﻿SOARIMG 
  FLIGHT 
  KLEMPERER 
  237 
  

  

  and 
  others 
  incorporating 
  flapping 
  wings. 
  An 
  interesting 
  experience 
  

   was 
  gained 
  with 
  an 
  extremely 
  light 
  tail-first 
  machine. 
  It 
  became 
  

   longitudinally 
  unstable 
  when 
  starting, 
  due 
  to 
  the 
  vertical 
  gradient 
  

   of 
  the 
  wind 
  close 
  to 
  the 
  ground, 
  it 
  is 
  believed. 
  

  

  The 
  normal 
  glidei-s 
  are 
  equipped 
  with 
  elevator, 
  rudder, 
  and 
  aile- 
  

   rons, 
  and 
  are 
  controlled 
  very 
  much 
  like 
  " 
  real 
  " 
  airplanes. 
  Control 
  

   surfaces 
  are 
  often 
  comparably 
  large, 
  but 
  the 
  length 
  of 
  the 
  tail 
  is 
  

   short 
  in 
  comparison 
  with 
  the 
  wing 
  span. 
  Many 
  efforts 
  have 
  been 
  

   made 
  with 
  a 
  view 
  to 
  eliminating 
  the 
  vertical 
  rudder. 
  The 
  birds 
  have 
  

   evidently 
  quite 
  good 
  control 
  without 
  it. 
  However, 
  all 
  attempts 
  at 
  

   copying 
  the 
  ideal 
  warping 
  and 
  folding 
  mechanism 
  of 
  the 
  birds' 
  

   wings 
  or 
  at 
  replacing 
  it 
  by 
  some 
  other 
  device 
  have 
  not 
  so 
  far 
  pro- 
  

   duced 
  anything 
  decidedly 
  superior 
  to 
  a 
  rudder. 
  Various 
  kinds 
  of 
  

   wind 
  brakes 
  mounted 
  on 
  the 
  wing 
  tips, 
  which 
  on 
  a 
  glider 
  have 
  such 
  

   a 
  long 
  leverage, 
  have 
  been 
  tried 
  with 
  partial 
  success. 
  Flexible 
  

   camber 
  wings 
  and 
  tiltable 
  wings 
  have 
  been 
  flown 
  quite 
  successfully, 
  

   although 
  the 
  advantages 
  claimed 
  do 
  not 
  seem 
  to 
  be 
  exactly 
  in 
  pro- 
  

   portion 
  to 
  the 
  complication. 
  Some 
  device 
  with 
  which 
  to 
  control 
  

   the 
  gliding 
  angle 
  independently 
  of 
  the 
  angle 
  of 
  attack 
  and 
  speed 
  

   does 
  have 
  some 
  definite 
  usefulness, 
  however. 
  

  

  Some 
  inventors 
  believe 
  certain 
  special 
  wing 
  and 
  steering 
  mecha- 
  

   nisms 
  to 
  be 
  capable 
  of 
  performing 
  dynamical 
  soaring 
  flight 
  auto- 
  

   maticall3^ 
  Such 
  devices, 
  it 
  seems, 
  are 
  not 
  very 
  likely 
  to 
  meet 
  with 
  

   success. 
  There 
  is 
  a 
  fundamental 
  difficulty 
  involved, 
  closely 
  connected 
  

   with 
  the 
  problem 
  of 
  distinction 
  between 
  vertical 
  currents 
  and 
  hori- 
  

   zontal 
  gusts 
  and 
  with 
  the 
  correct 
  utilizing 
  maneuver 
  depending 
  on 
  

   more 
  than 
  what 
  can 
  be 
  mechanically 
  and 
  aerodynamically 
  grasped 
  

   from 
  aboard. 
  In 
  practice, 
  the 
  interpretation 
  of 
  the 
  sensation 
  of 
  equi- 
  

   librium 
  depends 
  to 
  a 
  large 
  extent 
  on 
  the 
  visual 
  observation 
  of 
  what 
  

   happens. 
  One 
  can 
  fly 
  with 
  his 
  eyes 
  closed 
  for 
  a 
  while, 
  but 
  not 
  a 
  bit 
  

   in 
  dynamical 
  soaring. 
  Neither 
  can 
  a 
  bird 
  in 
  pitch-dark 
  night. 
  Most 
  

   of 
  those 
  inventions 
  are 
  the 
  involuntary 
  result 
  of 
  a 
  confusion 
  of 
  the 
  

   problems 
  of 
  dynamical 
  soaring 
  and 
  that 
  of 
  stabilization 
  in 
  straight 
  

   flight. 
  The 
  two 
  problems 
  are 
  by 
  no 
  means 
  identical. 
  In 
  fact, 
  the 
  

   stabilizer 
  is 
  intended 
  to 
  make 
  the 
  machine 
  let 
  the 
  gust 
  pass 
  as 
  unno- 
  

   ticed 
  as 
  possible. 
  In 
  dynamical 
  soaring, 
  on 
  the 
  contrary, 
  the 
  gust 
  

   must 
  be 
  responded 
  to 
  by 
  a 
  vigorous 
  motion 
  in 
  order 
  to 
  wrest 
  energy 
  

   from 
  it. 
  However, 
  there 
  is 
  a 
  deepei^ 
  meaning 
  to 
  this 
  confusion: 
  The 
  

   knowledge 
  of 
  the 
  direction 
  of 
  gravity 
  is 
  a 
  fundamental 
  condition 
  for 
  

   any 
  creation 
  of 
  a 
  lift 
  with 
  which 
  to 
  oppose 
  that 
  gravity. 
  On 
  the 
  

   solid 
  grouud 
  or 
  even 
  on 
  a 
  big 
  and 
  sluggish 
  air 
  liner 
  in 
  calm 
  air 
  there 
  

   is 
  no 
  difficulty 
  to 
  that, 
  and 
  we 
  are 
  so 
  familiar 
  with 
  it 
  that 
  we 
  are 
  

   thoroughly 
  accustomed 
  to 
  consider 
  the 
  direction 
  of 
  gravity 
  as 
  an 
  

   established 
  reference 
  basis. 
  Yet, 
  on 
  a 
  glider 
  performing 
  dynamical 
  

  

  