International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / During high performance fighter aircraft manoeuvres, a fighter pilot may be exposed to a physiological phenomenon known as the “Push-Pull Effect” (reference (ref) [1]). This effect will alter the pilot’s homeostasis whereas blood flow to the brain will be increased during low negative normal acceleration (-Gz) and suddenly decreased during positive normal acceleration (+Gz). It has been hypothesized that this effect can lessen the Gtolerance of the human body thereby making the subject more susceptible to G induced Loss of Consciousness (G-LOC) (refs [2], [3] and [4]). G-LOC is not a desirable state for a pilot in a high performance aircraft such as a CF-18. To better understand and study the Push-Pull Effect on a fighter pilot, the Aerospace Engineering Test Establishment (AETE) and the Defence and Civil Institute of Environmental Medicine (DCIEM) produced an In-Flight Research (IFR) Program sponsored by the Canadian Forces (CF). The aim of this program was to measure the physiological response of relaxed test subjects, unprotected by a G-suit, when exposed to the Push-Pull manoeuvre in flight. This IFR would validate the centrifuge data and confirm that the Push-Pull Effect can occur in flight. This paper will present the instrumentation, design, telemetry system and installation methodology utilized to perform experimental physiological research on a high performance, ejection seat equipped fighter aircraft (CF-18). Also, preliminary results on the Push-Pull Effect, obtained through this IFR Program will be presented.