dissipating requirements of the brakes.  There will be a maximum design landing  weight specified for each airpIane and this  limitation  must be respected because of  critical landing loads, arresting loads, or  brake requirements. Of course, any air-  plane will have a limiting touchdown rate  of descent  specified with the maximum land-  ing weight and the principal landing load  limitations will be defined by the combina-  tion. of gross weight and rate of descent at  touchdown.  (2) The surface winds must be considered  because  of the large effect of a headwind or  tailwind OR the landing distance. In the  case of the crosswind, the component of  wind along the runway will be the effective  headwind or tailwind velocity.  Also, the  crosswind component across  the runway will  define certain requirements of lateral control  power.  The airplane which exhibirs large  dihedral effect at high lift coefficients is  quite sensitive to crosswind and a limiting  crosswind component will be defined for the  configuration.  (3) Press.w~  dtitsde and tmpma~e will  affect the landing distance because of the  effect on the true airspeed for landing.  Thus, pressure  altitude and temperature must  be considered to define the density altitude.  (4) The runway condition must be con-  sidered for its effect on landing distances.  Runway slope of ordinary values will ordi-  narily favor selection of a runway for a  favorable headwind at landing.  The surface  condition of the runway will  determine  braking effectiveness  and ice or water on the  runway may produce a considerable increase  in the minimum landing distance.  Thus, preparation for the landing must in-  clude determination of the landing distance of  the airplane and comparison with the runway  length available. Use of the angle of attack  indicator and the mirror landing system will  assist the pilot in effecting touchdown at the  desired location with the proper airspeed.  Of  course, the landing is not completed until the  airplane is slowed to turn off the runway.  Control of the airpIane must be maintained  after the touchdown and proper technique must  be used to decelerate  the airplane.  TYPICAL ERRORS. There are many un-  desirable consequences  when basic principles  and specific procedures  are not followed during  the approach and landing.  Some of the typical  errors involved in landing accidents are out-  lined in the following discussion.  The steep, low power approach leads to an  exce.rsive  rate of descent  and the possibility of a  hard landing.  This is particularly the case  for the modern, low aspect ratio, swept wing  airplane configuration which incurs very large  induced drag at low speeds  and does not have  very conventional flare characteristics. For  this type of airplane in a steep, low power  approach, an increased  angle of attack without  a change of power setting may not cause a  reduction of rate of descent and may even in-  crease  the rate of descent at touchdown. For  this reason, a moderate stabilized approach is  necessary  and the principal changes in rate of  descent  must be controlled by changes in power  setting and principal changes in airspeed must  be controlled by changes in angle of attack.  ‘ An excessive  angle of attack during the ap-  proach and landing implies that the airplane is  being operated at too low an airspeed. Of  course, excessive  angle of attack may cause the  airplane to stall or spin and the low altitude  may preclude recovery. Also, the low aspect  ratio configuration at an excessively low air-  speed will incur very high induced drag and  will necessitate  a high power setting or other-  wise incur an excessive rate of descent. An  additional problem is created by an excessive  angle of attack for the airplane which exhibits  a large dihedral effect at high lift coefficients.  In this case, the airplane would be more sensi-  tive to crosswind.s  and adequate lateral control  may not be available to effect a safe landing at  a critical value of crosswind.  NAVWEPS OD-BOT-BO  APPLICATION OF AERODYNAMICS  TO SPECIFIC PROBLEMS OF FLYING 