﻿SOAEING 
  FLIGHT 
  KLEMPEKBR 
  225 
  

  

  the 
  contour 
  of 
  the 
  mountain. 
  Then 
  the 
  direction 
  and 
  magnitude 
  of 
  

   the 
  local 
  velocity 
  anywhere 
  in 
  the 
  field 
  can 
  be 
  calculated 
  by 
  simple 
  

   geometrical 
  addition 
  of 
  the 
  horizontal 
  wind 
  to 
  the 
  resultant 
  influence 
  

   of 
  all 
  sources 
  and 
  sinks 
  upon 
  that 
  point. 
  

  

  Since 
  the 
  equations 
  of 
  the 
  stream 
  lines 
  happen 
  to 
  be 
  identical 
  with 
  

   the 
  equations 
  of 
  the 
  equipotential 
  lines 
  in 
  an 
  electric 
  field, 
  several 
  

   investigators 
  have 
  made 
  experimental 
  use 
  of 
  this 
  remarkable 
  analogy 
  

   and 
  derived 
  flow 
  structures 
  by 
  electrically 
  sounding 
  in 
  a 
  tank 
  filled 
  

   with 
  an 
  electrolyte 
  between 
  electrodes 
  shaped 
  according 
  to 
  the 
  bound- 
  

   ary 
  lines 
  of 
  the 
  flow 
  problem. 
  

  

  Actual 
  full-size 
  measurements 
  of 
  the 
  wind 
  texture 
  on 
  the 
  wind- 
  

   ward 
  side 
  of 
  the 
  coast 
  at 
  the 
  Rossitten 
  soaring 
  flight 
  site 
  were 
  

   accomplished 
  last 
  summer 
  by 
  taking 
  motion 
  pictures 
  of 
  the 
  clouds 
  

   left 
  by 
  smoke 
  rockets 
  fired 
  up 
  to 
  various 
  heights. 
  The 
  results 
  

   of 
  these 
  experiments 
  and 
  others 
  made 
  with 
  ammonia 
  clouds 
  

   revealed 
  that 
  the 
  acceleration 
  of 
  the 
  wind 
  right 
  above 
  the 
  crest 
  

   and 
  the 
  upward 
  deflection 
  at 
  the 
  bottom 
  of 
  the 
  slope 
  are 
  

   somewhat 
  smaller 
  than 
  would 
  be 
  expected 
  from 
  the 
  analogous 
  po- 
  

   tential 
  flow. 
  Explanation 
  is 
  anticipated 
  to 
  be 
  found 
  in 
  friction 
  and 
  

   the 
  thermic 
  gradient. 
  

  

  The 
  best 
  locations 
  for 
  static 
  soaring 
  are 
  usually 
  to 
  be 
  found 
  at 
  

   some 
  distance 
  windward 
  off 
  the 
  crest. 
  The 
  useful 
  zone 
  may 
  extend 
  

   to 
  considerable 
  altitude, 
  at 
  times 
  twice 
  as 
  much 
  as 
  the 
  height 
  of 
  the 
  

   mountain 
  above 
  its 
  base. 
  Obviously, 
  the 
  vertical 
  deflection 
  com- 
  

   ponent 
  decreases 
  with 
  higher 
  altitude. 
  Thus 
  a 
  glider 
  which 
  has 
  a 
  

   well-defined 
  minimum 
  rate 
  of 
  descent 
  will 
  find 
  a 
  definite 
  " 
  ceiling 
  " 
  

   above 
  the 
  crest, 
  beyond 
  which 
  it 
  can 
  not 
  climb 
  in 
  static 
  soaring. 
  Very 
  

   favorable 
  conditions 
  occur 
  above 
  horseshoe-like 
  formations 
  of 
  gorges. 
  

   The 
  leeward 
  side 
  of 
  the 
  mountain 
  is 
  feared 
  for 
  its 
  treacherous 
  

   descending 
  currents, 
  weird 
  whirls, 
  and 
  dead 
  zones. 
  

  

  It 
  is 
  eas}'^ 
  to 
  see 
  that 
  there 
  is 
  no 
  fundamental 
  difficulty 
  in 
  remain- 
  

   ing 
  aloft 
  for 
  an 
  unlimited 
  duration 
  as 
  soon 
  as 
  the 
  pilot 
  has 
  found 
  a 
  

   sufficiently 
  wide 
  area 
  of 
  sufficiently 
  strong 
  rising 
  wind 
  currents, 
  as 
  

   long 
  as 
  he 
  sticks 
  to 
  it 
  and 
  the 
  wind 
  endures. 
  In 
  fact, 
  some 
  of 
  the 
  

   duration 
  record 
  flights 
  were 
  made 
  by 
  patiently 
  cruising 
  in 
  figure 
  

   eights 
  above 
  the 
  same 
  place 
  and 
  extended 
  far 
  into 
  night-time, 
  when 
  

   landings 
  had 
  to 
  be 
  made 
  in 
  the 
  light 
  of 
  automobile 
  headlights 
  and 
  

   flares. 
  The 
  longest 
  duration 
  ever 
  flown 
  by 
  a 
  glider 
  was 
  12 
  hours 
  

   and 
  a 
  few 
  minutes, 
  attained 
  by 
  Herr 
  F. 
  Schulz 
  in 
  1924 
  on 
  the 
  Ros- 
  

   sitten 
  coast.- 
  The 
  same 
  pilot 
  has 
  later 
  flown 
  nine 
  hours 
  with 
  a 
  

   passenger. 
  

  

  It 
  is 
  considerably 
  more 
  difficult 
  to 
  cover 
  large 
  distances, 
  how- 
  

   ever. 
  The 
  first 
  distance 
  flights 
  were 
  made 
  by 
  climbing 
  to 
  the 
  

  

  " 
  On 
  May 
  5, 
  1927, 
  he 
  beat 
  his 
  own 
  record, 
  staying 
  aloft 
  14 
  hours 
  7 
  minutes. 
  

  

  