What do you mean by "inherently safer"? If the t/r drive was faulty (if that is what caused this, hopefully initial findings will soon be made public) the accident might have occurred at a slightly different time but would possibly have put the aircraft down in a less fortunate place for those on the ground. Helicopters are designed to operate vertically, btw! The departure flown appears to have followed a certified Category A / Class 1 profile so it should have been as safe as any other.

Does anyone have a schematic of the tail rotor driveshaft and gearbox assemblies?

Presumably he means that had the climb out been more forwards, gaining airspeed, translational lift and a headwind asap there would be less stress on the TR and for a shorter exposure time...

The 169 has a winching capability. That punishes the tail rotor far more than a Cat A departure.

Chopjock.

You'll never change will you? After years of posting on rotorheads, listening to the advice of others - you still talk complete and utter bo**ox, don't you?

TC

Sorry Chopjock is correct, if you actually care to read the post Chop was referring to you will find Chop's answer is strictly correct. Unless you would prefer to be at 400 ft with no forward airspeed when the Tr assy takes a holiday. Personally I would take lower and probably doing around 60 to 80 kts ( that he would have arrived at in the time to go vertical to 400 ft.) At least your stabilisers would be doing something.

A question for you Legal Scholars posing as Helicopter Pilots.....the British way of doing a Confined Area Takeoff (I learned it as a Towering Takeoff) differed from the American way of doing the same thing (each used the same power) is far different from the various CAT A, Perf Class One (or whatever you are calling things this week).

Instead of this backwards and up to 400 feet (or so) as we saw used.....what if an old fashioned Towering Take Off had been used from as far downwind as possible and the aircraft accelerate much lower but clear of obstacles.....could Vtoss and Vbroc been achieved much quicker?

What Rules, Regulations, etc.....prohibit such a Takeoff like that a situation as is under discussion?

Are Rules getting ahead of reality and causing greater risk instead of making flying safer?

Except for the 109 and 119, which push

I must admit that during my time with Army flying, I was always a little puzzled watching civil helicopters performing all sorts of convoluted and painfully slow departures when we just took off into wind and transitioned as quickly as possible, then along the years we started to introduce committed calls at various airspeed and heights in twins. Leaving the military and starting police and corporate flying introduced a whole section of the flight manual to be observed depending on aircraft weight, helipad size, obstructions,....etc. Explaining to passengers why I was not just flying forward became part of the pre take of drills at one particular base, just to head off the inevitable question halfway up to TDP!

SASless, it is a cart/horse question on regulation/performance profiles and which comes first. There are lots of risks and hazards in helicopter flying only some of which are addressed by regulation. And those tend to be the quantifiable ones. Easiest is the airline model where the worst that can happen is an engine failure, and so that is then applied to helicopter and the regulators come up with different standards, exposures, etc. Some, like EASA, have more focus on compliance to OEM flight test certification procedures than others. In our Wild West view of confined, the greatest risk is hitting something, in the EASA view or PC1, it is the first engine failing (the second one never fails). So the certification authorities go back to the manufacturers and say "give us the numbers and performance charts, and publish them in the RFM". Now over to sales where performance sells, so the manufacturer uses their test pilots to develop OEM recommended procedures to maximize performance and payload, regardless of the real-world additional risks introduced. Two examples: the back up profile in a true "confined" area where you might actually hit something; some of the PC1 runway takeoffs where the TDP is an altitude instead of an airspeed. When I first flew S76, the PC1 takeoff profile was like a "cobra" maneuver, accelerate to a certain speed, balloon up and level, accelerate some more and then climb - just the thing not to do on a black night in monsoon rain with a new national copilot.
Anyway, a horse beat to death, and there are many on this forum (such as JimL) that can explain it much more clearly than I can. Needless to say, in todays world nobody will risk any SOP other than the OEM provided one, to the point that even where there are obvious flaws operationally, like the original AW139 offshore helideck with the too rapid climb through 20', we will fly a far riskier profile until the OEM can come up with a published revised profile. And yes, in the past we had free rein to make those up and apply them ourselves.

good point bosbefok - I was just thinking of the 139, 169 and 189 and forgot about the 109 and 119:ok:

Hmm, I'm not sure I quite understand what exactly is b*****ks with @Chopjocks remark? Reducing the time spent at zero forward speed will reduce the time spent in very unhelpful conditions when encountering a TR drive failure. Any forward speed will unload the TR, thereby reducing torque effect and will additionally increase effectiveness of the fin. At >50kts there is a reasonable fighting chance in case of a TR drive failure. At zero kts not so much.

And maybe not?

In the current designs with very small vertical surfaces be aware they virtually have no fin or it is very weak in effect -

Why is anyone quizzing the CAT A departure? In commercial ops it is a requirement not an option. So debating whether a takeoff profile other than this, is better - is a load of Bo**ox.

The pilot initiated a standard departure for the size of the site.

The probable causes now remain:
Part of the TR assembly failed and departed flight.
Something struck the tail area causing a catastrophic failure.

Once an aircraft enters a developed TR failure flight path (rotating) NOTHING the pilot does to recover (with the cyclic) will resolve the issue simply because the pitch/roll datums continuously change [as described earlier very succinctly].
The suggestion that the pilot fought to steer clear of people or property is wishful thinking At this stage in the flight, the pilot(s) became a passenger.

It's actually pretty rare to ground all examples of a type without some pretty solid evidence there have been multiple failures in the same mode across at least two incidents. The wreckage only departed the scene yesterday and the FDR could (par example) indicate TR performance loss without an immediate and obvious cause without further forensics.

Tc
I'm questioning it because it didn't work very well here did it? Cat A PC1 is so focused on one of two engines failing it completely disregards the extra exposure to the one and only tail rotor.

I’ve just picked on this individual post because it sort of illustrates my point; absolutely no criticism of it or the poster is intended.

Is it a particular helicopter thing to demand groundings the moment something happens?

On Monday a 737 crashed into the sea killing everyone on board, but I’ve yet to see any calls for 737s to be grounded.

In 2014 a 777 vanished without trace in the Indian Ocean, but I saw no calls for the 777s to be grounded, or questions about lack of emergency ADs/ASBs?

Three weeks after the 2016 EC225 crash in Norway, an Egyptian A320 crashed into the Med, with total loss of life. The cause is (AFAIK) still not known, yet our oil workers were happy to fly to Aberdeen on an Airbus A320 the next day before refusing to fly on an Airbus EC225.

What is it with helicopters that we have to react this way when our FW cousins do not?

Shake your Magic Eight Ball one more time and decide which it was so we can pass that news along to the AAIB so they can move on to other accidents.

Zero accident deaths ... last year
 

https://www.reuters.com/article/us-a...-idUSKBN1EQ17L

"2017 safest year on record for commercial passenger air travel
Airlines recorded zero accident deaths in commercial passenger jets last year,"

Probably carried more people in the first hour of 2017 than the entire global helicopter industry in the whole year. Someone might be able to work it out properly.

Helicopters are not as safe.

The aforementioned helicopter passengers seem to be behaving quite rationally.

Jet airliners and operations have proven themselves safe. Helicopters - still some way to go it seems.

Yes, not stuck pedal. Stuck pedal never causes you to fall out of the sky.

At the risk of annoyance, a number of eyewitnesses and other videos appear to be indicating that the departure was not typical (standard?) for that site. Legal, within regulations, etc, etc, but possibly not normal. For the lack of any other evidence I still wonder if there might have been something about the height of the departure that offers a clue to what subsequently went wrong.

Statistically, is it in fact more or less just as probable that other causes remain to be considered - however apparently unlikely - i.e. pilot incapacity, sabotage, etc?

Yep, I reckon. Countless times trying to get out of a tight spot in the boonies, back it up as far as you can go, get some airspeed whilst still in ground effect and then zoom climb it out at best angle. Many of those you'd never get out vertically, you just run out of puff before finding clear air above the trees.

Yep, I'm wondering the same thing, why so high? Doing rejected elevated heliport night takeoffs in a S76 from 60' CDP is a pretty harrowing experience on the way down. I'd be uncomfortable being needlessly exposed any higher without airspeed.

With the scant information available to the public at this point....Commonsense alone indicates considering all possible causes to be the bett4er course.

Watching video's taken from several perspectives does tend to point one's interest in one direction but absent more definitive information pointing a finger at a cause at this time is pure speculation.

I agree with you totally, the vertical profile in the S76 is and aggressive manouvre from the start, and several aircraft have been damaged practising the reject. In fact the RFM actually states that you should go light in the seat when you drop the collective.

The back up profile as used in this case, and on most AirBus helicopters actually is quite gentle. You have power in hand (it should never need full power until you rotate into forward flight), keep the take-off point in view all the time and the reject is a reduction in collective to contain the power (not slamming it down) drop the nose around 8 degrees and the aircraft flies back to the take-off point slowly and under full control, over the pad use collective to cushion the touch down. Like a few of the posters on this thread I use that technique most working days, I trust it, and practise rejects every six months. I never liked the S76 vertical due to the application of full power when on the ground, the loss of site picture and aggressive reject.

Give me what Eric did every time. The back up technique also guarantees obstacle clearance in the event of an engine failure after TDP.

And for those who doubt a goose could down a helicopter, how about the Blackhawk in January 2014 in Cley, Norfolk, UK, But I really don't believe either geeese, mute swans or anything else at the moment.

SND

Posted on another thread but probably best here.

Engines should meet a reliability figure of 1 x 10**-5; in ICAO parlance, this qualifies them as very reliable (the reason for the low standard is that a failure, at worst, should only result in an outcome of 'Major' - i.e. 'physical distress including injuries).

Tail-rotors should meet a reliability figure of 1 x 10**-9 because a failure could result in an outcome of 'Hazardous' or 'Catastrophic' - i.e. a fatality or multiple fatalities.

Reliability targets for tail-rotors are therefore 4 orders of magnitude better than engines - i.e. 10,000.

(A probability does not mean that a failure will occur after the reliability number has been reached, it can occur at any time but it should only occur once in the period.)

A helicopter certificated in Category A can depart or arrive utilising Category A procedures where failure of an engine should not result in damage.

A single-engine helicopter can depart or arrive using a Category B procedure where failure of the engine should not result in damage. It does this by accelerating below the HV avoid curve until it achieves a climb speed clear of the 'knee' of the HV curve.

Any departure other than that published in the Flight Manual - for either a Category A or Category B helicopter - could, following an engine-failure, result in a 'Hazardous' or 'Catastrophic' outcome (with a probability for a single of 1 x 10**-5, or for a twin or 2 x 10**-5).

An engine-failure in the cruise for a twin will be a non-event. An engine-failure in the cruise for a single might result in an outcome of 'Major' (as above) unless it is being flown over a hostile environment in which case the outcome might be 'Hazardous' or 'Catastrophic'.

In the recent accident, the profile flown was the AW169 Category A variable TDP procedure. Whatever caused the accident was not the result of having flown this procedure. It was within the defined and certified operational envelope.

JimL

Absolutely right. I have been involved in a number of accident investigations and on more than one occasion was pressurised to identify/speculate on the cause before before even starting the investigation.

The maxim is keep your mouth shut and your eyes wide open and let the investigation unravel the cause and effect.
This is particularly important when there is loss of life.

Is max power not limited by automatic switching to an OEI mode as with the 139? Lowing the collective in a 139 reject is to check the climb and intiate descent, and need not be (often should not be) a big reduction.

Roger that. S76 legacy habits applied to a light 139 rig departure using max available power are quite a ride. Hard to disaude the hard-wired or TDP concept averse.

S76 also lost to birds in the US a few years back. But also sceptical in this case.

[QUOTE=Torquetalk;10301362]Is max power not limited by automatic switching to an OEI mode as with the 139? Lowing the collective in a 139 reject is to check the climb and intiate descent, and need not be (often should not be) a big reduction.

I don't know on the 169, I've only got as far as looking at it for a prospective purchaser, but the reject should only need a check down. I don't know how the 169 protections work, but what you state is logical. I do think that the thinking from the colonies is that a Class 1back-up is either complex or tough on the aircraft. It just isn't. In fact the easiest part of it is that apart from a look to make sure you're inside SSE, and the thing isn't on fire, the whole reject is flown on the edge of the translational burble, giving fantastic references for speed being right, allowing eyes out to touch down, and that is the same on every aircraft I've flown with such a profile apart from the S76.

SND

I completely understand that the procedure was 'within the defined and certified operational envelope' - my question was whether or not it was 'normal' in terms of how others had observed this and similar aircraft taking off from this location in similar circumstances before. Equally, I didn't mean to suggest that - even if the procedure was 'abnormal' in those terms, it was the cause of the accident.
I was really wondering if there could have been a perceived anomaly in the performance/response or any other aspect of the aircraft (that we can't see) that might have lead to the pilot wanting to gain more height that 'normal' and that, if so, whether this might give any clues as to what subsequently caused the apparent catastrophic failure (that we can see).

I reckon that harks back to the days of 12E Hillers - you could rig them one way or the other - enough left pedal or right pedal but not both.

TDP - is just that, a "decision point", before it you come back down after it you can fly away and achieve the MINIMUM clearance to obstacles. If you continue climbing about the only thing that changes is the obstacle clearance gets larger.

So what?

seen this technique advocated by the Aussie mil but it leaves you very poorly placed in the event of an engine failure since you are travelling too fast to stop before you rotate and have nowhere to go once you have rotated

Cables near statium
 

There are 100 foot towers with cables to the north and east of the stadium. the stadium is in blue, centre background.
Would this influence departure planning?

According to Google Earth's radar the stadium flat roof is 19m above the pitch.

https://goo.gl/maps/ZLNQyosngDu

https://cimg4.ibsrv.net/gimg/pprune....ab70f8dfcc.png

Leicester City Football ground - in blue.