Going, Going, Gone….


Some time ago, there was a fly away in Australia that was reasonably well documented in the online media. Given that there is always something to learn from every accident, I will provide my thoughts on this one. I will apologize in advance for any incorrect conclusions I have drawn from the limited facts I have available to me.

The cause of the fly away came down to a latitude/longitude that was incorrectly entered and the GCS software assumed the northern hemisphere instead of the southern hemisphere. One single incorrect character a blank instead of an S, and as a result, the underlying map, that should have covered a small area, ended up covering thousands of kilometers.

The mission was planned using this map and so all way points ended up a thousand or so kilometers from their intended location. After launch, the UAV was flown manually for a short period of time until the radio link was unexpectedly lost. The loss of link failure engaged and the UAV started flying toward it’s preprogrammed home location, a location one thousand kilometers away.

It appears, from the data in the report, that the link was regained (the ground track shows some manual Flight and then the vehicle flying away toward it’s home location). The system had a manual mode so it should have been possible to take control of the UAV manually and return; however, from the description of the incident, it seems that engaging manual mode was complex and was not engaged in time to fly the UAV back manually.

The ground track doesn’t last long. It ends about 165 meters away from the ground station. This does not appear to be a fault in the radio link because the ground station was set up next to a hill. The hill would have blocked communications to the north and the last recorded position is consistent with the UAV flying behind the hill.

This incident has all the hallmarks of a typical aviation accident and there are a number of lessons one can learn from thus incident:

Lesson 1: It’s never just one thing
In virtually every aviation accident there is not one single cause; it’s almost always a chain of events, and if you break one link in the chain the accident doesn’t happen. In this particular incident there are actually seven factors that lead to this fly away.

1. Obviously an incorrectly georeferenced map was a major contributor.
2. The system did not warn the operators that the waypoints were unreasonably far away from the location where the UAV was initialized.
3. The operators probably hadn’t practiced emergency procedures (this is a guess).
4. The system had an overly complex procedure for taking manual control.
5. The system did not show the UAV’s GPS location relative to the programmed way points (and for that matter, map), prior to takeoff. Either that or the operator didn’t notice the inconsistency between the UAV’s Flight path and the location of the waypoints.
6. If communications hadn’t been blocked by the hill it is quite possible that the operator would have had more time to recover.
7. The manufacturer’s checklists where a bit vague and did not contain clearly defined measures to check for incorrectly Georeferenced maps.

Lesson 2: Blaming operator error isn’t helpful
A long time ago, aviation accidents were often blamed on pilot error. Certainly, in many accidents, the pilot had made a mistake. After a while, the industry came to realize that blaming the pilot was not productive. Pilots made mistakes, had always made mistakes, and would always make mistakes. And so, the goal became to surround the pilot with systems and processes that tolerated these mistakes. Here we have systems and procedures that don’t tolerate operator mistakes.

Lesson 3: Aviate, Navigate then Communicate
This is an old saying from the aviation world. Many minor incidents turned into major accidents because the pilot became distracted dealing with the emergency and simply forgot to keep flying the plane. It is possible that in their attempt to determine why their UAV was headed off in an unexpected direction the operators forgot to fly the plane (i.e. take over manual control and land the UAV manually). The facts are ambiguous on this point but this is a worthwhile topic nonetheless.

There is no mention in the report of any attempt to make contact with Air Traffic Control once the UAV had flown away. There was an airport only a few kilometers away and a warning about a UAS flying away would have been appropriate. When you fly, do you have the phone number of the nearest air traffic control in case you need it?

Lesson 4: Practice makes perfect
In piloted aviation, there is a lot of emphasis on practicing emergency procedures. It is hard to respond to an emergency if you rarely, or worse, never, practice. Timely reaction to emergencies is especially important when operating a drone as the drone is often rapidly moving away from you which limits your time to respond.

Lesson 5: Learn from every mistake
It’s a lot more pleasant (and cheaper), to learn from the mistakes of others than it is to learn from your own mistakes. There is always something to learn from every mistake but human nature means we minimize our role in any accident. This makes it more difficult to learn from our own mistakes and is where the saying ‘accidents happen’ originates. Certainly, accidents happen but many, many accidents can be prevented.

It is also valuable to look beyond the circumstances of the particular accident in question. Often when you carefully examine a particular accident you will realize there are other potential accidents that are similar. For example, this incident involves flying to an unintended location. A fly away in the horizontal direction. However, drones operate in three dimensions so there is another type of fly away – in the vertical direction. If you enter an altitude of 510 instead of 150 (transposing digits is a common data entry error), your drone will climb far above your intended altitude.

To their credit, the operators of this drone reported this incident to the authorities and clearly participated in the investigation. Hopefully, the operators have learned valuable lessons, the manufacturer of this UAV will take steps to make the system more error proof, and the wider UAV community will also learn from this incident.

For the record, MicroPilot autopilots have features that would have prevented this accident. Manual mode is simple and quick to engage and always overrides autonomous mode – no input is necessary from the GCS software. During initialization, MicroPilot autopilots check all waypoints to make sure they are a reasonable distance from the initialization point. MicroPilot autopilots are usually configured to fly back to their initialization point when they lose link and not an absolute location. We also support relative waypoints in addition to absolute waypoints, which simplifies describing how failures should be handled.

2 Replies to “Going, Going, Gone….”

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