FAA Private Pilot Helicopter (PRH) flashcards

Because air density decreases with altitude, a constant indicated airspeed corresponds to an increasingly higher true airspeed as altitude increases.

• IAS measures dynamic pressure, not true speed
• TAS = IAS plus a correction for air density
• At high altitude, TAS can be significantly greater than IAS

Memory trick: Thinner air, same gauge reading, but you're really going faster (TAS grows)

A mechanical linkage (correlator) or automatic sensing system (governor) that adjusts engine throttle as collective pitch is changed, to maintain a relatively constant main rotor RPM.

• Correlator is a mechanical linkage requiring some pilot throttle correction
• Governor senses RPM electronically/hydromechanically and adjusts automatically with little pilot input
• Both reduce pilot workload but differ in precision and response

Memory trick: Correlator/governor: the 'autopilot' for keeping rotor RPM steady as collective moves.

14 CFR 91.159 exempts helicopters from the VFR hemispheric cruising altitude rule that applies to fixed-wing aircraft.

• Airplanes must fly odd+500/even+500 based on magnetic course
• Helicopters may fly at any altitude regardless of course
• Rule applies more than 3,000 feet AGL in level cruising flight

Memory trick: Helicopters Hover above the hemispheric rule.

The maximum density altitude at which a helicopter can hover, which is higher in ground effect (HIGE) than out of ground effect (HOGE) because ground effect reduces induced drag and power required.

• Ground effect reduces rotor downwash angle and induced drag
• Lower power required means better performance at altitude/weight in IGE hover
• HOGE requires more power margin since ground effect benefit is lost
• Performance charts list both HIGE and HOGE ceilings for a given weight

Memory trick: Ground effect is a cushion that lets you hover higher with the same power.

The ratio of total blade area to the total rotor disk area, calculated as (number of blades × blade chord) divided by (π × rotor radius).

• Higher solidity means more blade area relative to disk area
• Two-bladed rotors typically have low solidity (~0.04-0.06)
• Affects rotor efficiency and power required characteristics

Memory trick: Solidity = how 'solid' (blade-filled) the disk really is

Abnormally rapid and deep breathing that eliminates too much carbon dioxide from the blood, causing dizziness, tingling, and muscle spasms.

• Often triggered by stress, anxiety, or fear
• Symptoms mimic hypoxia, making differentiation important
• Corrected by slowing breathing rate, talking aloud, or breathing into a bag

Memory trick: 'Too much air out' causes tingling fingers — slow down and talk it out.

A tendency for a helicopter to roll over when one skid or wheel is on the ground and acts as a pivot point, if bank angle exceeds a critical angle.

• Occurs during takeoff/landing when a skid/wheel is a fixed pivot
• Beyond critical angle, cyclic cannot stop the roll
• Prevented by smooth, coordinated liftoffs and avoiding sideward loads on skids

Memory trick: Past the point of no return, cyclic can't turn the tide.

A weather advisory for hazardous convective weather, including severe thunderstorms, embedded thunderstorms, lines of thunderstorms, hail 3/4 inch or larger, and tornadoes.

• Issued for significant convective activity affecting safety of flight
• Valid for up to 2 hours, with updates as needed
• Distinct from AIRMETs, which cover moderate-severity hazards

Memory trick: Convective SIGMET = Storms, hail, tornadoes—SIGnificant convective threats

The center of gravity is found by dividing the total moment (weight × arm) by the total weight of the aircraft.

• Moment = weight × arm
• CG = total moment ÷ total weight
• Must fall within the manufacturer's approved CG range

Memory trick: Moment ÷ Weight = Where it sits.

Lateral center of gravity is found by dividing total moment (sum of weight × lateral arm for each item) by total weight, then compared to the aircraft's lateral CG limits.

• Lateral arms are measured left (-) and right (+) of the helicopter centerline
• Moment = weight × arm for each item, summed algebraically
• CG = total moment ÷ total weight
• Must fall within the manufacturer's approved lateral CG envelope

Memory trick: Add up left and right moments like a seesaw balance.

As pressure altitude and temperature increase, air density decreases, reducing the mass of air available for combustion and lowering maximum engine power output.

• Higher pressure altitude reduces available oxygen for combustion
• Higher temperature further reduces air density
• Torque-available charts are used to verify sufficient power margin before flight

Memory trick: Thin, hot air starves the engine of the oxygen it needs.

Sectional charts use shading to depict Class E airspace floors: magenta vignette = 700 ft AGL floor, blue vignette = 1,200 ft AGL floor, dashed magenta line = surface area, and no shading (unmarked) = 14,500 ft MSL floor.

• Magenta vignette = 700 ft AGL floor
• Blue vignette = 1,200 ft AGL floor
• Dashed magenta line = surface-based Class E
• No shading = 14,500 ft MSL default floor

Memory trick: Magenta = 'Medium-low' 700 ft floor; Blue = 'Bit higher' 1,200 ft floor.

Obstructions on sectional charts are labeled with two numbers: the top number is elevation MSL, and the number in parentheses is the height AGL.

• Top number = MSL elevation
• Parenthetical number = AGL height
• Symbol shape indicates lighted vs unlighted
• Group obstructions use a different symbol

Memory trick: Parentheses 'hug the ground' — that's your AGL number.

Distance is measured using the latitude scale on the chart's side borders, where each minute of latitude equals 1 nautical mile.

• Latitude lines run east-west, minutes marked on side borders
• 1 minute of latitude = 1 nautical mile everywhere on Earth
• Longitude spacing varies with latitude, so it can't measure distance

Memory trick: Latitude = 'ladder' rungs of nautical miles up the side.

Third-class medical certificates are valid for 60 calendar months if the pilot is under 40 on the exam date, and 24 calendar months if 40 or older.

• Under 40: 60 calendar months
• 40 or older: 24 calendar months
• Expires last day of the expiration month, not exact issue date

Memory trick: Under 40, five years to go; forty-plus, two years, that's the flow

A hinge or axis on the rotor hub that allows each blade to rotate about its spanwise axis, changing its pitch angle for collective and cyclic control.

• Also called the pitch-change axis
• Works with pitch horn and pitch links driven by the swashplate
• Distinct from flapping (up/down) and lead-lag (fore/aft) hinges
• Present in fully articulated and semirigid systems

Memory trick: Feather = twist the blade like turning a feather in your fingers.

Isogonic lines on a chart connect points of equal magnetic variation; the agonic line is the isogonic line representing zero variation.

• Variation is the angle between true north and magnetic north
• Isogonic lines are labeled with variation values
• Agonic line = 0° variation
• Variation changes with location, unlike deviation which changes with heading

Memory trick: Agonic = 'A-Gone-ic' — variation is gone (zero).

Controlled airspace around airports with an operating control tower but no radar approach control, depicted by a blue dashed line.

• Typically extends from the surface to 2,500 feet AGL
• Radius usually 4 nautical miles, tailored to instrument approach needs
• Two-way radio communication must be established before entry

Memory trick: Dashed Blue = D for 'Dial before you Descend' into the pattern.

A visual illusion in which a pilot mistakes a sloping cloud formation, ground light pattern, or the milky way for the actual horizon, leading to an incorrect aircraft attitude.

• Common at night or in reduced visibility
• Pilot subconsciously aligns aircraft with the false reference
• Cross-checking flight instruments prevents this illusion

Memory trick: City lights on a hillside can fake a tilted horizon.

An increase in rotor efficiency that occurs when hovering within approximately one rotor diameter of the surface, caused by reduced induced drag.

• Effective within about one rotor diameter of the surface
• Reduces induced drag and required power
• Greatest over smooth, hard surfaces; reduced over tall grass, water, or slopes

Memory trick: Close to the ground, the air 'cushions' the rotor — less power needed.

A mechanical device consisting of stationary and rotating rings that transfers cyclic and collective control inputs from the non-rotating airframe to the rotating rotor blades.

• Tilting the swashplate changes blade pitch cyclically (once per revolution)
• Raising/lowering the swashplate changes collective pitch (all blades equally)
• Connected to blade grips via pitch links
• Essential link between pilot controls and rotor system

Memory trick: Swashplate 'swashes' pilot commands up to the spinning blades.

Maximum density altitude at which a helicopter can hover, either in ground effect (IGE) or out of ground effect (OGE); OGE is always lower due to increased power requirements.

• Ground effect reduces induced flow and power required
• IGE hover ceiling is typically higher than OGE
• OGE hover is used for performance planning at high density altitude sites

Memory trick: Ground gives a boost — lose it, lose altitude.

A technique of gently pinching the nose and blowing with the mouth closed to force air through the Eustachian tube and equalize middle ear pressure during descent.

• Used to relieve middle ear block during descent
• Should be done gently to avoid inner ear damage
• A cold or sinus congestion can prevent proper equalization, requiring the pilot not to fly

Memory trick: 'Pinch, blow, pop' — clear the tube like popping ears on a plane.

14 CFR 91.205(b) lists the minimum instruments and equipment required for VFR day flight, memorized by the mnemonic 'A-TOMATO FLAMES.'

• Attitude indicator is NOT required for VFR day, only for IFR
• Required VFR day items include altimeter, airspeed indicator, compass, tachometer, oil pressure/temp gauges, fuel gauge, seatbelts, ELT (fixed-wing)
• Additional items required for night and IFR flight

Memory trick: 'ATOMATOFLAMES' spells out day VFR gear — no attitude indicator inside it.

BECMG (becoming) indicates a gradual, permanent change in conditions expected to occur within the specified time range, with new conditions in effect by the end time.

• Time range format is DDHH/DDHH (day/hour to day/hour)
• Change is gradual, not instantaneous
• Conditions after the end time are as forecast in the BECMG group

Memory trick: 'FM flips fast, BECMG builds gradually, TEMPO is temporary, PROB is a probability'

A condition where, in the absence of visual references, the eyes relax to a near focal distance of 10-30 feet, making distant objects like aircraft appear out of focus and harder to see.

• Occurs in dark, featureless sky or over water/terrain at night
• Eyes default to near focus without conscious effort
• Pilots should consciously refocus at varying distances during scans

Memory trick: Nothing to see, eyes settle near — traffic sneaks in unseen.

Class B airspace requires an explicit two-way ATC clearance to enter, along with a Mode C transponder, two-way radio, and appropriate pilot certification/training.

• Clearance must be explicit ('cleared into Class Bravo')
• Mode C transponder required
• Student pilots need specific endorsements
• Surrounds the nation's busiest airports

Memory trick: Class Bravo = 'Big permission needed' before entry.

To carry passengers at night, a pilot needs 3 takeoffs and landings to a full stop at night within the preceding 90 days, per 61.57(b).

• 3 full-stop landings required
• Must occur at night (1 hr after sunset to 1 hr before sunrise)
• Valid for 90 preceding days

Memory trick: Three landings in the dark keep your passengers safe for 90 days

Under 14 CFR 91.157, helicopter pilots are exempt from the instrument rating requirement that applies to airplane pilots operating under special VFR at night.

• Airplanes need instrument rating for night SVFR
• Helicopters are exempt from that requirement
• SVFR still requires ATC clearance and ground visibility rules
• Applies within Class B, C, D, and E surface areas

Memory trick: Helicopters get a 'night pass' that fixed-wings don't.

An increase in rotor efficiency that occurs as the helicopter accelerates out of its own rotor downwash into clean, undisturbed air.

• Occurs at approximately 16-24 knots
• Rotor system requires less power for the same lift
• Often felt as a slight pitch-up or vibration change during transition

Memory trick: Around 20 knots, the rotor breaks free of its own turbulent air.

AROW stands for Airworthiness certificate, Registration, Operating limitations, and Weight and balance data — all required aboard the aircraft.

• A = Airworthiness certificate
• R = Registration certificate
• O = Operating limitations
• W = Weight and balance data

Memory trick: AROW: like an arrow, these documents fly with the aircraft everywhere

A pilot may not act as a crewmember within 8 hours after consuming alcohol, while under the influence, or with a blood alcohol concentration of 0.04% or greater.

• 8-hour minimum interval ('8 hours bottle to throttle')
• 0.04% BAC limit
• No acting as crewmember while using drugs that affect safety
• Applies to all crewmembers, not just PIC

Memory trick: 8 hours bottle to throttle, 0.04 is the ceiling.

Gross weight divided by main rotor disk area (lb/ft²); higher disk loading means more power is required to hover and a higher autorotational descent rate.

• Disk area = π × r² (r = half of rotor diameter)
• Disk loading = gross weight ÷ disk area
• Higher disk loading requires more power to hover
• Higher disk loading increases autorotation rate of descent

Memory trick: More weight per circle of rotor blades = more power to lift, faster fall if engine quits.

14 CFR 61.113(d) permits a private pilot with at least 200 hours logged flight time to act as PIC for compensation on an aircraft sales demonstration flight.

• Minimum 200 hours total flight time required
• Applies specifically to sales demonstration flights
• One of several narrow exceptions to the general no-compensation rule in 61.113(a)

Memory trick: '200 hours to show it off' — enough experience to sell the aircraft in flight.

Forms when a fast-moving cold front catches up to and overtakes a slower warm front, lifting the warm air mass off the surface. Can be a cold-type or warm-type occlusion depending on relative air mass temperatures.

• Cold-type occlusion: coldest air undercuts, weather resembles cold front
• Warm-type occlusion: overtaking air is less cold, weather resembles warm front
• Often brings complex, prolonged precipitation and cloud patterns

Memory trick: Occlusion = a fast cold front tackling a slow warm front from behind

The tendency of a rotor blade to speed up or slow down in its plane of rotation as its center of mass moves closer to or farther from the axis of rotation during flapping, per conservation of angular momentum.

• Blade flaps up → mass moves inward → blade speeds up (leads)
• Blade flaps down → mass moves outward → blade slows down (lags)
• Accommodated in fully articulated rotor systems by the lead-lag (drag) hinge

Memory trick: Like a spinning skater pulling in arms — blade speeds up as mass moves inward.

Below 10,000 ft MSL and more than 1,200 ft AGL in Class E airspace, VFR requires 3 SM visibility and 500/1,000/2,000 cloud clearance.

• 3 SM visibility required
• 500 ft below clouds
• 1,000 ft above clouds
• 2,000 ft horizontal from clouds

Memory trick: '3-5-2-1-1' ladder — 3 SM/500/1000/2000 below 10,000; 5 SM/1000/1000/1 mile above.

A complete weather and NOTAM briefing covering the entire proposed route, requested when the pilot has not yet obtained any prior briefing.

• Includes current conditions, forecasts, winds aloft, AIRMETs/SIGMETs, and NOTAMs
• Requested for the first briefing before a flight
• Differs from Abbreviated (update) and Outlook (6+ hrs out) briefings

Memory trick: 'Standard Starts it, Abbreviated Adds, Outlook is Off in the future'

Turbulence that develops on the leeward side of mountains when strong winds (typically 25+ knots) blow perpendicular to a ridge, causing oscillating wave patterns, severe turbulence, and strong downdrafts.

• Requires strong wind (usually >25 kt) roughly perpendicular to ridge
• Produces rotor clouds and lenticular clouds as visual clues
• Downdrafts can exceed the climb capability of aircraft

Memory trick: Wind over a mountain ridge rolls like ocean waves crashing downwind

An external load carried beneath a helicopter shifts the effective center of gravity and can introduce pendulum-like oscillations that couple with helicopter motion, potentially causing instability.

• Load acts like a pendulum suspended below the aircraft
• Swinging/oscillating loads can induce dangerous pitch/roll/yaw coupling
• CG location changes with load position and weight
• Pilots must monitor load behavior and limit airspeed/maneuvering accordingly

Memory trick: A swinging load is a pendulum trying to steer your helicopter.

A flight review under 61.56 consists of at least 1 hour of flight training and 1 hour of ground training, valid for 24 calendar months.

• Required every 24 calendar months
• Minimum 1 hour flight + 1 hour ground training
• Calendar months expire at month's end, not exact day

Memory trick: Two years, two hours: one up, one down (flight and ground)

A built-in reduction in pitch angle from root to tip of a rotor blade, designed to more evenly distribute lift along the blade span by compensating for the higher rotational velocity at the tip.

• Blade tip travels faster than blade root due to rotational geometry
• Without twist, tip would produce disproportionately more lift than root
• Twist improves rotor efficiency and reduces structural loads

Memory trick: Blade twist: less pitch at the fast tip keeps lift even, like dimming a bright spot.

A vestibular illusion where a pilot in a prolonged turn no longer perceives turning, and pulling back on the controls without leveling the wings tightens the spiral and descent.

• Occurs after sustained constant-rate turns in IMC
• Fluid in semicircular canals stabilizes, masking sensation of turn
• Trust instruments, not sensations, to recover

Memory trick: Digging your own grave by pulling back blind in a spiral.

A cold front occurs where advancing cold air undercuts and lifts warmer air, producing a narrow zone of intense, often severe weather followed by a rapid temperature drop and wind shift.

• Fast-moving fronts produce narrow bands of cumulonimbus, showers, and possible thunderstorms
• Abrupt wind shift, often clockwise, occurs at passage in the Northern Hemisphere
• Temperature drops sharply and pressure typically rises after passage
• Turbulence and gusty surface winds are common near and behind the front

Memory trick: Cold front = 'Cold and Quick' — sharp change, sudden shift, short but violent

14 CFR 91.126(b)(2) permits helicopters at nontowered airports to fly a pattern other than the standard fixed-wing pattern, as long as fixed-wing traffic flow is not disrupted.

• Standard fixed-wing pattern is left turns unless indicated otherwise
• Helicopters may deviate to avoid conflict
• Rule reflects helicopters' unique low-speed/vertical approach capability

Memory trick: Helicopters get a 'free pass' on pattern shape, as long as they don't crowd the airplanes.

AIRMETs (Airmen's Meteorological Information) advise of weather hazards significant to light aircraft that are less severe than SIGMET criteria.

• AIRMET Sierra: IFR conditions and mountain obscuration
• AIRMET Tango: moderate turbulence and sustained surface winds over 30 knots
• AIRMET Zulu: moderate icing and freezing levels
• AIRMETs are issued every 6 hours with updates as needed

Memory trick: Sierra=Sight (IFR/mtn obscuration), Tango=Turbulence, Zulu=iZe (icing)

A microburst is a small-scale, intense downdraft from a thunderstorm or convective cell that produces a rapid change from headwind to tailwind near the surface, hazardous to aircraft on approach or departure.

• Causes airspeed gain (headwind) followed by rapid airspeed loss (tailwind)
• Associated with strong convective downdrafts, especially virga and thunderstorms
• Effects last only a few minutes but can be catastrophic at low altitude
• Recovery requires immediate maximum power application and minimizing altitude loss

Memory trick: Microburst = 'Micro' size but MACRO danger: headwind then tailwind then down

Under 91.113(d), the right-of-way order (highest to lowest) is: aircraft in distress, balloon, glider, airship, then airplane/rotorcraft towing others, then other airplanes/rotorcraft.

• Aircraft in distress has right of way over all others
• Balloons rank above gliders
• Gliders rank above airships, which rank above airplanes/rotorcraft

Memory trick: Distress, Balloon, Glider, ship, then plane and copter — least maneuverable wins

A personal preflight self-assessment checklist pilots use to evaluate their physical and mental fitness to fly.

• Stands for Illness, Medication, Stress, Alcohol, Fatigue, Eating
• Should be reviewed before every flight
• Stress includes psychological, financial, or family pressures

Memory trick: I'M SAFE to fly if I check all six boxes.

The portion of the power-required curve at low airspeeds where power required increases as airspeed decreases, opposite to the normal relationship at higher speeds.

• Occurs below the speed for minimum power required
• Induced drag/power dominates at low airspeed
• Requires more power to slow down or hover, not less
• Important for understanding low-speed flight and approach-to-hover power management

Memory trick: Below minimum-power speed, slower means you must push harder—reverse of normal.

An imaginary 30 NM radius circle around a Class B primary airport, from the surface up to 10,000 feet MSL, within which a Mode C transponder and ADS-B Out are required.

• Defined by 14 CFR 91.215 and 91.225
• Applies even outside the actual Class B lateral boundaries
• Extends from surface to 10,000 feet MSL

Memory trick: Veil = a 30-mile 'veil' no one can hide under without Mode C.

A rotor system with separate flapping, feathering, and lead-lag hinges that allow each blade to move independently of the others.

• Usually has three or more blades
• Flapping hinge relieves dissymmetry of lift
• Lead-lag hinge compensates for Coriolis effect
• Feathering hinge changes blade pitch angle

Memory trick: Fully articulated = fully free-moving blades (Feather, Flap, Lag)

Pilots must establish two-way radio communication with ATC before entering Class D airspace and maintain it while operating within it.

• Applies to Class D surface areas
• Must establish contact before entry, not just attempt it
• Communication must continue throughout operations in the airspace

Memory trick: 'Dial before you enter D' – radio contact required first.

Converting true course to compass heading requires sequentially applying wind correction angle, magnetic variation (East subtract, West add), and compass deviation.

• TC + WCA = TH
• TH + West variation (or - East) = MH
• MH + deviation (algebraic) = CH
• Memory aid: 'East is Least, West is Best' for variation

Memory trick: East is Least, West is Best — add west variation, subtract east.

Structural icing forms when an aircraft flies through visible moisture at freezing temperatures; the type depends on droplet size and freezing rate.

• Clear ice: large droplets, spreads before freezing, smooth/dense/hard to remove
• Rime ice: small droplets, freezes instantly, rough/milky/brittle
• Mixed ice: combination of clear and rime characteristics
• Icing requires visible moisture and temperatures at or below freezing

Memory trick: Clear ice = 'clear and Cruel' (smooth, hard, dangerous); Rime = 'Rough and Removable'

Pressure altitude corrected for nonstandard temperature; it directly affects helicopter performance such as lift, power available, and hover capability.

• Rises with higher temperature and higher elevation
• High density altitude reduces engine and rotor performance
• Rule of thumb: DA = PA + 120 × (OAT − ISA temp at that altitude)

Memory trick: Hot and high, helicopters sigh (less lift, less power).

Under 91.409(a), most aircraft must receive an annual inspection within the preceding 12 calendar months to remain airworthy, valid through the end of the 12th month.

• Required within preceding 12 calendar months
• Calendar months expire at the end of the month, not the exact day
• Applies to aircraft not operated under a progressive or approved inspection program

Memory trick: An annual is like a birthday party that lasts until the end of the month

An aerodynamic asymmetry between the front and rear of the rotor disk during low-speed forward flight transition, where the rear disk produces more lift than the front, causing vibration and pitch/roll tendencies.

• Occurs during transition to forward flight (~10-20 kts)
• Rear rotor disk has greater induced flow lag, producing more lift
• Often causes a slight pitch-up and low-frequency vibration

Memory trick: Transverse flow: front is 'flowed out,' rear is fresh — imbalance shakes the disk.

Allowing rotor RPM to decay below the normal range during autorotation increases blade angle of attack toward stall, reducing lift and increasing rate of descent, especially critical at high density altitude.

• Low RPM increases blade angle of attack, risking blade stall
• High density altitude compounds the lift deficit
• Pilots must monitor and manage RPM using collective pitch throughout autorotation

Memory trick: Low RPM = blades 'gasping' for lift, stalling and dropping you faster

The TO/FROM flag shows whether the selected OBS course leads toward or away from the station; when FROM, the radial equals the OBS setting, and when TO, the radial is the reciprocal of the OBS setting.

• FROM = radial equals OBS setting
• TO = radial equals reciprocal of OBS setting
• CDI centered confirms you are on that course line
• Reciprocal = OBS ± 180°

Memory trick: TO means you're 'Turned Opposite' the radial you dialed.