Helicopter goes down in the Hudson River (NYC)

[Nugget]

Thank you for sharing your expertise with us, FCD!   Other than being a terrible tragedy I had no concept of how this event might have even been possible, but now have a clearer picture of what may have occured.

[FCD]

I've now seen a report that the pilot reported he needed to refuel 15 minutes after departure and was allegedly returning.

Not sure if that's reliable reporting and I don't know how it has anything to do with it breaking up in air, but I've seen it.

Yeah, I think the media is making much ado about nothing over this.  The pilot was likely radioing his base to let them know that he'd be require refueling after his current flight.  The company probably can't stage fuel tanks at the landing location, so it probably requires a fuel truck to come to them from a local FBO.  So, he was likely just notifying them so they could get the truck on the way so he wasn't waiting for them on the ground while the truck drove across town.  Needing fuel likely had nothing to do with the breakup.  Just the media once again showing their naivety and willingness to jump at any straw.

[Ksihkehe]

Thank you for sharing your expertise with us, FCD!   Other than being a terrible tragedy I had no concept of how this event might have even been possible, but now have a clearer picture of what may have occur

Agreed.

[FCD]

After looking at the longer full video, it only further confirms my earlier suspicions.  Prior to the breakup the helicopter is in straight and level flight.  There is zero indication of any anomaly; the helicopter does not appear to be making any sort of emergency descent or other special out of the ordinary maneuver.  Then, the aircraft suddenly (and wildly) appears to spin 180 degrees on the rotor axis.  This motion is sudden and violent.  Something went bad-wrong right at that moment.  Not even a complete loss of the tail rotor system would cause such a violent rotation, (but an impact of the main rotor to the tail boom might).  Immediately after this sudden rotation, the helicopter begins shedding parts into the air.  This tells me whatever happened was violent enough to rip everything but the most structurally sound elements of the frame off of the helicopter and send it flying.  For the helicopter to rotate that quickly suggests to me this is the point where the tail boom was severed.  The helo does manage to come back around into the correct orientation for flight, but by this point you can clearly see it has started its downward trajectory.  This also explains the inverted orientation down near the ground; as the helicopter fell forward rotation was experienced, likely due to simple weight imbalance forward.  The remaining crew cabin was tumbling, and by the time it had reached the water it had made a full half rotation to the inverted position.

Definitely a tragic event to be sure.  If there's any 'good' news here, it would be this...  This event was sudden and violent.  Occupants inside likely would not have had time to even begin to understand what was happening before the helicopter impacted the water.  The pilot likely realized there was a serious mechanical problem, but the PAX probably never had time to feel anything other than a major sideways jolt and then several seconds of high-g rotation before impact.

[FCD]

Just some further updates:

The Bell 206L-4 LongRanger helicopter model involved in the accident had two recent active AD's (Airworthiness Directives) from the FAA.  One of these called for inspection and possible replacement of the main rotor blades due to possible "delamination" issues with the carbon fiber blades (just exactly as I had opined about in my OP).  Rotor blades for the Bell 206L-4 are $83,000 per each, and there are two of them.  Plus, rotor blade replacement usually requires an overhaul of the bearings, swash plate, and stabilizer bar assembly as well as having to have everything disassembled, reassembled and then all re-balanced.  This is probably another $40-50,000 in repair labor.  One thing about helicopters is they are very expensive to maintain to an airworthy state.  A potential $200,000 repair bill is something a tour operator might balk and delay on.  Even inspections for this kind of thing are fairly comprehensive, often involving removing the blades and sending them out for X-ray analysis.  This typically isn't something which can be observed by a visual inspection.

The federal agency issued the first directive in December 2022 and called for the inspection and possible replacement of the models’ main rotor blades due to “delamination” — an issue with the internal layers of the blade separating due to material fatigue, damage or other defects.  Source

The other AD had to do with the tail rotor assembly, specifically a joint in the drive assembly.  This as a result of a failure in another similar helicopter.  I doubt though this would lead to as catastrophic of a failure as what the helo in question experienced.  Make not mistake though, losing a tail rotor on a helicopter is a BIG deal because it affects the ability of the helicopter to successfully auto-rotate in an emergency and would likely result in a crash...although probably not as dynamic of a crash as this one.  Tail rotor failures as a result of striking other objects, including the ground, have been the cause of many helicopter incidents.  This is why on some of the newer helicopters you see the tail rotor housed inside of a shroud which surrounds the whole blade.  The 206 does not have such a shroud, but again, I doubt this was a tail rotor issue anyway.

edit - Just FYI, an FAA Airworthiness Directive (AD) is not directed at a specific aircraft, they are intended to apply to all aircraft of that model and type.  So, it's not an individual helicopter thing, but rather a directive which applies to all helicopters of that type.  Plus, in order to maintain an overall airworthiness certificate for the aircraft, an owner must be able to demonstrate compliance with all AD's for that model regardless of date.  Though, this is rarely checked unless an aircraft is transferring ownership (i.e. being sold to another party).

(Anecdotal note - This is one of the reasons that buying an older aircraft can be so expensive.  Over the years AD's can stack up, and by the time a new buyer comes along they could wind up with a mountain of AD's to deal with.)

[FCD]

Also of interest in this story...

The specific helicopter in question had maintenance performed on its main transmission back in September 2024.  What the nature of this maintenance was is unclear.  However, a complete transmission failure in a helicopter could very well result in a catastrophic in-flight failure such as this one.  The transmission is the only thing holding the main rotor shaft onto the helicopter.  If the transmission were to 'frag' itself, it could conceivably lose control of the main rotor shaft, releasing the shaft and rotor assembly altogether.  That would make for a really bad day.

Nothing conclusive here though.  Any work on a transmission would have needed to be done by a licensed Airframe and Power Plant (A&P) aviation mechanic / facility, and would have needed to be done in accordance with all manufacturer required certifications (which is a LOT).  Plus, the helicopter flew successfully, presumably daily, for 7 months following this repair.  Most repair related failures will take place within a few hours of operation after the repair, so the fact this helo flew for over 7 months following the repair really suggests the repair likely had nothing to do with the crash.  Just another possible thing to look into.

[FCD]

AND...on the subject of "people are sick anymore"...reading thought the comments section of the NY Post is pretty disgusting.  Comment after comment expressing glee over the crash.  It seems many New Yorker's don't like these sight seeing helicopters.  "Don't like" is probably putting it too mildly..."despise" might be a better term.  So, they're busy posting away about how happy they are that this helicopter crashed and hoping that more crash, and all the companies get sued and all go out of business.

People are fucking sick in our society today, just fucking sick!  Fifty years ago you'd have never seen a comment like this, and anyone who made a comment like that would get their ass kicked.  There's a lot of people in this country who need a good ass whoopin!!

[Ksihkehe]

Even inspections for this kind of thing are fairly comprehensive, often involving removing the blades and sending them out for X-ray analysis.  This typically isn't something which can be observed by a visual inspection.

When you mentioned delamination I wondered what they did to prevent them and I figured imaging of some kind.

Do these take a while to process for imaging and clearing them? I would imagine down time would be, right or wrong, a consideration for scheduling repairs. I don't know, but I would imagine the pilot would be doing his own risk assessment and if they strongly felt the craft was unsafe then they probably wouldn't take it on sight-seeing tours. Do pilots typically keep up with all this range of maintenance in preventative work and alerts? Would he have known if the owner was putting off a repair that was critical?

[FCD]

When you mentioned delamination I wondered what they did to prevent them and I figured imaging of some kind.

Do these take a while to process for imaging and clearing them? I would imagine down time would be, right or wrong, a consideration for scheduling repairs. I don't know, but I would imagine the pilot would be doing his own risk assessment and if they strongly felt the craft was unsafe then they probably wouldn't take it on sight-seeing tours. Do pilots typically keep up with all this range of maintenance in preventative work and alerts? Would he have known if the owner was putting off a repair that was critical?

Well, those are some interesting questions.  Typically, an 'owner' or an 'operator' would be notified, not necessarily a pilot (because there could be many).  Then, depending on how the AD is written, the AD will lay out what restrictions apply.  There are three types of AD, only one of which requires immediate action, the 'Emergency AD'.  An Emergency AD will specify what actions need to be taken and what restrictions apply until those actions are taken.  So, for example, an AD might require the owner operator to perform whatever prescriptive inspections listed to be performed before the aircraft flies again, or it might require some action per increment of time (i.e. inspect every 30 days, or, inspect withing 50 hours of operation, etc.).  So, not all AD's immediately ground an aircraft completely, but many do.  Failing to comply is complicated (kind of).  Technically, a failure to comply puts the owner/operator in violation of their certificate of operation, making it illegal for them to operate.  In and of itself, this wouldn't cause much to happen, UNLESS something like another infraction were to take place (could be unrelated to the AD).  This would cause whatever authority to first look into whether the owner/operator has a valid certificate of operation (kind of like a driver's license, but for a company).  If they were found to be in violation, any number of things could happen (i.e. fines, jail, aircraft seizure, etc.).  

But probably the biggest risk an owner/operator would face is the insurance implications.  If an owner/operator were found to be in violation of their operating certificate they would likely be dropped immediately by their insurance carrier.  And this is a BIG deal.  Aircraft insurance is difficult to get in the first place (very difficult), and it's also very expensive.  Getting dropped by a carrier would only make this even more difficult in the future (IF they could even get any insurance at all), not to mention more expensive (by a LOT, like double or even triple).  Insurance costs can put you out of business faster than any other single thing short of a crash.  Operating without insurance would be, well, insane (not to mention highly illegal).

But to your point, a 'pilot' wouldn't absolutely know.  However, most smart type rated pilots generally keep up with AD's issued for the aircraft type they fly on their own accord.  Plus, many pilots belong to pilots unions, and unions are always looking for reasons not to work and still get paid.  Regardless, pilots generally have a pretty good knowledge of what's going on with the aircraft they fly.  It's not that much different than a recall on a car/truck.  Even if you missed the letter in the mail, or the phone call, you'll likely find out about a recall either via word of mouth, the media or other sources.

And, to your last question...'would the pilot know if the required action was being delayed'?  As you pointed out, some of these inspections require downtime.  Depending on how many aircraft are in the fleet, pilots 'might' know, but also might not.  Take for example a major airline who have hundreds of aircraft in their fleet; a given pilot might never fly the same airplane twice in a given week, even though they fly daily.  In this example, the pilot would have little to no idea if an AD had been complied with, even if the AD required a couple of weeks downtime for the aircraft.  Conversely, if a company only had one aircraft and this aircraft flew daily, then any pilots of that aircraft would be keenly aware of whether an intensive AD inspection or corrective action had been performed.  It just depends on a number of factors.  You are correct though, downtime for a small company can be a very painful experience because it shuts down your revenue stream for any affected aircraft completely while they go through whatever inspection or repair is required. 

Lastly, removing and replacing the rotors on a helicopter like the Bell 206 can be done in less than a day.  Depending on the inspection required, and the location of the nearest facility capable of performing that inspection, will determine how long the actual inspection process takes.  In a place near a major city, an inspection of parts or a repair might only take a day.  In some remote part of Alaska, as an example, that same downtime might stretch into weeks or months.  Just imagine the logistics of having to ship/transport an object which is 15-20 feet long, so it's really a transit time issue and a parts availability issue more than anything else.  The actual inspections and repairs themselves don't take too long.

On a side note, this is one of the things which kills me about the government and military in particular.  Many of the US Military special forces commands use small helicopters extensively, and they're rough on these helicopters.  Main rotor blade damage due to blade strikes from things like rocks and debris is common.  They go through rotor blades like Skittles, and when you realize each one of these blades can easily cost $100k or more, it's just mind boggling.  Anyway, I've rambled on enough here, but I hope I answered your question.

[FCD]

Further update:

Now investigators are looking into the "Jesus nut" (as I theorized in the OP) as the possible cause of the rotor separation.  This could lead to the main rotor shearing off the tail boom after separation, as I suspected.

Source