Performance class two enhanced (offshore)

[manfromuncle]

I understand the rules are changing regarding this? For European offshore operations

I understand this will have a major impact in the Southern North Sea.

Can anyone point me in the direction of the details?

[Deutz]

I’m not sure that you mean performance class two‘enhanced’. PC2(e) was a term which meant PC2 with exposure period during which a safe forced landing is not possible.

There is a good explanation of the concept in a closed JAA NPA. Try googling ‘JAA NPA OPS 38’. This has been lifted by EASA and is included in EASA NPA 2009-2B, for which a comment response document following the first round of consultation is awaited.

[212man]

Deutz,
PC2e most certainly does not mean "with exposure period", in fact quite the opposite! The NPA you refer to was incorporated in JAR OPS-3 Amdt 5, and if you re-read it you will see that in essence what PC2e tries to achieve is a quasi - PC1, whilst recognising that a full PC1 guarantee is not possible in the offshore environment.

I'm sure JimL can give you chapter and verse on the subject, should he feel fit.

[HeliComparator]

Just to be awkward, I would say that PC2E is performance class 2 with exposure time, where that exposure time is nominally zero. Which as 212man points out, is certainly not PC1.

The question is, is the probability of having an engine failure and ditching during the typical 4 seconds or so of exposure time when flying PC2, greater or less than the probability of having some other problem resulting from having to operate with minimum fuel to satisfy PC2E, such as:

Getting short of fuel because the TAF for your Coastal Airfield was way out (its fogged in) and you don't have enough fuel for an alternate, so you have no choice but to fly the approach anyway even though the RVR is 100m. Or something similar!

And what about the effect on overall safety by having to fly more sectors, because the payload for each sector is less due to PC2E constraints?

And what about some of the PC2E profiles the manufacturers have come up with - eg you must keep 40kts IAS on til the last moment, then big nose up attitude to stop in time, hopefully not hitting the structure in the process when you can't really see where you are going due to the nose up.

When did the last accident occur from an engine failure just on takeoff or landing? By contrast, how many aircraft have hit the structure due to misjudgment, or become dangerously short of fuel?

These are the sorts of reasons why some of the operators, and UK CAA, are rather against PC2E. Yes, when the other option was PC1 (impossible offshore) it was a good idea. Now EU Ops is all up for grabs, we think that the status quo is best - ie PC2 with controlled exposure time and the equipment (UMS etc) to retain confidence in engine reliability.

HC

[212man]

JimL can give you chapter and verse on the subject, should he feel fit.

.....and HC will read you the other chapters and verses!

[JimL]

Manfromuncle,

The rules were changed at AL5.

The effect on the SNS will depend on the equipment used; for the AW139 there will be no effect at all.

The effect on all NS operations will depend upon the operator's application of the rules. Take-off and landing in Subpart H (PC2) was always divided between: (a) the original ICAO principle of a safe-forced-landing (Pure PC); and (b) the use of Exposure. This did not change with AL5.

Examination of the revised JAR-OPS 3 will show that (both for take-off and landing):
Clause (a)(1) of the rule requires the base-line performance (second segment climb);

Clause (a)(2) is for operations other than with Exposure (with a SFL - i.e. Pure PC2); and

Clause (a)(3) is for operation with Exposure

The operator has the opportunity for application of either Pure PC2 or Enhanced PC2 (PC2e).

PC2e comes within (a)(3) because it is well known that (described in the guidance - as it was in the explanatory material for the NPA) environmental conditions of helideck operations do not always permit a deterministic outcome as prescribed in the Category A procedure. This is one of the reasons why operations cannot be in PC1 (another is the required size of the helideck surface (the TLOF)).

Application of Pure PC2 requires a safe-forced-landing - in the case of helideck operations that implies: (a) no deck-edge strike; and (b) a landing without injury to persons in the helicopter (a safe ditching). It has long been recognised that such a safe landing can be conducted in Sea State 4 and below (from AC 29-2C, significant wave height of 4ft - 8ft and wind between 17kts and 21kts).

Provided that a safe-forced-landing can be achieved, Pure PC2 can be conducted.

Helidecks have to be designed to provide a 180 obstacle free sector - oriented into the prevailing wind. Leaving aside the case of a sea that is running high with a slack wind (which is an issue that does has to be addressed) it follows that with a reported wind of 21kts or less, a departure or arrival will always be possible within the 180 obstacle free sector regardless of wind direction. If, for take-off, that is combined with a profile that assures deck-edge clearance, the conditions for Pure PC2 are satisfied. As wind accountability is never built in to the manufacturers procedures other than for drop down, a cross wind has no effect on deck-edge clearance.

Compare that with the pre-AL5 conditions and you can see that (for winds of 21kts or below) the only additional requirement is the provision of a profile that provides deck-edge clearance. (This does not take cognisance of the provisions that have already been made for low wind operations discussed in the other thread.)

The use of Pure PC2 is tied to a wind speed of 21kts or less (with the rider about significant wave height); this break is hard - i.e. not factored. If that wind is exceeded, then a safe-forced-landing is not assured and the operator has to apply the conditions of the provisions of (a)(3). If the break is hard, it can logically be argued that progression into PC2e should permit full credit for the first 21kts of the wind. Whilst this could not be permitted for a Category A procedure, it can for PC2e because of the flexibility of the provision:
"take-off mass takes into account: the procedure; deck-edge miss; and drop down appropriate to the height of the helideck..."
The situation with institutionalised ditching (albeit tied to a limit of SS4) provides an ethical dilemma for the oil companies; the acceptance of this situation is for them to deal with because it is one of duty of care. Before extensively flaming me for accepting this situation, please examine the status quo - operations with Exposure which encompass both the probability of a deck-edge strike and ditching in an undefined sea state.

In order not to provide a dense post, I will pause at this stage and let you consider what has been said.

I will resume later with: the provision of performance data based upon manufacturers graphs; the situation when the wind is in excess of 21kts and in the 150 limited obstacle sector; addressing the lack of (explicit) data for the HAPS landing manoeuvre by utilising manufacturer's statements and graphs; and examination of the 'proportion' of operations that may have to be conducted with an exposure element.

Hopefully, by the time the entirety of this has been discussed, you will see that most of HCs apocalyptic predictions are not based upon fact.

Jim

[JimL]

Firstly to the take-off masses:

Some mass figures which relate to the observations in the post above (addressing Pure PC2 and PC2e).

Using the manufacturer's data for, the AW139, the EC225 (included for HC's benefit), the EC155 and the S76C++.

Taking ISA SL conditions the following masses are provided by the graphs:

For the AW139:

PC2e - there is no drop-down with a mass of 6,400kg in nil wind up to ISA + 20

For the EC225:

The Pure PC2 mass is 10,875kg

The PC2e mass with an unfactored wind of 20kts is:

10,500kg for a 50ft drop down; and

11,000kg for a 100ft drop down (limited by the deck-edge mass of 10,875kg)

Zero drop down is achieved with an unfactored wind of about 35kts (extrapolated)

For the EC155:

The Pure PC2 mass is 4,750kg

The PC2e mass with an unfactored wind of 20kts is:

4,920kg for a 30 ft drop down (limited to 4,750kg)

Zero drop down is achieved with an unfactored wind of 27kts

For the S-92:

The Pure PC2 mass is 26,250lbs

The PC2e mass with an unfactored wind of 20kts is:

26,500lbs for a 50ft drop down

Zero drop down is achieved with an unfactored wind of 30kts

For the S=76C++:

The Pure PC2 mass is 11,500lbs (wind up to 10kts)

The PC2e mass with an unfactored wind of 20kts is:

11,700lbs with a drop down of 15ft

Zero drop down is achieved at 11,700lbs with 23kts of wind (extrapolated)

NB 'Zero drop down' is no drop down below deck level.

Jim

[JimL]

To continue to the landing manoeuvre.

HC is absolutely correct when he points to the inappropriateness of some of the Helideck CAT A landing procedures. We can speculate that this was as a result of a decision to replicate the onshore helipad procedures. The onshore procedure provides a straight in continuous approach through the LDP to the landing point. (Previous versions of the guidance material also had a clause to include a landing after a failure at any point on the approach path - in later versions this is removed.) The LDP is the last point from which a balked landing can be carried out.

When providing procedures for a ground level helipad, a straight in approach with an LDP of about 40kts is reasonable because the (peripheral) cueing environment is sufficient to allow the positioning of the helicopter to the correct touchdown spot and it maximises the landing mass. For straight in offshore approaches there may be few peripheral cues and even those in front of the helicopter disappear from view when in a decelerative manoeuvre close to the helideck (one of the reasons for tail-rotor strikes).

It was for this reason that the HAPS landing profile was defined; with the HAPS profile, the Committal Point (CP) represents the last point from where a OEI SFL/balked landing can be carried out and the first point where a OEI sidestep landing can be safely performed (meeting the requirement for a SFL). It is recommended that the Dynamic CP is set to a point where: the helicopter blades are clear of the deck; the handling pilot has the deck at 2 or 10-O-clock; and with a closing speed of 10kts. If there are obstructions, the Offset CP can be used; this is at the side of the deck (not necessarily in the hover).

Manufacturers have been extremely reluctant to provide profiles using an LDP as defined for the Dynamic CP. We can only speculate that this is because the landing masses for a balked landing with nil wind will result in a large drop down. This HAPS manoeuvre with a CP was modelled some years ago and established that an engine failure one second before the CP resulted in a drop down slightly less than that experienced for the HAPS take-off manoeuvre in similar winds. (This is intuitive for those who have flown extensively on the North Sea using the HAPS landing profiles.) Using the Dynamic CP also reduces the drop down because there is always a residual speed of 10kts.

Up to recently it has been difficult to establish the drop down in the absence of appropriate landing profiles. However, in a recent manufacturer's publication, it was stated that drop down can be established from the take-off graph by using the actual mass and speed of the helicopter as an equivalent of unfactored wind.

As provided in the regulations quoted before, actions following an engine failure at or before the CP can be either: continue OEI and perform a SFL on the surface; or perform a OEI balked landing. Actions at or after the CP are to continue and perform a SFL on the helideck. Applying the regulations to the landing mass and using the methodology provided above and manufacturer's data, we have the following.

Taking ISA SL conditions (and the residual 10kts A/S) and applying a hard limit of 20kts unfactored.

The following masses are provided by the graphs for a Dynamic CP (for an Offset CP, the landing mass would be the same as the take-off mass):

For the AW139:

PC2e - there is no drop-down with a mass of 6,400kg in nil wind up to ISA + 20

For the EC225:

The Pure PC2 mass is 10,875kg (from the WAT graph)

The PC2e mass with an unfactored wind of 20kts is:

11,000kg for a 50ft drop down (limited to 10,875kg)

Zero drop down is achieved with an unfactored wind of about 25kts (extrapolated)

For the EC155:

The Pure PC2 mass is 4,750kg

PC2e zero drop down is achieved with an unfactored wind of 17kts

For the S-92:

The Pure PC2 mass is 26,500lbs

The PC2e mass with an unfactored wind of 20kts is:

26,500lbs for zero drop down

Zero drop down is achieved with an unfactored wind of 20kts

For the S=76C++:

The Pure PC2 mass is 11,500lbs (wind up to 10kts)

PC2e zero drop down is achieved at 11,700lbs with 13kts of wind (extrapolated)

NB 'Zero drop down' is no drop down below deck level.

The implication of the zero drop down is that the arrival sector widens to the 210 degrees of the limited obstacle sector (where all obstacles have to be below the level of the deck).

[HeliComparator]

Blimey JimL, you are on a roll!

Just picking up on your "apocalyptic" comment at the end of your first post, neither the introduction of PC2e, nor the non-introduction of PC2e would be apocalyptic. However I suggest that there is little point in changing established procedure and introducing additional complexity unless a clear safety benefit can be identified.

Both the probability of an engine failure on takeoff or landing causing a crash/ditch without PC2e, and the probability of one of my "apocalyptic scenarios" occuring with PC2e, are very slight. However it has to be said that the former has never occured in the history of the N Sea, whereas the latter has occurred from time to time, in at least 1 case with fatal consequences.

So which ever path is finally taken, there will be little effect on overall safety. My point is why make a change for change's sake when the previous sentence is true? And without any proper analysis so far, it might well turn out that in fact the introduction of PC2e reduces overall safety.

But this argument is probably unanswerable with current information.

So how about:

If PC2e relies on accurate offshore wind data for performance calculations, will all offshore installations have to have approved wind measurement equipment/locations? (currently they are not approved as far as I am aware).

If I am shuttling and have arranged my fuel / arrival and departure weights to be within PC2e limits for the current offshore reported wind and client load, but whilst I am on deck for the normal 15 mins or so, the wind drops a bit so now I am over weight, what should I do? Bump passengers?

If I have that (admittedly never yet experienced) engine failure on rotation and clip the tail on the deck edge, spin into the water and kill someone, and its discovered in the investigation that I rotated 0.5 seconds (4ft) too early compared to the profile used to calculate deck edge clearance, will I go to prison?

HC

[JimL]

Hi HC,

As you know from our previous discussions, there is nothing new in my posts I am merely using data that is currently available, and restating other facts.

All aircraft use the existing wind measuring equipment to apply the limitations contained in the HLL. Will that change? Probably not. Even at this time JAR-OPS, permits the operator to take advantage of an improved wind factor - surely that is an incentive to improve this equipment. In order to strengthen your argument, you have a tendency to make assumptions that were not part of any proposal. Why was it do you think that the authors went to such trouble to emphasize the difficult nature of the offshore environment? Your whole argument depends upon something that you state you wish to avoid - confusion between PC1 (and the Category A procedure) and PC2e.

As you will have seen from the mass caculations, your previous statement about the knock-on effect on passenger loads was something of an exaggeration. With regard to a change of wind, such conditions already apply; what would you do now if you were operating an EC155 and the wind dropped from 10kts+ to 5kts? Would you apply the 300kg reduction in payload?

You should already know the answer to your final question because it is specifically mentioned in the ACJ; after discussion of a number of issues which affect the profile, it states:

"Under these circumstances, the Commander might adjust the profile to address a hazard more serious, or more likely, than that presented by an engine failure"

A number of your scenarios link the application of PC2 with other issues - one of which was fuel calculations. The calculation of fuel is completely independent of performance, it should be based upon safety, the company SOPs, and be compliant with the requirements - one of which is the ability of the Commander to add fuel for contingencies. This calculation comes before any load is offered to the customer. In any case, the masses shown above should not create a seismic shift in fuel policy (unless it is not currently based upon calculation but on a fill-it-up mentality).

Perhaps I sense a change in tone; we are now discussing the implementation of the rule and not non-compliance.

I find your statement:Now EU Ops is all up for grabs somewhat frivolous and naive. No changes were proposed (in performance) from JAR-OPS; I am also reliably informed that there were no objections to the AL5 changes in the comments to the NPA for offshore operations.

Perhaps the oil companies need to examine the facts with regard to compliance and performance and not be swayed by emotive arguments that cannot be substantiated. What price ALARP - are we confusing practical with convenient?

More later but consider this; if Pure PC2 (as described in my previous post) is employed, it will remove the probability of deck-edge strike from about 70% of offshore movements (take-off and landings). With a wind in the 180 sector, PC2e will remove the probability of a deck-edge strike and ditching in high sea states. How do they rate as safety benefits?

Stop just thinking EC225 and consider all helicopters.

Jim

[JimL]

Here is an attempt to quantify the benefit of the extant regulation with respect to the reduction in Exposure; in order to do this it is necessary to establish those operations which are potentially:

without exposure; and

where exposure might remain.

Firstly we need a reasonable basis for assessment. During the modelling of PC2e, access was provided to an operator’s database of weather reports (INTOPS).

INTOPS provided us with 39,131 North Sea wind data points (reports) for a four year period. Using this data we established that:

Wind <= 20kts occurred in 22,725 reports or 58%

Wind >20kts but <30kts occurred in 8,577 or 22%

Wind >30kts occurred in 7,829 reports or 20%

The following assessment assumes a helideck which is compliant with Annex 14 Volume II – as implemented in Cap 437. The orientation is not assessed but it is assumed that, if the CAP 437 recommendations have been followed, the Obstacle Free Sector is oriented into the prevailing wind; if this is the case, the figures shown below will be pessimistic.

Using the figures shown above, we are able to estimate the likely proportions of: non-exposed; potentially non-exposed; and potentially exposed, operations.

Non-Exposed

Wind at or below 20kts in all sectors:

Pure PC2 can be flown in 58% of all take-off or landing cases

Wind in excess of 20kts occurring in the 180° sector:

PC2e can be flown in 21% of all take-off or landing cases

This accounts for 79% of take-off and landings.

However, each aircraft has a zero drop down mass that is associated with an unfactored wind - if we assume that this wind is 30kts (not an unreasonable assumption given the figures provided in the calculated masses) then PC2e (without exposure) can be flown for an additional (30/360 x 20%) 1.7% of flights – i.e. when the wind is > 30kts and in the (30°) LOS (no obstacles above deck height).

This raises the non-exposed operations to 80.7%.

Potentially Non-Exposed

Wind >30kts and in the 150° obstacle sector

PC2e with zero drop down occurs for (150/360 x 20%) 8.3% of flights

In these cases, exposure is undefined but is tending to zero. As the wind increases all aircraft reach the point where OEI HOGE is achieved (just below the lowest Vtoss).

The exception to this occurs on those decks with turbulent sectors; this is, and should continue to be, dealt with in the HLL.

Potentially Exposed

Wind is >20 and <30 and in the 180° sector

We have 11% of flights where, potentially, there would be exposure.

In Summary

Operations without exposure are likely to be 80.7% of the total.

Operations where exposure tends to zero is likely to be 8.3% of the total.

Operations with exposure is likely to be 11% of the total.

Conclusions

Whilst there are operations in the North Sea where there is de facto no exposure, this has never been quantified (apart from operations with the AW139). Using the actual wind data and the examples of masses shown previously this can now be done.

We continue to base the take-off and landing masses on the clear area WAT just so we can establish the second segment climb – this is no longer satisfactory.

There were several reasons why there were change to the regulations, the most important of which was to provide a signal to manufacturers that future aircraft should be capable of providing exposure free operations.

To do nothing but justify what is already done will result in the continuation in operation of existing underpowered models and hold out the prospect of no change in the future.


Jim

[Camp Freddie]

my understanding is the implementation date has only slipped from 1st Jan to 1st July 2010 at the moment !

[HeliComparator]

JimL

Trying to leave the personal comments out of it, I still feel that you are not addressing the very point that you mentioned - risk ALARP.

By fixating on engine failures as the only source of hazard, I maintain that there is a danger that you replace one extremely remote hazard with others that, whilst also remote, are possibly less remote than the engine failure during the critical few seconds.

Without a balanced assement of all the risks, I don't see how you can claim that PC2e leads to overall risk ALARP. I agree that such an assessment is not particularly easy to quantify, but to omit it is to be blinkered.

Regarding the point about "the continuation in operation of existing underpowered models" and the nil wind thread, I think you are confusing AEO performance with OEI performance. The former is typically limited by transmission or rotor head and not by engine power. The latter is related to installed engine power.

Therefore there can be no guarantee that operation to PC2E will in any way help the AEO case of some of the newer underpowered aircraft such as the 155 - not too bad OEI due to its engines' 30 sec rating, but pretty poor AEO. Operating PC2e from a high deck would still allow high takeoff mass so not addressing the AEO performance issue.

Modern aircraft with marginal AEO performance can be more dangerous than their predecessors due to FADEC AEO power limiting. In an older aircraft one can in extremis normally pull to max contingency power on both engines. No doubt damaging the transmission but maybe not actually crashing.

Modern aircraft typically limit AEO power to the certified transmission limits, so you won't overstress the MGB but unfortunately you might crash as a result. Even those that have FADEC blowaway are little better because whilst the older aircraft can give max power on both engines whilst the rrpm is still normal, those with FADEC blowaway only give max power once the rrpm has become very low. Since thrust is a function of rrpm and torque, an overpitching crash is more likely in the new types, eg following an unexpected event such as weather or structure-induced downdraft.

So I am all for increasing AEO performance since this has potential benefit on every takeoff and landing, except the 1 in 10^9 when the engine fails during the few seconds of exposure. But its not related to OEI power nor to PC2e.

(sorry for thread drift on to AEO power, but you started it!)

HC

[DOUBLE BOGEY]

Hi Jim,

Thanks for the explanation, I am still digesting some of it. A quick question...how does the proposed mass calculations compare to the existing performance requirements for a HOGE AEO...providing the necessary thrust margin for take-off and landing. This seems to work well with the existing HAPS profiles.

DB

[JimL]

HC,

Deck-edge clearance is dependent upon an acceleration to the RP, this is always achieved AEO. If, as discussed in the other thread, the aircraft cannot achieve this acceleration, it certainly will not be able to meet the requirements of the profile. As is commonly understood, it is kinetic (acceleration and residual rotor energy) and potential energy (height at the RP) that provide clearance from the deck-edge, and OEI power that reduces the drop down.

Exposure does not just last for a few seconds (except for aircraft which can comply with little effort or impact on cost) nor can it ever be contained within 1 x 10**-9 (unless the engines could be made super reliable - in which case we wouldn't be having this debate). With existing aircraft the risk still contains both elements - deck-edge strike, and ditching without a SFL.

With regard to ALARP there are two sides to the equation; before it can be assesed we need to move the discussion back to the operational costs. I would be interested in a re-assessment (using the figures from the RFM provided earlier) of the impact of compliance upon loads and fuel. Is it still the contention that compliance will impact detrimentally upon fuel loads or result in (more than) a 30% increase in flights?

How much endurance does the EC225 have with a take-off mass of 10,875 and 19 passengers?

DB,

I have not compared the numbers so I am not sure; AEO HOGE was the first attempt to set a minimum standard but, as HC points out, it is the combination of AEO and OEI which provides protection throughout the profile. In fact the use of thrust margins to establish take-off masses is extremely difficult to achieve, as is the provision of a simple metric establish the PC2e mass. Notwithstanding that, I still cannot see how the flight conditions stated in the low wind thread would occur with AEO HOGE power (unless someone can explain).

Jim

[212man]

DB,
the procedures normally require a delta torque figure to be used that ensures a minimum rate of climb at the rotation point. This is to ensure deck edge clearance (at least 15ft.) for low decks the RTOM is limited by the drop down available, but as the deck height increases you reach a 'cross-over' point where deck edge clearance becomes the critical parameter, and increasing the height has no further benefit (on RTOM.). So, by definition, there is no specific reference to OGE AEO performance as the graphs have already allowed for the appropriate delta torque being available.

[Lenticular]

Can someone remind me of what the acronym HAPS stands for. I cannot get access to TGL 14 from the JAA website as it requires a password for some reason. Thanks in advance.

JimL - I note that the CAT A elevated heliport profiles on some types require a TDP of 30ft. This is in the avoid curve in light or nil wind. How does that work legally for PC1 which the CAT A profile is designed for. ie onshore off a hospital roof?

Is it that the reduced mass effectively means you are not in the avoid curve - the avoid curve assumes max certified gross weight?

[JimL]

Lenticular,

All phases of a Category A profile have to be outside the HV Curve - in some manuals it does state that the HV Curve is modified by the procedure. A number of CAT A profiles do not result in a reduction of take-off/landing masses. As the profile becomes more vertically oriented, or shortened, there can be a penalty to pay.

HAPS means Helicopter Airfield Performance Simulation - a 2D modelling programme written by WHL. This was superseded later by the 3D RESPECT/EUROPA model (a collaborative project of European research establishments and manufacturers which built on the HAPS model).

Optimised helideck take-off and landing procedures were, under the auspices of the CAA, investigated and modelled by WHL when providing the HAPS profiles. Whilst this work did not lead to (a method for) the establishment of take-off and landing masses, the procedures did reduce the time that the helicopter was at risk. The HAPS procedures (without the provision of masses) have been successfully utilised for several decades.

Here is a description of the HAPS model: "The Helicopter Airfield Performance Simulation (HAPS) program is a modular simulation program, designed to simplify the process of developing new techniques and modelling new aircraft. It has evolved directly from the simulation programs developed over many years to model the dynamic behaviour of a number of helicopters from the Wessex and Sea King to the Lynx and Westland 30.

The model takes the form of a longitudinal flight path simulation. The simulation considers only longitudinal symmetrical forces and motions with the exception of tail rotor thrust and power, which are also calculated because of their effect on the aircraft power required.

The model employs expressions derived from simple strip theory to calculate rotor thrust, collective pitch, rotor in plane force and fore and aft flapping. The induced velocity is calculated from momentum theory, and an empirical factor, based on forward speed and weight, is used to correct for non uniformities in the downwash field. The tail rotor power is calculated from the thrust required to balance the main rotor torque, and the lift, drag and pitching moments of the fuselage are derived from stored wind tunnel data.

An iterative process is used to establish the initial steady state (un-accelerated flight) condition. The dynamic section of the simulation model is then entered and time is incremented in discrete steps. At each time step, control movements and engine power are used to calculate the aircraft and rotor accelerations and a constant derivative integrating process is then used to calculate the aircraft's rate, position values and rotor speed prior to the next time step.

The control inputs may be applied in a number of ways:

Collective pitch defined in data arrays prior to running the program.

Collective pitch automatically evaluated (pilot simulation) to achieve pre defined rotor speed, engine power, rate of descent or normal acceleration patterns

Pitch attitude defined in data arrays prior to running the program required pitch acceleration is calculated, from which cyclic pitch is derived.

Cyclic pitch automatically evaluated (pilot simulation) to achieve pre defined pitch attitude or longitudinal acceleration patterns.

The engine power is calculated using a representation of the static droop law or isochronous rotor governor and is, therefore, primarily dependent upon rotor speed and collective lever position.

Engine failures may be scheduled at any point in the program run, after which the power of the failed engine follows an exponential decay whilst the live engine is allowed (if the engine governor demands it) to increase to a pre determined maximum (typically the brochure maximum contingency level). At less than nominal rotor speeds this maximum power level is reduced to simulate the reduction in turbine efficiency."


Jim

[Lenticular]

JimL - Thanks for the information, its intersesting to get an insight to the development of what we do on a daily basis.

Your statement All phases of a Category A profile have to be outside the H/V Curve is interesting. As an example the Ground helipad CAT A profile for the EC155 has a TDP of 100ft and is a vertical climb to that point. However, the avoid curve starts at 5ft and extends to 300ft. At 100ft, 15kts of wind would put you on the front edge of the H/V curve so assuming nil wind you are well into the H/V avoid area. The only plus is you are mass restricted.

There is no statement in the RFM that modifies the H/V graph.

[Geoffersincornwall]

Len

The dynamics of the situation - Cat A take-off -v- HV Curve - are completely different and it is quite possible that passage through the HV Curve is a necessary part of the Cat A profile.

The certification process for delineating the HV Curve is, I believe, one that is essentially static without the acceleration that characterises a take-off. All Cat A profiles are certified and therefore approved and to achieve that they will have been demonstrated with engine failures at all critical points.

If that profile seems to contradict the HV Curve then I am sure it is only a problem of perception, not a real one.

G. :ok:

[JimL]

Just a couple of other points that should be made:

There was considerable pressure put on the working group by some NAAs and those oil companies who wanted an elimination of the risk of engine failure that, theoretically, a move to PC1 should have provided.

Before NPA-38 was written, there was a time when existing profiles were being considered and risks/benefits quantified. Profiles included those from manufacturers and those resulting from the HAPS modelling – one was for the Bell 212 which I shall return to later in this post.

Further work on the quantification of the exposure periods resulted from examination of the Power-loss Exposure Risk Reports (PERRs) produced by the manufacturers - although some of these PERRs included the HAPS profiles, some did not. (You will remember that the HAPS profiles were intended to reduce risk – one of which results from the degraded FOV that occurs as a result of inappropriate landing procedures. A number of manufacturer’s profiles did not have this as their primary consideration - this might have been as a result of previous certification regulations, the re-use of onshore profiles or a concentration on payload over FOV.)

In order to estimate the effect on payload of the move to HAPS profiles with mass calculations; further modelling was undertaken, using first the HAPS model, and then EUROPA (remember that HAPS is a two-dimensional model whereas EUROPA is three dimensional – the third dimension being required to model the sidestep manoeuvre on landing). Once wind was factored into the modelling, it became clear that the effect on payloads would not be severe except, perhaps, in nil wind conditions and specifically, for drop down. To estimate the effect of environmental conditions on the whole solution, several years of wind data were downloaded from the INTOPS data base (along with temperature and pressure) and conclusions reached.

One disappointment that resulted from the modelling was the realisation that it was extremely difficult to come up with a single metric (from existing data) to provide ease of calculation; the data was presented using ’OEI ratio’ as a common metric but with the three types (a medium, a larger twin and a triple), the ratio for take-off at MUAM in nil wind conditions was respectively 1.36, 1.29 and 1.16 – clearly too wide to provide a basis for the solution. (It was probably the length of fuselage that caused the wide spread).

The output from modelling was collated and the results were presented to all working groups, operators, manufacturers and Authorities – it looked extremely promising. It was agreed to go ahead and replace the requirement for PC1 in 2010 with PC2 (and PC2e); NPA-38 was produced, accepted and the rest is history.

To return to the Bell profile; Bell were one of the first manufacturers to provide a CAT A Helideck procedure. They decided that the best solution (addressing operational constraints) was to utilise an upwards and sideways acceleration. This provided two benefits: the FOV to/from the deck would not be an issue; and the TDP would be positioned at the same point as the LDP. In the event, the procedure was ahead of its time and was not extensively used. It does continue to be used at Bell and evidence of it can be seen in the CAT A procedures for the B427 and B429 (and a very comfortable procedure it is - as those who have flown it will testify)

However, now that examination of the wind data shows that about 37% of the total departures could occur when the helicopter is facing into the 150° obstacle sector, it might be time for operators to revisit the merits of the Bell 212 take-off on those occasions. No, this is not an answer to issues with turbulent winds from the 150° sector (some of which are addressed in the HLL) but, as has already been explained, this is not a process that always has a deterministic outcome – and explains why the authors of AL5, quite righty, put PC2e in the Exposure loop.

In addition, this profile (or a form of it) can be used for departures from a well-head platform – particularly when flown with more powerful helicopters. With an engine failure before RP in the departure, the deck will remain in sight and a reject can be quite easily undertaken. This is a matter of training only – the performance figures should not be substantially altered (in fact it may assist because I am informed that there is a penalty applied by some operators)

None of this affects the 80% - 90% of departures which could now be undertaken without exposure.

Oh, and I still have not had the answer the question “how much endurance does the EC225 have with a take-off mass of 10,875 and 19 passengers”. Perhaps one of you can PM me the answer to that.

Jim

[gmrwiz]

Geoff,
what you say about the HV curve, is wrong.
CS29.59(a)(1) "Take-off path:Category A" establishes the requiremnts .

If a Cat A profile penetrates the "true" HV envelope a Rejected Take-off /Landing can not be carried out.

The "true" HV envelope is a family of variable HV envelope as a function of the Take-off/Landing Mass and density altitude.

Quite often, manufacturers do not spend to many efforts in defining the HV curves but simply presents the biggest envelope valid for the maximum density altitude and Maximum Take off/Landing mass.

In this case a Cat A vertical TO/Land procedure, carried out at a specified mass and at a specified DA, migth cross the HV.
But if it has been demonstrated that in those condition a RTO/OEI Land can be carried out, no doubt that the trajectory is outside the HV.

The region outside the HV envelope is a safe OEI reject take off and landing area. And this is also the requirements defined by Cat A.

gmrwiz

[JimL]

Just to round up the data that was shown on the earlier posts, I have added the S92 masses to those which have already been provided.

Just in case you do not wish to read the other posts, the figures are:

For the S-92:

Taking ISA SL conditions the following masses are provided by the graphs:

Take-off:

The Pure PC2 mass is 26,250lbs

The PC2e mass with an unfactored wind of 20kts is:

26,500lbs for a 50ft drop down

Zero drop down is achieved with an unfactored wind of 30kts

Landing:

The Pure PC2 mass is 26,500lbs

The PC2e mass with an unfactored wind of 20kts is:

26,500lbs for zero drop down

Zero drop down is achieved with an unfactored wind of 20kts

The answer to my question about the endurance of the 225 with 19 passengers appears to be about 2:18 endurance (plus 10% and final reserve fuel).

Jim

[Shawn Coyle]

gmrwiz:
The Category A profiles will have been flown and tested to be safe. There will be a statement in the front of the Category A supplement (if there is a supplement) that the HV curve is no longer applicable when using the performance and procedures for Category A.
Mixing apples and oranges.

[Droopystop]

JimL,

Thanks for the insight into PC2e which I thought was dead as far as the North Sea is concerned?

Alot of what you have put on here shows how much impact PC2e would have over the current status quo.

Some observations:
Whilst new decks have to be designed according to CAP 437 (IIRC) there are plenty of existing decks out there which don't seem to comply according to my layman's eye. These are the decks which will (should) really feel the impact of PC2e and to be honest, we would be better served by a new deck rather than new paper work.

You sight seastate 4 as a limit for what can be considered a "safe" ditching. Surely that is aircraft specific (stability and float fit and so on). To limit PC2e to SS 4 might be a disincentive to offer/buy SS5 or SS6 float kits. Also evaluation of seastate is location specific (which wave spectrum to use) and subjective - who is qualified to judge?

It is going to be interesting to see how PC2e will be introduced and what training will be required to fly it.

[JimL]

Droopystop,

The issues should not be confused; an existing deck which does not fully meet CAP 437 compliance will/should be limited by the HLL - this will not change with compliance with the requirement (i.e. no real change there).

It is not clear to me (from the numbers that have been posted) that the impact would be severe for modern aircraft. Look again at the operating masses for your particular aircraft and see what the impact would be. For example, if you are operating the EC155 in zero wind the Pure PC2 mass is 4,750kg - the restricted operating mass with less than 5 kts wind is 4,620kg (which should continue to be applied) and with up to 10 kts, 4,770. In this case the problem is with the aircraft not the system.

There is no Sea State limit on PC2e; the regulation permits Pure PC2 when a Safe-Forced-Landing can be carried out. It is generally accepted (borne out by the ditching approval which mandates the SS4 requirement for all helicopters - and sets the parameters) that a SFL can be achieved in SS4.

For Sea States over 4, PC2e should (in the majority of cases - see my post on the effect of compliance) provide engine-failure accountability. The hard break of 20kts wind between PC2 and PC2e (should it be accepted) will make this transition seamless.

If you have been flying the HAPS procedures (as described in JARs) there should be no substantial change in procedures.

Jim

[Geoffersincornwall]

Excuse me but I could not help but chuckle when I read the assertion that all new decks are built to CAP 437. My experience is that the first time anyone gets to look over 437 is when it's being towed out to the field and the oil company rep is scratching his head wondering how the vent stack ended up in the 210 sector. And that's in Europe - You should take a look at what goes on elsewhere - and no HLL either. When I see pictures of some of the GoM decks I wonder if we are on the same planet.

G. :ugh: :sad:

[spinwing]

Mmmmm ...


Well then Geoffers .... you would be absolutely STUNNED .... by what gets approved (?) in the "Middle East" ...... :=



:ugh:

[gmrwiz]

Shawn,
I am not mixing anything.
I am just pointing out what the airworthiness code (european and american) requires:


And this is logic because 29.87 establishes:

[QUOTE 29.87 Heightvelocity envelope
(a) If there is any combination of height and forward velocity (including hover) under which a safe landing cannot be made after failure of the
critical engine and with the remaining engines (where applicable) operating within approved limits, a heightvelocityenvelope must be established for:
(1) All combinations of pressure altitude and ambient temperature for which
takeoff and landing are approved; and
(2) Weight, from the maximum weight (at sealevel) to the highest weight approved for takeoff and landing at each altitude. For helicopters, this weight need not exceed the highest weight allowing hovering out of ground
effect at each altitude.

In other words the Cat A and the H-V requirements prescribe to carry out a safe landing after an engine failure.

The only difference is that H-V does not require to reject on the take-off area while Cat A requires.

By the way I have never seen in the Flight manual Cat A Supplement the statement you mention that H-V is not applicable to Cat A.
gmrwiz

[Paul Fraser]

"The answer to my question about the endurance of the 225 with 19 passengers appears to be about 2:18 endurance (plus 10% and final reserve fuel)."

As per my PM to you, in the 225s I fly you can lift with 4800lbs of fuel plus 19 pax and around 500lbs of baggage, if not more. At a burn rate of 1400lbs per hour this is 3 hours 25 minutes to tanks dry. (BTW, this is how I have always calculated endurance; if I am supposed to take off final reserve fuel and 10% then it is news to me).

[JimL]

Thanks Paul,

Perhaps I ought to have set out my thinking; I was trying to establish whether take-off mass of 10,875kg would be limiting - i.e. if I had to move 19 pax and their bags, would such a mass result in me flying with less fuel.

It wasn't so much endurance that I was looking for but the length of leg (plus any alternate) that could be flown. If this were to be planned, then it would consist of (simplistically):

Leg fuel (and alternate if one were required)

Contingency fuel of 10%

Final reserve fuel of 30 minutes

Subtracting my FRF and then 10% contingency provided the maximum fuel for the leg(s) which was 2:18 (the useful time that could be planned for any leg(s)). The only difference was that I used a fuel burn of 1440lbs/hr.

I'm not sure that any of this matters too much now because it is becoming clear that compliance with the rule does not result in additional risk due to either: a limitation on the amount of fuel that can be carried; or, a reduction in passenger loads such that additional sectors would have to be flown.

Jim

[HeliComparator]

Jim

A few thoughts, though insufficient time for a comprehensive post:

1) The figures I have for INTOPS wind bear no relation to what you posted earlier. Its much more common to have wind <20kts

2) Even if we assume that your gentleman's agreement that SS4 is acceptable for SFL, how do we the pilots know what the current SS is? Do all offshore installation have such measuring equipment? Would it be accepted by the regulator?

3) If I could always takeoff in my 225 at 10875kg then this reg would not be much of an issue, but you are chosing your data carefully to make the best of it.

4) You are using graphs from EC that require 30' TDP for deck edge clearance, this is getting dangerously high for night (or even day with my flying)

Finally, if you are saying that the impact of this reg is insignificant in terms of fuel, payload etc, then what you are equally saying is there will be no change in the general risk from engine failure compared to now (since you will not be making us fly any lighter), and what you are doing is introducing a huge level of additional complexity (viz EC PC2e supplement running to 49 pages) that you expect pilots to comply with "in anger" eg during the normal in-flight route changes, weather changes etc. Pilot A - heads down trying to read the graphs at night whilst pilot B flies into the water! As I said previously, an overall reduction in safety.

HC

[WOP]

You should take a look at what goes on elsewhere - and no HLL either. When I see pictures of some of the GoM decks I wonder if we are on the same planet.

Geoffersincornwall, have you got ay examples at hand?

[Geoffersincornwall]

In my CP days we would have looked at the problem, found a suitable 'rule-of-thumb' that met the ambitions of the regulators and written that into our SOPs in 'simplespeak.

In the 80s we circumvented the prospect of line-joes mis-reading the RFM and its acres of similar looking and sometimes obscurely drawn graphs by simply stating that if you were operating from airport A, B or C (the only places we were contracted to work from/use as alternates) and you operated with 2000 feet of runway then you could use cAT A Clear Area profile every time up to 25 degrees C.

Surely if the normal procedures are followed and the risk management requirements are thereby met there is no need to get into complex pre-landing or pre-TO computations. In Risk Management terms such endeavours may actually increase risk. I think the acronym is K.. I.... S....S!

G. :ok:

[Geoffersincornwall]

I am no Test Pilot but seems to me we are talking in circles.

1. If a take off or landing profile is 'certified' (accepted by the authorities as Cat A compliant) then it cannot by definition conflict with a mandatory (listed in the 'Limitations' section of the RFM) HV envelope.

2. My AW 139 has a Vertical Helipad profile with optional TDPs between 35 and 70 feet and a Short Field Take Off (vertical ascent to TDP) with TDPs between 85 and 400 feet ATS, published as Cat A compliant.

3. These profiles are clearly in conflict with the HV envelope.

4. The size of the HV envelope is variable according to WAT inputs but the TDP options are not WAT-dependent.

Maybe somebody who knows how this apparent conflict can fit into our understanding can explain it to me and not just quote isolated bits of the FARs/JARs without sufficient explanation.

Thanks and sorry for the minor thread-drift.

G. :ok:

[tistisnot]

Couldn't agree more about KISS - no-one stops to determine such data other than a RTOM/W or different rotation point. Whereas I thank JimL for his elegant elucidation of the points in question, on the line or answering the even more baffled client, we need to end up with simple reasoned profiles and procedures backed up by relevant training and supervision - and not complicate it with hypothetical gobbledeespeak forced upon us by the regulators.

[HeliTester]

Geoffersincornwall and Shawn Coyle are right on target, citing “the dynamics of the situation” and that “the Category A profiles will have been flown and tested to be safe.” A helicopter climbing vertically through a 100 ft TDP is in a substantially different energy state than a helicopter hovering at 100 ft.

Subsequent to single engine failure during vertical climb through 100 ft the pilot can lower the collective stick to contain the rotor droop while the helicopter continues to ascend to its peak height. By the time the descent begins, the remaining engine will have spooled-up and the rotor speed set to just below the governed speed thereby providing that OEI maximum contingency power is available throughout the descent. That’s why helicopters like the EC155 with Certified Category A helipad procedures can climb vertically to a TDP on the order of 100 ft, and successfully land back. This will have been demonstrated at up to the maximum helipad takeoff weight for altitude and temperature by both the helicopter manufacturer and the certificating authority prior to achieving Category A certification approval.

I have not seen the EC155 Category A Helipad Flight Manual Supplement, but it’s hard to believe that it doesn’t address this issue. This is addressed for other helicopter models. For instance, in the Limitations section of the S-76C+ Category A Helipad Supplement it states that “using the procedures and gross weights described in this supplement, it has been demonstrated that safe operation within the avoid area of the height-velocity diagram can be maintained if a single engine failure occurs at any point along the takeoff and landing flight paths.”

[JimL]

HeliComparator,

Equally short:

1. The INTOPS winds are those supplied for the PC2e modelling and had a mean of 20kts (there has been no untoward manipulation). The winds shown were for the Northern and Central North Sea; if the winds for the Southern NS are included, then the mean will reduce to below 20kts. With a mean wind <20 kts, the number of exposure free operations will increase because more operations can be flown within the 180 obstacle free sector.

2. The suggestion is that the hard break (between Pure PC2 and PC2e) should be related to reported wind (at SS4), with high sea states taken into consideration only when they are at odds with the reported wind - i.e. wind has dropped but the sea is still running high (using rule of thumb). Getting this wrong (at the margin) has no serious consequence. It is also understood that a number of companies would apply PC2e at night - particularly in Norway.

3. I would agree with you that there will be little change for the EC225 (or the S-92) - because of this, simpler metrics could be applied. For the AW139 there will be no change.

3. Yes the helideck CAT A take-off profiles have been used.

When PC2e was conceived, it was not intended to add complexity to operations. The work was done in the face of the pressure to move to operations in PC1 by 2010. The alternative (PC2e) was provided to show that the 'bar' could be raised by providing a safety-net to reduce exposure ALARP - i.e a removal of unfettered exposure offshore.

Yes the EC Supplement runs to 49 pages but it is based upon two graphs with many, many examples.

It was fully accepted that the modern types that were just about to appear on the North Sea would have no problem meeting the standard (as has been demonstrated). It was also accepted that there would be an effect on older types but it was projected that most of these would have left the North Sea by 2010 (remember that this work was started in about 2002).

There were also secondary objectives. It was felt that mass growth should be tied to a performance standard - the second segment climb performance was seen as as weak metric (that is why the AEO HOGE was brought from guidance and put into the rule - for all operations with exposure). There was a need to ensure that future aircraft had a built-in level of performance for offshore operations. (The working group were mindful of a remark that had been made at the time of the introduction of exposure that, in future, installed power could be reduced accordingly.)

A number of these objectives have already been met but some have not. The introduction (of most) of the modern types has improved the situation - this is in no small part due to the introduction of the new requirement with an implementation date of 2010. Manufacturers have strived to provide aircraft that meet the 2010 standard and they are to be congratulated for that.

Jim

[HeliComparator]

Jim

1) Mean of 20kts I can believe, but you said earlier that wind was 20+ for 81% of the time.

Yes the EC Supplement runs to 49 pages but it is based upon two graphs with many, many examples.

Two graphs but repeated 3 times for 3 possible values of Nr. The Nr value not surprisingly has a significant impact on deck edge clearance. So the pilots have first of all to work out what the hover Nr will be (based on density altitude and using a graph in the main part of the RFM). Assuming they are not lucky to have the Nr exactly as in one of the graphs, they then have to go into 2 sets of the graphs for 2 of the Nr values, then interpolate the answers. IMHO this is unrealistic to do in flight.

HC

[JimL]

Thanks HC.

I have looked back at my text - the post with the distribution of wind is fairly clear; however, I am not an error free zone.

I could have sworn that the graphs in the Complementary Flight Manual were identical - are they different in the RFM? I agree that this should not be done in flight - haven't EC provided an EFB yet.

Going back to the text of the rule; the wording is much more flexible than it is for PC1; I can't see how it could have been more operator/pilot friendly unless it had said 'please yourself'.

Now that we have shouted ourselves hoarse, perhaps we could just sit down and make it work to everyone's advantage. Explain to me why we didn't do this over the phone or on email! Perhaps because it is not just you and I who have to understand and work with this but other operators, pilots and regulators.

This can't be more difficult than trying to establish the best Vtoss to get over that 14ft mast on the end of 14 can it?

Jim

[bpaggi]

[. If a take off or landing profile is 'certified' (accepted by the authorities as Cat A compliant) then it cannot by definition conflict with a mandatory (listed in the 'Limitations' section of the RFM) HV envelope.

2. My AW 139 has a Vertical Helipad profile with optional TDPs between 35 and 70 feet and a Short Field Take Off (vertical ascent to TDP) with TDPs between 85 and 400 feet ATS, published as Cat A compliant.

3. These profiles are clearly in conflict with the HV envelope.

4. The size of the HV envelope is variable according to WAT inputs but the TDP options are not WAT-dependent.
]

Geoff

I wonder how you can make statements like these. A Cat A profile, by definition and by certification rules, can never interfere with the H-V area because if this would happen, the fundamental requirement of a safe landing, could not be achieved.

Since you have to demonstrate that at any point of the take off profile before TDP you can safely land after engile failure or you can carry out a Continued Take Off after an engine failure at or after TDP, there is no way H-V can interfere with Cat A.

The AW139 Cat A profiles (6 different techniques) have been certified and are compliant with these rules.

I strongly reccomend you to carefully study RFM Supllement, this will avoid to rush to not correct conclusions.

[gmrwiz]

Geoff,
you are not an attentive reader of your AW139 Flight Manual.
I explain why.
If you compare the Cat A weights, obtained from the Cat A WAT charts for the procedures you mentioned in your post i.e. Vertical Profile and Short Field, with the weight for which there is no H-V you will see, unbelievable, that the CAT A weights are always lower than the weights for NO H-V.
Some examples.

PA:0ft, OAT=40°C
Cat A weight ( Page S12-A32 and S12-B16 of the Suppl.12 to the 139 RFM):6400 Kg
NO HV weight (Page 1-17 of the basic RFM): HV does not exist

PA:5000 ft, OAT:20°C OAT :0°C
Cat A weight : 5880Kg Cat A weight: 6220 Kg
NO HV weight : below 6000Kg HV weight: HV does not exist

PA :10000ft , OAT:0°C
Cat A weight : 5220Kg
NO HV weight : below 5400Kg

You can continue the exercise by checking different procedures and environmental conditions but the results will be always the same i.e:

Cat A weight are always lower than the NO HV weight.

And this is obvious because this is the prerequisite that makes possible to reject the TO after an engine failure.

If you don’t trust me and you want to know more about the H-V and the way in which is determined I suggest to read the AC29 Page B-92 (it may be downloaded from http://http://www.faa.gov/regulations_policies/advisory_circulars/index.cfm/go/document.list/parentTopicID/107) .
You will realize that the HV is not always defined by failing the engine in steady flight.
This is true for the cruise region of the HV envelope.
The Take off region is defined by failing the engine along the TO profile at various height and speed. Therefore in a dynamic condition.

Keep off the HV. Remember its nickname.

gmrwiz

[Geoffersincornwall]

I think you have misunderstood my views. If you go back a few posts you will see that I agree 100% with your assertion.

Maybe I should have said 'apparently in conflict'

Shawn and I are arguing the point that certified Cat A profiles are ALWAYS safe to use if you apply the WAT curves correctly.

It's MrWizz that seems to be having a problem with this.

G. :ok:

[helmet fire]

Some irrelevant observations from the outside:}

Irrelevant rants removed. Thread creep alert down graded.

hf

[paco]

"The Bell 212 CAN be operated Cat A and PC1. Just reduce payload"

In Dubai, that will allow you one passenger. The max weight in Summer is around 8500 lbs! :) It's only 10,000 max Cat A anyway.

Phil

[bpaggi]

I'd like to add some more thoughts to this discussion.

PC2e has been invented most likely because most of the helicopter used in offshore can not afford PC1 operations at a decent weight/payload.
Furthermore I keep hearing that PC1 operations are not possible offshore due to several constraints and too variable weather/environment conditions.

At AW we think differently and we worked hard to provide several Cat A procedures one of which is specific for offshore operations.

We realized the peculiarity of this environment and we understand that in several situations PC1 is not possible. But we also think that in several scenarios this is possible and it is much safer if this actually carried out.

The AW139 Cat A offshore procedure (EASA certified) provides not just full protection from engine failure but allows much greater obstacle margins than most of the current procedures.
It has been constructed based on operation requirements and with pilot work load in mind.

This procedure does not implies pitch variations greater than -10° and +5° during the take off profile regardless there is an engine failure or not. The take off maneuver has a delta TQ application that is proportional to the hover performance in order to keep the RTO ballooning at the same height.
The TDP is the lowest possible (20 ft) but rotation point is at 30 ft in AEO and OEI.

The deck edge clearance is at least 100 m in the worst conditions with take off from the center of the deck.

The biggest drop down you can ever experience is 50 ft at max weight (6800 kg) during take off and not lower than 0 ft for a balked landing.

All this is at zero wind.

There is very little weight penalty in most of the hottest ambient conditions and almost no penalty with just 5 kts of factored wind.

This is not meant as sale pitch but an attempt to provide evidence that safety is not just performance but also obstacle clearance, power margins, controllability margins, easy to fly and a good pilot confidence.

I hope that PC1 offshore (and on shore) will be used all the times this will be feasible and I hope operators will give us all the necessary feedbacks in order to make the operations safer.

[HeliComparator]

bpaggi

Its well known that the 139 has very good OEI performance, making an engine failure in nearly any phase of flight a non-event.

However the penalty for that is large engines with poor cruise fuel consumption, resulting in an aircraft that has poor range-payload.

When the manufacturers can produce a helicopter with good OEI performance AND good range-payload, it will be a good helicopter indeed. In the mean time, personally I prefer the low stress of good range-payload in my 225 rather than the elimination of one way to crash (engine failure during exposure) which is very far down on the list of ways to crash in terms of occurrance rate.

HC

[bpaggi]

HeliComparator
You're right on the low occurrences of crashes due engine failures. My point is another.
The huge difference in flying aircraft like the 139 is not in the OEI performance (that are anyway outstanding) is the daily operation carried out in AEO conditions as I stressed in my post.
Safety in operations on helidecks are also provided by good AEO power margins, aircraft controllability, cross wind capability (45 kts at all azimuth for the 139) and possibility to carry out approaches, landing and take offs with the best obstacle clearance possible.
At AW we did not traded safety with range, on the contrary we have provided the highest safety standard with the best range capability in its class.

I hope you'll never brief your passengers that the aircraft are flying in has a very good range but some exposure in the most critical part of the flight!

[HeliComparator]

bpaggi

daily operation carried out in AEO conditions as I stressed in my post

To me your post seemed primarily about CAT A which is surely mostly about engine failure accountability? But I totally agree that good AEO performance is important for safe day-to-day operations. I have never flown the 139 and I don't know what its AEO performance is like. I do seem to recall that AEO max gross weight has recently been increased and this is surely only to improve the range-payload, not to improve safety, so AW is not totally saintly in this regard!

A safe helicopter has the attributes you mentioned, but also others such as good visibility from the cockpit, carefree handling including intuitive automation, and a good HMI. Those are the bits that help reduce operational accidents, but of course there is also the design of the mechanical bits - eg failure modes all identified and allowed for, good VHM system etc. and just plain high reliability of critical bits!

I don't know where the 139 stands on these points, but I do notice that it hasn't had much market share in terms of offshore helicopter sales. Why do you think that is?

HC

[bpaggi]

HC

The 139 is a relatively new product.
We have sold 460 units so far, almost 40% of these are for offshore operations.

[HeliComparator]

bpaggi

That's about 180 aircraft for offshore then, which is a lot. There are none that I can think of in N N Sea, not aware of any in SNS maybe 1 or 2 in Holland, so out of curiosity, where are they all? (yes, I know its a big world outside of UK waters!).

Oh just thought - do you mean "options" or "ordered" or "delivered" when you say "sold"?

HC

[bpaggi]

460 are ordered, delivered are about 230. CHC operates several 139s in NS. All the others are around the world.

[JimL]

In providing the analysis of exposure on one of the first pages of this thread, I inadvertently placed the 20kts wind into the >20 and <30 grouping. This had a substantial effect on the outcome of the analysis because that was the mean wind. This was pointed out by HC but it did not immediately sink in at the time.

I apologise for those who were mislead - I have corrected the original post and have put it 'in quotes' in this post. In fact, the effect of the revision of the analysis shows that I overestimated the amount of flights that would still be exposed when complying with the regulations.

Jim

Here is an attempt to quantify the benefit of the extant regulation with respect to the reduction in Exposure; in order to do this it is necessary to establish those operations which are potentially:

without exposure; and

where exposure might remain.

Firstly we need a reasonable basis for assessment. During the modelling of PC2e, access was provided to an operator’s database of weather reports (INTOPS).

INTOPS provided us with 39,131 North Sea wind data points (reports) for a four year period. Using this data we established that:

Wind <= 20kts occurred in 22,725 reports or 58%

Wind >20kts but <30kts occurred in 8,577 or 22%

Wind >30kts occurred in 7,829 reports or 20%

The following assessment assumes a helideck which is compliant with Annex 14 Volume II – as implemented in Cap 437. The orientation is not assessed but it is assumed that, if the CAP 437 recommendations have been followed, the Obstacle Free Sector is oriented into the prevailing wind; if this is the case, the figures shown below will be pessimistic.

Using the figures shown above, we are able to estimate the likely proportions of: non-exposed; potentially non-exposed; and potentially exposed, operations.

Non-Exposed

Wind at or below 20kts in all sectors:

Pure PC2 can be flown in 58% of all take-off or landing cases

Wind in excess of 20kts occurring in the 180° sector:

PC2e can be flown in 21% of all take-off or landing cases

This accounts for 79% of take-off and landings.

However, each aircraft has a zero drop down mass that is associated with an unfactored wind - if we assume that this wind is 30kts (not an unreasonable assumption given the figures provided in the calculated masses) then PC2e (without exposure) can be flown for an additional (30/360 x 20%) 1.7% of flights – i.e. when the wind is > 30kts and in the (30°) LOS (no obstacles above deck height).

This raises the non-exposed operations to 80.7%.

Potentially Non-Exposed

Wind >30kts and in the 150° obstacle sector

PC2e with zero drop down occurs for (150/360 x 20%) 8.3% of flights

In these cases, exposure is undefined but is tending to zero. As the wind increases all aircraft reach the point where OEI HOGE is achieved (just below the lowest Vtoss).

The exception to this occurs on those decks with turbulent sectors; this is, and should continue to be, dealt with in the HLL.

Potentially Exposed

Wind is >20 and <30 and in the 180° sector

We have 11% of flights where, potentially, there would be exposure.

In Summary

Operations without exposure are likely to be 80.7% of the total.

Operations where exposure tends to zero is likely to be 8.3% of the total.

Operations with exposure is likely to be 11% of the total.

Conclusions

Whilst there are operations in the North Sea where there is de facto no exposure, this has never been quantified (apart from operations with the AW139). Using the actual wind data and the examples of masses shown previously this can now be done.

We continue to base the take-off and landing masses on the clear area WAT just so we can establish the second segment climb – this is no longer satisfactory.

There were several reasons why there were change to the regulations, the most important of which was to provide a signal to manufacturers that future aircraft should be capable of providing exposure free operations.

To do nothing but justify what is already done will result in the continuation in operation of existing underpowered models and hold out the prospect of no change in the future.

[139GoM]

Do you see the CAT A offshore TO/LDG profile being FAA approved in the near future? Also someone at Augusta needs to talk to Gulf of Mexico operators and understand a different enviroment than other areas in the world. The biggest concern, deck size, the current deck size, 72x72' only on a few floaters coming into the gulf. 50'x50' deck are more common while 40'x40' decks even more popular. Augusta needs to talk to GOM operators and get the certification and for the smallest deck the operators operate from.

[Shell Management]

The US needs to outlaw under size decks!

The shake up after Deepwater Horizon and the replacement of the lax MMS regieme will only increase the chances of rigorous enforcement of sensible, internationally compatible, requirements.

[Gomer Pylot]

139GOM: Are you talking about Augusta, Georgia? Who in Augusta, Georgia cares about the GOM?

Call me cynical, but I don't think much is going to change. The oil companies care about only short-term profits, because that's what management bonuses are based on. They will resist to end anything which might lower those, and won't spend money on new heliports unless forced to by regulation. New regulation, after the investment of a few hundred thousand dollars in campaign contributions, is unlikely.

[HeliTester]

Just read the October 15th inputs to this thread. Looking backward, there was a flurry of activity in the February-March timeframe, but nothing between then and October 15th.

Back in February-March it was stated that PC2e is a quasi-PC1 procedure that provides zero-exposure engine failure accountability, but apparently with a reduced useful load. The ensuing debate discussed the merits of pure PC2 vs PC2e, even speculating that for various reasons pure PC2 might be safer than PC2e.

It was also mentioned that the implementation of PC2e had slipped from January 1st to July 1st 2010. July 1st has passed, so does anyone know the current status of PC2e? Is it now implemented or has the implementation been further deferred?

[zalt]

Wasn't PC2e stopped as a flawed regulation because the net effect would have been increased accidents?

[HeliComparator]

It hasn't been implemented in the UK yet.
HC

[Shell Management]

ZALT PC1/PC2e is an essential part of 7/7=1 which Shell launched nearly 6 years ago. Obviously it took time for the OEMs to put procedures in place and to get higher performance machines in place, but such an important part of 7/7=1 was high priority and helped drive many fleet renewals around the world with EC225, S-92, AW139. EC155, EC135 etc.:ok:

[HeliComparator]

Or to put it another way, lets take steps to eliminate a hazard that has never manifested itself, and in the mean time increase the risk from various other hazards...

HC

[ppng]

Shell guy
You say that "nearly 6 years ago" Shell started 7/7=1 and that led to Eurocopter developing the EC225? The 225 was approved by EASA in 2004 and so was in development for many years before that - get over yourself!

[sox6]

Can anyone (HC, JimL etc) explain why PC2e wasn't introduced in the UK to the JAR-OPS 3 date but it could in the Netherlands? I get the impression there is an interesting 'backstory'.

[Shell Management]

ppng - you have not understood the complexity of aircraft contrating.

I was refering to renewal of the Shell fleet by placing contracts with operators using new aircraft like the EC225. It is not possible to confidently place a contract on an operator to operate a new aircraft until the aircraft type is certified, delivered and added to their AOC.

Often you need to plan 14-18 months in advance to get an aircraft off the production line.

When putting in place new contracts Shell Aircraft policy is also to then wait for the fleet leader to reach, IIRC, 750hrs and the fleet around 1500hrs before they start on Shell contracts so that any major airwothiness problems can be identified, to allow personnel to build experience to meets Shell's minimum experience levels on the type and to demonstrate general offshore operational suitability.

However Shell, as the leaders in offshore safety, did have to pressure the OEMs to produce the right procedures for PC2e. It is sad that the oEMs failed to progress this quickly enougth. Hopefully the EC175 will have PC2e out of the box.

Now those procedures are available, Shell operations can be conducted to PC1 (or PC2e when PC1 is not possible), addressing a remedial action from the 7/7=1 safety case!:ok:

Yet again Shell Aircraft's efforts in raising safety by eliminating the hazard of deck or water impact after and engine failiure need to be applauded. In particular such RW1D deviations from the intended safe flight path are the number one risk in offshore operations.

It is just this sort of Shell Aircraft initiative, plus the adoption of safety cases and SMS and all the other 7/7=1 actions, that are moving helicopter safety towards the levels of safety that can be achieved on regular fixed wing passenger flights.:D

You can read more here - which includes a safety case:
http://www.ogp.org.uk/events/06/11-MMIR/10OGPWorkshop-ManagingMajorRisks-Aviation.pdf
or here which shows how Shell lead the way:
http://info.ogp.org.uk/tpes/Programmes/aviation/Breakout1/LongTermSafety.pdf

Sox6 - the UK CAA have rather lost the plot on offshore safety leadership. Its mainly down to turnover in personnel it seems.

[Hell Man]

Typical post from SM:

Yada yada yada shell, yada yada yada shell, yada yada yada shell, etc. etc.

:zzz: :zzz: :zzz:

ps: your love affair with shell is so sickening that is makes anything worthwhile you may have to say - of little interest!

[Shell Management]

I love the safety that 7/7=1 brings and really want to see that spread across the industry to save lives.

[Hell Man]

Well if you could love the safety a little more and shell at little less we would all be very f**king grateful!

[HeliTester]

Sox6 asked the question Can anyone (HC, JimL etc) explain why PC2e wasn't introduced in the UK to the JAR-OPS 3 date but it could in the Netherlands? I get the impression there is an interesting 'backstory'.

Shell Management responded with the UK CAA have rather lost the plot on offshore safety leadership. Its mainly down to turnover in personnel it seems.

What I find disturbing is that OEMs must comply with JAR-29 Certification rules in order to get Certification Approvals to field their aircraft, while it seems that operators and/or JAA member states can opt to not comply with JAR-OPS 3 Operating rules when operating those same aircraft. Why the apparent double standard?

[TomBola]

.... was refering to renewal of the Shell fleet by placing contracts with operators using new aircraft like the EC225. It is not possible to confidently place a contract on an operator to operate a new aircraft until the aircraft type is certified, delivered and added to their AOC.
.... Caverton Helicopters fleet before being awarded a major Shell contract - 2 Bell 412, couple of AS350B2 (oh, no, singles :eek:) couple of refurbished ancient DHC6.

[Shell Management]

Just look at the massive enhancment in the fleet since Shell's contract award with more new aircraft ordered via their JV partner:ok:

Bristow Helicopters wasn't much to speak of when Shell gave them their first proper contract in 1955.

[Cdn driver]

My god man, get over yourself!
:rolleyes:

[squib66]

The UK CAA have issued an exemption for the NPA they created! Other EU countries are following the JAA deadlines.

So much for that old chesnut that the UK complies with everything from Europe and the continentals don't bother.

[Variable Load]

ZALT PC1/PC2e is an essential part of 7/7=1 which Shell launched nearly 6 years ago..So SM, back to the PC2e debate. How many of Shell's contractors are using PC2e offshore?

Please produce a list:
Bristow:
Caverton:
CHC:
Others:

I'm sure it will make interesting reading.

[Shell Management]

It should be all, with the exception of certain aircraft like the Mil 8 and contracts that pre-date 2005, provided that appropriate procedures are in the RFM.

Shell OUs have invested massively in new machines partly, with more to come, for this heightened performance for PC1/PC2e and of course the improved certification standards.:ok:

I will verify and report back.

[sox6]

Any news on your research SM beyond the Netherlands?

:E

[Variable Load]

Any news on your research SM beyond the Netherlands?

I can add Brunei and Malaysia (S92 only - not EC225)

After that I suspect the sheet will be blank. :mad:

6/7=0.8571248 just doesn't have the same ring to it :E

[DOUBLE BOGEY]

The most interesting statement to come from this debate is JimLs explanation of the lack of visual cues avaiable to the pilot during landing - and as he explains, that spawned the necessity of the HAPs model.

In effect this statement (if true, and with a bit of offshore experience myself I think it is) pretty much kills any attempt to adopt a predictive performance environment for offshore.

Therefore, is it right to even attempt to define and control the many variables in play and of course the answer will always be YES, otherwise progress would never happen.

Having said this I am with Geoffers on this one. The environment we operate in offshore is dynamic, often unstable and always demanding. To even imagione how crews would fare when faced with the potential of complex computations, that due to the variables at any one minute changing, are probably inappropriate and flawed is one thing. To consider the chaos caused to the transport system (which is what we are part off) is unimaginable.

Some things in life get invented early on and they are pretty darn perfect. The wheel being one of them that springs to mind.

In my opinion, the work done all those years ago to define the HAPs modelling, and the slight adjustment by JAR to give a bit of thrust margin (AEO HOGE), is the "wheel" of the offshore environment.

I am somewhat dissapointed that so much effort has been expended into this issue and so little effort expended to tidy up and improve on what we have now. In my experience, majority of Offshore CPs occur way to low. Typically about 20 to 25 feet, and some significantly lower than that.

And yet the HAPs wants us at 40 feet ADH (I figure I noticed entirely lacking in JimLs disitations above (sorry JimL - sure this was just an oversight).

I challenge every Offshore pilot to look closely at their own personal CP profile. For the avoidance of doubt, and in concurrence with JimLs early posts, HAPs says we should have:

10 Knots G/S, rotor tips coincident with the deck edge, 40 feet ADH at the CP.

That is the equivelent of the 5 story block of flats above the deck.

For those of you who are too low, try the HAPs profile properly and you will be amazed at how much better the profile feels.

Geoffers is absolutley right in my opinion. The proposal is not only too complex, it is probably ill conceived from the outset.

Finnaly. in all of this little discussion has been made as to the mitigation of exposure (when it exists). Remember that JAR 3.517 carried a significant burden for the Operator and the Aircraft to reduce the possibilities of OEI by mandated use of HUMS, Reliability, training and of course profiles utilised to reduce the risks of Exposure in so far as is possible in the environment (the HAPs model).

The apparent lack of in service OEI events in the landing and take-off phase bears testiment not only to the helicopters inherent reliability, but the value of these mitiogation tools.

It is never a good thing to resist change solely due to the inertia of current practice. But In this instance that is where I am at unless someone can greatly simplfy the mindboggling data splurged throughout this thread.

DB

[Shell Management]

Please be more patient sox.:=

It has taken some time to review all Shell operations, the company does fly over 80,000 hours a year.:cool:

It does appear that local regulataory restrictions, mainly in the UK (:ugh:) and other third world countries are delaying the adoption of PC2e.:{

However that is still 7/6.33 = 1.11, which is far better than any other oil company can manage. :)

As an aside, a maths lesson for VL;):
Industry accident rate / Shell initiatives = Shell accident rate.

One day we will hopefully get to 0.85!:D

[newfieboy]

Boys, just ignore SM, Ive been checking out the plank forum on pprune, because of interest in the QF incidents of late (cos me mother and sisters use on a monthly basis), your man is even offering his advice there ......:rolleyes: Wind up merchant = Loser......:ugh:

[squib66]

Wow, there is a big admission SM!

I wonder how far along Shell is actually along with implementing 7/7, 5 years after launching it.

Certainly at 80,000 hours pa the 2009 GOM accident has screwed the target of 1 fatal(?) accident per million hours (the 5 year and 10 year Shell avarages are at least 2.5 by my calculations). I also suspect a plataeu has been hit by Shell, just like SM keeps point out the airline industry has hit.

[sox6]

So another sham improvement from Shell Aircraft?

[HeliTester]

In response to Variable Load’s question…

So SM, back to the PC2e debate. How many of Shell's contractors are using PC2e offshore?

Please produce a list:
Bristow:
Caverton:
CHC:
Others:

I'm sure it will make interesting reading.

On 1st November Shell Management wrote…

It should be all, with the exception of certain aircraft like the Mil 8 and contracts that pre-date 2005, provided that appropriate procedures are in the RFM.

Shell OUs have invested massively in new machines partly, with more to come, for this heightened performance for PC1/PC2e and of course the improved certification standards.

I will verify and report back.
Anxiously awaiting Shell Management’s report.

[Shell Management]

I think I've made the postion clear.

It is regrettable that certain major improvements are being held up by amoral lobby by opeartors (you know who you are) and weak willed ignorant regulators (you probably don't know what safety is).

Still, the Netherlands is leading the way!

[HeliTester]

SM,

Do you really think those operators lobbying against PC2e are amoral? Do you totally discount the possibility that they sincerely believe PC2e might result in an overall reduction in safety due to the reasons stated earlier in this thread? If so, I suggest that you should be lobbying not for PC2e, but for PC1. PC1 requires the use of Category A Certified procedures, procedures that are substantiated by flight test rather than computer modeling.

HT

[Shell Management]

There was a consultation on the NPA. The operators accepted it then. Now they want to bring out various sprious arguments. If not amoral - what? Incompetance? Lazyness?

The lack of response confirms what I contended about the lazy response last year.

The lack of an answer just confirms the lack of proactive culture.

[HeliTester]

There was a consultation on the NPA. The operators accepted it then. Now they want to bring out various sprious arguments. If not amoral - what? Incompetance? Lazyness?
Incompetence? Laziness?.......WOW! I note that more than 10% of the words in the above quote are misspelled!

Sorry for the cheap shot, but I just couldn’t resist.

[helmet fire]

Hi guys,
Am tracking down information on Category PC2 with exposure. In particular, which helicopter models are capable/certified? If that is the right term.

It appears as though it will become a requirement in Australia within the next 2 to 5 years, and I understand EASA has been using it for some time. I guess JimL will be all over it!

[Jet Ranger]

I think, B412, BK117, EC135, EC145, EC155, AW139, Bell 429, S76C+, EC225, ...generally all twins in last 20 years can operate PC2...(I m not sure for Bell 427:{)

Also, some of them operate PC1.

[Shell Management]

Onshore maybe. The question relates to their operation from elevated offshore helidecks. This is a special case due to deck impacts and lack of safe rejection area.

[Jet Ranger]

Hmmm, OK.

btw. I forgot to mention, AW109E

[HeliTester]

PC2e was a hot topic back in 2010 (there were 87 posts). Not so hot in 2011 (there were 4 posts). Implementation was originally targeted for 1 January 2010. Anyone know what the current status is?

[Variable Load]

Here's my personal precis:

Eurocopter decided they couldn't compete commercially with the requirements associated with PC2e.
They lobbied the N Sea operators.
The N Sea operators danced to their tune and seem to have collectively killed off the requirement.

So it looks like we're heading down a route called PC2d - defined exposure. So no safety improvement, just a defined period where the crew will not know what to do (do we ditch or do we fly away?) and lives could be lost.

[212man]

Good precis! Maybe someone should tell Michael O'Leary about the concept - imagine all those small regional airports he could use with a few seconds of exposure before and after V1!!

[HeliTester]

Variable Load, thanks for the update.

Does anyone know if EASA is in the process of removing the PC2e language from the regulation and replacing it with new PC2d language, and if so, what the interim operating rules are.

HT

[JimL]

The words are exactly the same - they always were objective and, therefore, flexible.

Jim

[HeliComparator]

VL, that is a valid point only if your world of possible dangerous outcomes is blinkered to the case of an engine failure during the few seconds of takeoff or landing when safe OEI flight is not assured - and even with PC2E there is no engine failure accountability except possibly for an idealised perfect offshore installation which unfortunately doesn't exist.

In the real world there are many more dangerous outcomes as demonstrated by the fact that engine failure during exposure time has never happened in the entire history of the N Sea, whilst we have found plenty of other ways to crash. If you take a look at overall safety, operating with low fuel states to achieve PC2e mass could result in an overall reduction in safety and that is why the UK operators (not EC) preferred not to implement PC2E. However PC 2DLE is a reasonable compromise that raises crew awareness of exposure and ensures that the aircraft are not operated with an unduly long exposure time.