Pitch-up
This too can be reduced to a single weight term acting at some point along the longitudinal axis of the aircraft, the "center of gravity", or CoG.
On a conventional rectangular wing, the CoP meets the aircraft at the point on the chord running directly out from the root.
Although it had long been known that an elliptical planform is "perfect" from an induced drag standpoint, it was also noticed that a linear taper of the wing had much the same effect, while being lighter.
Although this effect was unfavourable in a conventional straight wing aircraft, on a swept-wing design it had unexpected and dangerous results.
At lower speeds, however, this can lead to a considerable buildup of the boundary layer at the wing tip, adding to the problems noted above.
This was not always enough to correct for the problem, however; the F-86 continued to suffer from pitch-up in spite of increasing nose-down pressure from the tail surfaces.
This disrupts the flow and re-directs it rearward, while also causing the buildup of stagnant air inboard to lower the stall point.
To address the problems with spanwise loading, a wider variety of techniques have been used, including dedicated slats or flaps, the use of washout or automated control of the ailerons.
Although at first glance it would appear that this would cause pitch-down problems, the extreme rear mounting of the wing means that when the root stalls the lift moves forward, towards the tips.
One of the most notorious incidents was the loss of F-100C-20-NA Super Sabre 54-1907 and its pilot during an attempted emergency landing at Edwards AFB, California on January 10, 1956.
By chance, this particular incident was recorded in detail on 16 mm film by cameras set up to cover an unrelated test.
The pilot fought desperately to regain control due to faulty landing technique,[11] finally rolling and yawing to the right before striking the ground with the fuselage turned approximately 90 degrees to the line of flight.
The aircraft was one of three being delivered from North American's Palmdale plant to George AFB, California, but the nose gear pivot pin worked loose, allowing the wheel to swivel at random, so he diverted to Edwards, which had a longer runway.
[13] On approach, at a high angle of attack, the fighter exceeded its flight envelope, and, too far into stall condition, lost directional control with fatal results.
These scenes were inserted in the movie The Hunters, starring Robert Mitchum and Robert Wagner, in the movie X-15 with actor Charles Bronson playing the pilot, and in the made for TV film Red Flag: The Ultimate Game, although in The Hunters and in Red Flag: The Ultimate Game, the aircraft supposedly represented were respectively an F-86 and an F-5E.
