THE PHYSICS OF FLIGHT BGen (Ret’d) Gregory C.P. Matte, CD, PhD
GM Article: The Physics of Flight
VFC General Manager Admittedly, this article is nearly two years overdue, and was inspired by a brief yet enlightening discussion with Dr. Geoff Steeves as it pertained to providing his undergraduate students with a guest lecture on practical applications of the laws of physics. As fellow aviators, Geoff was intrigued with my brief yet visceral explanation of the application of energy management in “dog fighting”, as it pertained to aerial fighter tactics. As for myself, I was interested in the performance metrics of the Cessna 172S. My military experience infused an interest in exploring the outer performance limits of the CF-5 Freedom Fighter, and more specifically, the CF-18 Hornet, so as to establish my own baseline of the ultimate limits of performance. This knowledge and experience served to provide me with the confidence to take the CF-18 to its established limits (and beyond), while enjoying the ability to fully exploit the entire spectrum of the Hornet’s performance envelope in mock dogfighting training sessions. Underlying this discussion with Geoff was a narrative that I would loosely describe as the “physics of flight”. As a starting point, lets agree that everyone who takes flying lessons becomes acquatinted with and learns to trust Bernoulli’s equation and the theory of lift. This theory is witnessed every time we take-off from terra firma as a result of the lift created by the low-pressure environment on the top surface 6
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an asymmetrically designed wing such as we find on the Cessna. However, the theory of lift and the physics of flight can quickly expand beyond the basics, as I came to appreciate when I progressed from flying the CT-134A Beechcraft Musketeer, through to the CT-114 Tutor and onto the CF-5 Freedom Fighter. The CF-5 was the “lead-in” conversion trainer that was required before advancing onto the CF-18 Hornet.
lowest airspeed in which the maximum permissible G-forces can be applied. In the CF-18, corner speed was situated between 310 to 325 KIAS depending on the weight and configuration (external stores) of the aircraft. A primary factor in dogfighting is gaining “angles” on My introduction to basic the opponent, particularly when fighter maneuvers (aka “dog the duel starts with a neutral fighting”) was preceded by an advantage (e.g., the aircraft meet academic introduction to energy head on). As such, when one management theory as well as considers the(simplified) formula the dynamics of 3-dimensional relating to turn radius, namely maneuvering that were part of r=v2/g2,the importance of corner the basic fighter pilot training curriculum. The primary objective speed becomes apparent. If your airspeed is well in excess of corner of dogfighting is to maneuver speed, say 500 KIAS, then the one’s aircraft into a weapons turn radius will be approximately engagement zone (WEZ) against 12,350 feet despite being able the opponent in which either to pull 7.5 G, whereas at a speed a missile can be successfully of 315 KIAS and 7.5 G, the turn fired, or the gun can be applied. radius would be considerably However, unless the opponent tighter at approximately 4,900 is caught completely off guard, feet. Conversely, as airspeed one must balance the efforts to maneuver into a WEZ with that of decreases below corner speed, avoiding becoming the target due the amount of G that can be to an error in maneuvering tactics pulled decreases as well. Thus, at an airspeed of say 200 KIAS, the or an excessive loss of airspeed. CF-18 can only pull about 2.5 G, Airspeed dictates maneuvering performance, with the sweet spot thereby leading to a turn radius of approximately 17,800, so getting commonly referred to as “corner speed”. It is also why fighter pilots slow in a dogfight can quickly become a fatal disadvantage, often state that “speed is life” further reinforcing the adage that when it comes to dogfighting. “speed is life”! Corner speed equates to the VFC | Aviation Excellence Since 1946
