Heli crash, Honolulu, HI - video

[wasYKnowFJ]

Yikes!

https://youtu.be/MbhLWbs4PQ0

[looproll]

Wow, that thing sure slaps onto the water! I'm not a helicopter person, but it looks a lot like vortex ring state. I hope the teenager in critical condition makes a full recovery.

[YBW-Kid]

To me this somehow involves the tail rotor. In the slow monition portion, the tail rotor appears to stop, then reverses direction.

I'm not a helicopter expert. If you are in a near hover approaching to land when you experience a rotor failure, the only way to control the spin of the fuselage would be to reduce power? Of course reducing power in the hover would cause you to descend rapidly. Am I wrong in thinking this is what has happened here?

[godsrcrazy]

This was snot tail rotor failure. There is no one i know that could keep it from spinning if the tail rotor failed. There is no doubt by the sound of the turbine he didn't chop the power. This is "Vortex ring" also known as settling with power. The more power you pull the faster you go down. The only way out is drop the nose and gain forward air speed.

[Heliian]

This was a vortex ring state (VRS) accident by the looks of it. The water doesn't show much wind.

EDIT: not VRS by the sounds of the prelim report.

As for the tail rotor, the FPS rate of the video syncs with the rotational speed of the rotor. Almost every video looks like that.

[boeingboy]

It may be a VRS accident but there has to be more too it than that. This accident happened right in front of the pearl harbor visitor center. while there is a wide open space - they do not run helo ops out of it. He had to be making a precautionary landing for some reason.

Witnesses also stated hearing 2 bangs - like gunshots - right before it dropped out of the sky. Since the engine was still running - it could have been a transmission failure.

[ragbagflyer]

It appears to be in control until suddenly falling out of the sky. Also, there's no down wash on the water. Could it be that that collective was bottomed out for some reason or that some a part of the collectives linkage failed?

[godsrcrazy]

It appears to be in control until suddenly falling out of the sky. Also, there's no down wash on the water. Could it be that that collective was bottomed out for some reason or that some a part of the collectives linkage failed?

You will see little to no down wash in VRS. See the attached site. By the way the turbine was screaming i doubt the collective was push down. He was pulling all the power that C20 had. This from my arm chair.

http://www.copters.com/aero/settling.html

Settling with Power

Settling with Power is a condition of powered flight where the helicopter settles into its own downwash. The condition may also be referred to as the vortex ring state.
Conditions conducive to settling with power are a vertical or nearly vertical descent of at least 300 feet per minute and low forward airspeed. The rotor system must also be using some of the available engine power (from 20 to 100 percent) with insufficient power available to retard the sink rate. These conditions occur during approaches with a tailwind or during formation approaches when some aircraft are flying in turbulence from other aircraft.

Under the conditions described above, the helicopter may descend at a high rate which exceeds the normal downward induced flow rate of the inner blade sections. As a result, the airflow of the inner blade sections is upward relative to the disk. This produces a secondary vortex ring in addition to the normal tip vortex system. The secondary vortex ring is generated about the point on the blade where airflow changes from up to down. The result is an unsteady turbulent flow over a large area of the disk which causes loss of rotor efficiency even though power is still supplied from the engine.

This figure shows the induced flow along the blade span during normal hovering flight:



Downward velocity is highest at the blade tip where blade airspeed is highest. As blade airspeed decreases nearer the disk center, downward velocity is less. This figure shows the induced airflow velocity pattern along the blade span during a descent conducive to settling with power:



The descent is so rapid that induced flow at the inner portion of the blades is upward rather than downward. The upflow caused by the descent has overcome the downflow produced by blade rotation. If the helicopter descends under these conditions, with insufficient power to slow or stop the descent, it will enter the vortex ring state:



During the vortex ring state, roughness and loss of control is experienced because of the turbulent rotational flow on the blades and the unsteady shifting of the flow along the blade span.

This figure shows the relationship of horizontal speed versus vertical speed for a typical helicopter in a descent. Straight lines emanating from the upper left corner are lines of constant descent angle. Superimposed on this grid are flow state regions for the typical helicopter. From this illustration, several conclusions regarding the vortex ring state can be drawn:



The vortex ring state can be completely avoided by descending on flightpaths shallower than about 30 degrees (at any speed).
For steeper approaches, vortex ring state can be avoided by using a speed either faster or slower than the area of severe turbulence and thrust variation.
At very shallow angles of descent, the vortex ring wake is shed behind the helicopter.
At steep angles, the vortex ring wake is below the helicopter at slow rates of descent and above the helicopter at high rates of descent.
Power settling is an unstable condition. If allowed to continue, the sink rate will reach sufficient proportions for the flow to be entirely up through the rotor system. If continued, the rate of descent will reach extremely high rates. Recovery may be initiated during the early stages of power settling by putting on a large amount of excess power. During the early stages of power settling, the large amount of excess power may be sufficient to overcome the upflow near the center of the rotor. If the sink rate reaches a higher rate, power will not be available to break this upflow, and thus alter the vortex ring state of flow.
Normal tendency is for pilots to recover from a descent by application of collective pitch and power. If insufficient power is available for recovery, this action may aggravate power settling resulting in more turbulence and a higher rate of descent. Recovery can be accomplished by lowering collective pitch and increasing forward speed. Both of these methods of recovery require altitude to be successful.

[burhead1]

Cavitation! the short version. LOL

[PilotDAR]

Cavitation is a different affect than ring vortex state.

In the case of ring vortex state imagine the rotor slicing a bagel in haft from the middle of the hole. The air inside the volume of the bagel is recirculating through the portion of the rotor within it, and useless for creating lift. As the pilot pulls more power/collective the bagel puffs up, and envelopes more of the area of the rotor. If the pilot lowers the collective, and flies forward (consuming lots of altitude we hope he still has), the rotor will slice through the outside bagel (which volume rapidly diminishes), find undisturbed air, and lift can be restored by flying out through it. Cavitation is a vacuum being formed on the back of a propeller, main rotor blades don't pull that much power.

Hmmm, now I'm hungry....

[burhead1]

https://youtu.be/HrsGM0PzQFo

[youtube]https://www.youtube.com/watch?v=HrsGM0PzQFo[/youtube]

[Caracrane]

The 16 year's old kid passed away. Too bad.

[Nark]

I don't think it was settling with power.
I'm banking on mechanical failure of some sort. I'm thinking shaft failure.

From what I gather the 16year was under water for a long time, brain starved of O2. He had an extreme minimal chance of any meaningful life.

[Heliian]

WPR16FA072_Preliminary.pdf

(117.76 KiB) Downloaded 136 times

Prelim from the NTSB.

Doesn't sound like VRS, but more questions raised. Now I'm pissed they didn't have floats. If you are flying over water all the f ing time, get some GD floats!

[Meecka]

From the preliminary report, it sounds like he had a shaft failure. Shitty deal.

[boeingboy]

The pilot reported to the National Transportation Safety Board (NTSB) investigator-in-charge, that
while in cruise flight over Ford Island, he felt a vibration followed by a grinding noise. Shortly
after, the pilot heard a loud bang, scanned the instrument panel and saw that the engine instruments
indicated the engine was still running, however, rotor rpm decreasing. The pilot initiated an auto
rotation to a grassy area near Contemplation Circle at the World War II Valor in the Pacific National
Monument. As the pilot neared his intended landing area, he observed multiple people within the area.
The pilot stated he initiated a left pedal turn, attempting to land close to the shoreline.
Subsequently, the helicopter descended rapidly into the water, about 20 feet from the shoreline.

Like I said earlier - he was making and emergency landing.

I don't think floats would be needed. During their sightseeing tours they only follow shorelines and if they had a problem - they are within autorotation distance of land.

The fact he was making a landing approach from over the water when either the shaft let go completely or he ran out of lift when he executed a pedal turn was just dumb luck. He probably would have made it if the field was clear of people.

[Heliian]

Sounds like a freewheel failure.

He probably would have made it if the field was clear of people.

He would have made a safe water landing if he had floats and no one would be dead. As we all know, the gliding distance rule is abused to the point of being ineffective, as was the case here. Most of the other operators have floats and the big safety consortium the have demands it.

The short of it is that someone cheaped out on the floats, gambled, and lost.

[Meatservo]

Sounds like a freewheel failure.

He probably would have made it if the field was clear of people.

He would have made a safe water landing if he had floats and no one would be dead. As we all know, the gliding distance rule is abused to the point of being ineffective, as was the case here. Most of the other operators have floats and the big safety consortium the have demands it.

The short of it is that someone cheaped out on the floats, gambled, and lost.

Same problem as Sullenberger and Skiles, then, 'cept no-one died the time they "could" have glided to a spot on land but decided to go to the water instead so they wouldn't land on top of people (and buildings) . Cheap bastards. Floats for EVERYONE!

[boeingboy]

The short of it is that someone cheaped out on the floats, gambled, and lost.

did you even watch the video.......he was screwed no matter where he was. If he was over land they probably all would have died, he was just screwed from the get go as when everything went wrong he had no altitude to do anything with. They were just all along for the ride.

Yea - it's tragic the boy died....but this stuff happens. Should everyone be required to have floats because the might fly near a 100 ft wide lake or over a swimming pool, cause you never know - he might end up in it.

[godsrcrazy]

The short of it is that someone cheaped out on the floats, gambled, and lost.

did you even watch the video.......he was screwed no matter where he was. If he was over land they probably all would have died, he was just screwed from the get go as when everything went wrong he had no altitude to do anything with. They were just all along for the ride.

Yea - it's tragic the boy died....but this stuff happens. Should everyone be required to have floats because the might fly near a 100 ft wide lake or over a swimming pool, cause you never know - he might end up in it.

Plus 1. I doubt floats would have done him any good. They are not designed to take that impact. Even if he had land under him the gear etc would not have handled the impact. That was no normal autorotation. At least not any i have seen our been a part of.