Of the nine subjects on the A1/A3 syllabus, this is the one most people skim. It has nothing to do with airspace, class marks or the 120-metre ceiling, and it does not feel like it is about the drone at all. It is about you. And it is the only subject that describes a legal duty you carry during every single flight, not just a fact to recite on exam day.
The subject is human performance limitations, and it comes down to a plain question you are legally required to answer before you launch: are you fit to fly right now?
The rule, word for word
The duty lives in Regulation (EU) 2019/947, Annex Part A, point UAS.OPEN.060 — the responsibilities of the remote pilot. Point (2)(a) says that during the flight the remote pilot shall:
not perform duties under the influence of psychoactive substances or alcohol or when it is unfit to perform its tasks due to injury, fatigue, medication, sickness or other causes.
Read what the regulation does not do here. It gives you no number. There is no blood-alcohol limit written into the open category, no "eight hours from bottle to throttle" figure like crewed aviation uses, no list of banned medicines. It draws the line qualitatively: if a substance or a condition makes you unfit to perform the task, you do not fly. Full stop.
That is deliberate, and it puts the decision on you. The A1/A3 question bank is blunt about where responsibility sits: it rests solely with the remote pilot and the UAS operator. There is no medical examiner signing you off before a park flight. You are the check.
It is one of the nine exam subjects for a reason
Human performance limitations is not an add-on. It is named directly in the regulation as one of the online-theory subjects for the A1/A3 open category, alongside air safety, airspace restrictions, aviation regulation, operational procedures, general knowledge of UAS, privacy and data protection, insurance, and security.
It earns that place because a drone accident rarely starts with the aircraft. The battery is fine, the firmware is current, the zone is clear — and the flight still goes wrong because the person holding the controller was tired, distracted, rushing, or had one drink too many "just to relax before flying". The regulation regulates the machine everywhere else. This subject regulates the pilot.
IMSAFE: turning "fit to fly" into a real check
"Am I fit to fly?" is easy to wave away. Aviation solved that long ago with a six-letter self-assessment, IMSAFE, and it maps cleanly onto the open category's fitness duty. Run it in your head before you power up:
- I — Illness. A cold, a fever, dizziness, anything that dulls your reactions. If you would not want to drive, do not fly.
- M — Medication. Prescription or over-the-counter. Antihistamines, cold remedies and painkillers can cause drowsiness that you will not notice until your scan slows down.
- S — Stress. A bad day, a work deadline, an argument. Stress narrows attention — exactly the thing a pilot maintaining visual line of sight cannot afford to lose.
- A — Alcohol. The regulation's explicit trigger. Not just "am I drunk" but "is there any alcohol still in my system". If in doubt, the flight waits.
- F — Fatigue. The quiet one. Tiredness degrades judgement and reaction time before you feel obviously sleepy, which is why the regulation names it by hand.
- E — Eating. Low blood sugar and dehydration blunt concentration on a long session in the sun. Not a headline risk, but real on a hot afternoon in the field.
IMSAFE is an aviation self-check, not a paragraph of drone law — but it is the practical tool behind the regulation's word "unfit", and it is exactly what the human-performance section of the training is teaching you to internalise.
The perception traps that are specific to flying a drone
The fitness duty is one half of the subject. The other half is about the limits of your eyes and attention while you fly — and this half connects straight to the visual-line-of-sight rule, because your VLOS duty is only as good as your ability to actually see.
A few limits catch drone pilots in particular:
- Empty-field myopia. Stare at a featureless bright sky with nothing to focus on and your eyes relax to a near focus of a metre or two — so a small drone against that blank sky can slip out of sharp vision even while you are "looking right at it". The fix is to deliberately refocus on a distant object every so often.
- Night-vision loss. Your eyes take a long time to adapt to darkness and lose that adaptation in a single glance at a bright phone or controller screen. This is a real constraint the moment you fly at dusk or in the dark.
- Single-task fixation. Locking onto the live video feed or the map and forgetting to look up. In FPV especially, the goggles give you tunnel vision by design — which is precisely why the rules require the drone to stay in a spotter's or your own unaided sight.
None of these are moral failings. They are how human eyes and attention actually work, and the exam expects you to know them because knowing them is what makes you scan the sky instead of the screen.
This is not just an exam box to tick
It is tempting to treat this subject as the soft one. It is not. If a tired or impaired flight goes wrong, the responsibility — and any penalty — lands on the remote pilot, exactly as the question bank states. "I was fine" is not a defence when the regulation asked you to make an honest fitness call and you skipped it.
The good news is that this is the cheapest safety margin you own. It costs nothing and takes ten seconds: before you unfold the drone, run IMSAFE, and if any letter is a clear yes, the flight waits for another day.
Quick reference before you launch
- The duty is legal, not optional. UAS.OPEN.060(2)(a) forbids flying under psychoactive substances or alcohol, or when unfit due to injury, fatigue, medication, sickness or other causes.
- There is no number. No BAC limit, no bottle-to-throttle hours in the open category — it is a qualitative "fit to fly" call, and it is yours to make.
- Run IMSAFE: Illness, Medication, Stress, Alcohol, Fatigue, Eating.
- Mind your eyes: refocus on something distant to beat empty-field myopia, protect your night vision, and do not let the screen pull your gaze off the sky.
- Responsibility is yours. It rests solely with the remote pilot and the operator — there is no one else to catch the mistake.
FAQ
Can I fly a drone after drinking alcohol? No — not while alcohol is in your system. Regulation (EU) 2019/947, UAS.OPEN.060(2)(a), forbids operating under the influence of alcohol. The open category sets no specific blood-alcohol figure, so the safe reading is zero for flying: if you have been drinking, the flight waits.
Is there a legal blood-alcohol limit or "bottle to throttle" time for open-category drones? No numeric limit or fixed waiting period is written into the open-category rules. The regulation states a qualitative duty — do not fly impaired or unfit — and leaves the honest judgement to you as the remote pilot.
Does prescription or over-the-counter medication count? It can. UAS.OPEN.060 names medication explicitly among the causes that can make you unfit. Anything that causes drowsiness or slows your reactions — including common antihistamines and cold remedies — falls under the duty. When unsure, check the label and err toward not flying.
Is "human performance limitations" really on the A1/A3 exam? Yes. It is one of the nine subjects named in the regulation for the A1/A3 online theory test, so expect questions on the fitness duty, the IMSAFE factors, and perception limits like empty-field myopia and night-vision adaptation.
What is empty-field myopia? It is the tendency of your eyes to relax to a short focus distance when there is nothing to focus on — like a plain bright sky. It can make a small drone hard to keep in sharp view even when you are looking straight at it, which is why pilots deliberately refocus on distant objects during a flight.
Human performance is the subject that reminds you the safest drone still has a human in the loop. Once the fitness duty and the perception limits are clear, line them up with the open category A1, A2 and A3, the visual-line-of-sight rule it underpins, and what the A1/A3 exam in Latvia expects — then drill the human-factors questions in the practice sets.
