If it is necessary to take off over an obstacle or from a critically short field, the procedures should be altered slightly. For example, the initial climb speed that should provide the best angle of climb for obstacle clearance is Vx rather than Vy.
However, Vx in some light twins is below Vmc. In this case, if the climb were made at Vx and a sudden power failure occurred on one engine, the pilot would not be able to control the airplane unless power were reduced on the operating engine. This would create an impossible situation because it would not be likely that the airplane could clear an obstacle with one engine inoperative and the other at some reduced power setting. In any case, if an engine fails and the climb is to be continued over an obstacle, Vxse must be established if maximum performance is to be obtained.
Generally, the short field or obstacle clearance takeoff will be much the same as a normal takeoff using the manufacturer's recommended flap settings, power settings, and speeds. However, if the published best angle of climb speed (Vx) is less than Vmc + 5, then it is recommended that no less than Vmc + 5 be used.
During the takeoff roll as the airspeed reaches the best angle of climb speed, or Vmc + 5, whichever is higher, the airplane should be rotated to establish an angle of attack that will cause the airplane to lift off and climb at that specified speed. At an altitude of approximately 50 feet or after clearing the obstacle, the pitch attitude can be lowered gradually to allow the airspeed to increase to the all engine best rate of climb speed. Upon reaching safe maneuvering altitude, the airplane should be allowed to accelerate to normal or enroute climb speed and the power controls reduced to the normal climb power settings.