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If that sounds like a ludicrous question it's because I believe it is, but here is why I'm asking.

My grandfather flew B-24s in WWII and there was something of a local legend that he once flew a crew-laden Liberator under Bixby Bridge (near Big Sur along the CA coast). Here is a short video of the bridge:

I say no way. Aside from the the idea of a trained military aviator so recklessly risking crew lives (not to mention court martial, etc.) straining credibility, I think such a feat is physically impossible for an aircraft of that size. But then, I'm not a pilot - I just pretend to be one on X-Plane. I have relatives (also not pilots) who are convinced the story is true. Those of you who fly IRL, what do you think?

Unfortunately my grandfather passed before I was born so short of breaking out the Ouija board there isn't really a convenient way to ask him!

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    $\begingroup$ If it fits –and I believe it does– of course it's doable... $\endgroup$ – xxavier Mar 12 '18 at 7:55
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    $\begingroup$ Crazy is relative. This was a different time. Tex Johnson barrel rolled a 707 just because he could. Not to say that it happened or that it didn't, but present day assesments of risk and sanity are likely to be clouded by a certain degree of contemporary squeamishness. WWI pilots had a life expectancy of a few weeks on average. By WWII this improved, but the kind of reckless disregard for risk, which today would get you properly disciplined, was then the kind of thing that was deliberately sought out and encouraged in pilots. Who else would take a job where just surviving was a diceroll? $\endgroup$ – J... Mar 12 '18 at 11:45
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    $\begingroup$ @J... Johnston's barrel roll was not very crazy at all. As he himself explained, he maintained 1g throughout the manoeuvre. $\endgroup$ – MichaelK Mar 12 '18 at 13:02
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    $\begingroup$ "Aside from the the idea of a trained military aviator so recklessly risking crew lives (not to mention court-marshall, etc.) straining credibility..." You should read this: en.wikipedia.org/wiki/1994_Fairchild_Air_Force_Base_B-52_crash $\endgroup$ – ceejayoz Mar 12 '18 at 13:46
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    $\begingroup$ Re trained military aviators, this also: en.wikipedia.org/wiki/Cavalese_cable_car_disaster_(1998) $\endgroup$ – jamesqf Mar 12 '18 at 18:36
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Neglecting any potential power lines, I believe the manoeuvre is possible. I had to play around a little bit to get my simulation to work, though, showing that in real life, any attempt to underfly the bridge for real on the first try will be... risky. If I had to fly this for whatever reason, I would train the ground track at safe-ish altitude a couple of times before attempting the actual fly-under.

I am using a point-mass, trajectory-only simulation, which is accurate enough to study feasiblity of this type of manoeuvre, but not to determine exact values for required bank angles due to roll-in/roll-out turn radius variation. My aircraft isn't specifically a B-24 but a generic model; however the speeds, bank angles and descent rates I assume shouldn't be a problem for any aircraft of a similar size. Note that I am not modelling the climbout over the sea, as it doesn't really matter what rates are achieved, anyway, once past the coastline. I have used the bridge model mentioned by Tom and placed a B-24 model on my trajectory in Google Earth for a rough scale estimate.

This is how it looks:

Bixby Bridge Manoeuvre Pic 1 Bixby Bridge Manoeuvre Pic 2

My approach is towards the sea, as that will allow a safer recovery e.g. on engine failure than when diving towards the hills. [Later edit: Rates of climb in a B-24 trials report indicate on first looks that the necessary climb rates to clear the ridges when flying landward exceed the B-24's capabilities.] The manoeuvre is commenced at 150 mph indicated airspeed, in accordance with published best climb speed from the B-24 Flight Manual. I dive towards the ridge that has a path or road running along its top with 1000 ft/min descent rate, clearing it by approx. 120 ft. Then I roll into a 30-ish deg angle-of-bank right turn and push over into a steep 3000 ft/min dive. I clear the ridge in front of the bridge by approx. 100 ft (knowing that my right wing is lower, but still clear) and roll out pointing toward the bridge. My model gains approx. 14 mph during the 10-second steep segment of the dive as I can't generate enough drag, but if the B-24 behaves differently speed-wise it doesn't matter much, as the turn is nearly completed once speed has built up and the straight segment's geometry doesn't change measurably with speed. I clear the ridge underneath the bridge by some 50 ft and recover over the sea.

And... breathe.

PS: Anyone around who is tech savvy enough and would like to create the bridge for FSX?

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    $\begingroup$ This answer so far most thoroughly takes into account both the challenge of the terrain AND the performance characteristics of the aircraft. Thank you and well done...I may very well stand corrected! $\endgroup$ – masterofnone Mar 14 '18 at 5:22
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    $\begingroup$ well here's an attempt to follow that path... youtu.be/fY1I-20R734 ... though I think I would be tempted to come in from the ocean side with loads of beans and ride those ridges out... youtu.be/rN-vGZpGtF0 $\endgroup$ – Tom H Mar 15 '18 at 1:41
  • $\begingroup$ @TomH Well done! My reason to go towards the sea is that at any point you can safely break off the approach and climb away if anything happens. Coming in from the sea, after a certain point you’re committed under the bridge, even if all four engines quit (unlikely I know, but would you really want to bet your life on it with such a cool but, let’s face it, ultimately useless, manoeuvre)? $\endgroup$ – Cpt Reynolds Mar 15 '18 at 7:38
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A Liberator has wingspan of 34m, while the central span of the bridge is 110m wide, and 280ft high, so the aircraft will fit under the bridge.

Bixby creek approaches the bridge from the north-east, with a straight-ish approach of about 0.3miles. Approaching low from the north-east, and dropping down into the creek at the earliest opportunity might allow even a Liberator enough time to descend below the level of the bridge deck and recover over open sea, although the waves might be a little too close for comfort.

I wouldnt want to attempt it in a fully-laden B-24, but with a light fuel load and crew I'd say it's doable. Whether anyone ever did it is another story...

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    $\begingroup$ I hope those power lines weren't there if/when this was tried, though! $\endgroup$ – reirab Mar 12 '18 at 16:19
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    $\begingroup$ How high is the terrain 0.3m out? In other words, what descent gradient would be required to drop into the gorge on a straight approach and dip below the bridge? I‘ll try and have a go at modelling a trajectory one of these days - sounds like good fun! For info, a sensible manoeuvring speed for the B-24 seems to be around 150mph (from wwiiaircraftperformance.org/B-24/B-24_Flight_Manual.pdf). $\endgroup$ – Cpt Reynolds Mar 12 '18 at 16:47
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    $\begingroup$ Another aerial feat I would have expected to be impossible at Bixby: youtube.com/watch?v=QNfgu-bYEvc $\endgroup$ – Will Mar 12 '18 at 21:41
  • $\begingroup$ I scanned that doc but couldn't find a performance chart or the climb tables. Maybe I should find my glasses first $\endgroup$ – Tom H Mar 13 '18 at 0:12
  • $\begingroup$ @TomH I substituted best climb speed for manoeuvring speed as an approximation. The former is in the text for how to take off. Sadly, I didn’t find climb tables either. $\endgroup$ – Cpt Reynolds Mar 13 '18 at 7:22
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Interesting... It looks possible under ideal conditions in a modern aircraft. (I attempted a basic simulated flight in google-earth flight simulator-vid below)

Edit: The service cables mentioned in the other answer would also represent a substantial problem, but they were missing from the model.

Assuming you can get through the gap, the main issue for the maneuver seems to be the ridge immediately behind the bridge in the valley, which is marked in red in this shot, (and then you've got a second ridge behind if you continue a straight climb out)

enter image description here

Obviously it puts a constraint on the climb out path if you approached from the sea, or the path of the descent if you started in-land.

It looks like you would have to follow a fairly specific path to avoid the ridge, though if you knew the terrain and the aircraft well, it would make it a lot easier.

enter image description here

If you started inland, a direct approach would include avoiding these ridges on the way down, and a fairly hairy check of the descent as you cross under the bridge... There would presumably be some ground effect benefit when attempting to obtain positive rate of climb over the beach/ocean.

Edit: adding the utility cables makes it look like a very small gap indeed!

enter image description here

I noticed that Google Earth has a flight simulator, so after a couple of crashes into mountains, I fumbled a path... (I hadn't worked out the flaps, or power keys at that point, so its totally with defaults as set when selecting flight sim mode)

Edit: following @Cpt Reynolds suggestion in his answer above, this is one route through;

Or alternatively, come in with as much speed as you can stomach, and just ride over the ridges;

It was done using the SR22 model (310 horses, cruise 185kts);

enter image description here

If you want to have a bit of fun trying the various approaches... I used this model of the bridge from sketchup, and imported into the google earth desktop app.

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    $\begingroup$ Wow...thank you for the effort that must have gone into this! Truly enlightening! It does raise a couple of questions in my mind: I'm guessing for this demo you used the F-16 model...? Do you think a B-24 could actually climb and make that steep turn fast enough to clear that first ridge? I'm also assuming a B-24 would have to pass somewhat lower under the bridge to clear the arch. $\endgroup$ – masterofnone Mar 12 '18 at 21:05
  • $\begingroup$ Nice answer! it would be nice if you added some extra details to make it more relevant to the question though. $\endgroup$ – dalearn Mar 12 '18 at 21:15
  • $\begingroup$ @JacobPerl It was flown using the SR22 $\endgroup$ – Tom H Mar 12 '18 at 21:21
  • $\begingroup$ @TomH I'm not sure it CAN be done properly in Google if there is no model resembling the perf. characteristics of the B-24 but nevertheless very interesting what you did here! $\endgroup$ – masterofnone Mar 12 '18 at 21:45
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    $\begingroup$ I guess the value with the sim is seeing if there is a path that could be flown under ideal conditions. Whether it could be done in a B-24 is something best left to experts $\endgroup$ – Tom H Mar 12 '18 at 22:58
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As for why a military pilot would do something like that, consider the context in which it was happening.

This would have been during WW2 training, when losses, especially to bomber crews, were very high.

Put a bunch of teenagers in flight training, where quite a few get killed, and when that's over, they're on a path to getting blown out of the sky over Germany, or forced down over Japanese territory where they may have their head cut off with a sword on the spot, and those teenagers might get a bit reckless in blowing off steam. We may die anyway, let's live life to the utmost until then. Think you can fly this big pig under that bridge? Let's find out...

The highest scoring US ace in WW2, Richard Bong, once flew a loop around the center span of the Golden Gate Bridge, and then buzzed downtown SF, getting below the tops of the buildings and waving at the people in the buildings that were at eye level. Granted, this was in a P38 and not a B24...

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  • $\begingroup$ I'll admit my grandfather was known as a bit of a barnstormer in his time...did some crazy s*** at airshows and such! $\endgroup$ – masterofnone Mar 14 '18 at 5:35
  • $\begingroup$ this is actually a terrific answer, good one $\endgroup$ – Fattie Mar 15 '18 at 23:21
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As reirab mentioned there are currently utility lines that run half way up the arch. Looking at a modern picture you can see it's a communications line on the east side of the bridge with poles clearly visible on the north and south ends of the bridge.

Modem telephone poles

Looking at pictures of when the bridge first opened in 1932 there were not any utility poles then. Pic1 Pic2

However, by 1937 there were old style telegraph/telephone poles visible in photos.

enter image description here

Original Picture and Alternate View

Unfortunately the old lines are too thin to see so it's impossible to tell from the photos exactly how much of the arch they block. I suspect the line was in roughly the same position as it is today based on the fact the utility pole spacing and how much the lines sag hasn't changed much over the last 100 years.

If you're lucky the building department that handles the Bixby creek area may have old building permits and diagrams for these lines which could potentially disprove the possibility of flying under this bridge. You could also post a question over on engineering.stackexchange.com to see if anyone can give a height range as to where lines would have been relative to the current ones.

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Possible? Yes.

Smart? No.

Legal? Probably not now, may have been then (paraphrased as "need to maintain 500 foot clearance from things unless landing").

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  • $\begingroup$ This. Kinda like the B-25 that buzzed Florida Field during the Kentucky game forever ago on her retirement flight. See my answer to this question - aviation.stackexchange.com/questions/40945/… $\endgroup$ – ivanivan Mar 12 '18 at 19:31
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    $\begingroup$ Unless things have changed, it's 500 ft from buildings or open-air assemblies of people, for civil aircraft. (That's from memory, so I may be wrong.) IDK if military rules are the same, but it's quite common to have military planes come a lot closer to you than that, out here in northern Nevada/eastern California. I've been buzzed by jets while sitting on mountain peaks, and had a couple of C-130s fly over me at treetop level while out riding. (Thought my horse was going to panic, but she just kinda shrugged, like "What the heck were those?") $\endgroup$ – jamesqf Mar 12 '18 at 21:46
  • $\begingroup$ Pilot's of the 174th ANG liked buzzing campus even though they supposedly did get 'punished' for it. They would fly from east to west over the quad which put them below height on some of the dorms on the east side of Campus. I remember two different occasions in 1991. One F16 flew low and slow and the other for about 10 seconds had the afterburner on but was higher up than 500'. It is my understanding that when in a civilian flight zone that they are supposed to follow civilian flight rules $\endgroup$ – Rowan Hawkins Mar 18 '18 at 8:39

protected by Farhan Mar 15 '18 at 17:30

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