5" FPV Drone keeps falling out of the sky

[noahmalin]

Hey guys,

So, I had a crash a couple of months ago and broke one of my arms. Now, I've waited for two months to finally get the replacement arm and fixed it. But now, when I tried to test fly it, the quad keeps falling out of the sky for no reason. The distance is always different, sometimes 100 m and sometimes very close (in the video its about 5 m). I didn't change any settings in Betaflight, and this quad was flying fine for two years with my settings. The motors don't get hot, and I don't see any physical damage to the drone. Nothing is touching the props. I have the blackbox file attached with my latest test flight dvr video.
Just after the quad disarms, you can see that rxSignalReceived and rxFlightChannelsValid are still 1 and that failsafePhase is still 0. So, the flight controller itself isn't seeing a failsafe condition. It looks like it just disarms for some reason.
Does anyone know what could cause this? Thanks!

https://drive.google.com/drive/folders/1...sp=sharing


5 Inch X Hover Blastr V2
T-Motor F7 Stack - F7 FC, F55A PRO II 3-6S 4-in-1 ESC Combo
DJI Airunit
TBS Crossfire Nano RX, with immortal T antenna
Tango 2
4 x XNOVA 2207 FREESTYLE SMOOTH LINE MOTORS 1700 kv

Tattu R-Line batteries 6s 1800 mAh and 1400 mAh






# version

# Betaflight / STM32F7X2 (S7X2) 4.3.0 Jan 25 2022 / 12:40:47 (2e4f1c922) MSP API: 1.44

# config: manufacturer_id: TMTR, board_name: TMOTORF7, version: c2b8c0d3, date: 2021-06-18T03:42:42Z



# start the command batch

batch start



board_name TMOTORF7

manufacturer_id TMTR



# name: LINK QUALITY



# feature

feature -RX_PARALLEL_PWM

feature RX_SERIAL

feature GPS

feature TELEMETRY



# serial

serial 1 1 115200 57600 0 115200

serial 3 2 115200 57600 0 115200

serial 4 64 115200 57600 0 115200



# beeper

beeper -DISARMING

beeper -ARMING

beeper -ARMING_GPS_FIX

beeper -ARMED



# beacon

beacon RX_LOST

beacon RX_SET



# aux

aux 0 0 0 1700 2100 0 0

aux 1 1 2 1300 1700 0 0

aux 2 2 2 1700 2100 0 0

aux 3 46 3 1700 2100 0 0

aux 4 13 1 1700 2100 0 0

aux 5 35 1 1300 1700 0 0



# master

set acc_calibration = 50,53,86,1

set mag_hardware = NONE

set baro_hardware = NONE

set min_check = 1010

set max_check = 1990

set serialrx_provider = CRSF

set blackbox_sample_rate = 1/8

set blackbox_device = NONE

set dshot_bidir = ON

set motor_pwm_protocol = DSHOT600

set failsafe_procedure = GPS-RESCUE

set yaw_motors_reversed = ON

set small_angle = 180

set gps_provider = UBLOX

set gps_ublox_use_galileo = ON

set gps_set_home_point_once = ON

set gps_rescue_initial_alt = 88

set gps_rescue_descent_dist = 88

set gps_rescue_sanity_checks = RESCUE_SANITY_FS_ONLY

set gps_rescue_min_sats = 6

set gps_rescue_min_dth = 50

set gps_rescue_allow_arming_without_fix = ON

set osd_warn_batt_not_full = OFF

set osd_warn_core_temp = OFF

set osd_warn_rc_smoothing = OFF

set osd_warn_launch_control = OFF

set osd_warn_link_quality = ON

set osd_vbat_pos = 497

set osd_rssi_pos = 417

set osd_link_quality_pos = 2476

set osd_rssi_dbm_pos = 434

set osd_flymode_pos = 2401

set osd_current_pos = 128

set osd_mah_drawn_pos = 2534

set osd_craft_name_pos = 2465

set osd_display_name_pos = 395

set osd_gps_speed_pos = 2057

set osd_gps_lon_pos = 2080

set osd_gps_lat_pos = 2048

set osd_gps_sats_pos = 2433

set osd_home_dir_pos = 2061

set osd_home_dist_pos = 2062

set osd_altitude_pos = 2064

set osd_warnings_pos = 2377

set osd_avg_cell_voltage_pos = 2537

set osd_battery_usage_pos = 490

set debug_mode = GYRO_SCALED

set name = LINK QUALITY

set display_name = Noah Malin



profile 0



# profile 0

set vbat_sag_compensation = 40

set iterm_relax_cutoff = 10

set yaw_lowpass_hz = 70

set throttle_boost_cutoff = 10

set p_pitch = 64

set d_pitch = 54

set p_roll = 59

set d_roll = 50

set p_yaw = 63

set d_min_roll = 0

set d_min_pitch = 0

set feedforward_transition = 40



rateprofile 0



# rateprofile 0

set roll_rc_rate = 15

set pitch_rc_rate = 15

set yaw_rc_rate = 15

set roll_srate = 65

set pitch_srate = 65

set yaw_srate = 65



# end the command batch
batch end

 

[Liam B]

Looks like it flies quite well from the DVR you provided. At 1:05 in the video, you gave it a pretty good amount of gas and it didn't stutter then like I thought it might. A few things I noticed you didn't mention checking... are the motor screws touching the windings perhaps? I know that's something that could happen after an arm swap. Maybe in the crash, the speed controller was damaged? Do you have another to check this? I know it isn't probably your favorite advice you'll get, but if it's flying well on those PIDs and just being spontaneous in reliability, maybe replace the stack? I doubt the issue would follow

 

[noahmalin]

First of all, thank you for your help! Unfortunately, that doesn't seem to be the issue. I've checked all my motors, connectors, and wires. I just bought a new FC and ESC; I think that should solve the problem.

 

[mastermalpass]

My racing quad started cutting out randomly as well. I eventually discovered it happened when the motors exceeded a certain throttle level when I had the auto-level enabled:

I have yet to properly try the solution as the recommended tip was to re-flash the firmware. Thing is, binding this quad to my Spektrum was a ball-ache and I can't remember how I did it. Didn't manage to get it to bind again when I tried and now I have a FlySky FS-i6x I'm thinking I'll just get one of those receivers for it. When I got my Spektrum DX6i, quadcopters weren't really a thing yet. However, with it plugged into the computer, I can send the throttle up to 100% and that didn't cause it to cut out, so it's not that one of the ESCs is doing an emergency cut-off.

 

[Liam B]

First of all, thank you for your help! Unfortunately, that doesn't seem to be the issue. I've checked all my motors, connectors, and wires. I just bought a new FC and ESC; I think that should solve the problem.

Yeah as much as it stinks sometimes...: when in doubt, change it out. Especially with the big drones and semi-reliable components, its best to swap before it completely dies above water or at a high altitude.

 

[noahmalin]

Hey guys, thanks for all the answers!

So, I finally found the solution. The arming switch was twitching; when I opened the modes tab in Betaflight and armed the quad, it was twitching on and off. So, I flashed the FC, and that solved the problem. Hope this helps someone with a similar problem.

 

[Liam B]

Hey guys, thanks for all the answers!

So, I finally found the solution. The arming switch was twitching; when I opened the modes tab in Betaflight and armed the quad, it was twitching on and off. So, I flashed the FC, and that solved the problem. Hope this helps someone with a similar problem.

That has to be the weirdest issue I've heard... but luckily easily solvable. You're sure it's not the actual radio switch and just the firmware?