text: in the phugoid is 
  quite large, typical values being from 20 to 100 
  seconds. Since the pitching rate is quite low 
  and only negligible changes in angle of attack 
  take place, damping of the phugoid is weak and 
  possibly negative. However, such weak or 
  negative damping does not necessarily have any 
  great consequence. Since the period of oscilla- 
  is easily able to 
  is so great, the pilot 
  tion 
  tendency by very 
  counteract the oscillatory 
  slight and unnoticed control movements. 
  In 
  most cases, the necessary corrections ate so 
  that the pilot may be completely un- 
  slight 
  aware of the oscillatory tendency. 