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Silverbolt

Brazilian Air Force cracking windows

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Yesterday during the flag change cerimony, two Mirage 2000 passed too low at supersonic speed and end up cracking windows of the Parliament, Supreme Court and President's palace.

 

 

i say , well done!

 

here are the links:

 

http://www.youtube.com/watch?v=-qhc2lXCT9c

 

 

Edited by Silverbolt
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Haha great ! Hoping that it has awakened them from their slumber !

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next time one party or the other uses our servicepersonel's benifits as a political tool the airforce should do this over Washington DC.... ;)

 

next time one party or the other uses our servicepersonel's benifits as a political tool the airforce should do this over Washington DC.... ;)

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Well worth the price! They were low those were big windows you don't have to supersonic to bust windows that low.

Edited by MAKO69
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As cool as that was...it will be a lot less cool if they end up losing their wings for it.

 

FC

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Well worth the price! They were low those were big windows you don't have to supersonic to bust windows that low.

 

but i hear something i believe is an sonic boom blink.gif

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A sonic boom, especially a close one, is different then when a jet comes onto your location suddenly. The biggest thing you'll notice is a 'whump' sound/feel. Like someone dropped something HEAVY nearby, or you're standing next to your favorite loudspeaker putting out the bass...that 'thump' you feel in your chest with each beat of that speaker is what a sonic boom feels like.

 

The other thing you'll notice on a real supersonic run...there will be NO aircraft sound before the aircraft is directly overhead. No air rush, no noise from the intakes, nothing.

 

Based on what I see and hear...I'd say they were supersonic or at least transonic.

 

FC

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:yikes:

Is it me or they indeed were supersonic? Watch the 2nd plane vs sound delay (might be due to camera/codec/whatever)

I hope they will came out of it

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oh yea!! :yikes::grin:

 

although we all know they're standing tall in front of their Wing Commander about now.....

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The other thing you'll notice on a real supersonic run...there will be NO aircraft sound before the aircraft is directly overhead. No air rush, no noise from the intakes, nothing.

 

 

Back in '85 when I was a wee munchkin, I got to witness a pair of Mirage IIIOFs do this and it's silence was what really made an impression on me the most. Being 5yrs old and not knowing how sound worked, to see all these people at the airshow covering their ears at the very fast, very silent dart threw me. Then the sound hit and I entered a world of pain. Poor pilots got into a tonne of trouble when the moment of transonic flight made it on the news and several glass houses on nearby farms were completely demolished during their flypast. :lol:

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Back in '85 when I was a wee munchkin, I got to witness a pair of Mirage IIIOFs do this and it's silence was what really made an impression on me the most. Being 5yrs old and not knowing how sound worked, to see all these people at the airshow covering their ears at the very fast, very silent dart threw me. Then the sound hit and I entered a world of pain. Poor pilots got into a tonne of trouble when the moment of transonic flight made it on the news and several glass houses on nearby farms were completely demolished during their flypast. :lol:

 

 

heh heh

 

On Midway we had a standard air show routine (excuse me: "Firepower Demo") for whenever it was needed for visiting dignitaries. The flight demonstration package would launch and then everyone would come up on deck to watch the show, er, demonstration.

 

Now, on a carrier with a nice big deck and the island on the starboard side, everyone naturally turns to port. This tendency is reinforced by the airwing guys who all turn to port and watch. So everyone (except the airwing guys who glance over their shoulders every now and then....) are looking out to port as the opening fly-past of two Phantoms approach from starboard, on the deck, supersonic (and not just barely!) in full zone 5 and blast overhead in a thundering pass and zoom climb to the stratosphere while dumping the full load of flares as they rocket on by.

 

absolutely shattering! :yikes::lol:

Edited by Typhoid

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:yikes:

Is it me or they indeed were supersonic? Watch the 2nd plane vs sound delay (might be due to camera/codec/whatever)

I hope they will came out of it

 

Official report by FAB( Brazilian Air Force) says that the first pilot( the one who cracked those windows) was at 1100 km/h. Not supersonic, but it was fast enough to create a shock wave over the wings/fuselage. Or, as some people says, only the pressure's difference inside/outside the building created by the plane itself could crack those big windows. For me, doesn't matter, it was COOL! rofl.gif

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Assuming an OAT of 30°C, 1100km/h would be about M0.87 - which would certainly not make those windows crack!

Assuming ISA-conditions of 15°C, we're still at M0.89 or so.

 

 

You can wave a hand-full of BS-flags on that!

 

 

 

You won't hear such a *bang*, unless the aircraft travels at M0.99 or faster.

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The bang could be an artifact of the recording... the phone couldn't keep up with the rapid upramp of volume from the high speed, non-supersonic pass, and just recorded it as 'bang'.

 

In addition, I've witnessed multiple times of B-1Bs setting off car alarms... just on takeoff because the vibration was so strong.

 

However, most large panes of glass on modern buildings are designed to take a significant amount of differential pressure before they crack... I'm not sure a pass of less than 0.95 Mach would cause such an event.

 

FC

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The bang could be an artifact of the recording... the phone couldn't keep up with the rapid upramp of volume from the high speed, non-supersonic pass, and just recorded it as 'bang'.

 

In addition, I've witnessed multiple times of B-1Bs setting off car alarms... just on takeoff because the vibration was so strong.

 

However, most large panes of glass on modern buildings are designed to take a significant amount of differential pressure before they crack... I'm not sure a pass of less than 0.95 Mach would cause such an event.

 

FC

 

those buildings were built back in the 50's those are not even bulletproff good.gif

 

most damage building, the supreme court had its entire front destroyed, however the presidential pallace only had minor damage i think because those are bulletproof.

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Assuming an OAT of 30°C, 1100km/h would be about M0.87 - which would certainly not make those windows crack!

Assuming ISA-conditions of 15°C, we're still at M0.89 or so.

 

 

You can wave a hand-full of BS-flags on that!

 

 

 

You won't hear such a *bang*, unless the aircraft travels at M0.99 or faster.

 

You are correct Toryucool.gif, but you forgot just one detail. I don't know for sure, but, at mach 0.87(or 0.89), the air around the wing(or even the fuselage, due to the "area rule" shape) could go supersonic, if the speed is bigger than the critical mach number for the Mirage-2000, creating a shock wave. And, don't forget, as Silverbolt said:

"those buildings were built back in the 50's,those are not even bulletproff "

PS: about the window.... still worth it! grin.gif

 

 

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A friend of mine told me that visiting BONEs at Nordholz NAS, Germany, have thrown-over cows during low-passes :grin:

But then again, the Bone has four engines - each of them more powerful (and thus propably emitting more sound-energy) than the single M53 of the M2K.

 

A fun-fact in terms of sound-energy:

 

The CJ610 at our engine-lab (a civil, de-afterburnered version of the J85, an F-5 engine) produces 60kW of sound-energy alone at max power.

So there's an equivalent power of 80HP of SOUND emitted from this - tiny - turbojet-engine.

 

 

 

 

The issue with the glasses breaking is that there needs to be relatively strong pressure-spike in order to excite the glasses beyond their max stress-deflection. It's basicly a function of the glasses' thickness and it's area.

The shockwaves that are experienced by transonic (at M< 1.0) objects are relatively weak, because it's just local air decelerating into subsonic-flow.

 

Shockwaves created by an object that flies at transonic speeds that are greater than M 1.0 are a different beast and usually stronger, with stronger pressure-differences associated.

The PX-difference is a function of the freestream Mach-number and the angle of deflection.

 

The aircraft are both clearly past the camera when the bang occurs, with the second aircraft being faster (smaller Mach-angle) than the first.

 

 

Mach-numbers will vary locally with temperature. As the air-temperature is not homogenously distributed (as in "the same temperature everywhere"), there will be warmer and colder spots of air.

 

An example:

An aircraft traveling along at 336m/s @ 15°C is flying at M0.99 - a temperature-drop to 7°C will turn the same air-speed into exactly M1.0 - the speed of sound changed by 4m/s (about 7-8 Knots) by just a change in air-temperature of 8°C.

The Mirage might have gone in and out of M1.0 by just flying at the same air-speed, as temperature-differences of 5-10°C can easily be achieved by different ground-colours.

Then there's wind-shear and moisture-distribution, which also have an effect on the speed of sound and// or the Mach-number.

 

A combination of changes can and will get you supersonic without intent in a heartbeat.

 

 

______________

Transonic: Condition of airflow around an object that has both, subsonic and supersonic portions - usually between M 0.8 (below= purely subsonic) and M 1.3 (above = purely supersonic). The transonic-region is different on each aircraft-type and will differ considerably with AoA.

Edited by Toryu
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My 2 cents.

There are two reasons why i say, that it was no supersonic speed which the Mirages had flown.

first, a supersonic boom sounds different

second, the people on the place are still standing on their feets.

 

 

To first. Here in Germany (East Germany) we heared in the cold war time very often the supersonic boom. It was a short and dry bang. It was an unmistakable and very diffrent sound than that what i have heared in the video.

 

To second. during my military time i (and my unit) was a "victim" of a very low high speed overfly of a pair of Su-22 fighterbombers. They came along the street on which our column was marching and they came from the back, so that we not heared, that they came. And when the were above us the noise and the pressure on the lunge was so overwellming, that i fall on my butt, like the most of the guys in the column.

 

 

But is nice to see windows breaking in real. :good::cool:

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Columbia broke the sound barrier directly over my head once, at ~30,000 ft. At that distance the double boom was enough to suck the air from your lungs, although no windows were broken because the area had long ago been hardened to such things. Had it been at low alt, though, like under 1000 ft, it would've shattered everything and possibly induced cardiac arrest in frail people!

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i (and my unit) was a "victim" of a very low high speed overfly of a pair of

Su-22 fighterbombers. They came along the street on which our column was

marching and they came from the back, so that we not heared, that they came. And

when the were above us the noise and the pressure on the lunge was so

overwellming, that i fall on my butt

 

 

Had a very simillar experience with an F-4F a few miles offshore in the vacinity of RAF Leuchars a few years back.... sneaky Jerry git! :punish:

 

 

 

Craig

Edited by fallenphoenix1986

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Columbia broke the sound barrier directly over my head once, at ~30,000 ft. At that distance the double boom was enough to suck the air from your lungs, although no windows were broken because the area had long ago been hardened to such things. Had it been at low alt, though, like under 1000 ft, it would've shattered everything and possibly induced cardiac arrest in frail people!

 

Technicly, it didn't "break the sound barrier" as it overflew. It came in hypersonic from orbit and was supersonic at 30000ft. The double-bang associated with the fwd and aft shockwaves (there may be some shockwaves in-between) can always be heard as soon as the aircraft flies M 1 or faster. It doesn't "break" anything (I guess you know this anyway, but people in general seem to be a bit confused about that).

The *bang* results of all the sound-waves being compressed into a shock-front that travels at the speed of sound (it can't go any faster by definition...) - hence the cone-shaped shock-front at speeds faster than M 1. The second reason for the bang (it's related) is the huge pressure-difference from before the shock to after the shock (pressure, and temperature rise over the shock-wave, local Mach-number goes down).

 

The intensity of the shock depends mainly on two things:

- the deflection-angle (if the angle gets too large, the fwd shock detaches)

- the Mach-number

 

The Space Shuttle has a very blunt nose, as it's designed to travel at very high (hypersonic!) Mach-numbers during it's fairly short time of atmospheric flight. The thermal-loads of hypeersonic flight (and re-entry, of course!) dictate blunt-shapes, as sharp and pointy shapes can not dissipate the thermal-loads and will fail (this is subject to scientific research atm). The consequence of this blunt shape is a very strong fwd shock. The aft shock is also increased by the shape of the Shuttle, as there's no afterbody-assy that "reunites" the airflow, but a very suden transition from "engine compartment/ laval-nozzles" to "free airstream". This also results in a pretty strong shock-wave - much stronger than on fighter-sized airplanes.

 

 

IF the Mirages were supersonic can not easily be determined.

You might notice the lack of a double-bang. That might result in the geometry involved, though, as a airplane of 15m length, travelling at 330m/s will only take 0.04545 seconds to pass overhead, which possibly is too short of a timeframe for the camera to proccess.

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