and this is the great dilemma isn't it? The pressure on EC to find a workable solution based on real science is immense. We can fly the 225 like a L/L2 with no Emerg Lube but whether this will be acceptable to all, who knows. The Sea King that is being replaced with new technology has had it for about 20 years...

I think that if one reads the message not as "EMLube failure -Ditch" , but
"EMLuBe Fail(ed to fix the problem) - Ditch"

then in fact it is working properly, If I were writing the software, I might well decide to not have a host of different error messages when the conclusion is the same.

Just out of interest - how many Aberdeen aircraft does this affect (all 3 operators)?

As it stands, that message from the StepChange website is out of date. If I understand the effect of the CAA Operational Directive, it will prevent the use of any UK-Reg Pumas and variants offshore, if they have the relevant part number shaft.

The "Step Change" party line is really just the view of the offshore installation operators. It is clear they wanted Puma shuttles to resume with limited restrictions. I wonder whether this will change, in the light of the CAA action?

Is relying on HUMS acceptable?

CAP 753 (8.3) states that HUMS must detect no less than 70% of failure modes that it is directly monitoring. The oil pump shaft is not directly monitored so presumably the rate of detection may be less than 70%.

At what percentage do you say the risk is mitigated and it's OK to fly?

Can EC or an operator demonstrate 225 HUMS will always give an early warning of impending failure?

FYI, the Fact Sheet (the second link) includes a reference to the CAA Directive:

Why is the EC225 still suspended?
The helicopter operators took the decision to continue to suspend the EC225 until further guarantees can be provided on its safety. Independent of this, the UK aviation regulator, the Civil Aviation Authority (CAA) has since issued an operational directive forbidding its use for offshore transport. This continued suspension of the EC225 is fully supported by the Helicopter Safety Steering Group and the trade unions.

Exactly the point Sanus. You have answered the question yourself.

This failure of the defective part is known and at the moment has an apparent return period of 6 months in the UK fleet. Apparently the HUMS has only a relatively small chance of preventive detection, so the frequency of further undetected failures is pretty significant if the affected aircraft continue to fly.

Its only a satisfactory resolution, if you are happy with a reasonable prospect of North Sea "controlled" ditching, in the winter months.

We have been very lucky so far, that the outcomes have not involved injury or worse. What is the conditional probability of benign conditions in a North Sea winter? It gives the expression "wing and a prayer" new resonance.

B73 - thanks for pointing me at the second link. However, is it not less to do with the aircraft type/variant but more with the gearbox shaft batch part number/method of manufacture?

From the HSSG 'Fact Sheet':

The return to flying will see an additional one AS332L1 and eight AS332L2 aircraft amongst the three Aberdeen-based operators.





So, in essence, the CAA directive effects all but 9 Super Pumas in ABZ.

I wonder what the time scale is for going back to original design shafts on the L and L2 models. I also wonder if it is possible to rework the existing new design shafts which are in service now or will EC have to start from scratch. I assume it takes a long time to make a shaft due to the manufacturing, chemical treatment and ageing processes involved so the North Sea (and other areas) is probably in for a lengthy disruption.

The loss of a significant proportion of O & G helicopter support worldwide is bound to cause serious concern at the highest levels of the oil companies management and governments.

To think all those S-61's that got flogged off for junk prices!:(

It is indeed. And the next section of the 'Fact Sheet' addresses that very point. (Bear in mind the target audience (ie the passengers) so the serial and part numbers themselves are not mentioned). Also, PPRuNE/vbulletin doesn't want to accept the original tabular formatting so I've had to re-jig it slightly:

Why are some Super Pumas flying and others not?
The difference is down to a certain type of component – the main gearbox vertical shaft. For ease, these have been labelled below as shafts 1 and 2.

Type of shaft.......Can be fitted in.......What is it?.........Approved for use?

“Shaft 1”......L, L1 and L2 models........This is the original design of shaft. Has accumulated 4.5 million flight hours without incident......Yes

“Shaft 2”...... L, L1, L2 and EC225 L, L1 and L2 aircraft can be fitter with either Shaft 1 or Shaft 2 If not already so, these will now be re-fitted with shaft 1 in order to be fly again. All EC225s feature shaft 2 and cannot be fitted with Shaft 1........... A change in the manufacturing process of specific batches of Shaft 2 was originally thought to be the cause of the G-REDW ditching in May. New evidence is coming to light which suggests that the scope of the problems associated with Shaft 2 are wider. Use of aircraft which feature this shaft is not supported by the aircraft operators and is also no currently permitted by the CAA.

I thought the EC225 fleet leader has nearly 40K hours accumulated?

40,000 hours???? It was only certified in 2004 so that would mean the aircraft flying something in the order of 13 hours a day, every day, for the last 8 years.

First introduction a little bit less than 8 years ago so the answer is : no

G-TIGC, a 332L from Bristow for sale (up to now...) is 30 years old with about 34000 Hrs TT.
.

Not far shy of 10,000 hrs on one NS 225 that I know of

As of December 2011 there were two aircraft with 9K hours, so current EC225 fleet leader is likely to be at ~10K.

I/C

I'm just using Eurocopters own data:-

Puma helicopter, super puma - Eurocopter helicopters - Eurocopter, an EADS company

which says:-

The EC225 has evolved from the vast experience accumulated by some 100 Super Puma operators; some 900 helicopters have been ordered in 52 countries. The in-service Super Puma fleet has logged more than 4,4-million hours and the fleet leader has flown 39,300 hours.

One assumes therefore that they are now being clever with the mix and match of types.

Not really, to be fair. The 'in-service Super Puma fleet' includes all the various variants of the AS332 and the EC225. (The EC225 is, in essence, an AS332 L3).

ha yes but Bravo I think we are seeing that some Super Puma's are more Super than others...

One truely wonders how that approach was used in the approval process. Over simplification no doubt but do you just take AS332L2 then say you've ran the new gearbox on a rig for X hours and therefore we are good to go with the EC225?

The focus on the emergency gearbox cooling system is all well and good but remember thats just the short term fix if you have one type of in flight issue. As has been said before when parts of the gearbox are departing through the fuselage a cooling system isn't going to save you.

The only real solution short term is limit the torque of the 225 to protect the gearbox that it has and for the manufacturer to give a strict limits on checks. Although one might note that in the case of REDL the suggestion was that existing detection methods wouldn't have provided further indication of issues.

Now I know the failures are different but with no explaination why a 3000hr gearbox shat itself which was lifed to 6000hrs and with 2 further gearbox issues in 2012 I think an engineering solution is needed not just a software update and the responsibility dumped on the operator or worse maintenance for the operator. Would you want that on your conscious?

People often say this when there is a problem with a gearbox - reduce its load and it will be OK, however in this case, since the failure occurs between the bevel gear and the oil pumps, I am not sure how reducing torque would affect anything, since the torque on the bit of the shaft that is failing would remain the same (just driving the oil pumps). I suppose there could be some reduction in bending caused by less torque, but I think you would need to be a transmission expert to understand if this were the case (which I am not!).