• If heavy tree trunk contact is unavoidable once the  airplane is on the ground, it is best to involve both  wings simultaneously by directing the airplane  between two properly spaced trees. Do not attempt  this maneuver, however, while still airborne. 17-6 An emergency descent is a maneuver for descending as  rapidly as possible to a lower altitude or to the ground for an  emergency landing.  [Figure 17-6]  The need for this maneuver  may result from an uncontrollable fire, a sudden loss of  cabin pressurization, or any other situation demanding an  immediate and rapid descent. The objective is to descend the  airplane as soon and as rapidly as possible within the structural  limitations of the airplane. Simulated emergency descents  should be made in a turn to check for other air traffic below  and to look around for a possible emergency landing area. A  radio call announcing descent intentions may be appropriate  to alert other aircraft in the area. When initiating the descent,  a bank of approximately 30 to 45° should be established to  maintain positive load factors (G forces) on the airplane. The decision to continue straight ahead is often difficult to  make unless the problems involved in attempting to turn  back are seriously considered. In the first place, the takeoff  was in all probability made into the wind. To get back to  the takeoff field, a downwind turn must be made. This  increases the groundspeed and rushes the pilot even more in  the performance of procedures and in planning the landing  approach. Secondly, the airplane is losing considerable  altitude during the turn and might still be in a bank when the  ground is contacted, resulting in the airplane cartwheeling  (which would be a catastrophe for the occupants, as well as  the airplane). After turning downwind, the apparent increase  The altitude available is, in many ways, the controlling factor  in the successful accomplishment of an emergency landing.  If an actual engine failure should occur immediately after  takeoff and before a safe maneuvering altitude is attained, it  is usually inadvisable to attempt to turn back to the field from  where the takeoff was made. Instead, it is safer to immediately  establish the proper glide attitude, and select a field directly  ahead or slightly too either side of the takeoff path. Consider the following example of an airplane which has  taken off and climbed to an altitude of 300 feet above ground  level (AGL) when the engine fails.  [Figure 17-5]  After a  typical 4 second reaction time, the pilot elects to turn back  to the runway. Using a standard rate (3° change in direction  per second) turn, it takes 1 minute to turn 180°. At a glide  speed of 65 knots, the radius of the turn is 2,100 feet, so at  the completion of the turn, the airplane is 4,200 feet to one  side of the runway. The pilot must turn another 45° to head  the airplane toward the runway. By this time, the total change  in direction is 225° equating to 75 seconds plus the 4 second  reaction time. If the airplane in a poweroff glide descends  at approximately 1,000 fpm, it has descended 1,316, feet  placing it 1,016 feet below the runway. Loss of depth perception may occur when landing on a wide  expanse of smooth water with the risk of flying into the  water or stalling in from excessive altitude. To avoid this  hazard, the airplane should be “dragged in” when possible.  Use no more than intermediate flaps on low-wing airplanes.  The water resistance of fully extended flaps may result in  asymmetrical flap failure and slowing of the airplane. Keep a  retractable gear up unless the AFM/POH advises otherwise. A landing in snow should be executed like a ditching, in  the same configuration and with the same regard for loss  of depth perception (white out) in reduced visibility and on  wide-open terrain. Concerning the subject of turning back to the runway following  an engine failure on takeoff, the pilot should determine the  minimum altitude an attempt of such a maneuver should  be made in a particular airplane. Experimentation at a safe  altitude should give the pilot an approximation of height lost  in a descending 180° turn at idle power. By adding a safety  factor of about 25 percent, the pilot should arrive at a practical  decision height. The ability to make a 180° turn does not  necessarily mean that the departure runway can be reached  in a power-off glide; this depends on the wind, the distance  traveled during the climb, the height reached, and the glide  distance of the airplane without power. The pilot should also  remember that a turn back to the departure runway may in  fact require more than a 180° change in direction. A well-executed water landing normally involves less  deceleration violence than a poor tree landing or a touchdown  on extremely rough terrain. Also, an airplane that is ditched  at minimum speed and in a normal landing attitude does not  immediately sink upon touchdown. Intact wings and fuel  tanks (especially when empty) provide floatation for at least  several minutes, even if the cabin may be just below the water  line in a high-wing airplane. in groundspeed could mislead the pilot into attempting to  prematurely slow down the airplane and cause it to stall. On the  other hand, continuing straight ahead or making a slight turn  allows the pilot more time to establish a safe landing attitude,  and the landing can be made as slowly as possible, but more  importantly, the airplane can be landed while under control. Water (Ditching) and Snow Engine Failure After Takeoff (Single- Engine) Emergency Descents