F-111 mach 3?

[topol-m]

hey ggtharo, please do not correct people when they know more about a plane then you abviously do.

sometimes it is even for you better to not write anything.

 

this what i talk about was recorded on the hud cam, no harder evidence can prove me wrong, not even the biggest dick in the world.

 

the pilot himself did not even realised that he pulled so many g´s. he actually passed nearly out, but the fear of death kept him awake.

 

i am still surching for the tape though

 

LOL No need to be rude, man. Tharos is difficult to argue with sometimes ;) but has a great knowledge in the military aviation sphere.

About the discussion: There is not a single aircraft that can withstand such huge G`s and i cannot possibly know can they even be achieved with any of the modern fighters. It will surely break apart at this values. The onboard instruments including the hud do not have a scale that can show such high values of G loading. 30-40G can be reached by missiles. The trained pilots can withstand 9 G or even little more for a short time with special suits. It is possible to survive 40G but for a second or less with high possibility of various injuries (such G loading, or even bigger occures in car accidents and a lot of people survive - the lucky ones). :thumbup:

[sobek]

i am still surching for the tape though

 

Until you show it, i see myself forced to say, consider yourself happy that paper (or forum background) does not blush. ;)

 

such G loading, or even bigger occures in car accidents and a lot of people survive - the lucky ones

 

The human body is much more capable of withstanding g-force along the front-back axis than the top-bottom axis. Also, 'eyes in' force can be tolerated better than 'eyes out'.

Edited May 30, 2009 by sobek

[GGTharos]

The tape is on youtube and you can't see the accelerometer on it. It also blancs out at the critical moments where the aircraft is pulling 15g (read it again, 15 ;) ).

 

That aircraft's airframe was bent from the ordeal, and as such it could no longer be maintained (access doors wouldn't close properly, etc etc) so it has become a museum piece - specifically it is mounted on a stand in front of an airbase.

 

Edit: The HUD tape is here:

 

More interesting is that the guy isn't G-LOC'ed after this pull, which basically precludes the possibility of a 40-g pull for that length of time. Further, the amount of time that he pulled for is more consistent with a 15g pull than a 40g pull. We're talking about an aircraft that's aerodynamically limited to a max turn-rate of 21DPS at 9g - at 40g, if we were to assume a linear relationship, you'd get 84DPS, or basically a square corner. That is NOT what happened. ;)

Edited May 30, 2009 by GGTharos

[sobek]

Edit: The HUD tape is here:

 

I cannot, for the love of god, see any readable numbers on that tape. For what it's worth, it could be a 9g turn as well.

[GGTharos]

LOL No need to be rude, man. Tharos is difficult to argue with sometimes ;) but has a great knowledge in the military aviation sphere.

 

Why thank you Sir :D

 

About the discussion: There is not a single aircraft that can withstand such huge G`s and i cannot possibly know can they even be achieved with any of the modern fighters. It will surely break apart at this values. The onboard instruments including the hud do not have a scale that can show such high values of G loading. 30-40G can be reached by missiles. The trained pilots can withstand 9 G or even little more for a short time with special suits. It is possible to survive 40G but for a second or less with high possibility of various injuries (such G loading, or even bigger occures in car accidents and a lot of people survive - the lucky ones). :thumbup:

You can withstand many, many g's without blacking out if it's for a very short amount of time. The more g's, the shorter the time - for example, you can withstand up to 12g for about 4-5 sec. This is because your brain has an oxygen supply for this long without your heart pumping fresh blood into it - however, any longer and you're out. The more g's you pull, the less time you have because the acceleration drains the blood from your brain and so that 4-5 sec reserve is not there any longer.

 

I'm attaching an image of a STOHL curve that shows how g-tolerance works in people. This curve is for the average person, not a pilot with training + g-suit and other aids. The time is onset time (ie. how much time you take until you read n g's)

[GGTharos]

Exactly. What you can do is time some of this stuff. At 15g and 500kt you might see a 20-25DPS instantaneous turn rate.

 

I'm including a page with the most optimistic sustained turn rates for the F-15 from the -1. You can turn faster than this if you make it an instantaneous turn.

 

I cannot, for the love of god, see any readable numbers on that tape. For what it's worth, it could be a 9g turn as well.

[hitman]

This convo is turning me on.

[Vekkinho]

15G is a great result for a fighter plane...hard to beat or impossible with what human technology and knowledge can produce. This makes 30 G a bit too much to be true, it would break the airframe apart or if plane makes it to the home plate it would be grounded permanently after landing.

 

Now let's say 30G was the case with this F-15, let's say it was clean and running on fumes. Weight numbers of a clean, bingo F-15C are in neighborhood of 13.000kg so when you multiply it with 30 you'd lose some wings and break it's spine...

[borchi_2b]

vekkinho, did you see the videotape?

 

this plane never flew again after that hapend.

 

ok, gg, you found one of the 2 viedos. but there was one on youtube or some other video hoster without the voice and with a way better videoquality in which you could see the g meter in the hud clearly. maybe they removed it, but i have been searching for it for 2 days now and it is not in my linking list.

 

never the less, normaly the planes are designed for a max g performance.

ok, lets talk about bussiness here.

 

do to the fact that military and civil planes are built to fly manned, they have to withstand certain tests.

 

a boeing 777 for example has a max break load, we talk about a max g untill the wings fall apart, of 11g´s.

it is limmited to a max flight performance of abaout 3 g´s, which is a 1/4 of the max possible g´s before the plane breaks.

 

when we talk about military planes ok, then we have about the same ratio, but most western fighters were designer with a max load that is 5 times greater then the max g performance.

 

so lets take the f15c, ok.

the eagle is limited to 9.5 g´s in flight.

5 times that ammount would sum up to what ?

47.5 g´s max.

this is about the g force that is needed to break the wings of the airframe.

 

so it is possible to pull an eagle to 40g´s. not for long at all, maybe just a tiny fraction of a second but most people would thing "ohh this plane cannot pull such g´s cause it breakes apart way earlier", which is complete bullshit.

that it will not stay in service after such loads that a fact that we do not have to discuss cause it is obvious.

 

one last thing to the g load.

 

in eruope we have a very nice piece of fighter. all should know about that plane by now allready. the eurofighter is limited to a g load of +12, do to the fact that even most of the pilots cannot withstand higher g´s for long althugh they were a nice invention done by the germans :-), which is called libelle, one of the best anti g suits ever built so far.

the EADS production and testteams figured that the eurofighter could withstand about 17g´s for a long term without having serious damage done to the airframe.

so lets not talk about that down to 0 cause it is not what i actually wanted to piont our with the fact of the eagle.

 

what i wanted to point out is, that a mach 1.7 is not impossible at low levels at all, although the airframe would probably suffer from the heat that builds up, but we have not been in a f111, none of us so far i guess.

 

i just think that it is a possible flightenvelope of the f111, not more and not less.

just imagine, only replace the engines of the tornado with the eruofighter engines which have about twice as much power then the tornado engines have and you could easily go mach1.4 with a panavia tornado at low level. this is not much less then m1.7 and i am sure, with engines that are srtong enough and the thrust to weight ration in a huge advantage set for the planes envelopes, the m1.7 is a realisic number

[GGTharos]

vekkinho, did you see the videotape?

 

this plane never flew again after that hapend.

 

ok, gg, you found one of the 2 viedos. but there was one on youtube or some other video hoster without the voice and with a way better videoquality in which you could see the g meter in the hud clearly. maybe they removed it, but i have been searching for it for 2 days now and it is not in my linking list.

 

You can CLEARLY see that once the aircraft is over-g'ed, the HUD tape is useless because the recording head comes off the tape ;)

 

never the less, normaly the planes are designed for a max g performance.

ok, lets talk about bussiness here.

 

do to the fact that military and civil planes are built to fly manned, they have to withstand certain tests.

 

a boeing 777 for example has a max break load, we talk about a max g untill the wings fall apart, of 11g´s.

it is limmited to a max flight performance of abaout 3 g´s, which is a 1/4 of the max possible g´s before the plane breaks.

11g's when it's what? Empty? I can maybe buy that. I also know a business jet such as this will see its fuselage fall apart at 5g's under certain circumstances (already happened!), and you can rip the tail off pretty easy without needing too many g's. Why it's happened in reality, recently, too.

 

Your assumption that it's 'limited to 1/4 of g's before it breaks' is BS. Look at the F-15-1 and you'll see an OWS-deprived F-15 is limited to a max of 4g at MTOW, and that's symmetrical gs.

 

when we talk about military planes ok, then we have about the same ratio, but most western fighters were designer with a max load that is 5 times greater then the max g performance.

The ratio is 1.3, not 4-5. You over engineer the airframe to reasonably withstand 33% more g than its 'structural design limit' so that you can actually reach that limit in most flight conditions without breaking up.

 

so lets take the f15c, ok.

the eagle is limited to 9.5 g´s in flight.

9.0g. Warning at 8.2. Do you even have the -1?

 

5 times that ammount would sum up to what ?

47.5 g´s max.

this is about the g force that is needed to break the wings of the airframe.

 

so it is possible to pull an eagle to 40g´s. not for long at all, maybe just a tiny fraction of a second but most people would thing "ohh this plane cannot pull such g´s cause it breakes apart way earlier", which is complete bullshit.

that it will not stay in service after such loads that a fact that we do not have to discuss cause it is obvious.

And to further demonstrate what a load of hot air you're blowing, the F-15 in the longeron accident broke apart at 3g. Not 30, not 40, 3. This is already 1/3 or 1/4th of the structural design limit, so you're telling me it lost 10x more strength than it should have?

Further, if it DID pull 40g's 'for a tiny fraction of a second' you would never know it, and the tape would never show it, so what are you talking about still?

 

one last thing to the g load.

 

in eruope we have a very nice piece of fighter. all should know about that plane by now allready. the eurofighter is limited to a g load of +12, do to the fact that even most of the pilots cannot withstand higher g´s for long althugh they were a nice invention done by the germans :-), which is called libelle, one of the best anti g suits ever built so far.

the EADS production and testteams figured that the eurofighter could withstand about 17g´s for a long term without having serious damage done to the airframe.

so lets not talk about that down to 0 cause it is not what i actually wanted to piont our with the fact of the eagle.

No eurofighter will withstand 17g for anything resembling 'long term'. In order to do this you have to pay a hell of a lot more for the materials, they MUST be heavier, and so on and so forth. It makes zero sense to give it a capability that cannot be used. 12g is an over-g limit ... the FCS limits it to 9 ;)

The reasons for these things should be obvious, and for someone who claims to know about the F-15 than me, I find your knowlege in this whole aviation matter severely lacking, even compared to the little that I know.

Edited June 3, 2009 by GGTharos

[topol-m]

a boeing 777 for example has a max break load, we talk about a max g untill the wings fall apart, of 11g´s.

it is limmited to a max flight performance of abaout 3 g´s, which is a 1/4 of the max possible g´s before the plane breaks.

 

when we talk about military planes ok, then we have about the same ratio, but most western fighters were designer with a max load that is 5 times greater then the max g performance.

 

so lets take the f15c, ok.

the eagle is limited to 9.5 g´s in flight.

5 times that ammount would sum up to what ?

47.5 g´s max.

this is about the g force that is needed to break the wings of the airframe.

 

1. What`s the source of the info you have about "fighters were designer with a max load that is 5 times greater then the max g performance" or the 9.5G-47.5G ratio.

2. Could you explain how can a modern fighter could perform a meneuver with such high G? The only way i see it possible is to mount some huge rocket engines creating thrust perpendicular of the aircraft flying direction and start them when its flying with max speed. Pretty ugly picture...

3. Even if in theory the fighter could withstand the 40G for a fraction of the second it wouldn`t be able to jump from lets say 9G directly to a 40G and keep 40G for a fraction of a second without passing throght 15, 20, 30...Gs first, unless it is some alien technology that allows it to perform some 90+ degree turn instantaneously. So it will break apart even at lower than 40Gs due to high G loading for seconds.

[vanir]

Any non-bypass engine can overspeed (runaway rpm). A combination of compressor and inlet design decides what speed. Something like an A-4 for example will overspeed in a shallow dive at 1.2 Mach or thereabouts. An F-4 it'll be more like 2.3 Mach. Generally for obvious reasons aircraft are engineering so as to reduce likelihood of overspeeding at normal operating speeds. This gets more difficult as operating speeds get higher, where the airframe capabilities may outweigh those of engine/inlet design.

 

The most graphic example of this is the MiG-25 which has an airframe limit of 2.83 Mach and an engine restriction of 2.5 Mach. Normal maximum speed is 2.35 Mach although 3.2 Mach has been recorded in service (by NATO intelligence recording as well as Soviet figures), however during flights exceeding 2.5 Mach engine destruction is virtually inevitable due to uncontrolled overspeeding. Experienced Foxbat pilots advise maximum throttle should never be used at high Mach except in emergencies due to this tendency.

 

The MiG-31 has similar airframe design limits (2.83 Mach maximum is official limit in common with MiG-25 but Foxhound airframe is much better built for these speeds with twice titanium content and general improved construction). It has no such overspeeding problems with the Aviadvigatel engines which are designed to sustain cruise at speeds up to 2.83 Mach and reportedly are very reliable (yet to fail in bench testing after several hundred thousand hours according to manufacturer).

 

As far as design for high speed flight goes the F-111 is built more like a MiG-25 than a MiG-31. The variable sweep structure is not as strong as the F-14 but overall is a less bulky type so it has a higher speed capability than the Tomcat, but the Tomcat was chosen because it was stronger for sustained carrier operations (the F-111 was originally going to use the Pheonix weapon system as a 2.5 Mach carrier fighter).

 

At high altitude the F-111 has the same troubles as any contemporary in terms of airframe heat dissipation, how much friction heat it can handle (or produces in the first place) and engine overspeed limitations. Plus there is all the same interpretive qualities to judging its best high speed condition as other types.

"Maximum speed" in an Eagle under service conditions is a dash anything over 2 Mach, which is a remarkable speed for a fighter carrying missiles and a lot of avionics, but not much else. Phantoms that aren't actually stripped down for a dedicated speed test are unlikely to see much above 1.8 Mach. That 2.35 maximum cruise of the Foxbat (with BD engines) is pretty much uncatchable as it is.

It's a similar story with the F-111. I've spoken to Aardvark pilots too, on RAAF bases and they boasted proudly, it's as fast as an F-15, it can get faster than 2 Mach flying clean. That's the way they put it too.

 

At low altitude you've got other issues. Critical Mach is a much lower figure. The very fastest supersonic aircraft in the world at low altitude, can do 1.2-1.3 Mach at sea level. The F-111 is one of these.

Aircraft like the Hornet are also considered very fast at low altitude because they can make 1.4 Mach not very far from sea level (but certainly not at sea level). The F-111 also fits into this category. Generally an aircraft is considered exceptional if it can make supersonic at sea level at all, most second generation strike and fighter aircraft can't. The Foxbat can't.

Most of the reason for this is the fact the F-111 was designed as an air superiority fighter type with an emphasis on speed (the Foxbat for example is an interceptor type with an emphasis on altitude).

 

This 1.7 Mach figure is obviously either, at altitude above ground level and not sea level (ie. say 2000' above sea level but 100' above ground level maybe), or it is a figment of somebody's imagination. Regardless of flight experience in one of these aircraft between us forumites, the key issue would be that the aircraft engineering itself cannot support the claim.

 

You might as well say an ice cream cone can do Mach 1.5 at sea level, nobody's ever flown one supersonic so how could they know? Well it's just unreasonable to suggest, plainly.

 

The 3 Mach figure at altitude is fictional. No other way to put that. Total poppycock.

 

Maybe someone was having a lend of the OP. Maybe he's just making it up. There are no examples to support the contention, and the engineering certainly doesn't. 3 Mach is a huge jump from 2.5 Mach in terms of airframe stresses and heating, which is a *very* liberal, rather conditional speed figure for the Eagle and the Aardvark in the first place. By very liberal I mean it's unlikely you'll ever hear of that kind of speed in normal service outside of an extreme situation probably involving the destruction of the aircraft.

 

Mach 6 for a Blackbird btw is also pure fiction. The fact it could sustain 3.2 Mach cruise was an astonishing achievement (and has more than a little to do with the altitude it is cruising at). Some pilots have individually inferred that speeds of closer to 3.5 Mach were possible (actual recorded figures are 3.2 dash for YF-12A and 3.2 sustained absolute for SR-71A).

 

This contention about high speed flight being in any way parallel to high speed ground travel is just preposterous. High speed flight is achieved in concordance with altitude. It has totally different rules than putting a wider valve timing and uprated fuel supply in your Volvo (which then needs a compression change, head flow/manifolding examination and distributor recurve).

Edited June 8, 2009 by vanir

[Groove]

I thought this is a thread about the F-111...

[vanir]

I thought my post directly addressed the speed claims of this "F-111" using a reasonable comparison of contemporary technology, though the subject of engine overspeeding did come up in the thread but is again a reasonably associative consideration.

 

I do most certainly agree this business about F-15 "g" capabilities is walking headlong beyond the topic, a relevant point is one thing but a sustained discussion about turning ability and F-15 video footage seems to warrant a new thread.

 

 

please don't feed me to the pigs

[topol-m]

 

please don't feed me to the pigs

 

LOL :megalol:

[Vault]

when we talk about military planes ok, then we have about the same ratio, but most western fighters were designer with a max load that is 5 times greater then the max g performance.

 

Borchi whilst I can't speak for the US, in the UK and I think the EU the safe working load (SWL) of all metals is 1:3 of the tensile critical working load (MBL), IE if a metal component is rated with a SWL of 9G the metal component will reach its minimal critical tensile point at 27 G, the 5:1 SWL factor you state is used for soft materials like harness webbing because they're more prone to wear and tear. Are you sure that an F-111's airframe has a 1:5 G SWL factor?.

 

*Edit* Forgot to state that the figures above are UK civilian saftey system regulations and not military.

Edited June 15, 2009 by Vault

[DarkWanderer]

but most western fighters were designer with a max load that is 5 times greater then the max g performance.

Famous F-15 case with 15G pullout rendered the airframe irrestorable. The tail part of the plane was twisted.

[nscode]

But that isn't 5 times max performance :)

[GGTharos]

The entire airframe was warped, not just the tail - laterally and longitudinally. It resulted in access pannels not closing well, engine bores no longer being a good fit for the engines, etc etc ... in short, unmaintainable even though it could still fly!

 

Famous F-15 case with 15G pullout rendered the airframe irrestorable. The tail part of the plane was twisted.

[Mugenjin]

But that isn't 5 times max performance :)

 

I think that was what DarkWanderer was trying to convey? or not? :D

[nscode]

I think that was what DarkWanderer was trying to convey? or not? :D

 

wooops. got quotes confused :D lots of homework these days:D

[Scrape]

1.Most of the reason for this is the fact the F-111 was designed as an air superiority fighter type with an emphasis on speed (the Foxbat for example is an interceptor type with an emphasis on altitude).

 

2.the key issue would be that the aircraft engineering itself cannot support the claim.

 

3.You might as well say an ice cream cone can do Mach 1.5 at sea level, nobody's ever flown one supersonic so how could they know? Well it's just unreasonable to suggest, plainly.

 

4.The 3 Mach figure at altitude is fictional. No other way to put that. Total poppycock.

 

5.Maybe someone was having a lend of the OP. Maybe he's just making it up. There are no examples to support the contention, and the engineering certainly doesn't. 3 Mach is a huge jump from 2.5 Mach in terms of airframe stresses and heating, which is a *very* liberal, rather conditional speed figure for the Eagle and the Aardvark in the first place. By very liberal I mean it's unlikely you'll ever hear of that kind of speed in normal service outside of an extreme situation probably involving the destruction of the aircraft.

 

6.Mach 6 for a Blackbird btw is also pure fiction. The fact it could sustain 3.2 Mach cruise was an astonishing achievement (and has more than a little to do with the altitude it is cruising at). Some pilots have individually inferred that speeds of closer to 3.5 Mach were possible (actual recorded figures are 3.2 dash for YF-12A and 3.2 sustained absolute for SR-71A).

 

7.This contention about high speed flight being in any way parallel to high speed ground travel is just preposterous. High speed flight is achieved in concordance with altitude. It has totally different rules than putting a wider valve timing and uprated fuel supply in your Volvo (which then needs a compression change, head flow/manifolding examination and distributor recurve).

 

1. Can you verify that the F-111 although given the F designation wasn't flown as a tactical bomber. Air Superiority? The-111? Where did they put the missiles?

 

2. Can you explain how this is true? Usuing data and math.

 

3. Is there a point here? Nothing plain about it.

 

4,5. Great job reading the first two lines of the first post. How did this thread start again?

 

6. I was speculating (stated in post) how about an intelligent counter point?

 

7. The parallel wasn't about engines, but its nice that you tried to sound smart here, but the analogy was to aerodynamics versus frame structuer. Not speed on the ground vs high speed flight. Can you elaborate your point how aerodynamics only affects objects that are off the ground? And what is wider valve timing?

 

Have a good debate make a good argument. With respect.

[GGTharos]

1. Can you verify that the F-111 although given the F designation wasn't flown as a tactical bomber. Air Superiority? The-111? Where did they put the missiles?

 

Maybe you aren't aware, but they did try the AWG-9 and AIM-54 on it ...

 

Here's a quote from wikipedia for you:

 

The beginnings of the F-111 were in the TFX program, an ambitious early 1960s project to combine the United States Air Force requirement for a fighter-bomber to replace the F-105 Thunderchief with the United States Navy's need for a long-range carrier-based Fleet Air Defense fighter to replace the F-4 Phantom II. The fighter design philosophy of the day concentrated on very high speed, raw power, and air-to-air missiles.

 

They were trying to build a jack-of-all-trades ;)

 

 

2. Can you explain how this is true? Usuing data and math.

 

You'll kill your engines. That's all there is to it. As you increase speed, engine temperature increases to the point where you warp/destroy/cause fire. If you attempt to go mach 3 with those engines, you can pretty much say bye bye to them before you ever reach that speed.

THe F-15's arguably more advanced engines get used up if you use the v-max switch to reach mach 2.5. You have a useful one-minute transient from M2.3-M2.5, after which a lengthy engine inspection is required, IIRC, and if you go any longer the engine just gets replaced because it is no longer structurally sound. Again, IIRC.

 

6. I was speculating (stated in post) how about an intelligent counter point?

 

Okay. Your speculation is based on nothing. :)

The X-15 did Mach 6.7, and returned burned up. There was no design flaw issue in this case - heat simply does this sort of damage, period - and IIRC its ability to withstand temperature was better than the SR-71's. The SR-71 is built to withstand a mach 3.2 cruise, which means the skin heats up to a given temperature and holds there. At mach 6.7, you heat the poor thing up quite a bit more.

 

A simple, very simple way to figure out how much more ... E=1/2mv^2. Velocity squared. ;)

People like to say 'the difference between mach 1.3 and mach 1.7 isn't big' ... well yes, actually, it darn well is. It is 'I'll fry your engines and destroy your airframe' big ... so your Mach 6 speculation is utterly baseless.

 

 

7. The parallel wasn't about engines, but its nice that you tried to sound smart here, but the analogy was to aerodynamics versus frame structuer. Not speed on the ground vs high speed flight. Can you elaborate your point how aerodynamics only affects objects that are off the ground? And what is wider valve timing?

 

Have a good debate make a good argument. With respect.

 

It affects them in the same way is affects aircraft - thus you have cars shaped in a certain way and not another. See formula one cars for one, or that supersonic dragster, I forget its name.

[sobek]

that supersonic dragster, I forget its name.

 

Thrust SSC :)

[Scrape]

GGTharos, I'm aware of the missile fires from the F-111, I was referring to an operational loadout. As far as I know there were no approved SCAL loads with Air to Air missile included for the US. You missed my scarcasm when is came to #7. I'm well aware of the properties of aerodynamics on cars, my comments were directed to vanir and what he had posted.