RPM 365 on the AS365N3...

[tophelios]

Hi guys,

A little question concerning the RPM365 on the as365n3... This one is mandatory for the helipad take off (and landing )in cat A, but what do you think about using it during the winching ? particulary at sea and with a weight which doesn't allow you the OGE-OEI and the 'fly away'... Thanks for your point of view...

THS

[Flying Bull]

Hi tophelios,

I think RPM high is a good idea, when hovering with high mass, not only for Cat A operation.
What happens, if an engine fails on you? You´ll have an rpm drop before the other engine has a chance to serve you with increased power.
But it won´t be able to restore rpm to normal, as long as you´re pulling power - which you will certainly do ;).
The drop will not only affect the main rotor, making the bird more sluggish, it also effects the tailrotor/fenestron giving you less directional stability.
With rpm high selected you will still encounter an rpm drop - but from a higher startvalue leaving more rotor rpm when the other engine is up to full power thus giving you more time/rpm to play with to get out of the situation.
It is not forbidden to select RPM high at low speeds - so use it.
If you have the chance to have a ride in helisim, check it out - rpm high makes your life a lot easier, when an enginefailure hits you in the hover OGE.

Greetings Flying Bull

[VSOP]

Helisim's is N2, not N3.

[FlyingWay]

I used to fly AS532A2 more the 6 years
We wear flying over gulf see at night for hoisting rescue divers most of our work was in hot temperature , mostly more than 36 centigrade, and near calm wend, although we don't use RPM plus
From my experience using RPM+10 produce more drag on the rotor disc and effects the proficiency of helicopter movement OGE,
So I don't think it's good Idea to use RPM+10, during hovering out of ground effect

[Flying Bull]

Hi all,

more RPM does mean more drag on the blades - but it can't be much - because you also need less AOC with higher RPM.
And is it important about which helicopter we talk? The BK117 C1 with VARTOMS automaticly increases RPM when matching special figures i.e. density altitude and speed below a certain figure - for going to land or hover.
By the way helisim can have the following cockpits:
Super Puma MK1, Super Puma MK2, Dauphin N 2, EC155.

As long as both engines are running, you might not feel the difference - but I'm sure you will, when one engine fails on you.
You end up with more RPM if everything else stays the same - having more energy in the head, giving you the possibility to trade more RPM for Lift before reaching the min. RPM - and that might save your butt.
It works in helisim with the EC155, it works with the real machine - why shouldn't it work with the N3?
Take an IP and have a go, test it and you will know.

Greetings Flying Bull

[VSOP]

It works very very well with the N3.

[cpt]

I am not currently flying the N3 on operations, but my colleagues who do use to say they don't like this 365 NR mode since it brings the torque near the limit.....
I always have found this a little strange, since normally at a given power if we increase NR, Torque should decrease and N1 increase. It seems to be what we are looking at when torque limited.
Now, in increasing to 365NR we maybe loose a little bit in main rotor efficiency (when we gain in inertia and tail rotor effectivness)
Could it be the resultant of all these effects that make this torque increase instead of a decrease, or is it just a short temporary increase before a stabilisation at a lower value (as we can observe on 365N/N2 when we "play" with variations in NR ?

[VSOP]

FADEC "makes" the "diference".

[tophelios]

thanks for all...
just to add something, in the flight manual, we've got a 'height loss' diagram, but calculated without the RPM365 on...
and in case of ditching or emergency landing (during the winching), do you think +7 or 8 RPM do really make a difference ?

[Flying Bull]

Hi topelios,

with the EC155 - the difference is remarkable.
(I have videos from the simulator - but not cut by now and not quite sure, whether I'm allowed to make them public)
Speed always have the square in the formula - look for the brake way of a car with speed 50 km/h and 58 - its not only 1/6 longer as expected, (dependeing on factors - without reaction - MS tires its 17.5 meters to 23.5 meters)
So the additional energy in the head is a real factor.

But if curious - and with no simulator at hand - why not take an IP, a very light helicopter, may be before or on an technical trip - and check it out - go in the hover OGE, first with RPM high, check, that TQ won't hit the limits (thats what the light helicopter is fore) when retarding an engine and put one engine to idle and look what happens. (a videocamera would be handy to record RPM drop) - and don't touch the controls (pitch), only if really necessary - just pretend it hits you on surprise while looking outside.
After putting the engine back, select normal RPM and then put the same engine to idle and see what happens, even with the now lighter bird (burnt fuel).
Surely, before doing that, you should check the charts, whether OEI OGE hover is possible.

Look for RPM drop, height loss - and use the chance to practise a fly away.

Surely there will be a difference with a heavy helicopter with more TQ pulled to hovery - the RPM drop will be greater, because there is more power required from the running enigine.

After that come back to the forum and tell us, if there is a difference to the theory or between N3 and EC 155.

Greetings Flying Bull

[skadi]

I don't know, whether the 155 could be switched into TRAINING MODE like the 135 CPDS, but on the latter the NR Drop in case of OEI with or without HIGH NR could be demonstrated very well, the difference is remarkable...

skadi