Thanks for showing the footage on flutter. As an aerospace engineer I have tried explaining it to people and they generally can't believe that wings and tail surfaces will do that. My professor in college taught Aeroelasticity and there's actually 2 things that can happen when you go too fast for any given wing. One is flutter the other is called wing divergence. Both start with the fact that the aerodynamic pressure distribution around a wing causes a wing to twist about the main spar. If you go fast enough that twist will simply twist the wing so far it just rips from the plane that's called wing divergence for the obvious reason the wing diverges from the airplane. Its why aircraft have a "never exceed speed" on the airspeed indicator. If you go faster than that speed you risk having the wings suddenly rip away with zero warning. If you have ever heard of planes breaking up in a dive or as they fall from the sky that's what usually happens. Flutter happens when you go fast enough that the wing twists to the point where part of the wing stalls. The vortices created unload the wing which can then untwist. That then allows the air flow to re-attach and then re-twist the wing again until it begins to stall again. When that cycle happens fast enough its called flutter. That's what is happening in those film clips Juan showed. The worst is when that is close to the wing structure's natural frequency and the wing literally flaps. Like this kzfaq.info/get/bejne/obd5ZqSI1bq7mIE.html Its incredibly dangerous because not only will it want to rip the wing to pieces but you can lose control effectiveness and it becomes an unrecoverable situation. Aeroelasticity (Flutter & Divergence) is one of the hardest subjects anyone can study or look into because it involves aerodynamics, structural dynamics and structural strength. Those are usually taught as 3 separate subjects and Aeroelasticity combines the 3.

I was going out to LAX a lot from Indiana back in the days when Golden West Airlines was using dark blue helicopters as commuters. In my case I went to the Disneyland Hotel. After an 18 year safely record two of them crashed pretty much back to back. They then went to twin Otters (and Fullerton, near Anaheim). And two of them crashed back to back. All four were fatality accidents. That is what did air commuting in around L.A. The time frame was in the late 70's.

Having spent years working on DHC2 Beavers used for agricultural and float operation, I was horrified to see the condition of the tab that fell apart in a previous event. No one should have let a tab get to that level of wear and tear. On minor note, the wind tunnel flutter model was of a C-5, not a C141, and the mustang that crashed at Reno (2011) was 'Galloping Ghost', which also lost a trim tab, leading to loss of control.

Thank you, Juan. As a fan of the Beaver, and Twin Otter it was truly interesting to learn about the DHC-3 Turbo Otter. I never realized this bird is so large, and the uniqueness of her tail. My heart goes out to the families of the 10 souls lost. My God rest their souls in peace.

Excellent explanation. Thank you ! This brings back memories. As a brand new lieutenant in the F-16 SPO, I worked flutter tests on the F-16, as TAC (at the time) turned it into a ground pounder.

Mine and wife best friend was on that plane . She was also my best friend and boss and owner the company. Thank you

The Tacoma Narrows Bridge obviously needed a bridge rectifier.

It appears that one can bearly reach the rear elevator.

Really nice flutter videos. As a flutter engineer for many years, I found few people understood it. All they concentrated on was the idea of the aircraft shaking itself apart. Assurances that an aircraft could not be certified unless it was designed to eliminate flutter did not seem to reassure then. As you say, once the strength has been compromised, it is a new ball game.

pre flight inspection of tail section - Is that you Juan Brown -Bear? 4:24🐻

Great explanation especially since I fly on Otter float planes to fishing locations in Alaska.

Educating as always! Funny how you ignore the bear 🐻and continue describing the elevator. A true aviation geek.🙂

Thank you for the information about flutter. Interesting fact about the C-141 stabilizers. Loved those as a young fella growing up in Christchurch.

I usually always learn something from this channel whether I want to or not.

Thanks for your time and effort

Great video - clear, concise, with excellent examples👌. Thank God they issued the AD!

It's a privilege to watch and listen to you explaining these issues Thank you so much My thoughts and prayers to the families of all those killed

Great as always, thanks Juan

The Reno event you referenced was the P-51 “Galloping Ghost,” piloted by Jimmy Leeward. It lost an elevator trim tab during a high-speed pass, executed a sharp climb generating Gs sufficient to incapacitate the pilot, and impacted the runway near the viewing stands. So sorry to hear about this latest incident!

Reminds me of watching that Kemit weeks video where they were searching out sources of wing flutter on static airframes.

Dan Gryder was spot on with his analysis of this accident.

Very good & diligent. Thank you again.

Thank you Juan. Good luck! 👍

@2:56 they came out in the 1950's Juan . When viking took over I was working in the Downsview facility where the original tooling for the type was kept . Before viking changed the inspection criteria of the h stab , elevators and tabs, we made the repair parts under AC 43 13 or CARs 571.06 ...never had one fail with 16 aircraft and 5 different operators . I wanna see what they bring up from the bottom ,

Very informative video. Thanks Juan.

I liked your explanation on the Tacoma Narrows bridge oscillation

Oh my, chapter two.

Excellent presentation.

Flew on one of these back in 2007 from Malta to Gozo and back, operated by Harbour Air. No longer operate them from Malta

It will be interesting to see how this plays out. A local Seattle TV station had a new story on their website that mentioned the AWD a few days ago.

Excellent brief. Thank you.

Original video had a suspect crack showing which Juan thought was a scuff. It was removed.

F117 loss near Baltimore on 16 Sept. '97 was elevon flutter, there is video of the aircraft shedding pieces and the pilot abandoning the aircraft.

I love Ron's incredible ability to focus on the task/discussion at hand. No mention at all was made of the large brown bear standing on its hind legs in the shallows adjacent to the tail end of the moored Otter..Meanwhile, my mind has conjured up about a thousand memes...

Salt water environments are particularly harsh on aluminum aviation structures and require much greater inspection frequency. Particularly on older aircraft.

Thanks for explaining this.

ty, jb...looks like there's a problem there, unfortunately

correct me if I'm wrong, but the crashed otter (seattle seaplanes) as well as kenmore airs fleet of otters and beavers are pulled out of the water each night and put on the hard. Seems like there is plenty of opportunity to inspect the tails from ladders or whatever.

Apparently N725TH had a 100 hourly only 4 hours previous to this accident. 🤔. The FAA definitely don’t follow the same AD’s as the Canadian ones. Hence the re-look at the 2018 AD. With over 10,000 hours in the single Otter and the fact that I was flying one the same day in the same area, I’m not 100% that it’s structural failure. We actually delayed our flights that day. But that just me.

I think the Reno event was the p-51 Miss Ashley II that crashed back in 1999. It crashed after rudder flutter causing the empennage and rudder to separate from the aircraft.

This must be the revised video. Good to re-post with amendments/corrections.

Hi! If you have a minute, you should talk about the minor accident at Groveland airport on the 1st of October. Pilot uninjured, but plane hit a deer after landing and flipped nose over, destroying the prop and part of the engine. I had a family member there watching the whole thing happen. Luckily no fire, and they got him out rather quickly. I want to bring awareness to this, because this airport is a beloved airport by the locals for both the gorgeous views and our amazing yearly airshows with Wayne Hanley, and we are currently dealing with the county trying to pull funding, because of this accident that was simply out of anyone control. Our airport is the reason that the rim fire didn't destroy groveland 9 years ago, because us residents keep it maintained. We care a great deal about our tiny town, but it is very special to most of the residents of the airport. We have put a lot of work into maintaining the small community of groveland and them removing funding would essentially kick out 70% of the residents up there who are retired. Hopefully you see this!

Very informative.

Dan Gryder turned out to be spot-on here! 👌👌

We probably have a dozen of these landing and taking off daily in my community.

JUAN,,HI,,THANKS FOR THE INFO, DAMN,THOSE PIX OF DAMAGE, SHOES FANTASTIC DAMAGEhis also reminds m of TWIN OTTERS OPERATING IN THE PACAFIC, ,Operators devoted to use stainless steel control cables, being involved 100% in salt water,,,,UNFORTUNANEY ,THOSE CABLES WERE , BECAME BRITTLE,,USUALLY CRASHING ON CLIMBOUT, so AFTERALL THE NORMAL CABLES WERE THE ONES WHOM LASTED MOST OF ALL,,,TWIN OTTERS LAND VARIENT,,I HAVE FLOWN ON MINY TIMES, BUT MORE BN2 BRETON -NORMAN AIRCRAFT 🇺🇸🇺🇸🇺🇸🇺🇸

Hope the guys flying these down in the Keys are getting this. I'll be on one this summer. 👍

the attorneys are lining up

Reminds me of the Jimmy Stewart movie where he was an engineer working on stress fractures of commercial aircraft.

That you for the report I get it

AOPA Magazine October issue has a good article on the Otter

I remember being on Twitter watching the Learjet that crashed into the ocean over in Europe and then a few moments later FR24 comes up with this as breaking news. The day before it was the hijacked king air incident too. Terrible week for aviation for sure

Funny, Rapids Camp Lodge in King Salmon Alaska.....quite a history there.......

Whoever signed off on the last inspection had better have a GOOD lawyer

Transport Canada advised about this problem back in 2018.

Should have used the brown bear as an elevation example 😮 That’s OK, we still love you…. Interesting. Maybe a “real” physics geek can answer this, but as a long time pilot, what you do to one side, you should compensate with the other…. Using the weights on the left side? That second rod would seem to be just as cheap in the mfg process…

#229👍😤Thanks Juan! ERAU 80 CFIA&I ret.

Unfortunately the NTSB Didn’t catch this problem from the previous accidents even though there were warning signs that were ignored. This is the same problem that caused the issue at the Oraville dam, The concrete bridge that fell on those people in Florida and the collapse of other bridges and buildings such as that one in Florida. In almost every instance There are warning signs that have been ignored. It’s only after a catastrophic failure that people start to pay attention. There is a very good book titled “To engineer is human “ by Henry Petroski that Chronicles how engineering failures typically take place.

That brown bear standing by Five Romeo Charlie must be seven feet tall....

Sometimes we take for granted the fact that we can fly!

4:19 AMT has nice bear fur coat!

From the seaplanes ive worked on just about every one of them has damage thats often impossible to see. Corrosion is insidious in the way it can get into every part of an airframe or powerplant.

In the original vids comment section, someone posted about a wind tunnel test of a unspecified aircraft they were involved in. At a very specific air speed if the tail experienced fluttering ( gusty wind simulated by pulling a rope attached to the tail ) the tail would break off. Instantly. I'm hoping that comments from the other vid can be merged or the original poster can repost.

This is what happens when the systemic paralysis of the aviation industry and the FAA result in half century old airframes in commercial service. It's crazy. In the meantime, it would not be difficult to design a 3D printed replacement for that part with an integral skin and spar monoqocue design, made from almost any alloy. But the FAA would take a decade to approve it. Same with structural adhesives. Rivets? In 2022? Nuts.

I've done enough preflights to know the importance of getting hands on to inspect everything thoroughly. The question I have is how many preflights are shortened on not as thorough maybe as a practical matter due to an aircraft being on floats. Especially dedicated float planes..... It seems like doing a thorough preflight inspection would involve spinning the aircraft around at the dock in order to get under both wings and the entire tail.... I used to have coffee before work and a lot of lunches near a seaplane operation. And after watching them come and go maybe several hundred times at all different hours from very early in the morning to late at night. Both when they were beginning and ending operations for the day, I've never seen any of those aircraft turned around or inspected from both sides.

Probably doesn't help that's a corrosive environment

There was an AD on this same stabilizer linkage on an otter or beaver back in the 70s. My friends were killed in a De Haveland with similar pitch up and nose dive In DRT. It was a CAP mission and the crash happened at the end of 13 at DRT. It was said it was an un addressed AD in the stabilizer linkage...I'm wondering if it is related.

I don’t think that your F-18 clip is flutter. I think it is the vortex from the forebody chine simply buffeting the vertical stabilizers. That is a very different mechanism than flutter.

Kinda reminds us of the Chalk Air Wing failure. Too many repairs to a critical surface.

I wonder if the DHC6 suffers from the same issue. They're very popular for skydiving operations. The high tale design lessens the chance of a jumper striking the tail upon exit

Rest in peace Jason Winters and all others on board.

Aerodynamic (inflight) flutter? Watch what happens to the tail assembly on a float equipped single otter on take off, PT6, WALTER, GARRETT or PEZETEL😳😳. It’s certainly not confidence inspiring😢

Did I hear correctly that this doesn't include the radial engine Otters? Seems odd.

sad to here another one crashed. #456 N703TH sure pops up allot on google images

I wasn't sure how to message you any other way. Can you please do a review of the crash in Brentwood,Tn. yesterday. Thanks Juan love your reviews.

It looks to me like hiring a bear to do the tail inspections is a viable option.

Is that the pilot standing by the tail lol😊

Do these servo tabs actually move the elevator, or assist in moving it? On a/c that I flew, only the servo tab was connected to the yoke. The only thing moving the elevator was the tab- so if no airflow, (parked or taxi-ing) there was no way for the pilot to move the elevator.

Didn’t the locky Electra L - 188 have flutter problems also when it was first introduced?

Hey Boo Boo! Grab a step ladder Help me with the preflight before the ranger Smith get's here...

First! Great video as usual.

Cancel the Emergency Airworthiness Directive! Just found the problem, Juan ... bears have been doing the inspections.

Why wasn't the operator complying with the Canadian AWD? I think the operator is 100% liable for these deaths. Almost murder or at least man slaughter. The lawyers should have fun with this one while getting richer.

So Transport Canada issued an AD (AD-CF-2018-4) in 2018 and the FAA did not follow up???? That alone is a failure in the FAA system. I see several flights a day going past my home and I wonder about how secure the elevators are every time.

Are the elevators removable. Should not be hard to have viking create whole new elevator assemblies. If not a company with Vikings approval and FAA approval to create new elevator. Why a whole new elevator. An option to prevent loss of a multi million dollar aircraft.

Some of those repairs looks way sketchy. How is that even possible on an airplane?

Galloping Ghost

How many DHC 3 and equivalant are flying and have not checked ?

Dan Gryder had this figured out way too fast. NTSB and FAA…come on.

❤👍👍👍🙏🛩

This is all really important but, whats up with that bear. 4:13

Sorry to say this Juan but, the photo at 4:13, the bear standing looking at the aircraft, completely ruins the seriousness of the video. It is one of the funniest photo's I've seen, of a (presumably young) Brown Bear. You could run a wonderful caption contest on it.

04:15 Your pilot: Yogi Berra!

So basically, the preflight gets shorted because it’s “difficult”. When you’re out on the highway, make note of all those truck tire treads lying around on the side of the road. THOSE mostly happen to result from people not bothering to actually check their tires every time they stop (defined by law), or at least daily before heading out. I guess otters should have one of those spiffy Little Giant ladders tucked in someplace? Sorry to sound flippant, but the fact that so many instances of cracking showed up on aircraft that are ostensibly inspected at least daily in commercial operations might just make a person wonder WTF these operators have been doing this entire time, and in extension, are those techs performing annuals on these planes not really doing them correctly? Fair questions, I think.🤷🏻‍♂️

What does blanco lirio mean? I’ve tried looking it up and got nowhere.

SO SAD....... COULD have PREVENTED the ACCIDENT ~~~~~~~~ UNDER INSPECTION / SAVING ALMIGHTY DOLLARS !!!!!!

Almost like, I dunno, aircraft that are over half a century old should be mandated to be scrapped and replaced with newer, safer models .

All aircraft operated in a salt water environment ,are an accident waiting to happen ! Unless the air craft is totally made of plastic or aircraft technicians are very creative on their Inspections ! ( True Safety is no Accident ) come on aviation let’s Adopt this philosophy! Stop taking Innocent lives ! If your in aviation for the money or the glory get out ! Ya gotta to be in Aviation because you love it ! Aviation is for some one that thinks Of their precious life first and will consider all the variables before they Put their life on the line ! Even passengers are the pilot in command of their own lives ! If there’s a question on safety don’t rely on luck ! You make your on luck !If there’s a question on safety find another way even if you have to walk ! But then there is always the people that don’t think their lives are So special and don’t care ! And very unfortunately they can be at the helm of an aircraft with hundreds of Innocent People on board ! My question to all is what can we do to save thousands of Innocent lives ? Sincerely Captain Mark H Wirth

Accidents aside who's that welcoming bush campers?

4:20 _"What's the bear doing?"_