be practiced because these situations are hazardous and can  damage the WSC and injure occupants. These examples are  shown for informational purposes, in case similar situations  arise in the future.  The overall severity of a deceleration process is governed by  speed (groundspeed) and stopping distance. The most critical  of these is speed; doubling the groundspeed quadruples the  total destructive energy and vice versa. Even a small change  in groundspeed at touchdown, resulting from wind or pilot  technique, affects the outcome of a controlled crash. It is  important that the actual touchdown during an emergency  landing be made at the lowest possible controllable airspeed  using all available means. Most pilots instinctively—and correctly—look for the largest  available flat and open field for an emergency landing.  Actually, very little stopping distance is required if the speed  can be dissipated uniformly; that is, if the deceleration forces  can be spread evenly over the available distance. This concept  is designed into the arresting gear on aircraft carriers, and  provides a nearly constant stopping force from the moment  of hookup. For example, assuming a uniform 2 G deceleration while  landing into a headwind with a 25 mph groundspeed, the  stopping distance is about 10.5 feet; in a downwind landing  at 50 mph groundspeed, the required stopping distance is  42 feet—about four times as great.  [Figure 13-3]  Although  these figures are based on an ideal deceleration process,  it is interesting to note what can be accomplished in an  effectively used short stopping distance. Additionally,  landing uphill reduces the stopping distance and landing  downhill increases the stopping distance. Understanding  the need for a firm but uniform deceleration process in very  poor terrain enables the pilot to select touchdown conditions  that spread the breakup of dispensable structure over a short  distance, thereby reducing the peak deceleration of the fl ight  deck area. A careful consideration must be made considering  wind, slope, and terrain. The most critical and often the most inexcusable error that  can be made in the planning and execution of an emergency  landing, even in ideal terrain, is the loss of initiative over  the aircraft’s attitude and sink rate at touchdown. When the  touchdown is made on flat, open terrain, an excessive nose- low pitch attitude brings the risk of “sticking” the nose in  the ground. Steep bank angles just before touchdown should  also be avoided, as they increase the stalling speed and the  likelihood of a wingtip strike. Since the aircraft’s vertical component of velocity is  immediately reduced to zero upon ground contact, it must  be kept well under control. A flat touchdown at a high sink  rate (well in excess of 500 feet per minute (fpm)) on a  hard surface can be injurious without destroying the fl ight  deck structure depending on the design of the airframe and  the shock absorbing system. On soft terrain, an excessive  sink rate may cause digging in of the nose wheel with the  wing and/or WSC aircraft rotating forward into the ground,  stopping with severe forward deceleration or tumbling with  higher speeds. 10 20 30 40 2 G deceleration 42 feet 10.5 feet Headwind Tailwind Groundspeed 25 mph Groundspeed 50 mph Figure 13-3. Stopping distance vs. groundspeed.  Attitude and Sink Rate Control 13-5