# Heavy Quad arm (MotorsX8 coaxial multirotor) - Crashed **URL:** \ **Category:** Pixhawk\ **Created:** [February 6, 2026, 10:31am UTC](https://discuss.px4.io/t/heavy-quad-arm-motorsx8-coaxial-multirotor-crashed/48435 "2026-02-06T10:31:34Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![dasigjp2025](https://discuss.px4.io/user_avatar/discuss.px4.io/dasigjp2025/32/19094_2.png) [@dasigjp2025](https://discuss.px4.io/u/dasigjp2025)\ **Post date:** [February 6, 2026, 10:31am UTC](https://discuss.px4.io/t/heavy-quad-arm-motorsx8-coaxial-multirotor-crashed/48435/1 "2026-02-06T10:31:34Z")
Good Day! MotorsX8 coaxial multirotor Drone crashed during its 1st flight test. What could be the possible problem that I need to check before I perform another flight test for this drone? Params and Logs Files : [RP-U515B \_ MT50 Delivery Drone - Google Drive](https://drive.google.com/drive/folders/186kOR9aU5kjo324B8jeJIg-KyXzFVTAi?usp=sharing) Battery Used is (1s2p) Tattu 14s 30000mAh ( so 2 pcs of 14s in parallel connection) FC : Pixhawk 6c + Holybro PM08-CAN Power Module 14S, 200A RC : Siyi Mk15 Telemetry : Holybro SiK Telemetry Radio - Long Range 1W 915MHz GPS : M10 GPS/GNSS Drone Frame Specifications ![image](https://discuss.px4.io/uploads/default/original/3X/8/c/8cffd705327ef0af6a4d4bab799978e745bc93b3.png) ![image](https://discuss.px4.io/uploads/default/original/3X/c/4/c48c46b69e32b500e634644388cf92fcea52667f.png) I followed the PX4 guidelines in the Qgroundcontrol. I was able to configure and tune drones with total weight of 10kg ( quadrotor Drone) without problem. but this heavy drone that can carry of upto 50kg fails on its 1st flight. We have done calibrations too before flight test. What could be the problem and what should I be looking for? ---
**Author:** ![dasigjp2025](https://discuss.px4.io/user_avatar/discuss.px4.io/dasigjp2025/32/19094_2.png) [@dasigjp2025](https://discuss.px4.io/u/dasigjp2025)\ **Post date:** [February 6, 2026, 5:58pm UTC](https://discuss.px4.io/t/heavy-quad-arm-motorsx8-coaxial-multirotor-crashed/48435/2 "2026-02-06T17:58:40Z")
![image](https://discuss.px4.io/uploads/default/original/3X/3/1/31deb11cbb4b9cfc137a2cd740791d239dc62dd6.png) Im thinking this might be the problem.. Ill check it . ---
**Author:** ![dasigjp2025](https://discuss.px4.io/user_avatar/discuss.px4.io/dasigjp2025/32/19094_2.png) [@dasigjp2025](https://discuss.px4.io/u/dasigjp2025)\ **Post date:** [February 7, 2026, 4:31am UTC](https://discuss.px4.io/t/heavy-quad-arm-motorsx8-coaxial-multirotor-crashed/48435/3 "2026-02-07T04:31:47Z")
This is the exact frame we used. ![1000004823](https://discuss.px4.io/uploads/default/original/3X/f/1/f1b6fe044cef843814bd640eea222c2eba871bbe.jpeg) ---
**Author:** ![dasigjp2025](https://discuss.px4.io/user_avatar/discuss.px4.io/dasigjp2025/32/19094_2.png) [@dasigjp2025](https://discuss.px4.io/u/dasigjp2025)\ **Post date:** [February 7, 2026, 4:54am UTC](https://discuss.px4.io/t/heavy-quad-arm-motorsx8-coaxial-multirotor-crashed/48435/4 "2026-02-07T04:54:13Z")
How to measure the motor position for KM? Also the PY/Z axis value? ![image](https://discuss.px4.io/uploads/default/original/3X/a/a/aaccacf8cde2eb13a2ae02799cfd213516afccd2.png) ---
**Author:** ![Dr.Gadget](https://discuss.px4.io/user_avatar/discuss.px4.io/dr.gadget/32/19068_2.png) [@Dr.Gadget](https://discuss.px4.io/u/Dr.Gadget)\ **Post date:** [February 7, 2026, 10:34pm UTC](https://discuss.px4.io/t/heavy-quad-arm-motorsx8-coaxial-multirotor-crashed/48435/5 "2026-02-07T22:34:08Z")
When posting logs, use Flight Reivew, like this: [https://review.px4.io/plot\_app?log=09cbd0ca-0d4a-4015-8d7d-7988e8f564df](https://review.px4.io/plot_app?log=09cbd0ca-0d4a-4015-8d7d-7988e8f564df) (this is your log) It looks like your Mag was not happy ![image](https://discuss.px4.io/uploads/default/original/3X/5/8/589040f34ea4699dc6ab76db02e377b22ae0c4a1.png) Looking at thrust (current to motors) vs mag field is very correlated, this is bad. This will casue the EKF2 internal estimator to get wrong readings and ignore the magnetometer. Most likely, the motor cables are too close to the MAG. I would suggest using an external (e.g in gps) or standalone. The orange should be mostly flast, only 5-15% changes. ![image](https://discuss.px4.io/uploads/default/original/3X/6/a/6a63960dc78576fa529bf222b095b6e194f8278b.png) Lots of saturation on the motors aswell ![image](https://discuss.px4.io/uploads/default/original/3X/d/8/d8d5ea187f6682407d27adfab247f6fcadfc902f.png) I haven’t done the math but with such high potential thrust you might be running into the problem of not being able to give low enough thrust on the motors. The motors have to spin a certain speed to not stall or produce uneven lift. There is also a minimum thrust `MPC_THR_MIN` and` MPC_MANTHR_MIN` One of the best tips I can give you is to build a good testing rigg where the drone can be attached and spin withuot damanging anything. It can be as easy as a steel bar where the drone can only rotate in 1 way. This will let you test props direction, thrust, mag, some initial flight stability etc before doing real world tests. This is **VERY** large, costly and dangerous drone and the according tests have to be done ---
**Author:** ![Dr.Gadget](https://discuss.px4.io/user_avatar/discuss.px4.io/dr.gadget/32/19068_2.png) [@Dr.Gadget](https://discuss.px4.io/u/Dr.Gadget)\ **Post date:** [February 7, 2026, 10:38pm UTC](https://discuss.px4.io/t/heavy-quad-arm-motorsx8-coaxial-multirotor-crashed/48435/6 "2026-02-07T22:38:05Z")
A few other notes regarding large platforms: - Large drones create alot of noise, both on gyro and acc. There needs to be sufficient filtering, often both hardware and software. Motors are only 70 KV meaning they produce very low frequency noise, especially on low throttle. Those blue dampener might be too stiff. - Gyro filters too high to filter noise atm, try ` IMU_DGYRO_CUTOFF = 12Hz`, `IMU_GYRO_CUTOFF = 20Hz, prob need to calculate for best performance but it is a start. Lower accel filter aswell `IMU\_ACCEL\_CUTOFF = 10` - Notch filters (RPM based) could help alot (requires DSHOT telem or CAN telem). They allow higher LP filters for less delay while still filtering well. - With large propellers and linear throttle ESC (usually all are) the throttle to thrust relationship is not linear. This creates a huge effect at low and high throttle. I would suggest setting `THR_MDL_FAC = [0.7,0.85]`. Here is some good info: [Tuning Process Instructions — Plane documentation](https://ardupilot.org/plane/docs/quadplane-vtol-tuning-process.html) ---
**Author:** ![dasigjp2025](https://discuss.px4.io/user_avatar/discuss.px4.io/dasigjp2025/32/19094_2.png) [@dasigjp2025](https://discuss.px4.io/u/dasigjp2025)\ **Post date:** [February 9, 2026, 9:32am UTC](https://discuss.px4.io/t/heavy-quad-arm-motorsx8-coaxial-multirotor-crashed/48435/7 "2026-02-09T09:32:20Z")
Hello thank you for the reply. Ill try to change the dampener on the flight controller also will try to make some changes on the layout of the components to reduce the noise also the frame we used is JIS M50 which is custom made to 8 motors > **[JIS M50 Delivery Drone - 60 Minutes 50KG Payload](https://rcdrone.top/blogs/articles/jis-m50-delivery-drone-60-minutes-50kg-payload)** > > JIS M50 Delivery Drone Overview The JIS M50 Delivery Drone is engineered for robust and efficient delivery operations, offering high payload capacity, advanced navigation features, and superior flight performance. This drone is optimized for... ---
**Author:** ![dasigjp2025](https://discuss.px4.io/user_avatar/discuss.px4.io/dasigjp2025/32/19094_2.png) [@dasigjp2025](https://discuss.px4.io/u/dasigjp2025)\ **Post date:** [March 1, 2026, 6:33am UTC](https://discuss.px4.io/t/heavy-quad-arm-motorsx8-coaxial-multirotor-crashed/48435/8 "2026-03-01T06:33:53Z")
hello again, my ordered propellers for this drone has not been delivered also the hinges on its arm. but for now Im going to re-arrange the wiring cables especially the arrangement of the components in the top plate. Ill also do some drain test making sure vibrations and electrical interference is reduced as much as possible. ---
**Author:** ![dasigjp2025](https://discuss.px4.io/user_avatar/discuss.px4.io/dasigjp2025/32/19094_2.png) [@dasigjp2025](https://discuss.px4.io/u/dasigjp2025)\ **Post date:** [April 22, 2026, 3:33pm UTC](https://discuss.px4.io/t/heavy-quad-arm-motorsx8-coaxial-multirotor-crashed/48435/9 "2026-04-22T15:33:25Z")
I looked at the specification and watched the recorded flight test and I think one of the major problem is the power lost. I seeing that in the video, the motor is losing power when trying to lift up. then base on the specification of the motors which Hobbywing H11MD it really is needing larger battery packs with higher Discharge rate since at the time of the video the Drone’s battery being used is 14s 30Ah - 5c . Currently Im looking for a Battery pack that is 14s 66Ah 10c that can still fit in the battery cage so I dont need to modify the cage. Other than that I have already set parameters based on your suggestion and research on the documentation ---
**Author:** ![system](https://discuss.px4.io/uploads/default/original/3X/7/3/73ce918bdcd64854de904f0c8d9ab70ca9723f2a.png) [@system](https://discuss.px4.io/u/system)\ **Post date:** [July 21, 2026, 3:33pm UTC](https://discuss.px4.io/t/heavy-quad-arm-motorsx8-coaxial-multirotor-crashed/48435/10 "2026-07-21T15:33:48Z")
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