UG35 Payload Power Planning: What a 10 kg Capacity Does Not Tell a System Integrator
By UNITED UAV Official
A sensor package can fit within an aircraft's payload mass allowance and still be an unsuitable electrical load. Its average consumption may look modest while its startup current, moving gimbal, heater or computer creates a short demand that the proposed supply cannot support. The purchasing mistake is to treat a kilogram rating as evidence that an electrical interface has already been designed and verified.
For a civil mapping or inspection project, the useful question is specific: can the exact installed package start, collect, save and shut down throughout the intended operation without exceeding its supply limits or disturbing aircraft systems? Answering that requires a power budget, a description of the interfaces and measurements tied to the proposed configuration.
The UNITED UAV UG35 is a complete fixed-wing VTOL aircraft platform whose current listing declares up to 10 kg maximum payload and 190 minutes of no-load endurance. These are separate product declarations. Neither specifies an available payload bus voltage, continuous current allowance, transient capability or flight duration with a powered mission installation. The discussion below explains how a buyer can request that missing configuration evidence.
All numerical examples in this article are hypothetical engineering worksheets. They are not UG35 electrical specifications, approved installation designs, measured aircraft performance or operating instructions. Use the delivered equipment documentation and qualified integration review for actual limits and test procedures.
- Put every load on the correct side of the power budget
Begin with a list of electrical consumers, rather than a single sensor name. An imaging head may require a companion computer, stabilization system, storage device, navigation aid, cooling fan and network adapter. Some consumers operate continuously; others change state during recording, transmission or movement. Identify which source feeds each item and which consumption figure describes its operating state.
Consider an invented package with a measurement head using 48 W, a computer using 18 W, storage using 8 W and a gimbal using 12 W. The total steady payload demand is 86 W at the equipment inputs. That total excludes any conversion losses between the aircraft supply and those inputs. It also excludes aircraft propulsion and avionics, which belong in the complete vehicle energy model.
If a hypothetical converter is 90 percent efficient at that load, upstream demand is 86 divided by 0.90, or approximately 95.6 W. The converter itself dissipates about 9.6 W. Writing 86 W in both the equipment column and the aircraft-source column would hide that loss and understate the requirement presented to the supply designer.
Give every figure a source and condition. A product's typical consumption is different from its maximum consumption; a processor's idle state is different from sustained computation; a gimbal at rest is different from one moving under load. Keep unknown values visible and request them. An empty field should not become zero because a spreadsheet needs a total.
- Build a state table before choosing a continuous rating
A useful state table describes startup, idle, acquisition, storage, transmission, mechanical movement and shutdown. For each state, record voltage limits, average input power, peak current where supplied, event duration and which other consumers may be active. The purpose is to identify combinations that a headline power figure can conceal.
For example, an instrument might draw its largest startup current just as a computer boots and a gimbal initializes. Adding unrelated individual peaks could overstate the real requirement if those events are deliberately sequenced. Assuming they never coincide could understate it if the actual startup sequence is uncontrolled. Request the sequence and evidence instead of choosing whichever arithmetic makes the proposal easier.
Suppose the hypothetical package requires 150 W at its equipment inputs during a short event. Applying the same illustrative 90 percent conversion efficiency gives approximately 166.7 W upstream. At a hypothetical 24 V source, that corresponds to about 6.94 A. At 20 V, the same input-power requirement corresponds to about 8.33 A.
These voltages do not assert that UG35 provides either rail. They demonstrate why the current budget must cover the actual permitted source-voltage range. A calculation made only at a convenient nominal voltage can miss the current requirement near the lower end of that range. Converter efficiency may also change with voltage and load, so a real design needs the relevant operating curves.
- Keep power, energy and flight endurance in separate calculations
Power describes a rate of energy use. Energy describes the accumulated requirement over time. A source can have enough stored energy for a task while being unable to supply the necessary current during startup. Conversely, a source may handle the peak current but lack the usable energy for the requested duration.
Using the example's 86 W steady equipment load for an illustrative 90-minute recording session gives 129 Wh at the payload inputs. With the assumed 90 percent conversion efficiency, the upstream requirement is about 143.3 Wh. This is an electrical-duration example, not a proposal that the aircraft can fly that mission or an instruction to allocate a particular battery reserve.
Separate continuously active time from intermittently active time. If recording, computation or transmission occurs only during certain segments, calculate the energy in each segment using its own duration and load. Include startup and shutdown energy where material. Document how the duty cycle is enforced; a hoped-for idle period is not the same as a demonstrated operating mode.
The UG35's published no-load duration cannot fill the remaining cells. An installed package changes carried mass, electrical demand, cooling requirements and potentially external drag. A configuration-specific endurance assessment must account for the whole aircraft, the actual energy system and the intended operation. Subtracting payload watt-hours from an unspecified aircraft battery and scaling 190 minutes would create an unsupported mission estimate.
- Include the harness in the voltage seen by the equipment
The voltage measured at a supply connector is not necessarily the voltage at a sensor. Wires, contacts, switches and protective devices contribute resistance. The resulting drop changes with current, and a short high-current event can expose a problem that is invisible during an idle check.
For a purely illustrative circuit, assume the complete outgoing-and-return path has 0.08 ohm resistance and carries 6 A. The voltage drop is current multiplied by resistance: 0.48 V. Resistive heating in that path is current squared multiplied by resistance: 2.88 W. Neither figure specifies a suitable cable or connector for a real installation.
The example identifies measurements a buyer should request. Record voltage at the source and at the equipment input under the relevant load conditions. Relate the lowest equipment-input voltage to its documented operating range. Record the path being tested, including the actual connector revisions and protective devices. A measurement with a short laboratory lead does not establish behavior through the installed harness.
Continuous and transient limits both matter. A connector may have application conditions related to contact arrangement, ambient temperature and installation. Protection selection also depends on the circuit and equipment requirements. Ask the responsible designer to document those decisions; do not choose a fuse or cable from the example numbers alone.
- Treat startup behavior as a measurement problem
Average-power logging can miss a brief interruption. A payload can complete most of a session yet reboot during one event, lose a file, or enter a different operating state after recovery. A demonstration that ends with a live preview does not establish that the original recording remained complete.
Request time-correlated traces appropriate to the event being investigated: supply voltage, input current and the payload's state or event marker. The measurement method must resolve the event duration. A slow dashboard trend cannot establish the absence of a faster voltage dip. The team should state the instrument, sampling method, measurement location and limits of the observation.
Distinguish an orderly commanded startup from recovery after an interrupted supply. The equipment may behave differently when power returns, including whether it restarts recording, preserves existing files or waits for operator action. Establish the required behavior before testing. File integrity and state recovery belong in acceptance alongside the electrical trace.
This is work for the responsible integration team using an approved ground-test arrangement. The worksheet does not justify improvised power interruptions on an aircraft, deliberate airborne fault injection or bypassing protective devices. A test should have defined limits, a stop condition and a person responsible for the disposition of any anomaly.
- Make the thermal calculation consistent with the electrical one
In the steady example, the converter's 9.6 W loss must leave the converter as heat. That is additional to the heat produced by the payload equipment. A payload bay with enough physical volume may still have an inadequate thermal path, particularly when components are enclosed or surrounded by insulation and structural material.
Ask what conditions support a converter's output rating. Cooling method, ambient temperature and installation can affect available continuous output. A bare rating on a component label does not document performance inside the proposed bay. The integration record should identify the mounting arrangement, thermal path and temperature limits used for each critical component.
Evaluate relevant operating states separately. Powered preparation on the ground, vertical operation and fixed-wing cruise can present different airflow conditions. The actual installation determines whether external airflow reaches a heat-generating component at all. Do not credit cooling merely because the aircraft is moving.
Useful evidence includes temperature history over an appropriately bounded test, the operating load during that test and a clear statement of the conditions. An acceptable short demonstration does not establish thermal equilibrium during a longer task. Where the payload changes operating state, explain how the thermal test represents that duty cycle and which conditions remain outside its scope.
- Close the mass and balance consequences of the power design
Power equipment consumes part of the installed mass allowance. Include conversion hardware, protection, mounting, wiring, connectors, shielding, cooling hardware and any separate energy source in the configuration's mass statement. Count each item once and state whether it is already included in an aircraft or payload mass figure.
Consider a hypothetical sensor assembly weighing 8.3 kg. Add a 0.6 kg mount, 0.35 kg converter, 0.25 kg harness and protection assembly, and 0.3 kg cooling arrangement. The installed total reaches 9.8 kg. A comparison between the sensor alone and a 10 kg headline would have hidden 1.5 kg of integration equipment.
That arithmetic does not establish that the example installation is acceptable for UG35. Payload allowance, total takeoff mass, mounting loads and balance must each be checked against the actual aircraft documentation. Keep design-growth allowance explicit; a small remaining mass difference is not automatically available for an unspecified future accessory.
Location matters as well as total mass. NASA Glenn explains center of gravity through the distribution of component weights and their distances. For an illustrative 30 kg system, moving a 2 kg component by 0.25 m along one axis shifts the calculated overall center of gravity by about 16.7 mm along that axis, if the other masses remain fixed. Only the aircraft's documented limits can establish whether a particular result is acceptable.
- Review interference and fault boundaries with the electrical interfaces
An installation changes more than watts and kilograms. Power converters, computers, radios, wiring and metallic mounts may affect neighboring systems. PX4's magnetometer documentation discusses the influence of nearby electronics and power wiring on compass measurements. That is general engineering context; it does not establish that UG35 uses PX4 or any particular compass arrangement.
Ask for a configuration-specific layout and an explanation of the relevant separation, routing, shielding and bonding decisions. Confirm the electrical reference and signal requirements of each data interface. Matching connector shapes or the word Ethernet in two brochures does not establish that the complete electrical and data paths have been verified together.
Define fault boundaries in ordinary language. If a payload branch exceeds its permitted demand, what equipment is intended to remain powered? If the payload restarts, what happens to its data and to the aircraft's ability to continue the approved recovery procedure? The answers must come from the actual architecture and its reviewed evidence.
A separate power source may alter those questions, but it creates additional mass, charging, maintenance and state-monitoring obligations. Treat shared and separate supplies as alternative designs to evaluate. Neither arrangement should be selected solely because it appears to simplify one row of the spreadsheet while moving the difficulty somewhere else.
- Buy an electrical evidence package with the aircraft configuration
A useful UG35 inquiry includes the payload's exact identity, installed mass estimate, dimensions, supply requirements, steady and transient consumption, operating sequence, data interfaces, cooling assumptions and required recording duration. If a value is not available from the payload supplier, identify it as an open question rather than supplying a plausible number.
Request a response that names the proposed source, operating voltage range, continuous and transient limits, conversion equipment, protection concept, connector details and configuration revision. Ask who owns the harness design, thermal assessment, ground verification and discrepancy closure. The quotation should distinguish the complete aircraft package from payload engineering, mission equipment and any additional testing service.
The verification scope should connect each requirement to an observation. Source capacity needs the applicable load and environmental evidence. Voltage tolerance needs measurements at the equipment input. Recording continuity needs original files and state information. Thermal suitability needs a representative duration and installation. Mass and balance need a configuration-bound statement. Agree on the acceptance criteria using the responsible equipment documentation before collecting the evidence.
Keep the no-load endurance declaration in its original role as published product context. Ask separately for the loaded configuration's assessment and any permitted demonstration. The purpose of the power worksheet is to make that discussion precise, not to manufacture a loaded flight-time promise from incomplete electrical and aerodynamic information.
For UG35 technical configuration discussions, use the current UNITED UAV product page below. Include your payload power table, startup sequence and recording requirement so the response can address a defined installation:
store.uniteduav.com/products/u…
General technical references:
NASA Glenn, Center of Gravity: www1.grc.nasa.gov/beginners-gu…
PX4, Magnetometer Hardware and Setup: docs.px4.io/main/en/gps_compas…
For integrators working with heavier civil UAV sensors, which requirement has most often changed your initial design: startup current, cooling, the installed harness, or the mass of the supporting equipment?
