Products · Heavy-Lift and Civil Logistics

Range and Loaded Endurance Assessment

Loaded range is the number that decides whether a logistics route works. It has to be built from consumption, not from a headline figure.

9 of 10Method note

Overview

Structure the calculation as: energy available, energy per kilometre at the delivered mass, then reserve.
Vertical take-off and hover consume disproportionately; a route with many hover drops is shorter than one with wheels-on delivery.
Wind affects the outbound and return legs differently; compute them separately rather than halving a still-air figure.
Build in the reserve policy explicitly and state it — an unpublished reserve is an unpublished risk.

Typical conditions. Actual values depend on payload, wind and dispatch pattern.

A range figure without conditions is an upper bound

Range and endurance figures are produced at a payload, a speed, an altitude, a wind condition and a reserve policy. Those five conditions are not decoration — they are what the number means. Remove them and what remains is an upper bound: the best case, achieved in favourable conditions, which is not the number a programme should plan against.

This is not a criticism of how figures are published. It is how any physical measurement works. The problem arises when a figure is carried across into planning without its conditions, which happens routinely and produces aircraft that cannot complete the route they were bought for. Ask for the conditions, then re-derive the figure for your own case.

The five conditions differ in how much they move the result. Payload is usually the largest single lever, because mass is what the aircraft has to lift for the whole flight. Wind is the second and the most variable, because it acts on the whole route and changes with direction. Altitude, speed and reserve each take a smaller but real share.

Building the calculation honestly

Start with the round trip, not the one-way distance. A delivery route is an outbound leg with the load and a return leg without it, and the two legs have different mass, different wind exposure and, on routes with elevation change, different energy profiles. Planning on a symmetric round trip systematically overestimates capability.

Apply wind as a route-direction effect rather than as an average. What matters is the headwind component on the leg that determines whether the trip is possible — usually the loaded outbound leg — and the additional energy the return leg costs if the wind turns against it. Use the wind figure you expect to meet, not the calm-air figure.

Add the losses that do not appear in any specification: climb to working altitude, transition between flight regimes on VTOL platforms, turns at route ends, any holding, and the approach and recovery. On shorter routes these can be a larger fraction of the flight than on long ones, which is why short routes are where optimistic range figures do the most damage.

Reserve is not spare capacity

Reserve is the portion of energy or fuel deliberately held back so that the aircraft can deal with something unexpected and still arrive or return. It is not spare capacity to be spent when a route turns out to be longer than planned. The distinction matters because the two attitudes produce different planning: one treats reserve as untouchable, the other treats it as available, and only the first produces a route that still works when something goes wrong.

Set the reserve against the route's realistic worst case. On an inland route with landing options along the way, a smaller reserve may be defensible. On an overwater or mountain route with no alternative, the reserve should be sized so that an unplanned diversion or a stronger-than-expected headwind is still survivable.

State the reserve as a rule in the operating procedure, with a number, and make exceeding it an abort criterion rather than a judgement call. Our island logistics and mountain logistics notes show how the rule changes with route type.

From range to trips per day

Range determines whether a trip is possible; turnaround determines how many happen. The programme-level figure is trips per day, and it is usually where logistics economics are decided. A platform with marginally more range but substantially longer turnaround can deliver less per day than one with less range and faster turnaround.

Turnaround includes everything between landing and the next launch: battery swap or refuelling, load handling, pre-flight checks, data or record handling, and any crew rest requirement. Measure it on a real day rather than estimating it, because it is dominated by small tasks that nobody counts.

Then compute cost per delivered kilogram from trips per day rather than from range per trip. That figure is what makes two platforms genuinely comparable, and it frequently inverts the ranking produced by comparing range alone.

Getting the assessment done

For standard routes and standard configurations, the assessment is a calculation the operator can run with published figures, the route profile and the wind distribution. We can run it with you from route and load data.

For routes near the edge of capability, or with unusual conditions — high elevation, long overwater legs, unusual loads — it should be validated by a field trial before commitment. Our field testing and data collection work covers running that trial and test and verification methods describes how the results are structured.

Send your route profile, load mass, wind distribution, elevation profile and turnaround target to our engineering team. We will return a range and endurance estimate with its conditions stated, a trips-per-day figure, and an explicit statement of what the configuration cannot do.