Hard Core Category A?

[NickLappos]

The concept of complete protection from engine failure was discussed in a previous thread, lets kick it off here.

One side says that the engine is prone enough to failure that it is wise to design a helicopter that has complete coverage of its flight path so that engine failure can occur without probability of a mishap. Let's call this hover to hover or "full Cat A".

The other side says that a limited exposure where an engine failure can result in a hard landing is acceptable, as long as it can be shown that the probability of an engine failure in that exposure time is as slight as the other kinds of failures that can happen to a helicopter. Lets call that "limited exposure."

It is my belief that the ability of a helicopter to land on a small heliport or rig helideck with full Cat A will reduce payload substantially, so that the economics of the operation would be strongly impacted, and also that such full Cat A would not increase the actual safety of the operation, as long as limited exposure rules were applied.

It has been compared to jet airplanes, where full Cat A equivilents are had regularly. I contend that they are actually a special case, because the turbojets that are used to cruise at 30,000 feet have enormous thermodynamic power potential at low altitudes, so the Cat A is actually free to the design. Furthermore, if we asked that plane to take off full Cat A from a small airfield, we would then hear similar squawks from the designers.

I also contend that actual accident data for helicopters that have good enroute Cat A capabilities, but not full Cat A are subject to many more prevalent causes of accident, and we should spend the next dollar fixing those first. The money and economic damage wrought by full Cat A would actually reduce the safety of the operation, since the money that might have bought EGPWS and weather radar and TCAS and GPS precision approaches would be diverted to the engines instead.

Let the games begin!

[spinwing]

I tend to agree with Nick, ...problems occur when contract negiotions try to make a/c fly to their maximum payload possibilities not allowing for enough operational performance margins.....;)

[Shawn Coyle]

Great idea for discussion!
I'm in violent agreement with the 'limited exposure' concept.
We accept exposure to risk in helicopters in other areas that, on first glance, would take your breath away - this is on the quite reasonable point that it is actually a much lower risk than the other way of doing the job. Putting people onto tall power pylons is a good example - the risk from doing it by helicopter is far less than having the people climb up the pole.
To a certain extent, it's true for using helicopters to go to oil rigs.
We need to examine the engine failure rates and determine if the assumptions are still valid about rate of failure per 100,000 flight hour.
Can we also invoke the fixed wing single engine IFR / night logic? WIth the proper engine (read PT-6 for all intents and purposes) and the correct maintenance procedures, it's not accepted as being safer than twin piston light twins.
If we can show a substantial improvement in cost-effectiveness, then we need to explore it.
And anything to make it simpler to plan and fly such profiles is essential - trying to work out the parameters for Category A on some helicopters is enough to make John Kerry Republican...

[JimL]

This is an edited extract from that posted on the EC225 thread (JimL):

When the 1995 version of JAR-OPS 3 was written in the early 90s it was decided that it would have to be in compliance with ICAO Annex 6 Part III; this required (even for Operations in Performance Class 2) the provision of deck-edge clearance and (for operations in a hostile environment) flyaway; which in effect - for the North Sea - was a zero exposure regime; existing operations were grandfathered until 2010.

Around the time of the implementation date of 1995, the discussion on offshore performance was centred on how to show compliance with zero exposure. Informed wisdom at that time was that this could only be achieved with Category A helideck procedures (as one of the requirements was to show the 15’ deck edge clearance). However, such procedures that were in existence (very few at that time) could only provide limited approach/take-off directions with a minimum deck size of 2D (shortly after that Sikorsky provided a S76C+ procedure with a minimum deck size of 1.5D).

With this in mind, working groups extensively explored the problem and decide to concentrate on a solution based upon the concept of ‘exposure time’ - Exposure time. The actual period during which the performance of the helicopter with the critical power unit inoperative in still air does not guarantee a safe forced landing or the safe continuation of the flight. (See also definition of maximum permitted exposure time)

Maximum permitted exposure time. A period, determined on the basis of the power unit failure rate recorded for the helicopter's engine type, during which the probability of a power unit failure can be discountedNot wishing to bore you with safety targets and the compliance procedures, let’s just say that the ‘safety target’ was based around a limited window of exposure (measured in seconds) and a reliability rate based upon 1 failure per 100,000 flight hours.

212man has said that it is a shame that we cannot reproduce the performance of the ETOPS twins that are now the backbone of the transatlantic fleet. None of us would disagree with that but it must be understood that we have in our hands the most flexible aviation tool that has ever been produced and the provision of that flexibility comes at a cost. One of the costs of that (expensive provision of) flexibility is the longevity of equipment; whatever (operational) regulations are specified, they apply to the whole population of helicopters - older helicopters could be protected (grandfathered) but this cannot be to the detriment of newer craft which are by definition safer and more expensive but not necessarily more productive (see the previous discussion on the provision of the crashworthy floor for the EC225).

Another trade-off is the installed power to provide: adequate OEI power in the cruise; fuel consumption to ensure adequate payload/range; and power to eliminate/reduce the exposure to an engine failure on take-off or landing. You will already know that provision of these conflicting features (simplistically) is a trade off between the last two - fuel burn and take-off /landing performance (the AB139 argument put forward by Nick).

Discussions in the JAA over the last couple of years have been concerned with what to do in 2010 when the exposure time concept is due to end. Perceived wisdom now has it that there may be a method of providing zero exposure without reverting to Category A procedures. It would appear that, at least for the later versions of the AS332, B412, S76, EC225, S92 and of course the AB139, zero exposure is possible with the provision of risk assessed take-off and landing procedures giving deck-edge clearance and, for those helidecks that are situated in a hostile environment, a limitation on drop down to avoid ditching. It has been observed that such performance is possible even in ISA nil wind conditions.

Using the inherent environmental conditions that obtain in the North Sea which appear to indicate that:the mean wind is in excess of 20kts;

the mean deck height is just below 100ft;

the mean temperature is 10ºC;

the mean pressure is 1011; and

a mean density altitude of -536ft.it can be shown that zero exposure is possible for most of the time without any payload penalty. Because the defining parameter for take-off mass with helideck performance is drop down, for operational theatres with a non-hostile environment (GOM) this does not (have to) come into play and take-off masses can also be slightly higher than they would have been.

As was indicated in a previous post, the provision of regulations is not the bottom line; some customers have a duty of care that extends well beyond compliance with regulations. It has become increasingly clear that ‘standards’ are within the bailiwick of the customer and not the operator; it is those customers who will specify whether the certification, performance, operational equipment and staff training standards are adequate and, with the exception of certification, will ensure that they are raised if they are not!

[JimL]

This is not an attempt to turn this into an academic exercise but, as with all philosophical discussions, we need to ensure that we use a common vocabulary so that we can all map to the same mental pictures. Terms that are in common usage have therefore been reproduced - first the definition of Category A:(JAA) Category A, with respect to rotorcraft, means a multi-engined rotorcraft designed with engine and system isolation features specified in JAR–27 / JAR–29 and capable of operations using take-off and landing data scheduled under a critical engine failure concept which assures adequate designated surface area and adequate performance capability for continued safe flight or safe rejected take-off in the event of engine failure.

(FAA) Category A, with respect to transport category rotorcraft, means multiengine rotorcraft designed with engine and system isolation features specified in Part 29 and utilizing scheduled takeoff and landing operations under a critical engine failure concept which assures adequate designated surface area and adequate performance capability for continued safe flight in the event of engine failure.Text has been highlighted because it gives some clue to the different thinking between the FAA and (at least) the JAA. Whilst the FAA definition appears to encapsulate operations, the JAA one does not and is concerned only with certification. A generally held view is that the term 'Category A' is concerned only with certification - both airworthiness and performance - and does not provide the richness required to describe operations.

Nick is using imaginative and descriptive language that has already been encapsulated into definitions - the following are those contained in ICAO (amended to account for recent work):Performance Class 1 operations are those with performance such that, in the event of failure of the critical power unit, the helicopter is able to safely continue the flight to an appropriate landing area, unless the failure occurs prior to reaching the Take-Off Decision Point or after passing the Landing Decision Point in which cases the helicopter must be able to land within the take-off or landing area.

Performance Class 2 operations are those with performance such that, in the event of critical power unit failure, performance is available to enable the helicopter to safely continue the flight, except when the failure occurs early during the take-off manoeuvre or late in the landing manoeuvre, in which cases a forced landing may be required.

Performance Class 3 operations are those with performance such that, in the event of a power unit failure at any time during the flight, a forced landing will be required.You can therefore see that, in operational terms, Nick’s ‘Hard Core Category A’ or ‘full cat A’ is in fact operation in PC1 and his use of ‘limited exposure’ (hard landing) is encapsulated within the description of PC2. What have not been described in Nick’s post are operations with ‘exposure’ - as defined in a previous post - which (in the event of an engine failure at a critical time) will not result in a safe-forced-landing and will inevitably lead to a catastrophic outcome. One example of this would be a deck-edge strike in offshore operations - another could be ditching in a hostile environment.

When discussing take-off and landing procedures, analogies with fixed wing are not, in my view, very helpful as aeroplanes operate to runways where the obstacle environment is controlled; helicopters on the other hand can operate to locations which are analogous to runways covered in, and surrounded by, obstacles.

If you are beginning to infer from this that I am about to put a case against operations in PC2 or operations with exposure that is not correct The aim of this post was only to ensure that we can all group around the same concepts when discussing this extremely important subject.

[ATN]

Suppose it takes 1100 kw to fly 12 pax on 200 Nm at 5000 ft with 25 C OAT. Because of financial issues what has been done so far was to install 2 engines of say 700 kw each and it has been up to the regulatory agencies, operators and crews to design, implement and follow procedures and limitations to deal with this shortage of power on one engine.
Today nobody questions the necessity or redundant hydraulic, fuel and electric systems but we all agree - intellectually too - to operate underpowered helicopters.
IMO in the case above 2 engines of 1100 EACH should be installed so that the helo could hover on ONE engine under the above conditions. This is what a real twin engine is.
On the long term run the financial impact should not be that negative since the engines would be operated almost all the time far from their limits, thus increasing their reliability. Think about the numbers of engines changes worldwide because they work close to the limits.
Above all this safety issue would be settled once and for all.
The major oil companies make tremendous profits and through their aviation advisors they seem to have the final word on selecting the type of helicopter. So I think that they should be gently forced to accept the financial constraints for safer ops.

Cheers

ATN

[212man]

The down side ATN is that the engines run a long way off their design point and so are very thirsty; but hey, that's not my problem! With arriel 2C1s currently being changed at around 1200 hours in the 155 B due to failed power assurance checks, maybe you're point about reliability is valid. 820 C can't be a good T4 to run at all day long.

My concern expressed in the other thread is that having developed the concept of exposure time for the offshore environment, there is a move to allow it for onshore operations too, by both operators and at least one manufacturer (don't mention grandfathers!) and one assumes others too.

We are not talking about Cat A, per se, either; we are talking about Operational regulations as defined in Ops 3 and Annex 6, not the certification standards.

Nick makes a slightly misleading statement in suggesting exposure time is an area within which a hard landing may occur. It is actually an area where a catastrophic crash can occur! Quite legally. This is a fundamental difference; we are not talking about Class 2 criteria, we are proposing allowing large aircraft with members of the fare paying public to operate in a regulatory environment where if the aircraft loses an engine they will quite likely die.

Ignore the offshore oil industry, it's a slightly different case and in any event I genuinly feel that the exposure is very small and insignificant. Look at sheduled helicopter operations; Isles of Scillies S-61, Vancouver S-76, Macau and Hong Kong 76 and others too, no doubt. These have members of the public walking off thee street to travel on a commercial air transport airline. They check in, pass security, have departure lounges and the staff all look like airline staff. The pilots wear white shirts and bars and even ties.

One could forgive them for thinking that the regulations afford them the same protection that they enjoy when flying in a Saab 340 or Beech 1900, for instance (both many times cheaper than an EC-155 or S-76), but no that is not the case.

Instead, the manufacturer says to the regulator "look, it's too hard to do this and costs too much. Why don't we say that for 9 seconds during take off, if an engine fails, we have no idea what will happen to the aircraft and if there are hard immovable objects in the way, well that's just a statistical risk we can take based on creative use of past engine data failure." "oh, and by the way, can we ignore things like governor run downs as they're not really engine failures are they? Oh, and this is a new engine airframe combination, so we don't have a real data set, so guess what; the results are skewed!"

Great! That's progress! Performance is pretty marginal anyway without degrading it further.

I fully accept that the flexibility of this aircraft places it in many varied situations where the crew and other personnel (long lining, power line patrols, SAR etc) are in some risk. However they know that and accept it. What I disagree with is the idea that we can legislate the exposure concept for onshore commercial air transport with fee paying, ignorant (in the literal sense!) members of the public.

[MaxNg]

I agree totally with ATN and 212man.

The best fixes are usually the simplist, Bigger engines please:)

Right what's next

Hydraulics!

[gomex]

I have one question for everyone. Why must pilots in the gulf of Mexico fly twin engines equipment with a fuel requirement of destination plus 30 minutes, and not enough power to land on any rig or platform with one engine inopertive, and not enough fuel to go to the beach. Ditching in the water in not a normal procedure. So far no one has had to do this. The only aircraft that has the power to hover at gross wt with one engine , is the Bell 214ST, and it is a dinosaur. I vote to have more powerful engines.
Thanks for letting me get this off my chest.

[Steve76]

Nick said:
"and also that such full Cat A would not increase the actual safety of the operation, as long as limited exposure rules were applied."

Again, quite correct. Full Cat A availability is a only as good as the pilot on the end of the controls. You can have all the engines in the world but without the correct profile flown it is a waste of time. You still end up in the side of the rig, ocean or the side of the hospital in EMS.

More exposure to single engine operation in the training regime and education on correct approach and departure techniques would be many times more worthwhile.

An S76A can be flown at pretty much MAUW on a profile that will allow a single engine landing with no roll out on a rig or roof top. Take offs are another issue.

[peter manktelow]

Nick…you do know how to “stir the pot”……….but an excellent subject. I must agree that with a limited purse , one must prioritize what goodies one can buy. So I have no argument with you there.

HOWEVER , on the specific subject of engine failure at the rig , may I direct the issue to a helicopter’s ability to fly a profile that will allow a successful escape after the engine has quit. By successful , I mean survivable.

(Bear in mind that I am currently flying the A model 76 in the tropics.)

Now I am not as concerned with the landing phase. With good technique , even hot and nil wind , an engine failure on approach , holds less angst for me. It is the take off that worries me….and surprise surprise …. it is NOT the single engine performance that I want , it is TWIN performance ! WHY ?

I lost an engine on rotation from a rig many years ago. It was not a Sikorsky but the lesson was indelibly imprinted on my brain. We rotated at about 15 feet. Our event was witnessed by the rig radio operator. The PT6 (well that is a bit of a clue) spat half the turbine out the back , right on rotation. We did fly away but the radio operator verified what really scared the crap out a me... and that was that the tail rotor cleared the deck edge by inches. Now had I hit the deck edge with the T/R then OEI performance , or even Twin performance becomes academic….I am dead meat.

So that is what I mean by wanting TWIN PERFORMANCE. I want to be able to lift high enough so that if I do lose an engine at that critical point on rotation , I can clear the deck edge and either fly away or ditch.

I see that the C+ does have various profiles/performance graphs for drop down , fly away etc from an elevated helipad (ie helideck). I have not flown the C+ in traditional offshore oil operations so am very curious about the profiles that offshore C+ OPERATORS are using and their subsequent WAT limits. Are they equipped with the collective detent system that EAA has ?? etc etc

Finally , I would very much like to have 100% Cat A , but if I can’t ( for whatever reason) then give me twin engine performance AND a profile that allows me to escape that deck edge after an engine quits.

Great subject.

Peter :8

[200psi]

Nick

You make the point about turbojets having ample thermodynamic power at low altitudes as a result of their design requirement to be able cruise much higher. Can a similar design concept be applied to Helicopters. That is, designers set performance goals to the aircraft based on a cruise height eg 10,000 feet (no oxy) and say we want max OEI payload, maintain height (dont worry about using driftdown techniques), suffer only a 10% loss of TAS, full anti ice & heater on (I hate being cold). From this then surely the flow on effect would be helicopters with engines of similar power excess and thus "CAT A" for free.

The selling point could then be related to cruise safety, performance and comfort and "hey we can even land and takeoff on one engine but we will throw that in for free".

In the fixed wing (jet/turboprop) world you lose an engine and you usually still get to where you were going or end up back where you started, but with helicopters generally you dont as they lose so much cruise performance that an intermediate alternate is required, this is most felt in the medium twin market.

Anyway IMHO engine power is a bit like diet coke you can never have too much, nothing like being able to lift heavy things I say.

[peter manktelow]

I shud have read JimL's more thoroughly....agree agree agree


also like his following comment...

"It has become increasingly clear that ‘standards’ are within the bailiwick of the customer and not the operator"

and aint that the truth but also a double edged sword.

[heedm]

Well, it seems the technical information is all available. The operators that fly helicopters because their start and/or end points aren't runways, seem satisfied with the limited exposure argument. The operators that spend a significant amount of time in the hover seem to want the OEI performance.

That doesn't surprise me. However, in the end, helicopter design is not about what can be done or what is desired, but what can be sold. Regulations not conscience are the forebearer of safety, so until the regulations are in place, I doubt any operator is willing to pay the huge cost of providing this safety performance.

I think a helicopter company should design a twin that outperforms 412, 76, etc. in their typical roles, and has full envelope OEI. Before marketing this machine, the company should lobby all the regulatory boards and insurance companies to demand this. Then us poor operators would be left with no choice but to fly safe expensive machines.

Seriously though, I have no problem with a limited exposure argument as long as the mission can be flown as such. Use a very long line, a light helicopter, etc. I can't think of anyway of making SAR any safer since a higher hover means more time with a man on the hoist...injury more likely than an engine failure. Although we do try to give ourselves time to 'drop' the man, cut cable and fly away.

Matthew.

[JimL]

First in answer the question posed by Mars on the EC225 thread:

Within the extant JAR-OPS 3 (amendment 3 at 1st April 2004), approval to operate with exposure to an engine failure on take-off and landing lapses from 2010 and operation in Performance Class 1 (PC1) will be required. For a number of reasons (mainly concerned with the deck size and the helideck environment – both obstacle and wind related), it is not anticipated that operations in Performance Class 1 will be technically feasible or economically justifiable by that time (One Engine Inoperative (OEI), Hover Out of Ground Effect (HOGE) would be an acceptable method of compliance but this could result in a severe restriction on payload/range).

In view of this approaching deadline and the limitations discussed above, there is a need to produce a practical alternative to PC1 which will ensure that take-off/landing mass reflects: the procedure; deck-edge miss; and drop down. As accident/incident data indicates that the main hazard is collision with obstacles on the helideck due to human factors, a simple and reproducible but deterministic procedure is required. Such a procedure will require the calculation of the take-off/landing mass from information produced by manufacturers reflecting these elements. It is expected that manufacturers information will be derived from performance modelling/simulation using a model validated through limited flight testing. This alternative to PC1 for offshore operations might be termed Enhanced Performance Class 2 (PC2e).Peter Manktelow -
Now I am not as concerned with the landing phase. With good technique , even hot and nil wind , an engine failure on approach , holds less angst for me. It is the take off that worries me….and surprise surprise …. it is NOT the single engine performance that I want , it is TWIN performance !This subject, as a debate, was concluded some year ago and led to guidance that take-off from a helideck should only be undertaken with hover out of ground effect performance (all-engines-operating). It should be clear to all that as soon as the ground cushion is dissipated the aircraft will sink - all of us who have flown the early marks of the S76 in nil wind conditions will sympathise with your post.

It is a commonly held belief that we have more problems with power for take-off than for landing; performance modelling does not accord with this thinking and appears to indicate a greater power requirement for landing than for take-off. If one were to examine the masses for the S76C+ helideck Cat A take-off and landing, it would confirm the modelling results; however, this statement should be hedged around with qualifications as it results from an interpretation of JAR 29 that appeared to require that a single-engine landing should be possible on the helideck with a failure occurring at any stage in the approach. Perceived wisdom, confirmed by performance modelling, appears to confirm that providing Risk Assessed landing profiles are flown, the gap between take-off mass and landing mass can be narrowed. In partial answer to ‘gomex’s’ comment, such profiles are dependent upon a OEI flight back to a land base. I’m sure Nick will wish to comment on these thoughts.Heedm - I think a helicopter company should design a twin that outperforms 412, 76, etc. in their typical roles, and has full envelope OEI. Before marketing this machine, the company should lobby all the regulatory boards and insurance companies to demand this. Then us poor operators would be left with no choice but to fly safe expensive machines.Perhaps you might wish to follow the thread on the AB139, which appears to have this capability. With regard to your comment on lobbying, you will see that there is an attempt to describe the level playing field that you demand contained in the first two paragraphs of this post.Steve 76 - Full Cat A availability is a only as good as the pilot on the end of the controls. You can have all the engines in the world but without the correct profile flown it is a waste of time. You still end up in the side of the rig, ocean or the side of the hospital in EMS.None of us could have stated this better, if operational margins are to be limited to permit techniques which do provide engine failure accountability at an economically justifiable cost (be it PC1 or PC2e), the success of these techniques will be wholly dependent upon: (1) an understanding by the pilot of the risk profile of the technique; and (2) adherence by the pilot to that profile.Steve 76 - An S76A can be flown at pretty much MAUW on a profile that will allow a single engine landing with no roll out on a rig or roof top. Take offs are another issue.For the reasons discussed in the comment to Peter, this statement is not borne out by modelling or practical experience; whilst it may be possible to demonstrate this to a “landing square” that is drawn out on a runway, it is generally accepted by test pilots that this is not true when flying to an elevated heliport or helideck.

[alouette]

Can anybody provide details if the BO 105 is capable of performing CAT A perf. Class 1? responses welcome. Cheers:ok:

[Mars]

alouette:

It is difficult from your profile to know on what geographical basis you are asking this question but, if you are asking on a European basis, there are two questions you need to ask: Is the Bo105 certificated for Category A; and Does it have approved Category A procedures in its flight manualIn order to able to operate in Performance Class 1 (or PC2) the aircraft must be certificated in Category A. As the Bo105 was certificated before the advent of Appendix C of FAR 27, unless it has been certificated in accordance with UK CAA BCARs, it will need to be in the appropriate modification state (available from ECD) to be able to qualify for acceptance as Category A and be able to operate in PC1.

The answer to my second question and your only one; yes, it does have a number of approved Category A procedures.

[alouette]

To Mars:

Maybe I should have specified my question. It is more like is the BO 105 capable to operate in performance class 1 lets say at 35C OAT? Fire fighting? With HUMS installed, etc... Thanks:ok:

[Mars]

alouette:

That's a length of string question and I'm still not sure of your motives; why don't I attempt to answer the question that I think you are asking and we can continue from there.

The ability to perform any Category A procedure will be limited at some combination of density, payload, fuel etc. Depending on the procedure the limit will come sooner or later; the helipad procedure will limit earlier than the short field, will limit earlier than the clear area (runway).

Shawn referenced the case where it was safer putting a worker into a position with a helicopter than it was for him to climb up - this is sometimes called the 'Relative Safety Case'. However, it does depend upon the State of Operation whether that particular operation would be permitted with other than OEI OGE hover performance - it is likely in the UK that the higher performance standard would be required. Even though that particular operation is not within a Category A procedure it could be regarded as equivalent to PC1 as engine failure would have been accounted for.

Other Aerial Work tasks would not have the protection of such performance - the risk of engine failure is accepted in view of the fact that there is no exposure for passengers or third parties. Fire fighting comes into this category. There are no performance standard requirement for Aerial Work

I am not certain what you mean by HUMS but, for the purpose of this discussion let us assume that you mean engine monitoring such as that provided by Monitair or Altair (UMS). If all operations were to be in PC1, engine failure would have been accounted for and so there would be no need for engine monitoring. In the event that Commercial Air Transport (CAT) PC2 operations ‘with exposure’ were being contemplated, there might be a requirement depending upon the regulation - for example when operating in accordance with JAR-OPS 3.

If you genuinely do mean HUMS, it is likely that this would be a combination of UMS and vibration Health Monitoring (VHM) - which is only now coming over the horizon and is mainly being considered to address tail rotor failure issues.

In any event, it is unlikely that either of these pieces of equipment will add greatly to the weight of the Bo.

I am not a Bo105 expert and I’m sure that others can answer any specific question you have on Category A take-off masses - it is normal Flight Manual fare.

[NickLappos]

Take care with the simple question about Cat A or not Cat A. Every twin can have a full Cat A envelope, but for most, the reduced gross weight for the full Cat A means almost no payload. The real question is at what cost to payload/range/economics is full Cat A?

I will try to post some influence charts to illustrate the issue of payload vs landback distance and range vs OEI engine power, where it is the physics of the helo that cost the awesome price, not just lazy designers or cheap operators.

[JimL]

Nick,

I have no wish to contradict you but is that statement correct for the projected AB139 or the EC135 or the A109 Grand? The latest marks of these aircraft have close to OEI OGE hover performance at max weight - in temperate conditions and at lower altitudes. Isn't it correct that OEI OGE hover performance is far in excess of any Category A requirement, as reject distances are not required to be calculated. Granted that the ability to clear obstacles OEI is not, and never will be, as good as fixed wing but that is a burden that we have to carry for the flexibility of our chosen craft.

Isn't it correct that it is extremely unusual for the AS332L2 and the S76C+ not to be able to depart from the UK and Norway to the North Sea fields whilst operating in PC1 at MTOM (using the published Category A procedure)?

[Eurobolkow]

Jim L and Nick:

I think both of you are correct. Many of the older twins do have Cat A performance but at such a reduced gross weight as to make them useless for an operation. Some of the latest generation twins do have decent Cat A performance up to and including operations at max gross weight, the A109E for example has full Helipad CAT A Class 1 at MGW (ISA) up to 750m elevated.

As for the 76C+ and AS332L2 I will have to leave that to the EC and Sikorsky experts to reply but I would also be interested in knowing what the performance of the 135 and 92 are like?

[Hilico]

I spoke to an Essex HEMS pilot (EC135) who said he 'didn't need the second engine' below about 2600kg. Judging by the speed of his (twin-engined) departure, he was correct.

[Gomer Pylot]

Gomex, I don't know about every operator, but those I do know about allow one-way fuel with twins for only those models that can demonstrate landing on a rig OEI. For instance, most don't allow it with the S76A, but do with the A++, because the A++ can land successfully OEI, at least under most conditions, and we practice it, albeit on land, to a marked landing area. It's the same for the 412. They can't hover OEI, but landing doesn't require hover power if you're careful.

The problem with having enough power to hover OEI is that operators, driven mostly by customers, always want to carry more payload, so they harry the manufacturers until the max gross weight is increased, and eventually you're back on the ragged edge again. This happened with both the S76 and the 412, and will likely happen with everything else, unless regulations entirely prevent it.

I'm comfortable with not having enough power to hover OEI OGE. To me, that's overkill, and results in reduced range because of fuel consumption. IMO, the chances of having an engine failure at exactly the wrong time on takeoff are much smaller than the chances of finding my destination below landing minimums, and my needing more fuel than I anticipated. Regardless of how much power the engines are designed to produce, I know of none that produce much power using air as fuel. I'll take greater range over excess power any day.

[JimL]

Gomer Pylot,

No-one was suggesting a OEI HOGE requirement - it was only being used to show that some aircraft already have that capability and could therefore achieve PC1 at max weight; mainly to counter Nick's contention that PC1 was not possible with reasonable payloads. Having it as a requirement was not being suggested - as you will have seen from my first post.

ICAO and European regulations permit one way fuel (or rather offshore alternates) but only on the basis of an OEI HIGE landing capability - and only when the weather is at or above certain limits. The safety case is based upon a series of checks at PNR which establish, by contact with the rig, that the weather is above limits - PNR must be within 30 minutes of the rig thus reducing the probability of a weather deterioration.

When you indicate that you have the ability to land on the rig can we assume that you do not even have the OEI HIGE capability? Exactly how do you work out your landing mass to achieve this?

Your last statement makes me feel quite uncomfortable; if you are only carrying one-way-fuel and there is a chance of finding your destination below landing limits what exactly is your escape strategy based upon? If the weather in the GOM is like most offshore patches, don't the rigs all sit in the same weather pattern - unless there is a known and clearly defined front?

Notwithstanding all of this, PC2 could provide deck-edge clearance and a landing profile that retains all options until a decision point. The problem is that the drop down for most aircraft will be more than the height of the rigs in the GOM; on the plus side, ditching and surviving in the GOM is less of a problem than it would be in the North Sea or North Atlantic and does fall within the definition of a safe-forced-landing.

[Gomer Pylot]

Is there an echo in here? ;)

Basically, we don't even bother to work out the landing mass. We just go with the necessary fuel, and accept the landing weight we get after an hour or two of burning fuel. At sea level, and 600+ lb under gross, it's possible to put it on a legally-sized deck, but I would never try to hover at that weight, especially in the summer. Our technique is to land, not hover, and there is no legal requirement to be able to do so. We do work out a PNR, but there is no requirement that it be within 30 minutes of the destination or alternate. We must carry enough fuel to get to the destination, and then to another place we can land, plus reserve, even VFR, just in case of a fouled deck.

The GOM, at least the part that has oil & gas production, is more than 300 miles across, so it's not uncommon to have greatly different weather between the east and west ends, and it's not at all rare to have some areas fogged in and others completely clear. But if you're flying something with very short legs, like a 412, you probably can't get out of the current weather pattern. That's why I like more speed and range.

If I go IFR, I carry enough fuel to be legal - in the US, destination + alternate + 30 minutes. If I can, I prefer more than that, because that isn't enough to make me comfortable. Thus, I prefer more range to more power. I will not go short on fuel, under any circumstances. Running out of fuel means you ran out of employment, not to mention the other hazards. But bigger engines always mean more fuel burn, and reduced range. I prefer more range, thus more options, within reason of course. YMMV.

[NickLappos]

JimL,

Some experience in this stuff has lead me to believe that zero exposure landback distance (or the deck-to-tail clearance distance), is driven by the OEI power ratio, where the machine has to have enough engine power to be somewhere between IGE and OGE while OEI. (love those acronyms!)

The takeoff is always the tough part, requiring the most power ratio, as the aircraft is crawling up from a zero speed, zero altitude energy well. The landing is much easier, because the kinetic energy and potential energy both provide equivilent power to lend a helping hand.

Rotor inertia is a nice contributer, too.

I have some influence plots to illustrate this on my other computer, and will try to post a tome on it in a bit.

SFC, excess Power ratio, engine and transmission weights, and cruise fuel burn conspire to make us limit the OEI performance. There are ways to make it different, but they will wait until engine technology creates the true "burnout rating."

Gomer has my vote, gas, and the range/time that it brings, are much more important to flight safety than OEI engine.

[peter manktelow]

NICK says "Gomer has my vote, gas, and the range/time that it brings, are much more important to flight safety than OEI engine."

That subject could easily be the start of a new thread. Being in the tropics right now , the IFR/IMC side of the operation is almost non existent but in the northern winter areas...IFR is almost every day and the fuel issue is critical.

The issue is not the outbound leg , after all , if we arrive at the rig and can't get in , then we miss back to shore....easy peasy. It is when we get back to shore with a lot less fuel (depending on your particular government authority's fuel reserves) that we start to squirm

In my experience world wide , there is rarely a shore destination ( on the inbound leg) that has an IFR alternate within reasonable range. Unlike our fixed wing cousins who can nominate , for example ,destination Hong Kong with alternate Beijing...we are stuck.

That leaves us with either NO ALTERNATE approval for destination which will be weather related OR the capability and approval to flydown to lower minima as for example Cougar who have ILS 100' DH and 600 RVR (600 feet) ....oh , how nice it was to have the capability inherent in the SPZ 7000/7600 AFCS even if it was not legally available to me below 200'.

Regarding the OEI....
I gues what Nick and JimL are saying to me is that it is time to get out of my old A model and in to something with a bit more ooomph.
$$$$$$$$$$$$$$$!!!!!!!!!!!!

Peter :8

Nick...a question.

When establishing initial HOGE graphs on a helicopter , is the aircraft lifted up from the ground to a HOGE hover OR is the out of ground effect hover arrived at after a transition and descent from forward flight ?


Or is there some other method for ariving at HOGE figures

Peter :8

[tecpilot]

@alouette&mars

Only the last BO105 version the CB/CBS 5 is approved to use "special operations". The FM describes only under section 11 supplement 11-4 "Special takeoff and landing operations" some procedures.
That's the "Super Five" BO 105 version (CB/CBS5) with the new designed rotorblades and the newer main gearbox.

"Although the BO-105 helicopter is certified basically for operation according to FAR 27 this supplement provides standardized takeoff and landing procedures and performance data which are certified according to JAR PART 29, Second Draft, Category A operations.
This supplement only applies to helicopters having main transmission ZF FS72E (Retrofit kit, P/N 105-80037) installed.
...

...
C.2.1 CERTIFICATION CRITERIA
The emergency and normal procedures apply to:
– restricted helipads having dimensions of at least 15 x 15 meters under day and night
conditions, and
– elevated helipads having dimensions of at least 20 x 20 meters under day conditions
only.
NOTE Operation on elevated helipads smaller than 20 x 20 m but not less than 15 x
15 m, need individual approval by the respective authorities.
...

...
MASS LIMITS (example)
For maximum takeoff and landing gross mass refer to Fig. C1.
EXAMPLE: (see Fig. C1)
Determine: Max takeoff and landing gross mass, wind calm
Known: OAT 15 °C
Pressure altitude SL
Wind Calm
Solution: 1. Enter chart at known OAT (15 °C).
2. Move vertically up to known pressure altitude (SL).
3. Move horizontally right and read gross mass = 2262 kg."

It means, that under general HEMS conditions (3-4 persons+mission equipment) as example, the fuel load must be reduced to approx. 50-60 min flight time incl. all kinds of safety fuel! Mission time could be not more than round about 30min.

AND:

The ENGINE AND TRANSMISSION POWER LIMITATIONS limited the OEI TOT of the remaining engine to 810°C. Any BO-105 pilot knows the "normal" high TOT's. I say, under OAT's greater than 15°C thats the really limiting factor.

[NRDK]

Hard core CAT A is fine for all that easy safe rig flying stuff, with hundreds of CAA/FAA & company rules to safe-guard you. But what we are talking about here is who (EC225 or S92) is going to give me a HARD-CORE SAR machine. The sort of helo that will take me at max weight, hovering over the back end of some boat at night in a calm wind and safely be able to winch people without a ditching or a ‘run and cable cut’ when a donk stops. Or up the side of some mountain, ‘heavy’ & winching safe in the knowledge that nobody is going to get FUBAR when we become a ‘single’ again. Power in the hand in worth a twin in the bush! Come on EC & Sikorsky, meet the real challenge.

[Mars]

Nick:

Could be our confusion is based upon a previous statement made when this subject was aired on an earlier thread:The next generation of helos will meet JAR Ops 3, which will get them much closer to max gross weight with helideck Cat A capability. The S-92 will perform a Cat A takeoff from an elevated helideck with a full passenger load and at zero wind at 35 degrees C with enough gas to fly about 300 NM with IFR reserves.Can we assume that this remains correct and has been confirmed during flight testing? If so it would appear to meet the GOM profile and, as pointed out in JimL's post:Using the inherent environmental conditions that obtain in the North Sea which appear to indicate that:

the mean wind is in excess of 20kts;

the mean deck height is just below 100ft;

the mean temperature is 10ºC;

the mean pressure is 1011; and

a mean density altitude of -536ft.confirms that PC1 (or at least PC2e) is well within the scope of the S92 for the North Sea under almost all conditions. That appears to be good news; as we already know that the S76C+ has a similar profile and the AB139 is even better, what we now need to establish is if the same could be achieved by the EC225 - HC, any thoughts on that?

Because this performance is based upon the offshore configuration and the engines are already specified, Gomer Pylot and GOMEX no longer have to make the choice of range v performance, the choice has been made for them.

[JimL]

Gomer,

May I have another question - we are all aware that FAR 135.183(d) does not require you to work out your en-route performance (as you are carrying emergency floats), and as I know, from experience, that the early marks of the S76 start to gross out at about 20ºC, can we assume that you also do not work out a take-off weight that gives stay-up in the case of an engine-failure - i.e. you are operating in PC3 not PC2.

(In answer to ‘gomex’s’ earlier comment, there was a Bo105 that ditched in the GOM after losing one engine - round about January last year.)

[FLI]

Most light twins are bought by wealthy individuals or corporations. The owners step out of their BBJ, G550, etc and into an EC155, SK76, etc to take them home. Do you think that they would find “limited exposure” comforting? They think that they have bought or hired a twin engine helicopter in the same performance category as their jet and at no time will they be exposed to danger in the event of an engine failing.

Those with experience of the types that I have mentioned know that, short of operating from an airfield, the OEI will just take them to a difficult landing spot if the surface isn’t anything other than a smooth grass field.

In the real world of onshore commercial or private corporate operations those types of T/O and Ldg sites are very rare.

The Manufacturers have relied too long on the pilots keeping quiet on the weak performance of their helicopters. We need our jobs and we want our customers to fly so we do the best that we can with the equipment available. Eurocopter’s 155 can not get airborne on 2 engines at gross weight at +30 GPA! The OEI situation is fingers crossed!

Sikorsky’s answer to the weak performance of the 76A was to devise complicated and uncomfortable profiles that scared the passengers. The full Group A T/O profile requires nearly 1000 metres of firm clear surface? Where does one get that in Europe? The GPA Vertical reduced the payload by 1200lbs and still required 450 feet of clear firm landing space. The 76B’s performance was a vast improvement but then they produced the C. That was somewhere between the A and B in performance terms. What progress!

The regulatory authorities in the UK have not given special easements for helicopter GPA operations. They regard GPA helicopter operations in the same way as GPA fixed wing (light underside damage, no injuries to pax and no danger to third parties). Where possible, operators fly to GPA (restricted) to enable more realistic operations.

Some twin engine helicopters will ditch on the Thames if OEI occurs shortly after TO from Battersea Heliport. We brief passengers on emergency actions and life jackets but they assume that a twin will continue to fly away OEI. That is, after all, why they bought/hired one. Regulations do not require us to tell them otherwise.

When will the manufactures provide twins with OEI fly away at any time, at gross weight and at realistic temperatures for many parts of the world?

For too long manufactures have been producing and selling helicopters under the Cat A/ Group A category that are applicable to airfield operations only.

[NickLappos]

Mars,

I guess the answer is this:

I don't post these thoughts with an agenda. The idea of what is necessary is not tied to what products anyone is producing right now. Please do not take my posts on this thread, or any other, as having motivation in promotion of products. These are my thoughts, not tied to any company or product.

Specifically, the S-92 is quite capable of rig Cat A as I have previously posted (and you have reposted, thanks). The S-92 might be the best so far out there, but that doesn't mean that I should pound that as an advantage if I don't think it is. I still think hard Cat A from rigs is less necessary that many other safety features that can be added for less penalty, and much more bang for the buck.


I think I also disagree with FLI, because I don't think the manufacturers hide their performance. He blames manufacturers when he says, "For too long manufactures have been producing and selling helicopters under the Cat A/ Group A category that are applicable to airfield operations only."

FLI says,"We brief passengers on emergency actions and life jackets but they assume that a twin will continue to fly away OEI."

Sounds like your briefing needs a bit more fact, and less fluff, FLI!

[Gomer Pylot]

Jim, there aren't many S76A models left. I don't know what those operators do. With the A++, stayup isn't a huge problem, especially when flown from an airport. In most (not all, unfortunately) Gulf Coast bases, there is lots of flat, open ground for takeoff. Operating from the few places that have cranes, boats, towers, etc in the way, than loads may have to be reduced. PC1, 2, or 3 isn't even mentioned in the FARs, AFAIK.

I have to agree with Nick, in that if money is going to be spent, it needs to be spent on other things that are more important, like communications, radar coverage, weather reporting, EGPWS, TCAS, etc. If you look at the reports, more people have been killed in midair collisions than in accidents caused by engine failure in twins, by a huge margin. More people have been killed flying in bad weather, by a wide margin. When we go out, we go without current weather reports, without radar coverage, and without ATC radio communications, in many cases. I regularly file and fly IFR without a weather report at the destination, with no communications with the rig, and with no assurance that we will maintain communications with ATC. Radar coverage is lost about 50 miles from the beach. All hope of the government funding anything was lost in Bush's tax cut. The oil and helicopter companies could fund these, but that would cut their profits by perhaps a percent, at least in the case of the smaller companies.

I'll always take more power and more reliability, but that's not what is killing people. I prefer to spend money correcting the things that are killing us.

[helmet fire]

Great thread.

I also agree with Nick & Gomer - spend money where it will save the most lives - reducing CFIT. I think the current twin engine balance is close to being correct: the manufacturers produce PC1 capable aircraft that can have the payload and fuel load increased to make into a PC2 or even PC3 (ie AS355F1!). Then it is purely up to the operator/customer to decide upon their own acceptable level of risk exposure. In this I totally disagree with FLI. It should NOT be up to the manufacturer to economically restrict some operations by only creating aircraft with full PC1 at all times.

It is simple: operate to the appropriate risk exposure you are willing to accept AND pay for. If that means you have 5 people to transport with PC1 risk, then you will have to get out of your AS355 and pay for a 412. If you have 13 people for a PC1 op, then get out of your 412 and into the 332. Because if we all wanted to have MORE range, MORE payload, MORE power it is going to cost MORE money, and the operators who can accept exposure become economically unviable.

I would argue then, that we already have the right balance. If you want PC1, fly with the published weights, and if you can accept more exposure (during a sling load, or clear area take off) then you can take more weight and increase the flexibility of the machine.

Sorry, a PS:

Nick, I know you are probably sick of additions to the question about what pilots want in their next helicopter, but here is one that may fit nicely into this thread - a fuel dump. I have operated with one on the Black Hawk and I thought it was the bees knees. A quick flick of the switch and you are jettisoning 836lbs/min!! We even amended the emergency checklist for OEI emergencies to include this action as Sikorsky hadn\'t. What a wonderful tool - and I wonder what impact it would have on the issues raised in this thread?

It would not help your tail-to-side issues of Pete M, but it would really help in your flyaway! Imagine it fitted to the less PC1 capable twins like the AS355, B212, BK117, etc. Flick that baby on and try to miss the ground for the next 30 secs - minute or so, and viola 400 KG closer to PC1. Arrive OEI overhead your landing area, and flick that switch so you can avoid endless circuits waiting for your weight to become acceptable. Messed up your drift down height and need another thousand feet? Flick it on to get lighter!

PS: I should explain to that the suck pipe of the fuel dump does not go to the bottom of the fuel tank, but is cut off several inches above the bottom so that if you do forget and leave it activated, the worse case scenario it can leave you with is 20 mins fuel remaining. Obviously not a consideration at your take off and landing point - but quite critical if you do it enroute over water or tiger country

[NickLappos]

helmet fire,

I agree, the fuel dump we put in Army helos is impressive, but usually the absolute limiting factor for the Cat A takeoff is the initial dip, which occurs too soon to allow appreciable weight relief with the dump. Dump is great for landing, however!
Most fuel dumps have over 100GPM pumps, so the weight reduction is about 1000 lbs per miunte. The dump system does weigh about 60 to 75 lbs if I recall correctly.

helmet fire, you infer an interesting point - I know of no military service that has any equivilent of full Cat A, in any mission, mostly because the statistics simply do not support the very slight gain in safety vs the loss in operational capability.

The US Army's experience with the GE T700/CT7 engine family is very impressive: the failure rate is 1 engine failure per 500,000 hours of engine operation for engine cause, and 1:200000 for all causes (mostly pilot/fuel issues.) At 1:200,000 hours, that means a 500 aircraft civil fleet flying 1,000 hours per year per aircraft would experience 5 engine failures per year total, and 2 that were the engine's fault. If the average mission is 1 hour long, and there was an 8 second exposure time on takeoff, and a 5 second one on landing (13 seconds out of 3600) then the fleet spends 0.36% of its life in the exposure zone. This infers an engine failure every 55 years inside the exposure time!

If we launched that civil fleet, and let it just fly at today's accident rates, it would reduce itself by about 2% per year, due to accidents, so that by the 55th year, there would only be 175 aircraft left to have that failure, (500 x .98 done 55 times!)showing the problem with designing for full Cat A - your are fixing the problem you want to fix, not the problems that get you.

BTW, the concept of full Cat A would virtually eliminate civil tilt rotor operations, because the design tradeoffs for tilt rotors require engines that are 40% larger than helicopters (for the same payload) while the TR inefficiency in low speed makes those bigger engines barely able to produce today's airport type Cat A distances.

[JimL]

With such a complex subject it is often useful to remove a number of elements that are not germane to the discussion. One of these is the introduction of the alternative spend argument.

We took this discussion from the EC225 thread which was based on an offshore scenario; why? For the obvious reason that both types will logically follow their predecessors into the oil support market - particularly (as stated before) as most of the remaining large reserves of offshore oil are contained in ‘deep water’ regions (that this will be an Achilles heel for the AB139 with its relatively short legs will be something that AgustaWestland may have to address in the near future).

As Gomer has pointed out in one of his posts (without considering these deep water territories), at least one offshore domain is subject to a number of hazards that others are not; this includes but is not limited to: uncontrolled airspace; bad or no weather reporting; a lack of ATC coverage.

If it considered that the risk of accidents, resulting from one or more of the above, is beyond the safety target set by the State (supposing there is one) it should result in a requirement for mitigating procedures or equipment to reduce the exposure. Whilst several of these (may) require infrastructure spending, it is likely that existing programs will assist in the reduction of some of these hazards.

One hazard - a combination of one or more of the above - is controlled flight into water. After a particularly nasty accident in the UK, it became a requirement to fit a radio altimeter with AVAD on offshore helicopters. There have been several posts that have extolled the virtues of EGPWS - of which I am a great supporter. However, when operating offshore, it is quite clear where the level of the surface is, and fixed platforms are mapped and of limited physical dimensions. However, unlike most onshore areas, we do have a number of transient obstacles that can range up to 500ft in height. EGPWS will not know about these transient obstacles and will not be as effective as one solution that has been used in the North Sea for decades - the RADALT, AVAD and weather RADAR. The introduction of geostationary satellites and differential GPS using WAAS will improve the effectiveness of that equipment.

I submit that the existing solution is cheaper than, and just as effective as, the more expensive one (which would not be true for onshore CFIT). (It could also be argued that controlled flight into water is not the true reason for a number of the accidents seen, but a loss of control resulting from inappropriate but inadvertent entry into cloud.)

Similarly for congested but uncontrolled airspace (both VFR and IFR); airborne collision and avoidance systems (I hesitate to use the acronym ACAS as it brings to mind specific solutions) might provide the protection we need for what is in effect ‘free flight’ in offshore domains. If the provision of this solution also includes the reading of automatic weather stations (both by the onshore base and whilst flying offshore) it will bring added value to the solution. CAPSTONE appears to provide one such solution.

I would also contend that the provision of landing aids that have been produced for onshore runway use are also inappropriate as they will not have taken into account the fact that the go-around must miss the largest obstacle in the area - the rig that you are attempting to land on. Present ARAs using RADALT and airborne radar but improved with the use of differential GPS will continue to provide the best solution for offshore approaches.

Equally, the use of offshore alternates v return-to-land-base-fuel must be the result of addressing the combined problem of offshore weather and the lack of single-engine landing performance to a rig. If the oil company decides (and the Authority accepts) that a non-assured emergency landing onto a rig could (to some mathematically defined probability) result in a more serious and catastrophic event, ditching is the preferable option (once again with a clearly defined risk of escape and survival governed by probability and consequence).

The point that I am attempting to make is that all of these technologies and procedures mitigate specific hazards which have to be addressed in their own right - if they result in an unacceptable accident rate. What is not, and must not be advocated, is the introduction of an additional hazard to mitigate the cost of providing other solutions.

Let's continue with the discussion of the provision of appropriate performance standards.

[Mars]

Nick:

I'm sure none of us are without motive; that would be too much to ask and probably boring to boot.

Thanks for the reply and the confirmation - the reason that I raised the quotation and asked the question is that the theme of your post appeared to be taking us away from something we already have - zero exposure to a helideck strike with the majority of modern aircraft in, and about to enter, service. Your figures show that this is even possible for the S92 in the conditions that are present in the Gulf of Mexico.

However, we also know that, for any elevated procedure which has a short vertical section (a TDP of 20’ - 30’) and which relies upon rotor inertia and a 30 second power to achieve deck-edge clearance, there will be a (potential) penalty in drop down; we also know that drop down can be reduced by a favourable density altitude and wind accountability - examination of the S76C+ Category A procedure will confirm this. Drop down is not a bad thing as helidecks are elevated and (in the North Sea) appear to have a mean height of 100’ and are exposed to a mean wind of 20kts.

Onshore elevated heliports and ground level helipads are subject to different conditions but could have the luxury of space to have a back-up procedure, or longer vertical sections which could be traded for drop down.

How can the manufacturers be accused of hiding performance, don’t they publish the Category A procedure; isn’t it more that the operators, pilots and regulators are not capable of asking the correct questions and appear to be satisfied by a statement that the aircraft is Certificated to Category A. Not even FAR 29 requires more - strange then that an interpretation of FAR 29.1(e) appeared to indicate that a Transport Category helicopter should be operated only in Category A - hence the HV graph being in the limitations section (and the lack of performance rules in the current FAR 91 or 135). Are we missing something here, isn’t the class of helicopter that is above 20,000lbs and carries more than 10 passengers mostly used in offshore operations.

For me, and for the reasons that you have stated in your statistical analysis (the calculations look familiar), I am content with PC2 with exposure for offshore operations; but for those States and customers who need to have more assurance built in to their operations (for example when operating in a hostile environment), PC2e appears to give the best of both worlds - zero exposure without the expense of flight trials in the Moray Firth. Looks like a win-win situation to me.

[NickLappos]

Mars,

The true zero exposure pc1 can be provided, at reduced gross weight, and very reduced payload, of course, and will be for those who want it, I am sure.

I believe the "hostile environment" has no play in the use of pc2e, as the probabilities of the need for exposure are so small they are negligable, and the exposure we are describing has a very small, but measurable window inside that exposure window where the failure could result in a very hard deck landing, or a clipped strike on the rig and a fall down the side. Recall that the full window is a once per 55 year event for our hypothetical 500 aircraft fleet, while we lose a much more vast number to more common, and more preventable causes.


JimL,

That EGPWS that I always harp on is actually a multi-talented device of great use in offshore, much more so than the common radar altitude (Radalt has been aboard every cfit accident aircraft I have ever investigated, BTW). The EGPWS protects against descent after takeoff, tail low on landing and about 30 other classic helicopter problems, as well as it warns if you are about to hit something. Those roving, random 500 foot obstructions are quite a nuisence, still, but actually can be manually inputted into EGPWS at the Ops Room prior to flight.

[FLI]

Nick says
-----------------------------------------------------------------------------------
The US Army's experience with the GE T700/CT7 engine family is very impressive: the failure rate is 1 engine failure per 500,000 hours of engine operation for engine cause, and 1:200000 for all causes (mostly pilot/fuel issues.) At 1:200,000 hours, that means a 500 aircraft civil fleet flying 1,000 hours per year per aircraft would experience 5 engine failures per year total, and 2 that were the engine's fault. If the average mission is 1 hour long, and there was an 8 second exposure time on takeoff, and a 5 second one on landing (13 seconds out of 3600) then the fleet spends 0.36% of its life in the exposure zone. This infers an engine failure every 55 years inside the exposure time!
-----------------------------------------------------------------------------------

Am I correct to assume that an engine is more prone to failure when operating at very high power demands? Like during T/O, Ldg and hovering? On some twins the T/O Cat A profile requires 100% torque. What are the statistics for engine failure at max power? The thread was, after all, about take off and landing performance.

The Cat A profiles also require an engine to be able to produce it’s published power. How many engine changes has the Sikorsky 76C+ fleet had because of failure to meet the PPI?

My point is the engines on a lot of twins are operating very close to their design limits. Would it not make sense to have some margin in these engines in order that they are not at max chat at every take off? That margin could then be used to reduce the exposure time and reject distance in the event of OEI. I know we have OEI 30 sec and 2.5 min limits but utilizing these margins, on some twins, still requires 100’s of meters of flat unobstructed reject area and a replacement of the good engine if it all works out.


Helmut fire says

-----------------------------------------------------------------------------------
It is simple: operate to the appropriate risk exposure you are willing to accept AND pay for. If that means you have 5 people to transport with PC1 risk, then you will have to get out of your AS355 and pay for a 412. If you have 13 people for a PC1 op, then get out of your 412 and into the 332
-----------------------------------------------------------------------------------

Most light twin helicopters were designed to carry 12 pax. In the Corporate role most of these helicopters are fitted for just 6 pax. And still we struggle to get airborne and fly 250 miles. We don’t struggle from airfields but from the operating sites. Yes, I know, we can get rid of the leather, the bar, the A/C and all the other luxuries but the boss likes them!
And the Helicopter Manufacturers like selling them!


Mars says:

-----------------------------------------------------------------------------------
How can the manufacturers be accused of hiding performance, don’t they publish the Category A procedure; isn’t it more that the operators, pilots and regulators are not capable of asking the correct questions and appear to be satisfied by a statement that the aircraft is Certificated to Category A.
-----------------------------------------------------------------------------------

I did not say that they hide their performance figures. The words "Category A" sell helicopters that have insufficient performance for a lot of corporate and charter operations.

Can hardly wait for the AB139 and the Grand!

[Mars]

FLI:

It was meant to be irony and make exactly the point that you were making. Why would anyone buy a helicopter without establishing exactly what it can and cannot do - performance wise? Is it that we helicopter pilots do not understand the issues?

[NickLappos]

FLI,

No, I think it is generally incorrect to assume that power margin is the way to assure engine failure reliability. Those military engines I note are used in awful environments by Army pilots and mechanics, and the stats are what they are, anyway. The way to assure flight safety is to fix the cause of accidents, FLI, not to add more engine power, but you miss all that, and fail to even consider it.

I note that the numbers don't move you at all, you gloss over the proven experience that there are about 9999 more ways to have an accident than an engine failure in a critical exposure window, ways that get us every day, in spite of the exposure windows we have.

You seem upset about all this, and blame lots of people for your plight. You have choices. Carefully note the cost to operate, the payload, range and OEI peformance, and buy what you want, of course. When you do find the perfect ground level, zero exposure helicopter, do not be disappointed to find the IFR range is a bit shy, and the costs are equivilent to those of an aircraft that carries a bunch more payload, since you are really buying a given helo, and operating it at 75% of its potential.

And for accident prevention, please buy an EGPWS with that new machine!

[FLI]

Nick,

I think you already know that most corporate machines bought from Sikorsky are very well equiped with the aids to flight safety that you list. I am very grateful to Sikorsky for developing and providing them.

But, the issue here is power. Not just OEI but twin engine power.

Apart from the 'B model' the 76 just doesn't have enough power.

Eurocopter's 155 has similar limitations.

The topic of this thread was "full Cat A?" Yes, there is a market for it.

I'm just glad that another manufacturer is addressing that!

[212man]

FLI touches on the points I raise quite nicely, but so far no one seems to really appreciates the full significance of onshore PC2 exposure time as a concept. We are not talking about using 332s to lift 412 cabin loads etc, we are talking about using using class 2 performance criteria to take off from a site where in fact there is no suitable reject area for a significant portion of the take off profile.

Nick, I appreciate what you are saying but please also remember that what we have to operate to, regardless of the client or operator, is some logical and justifiable arena of operation that we can justify to the proverbial "subsequent board of enquiry." Generic discussion of engine reliability does not hold sway in court; regulatory documents will.

[NickLappos]

FLI,
In supporting your point about Cat A, you say, "I'm just glad that another manufacturer is addressing that!" as if one or the other manufacturer is represented here, or as if one or the other does not provide what you are looking for.

Let me state again, the opinions I state here are mine, and not a line from any company. To infer otherwise is not correct, and frankly unfair.

I believe that all manufacturers provide helos that meet full Cat A from rigs, ground level heliports and anywhere else. The charts that tell you how to perform to those standards are in the flight manuals.

212man,
I guess you are bound to hard Cat A, am I right? If so, there are good procedures for this for virtually all aircraft.

[helmet fire]

FLI and 212man,

My point was that performance IS linked to dollars. If you want more margin then the upgrade will cost more $$. What about all those other operators who are comfotable with the current margins due to their risk profiles? Do we make them pay for the extra margin and affect their economic viability? Surely it's better the way it is now - that those who want the extra margin due to their risk profiles CAN access it by either operating with reduced payload or buying a bigger machine. If the bosses like their leather - then that comes at a cost of exposure. They can forgo the nice bits OR buy a bigger machine: at least they have an option.

Nick, on the fuel dump I agree that the critical issue part is the dip down, and as I said, it will not solve your deck edge clearance issues, but that is, as you point out, such an insignificant period of exposure. The dump pipe WILL benefit you over the entire rest of the exposure envelope with the exception of final landing stages. So taking Nick's 0.36%, that is during 99.64% of the flight time, a fuel dump pump will be of benefit to OEI situations.
A slightly unfair use of stats, but you get the point. Maybe thats your answer FLI: stay with the leather, add a fuel dump.

[peter manktelow]

Nick...we have been this way before....ok I have the OGP pie charts now and I am convinced about CFIT. Elimate that section of the chart and you take a great chunk out of your risk exposure.

Cant afford the EGPWS and dont think it is value for money in my environment where I operate literally from the beach ie 99% of my flight is over water (typical offshore oil support) where Radalt/Radar/GPS AND sound procedure should ( I say should)keep me outa the water or from hitting the rig. (is not striking the deck edge post OEI take off , sort of CFIT ?? sorry , a touch of Aussie "stirring" creeping in there.)

anyhow....

CFIT training is not readily available unless one makes up their own course and then , as far as I can see , it is still a classroom exercise. I sure would like to see what other people have done in the way of CFIT training..in the classroom/aircraft/WPB Simulator

Peter:8

[NickLappos]

peter, peace! The right procedures and awareness should serve, but at the next equipment upgrade.....


Here is some stuff to whet the argument. I did a small design exercise, crude but to the point:
Here are three similar helos, all the same gross weight, same rotor and such, but they differ in engine power. the single has one 1300 HP engine, the middle twin has two 700HP engines and can do airport OEI procedures, and the third has two 1000HP engines, and can Hover OEI.


http://www.s-92heliport.com/table.jpg

Note that the payload and range are vastly different, mostlt because of the extra gross weight and the extra fuel flow.
http://www.s-92heliport.com/payload.jpg

Note that the sacrifice for OEI hover is pretty big.

Here are two OGP pdf files for us to chew on, great stuff, thanks to some great helo pilots who work for the Oil Companies, and who really try to do the right thing. Each file is not quite 1 meg:

http://www.s-92heliport.com/OGP1998.pdf
http://www.s-92heliport.com/OGP2002.pdf

[NRDK]

Nick, Eurocopter & Airfix

With lives at stake daily and the need to hover in all sorts of wonderful places, weather and altitudes. The big twin is going to be the choice of the SAR pilots. We would gladly sacrifice a little max range and payload (no commercial penalty for us). We are frequently exploring the boundaries of possible OEI territory for protracted periods. The great threat of CFIT for us is a very real. Escaping it on one engine that insists on taking you to the scene of the accident isn’t acceptable when an EGPWS is ‘whooping away’. Granted engine failures are rare and with the increased protection afforded by modern design, we will be better placed with the newer EC & Sikorsky products. Albeit limited for now, the SAR world is a growing market. ‘Loads of power’ please.

[JimL]

Helmet,

Fuel dump is an excellent device when a helicopter cannot meet its en-route performance - for example where it has to clear a defined obstacle (a mountain peak). Guidance on this is contained in JAR-OPS 3, IEM OPS 3.500(a)(5) - suffice to say that the fuel remaining after the dump must meet the requirement for continuation to a destination or alternate (i.e. the use of dump must be planned before take-off - as it always was when being used in the S61).

The maximum take-off mass for operations in PC2 is defined by the second segment climb (150ft/min OEI at Vy - 1000ft above the take-off point); this second segment climb is identical to the requirement for PC1. This leads to a number of observations:at Vy PC1 and PC2 performance should be identical (they could be different if a PC2 take-off procedure/mass is chosen where a PC1 procedure/mass is based upon one of the more restrictive take-off procedures - in which case the latter will have a better than required second segment climb performance);

in PC2; the aircraft is only exposed to a forced landing up to the time that it reaches Vstay-up;

in PC2; for an aircraft that has a Cat A procedure at maximum weight (most of them) Vstay-up can be less than the Vtoss but is achieved at (that) Vtoss;

in PC2; for operations to helidecks, drop down is a positive element which may remove the exposure to forced landing before reaching Vstay-up (exposure to deck-edge strike is another issue but can be mitigated with PC2e);

in PC2; measurement of exposure is the time to reach one of these speeds with all-engines-operating acceleration.

in PC2 with exposure; exposure can only be to a 'crash on the surface' not to obstacles in the take-off flight path;

in PC1; the take-off flight path starts at the end of take-off-distance-required;

in PC2; the take-off flight path starts at the point where the OEI obstacle clearance point is reached - DPATO - (and is limited in the proposed revision to JAR-OPS 3);

in PC1; if there is a take-off limitation (due to obstacles in the take-off-flight-path) that might also be reflected in the PC2 take-off mass (unless eliminated by the reduced PC2 distances - see below);

PC2 to PC1 convergence occurs when the obstacle clearance OEI is reached (or as defined in PC2);Ipso facto the extent of exposure (when permitted) will be defined by one of the above. Take-off distances will always be less for PC2 as they can be calculated AEO; unlike PC1 where they have to be calculated OEI.

Nick can provide the time/distance for most of the above but from experience, it is not likely to be more than 10 seconds from the time that all-engines-operating acceleration is commenced (be it from the hover or from the rotation point at the top of the vertical section of the take-off profile).

None of this can possibly be influenced by a fuel dump - which under civilian operating rules, cannot be commenced below 1000 ft.

[FLI]

Nick, you say “I believe that all manufacturers provide helos that meet full Cat A from rigs, ground level heliports and anywhere else. The charts that tell you how to perform to those standards are in the flight manuals”.

When you started this thread, you were discussing “hard core Cat A”. We now appear to be discussing the Cat A profiles that have been in helicopter manuals for many years. Most of these profiles require unrealistic onshore, off airfield, rejected T/O areas or substantial reductions in payload. Yes, as pilots, we have choices but sometimes the field conditions just do not allow us to be so flexible.
Regulations often provide no flexibility.
Even after a full site recce in preparation for a flight, conditions can change. In the UK this summer, we have had +17 one day and two days later it is +30! Welcome to England! We have to reduce payload (leave the boss’s wife behind?) or stop enroute to fuel or even cancel the flight. Hardly “all weather Cat A” that the manufactures put in their glossy publications. We can’t even fly on sunny days! Reliable door to door time is why the clients bought the machine.

With regards to limited range, most corporate clients have access to jets. They generally do not fly 400 miles by helicopter. They go by jet. Give us 2.5 hours fuel with an aux tank option to extend to 3 hours.

When Sikorsky produced the B model, they answered a lot of the performance failings of the A. Yes, the fuel consumption was a lot more and the range reduced, but Sikorsky offered an aux tank option to redress these issues and increase the flexibility of the machine. For many years the B cornered the corporate market, with clients switching from A’s and AS365’s. What a sad day it was, when Sikorsky closed the B production line and introduced the C. Some very wealthy clients are now flying in 15 year old B’s because there has been no comparable alternative, performance wise. The large twins are just too large for many public-use sites.

When Eurocopter announced the 365N4 (to become EC155B) many clients were excited. In reality, the marginal performance of the 155B was quickly addressed with the introduction of the B1. (It went from marginal to weak). Lovely aircraft to fly, just poor performance. It has Cat A certification.

Early versions of the Explorer did not have enroute Cat A performance (level sustained flight OEI) at realistic range/payload. Addressed for later versions.

We all remember early versions of the 109… full fuel no pax or full pax no fuel! Again, addressed for later versions.

It is ironic that, most ‘full pax and full fuel’ helicopters are single engine and that they require less distance for a RTO than many so called Cat A twins!

212man has highlighted the regulatory issues very well.

Helmut fire says “Maybe that’s your answer FLI: stay with the leather, add a fuel dump”. I have flown aircraft with fuel dump. How will it help during the critical T/O phase? I hardly think you would have time, or the inclination, to spray fuel during an OEI reject! If one is able to take off Cat A then, generally, one has Cat A enroute performance in most helicopter operations. It is would be useful to reduce weight for the OEI landing but the critical power phase is during T/O.

What I find most ironic from some of the postings is, now that we are close to getting “Hard Core Cat A”, people are questioning the requirement. Ask any onshore twin engine helicopter pilot operating commercially if he needs/wants more power to satisfy safety and regulations.

[NickLappos]

FLI,

You have not moved from your starting point. You have not recognized the accident probabilities. or the cost in reduced range and payload of providing the amount of excess power. You have basically blamed those "misleading" manufacturers with the "glossy brochures", who seem to be unable to break the laws of aerodynamics enough to suit your needs.

But you are stating that you want, need, and insist on - full Cat A, and that is fine. You havn't accepted the fact that this will reduce other aspects of the design. You do know there is a design trade off at work, when you state, "It is ironic that, most ‘full pax and full fuel’ helicopters are single engine....."

See the above charts that explain how big-engined twins have LESS payload and range than equivilent singles.

The question on the table is not "How much OEI power do you want?" The question is, "What range, payload and safety benifits are you willing to give up to gain that OEI power margin?"

[Mars]

Nick:

Whilst most of us can contemplate a rational discussion of PC2 v PC1 in areas where there are no third party risks; and, under some circumstances, measure the arguments for and against PC2 ‘with exposure’ - the fact that a single can lift more than a twin is a non sequitur.

We are straying from a discussion of whether it is technically feasible and economically justifiable to eliminate/limit exposure to engine failure in the take-off and landing phases to one where the flight is always exposed to an engine failure. I’m not sure FLI’s customer base will welcome the improvement in range that is based on swapping two engines for one.

As has been pointed out in recent posts, PC2 with exposure is limited in time and space and could be part of a Risk Assessed departure/arrival regime - we (with some certainty) know: the maximum extent of the exposure; the probability of engine failure; and can assess the consequences of that failure; both in immediate terms for this phase, and in the medium and long term on our business (be it a one-man-band or a multi-national oil company).

What comes as a surprise to all of us is not ‘driving looking in the rear view mirror’ but the attempt to ‘put the car into reverse’. We already know that the EC225, AS332L2, S92 and S76 can operate in PC1 and to their credit the latest marks of the EC135, A109, MD902 and AB139 can do it in spades.

FLI may have not moved from his starting point - he knows what his customer wants; what is puzzling us is the direction of your movement.

[FLI]

Nick,

I think you will find that I have acknowledged the other aids to flight safety. I have acknowledged the reliability figures. I did, however, question the validity of the figures when discussing very high power demands. I have accepted that there will be a trade off in range and payload.

What I fail to understand is why we, the operators, must accept unrealistic onshore RTOD.

Most of your arguments are counter to Sikorsky ever producing the B model to provide an alternative to the ‘A’. The number of onshore operators using the ‘B’ is testament to accepting the trade-offs for more performance. (Less range, less payload, higher costs, etc.) The same argument applies to the AS365N, N1, N2 and N3. The answer, I suspect, is in response to customer requirements for more power.

Yes, I understand the penalties of a reduced RTOD. Anyone who has flown twin anything will recognise the trade-offs. It is there in the charts.

My issue is that all twin engine helicopter manufactures provide ‘Cat A’ but in a lot of circumstances the penalties are too great to operate full Cat A. We need more power to reduce/eliminate the RTOD.

Legislation, particularly operations within congested areas, requires full Cat A. On many of the helicopters today that is nigh on impossible without a very substantial reduction in payload. Perhaps, instead, we should be lobbying for a relaxation of the rules based on the industry statistics? Maybe, even, fly medium singles as they appear to answer a lot of the problems that the manufactures have in providing what we want?

Those cost conscious operators can continue to fly today’s machines. Let the corporate/onshore charter customers have an alternative to the ageing 76B!

As an aside, I have suffered 4 engine shutdowns on twins: Two in the cruise to secure an engine due to low oil pressure, one in the hover due to no oil pressure (burst pipe) and one engine explosion during take off. I have also had governor problems, which, not technically an engine failure, have resulted in limited power landings. So much for statistics! Touch wood, none on singles though!

[NickLappos]

Mars and FLI,

Sorry that my post was so misunderstood, as I have tried to show the natural progression in cost to the design from 1 to 2 smaller to 2 big engines. This is a free ranging discussion, and I am just painting the picture of how the cost builds. Note the reasonably symmetrical damage to range and payload as the single morphs to a twin with Cat A enroute to the very capable twin.

I note with both you and FLI take it as a given that more engine OEI power is better, safer and more modern, so you have made your minds up. Fair enough, but I am not sure why you believe it is safer, you never told us. That was the reason for the thread!

[212man]

Nick, if you think "I'm hardcore Cat A" you want to come and look at my operating environment! Especially in an a/c that drops Cat A weight from 19.5 C at sea level, and operating in the tropics.

It's too late at night to come up with long answers to discuss the points that you and JimL et al raise, so I won't try.

Please don't raise the issue of what the military do and do not accept as a risk for AEO/OEI ops: clearly they have a different agenda and evaluate risk from a different perspective. They also have a different legal liability exposure too.

I fully accept the basic premise of PC2 ops as a concept (or I wouldn't be operating onshore with water rejects!) As I have tried to say, though, the idea of adding the exposure time concept to onshore ops is (IMHO) a backwards step that is not well understood by many pilots or, especially, the passengers.

As I understood it, the frangible parts were supposed to be on the aircraft or the landing surface; not pink, soft and within the cabin!

Anyone got any figures for a 214B with a 412 head? That must be the way forward, surely?

[helmet fire]

FLI: do you read the responses? Look for your point about the fuel dump on the take off part in both my posts. Is there an echo here somewhere? Whilst you highlight the lack of brainspace available to the pilot during an OEI on take off, I note that floats and contingency power limiter switches have previously been incorporated and successfully used in the past despite such brainspace issues.

The point was that the fuel dump is not effective on the rejected take off, nor after the TDP, but it is usefull for the other 99.64% by giving you a much improved power margin for your subsequent actions. You want the power margin - and a fuel dump will give that to you. Not only does it provide you better enroute planning ability due to the ability to significantly increase drift down altitudes, it provides you a significantly better margin when you try to land OEI, but it also gives you an improving margin in your OEI flyaway attempt after TDP. And if you correctly pick your flight path (avoiding disabled kindergardens and day care centres), a fuel dump below 1000ft AGL is justified in an emergency.

So, to incorporate a fuel dump into your risk management process, you will take off 60lbs heavier, thus you should climb a bit extra for the TDP, and increase LDP. For that 0.36% of the sortie you will land 60lbs heavier in your OEI situation, but between TDP and LDP you will have a power margin increase and thus a reduced risk exposure over the remaining 99.64% of the sortie, and it may even allow you to accept higher enroute LSALTs and a more direct route due to the higher drift down capability.

Or, FLI, maybe an accurate analysis of your operating environment, payload requirements, and acceptable risk exposure levels could be matched to a machine that IS capable of achieving your aims, rather than purchasing one that just doesnt do the job and trying to blame the manufacturers for insufficient power. They make machines with sufficient power for your mission profile, you just have to pay for it.

[NickLappos]

helmet fire,

I had similar thoughts in my unposted answer to FLI's posts, frankly I just gave up. Thanks!

[GLSNightPilot]

FLI, the A++ is, IMO, far superior to the B model. The Arriel engines give lots of power, but are very efficient. We typically burn less than 600 lb/hr, unless someone gets in a big hurry. PT6s are reliable, but they are so fuel-hungry that they don't give you much range. With only a 10,800lb MGW, we can carry almost as much as a C+, and go a long way. We can't often carry a full 12 offshore hands, but 10 is common, going well over 100NM offshore. We couldn't fit the baggage for the other two, anyway. We often have to carry baggage in the cabin, strapped into the empty seats. I wouldn't want a B model, but the A++ is so much better than the straight A that it's like a different aircraft.

Engine manufacturers have come a long way, and are producing engines with more power and lower fuel consumption than were available a few decades ago, and airframe manufacturers are using them.

[FLI]

Helmet Fire said:

“The point was that the fuel dump is not effective on the rejected take off, nor after the TDP, but it is useful for the other 99.64% by giving you a much improved power margin for your subsequent actions.”

You brought up the issue of “brainspace” now read what I have been talking about in all of my post.

WE WANT TO REDUCE/ELIMINATE RTOD

The aircraft that I am familiar with that has fuel dump prohibits its use below 40Kts, regulations in the UK prohibit its use below 1000’, no gear operation during use and must be closed 1 minute before landing. As I said in a previous post, “If one is able to take off Cat A then, generally, one has Cat A enroute performance in most helicopter operations”. There will always be exceptions. “It would be useful to reduce weight for the OEI landing but the critical power phase is during T/O.” The fuel dump issue is a red herring to this discussion, period.

As previously stated, we are already flying in a 14 seater helicopter that has Cat A performance. Except, we only have 8 seats fitted! And still we find the performance marginal for onshore corporate/charter operations. What are you suggesting now…… a 22 seater for 6 pax? Again, as previously stated, the heavy helicopters are too big for most public use heli pads. We have already moved up one class in order to get some performance.

Nick, the points that I have been trying to get across are that the corporate customer, ‘he who actually pays for the machine’ has a perception, maybe carried from the fixed wing world, that a Cat A certification will ensure that if an engine should fail he and his family will be in no danger. My issue is that the performance on many machines with Cat A certification is so weak that we are not able to operate to full Cat A for most of the time. I am not talking about “Hard Core Cat A” at this time. Many times we have to operate to Cat A (Restricted). Most Corporate owners will not accept “limited exposure” as a concept, though that is what they have been exposed to, for a long time now, when operating to Cat A (R). I know that there are some operations that operate to Cat A all of the time but they have the luxury of site recce personnel, on site personnel and, normally, weeks of forward planning. For most operators this is not the case.
The UK Authority regulate for ‘full Cat A’ when operating in a congested area (a large proportion of England). The short field Cat A profiles for most helicopters still require a substantial reduction in payload and a RTOD. With temperatures regularly in the high 20’s during the summer, the penalty is even greater.

Now, I have no statistics to prove 2 engines are safer than one but I know that I couldn’t convince my customers that just 1 engine would be better! (It is a failing that most of us have if the number of twins is counted!) I haven’t been able to convince the CAA either! The manufacturers have not been convinced either or they would be promoting their medium singles a bit harder than they are!

Manufacturers, as suppliers to the industry, need to be aware of their customers needs. When asked, I will always say more power for my twin so that one day I can fly away OEI.
That day appears to be getting near, thankfully.

[helmet fire]

FLI,
you just dont get the risk management/risk exposure bits do you?
Or risk exposure V cost.
And I think you missed the brainspace bit too.
Oh and the bit about using fuel dump in an emergency. You know you are not permitted to crash either!

Repeat: if you want NO exposure you DO have 2 current options:

1. Reduce payload.
2. Buy a more powerful machine.

Do you really land at places in a heavy S76 that you could not squeeze a lightly loaded (reduced downwash) S61, S70, or maybe even B412 or AB139? Really? You land your corprate S76 in such tight areas that a few extra feet make all the difference?

I believe that if you have already moved up one class for your performace reasons then you have really not conducted a thorough analysis of requirements if you are already having problems. Or, if you customer changed their requirements - they must be aware of the extra cost.

Have you considered two light twins lightly loaded, ie 109s or EC135s?

[FLI]

Helmet Fire,

I don’t know why I am even replying to you!

If you read my post you will know that I certainly know what risk management/risk exposure/cost are all about.

What you appear to have no knowledge on is VIP Corporate/ Charter operations within UK, Europe and many other parts of the world. The types of customers and the regulations make life very difficult in this environment. Your cr*p about fuel dump for onshore VIP ops just highlights your complete lack of knowledge in this arena.

The type of clients that I am referring to do not buy old second hand aircraft!
They want new or nearly new. Up until now, there has been no aircraft that comprehensively covers all the conditions that I have been referring to. The Sikorsky 76B came close but was dis-continued.

Augusta has now produced an aircraft that will replace it. Watch how corporate clients trade in their 76’s, 155’s, 365's and 412’s to buy the AB139?

Then tell me there isn’t a market for a powerful twin!!

P.S. Not only do you know nothing about corporate aviation you don’t even know how to spell it! Same goes for performance! (See your previous post)

[JimL]

I hope that readers of this thread are finding it as informative as those of us who have been prepared to post.

Nick, in a previous email warned us to take care with the simple questions about Cat A or not Cat A; I might add my warning to his and use that as justification to clarify the usage of the term Category A. From a close reading of the definition(s) posted on the first page of this thread, it can be seen that the term is restricted to the landing and take-off phases - there is no such thing as en-route Cat A. FAR 29.67 - 'Climb: One Engine Inoperative (OEI)' is confined to establishing the requirement for first (at 200ft) and second (at 1000ft) segment climb requirements and, subsequent to revision 39, the production of data to establish the climb (or descent) data in the complete operating envelope. Whilst on the subject, there is also no such thing as Cat A Restricted (there is Group A - the UK performance standard, and Group A restricted - which was a less precise form of PC2).

It is therefore (quite rightly) left to operating regulations to stipulate what the en-route climb performance should be. In JAR-OPS 3 that requirement (simply stated) is for a 50ft/min climb performance at an altitude which gives obstacles clearance. Drift down is permitted as is fuel dump:Fuel jettison is planned to take place only to extent consistent with reaching the heliport with the required fuel reserves and using a safe procedure. The subtext for fuel dumping was discussed at great length before the words were chosen - in practice it is not as simple or as useful as it first appears; for offshore, if we refer to the previous discussion on one-way-fuel v beach-fuel - with one-way-fuel there is no possibility of use and with beach-fuel there is no need; there are specific onshore cases where fuel dump might be useful but when they exist, they need careful planning.

In FARs in the overwater case, the VFR requirement for en-route climb performance - 50ft /min at 1,000ft - is alleviated if floats are fitted FAR 135,183(d); and for the IFR case: onshore - requires 50ft/min at the MEA or 5,000ft, whichever is the higher; offshore - requires 50ft/min at the MEA or 1,500ft MSL, whichever is the higher.

Performance Classes give a much richer operational vocabulary particularly PC2 which describes exactly the points that Nick and others are making about a limited period when engine failure accountability is not provided on take-off and landing. The terms are written objectively and permit any number of methods of compliance.

Whether PC1 is used is a matter of policy for a number of interested parties: society will decide whether ‘exposure’ is permitted in a congested hostile environment (congested area) and customers (oil companies - and some cases like Norway - States) will decide whether zero exposure (PC1 or PC2e) is the standard for operations to helidecks. Provided that a large enough customer base exists for operations in PC1, the manufacturers will provide the equipment and the appropriate procedures. That these zero exposure options come at a cost is not in doubt; for some customers/States the prospect of not specifying zero exposure when it is possible (and it is) and then suffering a failure leading to death or injury is not a justifiable option.

If PC1 is not used (or is too costly in terms of loss of payload/range), PC2 provides the ability to establish the cost of exposure in a number of currencies. When the calculations are performed, the key elements will be the probability of failure, the consequence of failure and most important of all, whether the subsequent calculation is within the safety target chosen. The calculation for each aircraft type can be standard as the maximum exposure is, as Mars stated above, finite.

[helmet fire]

meow.

I hope I spelled it write.

Oh, and the AB139 - so you are going to buy a more powerful machine after all that?
Helmut.
:{

JimL: Here in Oz we have a slightly different enroute climb requirement OEI, and that is dependant upon category (airwork, charter, & VFR or IFR, etc) but it is essentially the same aim. You are right about the fuel dump not being so straight forward - it requires forethought and calculation prior to enroute use for the reasons you allude to: though I would contend that it is not rocket science. But at the take off and landing areas, it is very straight forward, simple to use, and of benefit. I also agree that it's use is of smaller benefit for offshore ops - but it is still of benefit. Overland, there are occaisions when our drift down requirement prevents me carrying preferred fuel loads in my current EMS job, let alone the take off and landing phases. And in the charter situation, it would greatly benefit our higher DA operations by allowing more fuel on take offs.

BTW, Does you fuel dump plan regulation actually say "the" heliport, or any heliport? In other words, is a diversion acceptable for fuel dumping purposes? Can "heliport" be met by a field, road or paddock, or does it mean a permanent helicopter landing site?

[JimL]

Helmet Fire,

The wording was specifically chosen so as not to constrain the operator; however, if use of fuel dump is planned (in the sense that it is known that an engine failure at some point will result in a lack of obstacle clearance) the resulting diversion must be know in order to ensure sufficient fuel reserves - this can include en-route alternates. The rules that have been quoted are, as with Australian regulations, aimed only at Commercial Air Transport (CAT). (T'was a time when fuel dump was used in the S61 to permit CAT B take-off from Aberdeen so that benefit could be taken for the overland portion; en-route climb performance had to be obtained before crossing the coast.)

You might have to accept that, for the purpose of this discussion (which is about take-off and landing performance), fuel dump has no real relevance.

None of what we are discussing is rocket science but there are a number of strongly held views that are somewhat related to the societal ethic of the State of Operation. For my own selfish motives, this thread does provide a platform to broadcast and discuss a number of concepts that we in Europe have been developing for a number of years.

Informed wisdom has it that the AB139 will only have one Category A procedure, a vertical profile with a (variable) TDP of 10ft or higher if an obstacle has to be cleared in the continued take-off; this will not require a Rejected Take-Off Distance (RTOD) larger than the pad (providing that visual cues can be maintained). One benefit will be the reduction of training (and training accidents) required for operations in PC1, and unconstrained PC1 offshore (until someone wishes to grow the aircraft).

[helmet fire]

Thanks JimL.
Could you touch on the last question I asked in relation to a heliport please?

Please keep at it with your "own selfish motives" so we can all continue to peer into the European intent of some of these rules and procedures. Thanks for the patience - it makes good reading.

[JimL]

Helmet Fire,

It was that question I was alluding to in the first paragraph of my response; yes you could have a fuel dump alternate which could be any landing area qualifying as a heliport.Heliport. An aerodrome or a defined area of land, water or a structure used or intended to be used wholly or in part for the arrival, departure and surface movement of helicopters.Note that this definition comes directly from Annex 6 Part III and should therefore be usable in any Contracting State - unless it is 'masked' by a local requirement. It has been adopted and used in JARs.

[helmet fire]

Thanks JimL,
We (in Australia) have not had much representation for the Annex 6 issues as yet, so thanks for the info.

[212man]

I think the reason the fuel dump issue is becoming talked about at slightly crossed purposes is that the rules in Australia are different than Europe regarding max take off weight. I do not have the regulations to hand, but know from discussion with Australian colleagues, that because of the high temperatures routinely encountered it is not viable to operate to what we would consider normal PC1 or PC2 criteria. Allowable take off weight is more like a 0 rate of climb OEI weight or similar; is that right helmet? This may therefore be above the en-route weight.

Therefore, in that instance it may be of benefit to dump fuel on departure in the event of a failure. However, if operating to PC2 or PC1, the second segment climb requirement will be more limiting than the en-route weight restriction, unless there is a very restrictive MSA along the track, and so it is not normally of any benefit to have fuel dumping as an option.

The reference to the S-61 ops from Aberdeen is historical and relates to a regulatory regime long past that allowed Group B take off weights as long as fuel dump could ensure Group A en-route weight. This is a similar situation to the current Australian regulatory position, I think but stand to be corrected!

None of which is of any consolation to FLI and his passengers as they wrap themselves round a tree!

Helmet et al, don't be so quick to jump down others throats; generally if somone is quoting a sensible set of facts and concerns, they are probably grounded in some reality! I could go into some detail about client expectations in a new aircraft and how they relate to the actual delivered product, but it would be totally innapropriate in this context. However, the result highlights many of the concerns discussed above.

[FLI]

JimL,
My apologies for mixing up the various operating standards. I switched to Cat A instead of Group A so that a larger audience would understand what I was referring to.
Of course, Cat A (Restricted) should have been referred to as Group A (Restricted). Or PC2.
The reference to Cat A enroute was used, simplistically, to indicate sufficient single engine power to sustain level flight clear of all obstacles whilst flying to a landing site after segment 2 on the Group A T/O.
Thank you, for the very precise wording and explanations on PC1 and PC2.

[Shawn Coyle]

Regarding fuel dump - you can't use it to reduce weight until after you've got Vtoss and the initial climb going. Check Part 29 and the Advisory Circular - it's a secondary control, and as such can't be used for performance purposes for determining all the necessary things until after you're safely climbing.
Also probably not a good idea to be trying to do it in what will be a pretty busy time anyway.

[Mars]

Even though this thread has slowed, it is not clear that we should be letting this subject go. Whilst there is a lull in proceedings and to allow time for all to draw a second breath here for your amusement and delectation are a couple of quotes. A bottle of champagne to the first guru who can tell us where they appeared and the year:Concerns relating to powerplants appeared to top the lists of all the users. A true one-engine-inoperative capability was referred to repeatedly and in a variety of ways. The operators were unanimous in their endorsement of twin engine helicopters, but less happy with available single engine performance. Ideally, an out-of-ground-effect hover capability with one-engine-inoperative was desired. FAA is encouraged by the increases in power-to-weight which have resulted from technological changes over the last 15 years in transport category rotorcraft, and it is hoped that increased technology will ultimately lead to full category A performance capability for these transport category designs.

[GLSNightPilot]

FAR 29.1, 31 January 1983.

Google is a very useful tool.

[Mars]

Well done GLSNightPilot! The document can be found at the following location

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgNPRM.nsf/2ed8a85bb3dd48e68525644900598dfb/5c3601bbfb00616c862568f600663576

The text that was quoted was indeed in the Final Rule text of Amdt. 29-21, Eff. 3/2/83.

Interestingly, NPRM 80-25 was issued on 12/15/80 and contained a proposal that would have required Category A for all helicopters certificated with 10 or more seats:Rotorcraft are projected to be carrying more and more passengers in business, commuter, and air carrier roles. This proposal would provide a clear and consistent 10 passenger division point for continued takeoff capability with engine failure for all fixed or rotary wing aircraft. The weight penalty to rotor craft for operation under the improved safety level of category A is parallel to that already experienced by fixed wing aircraft operating at the 10 passenger level and above. The tradeoffs between performance and weight are essentially the same in fixed and rotary wing aircraft. This proposal upgrades rotorcraft performance standards to those of their fixed wing counterparts. The economic and safety considerations of the continued takeoff philosophy for 10 or more passengers are discussed in considerable detail in NPRMS 67-11 (32 FR 5698; April 7, 1967) and 68-37 (34 FR 210; January 7, 1969) and in the preamble to Amendment 135-18 (35 FR 10098; June 19, 1970). Pertinent rulemaking philosophy and FAA's response to industry comments contained therein apply equally to this notice. In spite of dire predictions to the contrary, the current fixed wing air taxi industry is thriving under the 10 passengerIn the event, the proposal to meet an operational requirement of PC1 for helicopters with 10 or more seats was not carried and, with one exception, the applicability of FAR 29.1 was downgraded to a requirement to meet PC2. The exception; helicopters with Maximum Gross Weight greater than 20,000 pounds and certificated with more than 9 passenger seats, for which the requirement remained… hang on! Doesn’t the S92 fit into that category? In Europe, FAR 29.1 appears to be seen only as a certification requirement.

The results of the FAA deliberations can be seen in a modified form in the JAR-OPS applicability for the Performance Classes:PC1; passenger seating configuration of more than 19 or any operation in a congested hostile environment.

PC2; passenger seating configuration of more than 9 but less than 20.

PC3; passenger seating configuration of 9 or less.How wide of the mark was the original aspiration contained in the referenced text: FAA is encouraged by the increases in power-to-weight which have resulted from technological changes over the last 15 years in transport category rotorcraft, and it is hoped that increased technology will ultimately lead to full category A performance capability for these transport category designs.well, considering that statement was probably drafted between 1980 and 1982, it is difficult to estimate what time scale ultimately was meant to encompass (did they consider that we would still be discussing this 24 years later?). Isn’t it interesting though that, for a number of good reasons, the FAR 27 twins have arrived at that destination already but, as they are limited to 9 passenger seats, were never intended even to make the journey.

My contention would be that we have also arrived for the FAR 29 helicopters that were designed after the application of this NPRM; that this cannot be done for all sites, under all operating conditions and at the maximum mass, is a feature of the flexibility of the helicopter not one of lack of intent or engineering skills. It is therefore for operational regulations to establish the conditions under which any necessary gap might be bridged. Risk Assessment provides the tools to establish what that gap might be under a particular circumstance, and whether to use PC2 (with exposure) to bridge that gap - or reduce payload and operate in PC1. For offshore operations, we now have the added tool of performance modelling to virtually reduce that performance gap to nil - operating in accordance with PC2e but without compromising the pilot’s discretion.

Every day it is possible to make the last minute tweaks - the introduction of the CT7-8A will add another 5% to the available performance with the same geometry and without modification to the airframe; how, by clever engineering and by using different materials to improve the 30 second rating by about 140hp. This appears to be something for nothing as the 30 second rating should never be used and does not have any operational cost.

[JimL]

Nick opened this thread describing the dilemma:One side says that the engine is prone enough to failure that it is wise to design a helicopter that has complete coverage of its flight path so that engine failure can occur without probability of a mishap. Let's call this hover to hover or "full Cat A".

The other side says that a limited exposure where an engine failure can result in a hard landing is acceptable, as long as it can be shown that the probability of an engine failure in that exposure time is as slight as the other kinds of failures that can happen to a helicopter. Let’s call that "limited exposure."It has been the belief of a number of us for some considerable time that performance, as with all aviation matters, is not an ‘either or’ choice. What we should be debating is the management of safety - which is not measured in absolute terms but expressed as safety targets.

That two views are expressed already indicates that any manufacturer who wishes to maximise its market, has to position its product so that it can meet both aspirations. The one that cannot be satisfied is that which demands PC1 for all sizes of sites at all density altitudes.

Recent developments have increased the number of risk management tools; performance modelling has shown that, for offshore operations, the margin of exposure (due to performance) can be reduced to a theoretical zero. Why the conditional statement? Because those of us who have been in offshore operations for a number of years will know that, on occasions, the environmental conditions and the obstacle environment, prevents us from flying the optimum profile.

For the uninitiated, there are three (theoretical) subdivisions of PC2 that an operator can take advantage of; these range from nil exposure (without using Category A procedures) to limited exposure - and are as follows (not in that order):PC2 in its ICAO form; this requires that a safe-forced-landing can be carried out. There are a number of uses of this basic PC2: the take-off from a surface that is not firm enough for a rejected landing; take-off over a surface that has frangible obstacles - bushes or small trees; or take-off from a helideck where deck-edge clearance is provided by the procedure but ditching will be required if the engine fails immediately after the rotation or immediately before the commitment to the landing (the GOM in low sea states).

PC2e; which has a zero exposure but does not use a Category A procedure and which is primarily based upon a profile produced with the aid of a simulation model that has been validated with limited flight testing. The procedure will be based upon information contained in Part 2 of the Flight Manual comprising a take-off profile, deck-edge miss and a drop down graph. Whilst operations might be conducted with this profile the enabling regulation is not likely to force compliance for the reasons stated above (this is a good methodology in temperate offshore provinces like the North Sea and Atlantic Canada as it is unlikely to lead to a reduction of take-off mass - under most circumstances).

PC2 with exposure; which enables operation with exposure to an engine failure which is both limited and measured; the static risk of such operations can be (pre)measured and set against a safety target based upon the limit of the exposure (in time) and the reliability of the power unit. In this case the consequence of the engine failure is accepted as a residual risk. It is considered that such exposure can be limited to less than 10 seconds.Nick has indicated that, on PPrune, he does not speak for his company but as an individual; that this is correct can be observed by the actions of Sikorsky which appears to be doing precisely what is described above and is positioning the S92 to meet the performance aspirations of its actual and potential customers (whatever camp they might be in).

What we have to hope for (because we have no information on which to base any assumptions) is that Eurocopter will take note of the enlightened attitude of Sikorsky, and also position their products (the EC225, EC155 and AS332L2) to meet both sets of aspirations.

[FLI]

JimL,

I am a bit confused with your explanaition on the performance on the S92.

This is an article that I found on the H-92 written last year at the Paris Air show.
I quote just part of the article.

“The civil S-92 aircraft on which the H-92 Superhawk is based has already achieved U.S. certification. Standard S-92 safety features that will be found in the H-92 Superhawk include flaw tolerant components, multiple redundant control systems, bird strike protection, high-intensity radiated field protection and category A (class 1) performance, which allows pilots to continue safe flight in the event of an engine failure at any point in flight”.

Full article can be found here:
http://www.ainonline.com/Publications/paris/paris_03/pd2h92pg14.html

The article implies that the S92 will have, so called, “Hard Core”/ ”Full Cat A”. Is this correct? Are there substantial payload reductions or DA restrictions to achieve this?

[NickLappos]

JimL,

Thanks for clarifying the case with your last post. Note that the performance for Cat A is not a sharp decision, yes or no, as you say. I believe few helicopters will come out where the maximum weight allows full Cat A, because the ability to recoup this extra power as payload for other operations will be so compelling that the aircraft will have two or three operating procedures, one for hard Cat A, and one for lesser OEI but a higher MGW and much better payload/range. Thus one design will serve several possible customer bases.

This debate has unfortunately not driven into the kind of discussion I had hoped, because it became a vote on hard Cat A yes or no, and not a discussion of safer or less safe.

It seems that so many vocal regulators and some customers (FLI out there?) speak as though the solution to helicopter operational safety concerns is more power. This is in spite of the data, and of the real hazards. If the debate does not move off this as a flip switch, yes/no, helicopter safety will suffer for another generation, I believe.

I am struck too at the inability of we who make the machines to express the cost to a design to meet these requirements - the plots I provided that showed a massive penalty for hard Cat A were virtually ignored by all, as if they were not part of the discussion, perhaps because I phrased the discussion so poorly.

So, here is a possibly new way to state the question:

Given that a helicopter will be designed to lose 25% of its range (or the equivilent payload) and this penalty assigned to safety concerns, what concerns should be addressed? A possible sample:

Hover to hover full Instrument procedures to heliports in rural and urban areas, independant of airplane operations

Pilot visionics, where the pilot sees the world through a see-through virtual reality device, with FLIR and CGI mixed so that night/instrument is as if he were in a simulator, and VFR like rules are applied to all traffic.

Hard terrain avoidance, where the machine is not capable of being driven into the ground except as a controlled landing. This includes brown out and zero light available circumstances.

Maintenance free operation for a full year, during which only pilot pre-flight inspection is required, and during which all maintenance activities are diagnosed by the aircraft

Tolerance to accept common corrosion, damage and mishandling so that no unsafe condition is developed for the year.

Ability to Fly in any icing, rain, or wind condition without loss of control.

Fly with the noise signature of a common large car, so that ground observers note no objectionable noise, even in rural areas.

As a helicopter R&D engineer, I can state that all the above are not just possible, they can be certified within 10 years. And none will cost half of what hard Cat A does cost to the design. As someone who wishes the best for all of us (we are one big family in a way) I simply cannot understand why we are not asking for these things to be legislated!


And for FLI, your questions about the Cat A performance of the S-92 have already been answered in this thread. It is my belief that the S-92 is the most capable hard Cat A platform now available, with more payload, range, speed from a hard Cat A operation off a rig or from ground level than any helicopter. However, this thread has nothing to do with any specific helo, in spite of your wish to make my general comments somehow specific to any given helicopter's capabilities. You might just be one of those fellows who just never gets the message, sadly.

[helmet fire]

Well said Nick - for the third or fourth time this thread.

Is it that the operators are really not savvy enough to buy a machine that is capable of flexibility - or is it that the customer really hates to think (or cannot understand) that there is an empty seat next to them in order to reduce their risk exposure? Or can they in no way be educated about this?

I note that FLI said they had adjusted the seating of the aircraft to 6 in order to achieve greater power margin, so why not look at your operating envelope, pick the max DA and range your customer will make you operate to - couple it with the exposure profile they desire - then fit the max number of seats that will be able to be filled? Hey presto: you have achieved what you want: a "hardcore Cat A" machine without penalising other buyers who can accept different risk exposure.

Or maybe the answer to "the customer is always right" thing when education fails, is to give them what they want. How about Sikorsky produce a VIP S76 with only four seats in the back so that it can be considered to have the best PC1 rating known to man, and then a utility version for those who want to adapt to flexible performance/exposure/cost profiles depandant upon missions?

Nick: lets not divert spending into areas that can resolve higher risks to helicopter operations, lets produce machines that never require performance planning.:ok:

[Xnr]

Legislation, particularly operations within congested areas, requires full Cat A. On many of the helicopters today that is nigh on impossible without a very substantial reduction in payload. Perhaps, instead, we should be lobbying for a relaxation of the rules based on the industry statistics? Maybe, even, fly medium singles as they appear to answer a lot of the problems that the manufactures have in providing what we want?


Regulations for Cat A capabilities are in place. The regulatory bodies feel that it IS a safety concern. (Third party liability.....can't have helicopters landing on people in the street below when the aircraft misses the rooftop helipad OEI.)

The problem as I see it is that companies may be ignoring the fact. Hesitant to bring their customers up to date on the Cat A issue for fear of lost contracts or closed flight departments. Regulatory bodies do not enforce the regulations that they have put in place until, as Nick says, once in 55 years, we have an accident.

Whether we feel that money could be better spent elsewhere is a great topic for discussion. This topic really should have been discussed between operators, manufacturers and regulatory bodies before the regulations were put into effect. Now the guy caught in the middle is the pilot. Surprise surprise.

For the record Nick, I think we could spend our money more wisely than having full Cat A capability but the regulatory body in this country doesn't seem to agree.

Cheers

[Brian Abraham]

Total 19,500 Offshore 16,000 S76(A & C) 11,500
Least anyone thinks that the above experience level endows me with any particular wisdom I wish them to think otherwise. The number of hours are not necessarily an indication of an aviators ability or knowledge. It has been said before “Does he have a thousand hours experience, or one hours experience repeated a thousand times”. I have to say I probably fall into the latter category as all my offshore time has been gained flying out of the same geographical point for the same operator. I read the postings on these pages with some envy at times at the professional lives some of you lead (the grass is always greener).

If I were to have a wish list it would be for more power, both dual and OEI, a boot double its current size, means to avoid CFIT, and the ability to make a zero/zero landing. The 76 is a great helo in the temperate climate in which I fly, but the performance bleeds too quickly once the OAT starts to get up. To have OEI hover would be outstanding, as I would be able to use all those rigs I fly over as an alternate, instead of having to carry the emergency to the beach (which may well be clamped, as we don’t bother with planning to have an alternate in our operation). Our individual personal history and experiences is what colours our thinking and having had two catastrophic engine failures with the Turbomeca in the C model (only engine failures I’ve had in my career – one at CDP on a rig takeoff, the other in the hover prior to departing a runway) you can guess where my sympathies lie. I recognise all that Nick says re the engineering trade offs required as relevant, and there is no such thing as being able to make the business risk free, even by regulation. The Concorde, for example, was only required by regulation to be able to handle a single (as are all multi airline transports), not a double engine failure on one side, but we all saw in graphic detail what happens when it happens. Likewise the DC-10 at Sioux City landing with no hydraulics – what chance that, finding yourself with no hydraulics and having to control the aircraft purely by manipulation of the throttles? I’m reminded also of a young lad making his first night solo IFR trip in a S-2 Tracker in my navy days. He had a total electrical failure due to a compounding series of mechanical problems in each engine. He got down OK but the investigators write up asked the question “Twin reliability or double trouble?” At times the dog of fate simply lifts its leg and pisses on the pillar of science.

I detect a level of frustration in some postings that the author is not getting his message across. Once again we look at things based on our past experiences, training (or lack of) and it can be quite difficult at times to see the light. Those of you with an instructing background (which I do not) would be able to tell some stories. Our operation has a Cat A takeoff procedure to use from our home base which has 2,000 feet of runway. The only trouble is that the procedure makes no allowance for the accelerate distance required for when the failure is after CDP. Ten years of trying to get management to see the light has been for nought, so it says nothing for my abilities as an educator. An old saying has it that the only stupid question is the one not asked. Similarly the only stupid opinion is the one not given. Every one is entitled to an opinion, but he is not entitled to be wrong in his facts. The following philosophers say it all.

John Stuart Mill in Utilitarianism. Liberty. Representative Government. London 1960 says:
The peculiar evil of silencing the expression of an opinion is, that it is robbing the human race; posterity as well as the existing generation; those who dissent from the opinion, still more than those who hold it. If the opinion is right, they are deprived of the opportunity of exchanging error for truth: if wrong, they lose, what is almost as great a benefit, the clearer perception and livelier impression of truth, produced by its collision with error…….We can never be sure that the opinion we are endeavouring to stifle is a false opinion; and if we were sure, stifling it would be an evil still.

Von Hayek
To deprecate the value of intellectual freedom because it will never mean for everybody the same possibility of independent thought is completely to miss the reasons which give intellectual freedom its value. What is essential to make it serve its function as the prime mover of intellectual progress is not that everybody may be able to think or write anything, but that any cause or idea may be argued by somebody. So long as dissent is not suppressed, there will always be some who will query the ideas ruling their contemporaries and put new ideas to the test of argument and propaganda.
This interaction of individuals, possessing different knowledge and different views, is what constitutes the life of thought. The growth of reason is a social process based on the existence of such differences

A rambling old man with too much time on his hands best go.
Blue Skies to all,
Brian.

[peter manktelow]

Onya Brian. Hours may not be the whole measure but it is a fair indication that you are doing something right ie keeping self , pax and machine , out of the water.

( …having worked within many multi cultural situations may I offer this small snippet to help enlighten some of the Pprune audience…...boot = baggage compartment = trunk….they know to whom I refer ! Sorry Brian , I could not help myself)

We all wrestle with our particular (operational) demons but as Xnr says
“Now the guy caught in the middle is the pilot. Surprise surprise.”

..and this is what I find annoying. We are at the bottom of the “food chain”. As pilots , we must make the operation work after the manufacturer presents his machine , the regulator does his bit , the auditor/oil company lays down their creed and our management tries to sell the whole shebang. We are not caught in the middle , we are caught at the end and this is where Nick’s involvement in Pprune is worth a million dollars. I know you are expressing private opinions , Nick. Fair enough , but you are also in a position to take in what you hear from this far wider audience of pilots and allow it to effect outcomes at the beginning of that “food chain”

My parting remark is borrowed from a good Canadian buddy of mine who once said..
”take any helicopter (single or multi ), remove x% of seats and you have a half decent performer”

I believe that a lot of our performance woes are directly attributable to ignorance (or head burying or economics) on the part of the end user. In the offshore patch , that is the oil companies. I should really get a Pprune pseudonym before I blast the oil companies but ………

Peter:8

[NickLappos]

peter,

tell me about pseudonyms! I am considering stopping posting in my name, as it appears some folks think it is fair game to pin the thoughts onto a particular manufacturer, and even take pot shots from that view point.

Brian, those are not ramblings, they are well thought out positions! I do like the philosophical quotes, too. I too think the opinions of all are valuable, for those reasons.

The issue we face is that the performance margin rubs directly against the profit margin because the payload can be reduced to permit better performance. This is not a statement of greed vs good, it is physics.

What I see is that as pilots we want the CHOICE removed, so that the reduced payload is hidden in a lower MGW, sort of removing the hobson's choice from the field of consideration. An interesting problem!

I will say this, many posters have considered the law's requirement of hard Cat A as proof enough. I do not.

The European law cannot get off their duffs and approve IFR approaches for helos (by IFR for helos I mean to heliports, of course)! (I know of many operators who do their own thing, because of this!) The law can't even find it to insist on CFIT protection devices. I have asked several times for someone to show that safety and hard Cat A are connected, and all the responses simply list the regulations, as if that were proof. All the while 30% of our crashes are completely correctable with EGPWS, and 0% of the twin crashes are due to insufficient OEI performance!

That rant now having passed, I do welcome all the ideas posted here!

[heedm]

I've been busy and haven't been following this thread lately, but even still, I'm going to cut into this based on one point.

Nick said, "0% of the twin crashes are due to insufficient OEI performance!".

I know of three crashes in twins that if they had sufficient OEI performance, then the crashes wouldn't have happened. Did you need details of these crashes or have I missed what your point actually is?

[peter manktelow]

To psuedonym or not to psuedonym , that is the question.

Hang in there Nick. I far prefer to know , the party to whom I am speaking. Unfortunately “pot shots” are part of the deal. In Australia we call it the “tall poppy syndrome” and it is a particularly nasty side of our Aussie psyche. When/if opportunity ever permits , I can better explain over a beer or three.

I guess the main issue I was trying to get across in my last post was that in my experience , the people who should know , don’t know. I am referring to the various client companies who use our multi engine helicopters , fully believing that they have 100% Cat A…or worse believing that Cat A gives them , as one previous post said , a 100% single engine capability on par with the airlines. And this ignorance also extends into other areas of performance as mentioned by Brian with his lack of suitable “accelerate distance required for when the failure is after CDP”. I was once reprimanded by a “goose” of a manager for questioning the company’s OEI definitions/performance and whether in fact the client was aware of what they were getting or not getting. So OEI performance is a subject “dear to my heart” so to speak.

The whole multi engine OEI situation is a very confusing subject. Just ask any keen young copilot who has recently been pouring thru the books. I thought I knew a few things about the issue but am continuing to learn , especially thru this medium. Not helping is changing and differing regulatory rules. Staggeringly ,within one regulatory group , there can be differing company rules..AND within a single company at different bases , there are different rules. Talk about the tower of Babel !!

You have convinced me that your argument is sound and statistically watertight. The only problem that still exists is that my “pucker meter” is still inordinately affected as I land and takeoff from the rig. Whether I am flying Brand X or Brand Y helicopters , THE CLIENT wants every fitted seat occupied and the boot , trunk , baggage compartment stuffed to bursting…..and they want to believe that no matter what happens…we can fly em home if it all turns wobbly.

Perhaps organizations such as OGP should be paying a bit more attention to the subject of educating their members on this subject.

Peter
:8

[Nigel Osborn]

I've been trying to keep up with all the experts on this tread but to be honest, I am some what bemused at what should not be a problem.
In Oz cat A has a very straight forward requirement. Before CDP you must have the ability to land back. After CDP you must have the ability to fly away. It does not matter if you are on a rig platform 200 ft above sea level, on a work boat 15 ft above sea level, on a mountian pad, in a jungle clearing or a 10000ft runway. You simply adjust your take off weight to suit the cat A requirement; this of course means that you will have different take off weights to suit the differing conditions.
All twins flown at the correct weight must be able to maintain level in the cruise on one engine at specified heights. So if you take off at sea level to fly over mountains, you must use a weight that is suitable.
After CDP from a helipad, you must reach VTOSS and started climbing by 35 ft, no reject area is required. If you can't do that, you are too heavy.
So I just don't see the problem. Fly at the correct weight and your company should pass those weights on to the customer if necessary.
In OZ we rarely use cat A unless the customer requires it.:confused:

[Xnr]

The whole multi engine OEI situation is a very confusing subject. Just ask any keen young copilot who has recently been pouring thru the books. I thought I knew a few things about the issue but am continuing to learn , especially thru this medium. Not helping is changing and differing regulatory rules. Staggeringly ,within one regulatory group , there can be differing company rules..AND within a single company at different bases , there are different rules. Talk about the tower of Babel !!

Nick

I have struggled with this topic for well over a year now. Seeking the advice of those far more knowledgeable than I.

Under Canadian regs some helipads (80'x80') which are located within built up areas are "restricted to helicopters than can maintain 4.5 m (15ft.) above the highest obstacle within the approved approach and departure path when operated in accordance with the approved aircraft flight manual with one engine inoperative."

I fly an S76A model. Do you feel that I can legally land at or depart from this helipad?

Conversations with Transport Canada, Flight Safety and management have only yielded politcal bullsh*t.

In frustration I ask you. Please be as direct and to the point as you can as I consider your opinion invaluable.

Cheers

[Nigel Osborn]

Hi Xnr

Any twin has a certain capacity with 1 engine out. From the flight manual you can calculate what your weight should be to achieve single engine performance. This then becomes the weight you use from that helipad to give full engine out capability.

For example when we did marine pilot transfers to LNG tankers in a S76A++, we had to have full single engine capability from beginning to end. Sikorsky recommended an approach & take technique & weight which we stuck to. We had 2 pilots, about 500-600 lbs fuel, sometimes less on very hot windless days, and took 1 or 2 marine pilots. At the weights we used, I could have done the whole flight on 1 engine.

So it just depends what rules exist in your area and then adjust the weight accordingly.:O

[JimL]

Nick et al,

I think that Nigel has hit the nail on the head - I am only aware of one poster in this whole discussion who was asking for PC1 Operations, at MCTOM (MGM), from any site!

Nick, you have a company representative on the ICAO WG that is proposing amendments to Annex 6 to include recommendations for TAWS and ACAS; you should be aware that this was accepted by all of the regulators on the WG and only opposed (initially) by non-regulatory members (no names no pack drill). Why a recommendation? Because Annex 6 is (almost) a one size fits all document and to apply a Standard to all helicopters which are operating in CAT would have been universally opposed. For reasons that you are well aware of, the remark about European regulators smarts a little. Be prepared to see extensive improvements in the approval of Approach Procedures now that EGNOS is being used to add integrity to GPS (which was the basis of the conservatism).

Nigel, a great deal of cooperation has been achieved with OGP and they are kept aware of all the performance arguments; those members who have operations in a hostile environment are enthusiastic about PC2e because it has the potential for zero exposure to-and-from Rigs without the formality of Cat A, and without requiring the greater than 1D sizes that are presently contained in Cat A elevated heliport/helideck procedures.

Xnr, I am not intimately aware of Canadian Regulations but the obstacle clearance that you quote is built into ICAO (in fact you have omitted the divergence factor) and most other operational regulations (and of course FAR 27/29); it is not just a feature of Cat A, or related to the helipad size that you have quoted. PC1 & 2 both require this but only where an obstacle cannot be avoided laterally.

By the way, in an earlier post Helmet Fire intimated that Australia were not yet involved in the ICAO debate; not true you have had an active representative on the ICAO WG since it started its work.

[FLI]

Nigel Osborn said:

“For example when we did marine pilot transfers to LNG tankers in a S76A++, we had to have full single engine capability from beginning to end. Sikorsky recommended an approach & take technique & weight which we stuck to. We had 2 pilots, about 500-600 lbs fuel, sometimes less on very hot windless days, and took 1 or 2 marine pilots. At the weights we used, I could have done the whole flight on 1 engine.”

Have readers realised that we are talking about a performance enhanced helicopter (from the original Cat A “A model”) that is designed to carry 14 people, with a range of 400 nm, but operating with 4 people and 120ish nm range to achieve “hard core Cat A”. This from a helicopter that, as GLSNight Pilot says “the A++ is, IMO, far superior to the B model” when referring to performance/payload.

I realise that this discussion isn’t about aircraft types but the requirement, or otherwise, of “hard core cat A”. The example just highlights the problems we face when operating to the regulations.

I understand the manufacture’s frustration with the regulatory authorities regarding engine risk profiles for helicopters, but isn’t it their remit to convince them that Cat A is unnecessary or produce something that will accommodate the regulations in realistic operating conditions?

JimL says,

“I am only aware of one poster in this whole discussion who was asking for PC1 Operations, at MCTOM (MGM), from any site!”

The definition of PC1 that was given by JimL at the beginning of the thread was,

“Performance Class 1 operations are those with performance such that, in the event of failure of the critical power unit, the helicopter is able to safely continue the flight to an appropriate landing area, unless the failure occurs prior to reaching the Take-Off Decision Point or after passing the Landing Decision Point in which cases the helicopter must be able to land within the take-off or landing area”

I have not been asking for PC1. We already operate to this requirement most of the time, but, at a huge disadvantage to payload.

I have been advocating a realistic “hard core Cat A” (Fly away OEI with no reject required).

If one reads through the thread one will see that I am not a lone voice.

[Xnr]

Hi Nigel

Thanx for your input. It echoes most of the answers I receive on this topic.


Any twin has a certain capacity with 1 engine out. From the flight manual you can calculate what your weight should be to achieve single engine performance. This then becomes the weight you use from that helipad to give full engine out capability.

Later in your post you state when you required full Cat A capability, Sikorsky came up with profiles and weights that you stuck to.

Why would you not have consulted the flight manual as you recommended above.

To my knowledge there is no provision within the rotorcraft flight manual to operate a S76A to or from a helipad Cat A. I am not familiar with the A++.

As the restriction states "when operated in accordance with the aircraft flight manual".

Cheers

[JimL]

In looking at my previous post I see that, when answering Xnr's point about obstacle clearance, I have committed Nick’s heinous sin of quoting regulations.

What I might have said was if an Authority wishes to ensure engine failure accountability (particularly in a built up area) it must specify the minimum obstacle clearance standard - not to do so would be to ensure that the twin is less safe than a single as it has double the probability of an engine failure with the same consequence.

FLI - then you have to turn to the AB139 within its present MCTOM (MGW) or fly one of the FAR 27 twins. I personally would accept PC1 where it includes a variable FDP with or without a modified RTOD. As has been said in previous posts, without OEI HOGE, a set of flexible procedures that give a continuum from the helipad through the confined area (short field) to the clear area would be a goal for the manufacturers to aim at.

[NickLappos]

JimL,

Surely quoting regulations is a very minor sin... ;-)

I guess "getting off duffs" was a bit strong, eh? Sorry, but I do think there was a point there somewhere, in that one would think the accident record should have some correlation to the regulatory activity. Perhaps in another life!

[Xnr]

JimL

Nick seems to be away, although, as of late hurricanes may be the priority right now. You seem well versed on this topic so to you I pose the same question.

A simple yes or no answer will suffice.


posted 30th August 2004 02:54
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quote:
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The whole multi engine OEI situation is a very confusing subject. Just ask any keen young copilot who has recently been pouring thru the books. I thought I knew a few things about the issue but am continuing to learn , especially thru this medium. Not helping is changing and differing regulatory rules. Staggeringly ,within one regulatory group , there can be differing company rules..AND within a single company at different bases , there are different rules. Talk about the tower of Babel !!
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I have struggled with this topic for well over a year now. Seeking the advice of those far more knowledgeable than I.

Under Canadian regs some helipads (80'x80') which are located within built up areas are "restricted to helicopters than can maintain 4.5 m (15ft.) above the highest obstacle within the approved approach and departure path when operated in accordance with the approved aircraft flight manual with one engine inoperative."

I fly an S76A model. Do you feel that I can legally land at or depart from this helipad?

Conversations with Transport Canada, Flight Safety and management have only yielded politcal bullsh*t.

In frustration I ask you. Please be as direct and to the point as you can as I consider your opinion invaluable.

Cheers

[rjsquirrel]

Xnr,

I am not sure what you mean by a "bull" answer. What did they say?

The rules that you fly under are part of your ops manual. I assume you are a 135 operator or its equivilent. Does this manual list the helipads and procedures that you are authorized to use? If so, you are covered. If not, then how are you authorized to land there?

Every now and then someone with too much time on their hands comes across an inconsistency that seems overpowering. A few years ago a NY city pilot discovered that if he landed at a helipad in Manhatten, he might actually be violating the flight manual HV curve for some obscure reason. This made its way around and around, and was never really resolved, but folks kept operating, and eventually it was forgotten.

Nobody will publicly advocate breaking any rules, especially TC, and neither can your management. If you ask a question that requires them to assume your risk, or that tells them to stop your operations, you will not get a yes or no answer, because they're not that dumb.

There are Cat A procedures for every transport helo, of course. If you must use them at your heliport, and the heliport is too small (or the procedure needs too much room) then you should find a new place, or a new helo, a new job or a new hobby to keep you occupied.

[Xnr]

Squirrel

Thanx for your candid reply....as ususal the **** roles downhill.
Nobody will publicly advocate breaking any rules, especially TC, and neither can your management. If you ask a question that requires them to assume your risk, or that tells them to stop your operations, you will not get a yes or no answer, because they're not that "dumb".
TC won't enforce their own regulations and because of that operators see it as the green light. But you are right, if noone else has the backbone to do the right thing, the pilot is the last hope.

Its much easier for everyone else that way isn't it?

Cheers

P.S. only in aviation can the word "dumb" and the word "responsible" be used interchangeably......and I have a new hobby

[helisteve]

Hi All,
I don't have access to a S76A flight manual. Can anyone tell me if the S76A is capable of VTOL Category A performance from a ground level helipad at sea level/15c day?
Thks

[Gomer Pylot]

Yes, depending on the load. The payload won't be high.

[HeliTester]

I also do not have access to an S-76A Flight Manual, but I know there is one S-76A Category A VTOL procedure that is actually certified by an Airworthiness Authority. The operating weights are given in Supplement 3 to the CAA Approved S-76A Flight Manual. The takeoff uses a vertical climb to a 120 ft TDP. But because vertical landback from 120 ft is not possible, the rejected takeoff must be performed with forward speed, so there is an associated rejected takeoff area (possibly 400-500 ft?). I think it’s called a Vertical Procedure, but it’s actually a Short Field Procedure. Don’t know how to get a copy of Supplement 3; perhaps Nick Lappos (who started this thread) can help.

[Collective Bias]

If I remember right on this procedure, the landing (if loosing an engine) is vertical up to 70 ft, and between 70 and 120 ft there is a short forward area (400 ft) required.

Max TO weight is not much more than 9 000 - 9 500 lbs I think.

CB

[HeliTester]

CB,

For the S-76A there are two TDP’s called TDP1 (40 ft) and TDP2 (120 ft). If an engine fails on takeoff before passing TDP1, the landback is vertical. If an engine fails after passing TDP1 and before reaching TDP2, the pilot must rotate nose-down and landback with forward speed. TDP2 is the “real” TDP, as fly-away must not be attempted if an engine fails before passing TDP2.

I think you are remembering an S-76C++ procedure where TDP1 is 70 ft and TDP2 can be as high as 170 ft.

HT

[rvl]

Hello everybody,
Is anybody who can tell me how can an AS355F2 can operate in Category A Class 1? What are the weight limitations for this operation?

[paco]

If memory serves, 2100 kg is the max weight for Cat A

Phil

[rvl]

My question referred basicly to the AS355F2's performance: probably there is a maximum (decreased) weight limit to the helicopter to be able to fly in CAT A Class 1 (appropriate for take off/en-route/landing - according OPS)

[Shawn Coyle]

The max weight is going to be weather (OAT and PA) dependent isn't it?

[paco]

Yes, but for quick reference 2100 kg in a country like UK is about right, although you should really use the chart in Suppl 11.1. The max weight is normally 2540 kg so that would make sense.

His question is not very clear, though. Cat A Class 1?

phil

[JimL]

Paco,

You're quite correct that the question was not framed in a way that an answer could easily be provided.

After exchanging a series of PMs with 'rvl', it would appear that her question was about operating from a 'congested hostile environment' and therefore related to the 'helipad' procedure.

As I always point out, on a runway, the clear area CAT A procedure provides little that PC2 could not provide - PC1 has to be achieved by 200ft in either case and the take-off mass is almost always related to the second segment climb (which starts at that level).

Jim

[Upland Goose]

AS355F1 Cat A Clear Area 2400kg Cat A Helipad 2200kg

AS355F2 Cat A Clear Area 2400kg Cat A Helipad 2200kg

The Max T/O Mass of 2540 for F2 is unscheduled for Cat A i.e the extra 140kgs - but on a particular day you may be able to take off Class 2 at 2540kg and maintain CAT en route performance

I think!! UG:hmm:

[barnas]

Hi! Could you please tell me how can we distinguish between Helicopter Performance Classes 1, 2 and 3? Is this classification based on types of helicopters or the number of passengers they can carry? Or any other thing? Any suggestions will be appreciable!! :)

[HeliComparator]

For a twin engined helicopter, it is determined by how the operator chooses to operate it. Of course there may be some operational regulations requiring operation in one of those classes, depending on the rules applicable in the locale. See for example JAR-OPS 3. The rules are a bit too complex to briefly explain in a post.

A single engine heli can only operate in PC 3.

In simplistic terms, with PC1, in the event of an engine failure you can maintain safe flight or land on the helipad/ runway. PC 2 is the same except that there is a brief period during takeoff and landing when you may have to make a forced landing off the helipad / runway if an engine fails

PC3 you may have to make a forced landing any time an engine fails.