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"PENTAGON WORKING TO GIVE F-35 JSF NUCLEAR-STRIKE CAPABILITY"
On May 13, 5:05 am, "Kurt R. Todoroff"
wrote: In article , "Ken S. Tucker" wrote: On May 13, 1:03 am, frank wrote: On May 12, 5:13 pm, Andrew Swallow wrote: Let me guess, corrections invited. Today, software and computer enhanced flying is well known to a military pilot. (The rumor that the F-22's crossing the International dateline caused the computer - via software glitch - to crash is a typical example). In a sense, software removes pilots burden. When was software first used? I'm guessing it was 1st used to automatically control the F-111 wing sweep. Ken Ken, The pilot commanded the F-111 wing sweep position via a lever that was mounted underneath the left canopy rail. It hung underneath the rail and was hinged to flip up (outboard) to stay out of the way. The pilot would move his left hand from the throttles up to the handle, grab it and rotate it down, then push it forward or pull it back. Forward equals wings move forward, back equals wings move back. When the handle was stowed in the outboard spring loaded position, it was friction locked from moving forward or back. The wing sweep control handle was connected via manual cable (not electrical cable) to the high-lift control system, which in turn controlled the wing sweep position. Wing sweep position was directly proportional to wing sweep handle position. The two hydraulic systems provided control power to move the wings. The wing sweep actuator was a non-reversible system that prevented the wing sweep position from being affected by airloads. The forward position was 16 degrees leading edge sweep. The aft position was 72.5 degrees leading edge sweep. The wings moved at 3.8 degrees per second. The aircraft placard G limits were -3.0 to +7.33 symmetric when the wings were stationary. This were later changed to -1.5 to +7.33. During wing sweep, the placard G limits were 0 to +4.0 symmetrical. Assymmetric G during wing sweep was prohibited. The F-14 Tomcat used a more sophisticated wing sweep system. The pilot's right throttle contained a five position thumb switch (button) on the inboard side which was very similar to the trim button on the stick except that unlike the trim button which was spring loaded to the center position, the pilot could place the wing sweep button in any of the five positions. The positions we Forward: Sweep wings forward Aft: Sweep wings aft Down: Sweep wings to sixty degrees (I think) Up: Autosweep Center: No command In the Autosweep mode, the Central Air Data Computer (an analog device) commanded the wing sweep position according to Mach number, using a pressure altitude bias. Furthermore, regardless of wing sweep mode, the CADC would not allow the wings to be over-sped. If the pilot manually commanded the wings forward, the CADC would stop the wing sweep movement when they reached the computed Maximum Safe Mach value. If the pilot left the wing sweep control in the center (no command) at takeoff instead of up (Auto) then the CADC would start to sweep the wings aft during aircraft acceleration to prevent overspeeding the them. The forward position was 20 degrees leading edge sweep. The aft position was 68 degrees leading edge sweep. The wings moved at 15 degrees per second. The aircraft placard G limits were -1.5 to +6.5 symmetric even during wing sweep. Grumman improved on the F-111's wing box to gain this capability, unfortunately at the expense of a substantial amount of extra weight. Variable geometry wings proved to be a great asset to the F-111 in the interdiction/strike role. In my opinion it provided no benefit to the F-14 in the A/A role. The F-15A empty weight was 28,500 pounds. The F-14A empty weight was 40,000 pounds. Most of this was due to the VG component of the aircraft. These two aircraft are nearly the same length. The F-14 used a simple fly-by-wire throttle. The interconnect between the throttles and the engine fuel controls was electrical. The F-16 uses a similar FBW throttle system, that compliments its FBW flight control system which which GD borrowed from the F-111. GD used the Vark's triple channel FBW flight control system, added a fourth channel, and added a few more features (ie. limiters, some of which were eventually added to the Vark's FBW FCS) and then used it in the F-16. Kurt Todoroff Thanks Kurt, We (wife and I) studied your post carefully, For me, you put me into the F-111 and F-14 cockpit. In the early 70's there was a kind of renaissance in aviation, (I was in the bearing business, SKF), and the F-111 was maturing, as were the F-14, F-15, and the fighter competition, F-16 and F-17 was hot stuff. The B-1A was suffering from bearing problems, the C5-A had wing strength issues. I agree with your F-14 thesis, the VG weight penalty was not worth the performance gain, especially in view of the F-18, but also recognize the subtle diff where the F-111 and then B-1 is concerned, as you point out, in the long strike mission. Regards Ken |
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