fw pos ctrl params: clarify landing parameters, change defaults

FW_LND_USETER defaulted to 1 and FW_LND_ABORT terrain based bits all enabled. why? because using a distance sensor is critical to detecting when to flare, and we want to force the user to actively disable these safety settings if they so choose, so that they understand the implications.

src/modules/fw_pos_control_l1/fw_pos_control_l1_params.c

@@ -411,16 +411,17 @@ PARAM_DEFINE_FLOAT(FW_TKO_PITCH_MIN, 10.0f);
 PARAM_DEFINE_FLOAT(FW_LND_FLALT, 0.5f);
 
 /**
- * Use terrain estimate during landing.
+ * Use terrain estimate during landing. This is critical for detecting when to flare, and should be enabled if possible.
  *
- * This is turned off by default and a waypoint or return altitude is normally used (or sea level for an arbitrary land
- * position). If enabled and no measurement is found within a given timeout, the landing waypoint will be used or the
+ * If enabled and no measurement is found within a given timeout, the landing waypoint will be used or the
  * landing will be aborted, depending on the criteria set in FW_LND_ABORT.
  *
+ * If disabled, FW_LND_ABORT terrain based criteria are ignored.
+ *
  * @boolean
  * @group FW L1 Control
  */
-PARAM_DEFINE_INT32(FW_LND_USETER, 0);
+PARAM_DEFINE_INT32(FW_LND_USETER, 1);
 
 /**
  * Early landing configuration deployment
@@ -1045,7 +1046,7 @@ PARAM_DEFINE_FLOAT(FW_LND_TD_OFF, 3.0);
  * @value 0 Disable nudging
  * @value 1 Nudge approach angle
  * @value 2 Nudge approach path
- * @group FW L1 ControlW
+ * @group FW L1 Control
  */
 PARAM_DEFINE_INT32(FW_LND_NUDGE, 2);
 
@@ -1068,7 +1069,7 @@ PARAM_DEFINE_INT32(FW_LND_NUDGE, 2);
  * @bit 1 Abort if terrain times out (after a first successful measurement)
  * @group FW L1 Control
  */
-PARAM_DEFINE_INT32(FW_LND_ABORT, 0);
+PARAM_DEFINE_INT32(FW_LND_ABORT, 3);
 
 /**
  * Calculate the landing glide slope relative to the terrain estimate.