Hard Core Category A?
 

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!

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.....;)

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...

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’ -

Not 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:

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!

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:

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):

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.

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

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.

I agree totally with ATN and 212man.

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

Right what's next

Hydraulics!

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.

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.

DECK EDGE
 

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

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.

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.

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.

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).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.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.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.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.

CAT A, peformance class 1
 

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

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:

1. Is the Bo105 certificated for Category A; and
2. Does it have approved Category A procedures in its flight manual

In 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.

BO 105
 

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:

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.

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.

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)?

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?

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.

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.

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.

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.

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.

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

@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.

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.

Nick:

Could be our confusion is based upon a previous statement made when this subject was aired on an earlier thread: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: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.

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.)

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.

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!

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.

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

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.

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.

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.

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.