title: The optokinetic cervico reflex during simulated helicopter flight.
abstract: BACKGROUND
  The optokinetic cervico reflex (OKCR) is a recently hypothesized, visually driven reflex that serves to stabilize the image of the external horizon on the retina during roll maneuvers in high-performance aircraft. Although reported anecdotally, head tilt during helicopter flight has not been studied formally. Such research is required to determine the full impact and significance that it may have on the flying performance of a rotary-wing aviator.
  
  
  OBJECTIVE
  The aim of this study was to investigate the relationship between horizon position and the perception of orientation and, thus, to generate vital information to assess whether OKCR plays an important role in spatial disorientation.
  
  
  OBJECTIVE
  Pilots of rotary-wing aircraft will exhibit the OKCR.
  
  
  METHODS
  A UH-60 flight simulator study, with 20 volunteer pilots participating, was performed to examine the effects of this reflex during day flight and during flight with night vision goggles (NVGs).
  
  
  RESULTS
  The results confirm that the OKCR occurs during simulated helicopter flight, both with and without NVGs. As with previous studies, head roll increased during flight under visual meteorological conditions in relation to an increasing aircraft roll angle up to a maximum sustainable level and then remained constant. Head roll did not occur during flight under instrument meteorological conditions.
  
  
  CONCLUSIONS
  The presence of the OKCR will impact rotary-wing operations. Various aspects are discussed, and recommendations are made for future research.
authors.affiliation: U.S. Army Aeromedical Research Laboratory, Fort Rucker, AL, USA.
authors.forename: M G
authors.initials: MG
authors.lastname: Braithwaite
authors.forename: K G
authors.initials: KG
authors.lastname: Beal
authors.forename: E A
authors.initials: EA
authors.lastname: Alvarez
authors.forename: H D
authors.initials: HD
authors.lastname: Jones
authors.forename: A
authors.initials: A
authors.lastname: Estrada
mesh_terms: D000328:Adult; D000337:Aerospace Medicine; D000401:Aircraft; D003463:Cues; D003624:Darkness; D005139:Eyeglasses; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008889:Military Personnel; D009333:Neck / Q000502:physiology*; D017120:Nystagmus, Optokinetic / Q000502:physiology*; D012018:Reflex / Q000502:physiology*; D012678:Sensation Disorders / Q000209:etiology; D013028:Space Perception / Q000502:physiology*; D013647:Task Performance and Analysis; D013997:Time Factors; D014743:Videotape Recording; D014887:Weather