Helicopter Height-Velocity (H-V) limitations

[Mars]

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

"...the H-V envelope is a limitation only when operating according to Category A..."

Would someone like to explain that to me!

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

Change CS-29 to move the H-V envelope from the limitations section to the performance section in the AFM.

Moving the H-V envelope from limitations to performance criteria goes against the Category A certification philosophy and would be a non-trivial change. Furthermore, changing CS-29 in such a way would create a substantial difference with the similar FAA certification requirements, and may impact on type-validation and acceptance by foreign authorities [presumably the FAA].

It should also be noted that to obtain the expected effect of the suggestion, Category A take-off and landing weights would also need to be required transposed [their wording] from limitations to performance criteria. This would go against the regulatory desire and trend towards encouraging more powerful helicopters with full Category A engine failure accountability.

In the Agency’s view this suggestions cannot be further considered.

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

[212man]

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

[Mars]

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

2.6.2. CS 29.1 Availability

It is proposed to change the paragraph to ensure that multi-engined helicopters may be certified both Category A and Category B with appropriate and different operating limitations for each category.

For helicopters with MTOM greater than 9072 kg and 10 or more passenger seats, it is already stated in CS 29.1(c) that Category A approval is required.

Clarification is given that only helicopters certified solely to Category B are affected by the additional limitations which are normally associated with Category A. Where a Category B approval is a stepping stone before gaining a Category A approval, the additional Category A limitations will not be applied as part of the Category B approval. Helicopters with MTOM greater than 9072 kg but with less than 10 passenger seats (CS 29.1(d)) and helicopters with MTOM less than 9 072 kg but with more than 10 passenger seats are within this regulatory frame.

This allows all large multi-engined helicopters to be type certified as both Category A and Category B with appropriate and different operating limitations, as defined in CS 29.1(b). This aligns with the change to CAT.POL.H.300, and ensures that the objective defined for the RMT is fulfilled.

An accompanying AMC regarding certification standards will be included.

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:

CS 29.1 Applicability
…
(b) Transport category rotorcraft must be certificated in accordance with either the Category A or Category B requirements of this Part. A multiengine rotorcraft may be type certificated as both Category A and Category B with appropriate and different operating limitations for each category. [my underlining]

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:

2.6.2 CS 29.1 Availability [Applicability]

...

For helicopters with MTOM greater than 9072 kg and 10 or more passenger seats, it is already stated in CS 29.1(c) that Category A approval is required.

...

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

[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.

[JimL]

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:

Category A, with respect to transport category rotorcraft, means multiengine rotorcraft designed with engine and system isolation features specified in Part 29 and utilizing scheduled takeoff and landing operations under a critical engine failure concept which assures adequate designated surface area and adequate performance capability for continued safe flight in the event of engine failure.

and, for the JAA/EASA/ICAO:

Category A, with respect to rotorcraft, means a multi-engined rotorcraft designed with engine and system isolation features specified in CS–27 / CS–29 and capable of operations using take-off and landing data scheduled under a critical engine failure concept which assures adequate designated surface area and adequate performance capability for continued safe flight or safe rejected take-off in the event of engine failure.

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

[HeliTester]

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

[212man]

HT, that's how I understand it.

[JimL]

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:

...
In addition, PC2 regulations for take-off and landing allowed operations which were not within the scope of Category A. This constituted a regulatory mismatch with the Category A certification requirement. This was not further approached by the JAA.
...

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):

(a) For helicopters certificated in Category A, a momentary flight through the height velocity (HV) envelope is allowed during the take-off and landing phases, when the helicopter is operated according to any of the following requirements: [take-off/landing with exposure]

and CAT.POL.H.300

(b) Helicopters operated in performance class 2 without an assured safe forced landing capability during the take-off and landing phases shall be certified in both Category A and Category B or equivalent as determined by the Agency.

(c) Operations defined in (b) shall be conducted subject to the AFM limitations of Category A, except prior to the defined point after take-off (DPATO) and after the defined point before landing (DPBL) where Category B limitations may apply.

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).

(a) UTILISING CATEGORY B LIMITATIONS

Within the area defined in CAT.POL.H.300(c), Category B limitations may only apply if:

(1) a Category A procedure is impractical and the authorised take-off weight and landing masses would penetrate the height-velocity envelope during a performance class 2 take-off or landing; and/or

(2) the available take-off and landing area (FATO) would not allow a safe forced landing following a failure of the critical engine.

[JimL]

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.

[JimL]

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:

Suggestion 3:

Change CS-29 to move the H-V envelope from the limitations section to the performance section in the AFM.

Moving the H-V envelope from limitations to performance criteria goes against the Category A certification philosophy and would be a non-trivial change. Furthermore, changing CS-29 in such a way would create a substantial difference with the similar FAA certification requirements, and may impact on type-validation and acceptance by foreign authorities.

It should also be noted that to obtain the expected effect of the suggestion, Category A take-off and landing weights would also need to be required transposed from limitations to performance criteria. This would go against the regulatory desire and trend towards encouraging more powerful helicopters with full Category A engine failure accountability.

In the Agency’s view this suggestions cannot be further considered.

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:

If an engine failure is recognized at the Takeoff Decision Point (TDP) or at any point in the takeoff profile prior to attaining TDP, the rotorcraft must be able to land safely within the established rejected takeoff distance. Flight testing to determine the Category A rejected takeoff distance is very similar to height-velocity testing and should be approached with caution. The initial Category A takeoff profiles should be outside of the avoid area of the Category B height-velocity envelope.

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:

Suggestion 6:

Change Regulation (EU) No 965/2012 to allow dispensation from the AFM limitations to allow short time penetration of the H-V curve during PC2 take-off and landing.

Regulation (EU) No 965/2012 cannot include a paragraph allowing dispensation or alleviation from airworthiness criteria defined in the AFM as it would be in conflict with the Basic Regulation.

In the Agency’s view this suggestions cannot be further considered.

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:

2. Unless otherwise determined in the implementing rules, operators engaged in commercial operations shall demonstrate their capability and means of discharging the responsibilities associated with their privileges. These capabilities and means shall be recognised through the issuance of a certificate. The privileges granted to the operator and the scope of the operations shall be specified in the certificate.

3. Unless otherwise determined in the implementing rules, operators engaged in the non-commercial operation of complex motor-powered aircraft shall declare their capability and means of discharging the responsibilities associated with the operation of that aircraft.

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

Unless otherwise determined in the implementing rules, an aircraft must be operated in accordance with its airworthiness documentation and all related operating procedures and limitations as expressed in its approved flight manual or equivalent documentation as the case may be.

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

[JimL]

“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:

2.1 Helicopters operating in performance Classes 1 and 2 should be certificated in Category A.

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):

…provides the most rigid rules, requiring multiengine design with independent engines, fuel systems, and electrical systems. Category A design requires that no single failure can cause loss of more than one engine. Although there is no limit on maximum weight, Category A rotorcraft are certificated at a weight which will assure a minimum climb capability in the event of engine failure and with adequate surface area to assure a safe landing in the event an engine fails anywhere in the flight envelope, including takeoff or landing operations.

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):

3.1.1. CAT.POL.H.300 General

(a) Helicopters operated in performance class 2 shall be certified in Category A or equivalent as determined by the Agency.

(b) Helicopters operated in performance class 2 without an assured safe forced landing capability during the take-off and landing phases shall be certified in both Category A and Category B or equivalent as determined by the Agency.

(c) Operations defined in (b) shall be conducted subject to the AFM limitations of Category A, except prior to the defined point after take-off (DPATO) and after the defined point before landing (DPBL) where Category B limitations may apply.

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):

CAT.POL.H.305 Operations without an assured safe forced landing capability

(a) Operations without an assured safe forced landing capability during the take-off and landing phases shall only be conducted if the operator has been granted an approval by the competent authority.

(b) Momentary flight through the height velocity (HV) envelope is permitted during the take-off and landing phases.

(c) To obtain and maintain such approval the operator shall:

…

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

[steve_oc]

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

[JimL]

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:

Suggestion 1:

Change the Basic Regulation to allow deviations from the AFM when applicable.

Even if it is possible to include a paragraph in the Basic Regulation allowing dispensation or alleviation from the AFM limitations, the Agency has decided not to because respecting the airworthiness limitations is an accepted general principle which should be maintained.

By retaining this principle, the Basic Regulation, Annex IV, paragraphs 4.a and 8.b, as quoted in 2.1.3 (a), remains in effect.

In the Agency’s view this suggestions cannot be further considered.

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

[JimL]

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.

Under FAR 91.9(d) the conditions are: flight from a heliport constructed over water in which a safe ditching can be accomplished; and, the helicopter is amphibious or equipped with floats.

Under Appendix 1 to JAR-OPS 3.005(c) the conditions are: the operator has an approval for operations with exposure.

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.

Effect USA: because operational FARs do not contain a formal code of performance, they rely upon the conditions of FAR 29.1(c) and (e) (the H-V Diagram as a Limitation) to ensure that flights are conducted in accordance with (the equivalent of) Performance Classes 1 and 2*. For that reason, they are unlikely to accord with a proposal to amend Part 29.

* FAR 29.1(c) contains the conditions under which Performance Class 1 can be conducted and FAR 29.1(e) Performance Class 2. (These are signalled through the application of the Category A WAT – meeting the second segment climb requirements - and observance of the H-V Diagram; and, additionally for 29.1(c), the application of the Category A Procedures.)

Effect Europe: no detrimental effect - Europe is in compliance with ICAO Annex 6, Part III in showing compliance with Chapters 3.1.1 and 3.1.2:

3.1.1 Helicopters shall be operated in accordance with a code of performance established by the State of the Operator, in compliance with the applicable Standards of this chapter.

Note 1.— The code of performance reflects, for the conduct of operations, both the various phases of flight and the operational environment. Attachment A provides guidance to assist States in establishing a code of performance.

3.1.2 In conditions where the safe continuation of flight is not ensured in the event of a critical engine failure, helicopter operations shall be conducted in a manner that gives appropriate consideration for achieving a safe forced landing.

Note.— Guidance on “appropriate consideration” is contained in Attachment A, 2.4.

Solution – Short Term:

Provide alleviation from the requirement to apply the RFM Limitations under controlled conditions.

Effect USA: no change from the status quo.

Effect Europe: this will require the following amendments to the regulations:

The text “Unless otherwise determined in the implementing rule” has to be prepended to paragraph 4.a of the Essential Requirements; and

The addition of new paragraph (b) to CAT.POL.H.205 “Momentary flight through the height velocity (H-V) envelope is permitted during the take-off and landing phases.”

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

[Shawn Coyle]

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?

[JimL]

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:

CS 29.87 Height-velocity envelope

(a) If there is any combination of height and forward velocity (including hover) under which a safe landing cannot be made after failure of the critical engine and with the remaining engines (where applicable) operating within approved limits, a height velocity envelope must be established…

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:

CS 29.1517 Limiting height-speed envelope

For Category A rotorcraft, if a range of heights exists at any speed, including zero, within which it is not possible to make a safe landing following power failure, the range of heights and its variation with forward speed must be established, together with any other pertinent information, such as the kind of landing surface.

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

CS 29.1583 Operating limitations

(f) Limiting heights. Enough information must be furnished to allow compliance with CS 29.1517.

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:

“Therefore, if the Category A takeoff and landing profiles, procedures, and WAT limitations are adequately and clearly defined in the RFM, this information is considered sufficient for compliance with the requirements of § 29.1583(f) without the inclusion of an actual HV diagram. The Category A procedures and profile definitions may be presented in the normal procedures or performance sections of the RFM but should be referenced as being mandatory requirements in the limitations section unless an HV diagram valid for Category A operations is presented.”

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

[Shawn Coyle]

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.

[JimL]

“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

[HeliTester]

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.

[JimL]

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:

(9) Vertical takeoff and landing (VTOL) testing normally does not require separate HV testing. The takeoff and landing tests take on the combined characteristics of takeoff, landing, and HV tests.

(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:

(10) Rotorcraft certificated prior to Amendment 29-21 were required to have the resulting height-velocity diagram as an operating limitation. This limitation restricted opportunities when operating large rotorcraft in various utility applications. Subsequently, Amendment 29-21 allows, under certain conditions, the height-velocity diagram to be placed in the Flight Manual Performance Information Section instead of the Limitations Section. Specifically, the rotorcraft must be: (1) certificated for a maximum gross weight of 20,000 pounds or less; (2) configured with nine passenger seats or less; and (3) certificated in Category B. Testing must be completed with the aircraft at the maximum gross weight at sea level. For altitudes above sea level, the test aircraft must be at a weight no less than the highest weight the rotorcraft can hover out-of-ground-effect (OGE). Rotorcraft certificated prior to Amendment 29-21 can update their certification basis to take advantage of this provision.

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