﻿230 
  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  192'7 
  

  

  ever, 
  it 
  is 
  very 
  difficult 
  for 
  the 
  pilot 
  to 
  foresee 
  what 
  is 
  going 
  to 
  

   become 
  the 
  peak 
  of 
  a 
  gust. 
  

  

  Besides, 
  it 
  is 
  impossible 
  to 
  make 
  an 
  infinitely 
  sudden 
  turn. 
  Thus 
  

   one 
  has 
  to 
  turn 
  away 
  from 
  the 
  gust 
  quite 
  a 
  little 
  before 
  he 
  gets 
  his 
  

   full 
  share 
  of 
  the 
  beneficial 
  acceleration 
  nor 
  will 
  he 
  have 
  reached 
  

   quite 
  the 
  opposite 
  flight 
  direction 
  on 
  time 
  to 
  get 
  all 
  of 
  the 
  reverse. 
  

   In 
  addition 
  to 
  this, 
  even 
  a 
  quite 
  moderately 
  banked 
  turn 
  consumes 
  an 
  

   additional 
  tribute 
  of 
  power 
  in 
  the 
  form 
  of 
  the 
  increased 
  drag 
  induced 
  

   by 
  the 
  increased 
  wing 
  lift 
  necessary 
  to 
  overcome 
  the 
  centrifugal 
  force 
  

   of 
  the 
  turn. 
  Thus, 
  after 
  all 
  bills 
  are 
  paid 
  the 
  profit 
  is 
  materially 
  cut 
  

   down. 
  For 
  instance, 
  if 
  one 
  simply 
  circled 
  " 
  synchronically 
  " 
  in 
  a 
  

   slow 
  but 
  powerful 
  gust 
  of 
  harmonical 
  rhythm, 
  he 
  may 
  practically 
  

   gain 
  about 
  one-third 
  of 
  the 
  energy 
  theoretically 
  available. 
  

  

  On 
  the 
  other 
  hand, 
  if 
  satisfied 
  with 
  only 
  a 
  fair 
  fraction 
  of 
  the 
  

   entire 
  possible 
  gain, 
  you 
  may 
  fly 
  across 
  the 
  wind 
  and 
  merely 
  sway 
  

   from 
  your 
  course 
  somewhat 
  in 
  serpent 
  fashion, 
  corresponding 
  to 
  the 
  

   lateral 
  accelerations, 
  always 
  with 
  a 
  trend 
  of 
  keeping 
  weatherly. 
  

   In 
  fact, 
  this 
  is 
  a 
  very 
  reasonable 
  method 
  to 
  be 
  resorted 
  to 
  when 
  

   flying 
  along 
  a 
  mountain 
  ridge, 
  and 
  in 
  some 
  instances 
  I 
  am 
  quite 
  

   sure 
  I 
  picked 
  some 
  valuable 
  gain 
  from 
  such 
  lateral 
  gusts 
  this 
  way. 
  

   A 
  Frenchman, 
  Mr. 
  A. 
  See, 
  demonstrated 
  how 
  energy 
  can 
  be 
  gained 
  

   from 
  lateral 
  gusts 
  by 
  merely 
  rolling 
  the 
  machine 
  while 
  yielding 
  to 
  

   the 
  yaw, 
  so 
  as 
  to 
  present 
  the 
  raised 
  wing 
  always 
  to 
  the 
  luff 
  side. 
  

   However, 
  every 
  pilot 
  knows 
  this 
  to 
  be 
  a 
  somewhat 
  delicate 
  maneuver 
  

   and 
  trying 
  it 
  I 
  once 
  almost 
  heeled 
  over 
  in 
  the 
  face 
  of 
  a 
  rugged 
  peak, 
  

   having 
  underestimated 
  the 
  force 
  of 
  a 
  blow 
  which 
  apparently 
  shot 
  

   from 
  an 
  adjacent 
  gorge. 
  The 
  excessive 
  banking 
  and 
  subsequent 
  

   recovery 
  by 
  a 
  dive 
  spoiled 
  more 
  altitude 
  than 
  had 
  been 
  gained. 
  

  

  If 
  the 
  gust 
  is 
  also 
  accompanied 
  by 
  a 
  variation 
  in 
  wind 
  direction, 
  

   this 
  can 
  be 
  quite 
  useful 
  to 
  a 
  glider 
  endeavoring 
  to 
  take 
  those 
  unavoid- 
  

   able 
  turns 
  always 
  in 
  the 
  sense 
  of 
  the 
  turning 
  of 
  the 
  acceleration 
  

   vector. 
  Indeed, 
  an 
  optimum 
  condition 
  would 
  be 
  what 
  may 
  be 
  termed 
  

   a 
  circularly 
  polarized 
  gust. 
  An 
  airplane 
  properly 
  curving 
  would 
  be 
  

   centrifuged 
  like 
  a 
  heavier 
  particle 
  in 
  a 
  rotary 
  separator. 
  Trying 
  to 
  

   head 
  toward 
  the 
  pole 
  of 
  the 
  whirl, 
  the 
  ship 
  would 
  be 
  dynamically 
  

   impelled. 
  Whether 
  similar 
  conditions 
  actually 
  occur 
  in 
  the 
  atmos- 
  

   phere 
  outside 
  of 
  tornadoes, 
  I 
  do 
  not 
  know. 
  

  

  We 
  have 
  seen 
  the 
  necessity 
  of 
  performing 
  some 
  sort 
  of 
  a 
  change 
  

   of 
  flight 
  direction 
  during 
  the 
  climax 
  of 
  a 
  gust. 
  But 
  there 
  is 
  no 
  rea- 
  

   son 
  why 
  it 
  is 
  confined 
  to 
  the 
  horizontal 
  plane. 
  Someone 
  may 
  prefer 
  

   to 
  do 
  it 
  vertically. 
  However, 
  by 
  mere 
  analogy 
  it 
  can 
  be 
  seen 
  that 
  it 
  

   would 
  take 
  continuous 
  looping 
  the 
  loop, 
  synchronous 
  with 
  the 
  oscilla- 
  

   tions 
  of 
  the 
  gusts 
  in 
  order 
  to 
  get 
  anything 
  like 
  a 
  fair 
  portion 
  of 
  the 
  

   entire 
  available 
  energy. 
  This 
  is 
  impossible. 
  Again, 
  a 
  fraction 
  of 
  it 
  

   is 
  obtainable 
  by 
  performing 
  certain 
  vertical 
  rocking 
  movements. 
  

  

  