# VIO Issues while flying at night

Source: https://forum.modalai.com/topic/545/vio-issues-while-flying-at-night
Category: Flight Core and Legacy VOXL (https://forum.modalai.com/category/9/flight-core-and-legacy-voxl)
Tags: flight-deck
Posted: 2021-11-04 23:55:00 UTC by robocopter
Replies: 1 · Views: 796

## robocopter · 2021-11-04 23:55:00 UTC

We are having issues while night flying a large quad that has the VOXL flight deck installed.  We were doing some initial hover tests at night and noticed an aggressive drop in altitude  while in alt hold. Was able to land and kept throttle stick all the way down when it got to the ground but it took off by its self and started flying away before I was able to switch back to stabilize and manually bring it back down. 

From looking at the logs it seems that the issue is with the VIO specifically in how the Flight deck was reading altitude from what we can tell. Can someone please take a look and help us figure out how to set the system up so that it can safely fly at night and during the day without needing to turn off VIO at night?

Here is the flight log 

https://drive.google.com/file/d/1alTYrE6EGLPAuwgBMfEcT4oRYSzZFdmC/view?usp=sharing

Thank you!

## Reply by Moderator (ModalAI staff) · 2021-11-05 00:04:00 UTC

There should be no expectation that VIO will work at night, it is a computer vision system that relies on visual features. Please see details here on troubleshooting VIO: https://docs.modalai.com/flying-with-vio/#troubleshooting-vio