A new perspective on “Back and to the Left” in the Z-film

[Charles Collins]

I dislike viewing the images associated with all of this. They are just unsettling to me. So I have avoided this thread for the most part. But I saw something on a Smithsonian channel show called “Air Disasters” that reminded me of this subject and wanted to share the essence of it. It involves the reasons that a supersonic passenger jet (SST) crashed shortly after takeoff in France years ago. What happened was a piece of metal laying on the runway cut one of the tires as the jet was traveling around 200 mph just before it’s takeoff speed. The tire exploded and a piece of the tire struck the underside of the wing (which was also a fuel tank). The piece of tire didn’t penetrate the tank. But it set off a shockwave which did rupture the tank at its weakest point. The fuel caught fire, an engine was disabled and the plane crashed shortly thereafter due to insufficient thrust to gain altitude. Anyway, the shockwave causing the fuel tank to rupture reminded me of some of the things that have been said about JFK’s head exploding. And I thought this thread might be an appropriate place to share.

[Brian Roselle]

I dislike viewing the images associated with all of this. They are just unsettling to me. So I have avoided this thread for the most part. But I saw something on a Smithsonian channel show called “Air Disasters” that reminded me of this subject and wanted to share the essence of it. It involves the reasons that a supersonic passenger jet (SST) crashed shortly after takeoff in France years ago. What happened was a piece of metal laying on the runway cut one of the tires as the jet was traveling around 200 mph just before it’s takeoff speed. The tire exploded and a piece of the tire struck the underside of the wing (which was also a fuel tank). The piece of tire didn’t penetrate the tank. But it set off a shockwave which did rupture the tank at its weakest point. The fuel caught fire, an engine was disabled and the plane crashed shortly thereafter due to insufficient thrust to gain altitude. Anyway, the shockwave causing the fuel tank to rupture reminded me of some of the things that have been said about JFK’s head exploding. And I thought this thread might be an appropriate place to share.

This may be relevant and is an interesting scenario, I may have to see if I can find the story.

I wonder about their conclusion though if the tire part ejection happened just before takeoff (and not in supersonic flight), it sounds related to an old physics trick question on how fast the top of a tire goes relative to the ground/or its axel. I believe the answer is only twice the velocity. If so, that would put a broken off chunk of rubber at 400 mph (2x200mph) which is subsonic. I think the axel/airplane would have to be going close to 400 mph before takeoff to have a chunk ejected at supersonic speed. (That is if I'm thinking about it right and they didn't add on some speed from an explosion which may be what they did). But I would think a chunk of rubber at 400 mph would still be able to do some damage (heck fast foam ultimately took out a space shuttle), so I'm wondering if a physical collision could have come into play here instead of a shock wave. I may be saying this based on how I was also a little surprised how little physical disruption was done to a house of cards by the 50 cal BMG mach 3 shock wave only an inch or so away in that one video.

The other thing about the shock wave is that it stops being formed when the bullet or fragment goes subsonic. In the JFK case it might be worth checking on what the estimates were for the bullet velocity after going through the occipital bone area which might have put it subsonic, but the other thing is that the speed of sound tends to go up in liquids and solids vs gas, so I would expect the speed of sound to go up in tissues.

[Charles Collins]

This may be relevant and is an interesting scenario, I may have to see if I can find the story.

I wonder about their conclusion though if the tire part ejection happened just before takeoff (and not in supersonic flight), it sounds related to an old physics trick question on how fast the top of a tire goes relative to the ground/or its axel. I believe the answer is only twice the velocity. If so, that would put a broken off chunk of rubber at 400 mph (2x200mph) which is subsonic. I think the axel/airplane would have to be going close to 400 mph before takeoff to have a chunk ejected at supersonic speed. (That is if I'm thinking about it right and they didn't add on some speed from an explosion which may be what they did). But I would think a chunk of rubber at 400 mph would still be able to do some damage (heck fast foam ultimately took out a space shuttle), so I'm wondering if a physical collision could have come into play here instead of a shock wave. I may be saying this based on how I was also a little surprised how little physical disruption was done to a house of cards by the 50 cal BMG mach 3 shock wave only an inch or so away in that one video.

The other thing about the shock wave is that it stops being formed when the bullet or fragment goes subsonic. In the JFK case it might be worth checking on what the estimates were for the bullet velocity after going through the occipital bone area which might have put it subsonic, but the other thing is that the speed of sound tends to go up in liquids and solids vs gas, so I would expect the speed of sound to go up in tissues.

The way I envision it, is the speed of a piece flying off of the tire circumference would depend upon the diameter of the tire (think how changing tire diameters would affect the speedometer on a car or truck), the speed of the plane relative to the runway, plus any added velocity created by the explosion of the tire. And if I remember correctly, they stressed the fact that the tire literally exploded. Also they pointed out that the fuel tanks were completely full for the long flight across the Atlantic Ocean (similar to a human head being full of semi-liquid matter). And I don’t know if supersonic speed was any part of their computer model showing that the shockwave (if that is the exact word that they used - I’m not sure because I kept being distracted while trying to watch the show). What was clear to me was that the impact of the tire piece didn’t actually penetrate the fuel tank, and that the rupture of the tank was in a different location and the metal was bent outwards. When we compare the Concorde SST situation to the JFK headshot it would be more like a blow to the head (that didn’t penetrate the skull) causing a concussion severe enough to blow the other side of the skull out. I doubt that there has ever been a documented case where that actually happened. What did happen to JFK was the bullet did penetrate the skull and it appears to me that a combination of a bullet fragment(s) and a shock wave from the impact of the bullet caused the other side of the skull to be fractured and blown out. Comparing the two very different cases, what strikes me as important is that the potential magnitude of the force of the shock wave inside a sealed container full of liquid (or semi-liquid) material can be great enough to rupture the container without the blow even penetrating it. And that the Zapruder frames 313, and a few immediately following it, showing the violent outflow of matter from JFK’s skull is visual evidence of the force of the shock wave inside his skull. Some people might have a difficult time understanding how a relatively small bullet can cause such an explosion. Just like they might have a similar time understanding how a piece of tire could do the damage that it did to the fuel tank of the Concorde plane.

[Charles Collins]

A look at a Wikipedia article shows some more specific information:

The Concorde ran over this piece of debris during its take-off run, cutting its right-front tyre (tyre No 2) and sending a large chunk of tyre debris (4.5 kilograms or 9.9 pounds) into the underside of the left wing at an estimated speed of 140 metres per second (310 mph).[2]: 115  It did not directly puncture any of the fuel tanks, but it sent out a pressure shockwave that ruptured the number 5 fuel tank at its weakest point, just above the undercarriage.


https://en.wikipedia.org/wiki/Air_France_Flight_4590


Wow, a 10-pound chunk of tire at 310 mph. That was a significant amount of energy. And I think that since the shockwave was in the liquid fuel, the tire chunk didn't need to be at supersonic speed (much like a boat on a body of water doesn't need to be going the speed of sound to create a wake).

[Brian Roselle]

A look at a Wikipedia article shows some more specific information:

The Concorde ran over this piece of debris during its take-off run, cutting its right-front tyre (tyre No 2) and sending a large chunk of tyre debris (4.5 kilograms or 9.9 pounds) into the underside of the left wing at an estimated speed of 140 metres per second (310 mph).[2]: 115  It did not directly puncture any of the fuel tanks, but it sent out a pressure shockwave that ruptured the number 5 fuel tank at its weakest point, just above the undercarriage.


https://en.wikipedia.org/wiki/Air_France_Flight_4590


Wow, a 10-pound chunk of tire at 310 mph. That was a significant amount of energy. And I think that since the shockwave was in the liquid fuel, the tire chunk didn't need to be at supersonic speed (much like a boat on a body of water doesn't need to be going the speed of sound to create a wake).

I had totally forgot about that Flt 4590 incident, but when you mentioned it, I recalled it a little bit and how it was debated in court and was part of the demise of the Concord.

Thanks for the link, it refreshed my memory on what happened and how the Concord was different vs other jets in its take off angles and required take off (V1) speeds etc.

An interesting but sad story, it sounds like once the crew hit V1 speed while still on ground during takeoff, there was basically nothing they could do to on the ground or in the air to prevent a cataclysm of some type after their tire blew and caused that internal wing damage (fuel tank and wires) as a result of hitting a previous plane’s piece of cowling metal on the runway.

OK, here is an interesting coincidence based on what the article mentions. Get your tomatoes ready. A thrust reverser cowl door of the number 3 engine of a Continental Airlines basically lost a piece of metal. This ultimately was the cause of the Concord tire blowout and the whole incident.

Years of debate ensued over a thrust reverser. A thrust reverser directs a jet of its exhaust in the same direction the plane moves, in a forward direction, to slow down and help stop the plane’s forward motion. It typically runs continuously over a short period of time (but not just an extremely short burst or impulse) to help the plane to almost stop.

I think there has been a lot of debate over the years about the idea of some thrust reversal effect in another case. It's not exactly the same but just a coincidence I noticed. You can now throw your tomatoes at me