Ugh....

https://www.liveleak.com/view?t=uD7UF_1540936986

Damn!

My son flies heliflopters and he tells me tail rotor failures scare the shit outta him, so he practices recovery techniques regularly.

Looks like that crew didn't have the altitude or the area to do an effective recovery.

You can recover from Loss of TR Effectiveness......but you can't recover from a TR Failure.  At that point it's a hopefully a controlled crash.  Some helicopters have to enter autorotation immediately, others if they have the airspeed, can reduce power and keep the yaw controllable since the TR is unloaded by the vertical stabilizer and airframe.  Then you can slide it onto a runway using the throttle to control the yaw......but IMHO, it's a lot safer to just do an autorotation.

Yep to the above. Tough break in the video.

With that in mind, did they really need to do a Max Performance takeoff to such an altitude? I don't know the area or the hazards present in it, so I'm not trying to armchair QB. I'd just be curious to know why the pilot didn't try to get some airspeed as soon as possible. That HV curve bites pretty hard when you're in the shade...

The HV diagram is for single engine helicopters and the ability to preform a no drama autorotation after engine failure.  This is a twin engine helicopter.  Twins that are unable to fly away on one engine will also have an HV diagram.  H/V has nothing to do with loss of tail rotor.

Except for when the proper response to such a failure is to enter an autorotation... I have no idea if that's the case for an AW169 according to the POH, to be entirely honest, but I do know it would eliminate most all M/R torque from the equation except, perhaps, for transmission drag. And while all my time is in single recips, I have a hard time believing that there's no H/V diagram, at all, in the POH of most twins. I'm open to learning otherwise. But an auto isn't a maneuver reserved solely for engine failures, and airspeed/altitude are just as much your friend in a twin as they are in a light single for a variety of reasons...

You do not understand the purpose of the HV diagram. https://blog.aopa.org/aopa/2014/12/17/the-mysteries-of-the-height-velocity-curve/

There are many reasons to auto.

The HV is a suggested flight envelope for a no drama auto for someone who has the pilot skills of a potato following loss of engine in a single engine helicopter.  It is not a suggested envelope for any kind of auto for a different purpose.  An auto ranging from "okay" to "well, we're alive" can be accomplished from anywhere inside the shaded area of an HV chart.

Once you become a working helicopter pilot the HV diagram goes out the window anyway and you learn what helicopters are actually capable of.  Reading the flight manuals of helicopters you have been flying for 10 years will become amusing.  Bordering on a drinking game.

I had a long diatribe typed out, but thought better of it. I understand the HV curve just fine, thanks. The physics and principles of flight are the same in the training world as they are in the so-called "real world" of flying helicopters. An auto is an auto, from an aerodynamic standpoint. True, no two are the same, but the elements needed to successfully perform one DO remain the same, regardless of why you entered one, be it power failure, T/R failure, in-flight fire, etc. That HV curve shows the areas where a pilot of average skill can auto successfully, period. You're not insinuating that a T/R failure at 100' and 0KIAS would somehow allow you to negate the laws of physics and fly an auto better/easier than you could if you entered an auto because of a power failure at 500' AGL/75KIAS are you??

And last I checked, the RFH states on page 11-16 that entering an auto is the correct EP for T/R (or antitorque system) failure in a conventional helicopter, regardless of how many engines a given airframe may have...

That's a bold and entirely unsupported claim.

Even in a B212, with ridiculous rotor energy, a 0kt/50AGL auto would be a very UGLY thing.  Heck, even losing one engine at high DA in a 50ft hover would generally result in significant damage.

Clearly not.

No.  If you'd take the time to simply look at an H/V chart and use your imagination for about 10 seconds, you'd see how dumb that is.

Not sure where you got that idea.

Yeah, nobody is disputing that.  Maybe take a step back and re-read my posts.

Not at all.  People who are a lot smarter and a lot more experienced than us have been asserting such for a while.  I had a bell test pilot sit in a room full of utility pilots and tell us the same thing.  It may not be pretty and the aircraft may not survive, but survivable crashes are successful autos.  And to be clear,  I am not saying that every attempt will have a positive outcome.  I am saying that surviving an engine failure from inside the knee is possible.

I've never flown the 212 so I have no idea.  How do you like flying it?  You a fire guy?

^From right there.^ You seem to suggest that the HV curve is only applicable in the event of an engine failure, and that your height/velocity is of little concern in the application of an auto for any other reason, which is patently false. If that IS how you feel, may we never cross paths in a way that requires I fly in an aircraft you're piloting!

The notion that you can throw out good data purchased at the cost of multiple airframes, and in some cases the blood of former aviators, while establishing the capabilities of an aircraft is asinine. Yes, any landing you can walk away from is a "good" landing, so the saying goes. But why would I want to ignore sound data that gives me a clear advantage? Shoot, plenty of folks have died horrible deaths or have been permanently disfigured from post-crash fires that occurred after an otherwise survivable crash. I most certainly do NOT want to die that way, so I aim to maintain a flight profile that gives me EVERY chance possible to get on the ground without balling up the airframe. It's not necessarily the crash I'm most worried about...

Anyway, we're clearly going to disagree here. I hope, for your sake, that your really ARE as good as you think you are with regard to your ability to make a successful, survivable auto from anywhere within the shaded area of the curve, and that you never have to find out either way. As for me? I plan to spend as little time in the shade as I can. I want to grow old with my wife and spoil my grandkids when the time comes...

Its not a suggestion, it is fact and common knowledge.  Consult your Chief pilot for remedial training.  What helicopter do you currently fly?

Oh look, another line guy that’s smarter/better than the test pilots.

Never seen that before.......

I'll get right on that, Mr. FAA... What am I, getting virtually ramp checked here??

+1 I've run into a few in my short time in the heli world. These guys worry me, because you often can't tell them apart from the rest of us who actually give a damn about how we fly and the image the rest of the world has of us until it's too late. There are definite areas where we have an uphill battle such as NY or other high traffic locations. Adding in careless or reckless ops doesn't help!

A ramp check?  No.  Are you always this dramatic?

I am suggesting you consult someone you may actually listen to on the matter as you have no interest in learning from others here.  Maybe he'll take the shovel away from you.

You're right, I have less than zero interest in learning from someone who's shown a complete disregard for sound doctrine and hasn't produced any credentials or other means to verify their experience and knowledge level. Good day, sir!

It wasn't a max. perf. takeoff, it was a CAT A departure profile, in this case specifically one where the helicopter backs up and out in a way that allows returning to the confined space in a forward direction if one engine is lost prior to the Critical Decision Point (CDP). I don't pretend to know much more about it than that, since I only fly the lowest forms of helicopter life , but here's a nice article on some of the things that go into CAT A departure profiles.

One can argue the merits of performing a CAT A profile like that vs. obtaining some forward speed in the event of an anti-torque failure of some kind. However, I suspect that a) anti-torque failures are far less likely than engine failures and b) it would still be a shit show at any forward speed they were likely to have achieved right about the time they were clearing the periphery of the stadium using any departure profile you care to name.

The amusing part is that you are referring to me when its actually you.

lol.  Career advice:  Learn when to shut up.  It has served me well, learned a lot in the process.

I tried.  I broke my own rule of "don't try to have a discussion with green CFIs" and have proven, again, why its a waste of time.  I hope you are willing to correct yourself.  You're doing a disservice to your students.  Good luck to you, you'll need it.

I've been in a R44 and done a zero a/s hover power loss from 50 ft.   Scary as hell, but the test pilot set it down like nothing.  Did it in a B206L4 too.

And I've seen someone do it in a B47 from at least 70, maybe 80 ft.

212 would have no problem at that altitude.  You could chop the throttle in a uh1 and set it down, pick it up, do a 360 right pedal turn and set it down.  Tons of inertia.  No telling what you could safely set it down at agl in that thing if you're timing is perfect.

This right here!
Yes, this appears to be a CAT A confined area takeoff procedure, which was appropriate for the situation.

@AZYoungGun
You cannot land into and takeoff from an area like that without accepting some sort of risk.
-CAT A allows you to fly away or land safely in the event of an engine failure, but a successful auto will be near impossible.
-Flying a more typical helicopter takeoff (where you gain airspeed and altitude) and lose an engine and you will crash into the stadium walls or lights, not to mention you can't auto in this scenario either due to obstacles.

It looks like he did a cat a takeoff?  Europeans like that stuff and often will default to it for any sort of pinnacle or confined area takeoff because its "safer".

I think the cat a thing is a poor choice most of the time for just this reason - it requires a huge increase in the amount of time you are at low airspeed, high altitude, and high power setting.  It's like a solution looking for a problem.

As for a HV curve, many multi-engine helicopters have one these days.  You have to read the manual to see what exactly it is telling you and when it applies.  Some will be the same as a single engine curve - when you can safely autorotate after a power loss(i.e. Both engines fail).  Some will tell you where you can "fly away" from a single engine failure by using maximum power from the remaining engine.

I've never heard it called CDP before.  I've always heard it referred to as TDP (take off decision point).  Its the same thing obviously.  Maybe its a european thing or perhaps a manufacturer thing?  Not important just curious if you know?

When flying a twin (or anything else) I prefer airspeed over altitude nearly all the time.

The part I bolded is well said.

That's an R44.  And while the 44 has relatively low rotor inertia it also has very little weight, and thus the energy required to arrest its momentum is smaller.  When you get to medium twins, weight goes way up, and the energy required to arrest their decent.  The 212's MGW is just shy of a weight endorsement.  At one of my jobs I fly a light twin and we do zero airspeed OEI's from 50 and 100ft hovers.  Even with one engine operating we enter an "auto rotation", aggressive nose over and when you get to the bottom it can still get interesting.  And that is with only me and the DO and an hours worth of fuel on board.  The user you're responding to is correct in asserting that from a 50ft hover at high DA the helicopter would probably be a mess.

As far as the huey thing goes, I'd pay to see that.  

There is a video on youtube of someone in an r22 doing zero airspeed autos from many heights ranging from like 50ft to 250ft, its pretty neat to watch.

And here is the crux of the entire situation.  Acceptance of risk.  As you stated, it is not possible to take off or land from such a place as a stadium without exposing yourself and your pax to some sort of risk.  Its not possible to fly a standard, steep or even shallow approach without entering the knee of an H/V chart.  You are always exposed to risk.  It is not possible to make any sort of a living as a helicopter pilot without being exposed to significant amounts of danger.

The crew in the video assessed their options and chose to expose themselves to the risk of landing and departing from the stadium.  Unfortunately for them it did not end well and they suffered the worst possible mechanical failure at the worst possible time.  The only chance they had was to chase the nose with the cyclic and dive aggressively to try to get air over the vertical stab.  It was over for them by the end of the first rotation sadly.

I've always wondered why the Europeans have such a hard on for CAT A.  I agree with you though and you're absolutely correct that you are exposing yourself for an extended period of time.  Way more than I am comfortable with unless absolutely necessary.  CAT A has its place, but its not that great of an option IMO.  I'd rather be at vTOSS as quickly as possible.

I think you are correct. As I mentioned I know just enough about it to appreciate the process, and not much more than that.

In the UH-1H, you could climb in the first half of a hovering auto, so yes, lots of rotor energy.
In the UH-1N, our HV shaded region starts at 10ft at 0Kts.  Obviously, a 10ft fall would not be pleasant, but it's easily survivable.  Once you get into OGE hovers, things start to get tricky.  Above about 600AGL, you can dive for airspeed then flare normally, which works nicely in the sim (not a perfect test, by any means).  In the sim, a loss of one engine from 50ft is hard to land safely--likely survivable, but not going to be pretty.  At 100+AGL, the remaining engine gives you enough power to do a quick dive/flare to a half-way decent landing. A dual engine failure from the same altitudes would be uglier, as you would not have airspeed for a flare, and would have a high sink rate.  If you leveled and pulled the guts out before impact, you MIGHT be more or less OK, depending on exact specifics.  So, this is mostly based on the sim, as the taxpayers aren't eager to have crews damage/destroy birds just to see if they can pull off stuff in unexpected ways.  From a few the mishap records, yes, you can sometimes perform a decent auto from the shaded region, but it's not a certainty by any means.  The HV diagram does build in allowances for pilot skill, so if you are superman, the edges of the shaded region might get a little smaller (if you ate your wheaties that day).

Which people would they be, and what evidence/data are they presenting?  I've never seen test data or compiled mishap stats to back up a claim like that.

I know guys who had a tail rotor failure during an approach, and all walked away.  They were well inside the HV shaded region, but the aircraft still did a decent enough auto (but rolled due to impacting at an angle).  So, I'm not saying "you always die if you auto from the shaded region," but your odds of a successful auto (damage free or minimal injury) goes way down at low airspeed/med altitudes.

The 212/-N is like driving a classic car.  Not as fancy as the new stuff, but a lot of fun to fly.  Also, 50 years of flight time on the model makes for very few surprises, which is nice!
I fly for the Air Force.

HV curves are developed experimentally by test pilots in accordance with whatever parameters the airworthiness authority sets.  
There is a lot of assumptions and human variability that go into making them.  It's not a black and white line, there is a lot of grey area.

The test pilots are probably more skilled and proficient than you and will have done HV curve development many times.  They assume a reaction time that you may or may not meet.  They have smooth concrete under them, never have a tailwind, etc.  They judge what they think an "average" pilot is capable of and that's how the line is drawn.

I don't believe you.

I don't care if you believe me.  I don't really have a dog in this fight, nor a reason to make it up.  Radar altimeter in 206L said 50ft, and the 44 and the 47 were guesstimates.   Go to the factory schools and then report back.

https://www.flightglobal.com/news/articles/easa-warns-on-aw169-tail-rotor-safety-453427/

The 429 had a similar incident in china.  Following that it was discovered that there was an issue with the bolts that hold the gear box on.

In this thread I grasp about twenty percent of what is said.

I do understand that swinging lots of aluminum as in a Bell 212 aka UH1 is a very good thing.

For clarification, I was asking who is claiming autos from anywhere on the HV diagram are survivable, not who develops the HV diagram.

At what point, after losing a tail rotor, does the g forces of a spin render occupants unconscious, or at the last unable to do anything meaningful?

Not enough G’s to do that...

You would get to live the entire experance

You won't be sitting far enough away from the point of rotation to experience enough G's to knock you out.  The bigger issue will be centrifugal force, which will force the pilot/SIC to the outside of the spin which would  cause anyone with a grasp on the collective to push down on it, increasing the rate of decent, and making the problem worse.

The pilots here had to recognize and then fix possible collective PIO after the mechanical failure, chase the nose with the cyclic, and somehow stop leaning on the collective.  A helicopter isn't just going to fall out of the sky after a t/r failure.  In theory, the helicopter should still fly/hover with the fuselage spinning provided you can keep some sort of control of it.  The insane difficulty of trying to hover while the fuselage is spinning is another matter.  These guys either tried entering an autorotation or someone was leaning on the collective.  The spin seemed to be fairly flat and the collective could have been used to cushion the landing at the bottom provided one of the pilots didn't have it pinned to the floor because of centrifugal force.

Everyone on board in this crash survived:

My rotorcraft time is a whopping 0.5 But I don't buy into that theory! Shoulder harnesses keep everyone off the cyclic plus the leverage you gain while trying bend the rudder peddles to correct yaw is going to keep you away.

And NO, the helicopter cannot fly for long spinning as the equal and opposite forces will eventually cause rotor RPM loss as the fuselage starts to catch up to the rotor RPM. The transmission can only spin the rotor as long as it has something to push against.

The pitch extrusions in the China video were more likely a result of over controlling the cyclic from the disorientation and panic. There was some pretty exciting coning of the rotor going on there too, wonder if that was also pilot induced?

Rotorhead84 please note that I am not arguing or saying your wrong, just presenting another point of view. I will appreciate your views to this.

I'm not selling anything.  You're free to believe whatever nonsense you want.

I'll stick to proven accurate data and testing by people way more skilled and qualified than me.

Yes it can.  The fuselage will never nearly spin as fast as the rotor because all the vertical fuselage area is damping in the yaw axis.  The engine will govern the rotor to the set speed relative to the fuselage, if the fuselage is spinning opposite then the rotor will slow down relative to the inertial reference(air/earth), this will cause more rotor coning than if the fuselage was not spinning.  But  humans are unpredictable so no telling what a pilot might do with the collective.

There are many videos of tail rotor failures at OGE altitudes on YouTube and you  can clearly see in many of them that the fuselage reaches a (very low) steady state yaw rate very quickly when the helicopter is vertically descending.   In many of them you can also see the rotor cone even at flat pitch/low power settings due to the slightly reduced absolute rotor speed.

Rotorhead84 is 100% correct. And I hope I'm never one of those who are tested by this failure mode. It's not something easily trained for except in a simulator and even then you are not going to get the same centrifugal force effects or spatial cues (or spatial disorientation!)

US built helicopters will spin their fuselage CW (viewed from above) forcing body weight to the left.
This will affect the both the cyclic and collective, but mostly the collective, shoulder harnesses not withstanding. And some helicopters do not have shoulder harnesses.
There is also the emotional desire to be on the ground right now.
Left unchecked, the fuselage will not attain even a small fraction of rotor speed.
Assuming a large, unobstructed area to land in, there is little penalty for letting it spin until into ground effect, pausing there and chopping the throttle.
The problem is to do this into a place reasonable to land in and getting it all just right while in the aviation equivalent of a washing machine on spin cycle.
There is a world of difference between this happening at low speed and altitude vs. cruise speed at 1000 AGL. At low speed/altitude good luck entering an auto or chasing the tail with the cyclic to pull out of it. At cruise chase the tail, if necessary, enter an auto and be done with it.

Again, all big talk from this low hours Robinson pilot, hope I never have to put my money where my mouth is!

Pro tip:  If you wear your shoulder harness tight enough to keep you off the collective in a scenario like this, you'll never be able to reach your coffee in the cup holder.

Thanks for the input gang.

I went out with my instructor and, among other things, did what I would term "intro to stuck or failed tail rotor" in the 44 this past Wed. In a hover wasn't too bad, just roll it off and hover auto, as long as you didn't wait so long it got crazy. A bit higher than that, chasing it around with the cyclic while gaining altitude and airspeed so you have a prayer of getting it to a place where you can start an auto was quite a bit more challenging

Not a Robie pilot, but be careful with that...more than one has had tail boom strikes, and that maneuver sounds like a recipe for large deviations between fuselage and rotor disk angles...

Not at all, not to worry. First, we don't let the rotation rates get that crazy. Second, the amount of cyclic motion required to follow the spin is not significant (assuming one does not panic, of course). No panic required, it's only a training maneuver easily exited by the instructor taking his heavy ass foot off of the pedal in a proper, controlled manner, and properly exited in short order if things are not proceeding to plan.

BTW, my instructor for advanced evolutions of this nature is a 10,000+ hour Robinson pilot, not (with all due respect to CFIs--I will never be one!) a 200 hour, newly minted CFI. I trust him pretty well.

Report is out:

https://assets.publishing.service.gov.uk/media/5c090ab1e5274a0b64c8a2f4/S2-2018_G-VSKP.pdf

NOT T/R drive failure
NOT Loss of T/R effectiveness
NOT Loss of the T/R (e.g. blade failure)

...Loss of T/R control (which means all/both blades usually go to a neutral pitch)

Discuss!

Many military helicopters have centering springs on the tail rotor sloppy links that will position the tail rotor at some intermediate thrust setting that will allow a rolling landing to avoid this exact problem when battle damage severs the tail rotor controls.

In fact, one design requirement of the Blackhawk was that the helicopter had to operate 100% normally after failure of any component.  The Blackhawk tail rotor is mostly cable controlled, the cables are under spring tension with the springs enabling normal operation with only one cable.  The pilot has no way  of knowing if one of the cables is severed, so they added a warning light  to indicate loss of redundancy In the tail rotor flight controls.

Didn't know that.....very cool.

Unfortunately for this one, it looks like the failure would have been downstream of those components (not sure if anything like that was on this helicopter, but judging how it started spinning it, probably not)

https://www.bbc.com/news/uk-england-46471934


The helicopter which crashed killing Leicester City's chairman and four others spun out of control after a mechanism became disconnected, investigators said.

An Air Accident Investigation Branch (AAIB) report found cockpit pedals had disconnected from the tail rotor.

This caused the AW169 aircraft to turn uncontrollably to the right before it crashed near the King Power Stadium.

The AAIB said its inquiries into the 27 October crash were ongoing.

...

An inspection at the crash site found parts of a mechanism linking the pilot's pedals to the tail rotor had become disconnected and there was a "build-up of black grease" on one component.

The failure of the system led to the pitch of the tail rotor blades being changed "until they reached the physical limit of their travel".

The report stated: "The initiating cause and exact sequence of the failure that resulted in the loss of tail rotor control is being investigated as a priority."

...

Widely shared video footage of the helicopter's last flight, taken from inside the King Power Stadium, shows the AgustaWestland AW169 climbing normally for about 40 seconds before it pauses and goes into a downward spin.

The aircraft reached an altitude of approximately 430ft then crashed to the ground.