The Latécoère 631 Flying Boat Airliner. First flown in 1942, five of the eleven built crashed and one was lost in WW2 as it was destroyed by two Royal Air Force de Havilland Mosquito aircraft on 17 April 1944.

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Kondor999@reddit

Beautiful aircraft. It’s in the full aviator edition of Microsoft flight simulator 2024.

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Regarding the safety record: Examination revealed that the engines with a .4375 gear reduction and operating at 1,925 rpm during cruise flight turned the propeller at 840 rpm. This resonated with a critical frequency of the wings, ailerons and Flettner tabs, which was 840 cycles per minute. The interaction rapidly fatigued parts in the outer aileron control system and caused them to fail. The damaged aileron system allowed the aileron to flutter, breaking the control system completely and leading to a complete loss of aircraft control.

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pvcf64@reddit

sounds (kinda) like what happened with the L-188

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FreakyManBaby@reddit

what happened there

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pvcf64@reddit

It was a major issue and found to be caused by an engine-mount problem. The mounting of the gearbox cracked, and the reduced rigidity enabled a phenomenon called "whirl mode flutter" (analogous to the precession of a child's top as it slows down that affected the outboard engine nacelles. When the oscillation was transmitted to the wings and the flutter frequency decreased to a point where it was resonant with the outer wing panels (at the same frequency, or harmonically related ones), violent up-and-down oscillation increased until the wings would tear off. It caused two crashes look up "lockheed electra whirl mode"

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WikiSummarizerBot@reddit

Mechanical resonance

Mechanical resonance is the tendency of a mechanical system to respond at greater amplitude when the frequency of its oscillations matches the system's natural frequency of vibration (its resonance frequency or resonant frequency) closer than it does other frequencies. It may cause violent swaying motions and potentially catastrophic failure in improperly constructed structures including bridges, buildings and airplanes. This is a phenomenon known as resonance disaster. Avoiding resonance disasters is a major concern in every building, tower and bridge construction project.

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SemiDesperado@reddit

Well....thats not good. Lol.

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BlacksmithNZ@reddit

Really not good:

"Latécoère 631 (F-WANU) crashed into the Atlantic Ocean ... with the loss of all twelve people on board.

The aircraft was on a test flight from Biscarrosse to determine the cause of the crash of Air France Flight 072.

How bad is it to crash on a test flight killing 12 people when the flight is trying to determine why the previous one crashed.

I can just imagine an engineer onboard watching the ailerons depart from the wing and the aircraft pitching out of control and starting its doomed final dive, and thinking to themselves; 'ah, so that was the problem'.

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Significant-Rice-441@reddit

I mean if I was the engineer, that would be my exact response as well

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Zestyprotein@reddit

That's how every engineer dreams of going out, though.

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BlacksmithNZ@reddit

As a some-times engineer, personally would actually prefer to figure this out in the office looking at the data and die in my sleep, rather than being strapped into a seat in an out-of-control aircraft.

All the screaming would probably make it hard to write up a report

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Zestyprotein@reddit

Spoken like a ~~true~~ ~~boring~~ engineer.

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SemiDesperado@reddit

I laughed way too hard at this...

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Zebidee@reddit

Not the only time that has happened. There are a bunch of modern planes with restrictions on operating at certain power settings for extended periods.

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wheelontour@reddit

Wow, never heard of that before. The number of things that can go wrong in aircraft engineering and construction must be near infinite.

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nanomuffins@reddit

Gotta love a weird flying boat, thank you

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hbs1951@reddit

Interesting they seemed to have been developing a commercial French airliner smack dab in the middle of a world war. I find the weird.

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Calm_Bodybuilder_843@reddit

Why did the mossies get involved?

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Rc72@reddit

The seaplane's prototype was seized by the Germans during the Occupation of France, and inducted into the Luftwaffe. It probably was brought to Dornier for evaluation, because it was on the Constance Lake near Friedrichshafen (where Dornier was located) when those Mossies showed up on a "free hunt" in 44...

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Calm_Bodybuilder_843@reddit

Thank you for the clear and comprehensive response, so refreshing. A ‘Free Hunt’ is presumably no defence I am assuming? Thank you RC72

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amiathrowaway2@reddit

No a "Free Hunt" was a name given to allied aircraft (mostly fighter's and fighter/bombers) coming back to base with munitions still aboard after the primary target for your mission was deemed "Destroyed". You as the flight leader can and would target anything on your way back to base. Be it troop concentrations on the ground, cars, trucks, tanks, trains, planes, etc, etc.

Anything that was being used by the axis powers was a target of opportunity.

The little railroad museum near me has an old 0-4-0 German steam locomotive that according to the story I was told it survived the war by being buried in a haystack after it was used and cooled down after the day's work was done. Otherwise... it would have been shot to hell and gone by the above mentioned "Free Hunters".

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Calm_Bodybuilder_843@reddit

Well, I didn’t know that, thank you. Are you in Germany now?

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wheelontour@reddit

A distant relative of mine was shot off the driver's bench of his horse cart and killed in Lower Bavaria by what must have been one of those "free hunters", near the end of WW2.

A while ago I saw colored WW2 gun cam footage of exactly such an incident on r/combatfootage. It is not impossible that that was my relative whose death was caught on camera.

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amiathrowaway2@reddit

Unfortunately no the now..... Stuck in Indiana fixing a leaky cylinder head on said steam engine.

But Octoberfest will come soon enough. And with family still over in Germany thankfully I'll be there for it.

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Spacious cockpit for long distance flights between islands

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MyDogGoldi@reddit (OP)

Source from The Old Machine Press with story and more images.

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