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A-10 stress, looks like you are the resident aeronautical engineer on this forum so I thought I would run a question by you, or anyone else who could weigh in their two cents.

Whats your opinion of VG in modern fighter aircraft? From what I have read, it was the latest greatest from about 1965 to 1974, then the F-15 came out with its performance and VG seemed to lose its ferver.

The F-14 has the mach sweep programmer to automize the process, and free the aviator to fight the enemy. Seems to me the only compromise on this is weight, and the fact that the wing sweep cannot anticipate what is going to happen next in the flight regime, and you lose some stealthiness. Would a next generation VG design that included some limited stealth characteristics, and a flight computer that could "adabt" it to the optimum performance envelope of the aircraft to give it some manouver anticipation chracteristics be a viable and realistic design? Seems to me with thrust vectoring, light weight composites, and other improvements since the early 70's, that the VG concept still holds some promise.

I know we had another thread on the matter, but I wanted to take that topic a bit further, so I apologize about the redundancy, or the layman verbage of my question.

I'm not an aerodynamicist either. I praise the F-14 wing because it is so good at helping the job I really do, that is airframe strength. When I was doing loads/stress preliminary design at Northrop I was forced to understand what the sources of load were and how to mitigate them. I learned that low speed flight charachteristics are the key to keeping the carrier compatability penalty weight down. In fact, for a large strike aircraft, such as the A-12, getting the speed down is the difference between something that can operate from a ship routinely or something that overuns the launch and recovery equipment with every flight (read that program cancellation prone). In the case of the F-14 wing, I believe the extra weight for the VG system is more than compensated for by weight savings arising from the slower launch/recovery speeds. Five knots can make a big difference. It means almost 1 foot per second more sink rate, which means another inch or so more stroke in the maingear, which means more weight from the gear and the stowage space for it. The hook load will go up about 10,000 pounds for that same 5 knots. If you can't accommodate the increased stroke, then all the gear loads go up astronomically. Pay me now or pay me later. For launch there are similar gains with a good wing. Not only does useable low speed lift help you with the maximum catapult load required to gain the flying speed, things like increased span decrease induced drag (due to lift) and keep you out of the "back side of the power curve" longer. Longer span also means that the angle of attack can be less for the same amount of lift (a higher lift curve slope). That means a lot when you need to rotate the nose up after a cat shot to get enough lift to support the weight. Less time is required to rotate to the required angle and the sink over the bow is minimized. Even for recovery, a higher lift curve slope is beneficial allowing a better view over the nose and less likely tail strikes, maybe eliminating a tail bumper. The F-14 VG allows it to have the maximum allowable span without violating the foul line and a minimum span that requires no fold. The leading edge sweep angle is so large at max sweep it allows a reasonably deep wing box (as opposed to the F-18 razor blades). This combined with a stellar max lift coefficient arising from the leading edge slatted, single slotted fowler flapped, direct lift control spoiler option really makes the loads minimum. It gives us a fighting chance to meet our weights. And you get all this without compromising (apparently, you'll have to talk to an aerodynamic expert)supersonic capability and the option of programmed variable sweep within the whole envelope...sweet. Good stuff. A good wing design gives me goose bumps. Keep that in mind you aero guys. It's not all about you all the time.

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"Who cares if it works? Does it look good on the ramp?"

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