Economic Cruise Speed AS 365
Joined: Apr 2003
Posts: 72
Likes: 0
From: FR
The Best Range Speed disappeared from the PMV.
It was published in section 10 in previous variants (F, N, N2...) with level flight performance charts, but not anymore
Really strange, especially if you consider the flight envelope defined in limitations section* (Max speed in turb = Best range speed)
*: For 155 AFCS H/C fitted, not considering APM 2010 fitted.
It was published in section 10 in previous variants (F, N, N2...) with level flight performance charts, but not anymore
Really strange, especially if you consider the flight envelope defined in limitations section* (Max speed in turb = Best range speed)
*: For 155 AFCS H/C fitted, not considering APM 2010 fitted.
Joined: May 2009
Posts: 292
Likes: 11
From: uk
ECON speed required - not Range speed
Don't think fooster was after Range speed but ECON speed as fuel costs are not only factor when determining most economic cruise speed.
Akin to Long Range Cruise and Max Range Cruise figures for transports - trade off between numerous financial/maintenance/operational factors.
Always found that most economic cruise speed for N3 was, for general chopper operating conditions over steady legs, the speed attained by using Max Cruise power.
Graphs show better 'economy' of fuel burn for distance covered - so even though your fuel flow increases, you fly for less time (as you are going faster) and so burn 'less' fuel.
Practice works when shown against flight plan fuel figures at various waypoints and expected fuel used - hence the phrase 'making fuel'
Akin to Long Range Cruise and Max Range Cruise figures for transports - trade off between numerous financial/maintenance/operational factors.
Always found that most economic cruise speed for N3 was, for general chopper operating conditions over steady legs, the speed attained by using Max Cruise power.
Graphs show better 'economy' of fuel burn for distance covered - so even though your fuel flow increases, you fly for less time (as you are going faster) and so burn 'less' fuel.
Practice works when shown against flight plan fuel figures at various waypoints and expected fuel used - hence the phrase 'making fuel'
Joined: Apr 2003
Posts: 72
Likes: 0
From: FR
In the N2 PMV, Best range speed varies from 120 to 135 Kts (depending OAT,Zp, weight). It's in section 10, level flight performances.
On the N3 PMV, no more mentioned.
Fooster, if it's the max endurance (Vy) you're after, it in the same charts (section 10), represented by the dotted line.
Agreed for the tangent, but it doesn't work on level performances, as the tq origin isn't 0 (??)
Fafe, the figures in section 2.3 (130Kts) is an IFR limitation (AFCS), not the best ratio distance/fuel. No reason to put this value (best range speed) in limitations. If it is one, will be in para 1 (Airspeed limitations), not in para 4 (IFR Flight).
On the N3 PMV, no more mentioned.
Fooster, if it's the max endurance (Vy) you're after, it in the same charts (section 10), represented by the dotted line.
Agreed for the tangent, but it doesn't work on level performances, as the tq origin isn't 0 (??)
Fafe, the figures in section 2.3 (130Kts) is an IFR limitation (AFCS), not the best ratio distance/fuel. No reason to put this value (best range speed) in limitations. If it is one, will be in para 1 (Airspeed limitations), not in para 4 (IFR Flight).
Joined: Mar 2008
Posts: 48
Likes: 0
From: Italy
Hi Gnz,
in the RFM RC D 2.3 4.2.1 Fully operational Duplex autopilot (that's a normal situation) or with one yaw lane inoperative the best range speed is 130 kt (with one pitch or roll lane unserviceable 130 is the limit, without exceeding VNE) and only there we can find this speed.
About the tangent we can extend the line below the origin in the figure (20 % torque) up to reach 0.
Fafe
in the RFM RC D 2.3 4.2.1 Fully operational Duplex autopilot (that's a normal situation) or with one yaw lane inoperative the best range speed is 130 kt (with one pitch or roll lane unserviceable 130 is the limit, without exceeding VNE) and only there we can find this speed.
About the tangent we can extend the line below the origin in the figure (20 % torque) up to reach 0.
Fafe
