CAT A explaination

[froggy_pilot]

Flying Cat A means that if you respect the flight manual (weight,OAT,performance charts) an average pilot will be able to land or take-off safely with one engine inoperative.
CAT A procedures use international standards (35 ft obstacle clearance...)

A procedure is established for each case by the manufacturer of the aircraft and has been demonstrated in flight

-you have to abort take-off before a decision point and continue take-off after this point
- you have to go around one engine inoperative before a decision point and land after this point

CAT A is not only performed on helipad but also on runways.
On runways you take in account acceleration-stop distance.

Some twins are not CAT A capable the AS 355F1 for example, but the AS 355N is CAT A capable due to is engines

Some twins can fly CAT A but with a reduced weight, the AS 332L max take-off weight is 9000 kg but CAT A take-off max weight is reduced to 8600 kg

:confused: Hope i've been clear

Most companies are pretending flying CAT A, they don't, just imagine they have to reduce the passengers/pay-load by 15% to 45% !!!!!!! no way $$$$$$$$ :mad:

[soggyboxers]

Hi Froggy,

Sorry, but actually you haven't been totally clear!

The CDP on take off is the only point at which, in the event of the failure of a critical power unit (caters for 3 engined helicopters also!), the take off may be either rejected or continued. In the event of a failure before CDP it must be rejected and in the event of a failure after CDP it is normally continued (depending, in the case of operation from a runway, if there is still sufficient distance remaining to reject safely).

The AS355F1 does have category A performance and has a Category A supplement in its FM, the same as other Eurocopter types. I think you are probably referring to engine containment when you state that it does not have category A performance. It has a supplement for elevated helipad performance and is cleared by the CAA to operate Category A onto a number of rooftop helipads in UK. Naturally this entails a considerable performance penalty, meaning that in hotter countries it is unable to carry any meaningful payload to/from a helipad.

- you have to go around one engine inoperative before a decision point and land after this point

I presume that here you are referring to the landing decision point as opposed to the CDP for take off. In the event of the failure of a critical power unit before LDP the landing may be continued or a go-around performed: after LDP there is no possibility to carry out a safe go around and the aircraft must be landed.

You are quite right that there are also factors such as accel/stop distance to be considered (although with some of the new types, such as the S92, coming into service this becomes irrelevant at most weights and temperatures due to its ability to transition away from an engine failure in the hover at MAUM). There are also factors such as single-engine rate of climb, obstacle clearance and performance at MSA to be considered. For performance at MSA, some regulatory authorities allow the use of fuel jettison - though this is not normally allowed to be used below 1,000 feet AGL for performance planning purposes.

Different countries have different rules, though most are based broadly around ICAO. I'm sure that there will now be numerous other replies which will correct some of what I have said and amplify it, though a great deal of this ground has been covered already on the thread about true Category A performance, so maybe you should have posted this on that thread.

Cheers, Soggy. :D

[Nick Lappos]

Froggy,

The important distinction in Cat A is that there can be many Cat A procedures for a model helicopter, each allowing a tradeoff between gross weight (payload), and landing distance and/or altitude/temperature.
They are in three general types:

Airfield Cat A , with land back distances and takeoff distances in the 1000 to 1500 feet range. These generally require you to accelerate to a speed where the climb is good even at MGW, usually close to Vy. This is usually at 100% of MGW, because most large helos must meet some Cat A procedure.

Reduced Field Length Cat A, where you climb vertically or even backwards, and then land obliquely into an area that might be about 300 to 500 feet long. This is usually about 85 to 90% of MGW (or so).

Cat A Vertical, where you take off vertically and land the same way. These have two sub-types, those that allow a dip below the heliport height (elevated helideck) and those that do not (ground level). The dip procedure can allow 90% of MGW, the ground level is perhaps 80% or so.

Note that a 10% loss of MGW is perhaps a 30% loss of passengers, since all the rest of the weight items are relatively fixed in place.

To clear up something you said:

"Most companies are pretending flying CAT A, they don't, just imagine they have to reduce the passengers/pay-load by 15% to 45% !!!!!!! no way $$$$$$$$"

In fact, virtually all operators are strictly legal, nobody routinely breaks the rules. Full takeoff-to-landing Cat A is not yet legally required of any operator offshore (but JAR Ops 3 is coming), and is only required onshore in some countries (UK, for one) in conjested city areas. For offshore passenger carrying, enroute Cat A capability is required, and a few seconds of exposure to engine failure on takeoff and landing is allowed and even planned, with proper flotation, exposure suits and Cat B procedures.

[zalt]

Nick: in JAR-OPS 3 the two senarios you describe are termed Class I and II.

The JAA have tried to avoid confusion with the JAR-27/29 certification definitions for Cat A & B.

The rule does allow the continued use of Class II take offs from oil rigs until 2005 (I think from memory). Sub Part H describes the extra requirements (eg engine usage monitoring [which standard with the HUMS in the North Sea fleet]) if you do have exposure. That time limit could be extended, but that'll depend on EASA. I think the original plan was to base the decision on service experience.

Class II is not an option from city centre heliports - obviously.

[Xnr]

Sorry to tie these 2 discussions together but I have asked this question in "True Cat A Performance" and haven't got an answer.

It Doesn't really have to do with Class 1 (Cat A) but more the fact of weather you are operating under 703 Canadian Regs (Less than 9 passengers) or 704 (9+ passengers)

From True Cat A Performance

"I believe that the rules have been tightened yet another notch, thus the topic of this thread.

In Canada, my understanding is that Class1 (Cat A) performance helicopters may operate in 2 different categories and the regs for each are not the same.

As Shawn (Coyle) says you can operate with less than 9 passengers or more than 9 passengers.

If you operate with less than 9 you may enter the H/V chart for the purpose of your operation.....if you are operating with 9 or more you may not enter the H/V chart for any reason.

Therefore my question was if you are coming off a rig with 9+ passengers on board, as soon as you leave the deck with low airspeed you are now in the curve."

Are you legal?

[Nick Lappos]

Xnr,

The question that you ask is by no means new, and shows the difference between the clean area of certification and the rough and tumble of operations. The HV curve is not an absolute limit in an engineering sense, because it represents only one set of test assumptions and conditions. It is by no means an all-seeing way to predict a good/bad outcome with an engine failure. In the old days, it was put into the flight manual Part I section 1 as a limit, even though it is so very limited in use, and so very conservative.

Every operational FAA pilot I know realizes that it is possible to cross the corners of the HV diagram during many approaches, including elevated platforms and many waterside heliports, as well as many obstructed heliports where a slight hover down is needed. These operations inspectors do not violate anyone, to my knowledge, and even give check rides to and from those heliports, flying the same procedures themselves.

The real answer to your question is that, thank the Lord, examiners are practical fellows, and not trying to find the odd corners to shut folks down.

[Xnr]

Thanx Nick

No one would give me an answer to that one....I was hoping you would.

Just wondering...... will the lawyers be as practical as the FAA inspectors should someone get injured or worse when there is a rediculous reg like that in existance?

Will the FAA be there in your defense should the unthinkable happen?

Just a thought.....I know..... too much time on my hands......but in this day and age it is CYA.

[Shawn Coyle]

To clarify a small point on this. (Sorry for not answering earlier).
The requirement is to avoid the HV curve for takeoff, but not for landing.
Given the way the HV curve is made in the regions likely to be transgressed on approach (i.e. takeoff power below the knee with no delay in pilot action, and one second intervention above the knee with power for level flight), going through it on approach is different than at takeoff.

[Xnr]

Hey Shawn

Any word on the elevated helipad 9+ configuration H/V limits (take-off)


Also I have been looking in the Regs to try and find where it says that 9+ configuration is not allowed to enter the H/V curve at any time....could you point me in the right direction.

Cheers

[GLSNightPilot]

XNR, the HV curve is in the limitations section in that configuration, but it's in the performance section for <9 pax configuration.