Since the beginnings of high-performance aircraft use circa WWII and perhaps even earlier, a primary limiting factor in maneuvering performance has been human ability to withstand high accelerations called "G-forces" when an aircraft changes direction rapidly at high speed. This centrifugal effect causes a person's body and limbs to seem much heavier than normal, as well as causing blood to collect in the extremities, resulting in effects known as gray-out, blackout and G-LOC (G-force loss of consciousness) when the blood is directed away from the pilot's head (positive G), and red-out when blood is directed toward the head (negative G). G-suits apply air pressure to the legs and lower body reducing the amount of blood leaving the head, allowing pilots to withstand momentary positive G-forces of around 12 G and longer sustained turns of about 9 G, but fighter aircraft have long been able to produce and structurally withstand forces greater than these, resulting in some fatal crashes, and leading to inclusion of G-limiting programming in flight control software of recent fighter aircraft.

It occurs to me that the human body is naturally nearly neutrally buoyant in water; thus, while underwater a person should be able to withstand much higher g-forces -- the hydrostatic pressure on the outside of the body would match that inside, conform perfectly to the body's contours, and prevent much of the blood pooling as well as the feeling of heaviness in the body, limbs and head.

Equipment needed to make a fluid-filled cockpit and allow a pilot to operate in such an environment would not be much more complicated than what is already required for pressurized cockpits and flight gear used in high-altitude aircraft. The main disadvantage would be the weight penalty. Even if the cockpit controls were optimized to minimize the amount of movement required by the pilot, thus allowing minimization of the volume of the cockpit capsule, the amount of water needed to fill it would still add several hundred pounds of weight to the aircraft. But the advantage in increased maneuverability might well be considered an acceptable trade-off.

Unfortunately, this idea now seems already obsolete as progress continues toward utilization of fully unmanned front-line aircraft for all missions.
-- A_J_Franzman, Aug 09 2007

Pilots need to move with pinpoint accuracy as quickly as they can.

Would not a fluid filled cockpit hinder the pilots movement speed?

As well, aerodynamics in modern jets are so precise that a computer is needed to translate the pilots actions in controlled movements, as the best human pilot is incapable of flying the Eurofighter without electronic aid.

With the jets of today likened to a dart thrown backwards using computers to keep it pointed that way to facilitate instant changes in direction, this extra weight front and center in the plane would hinder these actions further.
-- Giblet, Aug 09 2007


Custard filled cockpits would be easier to use as they would:

- Self-identify leaks - Provide nutrition in the case of a crash landing in a remote area - Have an adjustable viscosity depending upon mix
-- vincevincevince, Aug 09 2007


Surrounding something with water does not change the forces acting on it, the body may be neutrally bouyant but the blood inside the body is still more inclined towards the lowest point. However, the water would get heavier and so provide even more pressure on the hapless pilot, meaning that coming out of a 10G turn too fast would give you the bends.
-- marklar, Aug 09 2007


Re: "Pilots need to move with pinpoint accuracy as quickly as they can."

Accurately, yes, but I disagree with the "quickly as they can" part. They're not making gross flailing movements or rapid jerking movements; they're moving inches or fractions of inches with smooth precision, and the small additional viscosity won't slow those down much and may actually help with accuracy by damping overshoot. I also disagree about the weight being much of a hindrance to the aircraft's maneuverability if it's taken into account at the design stage. After all, fighter aircraft routinely carry several to tens of thousands of pounds of munitions.

Re: "the body may be neutrally bouyant but the blood inside the body is still more inclined towards the lowest point."

The blood within and the water outside will be affected nearly identically, for a net cancellation of the tendency for blood to move to the lower extremities -- in a high-g maneuver, the water pressure toward the bottom of the cockpit will increase outside the legs just as much as that of the blood inside.

Re: "coming out of a 10G turn too fast would give you the bends."

Free divers do not get the bends; they don't spend enough time at high pressure for significant additional nitrogen to be absorbed into the blood. Similarly, in a dogfighting aircraft, especially one that is much more maneuverable than one's opponent's, a pilot will not be subjected to high G-forces long enough for the increased static fluid pressure to allow buildup of excess nitrogen.
-- A_J_Franzman, Aug 20 2007



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