NAVWEPS 00-8OT-80  HIGH SPEED AERODYNAMICS  airplane are developed, the most likely general  configuration properties will beas follows:  slowed gradually through a series of very  weak oblique shock waves to a speed just  above sonic velocity.  Then the subsequent  normal shock to subsonic could be quite weak.  Such a combination of the weakest possible  waves would result in the least waste of energy  and the highest pressure recovery.  The ef-  ficiency of various types of diffusers is shown  in figure 3.20 and illustrates this principle.  (1) The wing will be of low aspect ratio,  have noticeable taper, and have sweepback  depending on the design speed range. The  wing sections will be of low thickness ratio  and require sharp leading edges.  (2) The fmelagc and naceller will  be of  high fineness  ratio (long and slender). The  supersonic pressure distribution may create  significant lift and drag and require con-  sideration of the stability contribution of  these surfaces.  (3) The t&Z surfaces  will  be similar to  the wing-low  aspect ratio, tapered, swept  and of thin section with sharp leading edge.  The controls will be fully powered and ir-  reversible with  all movable surfaces the  most likely configuration.  (4) In order to reduce interference drag  in transonic and supersonic flight, the gross  cross section of the aircraft may be “area  ruled” to approach that of some optimum  high speed shape.  An obvious complication of the supersonic  inlet is that the optimum shape is variable with  inlet flow direction and Mach number. In  other words, to derive highest efficiency and  stability of operation, the geometry of the  inlet would be different at each Mach number  and angle of attack of flight.  A typical super-  sonic military aircraft may experience large  variations in angle of attack, sideslip angle,  and flight Mach number during normal oper-  ation.  These large variations in inlet flow  conditions create certain important design  considerations.  (1) The inlet should provide the highest  practical efficiency. The ratio of recovered  total pressure to airstream total pressure  is  an appropriate measure of this efficiency.  (2) The inlet should match the demands  of the powerplant for airflow. The airflow  captured by the inlet should match that  necessary  for engine operation.  (3) Operation of the inlet at flight condi-  tions other than the design condition should  not cause a noticeable loss of efficiency or  excess drag. The operation of the inlet  should be stable and not allow  “buzz”  conditions (an oscillation of shock location  possible during off-design operation).  One of the most important qualities of high  speed configurations will  be the low speed  flight characteristics. The low aspect ratio  swept wing planform has the characteristic  of high induced drag at low flight speeds.  Steep turns, excessively low airspeeds, and  steep, power-off approaches can then produce  extremely high rates of descent  during landing.  Sweepback and low aspect ratio can cause  severe deterioration  ‘ of handling qualities at  speeds below those recommended for takeoff  and landing.  On the other hand, thin, swept  wings at high wing loading will have rela-  tively high landing speeds. Any excess of  this basically high airspeed can create an im-  possible requirement of brakes, tires, and arrest  ing gear. These characteristics require that  the pilot account for the variation of optimum  speeds  with weight changes and adhere to the  procedures and techniques outlined in the  flight handbook.  In order to develop a good, stable inlet design,  the performance at the design condition may  be compromised. A large variation of inlet  flow conditions may require special geometric  features for the inlet surfaces  or a completely  variable geometry inlet design,  SUPERSONIC CONFIGURATIONS.  When  all the various components of the supersonic 