Forum: F-16 Design & Construction

Hi all,

Got a question. While I've been watching this fine kinda emotional video (btw who knows the gentle music?) http://www.youtube.com/watch?v=PzGZOlR-RIM I noticed at 1:14 - on the pilot's penalty board following phrase: "Do not go supersonic + Overspeednig the tanks". So, what is actual speed limit for the Viper with it's tanks considering both 300gal and 370gal ones (and may b the CFTs). I suppouse that must be strictly related to the altitude. Could something bad might happen to the tanks/aircraft if someone accidently breake that limit?

Please lit it up a little
Thanks

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Depends on whether the tanks are full or empty.

ViperDude

I thought, that capacity of the fuel tanks is related yes but to the g-load, not tho the speed? Does it matter how much fuel left in your tanks when lets say you want to go supersonic while the tanks are still there all in all?... Drag still remains the same whether it's full or empty. Isn't it? Not the actual weight is a factor but drag. So, my question is.. where's the limit?

300 gallon and 370 gallon tanks are designed for 600 kcas to 1.6 mach. Combined with other stores, the speed limit may be less. Full or empty makes no difference to speed limit. 600 gallon tanks are subsonic. g limit does change with fuel usage.

Speed limits for fuel tanks are not set by drag, but usually by flutter, which is a catastrophic divergent oscillation.

That make me almost clear. Thanks

John

So, it appears that Viper can't fly supersonic at sea level with tanks.. because that means flying 650 -660 or more kcas at low and very low altitude. Correct?

And by the way. Is there any similar restrictions in case CFTs?

Correct. 600 kcas at sea level is 0.907 mach standard day. Don't know about CFT, after my time.

What would happen if the limit were exceeded a small amount? No one knows, but probably nothing. Limits have safety margins, simply because some one some day will exceed the limit. A gross violation of the limit, say diving at 700 kcas down to near sea level, given the right tank fuel load, could easily be catastrophic.

Theoretically, the jet handles fine at 640C if you accidentally take the tanks there at sea level. A bl50 over the ocean in the winter can easily overspeed the tanks, without the pilot noticing - one might just a little spanking when you get home and see it in the debrief. All theoretical of course.

Oh how I miss the 129.

Forum: F-16 Design & Construction

Tanks speed limit?