title: Frequency of the "push-pull effect" in U.S. Air Force fighter operations.
abstract: BACKGROUND
  Recent investigation into the push-pull effect (PPE), the reduction of +Gz tolerance when preceded by less than +1 Gz, has focused on centrifuge studies to demonstrate the presence of adverse cardiovascular responses. Maneuvers found to cause the Push-Pull Effect (PPEM) have not been studied previously in U.S. Air Force (USAF) fighter aircraft. The frequency of and extent to which PPEMs are performed in fighter aircraft are unknown.
  
  
  METHODS
  Head-up display (HUD) videotapes from F-15 and F-16 air combat training missions were reviewed for the presence of PPEMs. The frequency of engagements containing PPEMs and the magnitude of the Gz profiles were noted.
  
  
  RESULTS
  PPEMs were found in 11 to 67%, of engagements reviewed, depending on the nature of the training mission, with an overall average of 32%. The PPEMs that were observed contained segments of less than +1 Gz, ranging on average from 0.0 to 0.5 Gz for an average of 3.5 to 5 s duration.
  
  
  CONCLUSIONS
  PPEMs are present in air combat training missions performed by today's USAF fighter aircraft and represent an operationally significant source of risk for accidents. These findings support continued research into the physiologic response to PPE and the development of countermeasures.
authors.affiliation: U.S. Air Force School of Aerospace Medicine, Brooks AFB, TX 78235-5252, USA.
authors.forename: V J
authors.initials: VJ
authors.lastname: Michaud
authors.forename: T J
authors.initials: TJ
authors.lastname: Lyons
authors.forename: C M
authors.initials: CM
authors.lastname: Hansen
mesh_terms: D000054:Acceleration / Q000009:adverse effects*; D000060:Accidents, Aviation / Q000706:statistics & numerical data; D000337:Aerospace Medicine; D000401:Aircraft / Q000145:classification / Q000706:statistics & numerical data; D002320:Cardiovascular Physiological Phenomena; D006112:Gravitation; D006801:Humans; D008889:Military Personnel; D012189:Retrospective Studies; D012307:Risk Factors; D014481:United States