A cold westerly wind was blowing at us 11 stories above San Francisco on a rooftop that Kittyhawk sometimes uses for its flight testing. On this particular Friday Fly Day, our weekly Kittyhawk event to make sure that our code and flying skills are working in unison, as we were continuing to test the newly released DJI Spark with our Flight Deck feature.
Shortly after takeoff, a familiar voice parroted a warning from the phone:
“Attitude Mode, Attitude Mode.”
The drone that just seconds ago was leaning precariously into the wind, locked in place, started to move down wind at an alarming rate. As the VO (visual observer), I made sure to note the drone’s orientation as I saw it starting to slide away from us. I asked my Co-Founder Jon, the pilot in command, if he was ok flying in attitude mode.
“What’s attitude mode?! It’s not listening to what I’m telling it.”
I could hear panic was setting in as his expectations stopped matching reality.
The worst time to learn about a failure mode is after your aircraft has already entered it. For whatever reason, the tiny drone had lost its connection to both GPS and GLONASS and was unable to determine it’s position in space. Attitude mode means that it was only able to control its roll, pitch and yaw relative to the ground because it’s relying solely on it’s internal gyros for information. It was completely at the mercy of the wind and the control inputs of the pilot.
Since the aircraft wasn’t able to determine where it was on the earth, it couldn’t perform a return to home. Often times, pilots can refer to this as a “fly away.” A loss of navigation doesn’t seem dire unless you’ve come to depend on navigation to always be there. Many drone pilots have never flown in any other mode besides GPS mode.
As the aircraft got smaller and smaller, I took over the controls and used the iPhone’s video feed to verify that my mental orientation matched the aircraft’s orientation and started the journey back upwind to land back on our roof.
Understanding failure or diminished capability modes is an important part of drone operations. If you haven’t flown in attitude mode, or “ATTI Mode”, there a few tips and tricks that can help you learn faster and without breaking anything.
First, pick a day with little to no wind. This will give you a sense of how the aircraft is going to fly without GPS to guide it. As you gain confidence, fly in higher and higher winds. One thing that you’ll notice is that you’ll have to give inputs to stop the aircraft from flying in a direction it previously was and you’ll have to compensate for the direction the wind is blowing. Instead of the aircraft just “leaning” into the wind, you’ll have to hold the stick to compensate for the wind.
Depending on the conditions, you might find that your control inputs are unable to overcome the wind. This is because the software is capable of giving more control input to the aircraft to keep it stable than it allows the pilot too. In the event you find yourself in heavy wind, you may need to enable “sport mode” or “expert mode” to have the necessary control authority to travel back up wind.
Second, bring a safety pilot. Someone who is comfortable with a variety of aircraft and doesn’t mind flying in all sorts of modes and orientations. Have them shadow you so that if there is a problem, they can take over the controls. On that note, practice passing the controls back and forth a few times while the aircraft is still on the ground. A little practice will make sure that you can keep looking at the aircraft while passing over the controls — particularly with the larger control systems coming into favor.
From there, you can keep practicing in more and more challenging conditions. Try having your safety pilot put the drone in an odd orientation while you close your eyes. Then you need to orient it and return it to your location.
It’s important to understand what’s happening, why it’s happening, and how it will affect your drone so that the next time you unexpectedly hear “ATTITUDE MODE” you can say, “Don’t worry, I got this.”
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