What to check before the first power-up

The symptom

There isn't one yet. That is the entire point of this article.

A new build is more dangerous to itself in the five seconds after the first battery connection than at any other moment in its life. Everything downstream — the tune, the maiden hover, the first pack through it — is comparatively forgiving, because by then the aircraft has already proved it does not have a short across the battery pads. What follows is a staged sequence, and the staging is the point. Each stage exists to catch a class of fault while that fault is still cheap. Skip forward and you are simply choosing to find the same fault later, at a higher price.

Work through it with the aircraft in front of you. Do not read ahead and decide which bits you already know.

Before any power at all

No battery, no USB. Nothing connected. This stage costs you ten minutes and prevents the majority of dead-on-arrival builds.

Look for shorts and stray solder strands. This is the single most likely thing to destroy a new build. A whisker of solder bridging two pads on an ESC, a strand of wire braid from a battery lead lying across the underside of the stack, a blob that has slumped between DShot pads — any of these will let the magic smoke out the instant a 6S pack delivers its opinion. Take the stack out, look at both faces of every board under good light, and use a magnifier if your eyes are over thirty. Blow the boards out with air. Solder strands migrate.

Check every joint for cold or cracked solder. A dull, grainy, ball-shaped joint has not wetted; it may conduct today and stop conducting on the third hard landing. Tug each motor wire gently. A joint that moves is a joint that will fail in flight, and a motor wire that fails in flight is a flip.

Check nothing is pinched. Wires trapped under the stack when you tightened the standoffs, wires pressed against a carbon edge, wires routed through an arm where the arm bolt clamps them. Carbon fibre is conductive and it is also sharp. A wire chafing against a carbon edge will wear through its insulation over dozens of flights and then short — long after you have forgotten this build was ever new.

Check the battery lead polarity. Twice. Out loud. Red to positive, black to negative, and verify it at the pad, not at the connector, because a connector can be crimped backwards. Reverse polarity destroys almost everything downstream of it, instantly, and it is the one mistake with no partial credit.

Check nothing metallic is touching the board. Standoffs, screw heads, a stray nut in the frame, the antenna's coax braid. Anything conductive resting on a board is a short waiting for vibration to complete it.

Check every screw is present and tight, and nothing is loose. Count the arm bolts. Shake the aircraft next to your ear. A new build should be silent.

Then get a multimeter and check continuity across the main battery pads. Set it to continuity or resistance, put a probe on each of the two main pads, and look at what it says. You want a high resistance that settles as the capacitors charge — not a beep, and not a couple of ohms. A dead short across the battery leads will destroy the build the instant you plug in, and ruling it out takes ten seconds. There is no excuse for skipping this one.

First power — no battery, no props

Power the flight controller from USB only. USB cannot supply enough current to do serious damage; it is the cheapest possible way to be wrong. Props stay off — they stay off for most of this article, and if that annoys you, read the takeoff article and see what a 5 kg aircraft does when a motor map is backwards.

Confirm the FC boots and the Configurator connects. If it does not enumerate at all, stop and go back to the previous stage — you have a fault, not a driver problem.

Check the gyro and accelerometer respond, and respond the right way round. Pick the aircraft up and tilt it. The 3D model in the Betaflight or iNAV Configurator's Setup tab must roll when you roll the aircraft and pitch when you pitch it, in the same direction, by the same amount. If the model rolls when you pitch, your board orientation is wrong and you have just found it on the bench instead of two metres above concrete. This one test catches more maidens than any other on the page.

Check the receiver. Every channel moves the right way and reaches its endpoints — roughly 1000 and 2000 at the extremes, throttle down giving you about 1000. A stick that only reaches 1150 at full deflection is an endpoint problem you want to know about now.

Check the modes and switches you configured. Flip each one and watch the mode bar light up in the Modes tab. Arm switch, angle mode, beeper, whatever you set. Confirm the arm switch is off in its default position — a switch that reads as armed at boot will lock the FC out with an ARMSWITCH flag, and you would rather learn that here than in a field.

The smoke-stopper

If you own a current-limited "smoke stopper" — a lamp or a resistive limiter in series with the battery lead — this is the moment it exists for. Use it for the first battery connection. If there is a short you missed, the limiter takes the energy instead of your ESCs, the lamp lights up brightly, and you unplug and go back to the visual inspection stage having lost nothing.

If you do not own one, they cost less than a set of props and they will eventually save you a stack. Buy one before your next build.

First power on the battery — still no props

Props off. Say it aloud. Now connect the pack, ideally through the limiter.

Listen and watch for the first two seconds. ESC startup tones, no acrid smell, nothing glowing.

Check the voltage the FC reads. Compare the Configurator's battery voltage against a meter or a cell checker. If the FC thinks a full 6S pack is at 19 V, your voltage scale is wrong, and every voltage-dependent behaviour you rely on — the warning, the low-voltage cutoff, the OSD — is lying to you.

Spin each motor, one at a time, from the Configurator's Motors tab. Not with the sticks. Confirm that the motor the firmware calls 1 is physically where the layout diagram puts it, and that each motor turns the direction the diagram wants. Numbering first, direction second — direction is meaningless until numbering is proved. With DShot you can reverse a motor in software from that tab; do not "compensate" for a wrong map anywhere else in the configuration.

Then touch everything. ESCs, motors, the regulator, the VTX. After thirty seconds of low-throttle bench spinning, nothing should be more than mildly warm. A component that is hot with the aircraft doing no work is a component that is failing.

Check arming. Disconnect the Configurator (Betaflight will not arm with MSP attached — that is deliberate), arm on the bench with props off, and confirm it arms cleanly. Then look at the arming flags: status in the CLI should give you a clean line, not a list of excuses.

Configuration checks

With the hardware proved, prove the settings.

• Motor protocol matches what your ESCs actually run. DShot600 is the usual answer; a mismatch produces desyncs under load, which look exactly like a dying ESC.
• Motor direction and board orientation — you have now verified both physically, so make sure the configuration reflects what you verified rather than what you intended.
• Battery and voltage settings — cell count detection, the warning and critical thresholds, and the capacity. These drive your low-voltage behaviour, and on a heavy build the difference between landing and falling is whether that behaviour is right.
• Failsafe — configure it deliberately. Drop, land, or return-to-home, and know which one you chose.

Then test failsafe, with props off. Arm on the bench. Turn the transmitter off. Watch what the aircraft actually does. This is not a formality: failsafe is the one feature you never exercise on purpose, which is precisely why it is so often misconfigured and discovered broken at the worst possible moment. Two minutes on the bench is the only honest test it will ever get.

Fitting props — and only now

Everything above passed. Now, and only now, props.

Correct handedness on the correct corner — handedness follows motor direction, never the other way round. Correct way up: the leading edge is the thicker, more rounded one, it faces the direction of rotation, and the printed face goes up. A correctly handed prop mounted upside down produces thrust downwards, which is a lever, and the aircraft will roll over it.

Tighten the nuts properly. On many motors the thread is handed so that the motor's own rotation tightens the nut — which means a nut on the wrong motor will steadily undo itself in flight. Check that you have the right nut on the right corner if your motors use handed threads. Torque them to the point of firm, not to the point of destroying the shaft.

Then walk round the aircraft and check all four again. This is the step people skip because they just did it.

First hover

Somewhere open. Nothing valuable downwind. Grass or soft ground, not a car park. Nobody standing where the aircraft would go if it went.

Have an escape plan and your thumb on the disarm before you touch the throttle. Then commit — a decisive, clean lift-off, not a creeping one. A multirotor has almost no control authority while a leg is still loaded, and creeping the throttle keeps it in that state for a long, dangerous second.

Hover a metre up for a few seconds. Do not fly it. Land.

Then put your hand on each motor. Warm is fine. Hot, after a few seconds of hover, means something is wrong — usually far too much D, sometimes a mechanical bind. Walk round the aircraft and look for anything that changed: a loosened prop, a moved wire, a mark where something is rubbing.

After the first flight

Re-check every screw. Things loosen. Vibration is relentless, and a brand-new build has not yet found its settled state. Arm bolts, motor screws, stack standoffs, prop nuts.

Look for vibration damage. Chafed wires, cracked joints, a soft-mount that has torn, an antenna that has migrated into a prop arc.

Pull the log. Blackbox on Betaflight or iNAV, the dataflash log on ArduPilot. You have just recorded the only flight of this airframe that has ever happened, and the gyro trace from it is your baseline. Everything you diagnose about this aircraft for the rest of its life is a comparison against that first clean hover — so take it, and keep it.