FAA Private Pilot Helicopter (PRH) flashcards

Controlled airspace around airports with a radar approach control and operating tower, depicted by solid magenta circles.

• Inner core: surface to 4,000 ft AGL, 5 NM radius
• Outer shelf: 1,200 to 4,000 ft AGL, 10 NM radius
• Two-way radio communication must be established before entry

Memory trick: Class C looks like a wedding cake — a small tight core topped by a wider shelf.

Raising collective pitch increases blade angle of attack and induced drag, which decreases rotor RPM unless engine power (throttle) is simultaneously increased.

• Pitch angle changes directly affect drag on rotor blades
• Without throttle correlation, RPM decays when collective is raised
• Governors/correlators automatically compensate for this in modern helicopters
• Manual throttle control requires pilot to coordinate collective and throttle

Memory trick: More pitch, more drag, less RPM—unless you feed more fuel.

A condition where a pilot focuses so intently on one task that attention to other critical instruments, traffic, or flight parameters is neglected.

• Also called tunnel vision or channelized attention
• Common during troubleshooting, radio tuning, or checklist tasks
• Countered by disciplined scanning and prioritizing 'aviate, navigate, communicate'

Memory trick: Tunnel vision on one bulb while the whole dashboard goes dark.

The tendency of the fuselage to rotate opposite the main rotor's direction of turn, caused by the equal and opposite reaction to engine torque driving the rotor.

• Increased power increases torque reaction
• Tail rotor thrust counteracts this reaction
• Pedal inputs must change whenever power/torque changes
• Distinct from translating tendency, which is a lateral drift caused by tail rotor thrust itself

Memory trick: More power up, more left pedal to keep the nose true.

Airport symbols are printed in blue for airports with an operating control tower and in magenta for airports without a control tower.

• Blue = airport has an operating control tower
• Magenta = no control tower, or tower not in continuous operation
• Symbol shape indicates hard-surfaced vs. other runway types

Memory trick: Blue like the sky where the tower controller watches; magenta means 'mind yourself,' no tower.

METAR weather phenomena are prefixed with intensity qualifiers: '−' for light, no symbol for moderate, and '+' for heavy.

• '+' prefix = heavy intensity; '-' prefix = light intensity; no symbol = moderate
• TS = thunderstorm, RA = rain, common combined as TSRA
• VC prefix means 'in the vicinity' (5-10 miles from the station)
• Recency indicators like RE (recent) can also appear, e.g., 'RETS'

Memory trick: '+' means Plenty (heavy), '-' means Little (light), blank means moderate

When a helicopter loses all tail rotor thrust in cruise flight, forward airspeed and the vertical fin provide partial anti-torque effect; the pilot should maintain airspeed, gradually reduce power, and execute a controlled running landing.

• Different emergency techniques apply depending on flight regime (hover vs. cruise)
• At cruise speed, the vertical fin and airspeed help counteract torque-induced yaw
• Abrupt power changes can worsen uncontrolled yaw
• Goal is a controlled running/roll-on landing rather than abrupt autorotation entry

Memory trick: Keep your speed, ease the power, let the fin fly you home.

An airfoil shape with identical upper and lower surface curvature, chosen for main rotor blades because its center of pressure stays nearly fixed across changing angles of attack.

• Upper and lower surfaces are mirror images
• Center of pressure travel is minimal with AOA changes
• Reduces blade twisting (torsional) loads
• Cambered airfoils shift CP more and produce more lift but more twisting moment

Memory trick: Symmetrical = balanced twin, CP doesn't wander, blade doesn't twist.

During autorotation, rotor RPM is controlled by collective pitch; lowering collective decreases blade drag and increases RPM, while raising collective increases drag and decreases RPM.

• Low rotor RPM in autorotation is corrected by lowering collective
• Raising collective in this situation worsens RPM decay
• Rotor RPM must stay within the green arc for a safe autorotation and flare

Memory trick: Low RPM? Lower the collective — less drag lets the rotor spin free.

A violent, self-reinforcing vibration on fully articulated rotor helicopters caused by uneven blade spacing (from lead-lag hinges) coinciding with the natural frequency of the landing gear on the ground.

• Requires a fully articulated (lead-lag) rotor system
• Triggered by a hard landing, taxiing on rough ground, or one-wheel/skid touchdown
• Can rapidly destroy the helicopter if not corrected by immediate takeoff or shutdown

Memory trick: Ground resonance = 'bunched blades bounce the whole bird apart.'

The maximum operating weight for a given flight is the lesser of the structural maximum gross weight and any performance-limited weight (such as for hover, takeoff, or climb) under existing conditions.

• Structural limit is fixed by the manufacturer
• Performance limits vary with density altitude, wind, and temperature
• The more restrictive limit always governs the flight

Memory trick: The lowest fence wins — always obey the tighter limit.

The approximate height of cumuliform cloud bases can be estimated by dividing the temperature/dew point spread (°C) by 2.5 and multiplying by 1,000 feet.

• Formula: (Temp − Dew Point) ÷ 2.5 × 1,000 = cloud base AGL
• Based on typical adiabatic cooling and moisture lapse rates
• Useful for estimating convective cloud bases, not stratiform layers

Memory trick: Spread divided by 2.5, times a thousand, tells you where clouds are dumped

A one-way clutch in the transmission that automatically disengages the engine from the rotor system whenever engine RPM is lower than rotor RPM, essential for autorotation.

• Also called a sprag clutch or overrunning clutch
• Engages automatically—no pilot action required
• Allows rotor to continue turning via aerodynamic forces after engine failure

Memory trick: Freewheeling = 'free' the rotor from a dead engine automatically.

Requires pilots to become familiar with all available information concerning a flight, including weather, fuel requirements, alternatives, runway data, and NOTAMs before departure.

• Applies to every flight
• Includes weather reports and forecasts
• Includes fuel requirements and alternate plans
• Includes runway lengths at airports of intended use for flights under certain parts

Memory trick: WAFR: Weather, Alternates, Fuel, Runways — check before you fly.

Under 61.109(f), the helicopter private pilot solo cross-country requires 50 nm total distance, landings at three points, with one segment of at least 15 nm straight-line distance.

• 50 nm total distance minimum
• Landings at 3 points minimum
• One leg at least 15 nm straight-line

Memory trick: Fifty miles, three stops, fifteen straight — that's the helicopter's cross-country fate

Under 91.207(c), ELT batteries must be replaced after 1 cumulative hour of use or 50% of useful life expiration, whichever comes first.

• 1 cumulative hour of use triggers replacement
• 50% of useful life is the alternate trigger
• Whichever condition occurs first governs

Memory trick: One hour of talking or half a life gone — swap the battery before it's blown

14 CFR 61.31 requires pilots to hold the category and class rating appropriate to the aircraft they operate as PIC.

• Categories include airplane, rotorcraft, glider, etc.
• Class within rotorcraft includes helicopter and gyroplane
• Adding a rating requires meeting 61.109 experience and passing a practical test

Memory trick: Certificates are like keys — one key (airplane) doesn't open a different lock (helicopter).

As density altitude increases, both engine power output and rotor lift efficiency decrease, reducing the maximum gross weight for hovering, especially OGE.

• Higher density altitude decreases available engine power
• Higher density altitude requires more blade pitch (power) for the same lift
• OGE hover performance is more sensitive to density altitude than IGE

Memory trick: Thin air means thin margins — less weight allowed as DA climbs.

A steady headwind during hover reduces power required by providing translational-lift-like airflow over the rotor disk, improving rotor efficiency.

• Headwind reduces power required to hover
• Effect is similar to effective translational lift
• Tailwinds and gusty/turbulent winds can degrade hover performance and control

Memory trick: A friendly headwind does some of the rotor's work for free.

A straight imaginary line connecting the leading edge and trailing edge of an airfoil, used as the reference for measuring pitch angle and angle of attack.

• Straight line, unlike the curved camber line
• Basis for measuring blade pitch angle
• Basis for measuring angle of attack relative to relative wind

Memory trick: Chord is a straight cord tied leading-edge to trailing-edge

14 CFR 91.159 requires VFR aircraft above 3,000 feet AGL to fly at hemispheric cruising altitudes based on magnetic course, but helicopters are specifically excluded from this requirement.

• Applies to fixed-wing aircraft above 3,000 ft AGL
• Odd course (0-179°) = odd thousands +500 ft
• Even course (180-359°) = even thousands +500 ft
• Helicopters are exempt from this entire rule

Memory trick: Odd east, even west — but helicopters get a pass on the rest.

Tail rotor thrust output for a given pitch angle decreases as air density decreases (higher density altitude), requiring greater pedal input to maintain anti-torque control.

• Tail rotor performance follows the same aerodynamic principles as the main rotor
• High density altitude reduces available tail rotor thrust
• Pilots may run out of pedal authority (left pedal limit) at high density altitude hovers
• Critical consideration for high-altitude/hot-day hover operations

Memory trick: Thin air, thin thrust—tail rotor needs more pedal to fight torque.

Groundspeed is calculated as distance flown divided by time elapsed; it is then used to compute time required for remaining distance.

• Groundspeed (kt) = distance (NM) ÷ time (hr)
• Time (hr) = distance (NM) ÷ groundspeed (kt)
• Convert minutes to hours by dividing by 60 before calculating

Memory trick: Distance ÷ Time = Speed; flip it to find Time again.

The center of gravity position determines how much cyclic control margin remains available; extreme forward or aft loading can exhaust control authority.

• Forward CG requires aft cyclic to hover
• Aft CG requires forward cyclic to hover
• Exceeding CG limits can result in loss of control authority in flight regimes like hover or autorotation

Memory trick: Nose falls forward, cyclic pulls back.

Fog that forms over land on clear, calm nights when the ground radiates heat rapidly, cooling the air near the surface to its dew point.

• Requires clear skies for maximum radiational cooling
• Requires light or calm winds to prevent mixing
• Common in low-lying areas and valleys with moist air
• Usually dissipates after sunrise as the ground warms

Memory trick: Radiation fog = 'Rests on the ground on a Clear, Calm night'

A condition where the main rotor descends into its own downwash during a low-airspeed, high-rate vertical descent, causing loss of lift despite power application.

• Requires: power applied, low airspeed, high rate of descent
• Recovery: lower collective and apply forward cyclic to gain airspeed
• Adding more power alone worsens the condition

Memory trick: Sinking into your own storm — the rotor eats its own downwash.

Degraded alertness and performance caused by flying during the body's natural low point in its 24-hour internal clock, typically between 0300 and 0500.

• Circadian low point is roughly 0300-0500 for most people
• Reduced sleep amplifies circadian-related performance decline
• Irregular schedules and time zone changes worsen the effect

Memory trick: The body's clock hits its low point in the dead of night.

Density altitude is pressure altitude corrected for nonstandard temperature; it increases when temperature is above standard for that altitude.

• Standard temperature decreases 2°C per 1,000 feet from 15°C at sea level
• Density altitude changes about 120 ft per °C deviation from standard
• High density altitude reduces aircraft/helicopter performance
• Formula: DA = PA + (120 × (OAT − Standard Temp))

Memory trick: Find standard temp, find the difference, multiply by 120

Required periodic check under 14 CFR 91.171 to ensure a VOR receiver's accuracy before flight under IFR; tolerances vary by check method.

• VOT check: ±4 degrees
• Ground checkpoint: ±4 degrees
• Airborne checkpoint: ±6 degrees
• Must be logged with date, place, bearing error, and signature

Memory trick: VOT and ground both say '4,' airborne gives you a little more slack at '6.'

An 'accident' involves death, serious injury, or substantial aircraft damage during the operation of an aircraft; an 'incident' is any other occurrence associated with operation that affects safety without meeting those thresholds.

• Serious injury includes hospitalization >48 hrs within 7 days, among other criteria
• Substantial damage excludes engine failure alone, bent fairings, and flat tires/tubes
• Definition applies from boarding with intent for flight until disembarkation

Memory trick: 'Serious hurts or serious dents' define an accident — anything less is just an incident.

A spatial disorientation illusion in which an abrupt return to level flight after a prolonged, gradual, undetected turn causes a false sensation of banking in the opposite direction.

• Most common vestibular illusion experienced by pilots
• Caused by the inner ear's inability to detect very slow angular accelerations
• Correct response is to trust flight instruments over bodily sensations

Memory trick: 'Lean on the level' — trust the gauges when your body says lean.

Airspace established to separate military training activities from IFR traffic; VFR flight is permitted but caution is advised.

• Depicted with magenta hashed border and area name
• VFR flights may transit without clearance
• Pilots should check with Flight Service or controlling agency for activity times

Memory trick: MOA = 'Military Operations Allowed for VFR, but watch out!'

Colorless, odorless gas that can leak into the cabin through cracked exhaust heat exchangers, binding to hemoglobin and causing hypoxia-like symptoms.

• Symptoms: headache, drowsiness, dizziness, impaired judgment
• CO has 200+ times greater affinity for hemoglobin than oxygen
• Response: heater off, fresh air, oxygen if available, land ASAP

Memory trick: 'Silent gas, cracked heater' — smell nothing, feel everything.

As fuel is consumed during flight, gross weight decreases, which improves hover, climb, and overall performance capability.

• Fuel burned (lb) = fuel flow rate × time
• Lower gross weight improves hover ceiling and climb rate
• Performance planning should account for weight changes over a long flight

Memory trick: Burn fuel, lose weight, gain performance.

A property of rotating bodies where an applied force is manifested 90° later in the direction of rotation.

• Effect occurs 90° in the direction of rotation from the applied force
• Explains rotor disc tilt response to cyclic and mast movement
• Critical to understanding two-bladed semi-rigid rotor dynamics

Memory trick: Push now, feel it 90° later — precession plays a delay game.

When wind blows perpendicular to the intended course, it requires a wind correction angle calculated using the sine relationship between wind speed and true airspeed.

• WCA (degrees) ≈ arcsin(crosswind component / TAS)
• Groundspeed = sqrt(TAS² − crosswind component²) for a pure crosswind
• Correct into the wind (turn toward the direction the wind is coming from)

Memory trick: Turn your nose toward the wind's source, like leaning into a push.

14 CFR 61.57(a)(1) requires a pilot to have made 3 takeoffs and landings within the preceding 90 days in the same category and class of aircraft to carry passengers.

• Day currency: 3 takeoffs/landings in 90 days
• Night currency requires full-stop landings, 1 hour after sunset to 1 hour before sunrise
• Category, class, and type (if required) must match the aircraft flown

Memory trick: '90 days, 3 landings' keeps you legal to carry friends by day.

Helicopter performance charts are based on steady wind test data; gusty or variable winds require pilots to add a safety margin because performance can be less predictable.

• Charts assume smooth, steady reported wind speed
• Gusts can cause sudden loss of translational lift or effective airspeed
• Pilots should build in extra performance margin in gusty conditions

Memory trick: Steady wind on paper, gusty wind in reality—always keep a buffer

A pilot may log PIC time when sole manipulator of the controls of an aircraft for which they are rated, even if another qualified pilot is also acting as PIC.

• Requires appropriate category/class rating
• Applies regardless of who holds operational PIC responsibility
• CFI giving instruction may also log PIC simultaneously
• Different from acting as PIC, which involves legal responsibility for the flight

Memory trick: Hands on the controls, rating in your pocket — log it as PIC.

14 CFR 91.151 mandates specific fuel reserves (30 min day / 45 min night) for airplanes only; helicopters are not covered by this rule but must still plan adequate fuel under 91.103.

• 91.151 applies only to airplanes, not helicopters
• Airplane day reserve is 30 minutes, night reserve is 45 minutes
• 91.103 requires all pilots to ensure adequate fuel through preflight planning

Memory trick: 91.151 talks only to airplanes; helicopters listen to 91.103 instead

FD forecasts encode wind direction (tens of degrees true), speed (knots), and temperature (°C) in six-digit groups, with special codes for light/variable conditions and high altitudes.

• '9900' = light and variable wind, less than 5 knots
• Temperature omitted within 2,500 ft of station elevation
• Above 24,000 ft, add 50 to direction code and 100 to speed to distinguish high-speed winds

Memory trick: '99 means 99 problems but wind ain't one—light and variable'

A hazardous attitude in which a pilot takes unnecessary risks to prove superior ability, often to impress others.

• Antidote: 'Taking chances is foolish'
• Common trigger: showing off for passengers
• Can affect any pilot regardless of gender

Memory trick: A Menacing Idiot Recklessly Ignores rules.

An airman must notify the FAA of a permanent mailing address change within 30 days or lose the privilege to exercise certificate privileges until reported.

• Notification is written, sent to the Airman Certification Branch
• 30-day window applies
• Non-compliance suspends exercise of privileges after 30 days

Memory trick: '30 days or grounded' – notify or lose privileges.

An illusion causing a sensation of tumbling or turning on a different axis when a pilot moves his head during a sustained turn, disturbing fluid in multiple semicircular canals.

• Triggered by head movement during a prolonged turn
• Considered one of the most disorienting illusions
• Avoid quick head movements during instrument flight, especially in turns

Memory trick: Tilt your head mid-spin and the world tumbles sideways.

Effective translational lift occurs at a fairly consistent indicated airspeed, but in thinner air (higher density altitude) a greater true airspeed is required to reach that same indicated airspeed.

• ETL typically begins around 16-24 knots IAS
• IAS reflects dynamic pressure, which depends on air density
• Higher density altitude requires more TAS to produce the same IAS and airflow effect

Memory trick: Thin air makes you 'work harder and faster' (more TAS) to feel the same lift boost

A tail rotor replacement system that uses a fan-driven airflow exiting tailboom slots (via the Coandă effect) plus a direct jet thruster to provide anti-torque and yaw control.

• Variable-pitch fan blows air into the hollow tailboom
• Slots release air that follows the boom surface via Coandă effect
• A direct jet thruster at the tail provides additional directional control
• Eliminates exposed tail rotor blades, reducing certain hazards

Memory trick: No blades, just a boom that 'hugs' the air (Coandă) to push sideways.

Thunderstorms progress through cumulus, mature, and dissipating stages, each with distinct updraft/downdraft and precipitation characteristics.

• Cumulus stage: continuous updraft, cloud building, no precipitation yet
• Mature stage: updrafts and downdrafts coexist, heavy rain begins, most hazardous stage
• Dissipating stage: downdrafts dominate, precipitation decreases
• Onset of surface rain marks the beginning of the mature stage

Memory trick: Cumulus builds, Mature bursts, Dissipating rests

Hover ceiling performance charts vary with both pressure altitude and temperature; pilots must select the value matching actual conditions to determine maximum safe gross weight.

• Higher temperature reduces max hover gross weight at a given altitude
• Always use the temperature/altitude combination matching actual conditions
• Exceeding the chart's weight limit means the hover is not achievable

Memory trick: Match your real temperature to the chart—don't borrow a cooler day's numbers

The unequal lift generated between the advancing and retreating halves of the rotor disc during forward flight, caused by differing relative wind speeds.

• Advancing blade speed = rotational speed + aircraft speed
• Retreating blade speed = rotational speed − aircraft speed
• Compensated primarily by blade flapping (flap-up on advancing side)

Memory trick: Advancing blade adds speed, retreating blade subtracts — flapping fixes the fight.

Uncontrolled airspace that extends from the surface up to the base of overlying controlled (Class E) airspace; in areas without Class E, it can extend up to 14,500 feet MSL.

• Typical Class E floors are 700 ft or 1,200 ft AGL near airports
• In remote western U.S. areas lacking Class E, Class G extends to 14,500 ft MSL
• Above 14,500 MSL, Class E airspace generally begins nationwide (except in specific excluded areas)

Memory trick: No magenta on the map? Class G climbs sky-high to 14,500!

During autorotation the rotor blade is divided into three regions—stall, driving, and driven—based on angle of attack and the resulting aerodynamic force direction.

• Stall region: innermost, high AOA, blade stalled
• Driving region: middle, produces forward (accelerating) force
• Driven region: outer, produces rearward (decelerating) force
• Balance of these regions maintains autorotative RPM

Memory trick: Root stalls, Middle drives, Tip drags — the 'driving' middle keeps you spinning.

Common Traffic Advisory Frequency used at uncontrolled airports for pilots to self-announce position and intentions to enhance situational awareness.

• Self-announce starting about 10 NM from airport
• Continue broadcasts through pattern, landing, and taxi
• CTAF may be a UNICOM, MULTICOM, or FSS frequency

Memory trick: CTAF = 'Call The Airport First' at 10 miles out.

After an accident, the operator must preserve aircraft wreckage and records until the NTSB takes custody, except as needed to protect people or prevent further damage.

• Applies to wreckage, mail, cargo, and records
• Exceptions: removing injured/trapped persons, protecting from further damage, protecting the public
• Violation can result in enforcement action

Memory trick: 'Freeze the scene' until NTSB says go.

High humidity displaces heavier oxygen and nitrogen molecules with lighter water vapor, decreasing air density and degrading engine and rotor performance.

• Water vapor is lighter than dry air molecules
• High humidity effectively increases density altitude conditions
• Not included in the standard DA computation but should be considered by pilots

Memory trick: Humid air is 'thin' air in disguise—less punch for engine and rotor

Excess power is the power available beyond what is needed for level flight; it is used to produce a climb, and more excess power yields a greater rate of climb.

• Excess power = power available − power required
• Best rate-of-climb speed occurs where excess power is greatest
• Excess power decreases as altitude/weight/temperature increase

Memory trick: Leftover power lifts you higher.

A technique using short, regularly spaced eye movements across 10-degree segments to detect traffic, since the human eye cannot focus effectively while moving continuously.

• Each segment scanned for about 1 second
• Peripheral vision detects motion but needs central vision to identify objects
• Continuous sweeping motion reduces detection effectiveness

Memory trick: 'Stop, look, ten degrees, repeat' — like flipping through photo frames.

A chart showing combinations of altitude and airspeed to avoid because a safe autorotative landing may not be achievable if the engine fails.

• Also called the 'deadman's curve'
• Low altitude/low airspeed and low altitude/high airspeed combinations are most critical
• Varies by gross weight, density altitude, and helicopter model

Memory trick: Stay out of the shaded zone or you can't autorotate in time.

A vestibular illusion where rapid acceleration is perceived as a pitch-up attitude, prompting the pilot to push the nose down inappropriately.

• Occurs during rapid acceleration such as takeoff
• Most dangerous at night or in IMC with no visual horizon
• Can lead to controlled flight into terrain if pilot trusts sensation over instruments

Memory trick: 'Speed feels like a climb' — trust the gauges, not your gut.

An ELT battery must be replaced/recharged after 1 cumulative hour of use or 50% of useful life, whichever comes first.

• Applies to both used and standby battery life
• Replacement date must be marked on the ELT or its container
• ELTs transmit on 121.5 and 406 MHz depending on type

Memory trick: 1 hour used or half the life — replace that battery, avoid the strife.

Turning downwind at low altitude and low airspeed reduces airspeed through the rotor system, risking loss of effective translational lift and an unexpected settling toward the ground.

• Most critical near the ground and at low airspeed
• Groundspeed increases but airspeed through rotor decreases
• Pilot must add power/anticipate sink during the turn

Memory trick: Turn downwind, lose your wind — watch the sink!