AS-365 Decrease in Fuel Flow with Increase in speed
Thread Starter
Joined: Dec 2001
Posts: 1,835
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From: Philadelphia PA
AS-365 Decrease in Fuel Flow with Increase in speed
Just cleaning up some old documents, and came across some technical information from Eurocopter on the AS-365 family. Fuel flow in cruise shows a distinct notch for all weights at about 240-280 kg/hr. For example, at maximum weight, at sea level, ISA, the curve increases normally until it reaches a point of 128KTAS, with a fuel flow of 278kg / hr, then as the speed increases a mere 2 knots, it suddenly drops to 270Kg/hr. This change is at a consistent fuel flow of 278kg, that then drops back to 270 kg/hr for all weights (obviously different airspeeds) with a 2 knot increase in airspeed.
At 5,000 ft, the change occurs at 240kg/hr, when it drops back to 233 kg/hr for all weights with a 2 knot increase in airspeed. Much the same sort of thing happens at 10,000' when the fuel flow goes from 206kg/hr to 199kg/hr
This appears to fly in the face of common sense and previous experience.
Is there a change in rotor RPM somewhere here? Or something else????
At 5,000 ft, the change occurs at 240kg/hr, when it drops back to 233 kg/hr for all weights with a 2 knot increase in airspeed. Much the same sort of thing happens at 10,000' when the fuel flow goes from 206kg/hr to 199kg/hr
This appears to fly in the face of common sense and previous experience.
Is there a change in rotor RPM somewhere here? Or something else????
Joined: Nov 2006
Posts: 103
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From: USA
Fuel Flow
I think it caused by Fenestron. Fenestron takes less power in cruise flight.
Power absorbed by tailrotor. Classical tailrotor vs. Fenestron
Hover (IAS 0) 15% - 30%
Climb (IAS 75) 12% - 15 %
Cruise (IAS 135) ~10% - 2%!!
as you can see in hover parameters the Fenestron is not the best choice to hoist (Hover) operations. This not the answer, only comment...
Hostile
I think it caused by Fenestron. Fenestron takes less power in cruise flight.
Power absorbed by tailrotor. Classical tailrotor vs. Fenestron
Hover (IAS 0) 15% - 30%
Climb (IAS 75) 12% - 15 %
Cruise (IAS 135) ~10% - 2%!!
as you can see in hover parameters the Fenestron is not the best choice to hoist (Hover) operations. This not the answer, only comment...
Hostile
Joined: Nov 2006
Posts: 1,951
Likes: 90
From: After all, what’s more important than proving to someone on the internet that they’re wrong? - Manson
Arriel engine - bleed valve closing.
Same on all Arriel powered aircraft.
Some are electric controlled via speed sensor, 1B, 1C etc, some are pneumatic 1D, 1S .........
Dusting off the grey matter - best range in 350B, BA was with bleed valve just closed, so long as you weren't exceeding Q limits. Sometimes not possible on variants with fat engines.
Same on all Arriel powered aircraft.
Some are electric controlled via speed sensor, 1B, 1C etc, some are pneumatic 1D, 1S .........
Dusting off the grey matter - best range in 350B, BA was with bleed valve just closed, so long as you weren't exceeding Q limits. Sometimes not possible on variants with fat engines.
Joined: Apr 2002
Posts: 687
Likes: 1
From: Up north
The graphs may say that but in real life - more power selected more fuel used. We use 280kg/hr as a standard fuel planning figure which produces accurate fuel figures for N Sea/Lpl bay operations which are generally flown at 3000ft and below.
THe only 365N2 "trick" I have used is to increase speed as much as possible and then back off the Tq a few % and she will sometimes hold the increased speed with the reduced tq and fuel flow.
HF
THe only 365N2 "trick" I have used is to increase speed as much as possible and then back off the Tq a few % and she will sometimes hold the increased speed with the reduced tq and fuel flow.
HF
