I made a quad motor tail sitter which is crash now and it’s not a delta. My one is a fixed wing with all control surfaces like alerons, elevator and rudder.
Before checking transition I hover it in qoliter model and it hover in stable manner . Then I uploaded a mission which is 30 meter VTOL takeoff then waypoints then VTOL land. When I set auto mode plane do take off. After reaching desire altitude when it transit from drone to plane it when transition complete it became unstable and fall vertically in nose down orientation. I also record a video of flight and after analyzing it frame by frame I came to know that transition had been completed because when plane is falling it’s alerons are working and when aircraft transit to plane mode from drone it stay in correct plane orientation for few mili seconds and then suddenly fall vertically. Making another tailsitter is not a big deal but I want to find what happened to my design.