Loss of GPS Signal
Most small UAS pilots have come to rely heavily on GPS without fully realizing it — position hold, smooth hovering, and automatic return-to-home all depend on it. This lesson has no dedicated Part 107 regulation covering GPS loss specifically; it is grounded in 14 CFR 107.19's ongoing remote-pilot responsibility and 107.21's deviation authority if needed, but the real safety backstop is a regulation this course has not yet covered in full: 14 CFR 107.31, the visual-line-of-sight requirement, which this lesson explains completely.
What GPS does for a small UAS
GPS (Global Positioning System) gives a small UAS's flight controller a continuous estimate of its own position, and this feeds several capabilities pilots often take for granted: position hold (the aircraft actively corrects for wind to stay in one spot rather than drifting), smooth and precise waypoint navigation, and automatic return-to-home, which requires knowing both the aircraft's current position and its recorded home point. None of these capabilities is a legal requirement under Part 107 — they are conveniences built on top of GPS, and Part 107 was written assuming they might not always be available.
What happens when GPS signal is lost or degraded
When GPS signal is lost, most modern flight controllers automatically switch to an alternative flight mode, commonly called ATTI (attitude) mode. In ATTI mode, the aircraft still uses its barometer to hold altitude and its gyroscopes and accelerometers to hold a level attitude, but it can no longer actively correct for horizontal drift caused by wind, since it no longer has a reliable position reference. The practical result: the aircraft will drift with the wind unless the remote pilot manually corrects for that drift using the control sticks, continuously, for as long as GPS remains unavailable. A pilot who has only ever flown in GPS-assisted mode and has never practiced ATTI-mode flying can find this genuinely difficult to manage smoothly the first time it happens for real.
Common causes of GPS signal loss
GPS loss or degradation can result from several distinct causes. Dense urban canyons and tall buildings can block or reflect satellite signals, reducing the number of usable satellites below what the receiver needs for a reliable position fix. Flying near large metal structures or heavy machinery can interfere with the antenna's reception. Solar activity and ionospheric disturbances can occasionally degrade GPS accuracy across a wide area. And in rare, specific circumstances near certain sensitive facilities, GPS jamming or spoofing can deliberately disrupt or corrupt the signal a receiver picks up.
Why GPS loss does not remove any Part 107 obligation
This is the central point of this lesson: nothing about a GPS signal loss changes what Part 107 already requires of a remote pilot. The remote pilot was already required, under 14 CFR 107.31, to maintain the aircraft within unaided visual line of sight throughout the entire flight, specifically so that the aircraft's location, attitude, altitude, and direction of flight can be determined visually — independent of any onboard sensor, GPS included. A remote pilot who has genuinely been complying with 107.31 all along already has the visual information needed to fly the aircraft manually and safely without GPS; the loss of GPS removes a convenience, not the pilot's fundamental ability to keep the aircraft under control.
The regulation's exact text
Because this regulation is the real backstop for a GPS-loss situation, it is worth explaining completely here, not simply cited in passing. It reads, in full:
(1) Know the unmanned aircraft's location;
(2) Determine the unmanned aircraft's attitude, altitude, and direction of flight;
(3) Observe the airspace for other air traffic or hazards; and
(4) Determine that the unmanned aircraft does not endanger the life or property of another.
14 CFR 107.31(b) — Throughout the entire flight of the small unmanned aircraft, the ability described in paragraph (a) of this section must be exercised by either:
(1) The remote pilot in command and the person manipulating the flight controls of the small unmanned aircraft system, if the latter is not the remote pilot in command; or
(2) A visual observer.
Unpacking what 107.31(a) actually requires
Note the phrase "unaided by any device other than corrective lenses" — this means eyeglasses or contact lenses are fine, but binoculars, FPV goggles used as the sole means of maintaining the required visual capability, or any other visual-enhancing device do not satisfy 107.31 on their own. The four numbered items in 107.31(a) describe exactly what that unaided vision must let someone determine: where the aircraft is, its attitude/altitude/direction, the surrounding airspace for hazards, and whether it endangers anyone. These are precisely the pieces of information a GPS-equipped flight controller also tracks internally — which is why a pilot genuinely maintaining VLOS already has an independent, human backup to the aircraft's own GPS-based self-awareness.
107.31(b): who must exercise this ability
107.31(b) clarifies that this visual capability does not have to rest entirely on the remote pilot in command personally — it can be exercised by the remote pilot together with the person manipulating the controls (if that is a different individual), or by a dedicated visual observer. What it cannot be is exercised by no one, or satisfied purely through a video feed or GPS telemetry on a screen. The human, unaided-eye connection to the aircraft is what 107.31 actually requires, and it is precisely that connection that makes manual, GPS-free flying possible when it becomes necessary.
Worked scenario: applying VLOS during a GPS dropout
You are flying a rooftop inspection when the aircraft's display shows a sudden drop in the number of satellites acquired and a warning that GPS mode is no longer available; the aircraft switches automatically to ATTI mode and begins drifting slightly with a light crosswind. Because you have been maintaining VLOS the entire flight as 107.31 requires, you can see exactly which direction the aircraft is drifting, its current attitude, and that it remains well clear of the building edge and any bystanders below. You apply a gentle, continuous correction into the wind to hold position manually, complete the remaining portion of the inspection at a slightly reduced pace, and land normally once finished — all without needing to invoke 107.21's deviation authority, because 107.31 compliance gave you everything needed to keep the aircraft safe without GPS.
14 CFR 107.31's four required visual determinations remain the remote pilot's backstop whether or not GPS is currently available.
View Larger| Capability | GPS-assisted mode | ATTI (manual) mode |
|---|---|---|
| Horizontal position hold | Active, automatic correction for wind drift | None; pilot must manually correct for drift |
| Altitude hold | Barometer-based, generally still functions | Still functions via barometer in most aircraft |
| Automatic return-to-home | Available, using recorded home point | Typically unavailable without a position fix |
| Reliance on remote pilot's visual input | Reduced, but still legally required under 107.31 | Substantially increased; the pilot is the primary means of control |
Responding to a GPS Signal Loss in Flight
A response sequence built on the assumption that 107.31 VLOS has already been maintained throughout the flight.
Recognize the GPS-loss indicator immediately
Most flight controllers display a clear warning (often a mode change to ATTI, or a satellite-count icon change) when GPS is lost or degraded — know what your specific aircraft's indicator looks like before you need it.
Rely on your visual reference, not the aircraft's internal sensors, to assess drift
Use the 107.31 visual connection you have already been maintaining to see exactly how the aircraft is drifting and in what direction.
Apply gentle, continuous manual corrections
Correct for wind drift with smooth, small stick inputs rather than large, abrupt corrections, which are harder to control precisely in ATTI mode.
Reassess whether the mission can safely continue
Decide, based on your visual assessment and manual-control confidence, whether to complete the mission at a reduced pace or land promptly instead.
Land manually if control becomes difficult to maintain confidently
Choose a clear, safe landing area within visual range and land under manual control rather than risk losing positive control entirely.
| Mistake | Why it happens | Correct understanding | Regulation / source |
|---|---|---|---|
| Believing a video feed or telemetry screen satisfies 14 CFR 107.31's visual requirement | The video feed feels like it provides the same information | 107.31 requires unaided visual contact by the remote pilot, person manipulating the controls, or a visual observer — a screen does not substitute for this. | 14 CFR 107.31(a), (b) |
| Attempting an automatic return-to-home immediately after GPS is lost | Return-to-home feels like the safest default response | Return-to-home depends on accurate position data that is exactly what is missing during a GPS loss; manual flight and landing is often more reliable. | N/A (technical limitation) |
| Never having practiced ATTI-mode flying before needing it in a real GPS-loss event | GPS-assisted flight is the default and rarely fails during casual practice | Practicing manual, GPS-free flight in a safe environment builds the skill needed to respond calmly and precisely when GPS is actually lost. | N/A (skill development) |
| Assuming binoculars or FPV goggles alone satisfy the 107.31 visual requirement | Both provide a way of "seeing" the aircraft | 107.31(a) requires vision "unaided by any device other than corrective lenses" — binoculars and FPV goggles do not meet this standard on their own. | 14 CFR 107.31(a) |
Does losing GPS signal violate any Part 107 regulation by itself?
No. GPS loss is a technical event, not a regulatory violation. What matters is whether the remote pilot, already required to maintain VLOS under 14 CFR 107.31, responds appropriately to keep the aircraft safe once GPS assistance is unavailable.
What does "unaided by any device other than corrective lenses" mean under 107.31?
It means eyeglasses or contact lenses are acceptable, but visual-enhancing devices like binoculars or FPV goggles do not satisfy the visual-line-of-sight requirement on their own.
Can a visual observer satisfy 107.31 instead of the remote pilot personally?
Yes. 14 CFR 107.31(b) allows the required visual capability to be exercised by the remote pilot and the person manipulating the controls, or by a dedicated visual observer.
Test Your Knowledge
Answer the questions below to check your understanding. Every answer can be found in the lesson above.