What is the latest information re Bond's Loss of Rotor Head crash on the North Sea?

[SASless]

Last I heard the AAIB had determined "What" happened.....but have they determined "Why" it happened?

What measures have been put in place as a result of that tragic crash and have there been any significant findings since they were done?

Can we be assured the situation is resolved following technical improvements, procedural changes, or by other means?

[VeeAny]

Sasless expect the report soon.

I know those who are entitled to see it prior to publication have seen it and I think their comments where due back to the AAIB by end of July.

I guess it depends on whether any comments made by those people or companies will affect the content, as to how long it will take to release to the public.

[SASless]

It should make for interesting reading. We just don't expect MGB's to come apart anymore unless something very unusual acts to cause them to do so.

One would like to think these kinds of tragedies could be prevented as the industry matures.

[SASless]

Bond has settled with the Next of Kin of the Pilots killed in the crash.


Bond helicopter firm settles with partners of pilots killed in crash | Aberdeen & North | News | STV

[riff_raff]

"....The accident happened when the main rotor broke off, as a result gearbox failure, and severed the aircraft's tail boom....."

The description of the accident in the article seems a bit silly. The "main rotor broke off.....and severed the aircraft's tail boom". Once the main rotor separated from the aircraft, what significance does the impact with the tail boom have? Are we to believe that the aircraft would have been able to maintain stable flight had the departing main rotor not severed the tail boom?

Catastrophic structural failures of main rotor shafts/bearings should be an extremely rare event if modern design, manufacturing QA, and maintenance procedures are followed. Long before that main rotor shaft suffered structural failure, the MRGB HUMS should have given an indication of a problem.

[HeliComparator]

Long before that main rotor shaft suffered structural failure, the MRGB HUMS should have given an indication of a problem.

If only! As I understand it the defect originated in a planet gear which of course as well as rotating itself, is also travelling around the epicyclic. Therefore one point of the gear (where the crack was developing) follows a complex path which only repeats at relatively infrequent intervals. If you understand how the signal averaging techniques (used to extract data on a specific item using external sensors) works, you would know that this problem would result in very long acquisition times to get enough data for the signal averaging to work. That means lots of memory and a requirement to maintain stable flight conditions for a long time. This is not impossible, just difficult and thus not designed into HUMS technology whose concepts were developed in the 1990s.

One of the self-inflicted injuries of HUMS is that, whilst it is good, it is not a panacea and when an accident occurs that HUMS did to detect, it is ridiculed by the disbelievers. All the accidents that would have happened without HUMS are not taken into account.

[[email protected]]

But a crack in a gear should still change the vibration signature of the gearbox and at least hint that something is wrong - just as you know a bowl or cup is cracked because it sounds different when you tap or knock it, even if you can't see it and it hasn't broken yet.

Otherwise you are saying there is no method of detecting similar problems and the same failure could occur at any time!

[Hummingfrog]

Crab

the vibration signature of the gearbox

A gearbox doesn't have a single vibration signature it has hundreds depending on what flight regime it is experiencing. As HeliComparator said it developed in a gear which follows a complex path in the gearbox whose signature must be very complex.

HUMS forecasting is a bit like weather forecasting the more info you can get and the nearer the time to an event the better your forecast will be of that event.

It is a very good system and is getting better all the time as information is gathered but it is still at the stage of an early AMSTRAD compared to present day PCs.

The major clue to this failure of the gearbox was the flake of metal it made and the influence of magnets in the gearbox on finding flakes of metal.

HF

[HeliComparator]

Crab, I guess you don't understand how signal averaging allows the extraction of the vibration relating to a specific element (shaft, gear etc) within a gearbox. I suggest you look it up!

So yes, the same could happen again if the early warning sign of a chip is ignored. In many ways debris monitoring (chip detection etc) and HUMS (detection of non-debris releasing defects) complement each other to cover most, but not all, eventualities.

[Soave_Pilot]

I am with Hummingfrog on this one too...

Also in my view:

Taking an action of ditching a helicopter only because of a vibration is somewhat precipitated... Unless is something moderate to extreme of course.

Ditching a Helicopter only because of a MR chip light is also somewhat precipitated (as it could be a sensor failure).

Now... Ditching a Helicopter because of a MR chip light + vibration is something vey well explainable.

What sign did the crew have? I guess we will have to wait for the report...

[industry insider]

Soave

The report was published by the AAIB on November 24th 2011. Its an interesting read. HUMS is being developed to provide AAD but its a slow process. Does anyone do SOAP anymore in addition to HUMS and debris monitoring?

[DonQuixote23]

Could a possible action in the event of either an MR chip light or vibrations be to go down to very low altitude and slowly limp home? At least in that case if something goes totally pear-shaped the fall is survivable.

[Jetboxer]

DonQuixote23,

Could a possible action in the event of either an MR chip light or vibrations be to go down to very low altitude and slowly limp home? At least in that case if something goes totally pear-shaped the fall is survivable.

In this case, unfortunately, the crew had neither of these indications prior to a catastrophic failure.

http://www.aaib.gov.uk/cms_resources...1%20G-REDL.pdf

[HeliComparator]

II - although AAD is in being, it works by evaluating existing HUMS parameters. As far as I am aware there are no parameters for planet gear health, for the reasons explained, so unfortunately AAD would not help in this particular scenario.

DQ, in a word, no, not if survival was your intention.

[DonQuixote23]

"DQ, in a word, no, not if survival was your intention."

Due to? Not enough time to deploy the floats?

[Old Age Pilot]

Could a possible action in the event of either an MR chip light or vibrations be to go down to very low altitude and slowly limp home? At least in that case if something goes totally pear-shaped the fall is survivable

Due to? Not enough time to deploy the floats?

Surely common sense comes into it here? How low are you thinking of going? What height would you expect to be able to fall from without getting hurt?

[Jetboxer]

DQ,

I think HC is hinting to the fact that with a MGB Chip light, and vibrations (and other related warnings indicating an imminent failure of the gearbox) it would be wiser (if survival was your primary goal) to carry out a controlled ditching, pop the floats and man the liferafts - very well demonstrated by a Bond EC225 crew earlier this year.

Rather than....

Flying along slow and low, 'limping' home - During this 'limping home' stage if the MGB were to fail catastrophically, I doubt there would be much time to do much, let alone pop the floats. The change in attitude of the aircraft, I'm guessing, would be dramatic.

[DonQuixote23]

Jetboxer - thanks. What happens with a heli that ditches without the floats. Is it so top-heavy that it immediately flips around and sinks quickly?

[212man]

DonQuixote23 Jetboxer - thanks. What happens with a heli that ditches without the floats. Is it so top-heavy that it immediately flips around and sinks quickly?

Basically, yes. Search for G-TIGH for a tragic example.

[SASless]

This topic....Limp or Ditch....has been done to death before. The Consensus was "Ditch" anytime you have more than a simple single indication such as a Chip Light.

The original mindset was a gearbox would give you some warning .....but as it has been proven that is not always the case....then a controlled ditching is far safer than experiencing a Catastrophic failure while in any stage of flight at any altitude or airspeed combination.