# 返航模式

The Return flight mode causes the vehicle to ascend to a safe height, then return to its home position where it may then either wait (hover or circle) or land.

## 多旋翼（MC）

A copter/multi-rotor will first ascend to the return altitude (by default, RTL_RETURN_ALT) and then fly to the home position in a straight line and constant altitude (if already above the return altitude it will return at its current altitude).

The required return altitude can be configured using using the parameters RTL_RETURN_ALT and RTL_CONE_ANG (which define a half cone centered around the home position).

If the vehicles is:

• Above RTL_RETURN_ALT (1) it will return at its current altitude.
• Below the cone it will return where it intersects the cone (2) or RTL_DESCEND_ALT (whichever is higher).
• Outside the cone (3) it will first climb until it reaches RTL_RETURN_ALT.
• Inside the cone:

Note:

• If RTL_CONE_ANG is 0 degrees there is no "cone":
• the vehicle returns at RTL_RETURN_ALT (or above).
• This is the default behaviour.
• If RTL_CONE_ANG is 90 degrees the vehicle will return at the greater of RTL_DESCEND_ALT and the current altitude.
• The vehicle will always ascend at least RTL_DESCEND_ALT for the return.

RC stick movement will by default change the vehicle to Position mode unless handling a critical battery failsafe.

The RTL behaviour can be configured using the parameters below.

RTL_RETURN_ALT Return altitude in meters (default: 60m) when RTL_CONE_ANG is 0. If already above this value the vehicle will return at its current altitude.
RTL_DESCEND_ALT Minimum return altitude and altitude at which the vehicle will slow or stop its initial descent from a higher return altitude (default: 30m)
RTL_LAND_DELAY Time to hover at RTL_DESCEND_ALT before landing (default: 0.5s) -by default this period is short so that the vehicle will simply slow and then land immediately. 如果设置为-1, 系统将在 RTL_DESCEND_ALT 徘徊, 而不是降落。 The delay is provided to allow you to configure time for landing gear to be deployed (triggered automatically).
RTL_MIN_DIST Minimum horizontal distance from home position to trigger ascent to the return altitude specified by the "cone". If the vehicle is horizontally closer than this distance to home, it will return at its current altitude or RTL_DESCEND_ALT (whichever is higher) instead of first ascending to RTL_RETURN_ALT).
RTL_CONE_ANG Half-angle of the cone that defines the vehicle RTL return altitude. Values (in degrees): 0, 25, 45, 65, 80, 90. Note that 0 is "no cone" (always return at RTL_RETURN_ALT or higher), while 90 indicates that the vehicle must return at the current altitude or RTL_DESCEND_ALT (whichever is higher).
COM_RC_OVERRIDE If enabled stick movement gives control back to the pilot in Position mode (except when vehicle is handling a critical battery failsafe). Enabled by default.

## 固定翼（FW）

A fixed-wing aircraft behaves the same as a multicopter on the return trip (respecting the same parameters). The only difference is that on arrival the vehicle will, by default, circle above the home position rather than hover/land. If RTL_LAND_DELAY is set to -1 the vehicle will land as described in the topic: Landing (Fixed Wing). RC stick movement is ignored.

The following additional parameters affect return mode on fixed wing: