10 Range Flashcards
What is Specific Range, what are to two types and what type of speed are they associated with?
- Specific Range is the best measure of fuel with distance
Two types are:
- Specific Ground Range (SGR) which is related to Ground Speed
- Specific Air Range (SAR) which is related to TAS
What are the equations for the two types of Specific Range (jet)?
- SGR = GS / Fuel Flow = GS / (SFC x D)
- SAR = TAS / Fuel Flow = TAS / (SFC x D)
How is Fuel Flow related to Thrust and Power for a Jet AC and a Prop AC?
- Jet: Fuel Flow is proportional to Thrust
- Prop: Fuel Flow is proportional to Power
What sort of consideration is Specific Fuel Consumption and what is the formula for a Jet AC and a Prop AC?
- Specific Fuel Consumption (SFC) is an engine only consideration and is not affected by Drag (aerodynamic consideration)
- Jet SFC = Fuel Flow / Thrust
- Prop SFC = Fuel Flow / Power
In what conditions is the Specific Fuel Consumption for a Jet best?
- Low Temperatures
- Engine is running at it’s design RPM (apox. 90 - 95% max)
What is the formula for the Specific Air Range of a Jet AC?
SAR = TAS / (SFC x Thrust Required)
In straight and level flight this can be written as:
SAR = TAS / (SFC x Drag)
Since Thrust = Drag in S and L
What is the speed for Maximum Range in a Jet AC?
Which curve can this be found on and where?
- Speed for Maximum Range = 1.32 Vmd (Mmr: Mac Max Range)
- Found at the tangent to the Total Drag curve
What is the optimum altitude for Maximum Range on a Jet AC and why?
- The optimum altitude for a Jet AC is high for two reasons:
1. Achieve a higher TAS for the same IAS and Drag
2. High altitude allows the engine to operate at the correct speed AND it’s optimum design RPM (90 to 95% Max)
What is the Specific Air Rang for a Prop AC?
Specific Air Range = TAS / (SFC x Pr)
What is the speed for Maximum Range in a Prop AC?
Which curve can this be found on and where?
- Speed for Maximum Range is Vmd
- Found at the tangent to the Power Required curve
Why does altitude have a smaller effect on the Maximum Range of a Prop AC compared to a Jet AC?
- Since Pr = TAS x Drag
- And SAR = TAS / (SFC x Pr)
- So the effects of increasing TAS are cancelled out
What is the Altitude for Maximum Range for a Prop called?
Full Throttle Altitude
What are the factors which affect the Range of an AC and how do they affect the speed for optimum range?
- Increase in Mass: reduces Range, 1.32Vmd (Mmr) increases
- Altitude: Maximum Range is only achieved at the optimum altitude, any deviation from this will result in a reduced Range
What happens to the following (and why) as a flight progresses and fuel is burned, reducing the AC mass:
- Optimum Altitude
- Specific Air Range
- Optimum speed for max range
Optimum Altitude Increases:
- Less mass means less induced drag (and less Thrust is needed) so to keep at optimum design RPM, more altitude is needed
Specific Air Range Increases:
- SAR = TAS / (SFC x Drag)
- Less Drag means higher SAR
Optimum speed for max range decreases:
- Less Induced drag means lower Vmd so lower 1.32Vmd
What is the purpose of the Step Climb technique?
To increase Range by staying as close to the optimum altitude as possible as the flight progresses. Whilst complying with the ATC requirement of using flight levels
