Low RRPM in cruise
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Hi Delta3!
My bad!!
I should have included....increase rrpm, lower collective to original tq setting. Thus you would have a lower AOA for the same amount of lift (at increased NR).
DK
My bad!!
I should have included....increase rrpm, lower collective to original tq setting. Thus you would have a lower AOA for the same amount of lift (at increased NR).
DK
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76
DK,
That would mean to me that the 76 has a highly loaded disk at cruise, that is on the average over the optimal point (at this point drag indeed increases with AOA, more than lift)
I have no data on this machine (nor math, nor flying experience) I'll leave that to the specialists (Nick..., I remember a track where Nick indeed explained that the 76 design was optimised more for high speed than for hover performance)
d3
That would mean to me that the 76 has a highly loaded disk at cruise, that is on the average over the optimal point (at this point drag indeed increases with AOA, more than lift)
I have no data on this machine (nor math, nor flying experience) I'll leave that to the specialists (Nick..., I remember a track where Nick indeed explained that the 76 design was optimised more for high speed than for hover performance)
d3
Thread Starter
Recuperator:
I read somewhere that the FADEC on the 130 will do it.. I don't really know.
Regards.
The EC 120 does not have the facility to beep down it's RRPM.
Neither does the AS350B3 and therefore I don't think the EC130 (AS350B4) has it either
Neither does the AS350B3 and therefore I don't think the EC130 (AS350B4) has it either
Regards.
Aser comments on the 76 having a "Noticeably better fuel burn" than a Huey.
The Huey burns 600 lb/hr, flogging along at 100kt = 6lb/nm. The 76B burns 700 lb/hr at 140 kt (5 lb/nm) or 800 lb/hr at 150 kt (5.33 lb/nm). I suppose you could call it noticeable, but more noticeable than that is that the passengers from the S76 have already downed two beers before the Huey lands.
The Huey burns 600 lb/hr, flogging along at 100kt = 6lb/nm. The 76B burns 700 lb/hr at 140 kt (5 lb/nm) or 800 lb/hr at 150 kt (5.33 lb/nm). I suppose you could call it noticeable, but more noticeable than that is that the passengers from the S76 have already downed two beers before the Huey lands.
Thread Starter
NOTICEABLE better fuel burn?
Now that the consecuencies of change from 100% to 97% in i.e. a B412 is clear for me...
What I would like to see is the figures compared between 100%rrpm and 107rrpm in a 76 (asumming it isn't a 76B,so you could change rrpm) , do you have it?
You 76A drivers , how do you feel the vibs when flying from 100% to 107% , an increase?
Excuse me if I'm too boring.
Thanks.
Aser
IMHO
On the 76A generally the 4P in cockpit goes down when RRPM is increased from 100 at TO to about 103-104%, I think thats where most of the people have their RRPM during crusise.
How the vibe level is at 107% is very much depending on density altitude and weight, and we are talking mostly 4P. I do not think you can read any noticible 1P diffrence on a track and balancer unit between the two RRPM's.
We fly the A's at 103-104% and increases the RRPM going up in altitude, 104@4000, 105@5000, 106@6000 and 107@7000 and above. It seems to work well in regards of vibes and is also in "sync" with the FF and TAS diagrams.
One benefit is also higher VNE margin at altitude (in reality) but you can not read it somewhere.
CB
On the 76A generally the 4P in cockpit goes down when RRPM is increased from 100 at TO to about 103-104%, I think thats where most of the people have their RRPM during crusise.
How the vibe level is at 107% is very much depending on density altitude and weight, and we are talking mostly 4P. I do not think you can read any noticible 1P diffrence on a track and balancer unit between the two RRPM's.
We fly the A's at 103-104% and increases the RRPM going up in altitude, 104@4000, 105@5000, 106@6000 and 107@7000 and above. It seems to work well in regards of vibes and is also in "sync" with the FF and TAS diagrams.
One benefit is also higher VNE margin at altitude (in reality) but you can not read it somewhere.
CB
Thought I would conduct an experiment:
SK-76A++
FL 045 (4500FT) @1013 0r 29.92
OAT 33 C
IAS 115 kts---------------------------IAS 115 kts
RPM 107% ---------------------------RPM 102%
1 eng Q 59 ---------------------------1 eng Q 64
N1 96.1--------------------------------N1 97.0
ITT 739 -------------------------- -----ITT 753
FF 270 lbs/hr---------------------------FF 280
2 eng Q 60----------------------------2 eng Q 70
N1 96.1---------------------------------N1 97.3
ITT 760----------------------------------ITT 780
FF 282 lbs/hr----------------------------FF 295
Fuel flow total 552 lbs Hr---------Fuel flow total 575 lbs Hr
So it would appear that for a given IAS fuel flow is lower at 107% RPM than at 102%.
In this 76A++ at least.
SK-76A++
FL 045 (4500FT) @1013 0r 29.92
OAT 33 C
IAS 115 kts---------------------------IAS 115 kts
RPM 107% ---------------------------RPM 102%
1 eng Q 59 ---------------------------1 eng Q 64
N1 96.1--------------------------------N1 97.0
ITT 739 -------------------------- -----ITT 753
FF 270 lbs/hr---------------------------FF 280
2 eng Q 60----------------------------2 eng Q 70
N1 96.1---------------------------------N1 97.3
ITT 760----------------------------------ITT 780
FF 282 lbs/hr----------------------------FF 295
Fuel flow total 552 lbs Hr---------Fuel flow total 575 lbs Hr
So it would appear that for a given IAS fuel flow is lower at 107% RPM than at 102%.
In this 76A++ at least.
Thread Starter
albatross: very interesting to me, thanks for your time. But it would be nice to compare between same mast-TQ not airspeed
There is any other helicopter that states in the FM the possibility of adjust rrpm to more than 100%?
Best regards
Aser
There is any other helicopter that states in the FM the possibility of adjust rrpm to more than 100%?
Best regards
Aser
OffshoreIgor 