Scary situation on rooftop-helipad

[skadi]

A B412 encontered severe vibrations after unloading a patient on the rooftop of the Innsbruck/Austria hospital.

Video:
Video: So trudelte der Heli am Klinikdach - oesterreich.ORF.at (http://tirol.orf.at/stories/503296/)

skadi

[9Aplus]

Vauuuuuuu, lucky people...on board

that is much more than simple ground resonance....:eek:

[krypton_john]

Yikes. What happened next?

[skadi]

Yikes. What happened next?

The pilot flew the helicopter to the airport of Insbruck...

skadi

[ShyTorque]

that is much more than simple ground resonance....

:confused:

Resonance needs one vital thing to be classified as ground resonance...

I.e. The ground. This was airborne!

Looks like a partial loss of main rotor control.

[OvertHawk]

Agree that it does not look like ground resonance. Bearing in mind that there appears to have been loading / unloading going on, could it have been an inadvertent control input or obstructed control??

After the lift-off there seems to be a phase of more controlled flight followed by a second big deviation???

Very scary...

OH

[rotornut]

Reminds me of my first lesson when I was given the controls by the instructor:eek:

[tecpilot]

I bet there was a problem with the pilot and never in life could this be called ground resonance.

Looks to me like the pilot wasn't able to grab the controls right for a time. Reallys sure he and not a pax was initially on stick and pitch? May be they unloaded the doc and leaving the patient alone on the controls?

BTW, why do they unload the ship in the middle of a rooftop on full power?

[Gordy]

Almost looks like a red blanket gets sucked out of the open door on the right and into the blades. I blew it up but could not tell clearly.

Edited to add: I slowed it down and now could look like red smoke....

[9Aplus]

Try like this.....
use: In externem Player öffnen (mms://stream2.orf.at/filehandler/oesterreich/201110/hubi_neu-1_146487.wmv)
than put 200% size in Win media player
than slow speed down to 0,5
than you can see that all started with ground resonance
than main rotor rise up in front, and airframe follows
and after that was "fight" with pedals after collective wild rise up
:ouch:

[IntheTin]

That is a leased GHC 412 judging by the colours.....

Helipilots not engaged maybe?

[Non-PC Plod]

Not familiar with the type - dont know how it flies without the helipilot engaged, but it does appear to behave a lot like many aircraft do when they take off with no stabilisation.
This would seem to fit with the ground resonance theory - if resonance hits, you would take off pretty quick, probably without time to engage helipilots, let alone do any other checks!

[Brian Abraham]

I'm with IntheTin, helipilots not engaged. Have a few hours in the aircraft and even with helipiots engaged was still something of a twitchy beast.

[malabo]

He took off without closing the doors or waiting for the people standing around to move aside, or turning the helipilots on. Ground resonance could be a reason for him doing that. Maybe next time he'll leave the hp's on, and maybe check up slightly on the collective instead of keeping it all the way at the bottom.

412 isn't that bad without the hp's turned on, no worse than a 76. You can usually hover both without scaring anyone and reach down and turn them on. Helps if you've done it once or twice before.

[arica]

On 9th of March a Bell 412 of HELIAUSTRIA (Knaus) had a severe incident after landing on UNI Klinik Innsbruck. Does anyone of the community have an idea, what the reason for this rodeo could be? Media say something about "Ground ressonance". YouTube - hubi neu-1_146487[1].wmv (http://www.youtube.com/results?search_query=hubi%20neu-1_146487%5B1%5D.wmv&search=Search&sa=X&oi=spell&resnum=0&spell=1)

[skadi]

According to a newsreport the B412 showed no mechanical malfunktion/damage after the inspection at the Innsbruck Airport...

skadi

[Savoia]

.
From the clip there is zero evidence of ground resonance.

The take-off (if you can call it that) lacked any yaw control and the initial cyclic response was inappropriate leading me to suspect that a) this was an unplanned take-off (collective inadvertently manipulated) or b) the pilot allowed his 7 year old son to make his first attempt at flying a helicopter.

S.

[9Aplus]

Dear Savoia,
just please watch carefully tail position against horizontal helipad, from sec 2 to sec 6 and reconsider your statement....

[Savoia]

.
9A+ I'm sorry but I just can't see it. Even when I zoom my screen to 200% the clip remains the same size.

I guess we shall find out eventually!

S.

[Never in Balance]

does anyone have a link to the video on youtube?

[170']

If it was GR? (impossible to tell from a video; as it only shows up clearly on video when it's pretty much passed the recovery stage) quick action on the part of the pilot prevented this becoming far more dramatic... My own choice on an elevated helipad would also be to take it airborne rather than try to shut it down quickly (being shaken off the roof with engines spooling down and rotor brake coming on doesn't appeal much :eek:

I can easily imagine him looking back to check how the unloading is going and experiencing a skid settling,incipient GR event, and struggling to get into a normal seating position and fly the machine off at the same time...Just supposition on my part...

Looks like He did an good job to me...

[tecpilot]

I bet this was a surprising not controlled take-off and the pilot was at least not standing in the pedals. The ships turns like a humming top.
That uncontrolled a/c is not initiated by ground resonance and this was not a pilot controlled take-off. The a/c was short before to kill the guy standing on the left skid and stuffing things into the cabin. Not the most stupid pilot would eject his ship in such manner into the air knowing his mate is unsecured on the skid, head inside the cabin on a more than 50m high rooftop.

May be there was something wrong with the pilot seat, bringing the pilot out of rudder control.

The austro control (CAA) examination found yesterday no mechanical faults on the ship.

[K_9]

:confused:

Resonance needs one vital thing to be classified as ground resonance...

I.e. The ground. This was airborne!
I think a hospital rooftop will suffice. :p

[2dogz]

Maybe Hog was havin another go!

[ShyTorque]

I think some folk don't understand what ground resonance is. There was a similar discussion some time ago about another supposed "ground resonance" incident when an Agusta 109 chopped off its own tail after "*landing*". I said immediately that it wasn't ground resonance but others insisted it must have been. Read *very heavy landing* causing structural failure...

Ground resonance cannot, by definition, continue once the wheels / skids are off the ground. This aircraft wasn't in contact with the helipad during its gyrations. Things got very much worse once lift off took place.

The video quality is quite poor. However, it does look like something got drawn up into the main rotors. This might just be a function of video "colour bleeding".

[9Aplus]

Agree on your stand that after aircraft left ground "Ground Resonance"
can not be considered but please advise us what force
can push pilot to take of like that, all after that - we can fully agree :hmm:

Lucky chain was initiated with GR, after "escape" from GR was partial
lost of control aka "rodeo drive"....

[hostile]

Don't know about 412 systems, but how about collective trim hardover? surprised a pilot totally.

Just thinking,

Hostile:ok:

[SLINGKING]

ok try this link

Video: So trudelte der Heli am Klinikdach - oesterreich.ORF.at (http://tirol.orf.at/stories/503296/)


Video: So trudelte der Heli am Klinikdach - oesterreich.ORF.at (http://tirol.orf.at/stories/503296/)

[SLINGKING]

the failure on this is called " no sim no sim no sim "

[SLINGKING]

the authority is not really a authority

[K_9]

I think some folk don't understand what ground resonance is. There was a similar discussion some time ago about another supposed "ground resonance" incident when an Agusta 109 chopped off its own tail after "*landing*". I said immediately that it wasn't ground resonance but others insisted it must have been. Read *very heavy landing* causing structural failure...

Ground resonance cannot, by definition, continue once the wheels / skids are off the ground. This aircraft wasn't in contact with the helipad during its gyrations. Things got very much worse once lift off took place.

The video quality is quite poor. However, it does look like something got drawn up into the main rotors. This might just be a function of video "colour bleeding".
Are you arguing the semantics of it (saying that "If the aircraft is not on the ground then it can't be ground resonance!") or are you saying that the resonance phenomenon commonly known as ground resonance cannot occur even when hovering just above the ground? I'm a fixed-wing guy and I know that, but I've also taken a class or two dealing with rotary-wing flight. I'm going to need some convincing if I'm going to believe that a resonance condition between a rotor and a wall (the ground or hospital roof) can occur when the rotor is 10 feet from the wall but is impossible when the rotor is 15 feet from the wall.

[the coyote]

You must be in contact with the ground (or any other surface) to experience ground resonance. Once contact with the ground is severed the resonance ceases, and the rotor system will return to a balanced state.

I would have doubted that the 412 with its unique rotor head could experience significant ground resonance, given the elastomeric dampers only allow limited movement in lead and lag, however it is technically possible.

[TRC]

"If the aircraft is not on the ground then it can't be ground resonance!")

The clue is in the name - GROUND resonance.

It is an inter-reaction between the undercarriage and the main rotor that can sometimes occur to a helicopter with an articulating main rotor. It only happens on the ground, not in flight.

[K_9]

Okay, I had the terminology wrong. What I was thinking of was more of a ground interference aerodynamic resonance situation, where a wave of air being directed downward by each blade pass can reflect back up from the ground and, in the resonance case, meet up with the next blade. This obviously requires being close to the ground (a rotor diameter or so), but does not require being on the ground. Only occurs in a hover or in certain cases of slow translational flight with a following wind to match. Much less common than ground resonance (dynamic instability of the rotating structure).

[Savoia]

.
To add further clarity ..

6vICf8l-KV0
This is what it looks like (even on a roof pad) and how to get out of it. Like mast bumping in the 'teetering' Bell's - you've got milliseconds to respond to this phenomenon.

RihcJR0zvfM&NR=1
And this is what it looks like when you don't take corrective action.

S.

[TRC]

.... ground interference aerodynamic resonance situation, where a wave of air being directed downward by each blade pass can reflect back up from the ground and, in the resonance case, meet up with the next blade


Never heard of that phenomenon - have seen several cases G.R. (on the ground of course) recovered without harm, but not the one you describe.

Re-circulation from nearby walls isn't going to manifest itself as a condition like G.R., and I can't see how a downbeat of air from a blade of a hovering helicopter could 'bounce' back up and interfere with the following blade - have a look at a diagram of rotor downwash in the hover and you'll see why.

If you theory is correct, how would any helicopter manage to land or take-off without looking like the one in the video?

[ShyTorque]

Ground resonance occurs when an out of balance main rotor interacts with the helicopter undercarriage. This can occur due to poor design or a temporary issue, or a combination of issues, such as a failed main blade lead/lag damper, and/or a wrongly pressurised tyre or oleo leg.

The centre of gravity of the rotating mass becomes divergently displaced until the helicopter either shakes itself to pieces, or rocks from side to side over its undercarriage, so far that it rolls over.

In this situation, as soon as the helicopter leaves the ground, the rolling moment is removed because the undercarriage is no longer in the equation.

In an instance where something big and draggy (like a blanket) flies into the main rotor, the affected blades may well lag back against their damper back stop, causing an out of balance rotor with no damping to help recover the situation. This could set off ground resonance. If the pilot now lifts off, the drag from the blanket will continue to cause aerodynamic issues. It's easy to imagine why the helicopter will "rock and roll" in the air (once experienced, never forgotten, believe me, I've had this happen).

But how it might also cause yawing as it did in this case, is less easy to explain. Unless it caused so much blade drag that Nr was lost and a subsequent loss of tail rotor effectiveness was also experienced. OR the pilot lifted to the hover before rotor rpm was was up to normal.

Air resonance can occur when carrying a large underslung load, btw. The weight/inertia of the load has the effect of "tethering" the helicopter, in a similar way to the undercarriage when the helicopter is on the ground. Again it would need a "trigger" such as a failed blade damper.

Here's a useful link: http://www.asl.ethz.ch/education/master/aircraft/2010-L8-Rotorhead.pdf

[K_9]

I understand how vibrations and resonance occurs in structures and I'm familiar with how the added mass of a payload or the interference of the ground with the helicopter structure can change the characteristics to allow ground resonance to occur.

The other case I mentioned (aerodynamic resonance) is something we briefly discussed in a lower-level class I took several years ago, but I'm not knowledgeable enough on the subject to offer any more of an explanation than I already have. My academic areas of expertise are design, aerodynamics, and propulsion of airplanes; I work in flight controls and hydraulic systems design and certification. :)

[SLINGKING]

i actually was flying with a other pilot this machine in aerial work and we grounded this machine due to the bad maintenance, this WAS a part of the whole situation the resonance, but further more the incompetence due to lack of training.

the company has a reputation u even wont have as crash test dummy

[SLINGKING]

the whole szenario was waitign when knowing the background but i assume this would not be so interesting since it is a longer story

[Hedge36]

I hate to toss the mundane into this conversation, as lively and enlightening as it is... but for all we know, it could simply be a matter of "I dropped my pen, bent to pick it up and wrapped my helmet cord around the controls."

It'll be interesting to hear the whole story.

[farsouth]

Between 00:12 and 00:16 in the film clip seems to show something (blanket???) blowing down from the rotors (tail rotor area???) onto the helipad and then off to the right of screen. Seems a likely contributing factor.......

[Gordy]

Seems a likely contributing factor.......

Yeah, I said that back in post # 9....I guess only you and me see it.....

[9Aplus]

Yep, in my 0,5 slow down and 200% size, that look like sheets of paper,
source likely slide door, still wide open :confused:

[alouette]

Both sliding doors were wide open. Imagine if somebody would have been in the cabin without having buckled up...:eek:

[ShyTorque]

Yeah, I said that back in post # 9....I guess only you and me see it.....

Read my post, #25.

[Gordy]

ShyTorque

Read my post, #25.

Missed it sorry....and going back and looking again, you are probably right. I was concentrating too much on the "red". I can now see the "green" doing the same.

[Savoia]

.
Gordy; what number do you see?

http://uitrends.com/wp-content/uploads/2009/12/color_blindness_test1.jpg

:E

S.

[Epiphany]

Maybe next time he'll leave the hp's on, and maybe check up slightly on the collective instead of keeping it all the way at the bottom.

They were my thoughts Malabo. The 412 can start a nasty 'bounce' on a hard surface that a small application of collective can fix. Fortunately I was shown that before it happened to me the first time. If a pilot was unaware then the 'bounce' could be very alarming and prompt a quick take off. If the Helipilots (Bell AP's) were not engaged then this might well have caused the very exciting departure in the video.

[smile 412]

You are absolutely right Epiphany this could be a lack of training or experience on Bell 412.:confused:

[412hunter]

Taking off with the helipilots not engaged is no biggy, just a little more wobbly.
That to me looks like he was just about to get airborne and the seat slid fully backward, which can happen if the adjustment locking pin isn't fully engaged - and it travels a fair way back! That would explain the leap into the air and little or no tail rotor control. The sideways jerk is a result of an attempt to get the seat slid back forward?? I always check the seats locked post seat movement - pre start. My 2 cents.

[maeroda]

Epiphany and other drivers down here talking about the 412 bounce at MPOG and the slight two inches of pitch to be pulled to fix it are damm right to me!

I usually fly a pair of EP's, allmost identical twins ships; they have the same bounce attitude at start up and minimum pitch on ground.
The only change is my arse-feeling of the onset of that vibration.

Not assuming the bounce onset is what happened on the roofpad in Insbruck, I simply don't have any information about it apart what I see in the video.
The "red blanket" is the red of the paint scheme of the ship being defocused by the relative small definition of the video.

Just saying that the inadventent bounce onset + some AP's disingaged for any reason (may be inverter OFF check) + the brutal pitch pull on a 15 floors building (pinnacle) without strong visual references in a ****-scary moment may be the explanation of what had happen and COULD happen to every 412 driver with less than desired experience.

[bb in ca]

I can't believe collective bounce or ground resonance are being considered by Ppruners. Looking forward to some follow up information from the people involved or the authorities.

[tottigol]

Aaahhh, the notorious 412 collective bounce, any pilot with enough time in the 412 is fully aware of it.
Some other issues may have added to it though, little or no collective friction, HPs off, a possible droop restraint engaging at a time when it was not supposed to do so, and yes a seat sliding back beyond reach of the pedals.
Was the pilot accelerating from idle (77%), after dropping off the patient or did he/she maintain the RPMs up all the time?

[verticalspin]

reports say, that he was idling for noise abatement when unloading the patient.
the pilot has 8000 hours. don't know how many of those are on the 412 since that machine is fairly new to their fleet.
they did tests on the machine for the last couple of days but couldn't find anything wrong with it. the 412 is now up and flying again!

[Epiphany]

Taking off with the helipilots not engaged is no biggy, just a little more wobbly.

Maybe if you are doing it intentionally but unintentionally after a scary bouncing episode - I think not.

[412hunter]

Certainly the ground bounce, if you don't do something about it, gets very scary very quickly, but that doesn't explain little or no T/r control.

[SLINGKING]

some month before basically the helicopter got grounded due to the state of condition. this led to a change of the crew and suddenly this was a incident not coming on surprise

with all this asumptions and speculations, facts need to be stated before finding the reason of the failure on the machine itself.
even a pilot with 12 000 h , 4000h on type and a techn. License current on 412 flying this machine was ignored by the operator and fired after pointing out the problem under which the helicopter was assuemd by the owner to be airworthy and ready for operation !

also was not implemented the additional needs of procedures different from the other helicopters ( if there where any at all ) like the 204 they operate( 50 % crashed ), 205 crashed, Alouettte III crashed, AS 350 with full throttle on ground without pilot turned upside down, a Lama with undereducated pilot into cable ( sölden, 8+dead) and the Rescue Helicopters As355 ( crashed ) and MD 902 ( crashed ), 212 blades into ground, according to regulations expressed in the OM approved by the local CAA. instead they made a own over the thumb checklist. so the devil was in the detail and not hiding somehwere. this information i stated above was googled after looking in the accident reports in austria and when researching what was happening to each helicopter in the company. so it is free and open resource and nomade up facts.

idling down, bouncing, not knowing to correct it and in panik lift off on half way to thottle full open make each take off interesting to watch. -> maybe next time a checklist shall be used if not sure how to do, prevents a lot of mistakes which each one can make, but in intention ignoring it is no excuse. especial this happend in innsbruck downtown.

as one can see the tail IS going up and down, the wild movement of the tail are most lilely the fast winding of the throttle. the fast take off the instinkt of a pilot who flew many years lama known for grounsresonance and the required action needed. additional a takeoff with the AP´s off so inputs like the left roll is a result, which was several time observed as mistake without checklist. again it is easy to make a mistake but be permanent resistant to inputs form experienced 412 pilots/ 412 ingenieurs and TRE doenst change the level. google the history or heli austria ( known before as Knaus Helicopter , Heli Triol, Heli austria, Ländle Heli).
after researching this the view is a other one.

so one still thinking this is just bad luck?

[412hunter]

Wow, interesting safety culture and history in that company.:eek:
Nearly added a B412 to the impressive 'crashed' list.

[SLINGKING]

well if u know the austrian CAA u wont expect anything usefull

[TrT]

Well with my big lack in knowledge of flying twins and the 412.. I thought i would give it a shot as everyone else has done here. Right yaw to me indicates a tail problem... Was not on the pedals when got airborne for some reason and possibly kicked in loads of left, the wind didnt help the situation(LTE? whats the chances of Lte on a machine like this?). Anything kick up into the tail rotor? We cant see much. But this to me looks like a tail problem or pilot pedal problem. Is there chance you spool down one engine and not the other and he got airborne meaning he had lack of rpm and tail authority. Once again I point out out my lack of knowledge of twins and the 412.

[maeroda]

ASN Aircraft accident 09-MAR-2011 Bell 412 OE-XYY (http://aviation-safety.net/wikibase/wiki.php?id=121093)

Date:09-MAR-2011 Time:10:45 LT Type:Bell 412 (http://aviation-safety.net/wikibase/dblist.php?AcType=B412) Operator:Heli Austria Registration: OE-XYY C/n / msn: 36041 Fatalities:Fatalities: 0 / Occupants: 3 Other fatalities:0 Airplane damage: Unknown Location:Innsbruck Hospital Helipad - http://aviation-safety.net/database/country/flags_15/OE.gif Austria (http://aviation-safety.net/wikibase/dblist.php?Country=OE) Phase: Take off Nature:Ambulance Departure airport:Innsbruck Hospital Destination airport:LOWI Narrative:
The Bell 412 helicopter had finished unloading a patient at the helipad of Innsbruck hospital (54m above ground) near town center of Innsbruck, when strong resonances occurred in the helicopter which led to an uncontrolled take-off. The pilot managed to get the helicopter under control and made an emergency landing at nearby Innsbruck airport, where again strong resonances occurred.

The Bell 412 is in use by Heli Austria only since July 2010.

[toptobottom]

I can see what ST and Gordy mean by something caught in the MR, but I'm convinced this is just colour bleed in the poor quality rendering. I've been through it, frame by frame and the red (and green) colour is almost always only seen on the right hand side of the image, regardles of the machine's attitude.

http://i851.photobucket.com/albums/ab71/prooner/412a.jpg

It does yaw slightly to the right before it lifts possibly indicating the uncommanded (and unexpected) rise of the collective? The weird bit though, is the very aggressive left roll in the middle of the 15th second. That has nowt to do with TR control, but a mighty bucket load of left cyclic!!