Failed VTOL transition analysis

ArduPlane VTOL Plane
1

Hello all. After a success hover of my VTOL, I proceeded to a test transition which resulted in a crash.

The vehicle has the following characteristics:

VTOL 4+1 plane with takeoff mass of 7.5 kg.

Wingspan 2m, chord 30cm, twin Vertical Tail, ruderless.

4 VTOL motors: Sunnysky 3515S 400KV with EOLO 16X6 props.

1 pusher motor: Sunnysky V4006 320KV with folding 17X7 prop

Battery: Old Tattu LiPo 16000mAh 6S 15C (1844 grams)

Flight controller: The cube orange with Plane 4.6.3 official (with q parameters enabled)

GCS: Mission planner 1.3.83 build 1.3.9384.38258

Remote controller: Herelink v1.1

The test flight was planned to contain the following actions:

· Short transition test: (QLIOTER-> 30m altitude → FBWB for 4 seconds → QLOITER again to cancel the transition. (That was done correctly)

· Full transition and climb to 100m in order to calibrate the airspeed sensor and perform the autotune. (never managed to fully transition)

As you can see from the logs when I tried to do the full transition the vertical motors never stopped due to low airspeed which I know it is a result of the poor performance of the Sunnysky V4006 320KV pusher motor which can draw only 13Amperes@6S max at full throttle (~260W). Afterwards, in a left bank turn I lost one vertical motor and the plane crashed. The battery also is performing very poorly; the voltage dropped from 25.2V to 21.6V after only 3 minutes!!

What I would like to ask is:

  1. Which is a suitable pusher motor (&ESC) for this setup.

  2. A decent battery model which can withstand the loads.

  3. Anything else wrong that is hidden among the flight logs that I cannot spot.

Here is the flight log:

https://drive.google.com/file/d/1BKag_o0nI8yfJJotuc-JwO5JzL–d57o/view?usp=sharing

Thank you all for your valuable additions.

2

oI have a similar sized VTOL. It was rather stupid to try to fly forward on a 300 W motor. You should be able to stay in the air with around 240 W, so this leaves with a margin of 60 W… You need something which could deliver 1000 W, at least. I use Sunnysky X3520 - 560 kV with a 13 x 10 prop, although a better choice would be 14 x 10 or even 14 x 14. Your prop 17 x 7 is not good for economy, it is good for climbing.

Almost any descent ESC can be used, I use the YEP Escs, in that particular case I have one of 100 A.

One should not transition from Qloiter to FBWB. It is much safer to transition to FBWA, and also it is better to do from Qhover, and especially when you transition back.

Not sure why do you say you lost a motor, was it damaged? With the props you had I do not think that you exceeded the power or temperature of the motor.