On glove vanes and pitch (not a request for GV inclusion)

[captain_dalan]

I've never done a speed run in the F-14 actually, and since i've been flying the A exclusively after it came out, i never ran an intercept faster then mach 1.2 or so. Recently, in a now closed topic, the role of the glove vanes was mentioned and how they helped by adding lift and reducing stability at high mach numbers, allowing the jet do do 7.5g turns at mach 1.4+. If i understood the discussion correct, this means that without them, at say mach 1.6, no matter how hard we pull on the stick, the tail just can't generate enough down force-pitch authority to allow for 7+g's to be generated in a turn. Is this stick-stab deflection behavior actually simulated in the current implementation? I would test, but unfortunately i'm not likely to get any sim time in the next few days......
Cheers!

[draconus]

17 hours ago, captain_dalan said:

Is this stick-stab deflection behavior actually simulated in the current implementation?

Idk but currently you can pull all you want at M1.7 to either break it or blackout - no limits.

[Quid]

Probably not a definitive answer, but the V-N charts for the B/D show a projected structural limit out to 7.5g for 55,985lbs.  Once the aircraft's lift limit reaches 7.5g and flat-lines at the projected structural limit, the line never curves back down to imply a speed where the aircraft cannot at least hit the projected limit of 7.5g in any of the charts, even at 35,000 feet and 2.4M.  But, that's just reading a chart; SME input would probably help.  At the same time, I'm not sure how many B/D Tomcat crews decided to get the plane to 1.6M and pull to see if they could overshoot their NATOPS limit...

Edited June 22, 2021 by Quid
Clarification

[Hummingbird]

IIRC the vanes allowed 7.5 G sustained turns at very high speeds at altitude, i.e. it didn't have anything to do with control authority, just lift vs drag vs thrust. 

Edited June 22, 2021 by Hummingbird

[captain_dalan]

Ah, thanks for the input everyone!

[captain_dalan]

13 minutes ago, Hummingbird said:

IIRC the vanes allowed 7.5 G sustained turns at very high speeds at altitude, i.e. it didn't have anything to do with control authority, just lift vs drag vs thrust. 

 

I don't think a sustained turns performance above a few g's is possible, glove vanes or not. At least not according to the V-N diagrams XI-9-5 and XI-9-6. I don't see how you can turn  4g at 25kft and just tad   bellow 3g at 35kft (between mach 1.3 and 1.7) into 7+g. But then again, as @Quid mentioned,  we don't see the available lift drop either, so once it reaches the structural limits (in these charts around 7g) it never falls back.

[sLYFa]

The F-14 had a bunch of maneuvering limits in the supersonic speed range. These were not due to a performance or control authoritiy limitation but for stability reasons. The glove vanes helped a little with that as they countered the center of lift shift occuring at supersonic speeds. 

[Hummingbird]

4 hours ago, captain_dalan said:

I don't think a sustained turns performance above a few g's is possible, glove vanes or not. At least not according to the V-N diagrams XI-9-5 and XI-9-6. I don't see how you can turn  4g at 25kft and just tad   bellow 3g at 35kft (between mach 1.3 and 1.7) into 7+g. But then again, as @Quid mentioned,  we don't see the available lift drop either, so once it reaches the structural limits (in these charts around 7g) it never falls back.

 

Maybe at 5,000 ft, where sustainable load factor is already at 7.1 G at 0.83 mach. Perhaps the glove vanes allowed up to 7.5 G above 1.0 mach. But without an EM diagram to show it, it's just guessing.

 

It's also possible that it allowed up to 7.5 G instantaneous at higher altitude and speed when the wings were fully swept.

Edited June 23, 2021 by Hummingbird

[captain_dalan]

30 minutes ago, Hummingbird said:

 

Maybe at 5,000 ft, where sustainable load factor is already at 7.1 G at 0.83 mach. Perhaps the glove vanes allowed up to 7.5 G above 1.0 mach. But without an EM diagram to show it, it's just guessing.

 

It's also possible that it allowed up to 7.5 G instantaneous at higher altitude and speed when the wings were fully swept.

 

Yeah, but you won't be going much past 1.4 if that at 5000ft....
As for the 2nd part, this is how  i assumed they worked, by unloading the tail. But the charts don't seam to show it.

3 hours ago, sLYFa said:

The F-14 had a bunch of maneuvering limits in the supersonic speed range. These were not due to a performance or control authoritiy limitation but for stability reasons. The glove vanes helped a little with that as they countered the center of lift shift occuring at supersonic speeds. 

Well, moving the center of lift further forward would make the plane less stable in the pitch.