'RAF helicopter on fire'
The results of the enquiry have been published
https://www.gov.uk/government/public...nowdonia-wales
https://www.gov.uk/government/public...nowdonia-wales
Jeez, it would take ye ole' Air Marshal a month of Sundays to read that report. So in a nutshell, what happened? Was it something about the landing that caused the MGB mounts to crack and shunt forward? Or was it extremely fortuitous they cracked when they did in proximity to the ground during the course of normal operation?
They could significantly shorten the Report.....by leaving blank....the pages "Intentionally Left Blank".
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Yup, quite a tome isn't it! And it still bugs me that the people/persons who wrote it refer to that fine operator known as Bristow Helicopters as "Bristows", FFS it's "Bristow."
Yeah I know, but the main question is, did it crack because of something the crew did during the landing manoeuvre, or did it crack for other reasons and they were just lucky it cracked when it did and not whilst in flight?
Gross simplification having read the report this morning.
The final cracking was probably caused by the manoeuvring to land on the mountain side. However the crack would have been propagating for some time, at least since the last visual inspection. The MRG SC is an un-lifed component so wasn't captured in the recovery programme when it was realised that MoD's interpretation of the aircraft limits was wildly different from Bell's* and a recovery plan had been initiated to get everything back to a safe condition (this was in ~2009).
So definitely some element of luck in that the manoeuvring to land caused the final over stress, but the crack would have been growing for some time.
*Bell basically said 'Aerobatic manoeuvres prohibited' which MoD turned into a 90 degree pitch and bank limit. Bell later revised the Flight Manual to read something like 45 deg of bank and +30 -15 pitch, which resulted in MoD having a bit of a panic attack.
The final cracking was probably caused by the manoeuvring to land on the mountain side. However the crack would have been propagating for some time, at least since the last visual inspection. The MRG SC is an un-lifed component so wasn't captured in the recovery programme when it was realised that MoD's interpretation of the aircraft limits was wildly different from Bell's* and a recovery plan had been initiated to get everything back to a safe condition (this was in ~2009).
So definitely some element of luck in that the manoeuvring to land caused the final over stress, but the crack would have been growing for some time.
*Bell basically said 'Aerobatic manoeuvres prohibited' which MoD turned into a 90 degree pitch and bank limit. Bell later revised the Flight Manual to read something like 45 deg of bank and +30 -15 pitch, which resulted in MoD having a bit of a panic attack.
On point, Bing.
The DSA team did a thorough job investigating this situation and their report reads clearly. It's not their job to implement corrective actions however, and the results of their work leave a challenging situation for the user, the regulatory authorities, and to some extent, perhaps the manufacturer.
Para 1.4.144/5 Maneuver Limits ought to raise the attention level of anyone involved in certification testing. Not pointing a finger at Bell. Users use, and stuff happens. I recall clearly the day when our CH-53A Project Pilot returned from a visit to the USMC MAWTS Squadron at Yuma, where they were teaching squadron pilots on how to use the maneuverability of the 53 to avoid enemy aircraft. He knew that our flight loads survey data didn't include what was going on there. Not close. Fixing that took some doing.
The DSA team did a thorough job investigating this situation and their report reads clearly. It's not their job to implement corrective actions however, and the results of their work leave a challenging situation for the user, the regulatory authorities, and to some extent, perhaps the manufacturer.
Para 1.4.144/5 Maneuver Limits ought to raise the attention level of anyone involved in certification testing. Not pointing a finger at Bell. Users use, and stuff happens. I recall clearly the day when our CH-53A Project Pilot returned from a visit to the USMC MAWTS Squadron at Yuma, where they were teaching squadron pilots on how to use the maneuverability of the 53 to avoid enemy aircraft. He knew that our flight loads survey data didn't include what was going on there. Not close. Fixing that took some doing.
It's a bit like selling someone a car that does 150mph and then complaining when they bring it back to you, broken, because they have been doing 150mph in it when you were expecting them to keep it to 70mph.
Revised Statements of Usage and Operational Intent have been the norm in UK mil aircraft - saw it in both the Lynx and the Sea King because the actual operational fatigue spectrum 'wasn't what it was designed for' and they needed more data. All despite being used within the limits of the ODM (RFM)
Revised Statements of Usage and Operational Intent have been the norm in UK mil aircraft - saw it in both the Lynx and the Sea King because the actual operational fatigue spectrum 'wasn't what it was designed for' and they needed more data. All despite being used within the limits of the ODM (RFM)
How long had that particular part been installed....and had it been subject to the excess loading in the past...and not removed from service?
Remember how the discussion went about the Bell 407 that was "Looped" and found itself grounded as a result?
If I had an entire fleet of aircraft that had been flown in excess of the design and certification standards used by the manufacturer I would be having Kittens as well.....when confronted with a historical practice that far exceeded those standards.
Who is the guilty party....the Ute Builder who spec's the vehicle at one half ton load or the owner who runs around with two tons on it?
Remember how the discussion went about the Bell 407 that was "Looped" and found itself grounded as a result?
If I had an entire fleet of aircraft that had been flown in excess of the design and certification standards used by the manufacturer I would be having Kittens as well.....when confronted with a historical practice that far exceeded those standards.
Who is the guilty party....the Ute Builder who spec's the vehicle at one half ton load or the owner who runs around with two tons on it?
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I think I read that of all the global events of the MGB SC cracking, this same airframe had one in 2006 which was discovered on a post-maintenance ground run where the engrs found a leak.
The revised flight envelope had already been put in place at that time and the aircraft will have been operated within those limits. Prior to that time, the main flying exercise being taught that exceeded Bell's recommended pitch & roll flight envelope was wingovers which was removed from the Griffin syllabus as soon as the new operating limits were known.
The revised flight envelope had already been put in place at that time and the aircraft will have been operated within those limits. Prior to that time, the main flying exercise being taught that exceeded Bell's recommended pitch & roll flight envelope was wingovers which was removed from the Griffin syllabus as soon as the new operating limits were known.
Crab, SA, and Wiz make an excellent point: the fatigue spectrum is composed not simply of the specific maneuvers, but how many times they are accomplished, and at what weight. Best example I can think of on the weight side of things is what happened to the original S-64 Skycrane when it went into the logging business, compared to the original load spectrum within the military usage. ( and yes, that flight operation also changed the maneuver spectrum spread in that, for example, they would spend a lot more time coming down a mountain side on the edge of translational lift with high n/rev vibes ).
There is a recommendation to find out where the parts have got to, which as pretty much any 412 serviced by Bristow could have received a MRG SC that had been used at DHFS seems like a good idea.
But if Bell were really concerned, they could at least have insisted on removal and NDT of the SCs in question - rather than waiting for cracks to propagate - seems to me that they weren't that worried about wingovers causing the problem.
The sloping ground landings, on the other hand, are far more likely to have been a causal factor since the bending stresses on all the MRGB components are obvious and with student mishandling, likely to exceed design tolerances far more easily and far more often.
The sloping ground landings, on the other hand, are far more likely to have been a causal factor since the bending stresses on all the MRGB components are obvious and with student mishandling, likely to exceed design tolerances far more easily and far more often.
My interpretation of the use of the term “ un-lifed “ means that the measured stress from the flight loads survey flight test was under the “ endurance “ level, i.e. possessed infinite fatigue life when flown in that set of conditions/maneuvers/weights. There are some implications here. Perhaps I’m wrong re that verbage?
If memory serves, when Harry Jensen and his group at SA first arrived at the methods/test requirements etc associated with establishing the Safe Life concept in the helicopter business, there was a group at Bell doing similar work. That being true, I’d assume they’d be quite interested and able in following up on this situation.
If memory serves, when Harry Jensen and his group at SA first arrived at the methods/test requirements etc associated with establishing the Safe Life concept in the helicopter business, there was a group at Bell doing similar work. That being true, I’d assume they’d be quite interested and able in following up on this situation.
My understanding from reading the report is that due to it's un-lifed nature the part wasn't tracked so no one can actually answer that question, or indeed where other ones from the RAF fleet may have got to.
Even with "Tracked" Parts it gets tedious over time to be able to start back tracking to the starting point.....rather than having the starting point at first fit when new and then follow the item as it is passed down.
When you conjure up the difficulty that entails when the tracking is an after thought.....no telling where those parts went to over the years.
All that aside, the choice of B412 in a training role - particularly for students straight off initial helicopter course - does seem a little odd to me.
The DHFS single squirrel to 412 training regime replaced the RAFs Gazelle to Wessex training pipeline (which again had worked very well for many years) the new variant, MFTS with 135 all through and a smattering of 145 at the end, doesn't seem to be faring quite so well.
I was involved in the selection process for the twins for DHFS and we were limited to those types proposed by the various companies tendering for the task. In addition to the roles Crab mentioned, the requirement was also for navigator training in a centre seat. That precluded the BK 117 where the control runs were through a large 'box' from floor to roof between the pilot seats. The other types were MD 900, AS 365 and AB 109. The 412 was the winner by quite a clear margin, the others either lacking cabin room or had wheels considered too small for soft ground running landings. Was fun flying all those types for a week though!