A primer on the three variables that determine how a quadcopter flies. Motor KV, propeller pitch, and battery cell count aren't independent choices — picking one constrains the others, and the right combination depends on what the drone is actually for. This page covers the standard 5-inch, 7-inch, and 10-inch frame sizes Lumipad uses, and the combinations that work for crop-survey flight.
Every quadcopter's flight character comes down to how three components are matched: the motor's KV rating (how many RPM per volt), the propeller's pitch and diameter (how much air it moves per revolution), and the battery's cell count and capacity (how much voltage and energy the system gets). Pick wrong combinations and the drone either won't lift off, won't fly long, or will burn out within minutes.
Pick well-matched combinations and the drone has the thrust margin, flight time, and predictable behaviour that survey work demands. This primer documents the standard combinations for 5-inch, 7-inch, and 10-inch frames — what Lumipad uses across the cohort program and what the alumni network has converged on. It is not a complete reference; the deeper-dive handbook covering thrust curves, real-world endurance logs, and tuning is in development.
The first tab covers the underlying relationships — KV, pitch, voltage, thrust, current — so the size-specific recommendations make sense rather than feeling arbitrary. Once you understand why a 5" frame uses high-KV motors and a 10" uses low-KV, the tradeoffs become predictable rather than memorised.
The 5", 7", and 10" tabs each show typical motor / prop / battery combinations Lumipad and partner-org alumni use. These are starting points, not prescriptions. For most cohort work the 5" combinations work well; partners building for different missions may need to adjust.
Six relationships that determine how a quadcopter behaves. Once you internalise these, the size-specific tabs become quick references rather than mysteries. Trainees in Cohort 02 onward have these relationships covered in Week 1; this is the same content in handout form.
If you only remember one thing from this primer, remember this. The product of motor KV and battery max voltage is the motor's unloaded RPM. Most brushless motors safely tolerate 4000–5000 motor RPM per volt of input — not on the spec sheet, but easy to derive.
Mismatched combinations are the #1 cause of motor failures. Always check the manufacturer's spec sheet for the recommended cell count. Don't run high-KV motors on high-cell-count batteries — bearings fail, magnets demagnetise, and the smell of burnt copper is unforgettable.
The standard cohort frame. Compact, agile, easy to repair, with widely available parts. Best for surveys covering up to ~50 hectares per battery, plots within 400m of the takeoff point, and any location where a heavier drone would be impractical to transport. Every Lumipad alumnus's first build is a 5-inch.
The pattern is the classic three-way trade between thrust margin, endurance, and top speed. You can have any two; you can't have all three.
Don't try to optimise for all three at once. The temptation is real ("if I just get a higher-C battery..."). The physics doesn't permit it. Pick the variant that matches your dominant use case and accept the tradeoff in the other two dimensions.
The endurance and range variant. Roughly the same complexity to build as a 5", but with double the typical flight time and meaningfully more payload margin. Used by partner orgs running larger plot surveys, extended-range missions, and cooperatives where one drone covers 100+ hectares per session. The Lumipad Quad v1 is offered in a 7-inch variant for these contexts.
The decision is usually made by the AOI, not by preference. Three signals indicate a 7" is the right tool:
If none of the three apply, stick with the 5". The 7" is more capable but also more expensive, less agile, and less repairable. Capability you don't need is just cost you didn't have to pay.
Some partner orgs default to 7" because "bigger is better." This is usually wrong. Most cohort survey work fits comfortably in a 5"; 7" is for the specific cases where 5" runs out of capability.
The heavy-payload variant. Used by a small number of partner orgs running specialised missions: large multispectral cameras, LiDAR units, multi-sensor research rigs, post-disaster damage assessments. Crosses the CAAP 7kg threshold when fully loaded, which triggers different certification requirements — see the safety primer for the regulatory implications.
A 10A configuration loaded with sensors is at ~3.2 kg. With a heavier multispectral payload, that climbs toward 4–5 kg. With LiDAR (combo 10C), past 5 kg. None of these cross the 7 kg threshold themselves — but they're close enough that a heavier payload, a redundant battery, or an emergency parachute system pushes them over.
For most cohort and partner-org work, the 10" is overkill. It's the right tool when the sensor package demands it — but the additional regulatory burden, cost, and complexity mean nobody should default to a 10" without a clear reason. If the survey can be done at 5" or 7", do it there.
The 5/7/10 inch range covers everything Lumipad uses and almost everything partner-orgs use. But the broader quadcopter world extends well in both directions. This section provides context for trainees and partners encountering smaller or larger frames, so the design decisions remain coherent. None of these are recommended for cohort survey work.
Three real situations Cohort 02 alumni have encountered involving these out-of-standard sizes:
A common temptation: "I'll build a 13" for a cooperative because they want better cameras." Almost always wrong. The cooperative's real need is usually within 5" or 7" capability; the perceived need for "better cameras" is solved by better mission planning and the existing NDVI rig, not a more expensive frame.
The same six performance metrics across the three standard sizes. Numbers are based on the default Lumipad combinations (5A, 7A, 10A) loaded with the standard NDVI rig. Use this as a quick decision shortcut once you understand the underlying tradeoffs.
Four common scenarios alumni and partner orgs face, with the typical right answer. These are starting points for a conversation, not categorical rules — the deeper-dive handbook will cover the edge cases.
Use the 5-inch combo 5A. It's the cohort default for good reason — well-stocked parts, easy repair, light enough to transport on a motorbike, ample for plots up to ~50 hectares per session. Don't upgrade until your work consistently hits the limits of what the 5" can do.
Open the v1 5-inch BOM ↗Move to the 7-inch combo 7A or 7B. Survey time per battery roughly doubles, and the practical operating range pushes out enough to cover larger AOIs without battery-swap logistics. The cost increase is real (~₱8,000–12,000 above the 5") but proportional to the additional capability.
Open the v1 7-inch BOM ↗The 10-inch combo 10A or 10C handles research-grade payloads. Mind the regulatory implications — fully-loaded weight crosses CAAP thresholds. This is partner-org or research-grade work, not first-year alumni territory; expect a more involved certification process and dedicated equipment budget.
See safety primer for >7kg rules ↗There isn't one. The 5/7/10 sizes exist because the physics of thrust, agility, and endurance pull in different directions. Most working alumni end up with two drones — typically a 5" and a 7" — and use whichever fits the mission. One drone for everything is a budget compromise, not an engineering goal.
Stage 5 — adding a second drone ↗The 6-inch class exists in the wider hobby community but it's a compromise between the 5" and 7" without earning its keep. A 6" doesn't have the agility and parts-availability of a 5", and doesn't have the endurance and payload capacity of a 7". For survey work specifically, you almost always want one or the other.
Some FPV freestyle pilots prefer 6" for race-and-cinema combination work. That's a valid use case for that community. It's not what cohort alumni do.
Yes, with the right motors. Combo 5D in the 5-inch tab covers this — 1700KV motors instead of 2400KV, designed for the higher voltage. Don't run 2400KV motors on 6S; the bearings and magnets won't survive long.
The reason most 5" builds use 4S: it's a cheaper, lighter, simpler battery for the same effective performance. 6S 5" makes sense if you're standardising battery types across a fleet that includes 7" or 10" frames.
With the cohort default (combo 5A), 6–7 minutes of survey time is realistic. With the endurance variant (5B) and a fresh, well-charged battery, 8–9 minutes is achievable. Pushing past 9 minutes on a 5-inch usually means a heavier battery (1800+ mAh) which actually reduces flight time because the extra mass eats the gain.
If you need 10+ minutes, you've outgrown the 5-inch frame. Move to a 7-inch.
C-rating is the maximum continuous discharge rate, expressed as a multiple of the battery's capacity. A 1500 mAh 95C battery can deliver up to 1.5 × 95 = 142.5 amps continuously. During aggressive manoeuvres, four motors might draw 80–100 amps combined.
For survey work, 75–95C is plenty. Higher C ratings (120C+) are racing-territory and add cost without meaningful benefit at the throttle inputs survey work uses. Below 50C: voltage sags noticeably during direction changes; the FC reads it as "low battery" and may trigger return-to-home prematurely.
3-blade props produce more thrust at the same RPM (more blade area in the same disc), at the cost of slightly higher current draw and slightly lower top-end efficiency. For survey work — which spends most time at moderate throttle in stable flight, not at full throttle — the better thrust response is worth the small efficiency cost.
2-blade props are preferred for racing (better top-end speed) and for very long-range endurance builds where every percent of efficiency matters. 4-blade and 5-blade props exist but only suit specific niche applications.
Two failure modes:
The first failure is dangerous — a motor that demagnetises mid-flight loses control authority. Always verify motor manufacturer's recommended cell count before buying batteries.
Manufacturer thrust tables (EMAX, T-Motor, iFlight) are generally accurate to within ±10%, measured on a static thrust stand at sea level. Real flight thrust is lower because:
For survey work, build with at least 2.5:1 thrust-to-weight using manufacturer specs to maintain a real-world ratio above 2:1. The deeper-dive handbook will include real-world thrust tests with environmental corrections.
The full performance handbook is in development with target release Q3 2026. It will cover:
Use the "Notify me when handbook releases" link in the download bar to be added to the announcement list. Until then, this primer is the canonical Lumipad reference for parts decisions.