Human safety must be the top priority. Aircraft can be replaced. People cannot. Always prioritize the safety of yourself and others over the preservation of aircraft or equipment.
Emergency situations are dynamic events, that will not often conform perfectly to the categories listed below. A thorough understanding of aircraft systems, proficiency in piloting the aircraft, and sound judgment will allow you to bring about the best possible outcome in an emergency.
In general, if an emergency occurs, three basic actions can be applied to most situations:
Maintain aircraft control — Small emergencies can quickly escalate if the pilot is distracted attempting to troubleshoot the problem. Always maintain visual contact with the aircraft during an emergency to reduce the likelihood of losing orientation.
Analyze the situation — Once the aircraft is stabilized, assess the cause of the emergency.
Take appropriate action — In many cases, the appropriate action will be to land the aircraft as soon as possible.
Do not be over-reliant on Return Mode in emergency situations. The cause of the emergency may degrade performance or disable Return Mode. For example, loss of GPS disables Return Mode.
Error and Warning Indication
The aircraft communicates the presence of errors and warnings primarily though Auterion Mission Control (AMC) status indicators on Herelink or PC. Many messages are accompanied by an audible message (e.g. "Return Flight Mode"). Additionally, Astro boom LEDs will flash when the battery level is low.
Status messages, including errors and warnings, are stored in Flight Logs. After any emergency, review the log to determine the source of the problem.
Some situations are discussed in more detail below.
Loss of Orientation
If orientation is lost, neutralize inputs and activate position mode. Then work to identify the front of the aircraft.
We recommend identifying the front of the aircraft via a "guess and check" method of small roll right inputs alternating with yawing the aircraft 90 degrees at a time. We recommend a roll input rather than pitch because at a distance it is easier to see lateral motion than fore/aft motion.
If it is not possible to identify orientation, and it is safe to activate Return Mode, do so. By default in Return Mode, after climbing, the aircraft will yaw to put the front toward the direction of flight.
Resume flying or land as necessary.
Unexpected Aircraft Behavior
If Astro behaves unexpectedly, do the following: neutralize inputs, activate Position Mode, and observe the aircraft. If it is still flying in an uncommanded manner in Position or Altitude Mode, switch to Manual Mode.
In some cases, unexpected behavior is due to degraded GPS signal or erroneous sensor readings (e.g. compass error). In such cases, Return Mode may not behave reliably. Manual Mode does not rely on these sensors.
Land as soon as possible.
Landing Detector Failure
If the aircraft touches down, but hops back up into the air several times, or sits on the ground with the props continuing to spin, the autopilot may not have detected a landing. Climb and retry landing with a greater downward velocity.
Landing the aircraft firmly will give the accelerometers and gyroscopes a sufficient contrast between flight and landing.
If landing is unsuccessful in Position and Altitude mode, land in Manual Mode.
If landing is unsuccessful in Manual Mode, perform an Emergency Stop with the aircraft on the ground or as close as possible.
TODO: Check flight > landing section. Does it explain how landing is detected?
Loss of GPS
If GPS is lost, flight modes that rely on GPS (Position, Return, Mission, etc) will not be available. If the aircraft is in one of these modes when GPS is lost, the autopilot will switch to Altitude Mode.
It is the pilot's responsibility to be proficient with Altitude and Manual Mode, and to have the aircraft configured to behave safely if GPS is lost.
Examples of behavior without GPS:
If GPS is not available upon arming, no Home Point is set, and Return Mode is not available. Even if GPS becomes available while flying, Return Mode will not be available.
If the pilot commands Return Mode, the aircraft will remain in Altitude or Manual Mode, and an error will be displayed on the pilot handset.
If Land Mode is activated (e.g. by a failsafe), the aircraft will descend as though in Altitude mode, maintaining level attitude but drifting with the wind. (Land mode cannot be activated by the pilot because Land Mode requires GPS).
If GPS is lost during a mission, the aircraft will display a warning and switch flight mode to either Altitude Mode or Manual Mode, depending on the degradation of the signal.
If GPS is providing altitude information (e.g. while using RTK GPS), and GPS is lost, the ability of Altitude Mode to accurately maintain altitude may be affected.
RC Loss of Signal (LOS)
RC Loss of Signal (LOS) can occur if the pilot handset signal is degraded or stops, or if Astro does not receive the signal due to distance or interference (e.g. from obstacles or other radio signals).
If the signal is lost longer than the RC Timeout, a failsafe action will be triggered. The RC Timeout is quite short by default: 0.5 seconds. The pilot may not have time to react before the the failsafe action is activated. The failsafe action be default is Return Mode.
If the signal is lost, check pilot's handset power and antenna orientation. Antenna orientation is especially important when Astro is far from the pilot.
If the signal is recovered, the pilot will be able to take control via moving the sticks or pressing a flight mode button.
RC Loss of Signal (LOS) is differentiated from Data Link Loss. LOS refers to the stream of SBUS data containing the pilot's inputs. Data Link refers to the stream of MavLINK messages. Astro routes both data streams through a single radio system. Please note that the AMC app needs to be in the foreground on the Herelink during operation; Data Link will fail after 30 seconds and trigger a failsafe if the AMC app is closed or running in the background.
Loss of Video Signal
Loss of Video Signal can occur if the aircraft flies out of range or if it flies behind an object that interrupts the signal. Maintaining visual contact is the preferred method to re-establish control of the aircraft, either with the pilot seeing the aircraft, or by the use of a visual observer.
Yawing the aircraft can help signal reception if the body of the aircraft is blocking the line of sight between the transmitter and receiver antennas.
If video signal or visual contact cannot be re-established, enable Return Mode to bring the aircraft back to signal reception range.
It is the responsibility of the pilot to see and avoid other aircraft, people, or obstacles. Always maintain direct line of sight with Astro during flight, use visual observers as operations require, and follow local regulations regarding see-and-avoid requirements.
As a last resort, if it is not possible to land or control the aircraft, perform an Emergency Stop. If performed while flying, this will cause the aircraft to crash. Perform the Emergency Stop as far away from people as possible.
Emergency Stop is a last resort. It will cause a loss of control and a crash.
Failsafe behavior and settings are configured in AMC. The AMC documentation covers each failsafe and related settings in detail.
Some failsafes are discussed briefly below.
We strongly recommend using the default settings, changing only Return Altitude, unless you are an expert user and have tested the effect of changes thoroughly.
Battery level is evaluated from the State of Charge (SoC, e.g. 72%), not voltage (e.g. 23 Volts).
As the battery level becomes low, the autopilot can take action. The default settings do not interfere until the battery becomes quite low. Additionally, low battery failsafes have no knowledge of the aircraft's position or distance from the Home Point. This means it is the pilot's responsibility to be aware of the battery level and ensure the aircraft is on the ground.
Warning: Flash boom LEDs
When activated by a low battery failsafe, Return and Land Mode cannot be overridden by stick movement. They can be overridden by pressing a flight mode button (e.g. Position).