Hi Everyone, this is Gene Engelgau with Fruity Chutes. We manufacture parachute recovery systems for drones. In 2018 we were involved with the ASTM standards committee that created the specification for what it means to have a certified parachute recovery system for a drone for the purposes of flight over people, or for other high-risk use. The standard in the F.38 section is ASTM F3322-18 and is available here for purchase:
A key requirement to meet the standard is there needs to be an Automatic Trigger System (ATS) that can detect the drone failure and eject the parachute and it must be independent of the autopilot (is can work in cooperation as well so both can initiate the parachute). It standard also specifies that the drone needs to support a Flight Termination feature that when asserted by the ATS will cause the rotors to immediately stop since the parachute is being ejected. This is missing in the Ardupilot code base as far as I know, at least via an auxiliary input that the ATS can asset into the Pixhawk.
What I would like to propose is the addition of a key feature needed to support an external automatic trigger system called “Flight Termination” for the Ardupilot code base. This was recently added to the PX4 code base. Here is the pull request:
Below is the F3322-18 clause that defines the operation:
3.1.4 autonomous triggering system, ATS, n—device or components independent from any ﬂight critical system of the sUA that will detect and initiate parachute deployment upon detection of a critical failure of the sUA in ﬂight.
The ATS has it’s own IMU and other sensors that can detect the drone falling or flipping (out of control motion that should otherwise never happen). In this case the ATS will trigger the parachute.
The ATS also will generate a PWM signal that is sent to the autopilot to stop the rotors from spinning. This is called the Flight Termination System. The best and most reliable way to do this is to have the autopilot accept a PWM pulse width (or other ways can be done as well like logic level) that when asserted will cause all the rotors to immediately stop. Here is the paragraph from the standard that refers to the flight termination (stop the rotors)
3.1.16 ﬂight termination system, FTS, n—device or components that will disable the propulsion system of the sUA.
Below are several paragraphs that makes the assertions regarding these:
5.8.4 To prevent propellers from injuring people on the ground after a deployment the PRS shall also include a Flight Termination System (FTS).
126.96.36.199 The FTS shall activate at the time of or before parachute deployment is initiated.**
The FAA (and other similar government agencies in other countries) are now referring people to this standard who want waivers for flight over people. We make this device here that satisfies the ATS requirement here:
Get back to me your feedback. I can also be reached directly at email@example.com
Thanks for all of your time!!
-Gene - CEO Fruity Chutes