The dark night take-off accident. An aircraft accelerating in the climb feels to the pilot to be climbing more steeply than intended (a). To correct this impression, the pilot pushes forward on the control column with the result that the aircraft may no longer be climbing (b) and with continued inappropriate control, may begin to descend (c). In the force vector diagram associated with each of the lower aircraft pictures, the constant thrust of the engine is represented by the backward inertial force that it generates, while the lift on the wings, which decreases as a consequence of the aircraft trajectory, is represented by an inertial force vector acting vertically downward with respect to the aircraft. The resultant vector representing the sum of these two forces is shown in bold. In the absence of clear external vision, as might occur on a dark night or a take-off into cloud, this resultant force can be perceived as the gravitational vertical with implications for the pilot's perception of the pitch attitude of the aircraft. Each image in the upper series has been rotated to align the resultant force vector with the true vertical so as to represent what the pilot might think is happening to the aircraft. It can be seen that the pilot's inappropriate control action may increase rather than decrease the perception of pitch-up of the aircraft.