When a manufacturer publishes the range of a private jet, it’s based on a set of standard assumptions about how the jet will be used. This allows the manufacturer to publish potential range of any given aircraft – “6,000 nautical miles.” “7,700 nautical miles” etc. However, buyers need to consider how they will use their jet and recalibrate range based on how the aircraft will actually be used.
When we asked Josh Dodd, COO at Avionco, an aviation management firm, he told us “Owners and operators need to understand the mathematics and planning behind range calculations as it will directly impact mission capability, cost, and safety”.
Today, let’s look at how range is calculated and how different variables should be considered.
How Manufacturers Calculate Range
When aircraft manufacturers calculate range, they do so using highly standardized conditions designed to produce a best case scenario on which they can state the jet’s potential.
Typically, these assumptions include:
- Optimal altitude profile (step climbs to maximum efficiency levels)
- Long-range cruise speed (not maximum speed)
- International Standard Atmosphere (ISA) conditions
- No wind resistance
- Minimal reserves (just enough to meet regulatory requirements)
- New aircraft performance (no performance degradation that occurs over time)
At the core of these calculations is something called the Breguet Range Equation, which simplifies range into a function of:
- Fuel efficiency
- Aerodynamic efficiency (lift-to-drag ratio)
- Aircraft weight
- Cruise speed
What this means in practice is that manufacturers can only provide a theoretical maximum range under ideal conditions, not a guaranteed operational range.
Why Most Flights don’t Measure up to Manufacturer Calculations.
In the business of flight, there are myriad variables that impact every aircraft on every flight that can have negative or positive impact on range.
One of the biggest variables affecting range is weight. Every additional pound onboard a flight, whether it’s passengers, luggage, or optional equipment, directly reduces how far the aircraft can fly.
More payload means higher fuel burn while carrying less fuel to reduce weight will result in shorter range.
Operators constantly balance three competing priorities:
- Payload (people and cargo)
- Fuel load
- Runway performance limitations
For example: A fully loaded cabin may require a fuel stop on a mission that would otherwise be nonstop. A short runway may limit maximum takeoff weight, forcing a reduction in fuel before the aircraft even leaves the ground.
This is why “full fuel, full passengers, maximum range” is almost never achievable simultaneously.
And of course, there are many, many other variables such as tailwinds or headwinds with the former increasing range and the latter shrinking it. Pilots can also mitigate some of the variables by flying at higher altitudes where thinner air reduces drag and engines operate more efficiently.
The takeaway here should be that range is a strategy and not a statistic. Knowledge, experience and planning are critical to an aircraft operating at peak proficiency. If you are someone who needs help with aircraft management, contact us at [email protected] to learn more.
About Avionco
Formed in 2000 by Mike Dodd and Josh Dodd, Avionco is a premier aircraft services provider, purpose-built to serve aircraft owners whose business and lifestyle needs require impeccable service and efficiency in everything they do.
Josh Dodd, COO, leads day to day operations with a team of dedicated senior management professionals delivering a complete suite of flight management services including Pilot and Crew selection, In-Flight and Ground Operations, Safety and Compliance, and Entry Into Service (EIS). Learn more at www.avionco.com