"Say, That Looks Big Enough to Fly a B-25 through!"

[beamjockey]

I'm reprinting this from the comments section on james_nicoll's blog, where, in a discussion of planes hitting tall buildings, ethelmay writes, intriguingly:

Tangent: I once met a guy who had flown a B-25 UNDER the Eiffel Tower. He and his wife were friends of my father and stepmother.

The spaces at the base of the Eiffel Tower appear to be defined by semicircular arcs. Their diameter is 74.24 meters, for a radius of 37.12 m.

A North American B-25 has a wingspan of-- well, some online sources say 66 feet. Some say 67 feet. Some say 68. I found one that says 118 inches, but it turns out to be describing a 1:7 scale model. Let's take 68 feet, or 20.7 m, for a half-span of 10.35 m.

Presuming your transgressive* friend is skilled enough to fly his bomber down the centerline of the archway (as projected onto the ground; a plumbline dropped from the highest point of the arch would touch this), and presuming the wingspan is the dominant constraint (e.g. the twin tailfins are not tall enough to intersect the arch if the wingtips clear it), what is the maximum altitude at which the wings safely pass through?

This height is the length of a vertical side of a right triangle, whose horizontal side is a half-wingspan in length with a vertex on the arch, and whose hypotenuse is one radius in length with one end at this vertex and the other on the centerline at the ground.

Pythagoras teaches us that the maximum height is therefore

SQRT(37.12^² - 10.35²) = 35.6 meters, or 115 feet.

This answer is a bit too simple. I have treated the semicircle of the arch as if it were in a vertical plane. As anyone can see, the arch is actually tilted, so viewed from the side the tower's base appears to be a trapezoid. So height of the semicircle, and the maximum safe height for the bomber, are actually lower by a factor depending on the angle of the trapezoid's sides. Improving this result is left as an exercise for any student able to determine this angle.

I have also neglected the calculation of minimum height, which might involve gathering data on the umbrellas over vendors' pushcarts and such.

I am sure your friend, as a methodical and safety-minded aviator, took all these things into account in making his own calculations.




* Yet completely awesome.

Comments

[msminlr.livejournal.com]

From everything I have read and heard about aviators of that generation, I am completely sure that someone at least *TRIED* that.

It is reassuring to hear that, mathematically at least, it *WAS* feasible.

[vicarage.livejournal.com]

Much the same as the 139ft - aircraft height of the Hunter flying through Tower Bridge (https://en.wikipedia.org/wiki/Hawker_Hunter_Tower_Bridge_incident) then, which has a nice painting (http://www.aviationartworld-combatjets.com/html/tower_bridge_hunter.html). With a square profile, much easier to assess the problem too!

[brooksmoses]

You should also notice that the difference between the maximum height and the apex of the semicircle is about 1.5 meters -- about five feet. The tail on a B-25 appears higher than that, and so it -- rather than the wingtips -- is actually the limiting factor if the plane is reasonably close to the middle of the arch.

(That's going to be even more true when we consider the tilt of the arch -- although in the photo it appears to me that they are actually vertical semicircles projected onto the tilted plane of the structure, so the vertical calculation is correct.)

[ethelmay.livejournal.com]

I just checked Dad's letters, and I misremembered slightly: it was a B-17. The guy who did it is called Ken Sherman. Oh, wait, I missed that he was actually in Paris when he wrote this letter, and writes "We ... looked at the Eiffel Tower. ... Ken Sherman is reputed to have flown a B-17 bomber under that tower, and I wanted to see if he could have, and how easily. The opening is semi-circular, a bit over 300 feet wide and about 160 feet high, so a B-17, having a wing span of about 100 feet, could have easily fit."

I don't know where Dad got the Eiffel Tower measurements, but as a WWII navigator himself and a Boeing engineer later, I think he probably got the plane number correct.

There are of course several people who've flown under the Eiffel Tower -- one guy (not Ken) did it during a dogfight with a German plane.

[beamjockey.livejournal.com]

Thanks for telling us more of the story!

[vicarage.livejournal.com]

Here is a 54' wingspan Mosquito doing the Eiffel Tower. http://www.tallyhorestoration.com/wp-content/uploads/2013/01/405990_137696999722314_750786460_n.jpg

[dragonet2.livejournal.com]

ffffffffffff..... k.

[vicarage.livejournal.com]

Some background
http://www.ww2aircraft.net/forum/aviation/rcaf-409-nfs-3639-3.html

[dragonet2.livejournal.com]

And I saw another aviator quote recently (not sure where) where someone asked him if he could fly a fighter jet through something and he replied, "I probably could, but I want to keep flying at this job for a long time, so I won't."

My father was a bomber pilot, retired on B-52s. He once stated that one of the things they fight against is creativity and thinking outside the box. Because it leads to fewer broken planes.

[beamjockey.livejournal.com]

And, I'd guess, fewer broken landmarks.

[neowolf2.livejournal.com]

There is a famous case of a US fighter pilot in WW2 who chased a German plane under the Eiffel Tower. The German was trying to escape but the desperate ploy did not work.

He (the US pilot) just recently died., age 92.

http://www.dailymail.co.uk/news/article-2533373/WWII-fighter-pilot-flew-THROUGH-Eiffel-Tower-dies-Virginia-aged-92.html