In-Flight Emergencies, Lost Link, GPS Failure, and Battery Fire

Spot the condition early

An in-flight emergency includes a threat to control, navigation, propulsion, battery safety, people, property, or other aircraft. End the mission early rather than waiting for a warning to become a failure.

Use a disciplined order

1. Aviate: regain safe control. 2. Navigate: assess position, hazards, airspace, and wind. 3. Communicate: alert others. 4. Document only after the immediate hazard is controlled.

Emergency deviations

Part 107 permits deviation from a rule only to the extent necessary to meet an emergency. Necessity and proportionality matter; emergency authority is not a mission-planning substitute.

Reporting is a later duty

The FAA may request a written report after an emergency deviation. Under `14 CFR 107.9`, certain serious injuries, loss of consciousness, or qualifying property damage require FAA reporting within 10 calendar days.

Plan the words and roles

Brief simple crew calls before launch: Lost link, Landing now, Aircraft inbound, and Battery emergency. Assign who flies, scans, clears the landing area, calls for help, and meets responders.

Know when to escalate

Escalate to ATC or the relevant airport facility when an airspace conflict is possible. Escalate to public safety for a threatening uncontrolled aircraft, fire, injury, or hazardous missing aircraft.

Mark usable landing areas

Identify a primary, alternate, and emergency landing area. Also identify no-go areas: crowds, roads, power lines, water, sensitive facilities, and locations where recovery would create a new hazard.

Prepare a concise report

State who, what, where, aircraft behavior, and needed assistance. Record coordinates and access details before launch; do not spend critical seconds searching for them during an event.

Separate the terms

Lost link means command-and-control connection is lost or degraded. A fly-away is unexpected uncontrolled flight. Lost link can cause a fly-away, but GNSS, compass, software, or configuration failures can also cause one.

Choose the failsafe deliberately

Hover needs safe position-holding and battery. Land needs a clear area beneath the aircraft. RTH needs reliable positioning, an accurate home point, a clear route, and sufficient battery.

RTH altitude is a route decision

Set RTH altitude to clear obstacles over both the outbound and return paths. Include terrain, trees, structures, cranes, and uncertainty. Do not assume the launch point is the route's highest ground.

Contain after recovery

If link returns, stabilize and land at the safest reachable location. Do not resume the mission. Preserve flight logs and settings; they may reveal interference, configuration errors, or a component failure.

GPS supports automation

GNSS commonly supports position hold, RTH, waypoint flight, home-point behavior, and other automated features. A displayed satellite count is useful, but it does not by itself prove the position solution is accurate.

Expect a mode change

With degraded positioning, an aircraft may enter an attitude or stabilization mode. It can remain level yet drift horizontally with wind. Releasing the sticks may no longer stop ground movement.

Immediate response

Recognize the warning, cancel automation, maintain visual orientation, correct for wind, and move toward the nearest verified clear landing area. Do not trust a map display more than direct observation.

Exam distinction

GPS loss does not automatically equal loss of control. It removes or weakens position-dependent functions. RTH may be unsafe because both route guidance and home-point accuracy can be affected.

Common C2 spectrum

Many small UAS links use unlicensed spectrum near 2.4 GHz and 5.8 GHz. Wi-Fi, Bluetooth, other UAS, and wireless devices can congest the same spectrum without anyone doing anything illegal.

Obstacles affect radio differently

Buildings, foliage, terrain, vehicles, reinforced concrete, and your body can weaken a link. Reflections can also create multipath cancellation. Visual proximity does not guarantee reliable radio communication.

Antennas and margins matter

Follow the manufacturer's antenna guidance. Keep conservative range, avoid flying behind obstructions, watch signal trends, and investigate interference sources before launch rather than treating a full signal bar as a guarantee.

VLOS remains operationally vital

VLOS lets the crew determine location, attitude, altitude, direction, hazards, and whether the aircraft endangers people or property. It is not replaced by a video feed, telemetry display, or a strong radio signal.

Situation assessment

A warehouse inspection now has three threats: a weakening control link, a positioning-mode change that may allow drift, and a possible low helicopter. Terminate the mission; collecting imagery is no longer the priority.

Stabilize with the aircraft you have

Treat position hold and automated navigation as unreliable. Keep visual orientation, apply active drift correction, and recognize that the building may be both a radio obstruction and an obstacle.

Do not make RTH automatic

The safest landing area may be the open lot on the current side of the building. RTH could require flight behind the structure using degraded navigation and a weak command link.

Yield, land, record

Yield to the approaching manned aircraft, land as soon as safely practical, then preserve warnings, logs, weather, location, and crew observations. The safest outcome governs, not the normal mission procedure.

Battery health is flight safety

Lithium batteries can fail from damage, heat, charging errors, defects, contamination, or short circuits. Thermal runaway can create self-heating, smoke, toxic gases, intense fire, and cell-to-cell propagation.

Inspect before every use

Remove from service any battery with swelling, dents, punctures, cracked insulation, damaged leads, corrosion, leakage, abnormal odor, abnormal heat, or poor fit. Never tape over damage and fly anyway.

Charge under control

Use the correct charger and settings, a noncombustible surface, ventilation, and active monitoring. Do not charge a hot or damaged pack. Let batteries cool after flight before charging or storing.

Storage and transport

Protect terminals from short circuits and follow manufacturer and carrier rules. Spare lithium batteries generally belong in carry-on baggage on passenger aircraft, not checked baggage. Never transport a damaged or overheating battery.

Recognize escalation signs

Warning signs include unusual heat, swelling, hissing, venting, chemical odor, smoke, and fire. Do not handle a smoking battery with bare hands or expose people to fumes by carrying it through an occupied area.

Life safety comes first

Stop charging only if safe, warn others, evacuate the area, stay upwind outdoors, and call emergency services for smoke, fire, injury, or an uncontrolled thermal event. Give responders the battery type and location.

Cool and monitor

For lithium-ion and lithium-polymer fires, water is widely used to cool cells and limit propagation. An extinguisher can suppress flames but may not stop internal heating. Re-ignition remains possible.

Avoid false solutions

Do not seal a hot battery in an airtight container or assume sand, a blanket, or a small extinguisher has ended thermal runaway. Do not recharge, reuse, ship, or casually discard the affected pack.

First call: terminate and assign

Say: Terminate. I have the aircraft. Scan airspace. Clear the emergency landing area. Clear role assignment prevents conflicting control inputs and preserves the visual observer's critical traffic-scanning role.

Reject automatic reactions

Do not keep filming because video looks normal. Do not climb automatically for signal. Do not use RTH by reflex if its path could cross a road, pass a crane, or depend on a degrading link.

Choose the lowest-risk outcome

Turn away from the road, yield to the manned aircraft, and land in the nearest clear area if control permits. If link is lost, the configured failsafe should support the safest anticipated containment outcome.

The exam decision pattern

Control aircraft, protect people and other aircraft, use only necessary emergency deviations, then communicate and document. This sequence is more defensible than completing the mission or following a default setting blindly.