Airplane faster than a speeding bullet?

J

Jack Arnott

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Jan 29, 2011
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My Uncle Ed died on the first of this month. His funeral was last Tuesday, near where I grew up in the Little Belt Mountains in Montana. It was my first time being a pall bearer.

Of course there were many stories after, and before the funeral.
One was about the time he shot at the Air Force.

Growing up in Montana we had a huge Air Force presence. Might not seem like a likely scenario, but with thousands of Nukes, there needed to be somewhere to put them (that didn't matter to the rest of the country), and the northern border was closer to the USSR than anywhere. We had one of the motherfuckers three miles from where I lived.

There was a natural animosity between the ranchers/farmers and the Air Force. For one, the Air Force pilots had to log a certain number of hours each month. So they would be out all over Montana, "practicing". They developed a fondness for sneaking up on the agriculturists, and frightening them. This was when they were still allowed to go beyond the speed of sound. The pilots would fly low over farmers or ranchers on tractors, or cowboys on horses. Because they were going over the speed of sound, one could not hear them coming, and would of course be very scared when the sonic boom went off right over them. Then they would watch the planes fly off.

My uncle was having problems with a coyote in his sheep, and was carrying his 30-06 on his tractor to try and see if he could come across him while running the harrow in his field.
(This never works. The coyotes can smell a gun, and will be long gone.)
So, of course the Air Force picked this time to startle my Uncle. He was so pissed off. Usually he was very good about gun safety, but his emotions were so tweeked he pulled out the gun after getting over the initial shock and shot at the plane. (He was also a quite good marksman, so he was lucky that it was an elusive target and he apparently missed.)

When telling this at the dog park today, my friend thought that the plane would outrun the bullet. This seems counter-intuitive to me.
Most of you seem to know more about both subjects than myself. Couldn't he have hit the plane?

Regards, Jack
 
Re: Airplane faster than a speeding bullet?

I looked up the numbers for the maximum muzzle velocity of a 30-06 and it seems to be about 3500 ft/ second. If the jet was supersonic it would have to be going a minimum of about 1200 ft / second. The F4 phantom (which I just guessed since it was from that era) had a max speed of approximately 2x the speed of sound. I thought about trying to figure out at what point plane would meet bullet until I read this about the speed of sound:

This is 1,236 kilometres per hour (768 mph), or about one kilometer in three seconds or approximately one mile in five seconds.

Taking into account the plane was probably a mile and a half away by the time your uncle got his bearings and grabbed his rifle, the trajectory arc of a 30-06, crosswinds, moving target, and my own experience with 30-06 on open sights, I think it would be a pretty tough shot.
 
Re: Airplane faster than a speeding bullet?

Jack,

The muzzle velocity of the unladen sparrow, er... 30-'06, is about 2700 fps with a 180 grain bullet out of a 24" barrel which is normal for folks who don't mind a little recoil, but perhaps a little heavy for coyotes. The speed of sound is about 1116 feet per second in 65° dry air. Montana has a higher altitude, let's say 3,000' above sea level, so while the speed of sound is unchanged the bullet loses a little less velocity at range. We don't know how fast the plane was going, but let's say exactly Mach 1.

Problem number one with hitting the plane is that, while the bullet may start out faster than the plane, by the time it gets out to a range that is meaningful on the scale the plane operates at it has slowed significantly... it is only doing just over 1400 feet per second at 1000 yards.

Problem number two is bullet drop, by the time the bullet gets to that 1000 yard mark it has dropped nearly 400".

Problem number three is timing. It takes the bullet 1.54 seconds to travel 1,000 yards. Even if the plane were that close, it is a very fast moving target that will be very small. Your uncle would have had to know exactly where the plane would be 1.5 seconds after pulling the trigger, would have to perfectly estimate wind and have already sighted in the gun for a 1000 yard drop, and would have to make his shot perfectly. I suspect none of those things happened.

I like to shoot skeet, a 4" target moving at about 80 feet per second that I am trying to connect with an 8" cloud of shot moving at 1200 feet per second at a distance of 20-60 yards. My scores are usually in the low 30s, meaning I broke about 30-40% of my targets. Considering how critical leading the target properly is with that kind of velocity mismatch, I am of the opinion that it would be impossible with projectile and target moving at close to the same speed, even ignoring the issue of whether the bullet would ever get there.

Cool story, though!
 
Re: Airplane faster than a speeding bullet?

Bennet.
I might be reading your post wrong, but just to be clear: Speed of sound changes with altitude due to the changed density of the air. Extreme example: sound in water=super fast because of water being a lot denser than air in general.
BTW, most jets will be unable to reach their maximum speed close to the ground. 1,1 mach is however typical for a low-level bombing run by a fighterbomber, as I understand it.

Regarding shooting down planes with hand guns (it does happen in war-time): I think the more usual scenario would be that a whole platoon of guys spot the plane coming and just fire away and empty their AK-47s right as it's passing over, and a few get in a lucky shot. WWII tail gunners apparantly had a little math to do, also, due to the guns behaving a lot differently than when firing straight forward.


All this talk of guns and shooting made me forget my manners: Jack, my condolences to you and your family.
 
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Re: Airplane faster than a speeding bullet?

kristianjohnsen said:
I might be reading your post wrong, but just to be clear: Speed of sound changes with altitude due to the changed density of the air. Extreme example: sound in water=super fast because of water being a lot denser than air in general.
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Kristian,

Air pressure is not the same as air density, the two have a more or less equal and opposite effect for our purposes and cancel. The effect on the speed of sound of air pressure is minute compared to that of temperature, and even to that of humidity. From 1-5 atmospheres of pressure there is only a 0.5 m/sec increase in the speed of sound. From 0-100% humidity there is about a 2.5 m/sec increase in the speed of sound. Meanwhile, going from -13°C to 47°C there is a 40 m/sec difference in the speed of sound. Many (often aviation) graphs of speed of sound vs. altitude also include temperature and therefore confuse the issue.

http://www.sengpielaudio.com/calculator-speedsound.htm
http://en.wikipedia.org/wiki/Speed_of_sound#Dependence_on_the_properties_of_the_medium
http://www.phy.mtu.edu/~suits/SpeedofSound.html
 
Re: Airplane faster than a speeding bullet?

Bennett Prescott said:
Kristian,

Air pressure is not the same as air density, the two have a more or less equal and opposite effect for our purposes and cancel. The effect on the speed of sound of air pressure is minute compared to that of temperature, and even to that of humidity. From 1-5 atmospheres of pressure there is only a 0.5 m/sec increase in the speed of sound. From 0-100% humidity there is about a 2.5 m/sec increase in the speed of sound. Meanwhile, going from -13°C to 47°C there is a 40 m/sec difference in the speed of sound. Many (often aviation) graphs of speed of sound vs. altitude also include temperature and therefore confuse the issue.

http://www.sengpielaudio.com/calculator-speedsound.htm
http://en.wikipedia.org/wiki/Speed_of_sound#Dependence_on_the_properties_of_the_medium
http://www.phy.mtu.edu/~suits/SpeedofSound.html
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Hi Bennett.

Thanks for your clarification.

Regarding the density, my guess is that the air at altitude has a different mix of elements than the air at ground level - which would contribute to varying density.

Regarding top speed of a fighter jet: I think this is a really complicated calculation which would include considerations like varying aerodynamics, abundance of oxygen to burn and temperature of said oxygen into account. Again, this is a layman's guess, here!
 
Re: Airplane faster than a speeding bullet?

Although we do have planes that outrun that bullet today, not likely then. Having to lead the target accurately would be difficult at those speeds, and the size of the plane is relatively small. He might have gotten a lucky shot in, but likelihood of a hit is so small as to be nil (all things considered.) Considering the physics and facts, you have significantly better odds with the Mega Ball lottery.

Stuart
National Aeronautics and Space Administration
 
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Re: Airplane faster than a speeding bullet?

Stuart Pendleton said:
Considering the physics and facts, you have significantly better odds with the Mega Ball lottery.

Stuart
National Aeronautics and Space Administration
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Ha ha! This is the best reply ever. Didn't know you worked for everyone's boyhood dream... that is cool.

P.S. I would be much more worried about where the round came down than whether it hit the plane, but probably not an issue in the fields of Montana.
 
Re: Airplane faster than a speeding bullet?

Thanks Bennett. Been here for 23 years now. I am the sign off official for the release of NASA software outside of NASA. My days are filled with patent attorneys, export officials, and world class researchers, of which I am not one. Not exactly everyone's boyhood dream, but my father ran the sheet metal shop before me and knew the original 7 astronauts. He let me sit in John Glenn's capsule seat while they were working on the capsule. That WAS a dream for a child back then. The facility where they trained for the Apollo landing is about 1000 yds from where I am now, the facility where they learned to dock in space in in view, and I am surrounded by wind tunnels. We actually share a runway with the Air Force and they fly stealths overhead all the time.

After all the years here, I sometimes forget that it IS a cool place to work. Thanks for reminding me, and I can face the rest of the day now. ;-)

PS: I will trade jobs with anyone that works for Clair Brothers.....(somedays...)
 
Re: Airplane faster than a speeding bullet?

How does he know that he actually missed? Did he expect the plane to explode from a single shot-of that size?

He could have hit it in any number of places and it would continue to fly just fine.
 
Re: Airplane faster than a speeding bullet?

Wow, thanks for all the wonderful responses, and on topic too. You all win two interwebs.

30.06 bullet faster than jet.. difficult shot tho...
JR
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Short, and nailed it.

Taking into account the plane was probably a mile and a half away by the time your uncle got his bearings and grabbed his rifle, the trajectory arc of a 30-06, crosswinds, moving target, and my own experience with 30-06 on open sights, I think it would be a pretty tough shot.
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Good response, and suppositions, but he did have a scope. Wonder if that would make it easier or harder than open sights, in this case?

Problem number one with hitting the plane is that, while the bullet may start out faster than the plane, by the time it gets out to a range that is meaningful on the scale the plane operates at it has slowed significantly... it is only doing just over 1400 feet per second at 1000 yards.

Problem number two is bullet drop, by the time the bullet gets to that 1000 yard mark it has dropped nearly 400".
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I had not anticipated the slowing of the bullet.
The drop yes.

which is normal for folks who don't mind a little recoil, but perhaps a little heavy for coyotes.
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WTC is wrong with you? Heavy for coyotes? If there is anything to be learned from a sound providing forum it is that overkill is barely enough. My dad's 30-06 did have one of those recoil pads on it, but my uncles and mine were both brass plates. Mine is a 1917 Infield, with 5" of barrel removed, with the open sights, and a 4x installed. Now my (mean) grandmother did have a much smaller Reminton 25, which was fine for shooting deer in her garden from her bedroom window, (kept it under her bed), and when she was 90 was bragging about shooting five baby racoons out of her kitchen window with three shots, the previous morning, to the dismay of many of the dinner guests.

All this talk of guns and shooting made me forget my manners: Jack, my condolences to you and your family.
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Thanks Kristian. It was sad, though not tragic. The last time I saw him in August he was in decline. He still had his love for nature though. It was really inspiring that a sunset on the red bluffs above our ranch that he had seen thousands of times meant even more to him now. Not less. I kind of notice the same thing with flowers blooming in the spring. It seems more magical every time it happens.

Regarding shooting down planes with hand guns (it does happen in war-time): I think the more usual scenario would be that a whole platoon of guys spot the plane coming and just fire away and empty their AK-47s right as it's passing over, and a few get in a lucky shot. WWII tail gunners apparantly had a little math to do, also, due to the guns behaving a lot differently than when firing straight forward.
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I was guessing that the tailgunners used empirical evidence. As in, watching the tracers and seeing how they were responding/reacting.

Although we do have planes that outrun that bullet today, not likely then.
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The lotto quote is right on. But, although planes are faster now, they were allowed to go faster then. It has been a long time since going over the speed of sound has been a norm, even in rural Montana.

P.S. I would be much more worried about where the round came down than whether it hit the plane, but probably not an issue in the fields of Montana.
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Even in Montana, there is never a shot into the air that I would not consider dangerous. So many stories of stray bullets. My dad was very adamant about not shooting without a backdrop for your shot. So I would go with your initial concern.

How does he know that he actually missed? Did he expect the plane to explode from a single shot-of that size?
He could have hit it in any number of places and it would continue to fly just fine.
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Exactly. Leaves a lot of room for the story to grow with time.
(I don't think he expected anything, just a pissed of reaction.)
You do have a lot of TV to watch though. Everything blows up there, with the least bit of prompting.

(Which JR points out in the next response.)

Regards, Jack
 
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