Updating Class 1 Performance Figures

[biz-buz]

Hello,

I would be very grateful for any pointers regarding the reworking of some Class 1 performance figures for the AS355 F1 & F2. I work for a company that bought the 1991 Eurocopter/Allison STCs to up-rate the engines from C20F to C20R, these STCs have just been validated by EASA.

The problem is that the Americans were not overly concerned with updating the figures given in the Category A HLS and platform operations, Flight Manual Supplement, so the original STC did not change any of the manufacturers data, although obviously the figures could have been greatly improved. With the new EASA validation this is now very important to bring this part of the Flight Manual into line.

I have access to all the test data, including the single engine climb rate figures and hover IGE and OGE figures etc etc. I have read the JAR 27 regulations and the JAR Ops parts but apart from the various guidelines and comments about minimum rates of climb and 35ft limits there is not much help on how max take-off weights can be extrapolated and new figures calculated.

Can this reworking be done using an "official formula" or is it a smoke and mirrors job? If it is the former, any pointers to any official texts would be welcome, if the latter, a pointer to somebody who might be able to do this for me would be equally welcome.

Thank you.

[spinwing]

Oh .....surely you jest ? ....... AS355 ...... Performance 1 ..... :uhoh:

:E :ooh: :ooh: :ooh:

[biz-buz]

Thanks spinwing for the helpful comment! :zzz:

As far as I am aware once an aircraft is accepted as being Category A (even if only with a dispensaton) and is able to demonstrate Class 1 ability, the captain trims his load to suit the aircraft performance. It might well be that the F1 or F2 can only manage 2 pax in the back, but it can still operate according to Class 1 performance criteria.

Hence the interest in having the STC and the reason I need to update the figures!

There must be somebody who could give me a pointer please!:sad:

[gnz]

Could it helps you to have a look in JAA-NPA OPS 38? http://www.jaa.nl/operations/public_area.html:

[Shawn Coyle]

biz-buz:
Good luck. I think you'll find that you need to do a lot of rejected takeoffs, hover in and out of ground effect, and Category A fly aways to prove to the authorities that you have the extra capability.
The issue is that the Flight Manual doesn't give you performance in a meaningful way - by that I mean power required to hover vs. height AGl for a variety of temperatures and Pressure Altitudes. You would then be able to compare this to the (new) power available from the engines to see what improvement might be possible.
You also have make sure the engines you are using a set to 'minimum specification' engines, and not new, out of the box, 10% better than spec power.
A very interesting task - lot of detailed performance work needed.

[biz-buz]

Thanks for the pointers Shawn and gnz,

I have had a good idea :ok:

The post-STC performance or the F2 is as near as dammit that of the AS355N, which is what the aim of Eurocopter was when they conceived the STC. Eurocopter have already cited the "N" figures to the FAA to justify many elements of this STC already. As I can show by OEI hover OGE and climb rate figures that the performance is identical or even better in some cases, to the "N", this should not pose a problem.

This uses existing approved data and removes the need to justify the figures! If this fails then I will have to re-hash the existing figures. :)

gnz, you seem to be in the south of france, I am in the Charente, get in touch if you want. :cool:

[hostile]

Biz-buz,

I am not sure that have you understand differencies of CAT A and Performance class 1. Cat A is approval stuff for the helicopter manufacturers and Performance Class 1, 2 or 3 is pure JAA regulation. Read that NPA-38 and you can found many good information for it. Performance classes 1 and 2 are more than good powerfull helicopter.

Hostile:ok:

[gnz]

Hi biz-buz,

Aren't your charente neighbourood HUTC?...:ok:

Good luck for your enquiry