G-LOC – Then and Now…

16 September 2011. Reno, Nevada saw the tragic crash of a P-51Mustang [1] during the Reno Air Races. The findings of the National Transportation Safety Board suggests that the pilot had lost consciousness due to ‘overwhelming’ G forces [2]. This occurrence in a modified 1940’s vintage aircraft is no surprise, considering its high thrust to weight ratios amongst its contemporaries, with a structural strength of -2G to +9G, making it likely that G induced loss of consciousness (G-LOC) could have been the cause of this tragedy, where besides the pilot, 10 spectators also perished [2, 3].

Invariably though, most people associate G-LOC related incidents with high performance aircraft, forgetting that this malady of manoeuvers in aviation was reported as early as 1919. First reported by the British as “fainting in the air” in World War I, it was also reported during the 1922 Pulitzer Trophy Air Race in the United States [4]. And all this was occurring in those early aircraft like Sopwith Camel and DeHaviland.

One aircraft  with a massive structural  “G-tolerance” was the Sopwith Pup [5]. This, 1916 vintage canvas wing, bi-plane with wooden frames had  a maximum speed of  less than 100 Kt, with a service ceiling of around 15,000 ft (without any supplemental oxygen or G protection!). This aircraft was designed to undertake a controlled bunt, with structural  limits of -5G! Those pilots surely would have had “Red out” during those -Gz manoeuvers. It could  perform a U-Turn in less than 200 yards of air space, clocking up  almost 8 G in the process. Since those brave hearts did not know anything about G-LOC, neither were there any anti-G suits designed then, so they flew on [3]…

Sopwith Pup

World War II saw the Mitsubishi’s Zero aircraft [6], which was highly agile and extremely maneuverable due to its abnormally large  “ailerons”, even  at speeds below 275 mph. With its extremely light and steady elevators, the A6M2 variant of Zero could make tight turns above 300 mph, and the speed would not wash off during such tight turns, exposing its pilots to high Gs, almost reaching +8G, and that too sustained! Imagine flying A6M2 without an anti-G suits, and engaging dogfights – as the Zero did as compared to any other aircraft in history [3].


Much later, USAF introduced F-16 aircraft, a fly-by-wire, “highly nimble” aircraft, with ability to sustain G forces during tight turns [7]. Reportedly this induction in service saw accidents due to G-LOC for pilots converting from F-4 to F-16. This led the USAF to introduce high-G training to brief the pilots about the perils of high sustained G as well as learn for them to learn anti-G straining manoeuver (AGSM) under simulated G in a human centrifuge [4].

F-16 Fighting Falcon

G-LOC occurred then, when the aviation had just been invented, and continues to cost precious lives even today, if a pilot executes a combat manoeuver beyond his tolerance limits. The need for awareness about aircraft performance and limitations of human performance stays relevant even today.

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1. P-51 Mustang

2. NTSB: Pilot overwhelmed by g-forces in Reno crash 

3. Personal Communication – Dr US Mohalanobish a.k.a Dr Bish

4. Burton RR. G-induced loss of consciousness: Definition, history, current status. Aviat Space Environ Med 59; 1988: 2-5

5. Sopwith Pup

6. Mitsubishi A6M Zero

7. F-16 Fighting Falcon

Acknowledgement  Image Courtesy Wikimedia Commons

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