Parachute Configuration

When a multirotor loses control in the air and starts to fall, an automatic parachute deployment brings the descent rate under 5 m/s and saves the airframe and payload.

ArduPilot's parachute feature is not limited to multirotors — helicopters, fixed-wing aircraft and VTOLs use it too, with the same parameters. Motor failure, a jammed control surface, a violent spin, a flat battery: once the pilot can no longer fly it out with attitude control, the parachute is the last line of defence.

There are three ways to trigger it: automatic on loss of control, manual from a transmitter switch, and a command from the ground station or a mission.

Hardware requirements

Parachute unit

• The release mechanism must be electrically driven: a servo, a solenoid valve or a pyro cutter all work
• A ready-made chute built for PWM servo or relay triggering is the easiest to wire and configure — Fruity Chutes, Mars Mini and SkyCat, for example
• The canopy has to be big enough: once fitted it must hold the whole aircraft below 5 m/s descent. A home-made setup is simply "a servo pulling a pin, plus a chute bag"

▲ Left: door, release spring, servo and the wiring to the controller; right: deployed

Controller interface

Two options, pick one:

Method	Connects to	Parameters
Servo (preferred)	Any free PWM output	SERVOx_FUNCTION = 27 (Parachute Release)
Relay	A free GPIO	RELAYX_PIN + RELAYX_FUNCTION = 3

Pins and wiring are covered in the next section.

Power

Give the servo (or the pyro igniter) its own BEC or battery. If the main pack comes loose or a wire is torn out, the chute still has to open — that is the whole point of the separate supply. Sharing the main pack hands the last line of defence to the system that has already failed.

Mechanical installation

• The bay door opens outward — otherwise prop wash can suck it shut
• Fire the chute upward, clear of the blades and arms, so the lines cannot tangle
• Put the bridle attachment slightly below the aircraft's centre of gravity so it does not hang upside down after deployment

Wiring

The servo signal wire goes to one of the controller's PWM outputs. Which pin SERVO9 lands on depends on whether the controller has an IOMCU:

Controller type	Pin for SERVO9
With IOMCU (outputs split into MAIN and AUX)	A1 (AUX OUT 1)
Without IOMCU (a single bank of M outputs)	M9

Check the silkscreen on the controller before wiring, and confirm which number SERVO9 maps to.

▲ X25 EVO as the example: the servo's three wires go to M9 (colour coding is in the legend), and the servo pulls the pin to release the chute

Two things to watch when triggering with a relay:

• GPIO output current is tiny — never drive a heavy load from it directly
• GPIO is low by default while the bootloader runs, so choose a mechanism that triggers on a high level and set RELAYx_DEFAULT to OFF or No Change, so powering up cannot fire the chute by accident

WARNING

Deployment is violent. Take the propellers and the chute off before any bench or ground test.

Parameters

Parameter	What it does	Values
CHUTE_ENABLED	Master switch for the parachute	0 off 1 on
CHUTE_TYPE	Release mechanism type	10 servo 0 relay
CHUTE_SERVO_ON	Servo PWM on deployment	1000 ~ 2000 µs
CHUTE_SERVO_OFF	Servo PWM at rest (not deployed)	1000 ~ 2000 µs
CHUTE_CRT_SINK	Sink rate that triggers deployment	0 ~ 15 m/s
CHUTE_ALT_MIN	Minimum height above the takeoff point for automatic deployment	0 ~ 32000 m; 0 disables the check, default 10 m
CHUTE_DELAY_MS	Delay from motor stop to deployment	0 ~ 5000 ms
CHUTE_OPTIONS	Extra behaviours, see below	bitmask

Setup steps

1. Turn it on

Set CHUTE_ENABLED to 1, then refresh parameters or reboot — the other CHUTE_ parameters only appear after that.

2. Choose the release method

Servo release

Parameter	Set to
CHUTE_TYPE	10
CHUTE_SERVO_ON	PWM that pulls the pin
CHUTE_SERVO_OFF	PWM at rest
SERVO9_FUNCTION	27 (Parachute), which is A1 or M9; for another output just shift the number, so A2 or M10 uses SERVO10_FUNCTION

Relay release

Parameter	Set to
CHUTE_TYPE	0
RELAY1_PIN	GPIO pin number for that relay
RELAY1_FUNCTION	3 (Parachute)

▲ Set the output that drives the servo to function 27 (Parachute)

3. Set the trigger conditions

• CHUTE_CRT_SINK: deploy once the sink rate reaches this value, in m/s
• CHUTE_ALT_MIN: minimum height above the takeoff point — below it there is no automatic deployment; 0 disables the height check

4. Manual deployment (optional)

Give the transmitter a switch and set that channel's RCx_OPTION to:

Value	Meaning
22	Switch high deploys the chute
23	Three-position: low = deployment disabled, middle = enabled, high = forced deployment
21	Enable/disable only: high = deployment allowed, anything else = blocked

5. Ground station or mission deployment (optional)

Use MAV_CMD_DO_PARACHUTE (command 208); parameter 1 sets the action — 0 disable, 1 enable, 2 release now. It also works as a DO_PARACHUTE waypoint in a mission.

▲ Search for CHUTE_ in the full parameter list to find these (the screenshot is an older interface; trust what you see)

When it deploys automatically

All of these must hold for a full second before it deploys:

• Armed, and not landed
• Not in FLIP or ACRO
• Roll or pitch more than 30° away from the target attitude
• The barometer shows the aircraft is not climbing
• At the moment the loss of control is first detected, higher than CHUTE_ALT_MIN (in a fast fall, the actual deployment may already be below that height)

NOTE

Too much barometer noise can make the check fail; the other way round, a false detection deploys the chute for nothing. Set the sink rate and minimum height for your own airframe — do not copy the defaults.

The two CHUTE_OPTIONS bits

Bit	Meaning
0	Hold the released state until reboot. For cold high-altitude work, where the servo or relay may be frozen and only moves once it warms up lower down
1	Do not disarm the aircraft before deploying (by default the motors are stopped and the aircraft disarmed first)

Testing deployment

Take the propellers and the chute off first; watch only the servo or relay and the ground station messages.

Manual test

1. Set CHUTE_ALT_MIN to 0 to skip the height check
2. Arm in Stabilize and raise the throttle past minimum (motors disconnected or props off)
3. Flip the transmitter switch set up above, or trigger it from the Servo / Relay screen in the ground station
4. The motors stop, the release fires and the HUD shows Parachute: Released!

Automatic test

1. Set CHUTE_ALT_MIN to 0
2. Arm and raise the throttle
3. Tilt the aircraft more than 30° while lowering it, so the barometer reading keeps falling

After about a second the motors stop, the release fires and the HUD shows Parachute: Released.

TIP

Put CHUTE_ALT_MIN back to the value you need afterwards — the factory default is 10 m.

References

• ArduPilot documentation: Parachute