Helicopter Height-Velocity (H-V) limitations
 

I see that EASA have published NPA 2014-19 'Helicopter Height-Velocity (H-V) limitations':

http://easa.europa.eu/system/files/d...%202014-19.pdf

There are some interesting interpretations of the Certification rules of Part 29.1 (and others) which are bound to put EASA at odds with the FAA because it changes the intent of the rule as established in NPRM Notice No. 80-25. (In simple terms, it requires the H-V Diagram to be a limitation when the number of seats is 10 or more - thus requiring operations to be either Pure PC2 or PC1 for such helicopters.)

One of the interesting aspects of the NPA is the statement that flight in the H-V curve is governed by mass and not by height and speed; another is the concept of 'Category B operations' (or any other 'operating in Category' statement).

In the document, there are other strange statements - for example

Would someone like to explain that to me!

Suggestion 3 (which is really the crux of the matter) is dismissed with the following statements:

There are few who would not wish to see the H-V Diagram tranfered from the Limitations to the Performance Section. This would be no problem for those States who have a performance code (e.g. JAR-OPS 3 or EASA Ops) because protection for 'passengers'/'crew members' is already contained within the code. Operational regulations can permit risk assessment (limited exposure) and scaled (rules related to passenger numbers) or objective requirements and suitable methods of compliance.

That this will pass into regulations is not in doubt - offshore operations, in particular, need it. However, it would have been preferable either:

1. to correct the initial error of putting the requirement to apply the FM limitation into the 'law' - leaving compliance and alleviation to be achieved as it is with FAR 91.9 or JAR-OPS 3.005(c); or, better still
   
   
2. applying Suggestion 3.

This exercise is unlikely to make regulations clearer.

Mars

What a shambolic, rambling, innacurate prose. The NPA I mean - not Mars' ;)

Perhaps I am having problems because of my English comprehension; for example paragraph 2.6.2:

Firstly, what does the heading mean or imply? Is it a spelling mistake - should it be 'Applicability'?

It is important to understand the reason behind the 'NPRM 80-25' amendment to FAR 29.1 (no JARs at that time) that resulted in, what is in effect, quite a complicated set of clauses in the rule. Prior to 80-25, all helicopters certificated in the Transport Category had the H-V Diagram as a limitation unless a specific alleviation was sought from the FAA (each an individual application).

During the late 70, it became evident that Part 29 helicopters (Transport Category) were not only being used for passenger transport but were increasingly in demand for utility tasks; it was clear that for such tasks (Aerial Work) it was not necessary (nor was it possible) to retain the HV diagram as a limitation. A comprehensive proposal was put forward in NPRM Notice No. 80-25 to provide differentiation between Utility and Passenger Transportation along with appropriate standards. Adopting the philosophy applied to fixed wing aircraft in Appendix A to Part 135 (and using a similar justification), it was proposed to retain the higher standard only for the carriage 10 or more passengers.

However, because of the high cost of production and operation of helicopters this distinction could not be ‘hard’; it was clear that helicopters could (and would) be configured for both utility and passenger roles. In recognition of this, Part 29.1 was re-constructed to permit both Category A and Category B standards to be applied to a single helicopter type. The practical result of this dual certification was not a variation in the build standard for the helicopter type, but:

1. the removal of the HV diagram as a limitation; and
   
   
2. the removal of the requirement to provide most of the performance data

when the helicopter was operated in the Utility Role.

However, to ensure that this easement was not abused, Part 29.1(b) contained a clause requiring the provision of a supplement when the helicopter was being used in the Utility Role:

What the clauses to the rule made clear however, was that whenever the helicopter was in the 10 seat configuration, the H-V Diagram applied as a limitation.

So, back to the original quotation and the second paragraph:

Is my understanding correct that for a helicopter with a MCTOM of more than 20,000 lbs and 10 or more seats the H-V Diagram remains a limitation?

If not, why not?

Mars

Perhaps some basic information would be of assistance.

Helicopter certification is split between Parts 27 (small/normal) and 29 (large/transport). The mass break is at 3,175 kg (7000 lbs). All helicopter with a mass exceeding 3,175 kg must be certificated in accordance with Part 29. (We will return to Part 27 and Category A later.)

Large/Transport helicopters are certificated to Category A or Category B (or in some cases both) in accordance with their mass and passenger seats – the breaks for these Category divisions are: mass greater than 9,072 kg (20,000lbs); passenger seat of 10 or more (as stated in a previous post less than 10 seats is regarded as ‘utility’ and 10 or more as ‘passenger transportation’).

We will not dwell on the build standard but those helicopter with mass greater than 9,072 kg (20,000 lbs) and/or for ‘passenger transportation’ always have to satisfy the Category A requirements of Subparts C, D, E and F. That leaves the helicopter with a mass of 9072 kg or less and nine or less passengers which can be certificated to Category B.

Helicopters with 10 or more passengers seats have the H-V Diagram as a limitation and have to provide Category A performance data: for the helicopter in excess of 7,092 kg it is the full suite; for the helicopter of 7,092 kg or less it is the second segment climb performance (which is basic PC2 performance requirement).

Note: Helicopters operating in PC1 have to have the full Category A data suite – including those with a mass of 3,175 or less. As all helicopter have to meet the PC1 requirement when 200ft above the take-off/landing site, it is expected that they will have the full data suite.

If a helicopter is certificated in both a ‘utility’ configuration (i.e. less than 10 seats) and a ‘passenger transportation’ configuration, separate operating limitations are required – these can usually be found in the Flight Manual as a ‘9 seat Supplement’. Such a supplement usually states that the H-V Diagram is no longer a ‘limitation’ but is performance information.

When operating offshore (and occasionally onshore) in the ‘passenger transportation’ configuration (10 or more seats) and not flying within a Category A procedure, it is likely that there will be excursions into the H-V curve. Knowing that is the case, both JAR-OPS and Part 91 provided alleviation (for JAR-OPS that extended beyond over-water operations). That could be done because the requirement to apply the Flight Manual limitations, was contained in the (same) regulation and not in the Law (EASA Essential Requirements).

Having made the basic error of putting the requirement to apply the Flight Manual limitations in the Law, EASA had to remove the alleviation (taken from JAR-OPS 3) from the draft EASA OPS. The NPA proposes a (very complex and convoluted) method under which the H-V limitation can be circumvented. Clearly this solution is driven by expediency in that it does not have to tackle the basic problem (an attempt to regulate operations from a certification code) or address the error made by putting the Flight Manual limitation within the Law.

The intent of Part 29.1 is to provide a method of permitting two types of operation with one type of helicopter: the first is ‘passenger transportation’ – for which Category A procedures and data are provided in order to permit the highest standards to apply; and the second ‘utility operations ‘ - when such procedures and data are not required to be provided and alternative standards are permitted (thus removing the necessity to establish Category A procedures – quite a lengthy and costly exercise).

Thus we have the first ‘imperative’ of the rule: when operating with ten or more passengers, procedures and data will be available and flight inside the H-V curve is prohibited! No amount of obfuscation or misinterpretation of the rules can disguise this imperative.

However, NPA 80-25 made clear that the change in applicability was an opportunity for manufacturers to broaden the use of their helicopters by providing for both configurations in a single type; this required a second intent to be enumerated in Part 29.1(b)! When a manufacturer wished to provide for both types of operation – ‘passenger transportation’ and ‘utility’ – the distinction between them had to be made clear by the provision of “different operating limitations for each category”. As explained previously, this is usually achieved with the use of a ‘9 seat RFM Supplement’.

When a helicopter has been manufactured and certificated for both ‘utility’ and ‘passenger transportation’, it has met the higher build standard, the RFM has the applicable Category A procedures and data, and the H-V diagram is a limitation. The principle content of the 9 seat supplement therefore is the provision of a derogation from the H-V diagram.

Under the JAA/EASA, there is no compulsion to apply the Category A procedures unless Performance Class 1 operations are mandated (and even then, requirements are objective and alternative procedures can be used). However, under the FAA regulations, this is not so clear. This is because the definition of Category A differs between the two Authorities. The two definitions are - for the FAA:

and, for the JAA/EASA/ICAO:

As can be seen from the JAA/EASA/ICAO definition, for operations in Performance Class 2 any profile can be utilised providing there is no flight through the H-V curve. (As a matter of interest, the Category B profile mandated under Part 29 also requires flight outside the H-V curve.) In Performance Class 2 there is no compulsion to apply any profile contained in the RFM; in Pure Performance Class 2 if there is an engine-failure, a safe-forced-landing is required (out of the H-V curve and over an adequate surface); in Performance Class 2 with exposure, the condition of a safe-forced-landing are waived for a limited period.

However, when operating with ten or more passengers, the H-V diagram is a limitation and, when operating Performance Class 2 with exposure, the derogation provide by Appendix 1 to JAR-OPS 3.005(c) is required.

Up to the time that EASA removed the JAR-OPS 3.005(c) provisions (requirement and alleviation) from the operational regulation, there was no doubt about the intent of the 29.1 – all of the North Sea fleet had been (as required by the operational regulations) certificated in Category A and were operating with exposure.

Clearly a resolution is required but not one that ‘hacks’ the operational code and provides some bizarre interpretation of the certification code.

The least disruptive (in the sense of the negotiations that will be required between the FAA and EASA) would be to amend the Basic Requirements and re-introduce the mechanism for specific alleviation. The best solution would be for Authorities to accept the realities of operations, remove the H-V diagram as a limitation, and have it as information.

That the latter solution is difficult to achieve is because the FAA have never been able to regulate performance with the operational requirements (as they have for fixed-wing) and have to resort to doing so from the certification code.

Jim

Jim,

I found EASA NPA 2014-19 to be a difficult read. Then after reading your comments and considering the intent of the NPA expressed in the executive summary, I find myself asking the (possibly dumb) question…wasn’t this issue adequately addressed previously via JAR-29 and JAR-OPS 3? Does this issue arise because JAR-29 and JAR-OPS 3 did not migrate word-for-word into CS-29 and EU OPS?

HT

HT, that's how I understand it.

HeliTester,

With respect to Part 29 (FAR 29 and CS-29); this is a substantially harmonised document with no differences in the text that is being discussed in the NPA (or on here). EASA are proposing a slight change to CS-29.1 that is insignificant to the problem in hand but will take CS-29 out of harmonisation with FAR 29. Those changes are 'cosmetic' and have no substantial effect on the 'intent' of Part 29.1.

Yes, as previously stated, the alleviation that was established by Part 91.9(d) was copied over to JAR-OPS 3, incorporated in Appendix 1 to JAR-OPS 3.005(c), and widened slightly to include all operations with exposure.

When JAR-OPS 3 was transposed to EASA OPS, the alleviation was copied across verbatim. When the draft was submitted, EASA lawyers removed the alleviation stating that the Essential Requirements could not be alleviated from within the Operational Regulations. The removal of the alleviation resulted in the challenge to the effect that offshore operations with 10 or more passengers would be placed outside the law - i.e. the majority of North Sea Operations! There was no response from the lawyers.

The prevailing mindset in the NPA is that 'operations' are performed in in ‘Category A’ or ‘Category B’; this can be seen in the narrative of paragraph 2.1.2 of the NPA:

The reason it was not approached by the JAA was because the ‘helicopter operations committee’ understood extremely well the distinction between a ‘helicopter’ that was certificated in Category A and Operations in Performance Classes 1 and 2. Knowledge that now appears to be lost to EASA.

In fact what certification in Category A ensures is a build standard, limitations, and the provision of performance procedures and data; how/when those procedures and data are used and how helicopter is subsequently operated is a matter for the operational requirements.

When it comes to the critical point of the NPA; there is no effective (legal) difference between the text of Appendix 1 to JAR-OPS 3.005(c):

and CAT.POL.H.300

Except the JAA extract is direct and to the point and the EASA extract is not (they both provide a derogation from the limitation of the H-V Diagram when operating a helicopter with 10 or more seats).

The following extract from the AMC to 300 is also extremely badly written (mixes mass and weight, appears to align the H-V Diagram with mass, and makes little sense). It also appears to relate the ‘available take-off and landing area’ with the ‘FATO’ (which cannot be the case with exposure).

I have no wish for this to be a monologue or dialogue but it is an opportunity to provide information that is not generally well known (because it is at the nexus of certification and operations).

As was previously stated, the NPA makes a great deal of the discrepancy in mass between Category A and Category B and the effect on the H-V diagram. With respect to all operations in Performance Class 2, the maximum mass is given by the requirement (in the operational regulations) to meet the second segment climb performance*. This mass is provided in the basic Category A WAT required in accordance with Part 29.25(a) - for each density altitude for which the Category A performance and procedures are based. The data that is required to comply with this requirement is specified in Part 29.67(a)(2) – required for all helicopters with 10 or more passengers seats (and, in accordance with current operational requirements, for all helicopter operating in Performance Classes 1 & 2).

* When PC2 operations with exposure are planned (flight into the H-V curve), the mass may be further limited by the requirement for an AEO OGE hover in still air; for some helicopters, this might be more limiting than the second segment climb requirement.

This may be esoteric but the outcome of this is that, even if they exist in the RFM, Category B masses are not permitted to be used; ipso facto, there is only one H-V diagram that applies, even if more than one is present (which is often not the case). The question of mass and the H-V diagram is a red herring – albeit extensively mentioned in the NPA. Incursions into the H-V curve are as a result of the (usually vertical component of the) take-off and/or landing manoeuvre – when operating outside a Category A profile.

I am conscious of this now becoming a monologue and I apologise for that; however, it is important that statements made in regulatory documents, such as NPAs, do not go unchallenged when they are incorrect or are based upon the author’s opinion – rather than fact.

I would like you to consider Suggestions 3 (which I have referred to before) and 6 but prior to this, I want to debunk one or two of the ‘facts’ in the NPA. In my previous post, I mentioned the lack of relevance of the take-off mass to this issue. The mass limits provided in the limitations section have to be provided in accordance with Part 29.25(a); these masses are derived from:

1. The maximum design mass (showing compliance with the structural loading conditions);
   
   
2. The highest mass as which compliance with each applicable flight requirement is shown;
   
   
3. For Category B rotorcraft with 9 or less seats the maximum weight/altitude/temperature (WAT) at which the rotorcraft can operate safely near the ground.

The maximum Category A mass is provided by a WAT curve that meets the second segment climb performance (modified, if required, by the maximum design mass). It should come as no surprise to find that the maximum mass for one of the larger helicopters used offshore is (almost) identical for Category A and B.

We find a similar situation with respect to the H-V diagram; if the maximum mass is identical for Category A and B, then the H-V diagram will also be identical – as evidenced in the RFM of the helicopter mentioned above. (The Category A H-V diagram is contained in the Limitations Section whilst the identical H-V diagram is in the Performance Section.)

With respect to Category B; hover performance IGE and OGE have to be provided as does the AEO climb and angle of glide. The most important element however, is the establishment of the take-off and landing profiles. These have to be shown to be outside the H-V curve providing, respectively, a take-off and landing distance. The take-off distance requires an acceleration below the bottom of the H-V curve, commencing the climb when past the knee; the distance is measure from the hover to the 50ft point.

You will immediately see the lack of any relevance of Category B masses and profiles to offshore operations. Let us now examine the two suggestions mentioned earlier:

Whilst it is correct that making this change would create a substantial difference between EASA and the FAA it would only be because, in the absence of other requirements, the protection that is necessary in a 10 or more passenger configuration would be removed from the FARs. However, when it is considered that this is already the case with offshore operations (by dint of the FAR 91.9(d) alleviation) the impact would only be felt for onshore operations with 10 or more passengers. With the exception of departure from an onshore base to offshore location, there can’t be too many other of those operations. If some scheduled transportation service were to be commenced, it could be forced to use Category A procedures by an OpSpec or some other regulatory device.

With respect to the last paragraph, it would not require the transposition from limitation to performance criteria, with the exception of the basic Category A WAT, they are already contained in the RFM Supplements – and would continue to be so. If it is being hinted here that provision of the Category A procedures requires the Category A H-V Diagram to be in the Limitations Section, we can put EASA’s mind at rest because of the statement in AC 29.53A(a)(1) Take-off: Category A:

Of course it has to say this because, there is no requirement for a Category A H-V Diagram in the Limitations Section if the Category A procedures are mandated in the RFM.

Proceeding now to suggestion 6:

Bearing in mind that the whole intent of this NPA is to circumvent a requirement in Part 29.1, it is incomprehensible that EASA have not used the precedent previously set; in Article 8 “Air Operations” of the Basic Regulation we find the following two paragraphs:

This would only require paragraph 4.a of the essential requirements to be amended as follows:

This would then facilitate a change permitting momentary flight through the H-V curve. Such a rule would be contained within the appropriate Implementing Rule and would not therefore be open to abuse. This would reflect the procedure the FAA used with Part 91.9(d).

Jim

“Oh what a tangled web we weave when first we practice to deceive!”

To continue:

The NPA, in seeking to circumvent the Part 29.1 requirement, muddies the principle that was established and agreed in ICAO Annex 6 and JAR-OPS 3 - shown in ICAO Annex 6, Attachment A, Chapter 2.1 as:

This principle, which was discussed extensively before it was incorporated into Annex 6 and JAR-OPS 3, was adopted because it was felt necessary for helicopters operating over a hostile environment to be constructed to the highest standard, fulfilling the build requirements of Category A (as described in AC 29.1):

The requirement for certification in Category A was seen as necessary for helicopters that were intended for ‘unlimited’ operations over an environment that would not have permitted a safe-forced-landing or would have resulted in casualties due to the environment - in the context of this NPA, offshore operations where Performance Class 2 is mandated.

The proposed text of CAT.POL.H.300 obfuscates this requirement by introducing the complication of certification in Category B (as was previously discussed, a requirement that was intended for utility operations with less than 10 seats, not passenger transportation):

The proposed text just adds complexity to a regulation where none is required.

If the amendment to paragraph 4.a of the essential requirements is accepted, all that is then required is the addition of a clause to CAT.POL.H.305 - meeting the original intent of Appendix 1 to JAR-OPS 3.005(c):

To recap then; the only changes that are required to the current set of regulations are:

1. The addition of the text “Unless otherwise determined in the implementing rule” to the start of paragraph 4.a of the Essential Requirements; and
   
   
2. The addition of new paragraph (b) above to CAT.POL.H.305.

All of the other changes proposed in the NPA, along with the badly written and unnecessary/misleading guidance, can be discarded.

Because the principle of this was already agreed and incorporated in JAR-OPS 3, the proposal can be contained in one or two pages and passed through as a formality.

Without the changes proposed above, the Limitation of the H-V Diagram will continue to apply to helicopters ‘with 10 or more seats’.

Jim

Unfortunately all proposals to change the Basic Regulation, as you suggest or otherwise, were met with flat refusal...

Steve,

You are absolutely correct that when this solution was first proposed in May 2013, it was reject out of hand. However, now that the EASA proposal has been published, the folly of that decision is clear for all to see.

When suggestion 1 is considered in detail:

It can be seen that the phrase "respecting the airworthiness limitation is an accepted general principle which should be maintained" is totally disingenuous in the light of EASA's attempt to circumvent the certification requirement of 29.1(c) and (e).

However, what is crystal clear is that none of the obfuscation that is contained in the NPA will alter the fact that for a helicopter with 10 seats, the H-V Diagram is a Limitation. This is evidenced in the RFM of one of the larger types in current operation.

Jim

Let’s summarise what has been said so far:

The Issue (world-wide):

The take-off from an offshore location when not flying in accordance with a Category A procedure under conditions where the headwind component is less than the value at the knee of H-V curve, will be subject to momentary flight through the H-V avoid curve (due to the height of the helideck above the surface).

Helicopters certificated under Part 29 and with 10 or more seats (Part 29.1(c) and (e)) are required to have the H-V Diagram as a Limitation in the RFM in accordance with Part 29.1517.

In Europe, helicopter operating in Performance Class 2 are required to be certificated in Category A: such helicopters, when certificated under Part 29, have the H-V Diagram as a limitation in the RFM (helicopters certificated under Part 27 Appendix C are only required to have the H-V Diagram as performance information).

States mandate compliance with the Limitations of the RFM (known rules are JAR-OPS 3.005(c) and FAR 91.9(a)).

Current Solution:

States alleviate operators from the H-V Diagram Limitation under limited and risk assessed conditions.
Approaching Problem:

From October 2014 compliance must be shown with EASA OPS.

Under EASA OPS, the requirement to apply the limitations of the RFM are contained in the Essential Requirements of 4.a.

EASA have stated that they do not wish to provide a method of alleviation from the Limitations of the RFM and have removed the intent of Appendix 1 to JAR-OPS 3.005(c) from the performance code.

Ipso facto offshore operations will no longer have alleviation from the H-V Diagram Limitation; this impacts upon those flight for which flight through the H-V Diagram is necessary.

Solution – Long Term:

Remove the H-V Diagram as a Limitation from the requirements of Part 29.
Solution – Short Term:

Provide alleviation from the requirement to apply the RFM Limitations under controlled conditions.
This will return the regulations to the status quo ante before EASA lawyers intervened in the transposition of JAR-OPS 3 to EASA OPS.

Other points that have been clarified in this thread:

Helicopter that are certificated in Category A have a build standard, appropriate limitations, and the provision of performance procedures and data. This build standard is directly related to flight over a hostile environment and for that reason is mandated for operations in Performance Classes 1 & 2.

A helicopter cannot be operated in Category A or Category B. Procedures/profiles under which flight is conducted are specified in the operational code of performance. The maximum mass under which flight can be conducted in Performance Class 2 is defined by the Category A take-off mass.

Even when operating with Exposure, the maximum mass is still provided by the Category A WAT.

Finally:

Category B has no relevance to operations in Performance Classes 1 or 2; its introduction into the narrative/solution contained in the NPA results from a lack of knowledge of the certification and operational requirements. Operations in Performance Class 2 never make reference to the Category B take-off mass or the Category B H-V Diagram.

Jim

unless things have changed, I was taught that if you have a Category A supplement in a Part 29, 110+ pax machine, the supplement says that the limitation of the H-V no longer applies when using this supplement...
The Category A performance and procedures obviates the need for the H-V as a limitation. (at least in N. America)
Have things changed and I didn't notice?

Shawn - by way of background.

One of the complicating issues of this particular problem is the multi-threaded nature of Part 29 - which refers backward and forward in order to avoid redundancy (if something is only stated once then referred to, any changes that are necessary only have to be made to a single location). AC 29-2C is used to clarify some of these complexities but the logic of the regulation does require that it be studied and understood.

(Please be tolerant and follow this through, the point comes at the end of the series of quotes.)

The requirement for the H-V Diagram data provision is contained in Part 29.87 – Height Velocity Envelope:

This applies equally to certification in Category A and Category B. It is Part 29.1517 which requires this H-V Diagram to be provided as a Limitation:

The requirement for the H-V Diagram as an operating limitation is described in Part 29.1583(f)

AC 29.1583 makes quite clear, in the final sentence of section (b)(8)(i), conditions under which an H-V Diagram can be omitted from the limitations section:
Category A procedures and profiles are designed and flight tested to ensure that they meet engine-failure accountability and achieve flight/touchdown within the ‘serviceability limit’ of the helicopter (when flown as published, and on/over surfaces/areas which have been established for the purpose). They are a precision tool!

The H-V diagram is (usually) flight tested at the extremes of operation to provide a single graph (in some sense the provision of a rule-of-thumb for safe operations). It is a blunt instrument!

As you can see from AC 29.1583, when flight is conducted within the prescribed Category A profile/procedure, the H-V Diagram has no relevance*. However, omission of the H-V Diagram in the Limitation Section depends upon the Category A procedures being mandated in the RFM (which they are not).

* As Shawn indicates, there should be a note to the effect that the H-V Diagram can be ignored when applying the Category A procedure but I am not certain that it is always there - if not present, it is an oversight by the manufacturer and the regulator. It is not good enough "being taught" it has to be available within the RFM!

Most of the Part 29 helicopters that we are discussing here are normally flown in Performance Class 2 (and that applies to North America as well as Europe); that is achieved: in Europe - for operations with more than 9 passengers and/or flight over a hostile environment, by mandating Performance Class 2; and, in North America - for operations with more than 10 seats, by requiring the Category A WAT and enforcing the H-V Diagram, in the RFM.

Jim

Jim:
As I thought. Thanks for clarifying (?) the situation a bit more. Most helicopters I know that have Cat A procedures have wording in the supplement that say the H-V chart can be avoided when using the Cat A profile.

“Thy will be done”!

I have been referred to a previous thread on this subject that started in 2004 and concluded in 2010. In that thread, I was optimistic that EASA had the resolve to remove, from Part 29, the requirement to have the H-V Diagram as a Limitation:

http://www.pprune.org/rotorheads/426...ml#post5926055

I guess what has disappointed me about the current NPA is the approach taken, not just the content of the proposal - although it can be seen from this thread that it results from a lack of knowledge of the substance and intent of the certification and operational requirements/regulations – but the process of its provision.

As must now be clear to all who have taken the time to read and understand the intent of Part 29.1 (or accepted the central message of this thread), the two solutions (short term and long term) were the only ones that could have worked. This fact had been established for quite some time and, shortly after the formation of the working group (RMT .0132 & RMT .0515), an independent information paper was produced. This paper provided background to the changes to Part 29.1 that resulted from NPRM 80-25, the regulatory ‘trail’ for the H-V Diagram as a Limitation, and possible solutions. This was passed to EASA but they did not acknowledge or comment on it.

To the majority of the WG (one remained un-contactable and another supported the EASA position unquestioningly) the facts were incontrovertible and they made this clear by email. Projected meetings of the WG were cancelled and EASA (as they do when faced with opposition) continued with their proposal ‘in-house’. This was turned down by the (same) majority of the WG but EASA continued and produced NPA 2014-19. It is not clear that the proposal was seen by the WG before it was finalised and attached to a letter, dated 25th July, sent to the required regulatory committees and parties.

Interestingly, the letter states that “…once the regulatory changes are in effect, penetration of the H-V envelope when operating according to CAT.POL.H.305 approval can only be performed using helicopters with a Rotorcraft Flight Manual in compliance with the amended CS-29*. Operators should consider requiring the manufacturers to ensure such compliance for the specific helicopters.”

* That is, not in compliance with FAR 29.1.

Jim

JimL makes a very compelling argument for EASA OPS to mirror JAR-OPS-3. Because FAA has no operational performance requirements for helicopters (and likely won’t have in the foreseeable future), shouldn’t EASA’s short term goal be to only address the operational issue and not risk throwing CS-29 and FAR-29 out of harmonization, or invalidating existing operational performance rules after 28 October 2014. That JAR-OPS 3 has already made the necessary accommodation for Europe makes me wonder what can possibly be gained by reinventing the wheel. Helicopter operators and OEMs understand the existing rules and have provided the necessary operational procedures and supporting performance data to conform. Will recompiling the rule change the way and the payloads at which anyone actually operates? Could recompiling the rule cause the operators and OEMs to have to recompile their existing operational procedures and performance data? If so, at what cost? Will recompiling the rule make PC2 operations any safer than they are now?

The long term goal of removing the H-V diagram as a limitation via changing CS-29 (which must be an enormous rulemaking effort) could then be pursued with less disruption to the operators.

Thanks HeliTester - let's hope your sage words reach the ears of EASA.

With respect to Shawn's post on the H-V Diagram and Category A procedures; I was looking to see if there was guidance on what a statement to that effect might contain - I can't find any (and flight manuals that I have recently seen do not have any such statement). What I have found is guidance contained in AC 29.79(a)(9) with the following text:

(for those who know the rule numbers, 'Limiting Height-Speed Envelope' changed to 'Height-speed Envelope' after Amendment 29-38 and moved from 29.79 to 29.87; the guidance remained in place. This was quite logical as the H-V Diagram ceased to be a limitation at 29-21 when 29.1517 replaced the intent and limited the requirement only to Category A.)

Interestingly, immediately after this paragraph is another which impacts directly on the content of EASA NPA 2014-19 and, as shown already, further undermines the basis for their proposal:

The limitation clause (1) at 20,000 lbs does not accord with Part 29.1(d) unless an assumption is made that this clause actually mandates the build standard of Category A and only alleviates from the requirement to provide performance data and have the H-V Diagram as a Limitation. That has always been my reading of the intent of Part 29.1(d) and associated guidance.

Jim

Cat A Profiles - what now?
 

Hi Jim et al

Where does all this juggling with rules and regulations leave the poor old TRI/SFI trying to teach Cat A profiles that take the aircraft into the HV curve? Seems that the old 'get out' of saying that in these cases breaching the limitation is acceptable because the profile has been 'certified' is no longer available.

How am I supposed to deal with this anomalous and ambiguous puzzle?

G. :{

Hi Geoff,

As shown in my previous post, the flight tests that establish the trajectory of the Category A procedure/profile demonstrate a safe path through the H-V Diagram.

(That also applies to the Category B take-off procedure contained in the RFM.)

The only point of debate (with Shawn) was if, and where, that is stated in the RFM.

Jim

Take off and landing profiles
 

Jim

Does all this make it problematic when a large helicopter is used for 'Utility' work and has to operate from sites that cannot comply with either the published Cat A or Cat B profiles. Does EASA allow alleviations for 'aerial work'?

The one question that is always begged by these academic arguments and debates is that in the real world sites that are 'compliant' i.e. properly surveyed, are almost non existent and the very nature of most public transport (non airport) operations and all Cat B operations take place from unsurveyed (non-compliant) sites

Lest we forget offshore locations/vessels do not qualify as 'surveyed' in the 'obstacle' context by virtue of the changeable nature of their structures and environments.

G.

Hi Geoff,

This is a debate only about passenger transportation in Commercial Air Transport operating in accordance with Performance Class 2. The Performance Classes are not applicable to the ‘utility’ configuration or ‘Aerial Work’.

The larger helicopters configured in the ‘utility’ configuration (i.e. with less than 10 passenger seats) are appropriately addressed by Part 29. They are constrained only by the Category B mass which has to be provided as a limitation in accordance with Part 29.25 and mandated by Part 29.1519 (as is the Category A mass). There is no compulsion to use the Category B profile or be constrained by the H-V Diagram (the Category A and B H-V diagrams are almost always identical); any constraints on the operation will only be those contained in the regulations of the State (which is not part of this discussion).

Performance Class 2 was provided exactly for the Commercial Air Transport (off airport) operations that you have mentioned. It was adequately described in JAR-OPS 3 along with Exposure and the necessary alleviation from the H-V Diagram (which is a limitation for for Part 29 helicopters when: configured with 10 or more seats; or when certification in Category A is mandated under the operational regulations – as it is for Performance Class 2).

As explained in earlier posts, when transposed to EASA OPS the alleviation from the H-V Diagram, described above, was removed by the lawyers because EASA had ‘replaced’ the requirement to apply the RFM limitations from the operational regulations to paragraph 4.a of the Essential Requirement – so making it law.

The correct solutions (short term and long term) to this dilemma are contained in post #14 above.

Jim

General

In order to understand how NPRM 80-25 effected the certification of Category A and Category B rotorcraft, it is necessary to examine what changed and why. There were two substantial changes: one concerned the applicability of the H-V Diagram as a Limitation; and another the certification and operating criteria with respect to mass and numbers of passengers carried.

In addition the upper limit of 20,000lbs, for permitting the Operating Limitations of Category B, was removed.

Changes that Affected the Requirements for the H-V Diagram

The substantial change to Part 29.1 was made effective in 1983; before that time, although multi-engine rotorcraft could be certificated in Category A and/or Category B, they both had to have the H-V Diagram as a Limitation.

In NPRM 80-25 a number of changes were made to ensure that, whilst Category B no longer required the H-V Diagram as a Limitation, it was still required for the definition of the Category B take-off and landing WAT limit conditions. The necessary changes were made (in this amendment and subsequent ones) to partition the requirements such that all cases were covered .

The following amendments were made:
In spite of the intent being made quite clear in NPRM 80-25, there is still confusion, in some certificating authorities*, as to when one or both of the requirements (information and/or limitation) have to be met.

* Evidenced in the ESF awarded to the AW189 by EASA.

It is understood that in all cases, 29.87 has to be complied with – in addition:
The requirement of the H-V Diagram as a Limitation is bound to two imperatives:
Jim

Cut to the quick Jim....
 

.... and tell us what the impact of this debacle is likely to be on the community of fine upstanding helo operators whose only aim in life is to make a crust whilst staying within the law?

G :}

Hi Geoff,

None whatsoever if the status quo ante is preserved.

Let me explain why this thread is being kept alive: the harmony between certification and operations (Part 29, FAR 91 and JAR-OPS 3) provides a balance, on the H-V issue, which has endured – for FARs since 1983 (the significant amendment of Part-29) and for JAR-OPS 3 since 1998. It is in the best interest of the industry that FAA and EASA maintain a harmonised Part 29.

This balance was potentially put in jeopardy with the provision of EASA Essential Requirements which placed compliance with the RFM Limitations in Law rather than Regulations. As previously explained, this was noted when JAR-OPS 3 was transposed to EASA OPS because it invalidated the ‘partial and controlled’ alleviation from the H-V Limitation (the alleviation was removed, by lawyers, from the draft EASA OPS).

Removal of the alleviation invalidated Exposure in offshore operations (CAT) because it was placed outside the ‘Law’. The best solution is a continuation of the status quo as outlined in post #14; a tried and tested solution which preserved harmonisation in Part 29 (FAR 29 and CS-29).

During the time that the EASA working group were considering solutions, AW applied for, and were granted, an EASA Equivalent Safety Finding (ESF) on the requirement to provide an H-V Diagram; this finding was not in compliance with the ‘rules’ - as shown in the post above (the AW 189 is certificated as a ‘Large Rotorcraft Category A and B’). The proposed ESF was commented to that effect but, in EASA’s response, a lack of knowledge/understanding of both the certification and operational requirements was shown.

Although proposals and CRD documents are published, the readers are far fewer than those on PPRune. PPRune is read extensively in the industry (including regulators); in the absence of access to discussion on these matters, PPRune provides the only opportunity to offer an explanation of the regulations and, more importantly, their intent.

It is only with this knowledge that an appropriate solution will be put into place.

Jim

Jim

EASA AW189 certification team has proved great competence and vision on this subject, unfortunately the H-V NPA working group has missed it completely.

The ELOS was only addressed to the different way of presenting the H-V envelope information and NOT whether to provide it or not provided it, in fact all H-V information is included in the AW189 RFM.

I want to clear some concepts that EASA Cert team has made very clear and agreed with AW proposal.

The H-V limitations applies to takeoff and landing profiles and HOGE conditions for Cat B certification and only for takeoff and landings profiles for Cat A.
Being (by rule) the H-V envelope/limitation only applicable to the type of surface where it has been demonstrated (that in all RFM is hard/runway type surface) this limitation can only be considered applicable to the published takeoff and landing procedures that are the only conditions where the H-V has been demonstrated.
Based on this it was considered compliant, considering the applicable CS29 rules, that H-V limitation was demonstrated.

AW has considered that the inclusion of the actual traditional H-V chart that was fully demonstrated as per the required rules, was of low operational values. AW proposed instead to provide what AW considered a much more valuable information that can be faced in real operations where "usually" very rarely a Cat B takeoff/landing profile takes place over a runway and all HOGE operations almost never occur over it. It was then considered to introduce in the performance section a fully comprehensive set of charts that provide Safe Vertical Rejects and Fly-Away performance WAT charts with an actual height loss data including wind/speed contribution. We wanted to tell the pilot what he can do to save the helicopter and not what he cannot do without telling what is a safe escape.

This was also corroborated by the fact that the traditional H-V information is only limited to one type of surface and therefore not applicable to any other operational surface.

For Cat A procedures, the WAT charts included in the limitations section have been demonstrated to be cleared of any H-V limitation.

I want to reiterate my thanks again the EASA Cert team for their collaboration in achieving a step forward towards a new vision in providing a better and more operational oriented RFM for these class of helicopters.

One more consideration: there are no H-V envelopes for helideck sites, it is impossible to comply with these rules for these surfaces, therefore there are no possible infringements of the H-V limitation. Even a takeoff profile that complies with the published H-V limitation, if carried out from an helideck, can be fatal.
The only safe way to operate from helidecks is to apply procedures with zero exposures, i.e. PC1.

Thanks Dino,

In order to provide a cogent response, it is necessary to unpick some of the elements of your post for discussion.

A Common Certification code

Part 29 (FAR 29 and CS-29) represents a harmonised certification code in the Western World. The acceptance of Type Certification among those States who use this code, depends upon a common view of what the code represents. Guidance is provided in a single advisory circular which, for historical reasons, has an FAA bias (reference to operational rules is primarily oriented towards the FARs). Where this guidance is not seen as sufficiently comprehensive, some States have chosen to provide additional material on methods of compliance (this uses the statement in AC 29.2C that it represents a method but not the only one).

Operational Rules

Operational rules are not harmonised (although ICAO does provide a common Standard); for some States, the certification code underpins the operational rules; for others, it can represent an unnecessary constraint on operational practices based upon risk management. The H-V Diagram represents one such case; in States without a performance code, it provides a moderating mechanism; in States with a performance code in compliance with ICAO, it constrains under circumstances where risk assessment permits finer control.

The H-V Diagram as a Limitation

The H-V Limitation is a clumsy device and, even in those States where it is required to underpin control of operations, it represents a barrier to some legitimate operations (offshore for example). For that reason, all States need a method of alleviation in these cases.

States with a performance code in compliance with ICAO do not require the H-V Diagram as a Limitation and, in the past, have moved to have it only as information. That this move is resisted is understood because the required changes to the operational code in some States would be seen as seismic by some stake holders. For that reason, FAR 29 has remain unchanged and control has been provided by alleviation in Regulations. This method is pragmatic because it retains a common view on the application of Part 29 whilst allowing flexibility in operations.

The Conditions of an H-V Diagram

The H-V Diagram defines an envelope of airspeed and height above the ground from which a safe power-off or OEI landing cannot be made. The flight manual should list any procedures which may apply to specific points (e.g. high speed points) and test conditions, such as runways surface etc.

The surface condition has relevance to the H-V Diagram only inasmuch as it represents a further limiting condition – i.e. a landing is not guaranteed in the case of an engine failure outside the H-V avoid curve if the surface conditions do not permit it. In ICAO, this additional factor is included in the definition of a safe-forced-landing – which consists of two elements:
Only the former is a condition of the H-V Diagram. Surface conditions are non-sequitur and have no place in the determination of compliance.

Requirements for Provision of the H-V Diagram (see post #24)

The requirement for provision of the H-V Diagram is represented in two rules: 29.1583 ‘Operating Limitation’, and 29.1587 ‘Performance Information’ – both have to be satisfied.

29.1583(f) points to 29.1517 which requires, for Category A rotorcraft, a Limiting height speed envelope to be established; this requirement can be set aside only if the Category A procedures are mandated. If they are mandated they have to be contained in the Limitations Section or referred to in the Limitation Section. To my knowledge, that is not the case with the AW189. If that were the case, all flights would have to be flown within the Category A procedures – including those offshore.

29.1587(b)(6) requires, for Category B rotorcraft, the provision of a height-speed envelope. The exception to this is if one is provided as an operating limitation – i.e. in compliance with 29.1583(f). If Category A procedures are mandated, then it is necessary.

Must a Rotorcraft that is Certificated in Category A Apply the Category A Procedures?

Whilst the WAT for each of the Category A procedures represents a limitation for that procedure, it is difficult to see how that represents a general requirement for all flights to be conducted in accordance with Category A procedures – including flights to helidecks. That is not a result with which the operating community would be happy.

Are Category A procedures mandatory?

Let us examine the rules/guidance - we start with the definition of Category A:
Because this (JAA) definition was provided after the Performance Classes were defined in ICAO and JAR-OPS 3, it is likely that the wording was deliberate. Capability does not imply an imperative, or compulsion, to use the Category A procedures.

The strongest signal is provided in the guidance in AC 29.1583(b)(8)(i) with respect to the relationship between the Category A procedures and the H-V Diagram as a Limitations:
There can be no misunderstanding of the intent of this passage; unless the Category A procedures are mandated, an H-V Diagram is required in the Limitations section. Ipso facto, if the H-V Diagram is in the Limitations section, the Category A procedures are not mandated (unless so specified in the Operational Regulations).

It is therefore concluded that certification in Category A does not imply that the Category A procedures have to be used!

Jim

JimL,

''The H-V Diagram defines an envelope of airspeed and height above the ground from which a safe power-off or OEI landing cannot be made."

I have read somewhere:

" ... or OEI landing is not guaranteed by the OEM."

Cheers

Thanks ATN. The text was taken verbatim from AC 29.79.

In some sense your additional text illustrates one of the problems. Category A and B procedures are provided in a strict test environment; the OEM has no knowledge over and on which surfaces, operations are performed. That is left to the operational regulations.

Jim

The rationale and intent of Part 29.1 and its attendant clauses has now been explained – hopefully, so all can understand the implication of the H-V Diagram in both of its forms as a Limitation and Information. Leaving aside the issue of the AW189, which appears to mandate the Category A procedures; it should not be inferred from my comments that the H-V Diagram as a Limitation is supported – it is not.

When NPA 2014-19 was published, comments had to be with EASA by the 27th October 2014 – which was one day ahead of the opt-out period for Air OPS (28th October 2014). As was indicated in the covering letter to States, there will be a bridging period between the end of the opt-out period and adoption of the amended rules.

The comment period has now been extended to 27th November 2014 and so the first priority of States becomes the necessity to address the impending (28th October 2014) problem of the ‘illegal’ penetration of the H-V Diagram for rotorcraft that have been certificated in Category A under CS-29 – i.e. most helicopters used in North Sea offshore operations.

Member States were advised that, in order to continue operations in accordance with the status quo (Performance Class 2 with Exposure), it would be necessary for each to grant an exception under Article 14(4) of the Basic Regulation.

The regulation goes on to explain that the agency shall assess whether the exemptions are less restrictive than the Community provisions. As a correctly constructed exemption is intended to preserve the status quo ante, it is unlikely that it would be questioned by the Community (or EASA as its agent).

In considering what this exemption might be, it is necessary to look for the key element that has resulted in this situation. It is Article 8(1) of the Basic Regulation:

Requiring compliance with Essential Requirement 4(a) of Annex IV:

In order to permit continued operations to the current safety level, a 14(4) exemption must therefore provide alleviation from Article 8(1) in respect of compliance with Essential Requirement 4(a) of Annex IV of that regulation.

The conditions of the exemption should be those which were extant in JAR-OPS 3 – as transposed to Air OPS. That is:
For operations in CAT.POL.H.420 – helicopter operations over a hostile environment located outside a congested area; no exemption is required because the limit of the number of passengers is six (and therefore could make use of the 9 seat Supplement – under Performance Class 3 either Category A or Category B certification is permitted): SPA.HEMS.125 – performance requirements for HEMS operations; also does not require an exemption because it operates under CAT.POL.H.305, which will, itself, be exempted.

Jim

"To raise new questions, new possibilities, to regard old problems from a new angle, requires creative imagination and marks real advance in science."

— Albert Einstein


:sad:

Tell us about the AW189 situation Jim...
 

So are we saying that the net effects of the new rule structure are that all 189 operations must be Cat A compliant, even offshore?

If that is so, and given that we have often pointed out the impossibility of meeting Cat A performance requirements in the offshore environment due to the deterministic nature of the regulation and the difficulties with the obstacle environment, then we have a bit of a quandary to solve.

On the one hand it appears we have to comply with Cat A Procedures but we can't because they require us to predict (prior to departure from land) a level of obstacle clearance at the offshore location that we are unable to provide due to the unquantifiable interactions of wind, turbulence and the dynamic nature of offshore obstructions.(moveable derricks, supply boats, crane/lay/work over barges, fitful winds and turbine exhaust pollution).

G. :confused:

This perhaps this should have gone onto the AW189 thread because the issue does not result from the NPA proposal but from the interpretation of the regulation/guidance that has been shown above. It does, however, reveal an interpretation of the use of Category A procedures that permeates NPA 2014-19 and, for that reason, here is as good a place as any to provide an explanation.

The configuration of the AW189 RFM is as a consequence of the Equivalent Safety Finding (ESF), or more accurately, from the interpretation that has been put on CS-29 by EASA and AW. In the ESF there is an implicit assumption by the author/respondent that certification in Category A requires Category A procedures to be used (which, as was explained above, is not correct).

The ESF against CS 29.1587(b)(6) was intended to permit AW to replace the H-V Diagram in the Performance Section of the RFM with two other graphs, ‘reject’ and ‘fly-away’. My comment on the AW189 thread with respect to this was; in principle, it was supported but, because the ‘reject’ graph did not extend to 8,300kg, it did not completely fulfil the function of the H-V Diagram. The requirement of the contents of an H-V diagram are specific:

The maximum Category A mass is 8,300kg, ipso facto the requirement is not completely satisfied by the ‘reject’ graph (although it, along with the ‘fly-away’ graph is welcome in assisting in the provision of Performance Class 2 profiles).

What the ESF did not do was to make a determination against the requirement of CS 29.1583(f) - to provide an H-V Diagram in the Limitations Section of the RFM. The two requirements are not synonymous (the H-V Diagrams are, of course, identical); although the provision of an H-V Diagram in the Limitations Section can be regarded as satisfying the requirement for one in the Performance Section, the opposite is not true.

For a Category A helicopter, there must be an H-V Diagram in the Limitations Section unless the Category A procedures are mandated. As far as I am aware, there is no H-V Diagram in the Limitation Section of the AW189 so, the assumption we must make is that Category A procedures are mandated.

Contrary to what Dino has said, in EASA there is a lack of understanding of the application of Category A to Operational Requirements and, it would appear, a lack of understanding of their own certification regulations and guidance with respect to the provision of the H-V Diagram.

The NPA totally ignores the principle of Part 29.1 that, if there are 10 or more seats, the helicopter must be certificated in Category A and apply the Category A Limitations (i.e. for Passenger Transportation). Additionally, if the helicopter is operated in Performance Class 2, it must be certificated in Category A (with all of the concomitant limitations). The FAA and JAA understood this and provided, in their operational regulations, an alleviation from the H-V Diagram under limited and controlled conditions (in the JAA, this applied only under an Approval for Exposure).

Mandating of Category A procedures is not welcomed because, as you have so correctly stated, they are not always possible (to comply with) in the offshore environment.

This is the problem with looking for absolutes in a world were very few exist. The HV curve is a great example - its a fundamentally inadequate piece of information for the environment where most helicopters operate (off airport).

It would appear there has been a problem created where none existed. Much effort will go into fixing it and everyone will congratulate themselves on a job well done when a solution is agreed. The end result is a zero sum outcome that achieves nothing but confusion and uncertainty for those who have to operate these things in the meantime.

With the reliability of modern turbines, the HV chart should only be guidance material, particularly for multi engine aircraft. Our regulations and regulators (and to some degree industry) are still focused on yesterdays problems... trying to shoehorn rapidly evolving operations and aircraft into a 1970's regulatory environment and mindset. I like AW's preemptive action on this for the 189 and hope that others will follow.

For States which have a Performance Code in compliance with ICAO Annex 6, regulation of performance is achieved with use of the ‘Performance Classes’ and by controlling limited exposure (outside these classes) with risk assessed procedures which include a safety target, mitigating conditions and limits on passenger numbers. For these States, the retention of the H-V Diagram as a Limitation in Part 29 is an unnecessary constraint on operations.

For helicopters employed in offshore operations, most offshore take-off and landings penetrate the (traditionally presented) H-V avoid curve – this represents more than 50% of all take-off and landings ever performed with these helicopters. The probability of an engine failure leading to a catastrophic event for offshore take-off or landing with exposure is about 5 x 10-8 (1:20,000,000) - for operations outside of a Category A or Category B procedure.

Not all States using Part 29 have a Performance Code; those which do not, rely upon the ‘conditioning’ clauses of Part 29.1, and retention of the H-V Diagram as a Limitation, to provide (operational) control of performance within the flight manual. This results in a situation where States rely upon alleviation from the Limitation of the H-V Diagram when operating offshore with more than nine passenger seats.

In the modern era, all helicopters operating offshore in Europe are certificated in Category A and B – i.e. they all comply with the Category A ‘build’ standard. Dual qualification permits these helicopters to be employed in ‘utility operations’ (aerial work) as well as ‘passenger transportation’ (commercial air transport – offshore and onshore).

All Category A and B procedures (from Subpart B ‘Flight’ of Part 29) ensure that the helicopter can tolerate an engine failure on take-off or landing: for Category A, by providing profiles that have demonstrated engine-failure accountability; and, for Category B, by mandating take-off and landing profiles that remain clear of the H-V avoid curve.

All dual qualified helicopters have a ‘capability’ (as expressed in the EASA definition of Category A) of using the Category A or Category B procedures; helicopters cannot be ‘operated’ in Category A or Category B they have to be ‘operated’ in accordance with the Performance Classes (or with exposure) – i.e. it is the performance code that determines which Performance Class has to be employed. Certification in Category A does not mandate the use of the Category A procedures.

The significant intent of the changes to Part 29.1 as a result of NPRM 80-25, was to remove the H-V Diagram as a Limitation for ‘utility operations’ (aerial work) and, for simplicity, to bind that to a seating configuration of less than 10. Offshore operations (or any Commercial Air Transport) should not be regarded as ‘utility operations’; for that reason, more sophisticated methods of regulation need to be employed.

The one inescapable fact that results from Part 29.1 is that unless Category A procedures are mandated, the H-V Diagram is a Limitation when more than nine passengers are carried.

In NPA 2014-19; the proposed amendment to CS-29 – particularly in operations with more than nine passengers – is legally questionable, undermines the logic and intent of Part 29.1, and introduces doubt and unnecessary complication into the certification process; in order to preserve a world-wide harmonised code, it should not be undertaken. The introduction of Category B to Performance Class 2 requirements adds complications to the code under circumstances where the sole intent is to avoid the H-V Limitation (i.e. to circumvent CS-29.1 and CS-29.1517).

In the short term; a much simpler/better method would be to preserve the status quo (in Europe and world-wide) by: prepending an enabling clause into Subparagraph 4.a of the essential requirements; and, by adding an alleviating clause into CAT.POL.H.305. The decision not to proceed with this option should be revisited, or justification - acceptable to interested parties - provided.

In the long term; there is need for discussions between the Certificating Authorities about the removal of the H-V Diagram as a Limitation from Part 29.

Jim

The Nexus between the Certification and Operational Codes

It is axiomatic that operations should not be regulated from within a certification code; operations are dynamic and have to adapt to changing demands, whilst a certification code is (and has to be) somewhat static.

The seat of the ‘H-V Limitation’ issue results from a situation where some States have not provided a performance code in compliance with ICAO Annex 6, Part III, Chapter 3.1.1:
Hence, undue reliance has had to be placed upon limitations within the certification code to constrain operations; for obvious reasons, this method results in a coarse device with a singular granularity which has required alleviation to be provided for offshore operations. Using a code of performance permits a much finer granularity with risk assessment at its core.

The absence of a code of performance results in a situation where operations are (erroneously) described (by airworthiness personnel) in certification terms. The implied logic of NPA 2014-19 is that operations are performed either using the Category A or Category B procedures when the fact is that helicopters are certificated in Category A and/or Category B and are operated in Performance Classes 1, 2 or 3.

Note 1: Following the logic and intent of NPRM 80-25, the phrase ‘Category A operations’ in the AC 29-2C guidance is intended to refer to ‘passenger transportation’ rather than ‘utility’ operations (aerial work).

Note 2: If compliance with Category B procedures was required, then the fulfilment of CS 29.63 would require a defined take-off surface over which a landing can be made safely at any point along the flight path if an engine fails (not exactly in line with an offshore take-off).

Provision of procedures in accordance with Category A or Category B provides a capability (the term used in the definition of Category A) which can be employed in operations. The requirements for operation in the appropriate Performance Class is described in the code of performance; that there is no direct correlation between the certification Categories and Performance Classes is of little importance. Thus, Performance Class 2 provides the flexibility that is required, for operations other than from airports, with a Category A mass without the constraints of a Category A procedure but with appropriate levels of safety set in accordance with the risk profile of the operation.

It would be much better if H-V Diagram as a Limitation was removed. However, it is necessary to recognise that a situation exists where some (important) States, in the absence of a code of performance, require the certification code to contain operational restrictions. In the short term, a harmonised certification basis is more important that the fact that a directed alleviation from the Flight Manual Limitations has to be provided.

What is essential, is that airworthiness and operations personnel understand the nexus between certification and operations and share a single view of how they interact. What can be seen from the narrative of NPA 2014-19 is that more time needs to be set aside so that all personnel can read into and understand the underlying philosophy and concepts of the code of performance. Misconceptions enshrined in the NPA such as “Flight regimes subsequent to DPBL and prior to DPATO are therefore not within the scope of Category A according the definitions of Annex 1” have to be corrected.

Specifically, it must be made clear that “capable of operations using take-off and landing data…” does not result in an imperative to use such data – only the limitations have to be observed! The ICAO/JAA/EASA definition of Category A differs from the FAA version which contains the words “utilizing scheduled takeoff and landing operations...” a difference in the ICAO/JAA/EASA definition that was deliberately phrased at the time when the Performance Classes were being defined and incorporated into ICAO Annexes 6, 8 and 14 by the Heliops Panel.

The confusion of the NPA is exemplified in Paragraph 2.6.3 - CS 29.1587 Performance Information:In a single paragraph we have the nub of the problem; the text implies that ‘when operating according to Category A’ means using the Category A procedures. As has been shown above, Category A provides a capability that may be used in support of a Performance Class – it is not an imperative. This is confirmed by the last paragraphs of AC 29.1583(b)(8)(i) which states that the H-V Diagram can only be omitted from the Limitations Section if the Category A procedures are mandated:There can be no misunderstanding of the intent of this passage; unless the Category A procedures are mandated, an H-V Diagram is required in the Limitations section. Ipso facto, if the H-V Diagram is in the Limitations section, the Category A procedures are not mandated (unless so specified in the Operational Regulations).

Jim

If I may further seek your indulgence .

Understanding the difference between Limitations and Performance Information

In order to understand the difference between limitations and information it is necessary to examine two rules – CS 29.1583 and CS 29.1587. Firstly, we have to look to CS 29.1583 (‘Operating limitations’) to see what is mandated: for category A rotorcraft it is the maximum mass (in accordance with CS 29.25, CS 29.1519 and CS 29.1583(c)) and the H-V Diagram (in accordance with CS 29.87, CS 29.1517 and CS 29.1583(f)).

It is only when we look to CS 29.1587 (‘Performance Information’) that we find the Category A: airspeeds; techniques; rejected and take-off distances; landing data; climb data; and hover performance.

It is important that the difference between limitations and information is observed and understood.

If it is considered that, for an aircraft certificated in Category A, no departures/arrivals should be conducted outside of the profiles/procedures contained in the Category A Supplement of the RFM, passenger operations would be constrained in an unacceptable way. Particularly when a limited number of procedures/profiles are defined and operations are not always conducted from airfields.

As an example, look at the clear area procedure of the AW 189: this requires a ground run to 25 kts ground speed to comply with the procedure. One difference between Performance Class 2 and Performance Class 1 is that, whilst Performance Class 1 requires a surface on which a ‘reject’ can be carried out to the ‘limit load’ (also known as the serviceability limit) of the undercarriage (CS 29.725), the ‘safe-forced-landing’ of Performance Class 2 permits the ‘reject’ to be carried out to the ‘ultimate load’ (CS 29.727).

Note: ‘safe forced landing’ means an unavoidable landing or ditching with a reasonable expectancy of no injuries to persons in the aircraft or on the surface.

Compliance with Performance Class 2 is permitted over a surface which would not permit a ground run but, in the event of a power unit failure, would be suitable for a safe-forced-landing (for example a rough grass surface).

There appears to be no good reason why the clear area procedure could not be conducted with a normal departure from the hover; however, to comply with the Category A Supplement, it must be flown as published (with a ground run). Operations in Performance Class 2 would permit a hover departure mirroring the Category A procedures (but without ground run) at 8,300kg. However, this appears to be precluded because the ‘reject’ graph (substituting for the H-V Diagram) does not permit a take-off mass in excess of 7,900kg. (The gap in the upper end of the ‘reject’ graph could easily be filled by providing an appropriately constructed mini H-V Diagram.) The situation is exacerbated by the lack of a Category A WAT in the Limitation Section in compliance with CS 29.25, CS 29.1519 and CS 29.1583(c).

Note: the category A WAT (common to all Category A procedures) is one which is constructed to show compliance with CS 29.25(a)(2) and CS 29.67(a)(2).

Jim

Conclusion

The purpose of NPA 2014-19, is to provide alleviation from the H-V Diagram as an Operational Limitation by: amending CS 29.1; providing new AMC 29.1 and AMC 29.1587(b)(6); amending CAT.POL.H.300; and providing new AMC1 CAT.POL.H.300. The proposed solution is complex and relies for achievement of its objective in circumventing the intended requirement to apply the H-V Diagram as a Limitation when the aircraft is certificated as a Category A rotorcraft*, or when there are more than 9 passenger seats.

* Not 'certificated in Category A' but 'certificate as a Category A Rotorcraft'.

One inescapable fact that results from Part 29.1 is that, unless Category A procedures are mandated, the H-V Diagram is a Limitation when more than nine passengers are carried. In effect the changes proposed in NPA 2014-19 are an attempt to redefine the intent of CS 29.1 as established in NPRM 80-25 – which addressed the separation of ‘utility’ operations from ‘passenger transportation’.

Removal of the H-V Diagram as a Limitation requires more than just statements in guidance; the solution contained in NPA 2014-19 represents a substantial challenge to the intent of CS 29.1 – i.e. the requirement to apply CS 29.1517 for ‘passenger carriage’. This intent was explained/justified, when changes were made to the rule in NPRM 80-25. The proposed change to the intended function of 29.1 is unlikely to go unquestioned as it represents a breach in harmonisation under circumstances where regulation of performance in some States, depends upon the intended application of the rule.

The current method of alleviation, used in FAR 91.9(d) and Appendix 1 to JAR-OPS 3.005(c), is preferable because it is completely transparent and does not require a change in the intent or wording of CS-29.1; it preserves the status quo – both with respect to offshore operations, and harmonisation with the FAA. (The FAR/JAR solution was not transposed to EASA OPS because the requirement to comply with the Limitations of the RFM was placed in the Basic Regulations rather than in the Implementing Rules.)

The statement in NPA 2014-19:

cannot go unchallenged. Of course it is possible to make the changes shown below; in fact the solution, proposed in NPA 2014-19, shows less respect for the airworthiness code and the limitations that are represented in CS-29.1 than the current solution with its transparent, specified and limited alleviation backed by risk assessed procedures. The use of semantics to circumvent the intent of CS-29.1 will not provide the clarity that is achieved by the current alleviation; it also introduces a question mark into the world-wide interpretation of Part 29.1, and 29.1517 for States which rely upon the current intent to achieve regulation of operational performance.

A much simpler solution would be to amend the Essential Requirements to permit the well understood and measured solution that is currently used in FARs and JARs (the status quo ante). This could be achieved by using wording currently employed in the Basic Requirement for permitting alleviations; thereby facilitating the smallest change to EASA OPS whilst remaining completely transparent.

Article 8 – Air Operations, paragraphs 2 and 3, already contain precedents for the provision of a solution by having as the introduction to their text the phrase “unless otherwise determined in the implementing rules” – as follows:

All that is required is for Paragraph 4 ‘Aircraft performance and operating limitations’ - specifically subparagraph 4.a of the essential requirements to be be amended as follows:
This would then permit the addition of a clause (c) into CAT.POL.H.305 ‘Operations without an assured safe forced landing capability’:
That would leave only the editorial changes to be made.

Jim