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GalmOne

Safe, Sustained, Max and Ultimate F-14 load limits

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Some sources I read say that the USN made the Tomcat's safe load limit +6.5g. Another thread here http://combatace.com/topic/72262-what-was-the-initial-allowed-g-limit-for-the-f-14a/, which is a little short, still provides some insight on the F-14's g-loads, but only the ones imposed by the USN for long service life.

 

Were there any official USN sustained, max and ultimate load limits listed for the F-14A or did pilots just have to know the lame +6.5 g's and fly by that? For example, the F-15A's max and ultimate load limits were something like +7.33 g and +12 g respectively. From what I've heard from other sources, pulling +7.x G's in an F-14A was a non-issue. Also what are the negative g's that an F-14A can pull?

 

Thanks!

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About G pressure one od the Iranian pilots put 11G on tomcat while a dogfight

It made the rudders and wings some cracks and it took two year to rebuild it but the pilot and the copilot got body problems because of that

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The actual ultimate G is a function of fatigue-life-history and gross-weight. The more fatigue, the sooner the break-up threshhold is reached. Dito on grossweight.

Military airplanes are usually built with that in anticipation, so that the mathematical "ultimate" figure (1.5x limit-load) is nowhere near the actual ultimate figure - except maybe for an aircraft close to it's design lifte-time.

 

Anyway, other factors do also play decisive roles in fatigue-progress, such as corrosion and airloads that were not expected (see F-18 and their early troubles with the vertical tail).

 

Even though an aircraft might live through a significant g-overshoot with no superficial damage, the life-time will be drastically shortened (a couple of hundred hours).

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Thanks for the input, gentlemen. Though, Toryu, what I meant was the design ultimate loads. I.e. when it comes out of the factory fresh and new. I suppose I would have to draw one of those Goodman diagrams we did in class. Except for an entire airplane rather than just a landing gear trunnion pin!

 

EDIT: Although I just remembered that everywhere I read, they say that the introduction of the Tomcat meant that the Navy had a plane that had a "21 percent increase in acceleration and sustained g-force, 20 percent increase in rate of climb, 27 percent increase in maneuvering capability, and a 40 percent improvement in turning radius." Are they just referring to the F-4J Phantom? If so that means that when the Tomcat just entered service, the max G must have been higher than 6.5 since the F-4J was rated at just about that.

Edited by GalmOne

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There's what the plane is capable of, and there's what the service has placed as limits. As mentioned, it's not about what the plane can take so much as how long it will last given regular usage at those limits.

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Does anyone have screenshots of g-load, V-n diagram or turn rate diagrams for the F-14 that look like the picture below? I find that being able to compare the planes at every interval of the flight envelope can help me picture what a plane can do.f-4e-3.jpg

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Ah ok so the energy management diagram isn't showing up but I found one EM diagram which is supposedly for the F-14. It looks to be either for an F-14 at very high altitude or a very high heavily-loaded Tomcat or both. Take a look below. If anyone knows where to find the rest of these graphs, let me know! The thread I took this from is here (post 89): http://www.worldaffairsboard.com/military-aviation/56690-fighter-performance-actual-plane-analysis-6.html

 

23038d1291038300-fighter-performance-act

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I don't think it's a hi-alt EM-diagram, as the Mach-limit is at 1.5, which would indicate medium altitudes (say between 10kft and 20kft).

With a max sustainable load of 2.0g @ M0.8, this looks like a rather heavily loaded aircraft, propably at max wing-sweep as well.

 

 

EDIT: Although I just remembered that everywhere I read, they say that the introduction of the Tomcat meant that the Navy had a plane that had a "21 percent increase in acceleration and sustained g-force, 20 percent increase in rate of climb, 27 percent increase in maneuvering capability, and a 40 percent improvement in turning radius." Are they just referring to the F-4J Phantom? If so that means that when the Tomcat just entered service, the max G must have been higher than 6.5 since the F-4J was rated at just about that.

As with anyhing, the correct answer would be "depends" - and it really does!

20% higher sistained g would be roundabout 8.4g if we consider the max-max an F-4J could sustain (about 7g if relatively clean and relatively light). It doesn't say under which circumstances and at which configurations these numbers were achieved.

 

The 6.5g limitation on the Tomcat was for life-time saving only.

Edited by Toryu

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Such a fatigue-fighting measure is pretty sad considering it just eats away at maximum capabilities. This is why finding the collection of graphs to which the one above belongs would really help in getting an idea of the F-14's turning capabilities. If only the US Navy had graphs like the USAF.

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Considering 90%+ of flight time is training/peacetime work, it makes sense.

In war, max limits are allowed. There's no "better not break 6g trying to dodge this missile or there could be a lengthy post-flight inspection!"

 

If you allow max limits for all flight time, the planes wear out faster. It's just math.

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6.5Gs limit was necessary to give the planes some more time to live.They had to carry a huge radar, they had to spend long time in the air, they had to pound themselves with arrested landings/launches, and to top it all off, they had to carry a big weapon.They had to cut something down.I've heard a few stories of Tomcats pulling 9-10Gs.Here's one:

 

http://instapinch.com/?p=1003

 

The safe limit, I'd say it is 6.5, or maybe a little above that (according to Grumman's specs, but those could even be talking about a clean plane with 50% fuel, so...).Max Gs are, I guess, placed to 9-10,  and sustained should be at about 7-8, maybe?

Edited by thodouras95

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I don't think the A model could sustain 7-8. It just didn't have the engines for that. Instantaneous, sure, but to sustain that many in a turn you need some power behind you.

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The A model Turkey could sustain 7g at just above combat weight or less at lower altitudes, and at medium to high subsonic speed.

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