Back in the day, I did quite a lot of 3-engine ferry flights on Boeing 747-100 and -200 series aircraft. As well as careful flight planning, here are some of the practical piloting considerations. First, the regulations allow only the three flight crew on board because often there is a critical period during the take-off run when it is neither possible to continue nor to stop. Second, you had to be 3-engine ferry flight qualified.
The reasons for this are that, during the take-off acceleration and shortly before lift-off, there is a short ‘gap’ of about 10 knots of airspeed between V-stop and the 2 engine Vmcg, typically between 130 to 140 knots. If an engine fails when the airspeed is below V-stop there is still room to stop (just) before the end of the runway. If an engine fails on the same side as the inoperative engine after passing this gap, the aircraft is then above Vmcg-2eng and you can continue the take-off with just enough rudder control to keep the aircraft straight on the runway.
If the engine fails, and it is on the same side as the inoperative engine, within the 10 knot gap you can neither stop nor continue. If you try to stop, you will go off the end of the runway despite using full braking. If you try to continue, there is not enough rudder control, it is impossible to keep straight and you will career off the side of the runway. The take-off weight needs to be kept as low as possible (commensurate with the sector length to be flown) to minimise this gap, hence the criticality of the take-off performance calculations and the fuel load.
The other problem with an inoperative outboard engine is directional control during the first part of the take-off run. You have to push and hold full rudder to counteract the thrust from the two good engines. You start by holding the aircraft stationary on the brakes while spooling up all three engines until they are stable. Then, you release the brakes and the flight engineer opens up the two inboard engines as fast as reasonably possible. Once you start moving, you open up the good outboard engine yourself, keeping the power just within the capability of the full rudder control – in effect, steering the aircraft with the engine until you are above the critical control speed (perhaps around 120 knots). It is a fairly demanding exercise but, once airborne, everything is straight forward, apart from checking minimum safe altitudes along the way, and suitable en-route alternates in case a second engine fails.
The landing at destination is a 'normal' 3-engine landing.
It was all a long time ago - I hope I have remembered it correctly!!
Last edited by Bergerie1; 31st January 2026 at 14:31.