Human Factors

• Hypoxic — insufficient oxygen pressure at altitude; the classic altitude hypoxia
• Hypemic — the blood cannot carry oxygen; carbon monoxide poisoning, anemia, blood loss
• Histotoxic — the cells cannot use the oxygen delivered; alcohol and drugs
• Stagnant — inadequate circulation delivers the oxygen; G-forces, cold, restricted circulation

(PHAK ch. 17.) Symptoms include lightheadedness or dizziness, tingling in fingers and toes, and numbness; as it worsens the field of vision narrows and instrument interpretation becomes difficult — and it can produce a false sense of security, deceiving the pilot into believing everything is normal (PHAK ch. 17). Treatment is lower altitude and/or supplemental oxygen. All pilots are susceptible regardless of physical endurance or fitness.

Over-breathing blows off carbon dioxide, and the symptoms closely mimic hypoxia, which is why correct diagnosis matters (PHAK ch. 17). If supplemental oxygen is in use, check the equipment and flow rate first to establish whether the symptoms are oxygen-related.

In a training airplane the usual cause is anxiety, and the usual student is one who will not say anything. Corrective action: get them talking — talking aloud slows the breathing rate mechanically — level off, and lower the workload. Then debrief it as a normal, correctable thing, so the student reports it next time instead of hiding it.

CO produces hypemic hypoxia — the blood loses its ability to carry oxygen (PHAK ch. 17). In a training airplane the classic source is exhaust leaking into the cabin heat through a cracked heater muff, so it appears in winter, in the airplane the student flies every week.

Corrective actions to teach: heater off, fresh air vents open, oxygen if available, and land. Preventive action to teach: a CO detector in the airplane, and a preflight look at the exhaust system. Teach the student to treat an unexplained headache in the winter as CO until proven otherwise.

Trapped air in the middle ear and sinuses expands on climb and must be equalized on descent. Congestion blocks the eustachian tube and the descent becomes painful or damaging. The instructor decision is the one that matters: a student who reports a cold does not fly, and a student who reports ear pain on descent gets a slower descent rate — or a level-off — immediately.

Related risk in Task II.M and II.N territory: a decongestant may fix the ear and impair the pilot, which is why 91.17(a)(3) prohibits acting as a crewmember while using any drug that affects the person's faculties in any way contrary to safety.

The three orientation systems are vestibular (inner ear), somatosensory (pressure and muscle cues), and visual. Vision is the reliable one; the other two mislead without outside references. The classic illusions all arise when the vestibular system reports a motion the eyes cannot confirm:

• The leans
• Coriolis
• Graveyard spiral
• Somatogravic
• Inversion
• False horizon
• Autokinesis
• Elevator

Instructor rule: when the student reports a sensation that disagrees with the instruments, the instruments win, and you say so out loud while you take the controls if needed. Demonstrate disorientation deliberately under the hood, at altitude, with a briefed recovery — not accidentally in deteriorating weather.

Prevent it: fresh air, an outside visual reference, level flight, and control in the student's hands rather than yours. If it starts: stop the maneuver, get the airplane level and cool, open the vents, and give the student something to look at outside and something to do.

The instructional consequence matters more than the physiology. A student who gets sick and is pushed to continue learns aversion, not flying. End the lesson early, debrief on the ground, and schedule the next flight short. Learning does not happen while a person is nauseated — negative emotion blocks it (AIH ch. 2).

These are the conditions your student will not report, and the ones you are most likely to have. A CFI flying five lessons a day is the fatigue case study.

• Fatigue — degrades attention, judgment, and the willingness to intervene. 61.195(a) caps you at 8 hours of flight training in any 24-consecutive-hour period, but that is a legal ceiling, not a fitness standard.
• Stress — external pressure (a checkride date, a paying customer, a hard month) drives get-there-itis in instructors as readily as in pilots.
• Dehydration and nutrition — a full day of lessons without water or a meal produces exactly the symptoms you are supposed to be monitoring in someone else.
• Hypothermia — cold degrades dexterity and judgment; in an unheated cockpit in winter it arrives before anyone names it.

Diving forces additional nitrogen into body tissues and fluids; the reduced pressure of flight lets it come out of solution as bubbles (PHAK ch. 17):

• At least 12 hours before flying to altitudes up to 8,000 ft after a dive that does not require controlled ascent (nondecompression stop diving)
• At least 24 hours after a dive that does require controlled ascent (decompression stop diving)
• At least 24 hours after any dive before flying above 8,000 ft

These are actual flight altitudes MSL, not pressurized cabin altitudes, because the numbers take into account the risk of an in-flight decompression (PHAK ch. 17).

Under 91.17(a) no person may act or attempt to act as a crewmember:

• Within 8 hours after consuming any alcoholic beverage
• While under the influence of alcohol
• While using any drug that affects the person's faculties in any way contrary to safety
• With an alcohol concentration of 0.04 or greater in a blood or breath specimen

91.17(b) also prohibits carrying a person who appears intoxicated or shows indications of drug influence, except in an emergency or a medical patient under proper care. 61.15 governs the certificate consequences of drug and alcohol convictions and the reporting obligation.

For over-the-counter medication, PHAK ch. 17 recommends waiting at least five maximal dosing intervals before flying after any medication with potentially adverse side effects — a drug dosed every 5 to 6 hours means a 30-hour wait — and notes that observing the interval does not eliminate the risk.

• Anti-authority ("Don't tell me") → Follow the rules; they are usually right
• Impulsivity ("Do something quickly") → Not so fast; think first
• Invulnerability ("It won't happen to me") → It could happen to me
• Macho ("I can do it") → Taking chances is foolish
• Resignation ("What's the use?") → I'm not helpless; I can make a difference

The instructor's job is not to have the student recite these — it is to name the attitude in the moment it appears, in the debrief, using the student's own decision as the example. That is a critique, not an evaluation (AIH ch. 6).

Single-Pilot Resource Management is the management of all resources — onboard (instruments, avionics, autopilot, checklists) and outside (ATC, flight service, flight following) — to reduce workload and maintain safety. CRM applies where there is a crew.

The wrinkle for instructors: there are two people in a training airplane, but the student is not a crew — the student is a workload source. FI.I.F.S3d makes awareness of who is manipulating the controls, through the positive exchange of flight controls, a skill element in its own right. Brief the exchange procedure on the ground and use it every time (AIH ch. 9).

Assigned minimums are the instructor's minimums, and they evaporate the day the student flies alone. Build them with the student instead:

1. Start from the regulatory floor — 91.155 visibility and cloud clearance, 91.151 fuel reserve.
2. Add the student's demonstrated performance — the crosswind they have actually handled, the ceiling at which they have actually flown a cross-country.
3. Write the numbers down, with the student holding the pen.
4. Add a rule for changing them: minimums go up when conditions or currency degrade, and they only go down after training, in daylight, with an instructor.

Then use them. Every solo endorsement you write should reference limitations, and those limitations should be the student's own numbers whenever they are more conservative than yours (61.195(d)(1)). That is how a personal minimum survives the checkride.

Treat the go/no-go as the lesson. Run IMSAFE out loud together rather than asking "are you good to fly?" — a yes/no question with a socially obvious answer teaches nothing. If the answer is no, the correct instructor behavior is to convert the flight into a ground lesson and say plainly why, because the demonstration of a canceled flight is worth more than the flight would have been.

The AIH framing: instructors are role models whose behavior is copied whether or not it is taught (AIH ch. 8). A CFI who flies fatigued produces pilots who fly fatigued.

By planning realistic distractions rather than improvising them. FI.I.B.S3 makes this an explicit instructor skill: plan for and use techniques, including realistic distractions, that teach flight students how to manage workload.

Techniques that work:

• Ask for a radio frequency change during a maneuver the student has already mastered — never during first exposure
• Drop a chart, ask a navigation question, or simulate a passenger request in the pattern
• Require the student to verbalize aviate–navigate–communicate priority out loud when saturated

Techniques that do not work: surprising a student during initial learning of a difficult skill. That produces stress and negative learning, not resilience.

Expectation bias — hearing the clearance you expected rather than the one issued. It is the reason 91.123-style readbacks and written taxi instructions matter, and it is named directly as a runway incursion risk in Task II.C.

Confirmation bias — seeking information that supports the decision you already made, most dangerously in weather go/no-go: reading the one favorable TAF and stopping.

The instructor countermeasure is procedural, not motivational. Require the student to state the decision and the evidence that would reverse it, before the flight. "We go, unless the ceiling at the destination drops below 3,000 or the crosswind exceeds 10 knots" is a decision that can be checked. "It looks fine" is not.

You point them to the regulation and to a qualified source, and you do not offer a medical opinion. 61.23 governs medical certificate requirements and duration, 61.53 prohibits acting as pilot in command while having a known medical deficiency, and the AME or an aviation medical specialist is the correct address for the question.

What you do own: telling the student clearly that concealing a condition is both a certificate action risk and a flight safety risk, and that the FAA's process has more paths to a certificate than most students assume. Then stay in your lane. Confidently guessing on aeromedical questions is one of the fastest ways for an instructor to lose credibility — and to give genuinely harmful advice (AIH ch. 8).

They compound. Vision is the first thing degraded by reduced oxygen, and rods — the receptors you depend on at night — take approximately 30 minutes to fully dark-adapt while a single bright light can destroy that adaptation (PHAK ch. 17). At night, fatigue is higher, the horizon may be absent, and vestibular illusions have nothing to contradict them.

That is why night cross-country training is where you most need the self-assessment discipline you have been modeling all along, and why many pilots use supplemental oxygen at night well below the 91.211 thresholds. Detail lives in Tasks II.M and II.N.