to accelerate to get rid of flaps (reducing drag) is much tougher. Depending upon weight it might not be possible with the gear down.
In landing configuration, at a heavy weight right after takeoff, airliners don't have enough power to fly level. This was a training event that was introduced to demonstrate that at heavy weights (ie immediate return scenario), even at max power you'd be unable to hold level flight while in landing configuration while single engine. Rule of thumb "no gear down until you're going downhill" (ie descent patth without level offs).