Glossary
Alphabetical reference of every term used across the RotaryXC training tracks. Type in the search box to filter; click a letter to jump.
#
100LL
100-octane low-lead avgas, blue-dyed. Standard for piston helicopters (R22, R44, Cabri G2). Fuel System →
A
Adiabatic cooling/heating
Temperature change resulting from compression or expansion of air with no heat exchange. Rising air cools at the dry adiabatic rate (3°C/1,000 ft) until saturated, then 1.5°C/1,000 ft. Mountain Flying →
ADF Automatic Direction Finder
Receiver for low-frequency NDB transmitters. Indicator shows relative bearing — magnetic bearing = magnetic heading + relative bearing. Instruments →
ACS Airman Certification Standards
FAA standardized testing document per certificate/rating (PPL FAA-S-ACS-15, CPL FAA-S-ACS-16, IFR FAA-S-ACS-14, CFI FAA-S-ACS-29). Replaces the older PTS — adds knowledge and risk management alongside skills. CFI track →
ADM Aeronautical Decision Making
Structured framework for in-cockpit decisions. Models include the Three Ps, DECIDE, and the Five Ps. ADM/CRM →
ADS-B Automatic Dependent Surveillance-Broadcast
Position-broadcasting system. Out required in Class A/B/C airspace and certain Class E per § 91.225. In receives traffic (TIS-B) and weather (FIS-B). Instruments →
AIM Aeronautical Information Manual
FAA's official guide to ATC procedures and pilot/controller communication. Reference, not regulatory.
AIRMET
Airmen's meteorological information — less severe than SIGMET. Three series: Sierra (IFR/mountain obscuration), Tango (turbulence/wind >30 kts), Zulu (icing/freezing levels). Commercial Weather →
ALS Approach Lighting System
Runway approach lighting from the FAF toward threshold. Variants: ALSF-1/2, MALSR, MALSF, ODALS, REIL, SSALR. Sighting at decision altitude lowers minima per § 91.175. ILS approaches →
Alternate static source
Backup static port (often inside the cabin) used when the primary static port is blocked. Reads slightly low. Instruments →
Alternator
Engine-driven AC generator, rectified to DC for the bus. Charges the battery and powers electrical loads in flight. Failure typically annunciates as a low-volts warning. Electrical System →
Aneroid
An elastic capsule that expands or contracts with pressure changes. The mechanism inside altimeters and VSIs. Instruments →
Agonic line
Line on a sectional where magnetic variation is zero — true heading equals magnetic heading along this line. Compare with isogonic lines. Sectional Charts →
Autokinesis
At night, staring at a single isolated light for more than ~10 seconds makes it appear to move. Counter by scanning across multiple references. Vision & illusions →
Angle of attack AOA
The angle between the chord line of an airfoil and the relative wind. Different from pitch angle. Aerodynamics →
Angular momentum
Conservation principle: as a flapping blade's mass moves closer to the rotor mast, it speeds up (and vice versa) to keep angular momentum constant. Why fully articulated rotors need lead-lag hinges. Aerodynamics →
Arm
Horizontal distance from the datum to the center of gravity of an item. Positive aft, negative forward. Used to compute moments in weight & balance. Weight & Balance →
ARROW
Required aircraft documents: Airworthiness, Registration, Radio license (intl), Operating handbook, Weight & balance. Regulations →
ASI Airspeed Indicator
Pitot-static instrument showing indicated airspeed (pitot − static). Color arcs: white (Vfe), green (normal), yellow (caution), red line (Vne). Pitot-static →
ATOMATOFLAMES
Day VFR required equipment per § 91.205(b): Airspeed, Tachometer, Oil pressure, Manifold pressure (if applicable), Altimeter, Temperature gauge (liquid-cooled), Oil temperature, Fuel gauge, Landing gear position, Anti-collision lights, Magnetic compass, ELT, Safety belts. Regulations →
ARTCC Air Route Traffic Control Center
"Center" — provides separation for IFR traffic in the en-route structure. Begins on airways at 1,200 ft AGL. Clearances →
ASR Airport Surveillance Radar
Radar approach providing lateral guidance only (no glideslope). Higher minimums than precision approaches. Approaches →
Attitude indicator AI
Gyroscopic instrument displaying pitch and bank against a horizon reference. The centerpiece of every IFR scan. Instruments →
Autorotation
Unpowered descent in which airflow keeps the rotor spinning. Three rotor regions: driven, driving, stall. Maneuvers →
B
BANK PITCH POWER
Unusual attitude recovery sequence: correct bank, then pitch, then power. Cannot stop the descent until bank and pitch are wings-level/nose-level. Arrivals →
Basic empty weight
Airframe + permanently installed equipment + unusable fuel + full oil. Starting point for every weight & balance computation. See the POH. Weight & Balance →
BECMG
TAF group meaning "becoming." Permanent change between two times — e.g., BECMG 1820 means changing between 1800Z and 2000Z, persisting after. Commercial Weather →
Bernoulli's principle
Faster-moving air has lower pressure. Combined with Newton's third law, explains airfoil lift. Aerodynamics →
BFR Biennial Flight Review
Now called "Flight Review." 1 hour ground + 1 hour flight every 24 calendar months. CFI Responsibilities →
Blade flapping
Vertical motion of a rotor blade — compensates for dissymmetry of lift in forward flight. Aerodynamics →
Black-hole approach
Night approach over unlit terrain or water to a lit destination. No visual references for glide path; pilot tends to descend too steep. Use VASI/PAPI or DME stepdowns. Vision & illusions →
Blowback
Rearward tilt of the rotor disc in forward flight as the advancing blade flaps up and the retreating blade flaps down. Pilot compensates with forward cyclic. Dissymmetry of Lift →
Brownout
Loss of visual reference in a cloud of dust kicked up by rotor downwash during landing/takeoff on dry or dusty surfaces. The snow equivalent is whiteout. Vision & illusions →
BR Mist
METAR code for fog with visibility 5/8 to 6 SM. Below 5/8 SM, the code becomes FG. Commercial Weather →
C
Carb heat
Pre-heat air upstream of the carburetor to prevent or melt induction icing. Causes a slight RPM drop. Systems →
Carburetor ice
Ice in the carburetor venturi when fuel vaporization cools moist air below freezing. Symptoms: RPM drop, rough running. Solution: carb heat. Powerplant →
CAS Calibrated Airspeed
Indicated airspeed corrected for instrument and position errors. From the POH. Instruments →
CDI Course Deviation Indicator
Five dots either side of center, each representing 2° course deviation. Linear distance per dot increases with distance from station. Approaches →
Center of gravity CG
Point through which the aircraft's weight acts. Must lie within the manufacturer's forward and aft limits for controllable flight. Weight & Balance →
Center of pressure
Point on a chord line where the resultants of all aerodynamic forces concentrate. Moves forward as AOA increases. Aerodynamics →
Centrifugal force
Outward force on a rotor blade as it spins. Combined with lift, produces coning. Scales with rotor RPM squared. Aerodynamics →
Chip light
Cockpit warning that metallic particles have bridged a chip-detector plug in the transmission or a gearbox. Sustained illumination — land as soon as practical. Transmission →
CFI / CFII
Certified Flight Instructor / Certified Flight Instructor — Instrument. Authorized to give flight instruction toward certificates and ratings. Valid 24 calendar months. CFI track →
Chord line
Straight line from the leading edge to the trailing edge of an airfoil. Reference for pitch angle and AOA.
Class A/B/C/D/E/G airspace
Six US airspace classes. A is IFR-only above 18,000 MSL. B/C/D require ATC contact. E is controlled. G is uncontrolled. Navigation →
Clear ice
Glossy, dense, transparent ice from slow freezing of large supercooled droplets. Forms 0°C to -10°C. Most hazardous icing type. IFR Emergencies →
Coaxial rotor
Two counter-rotating main rotors on a single mast — torque cancels, no tail rotor required. Kamov design lineage. Tail Rotor →
Collective
Primary helicopter control at the pilot's left side. Raises blade pitch on all blades simultaneously to control vertical thrust. Coupled to throttle via correlator/governor on most singles. Flight Controls →
Confined-area approach
Approach into a small LZ with obstacles on multiple sides. High recon (500 ft AGL) → low recon (100-300 ft) → approach with abort plan. Wind and tail-rotor clearance dominate. Confined-area ops →
Coning
Upward sweep of rotor blades from the resultant of centrifugal force (outward) and lift (upward). Aerodynamics →
Contact approach
IFR-to-visual approach. Pilot must request — ATC cannot initiate. Requires 1 SM flight visibility, clear of clouds, and a published instrument approach at the destination. Approaches →
COIL
Communication barriers: Confusion (symbol vs object), Overuse of abstractions, Interference, Lack of common experience. FOI →
COP Changeover Point
Point on an airway where the pilot switches from one VOR to the next. Prevents loss of nav guidance. Clearances →
Coriolis effect
Aerodynamic: rotor blade flapping up moves mass closer to the axis of rotation, accelerating the blade to conserve angular momentum. Vestibular: head movement in a sustained turn produces an overwhelming false sensation of rotation. Aeromedical →
Cushion collective
Final collective pull at touchdown in autorotation. Uses the remaining rotor inertia to soften ground contact. Pulled too early bleeds RPM; too late means a hard landing. Maneuvers →
Correlator
Mechanical link between collective and throttle on piston helicopters — automatically adjusts power as collective changes. Flight Controls →
CRAFT
IFR clearance components: Clearance limit, Route, Altitude, Frequency, Transponder. Clearances →
CRM Crew Resource Management
Effective use of all available resources (human, hardware, info) for safe operation. Applies single-pilot too. ADM/CRM →
Cyclic
Primary helicopter control between the pilot's legs. Tilts the rotor disc in the direction pushed. Flight Controls →
D
DA / DH Decision Altitude / Decision Height
Used on precision approaches. A decision point — momentary descent below DA is acceptable while initiating the missed. Approaches →
Datum
Reference plane on the aircraft from which all arms are measured. Set by the manufacturer; see the POH. Weight & Balance →
DECIDE
Six-step in-flight decision model: Detect, Estimate, Choose, Identify, Do, Evaluate. ADM/CRM →
Defense mechanisms CPRDRFAR
Compensation, Projection, Rationalization, Denial, Reaction formation, Flight (escape), Aggression, Resignation. FOI →
Demarcation line
Boundary between updraft (windward) and downdraft (leeward) air on a ridge. Steepens with stronger winds. Mountain Flying →
Density altitude
Pressure altitude corrected for non-standard temperature. High DA = thin air = reduced performance. PPL Weather →
DFRATE
Holding clearance components: Direction, Fix, Radial, Altitude, Turns, EFC time. Holding →
Dissymmetry of lift
Unequal lift across the rotor disc in forward flight. Compensated by blade flapping. Aerodynamics →
DME Distance Measuring Equipment
Transponder-based slant-range distance from aircraft to ground station. Range up to 199 NM. Instruments →
Drag dampers
Hydraulic or elastomeric dampers on each blade of a fully articulated rotor, resisting lead-lag motion. A failed damper shifts a blade's natural frequency and can trigger ground resonance. Rotor System →
DroneZone
FAA online portal for sUAS registration and waiver applications. Operating Rules →
Driven / driving / stall regions
Three aerodynamic regions of an autorotating rotor blade. Pilot raises collective to shrink the driving region; lowers collective to enlarge it. Maneuvers →
Dynamic rollover
Lateral rollover when the helicopter pivots on a stuck point. Three conditions: pivot point, rolling motion, exceeding critical angle. Recovery: smooth collective reduction. Hazards →
E
EAS Equivalent Airspeed
CAS corrected for compressibility. Significant only above ~180 kts; at helicopter speeds, EAS ≈ CAS. Instruments →
ELT Emergency Locator Transmitter
Crash-activated transmitter on 121.5 / 406 MHz. Required by § 91.207. Inspect every 12 months; replace battery per manufacturer schedule. Emergency equipment →
EFC Expect Further Clearance
Time after which the pilot proceeds (per lost-comm procedures) if no further clearance has been received. Issued with holding clearances. Holding →
ETL Effective Translational Lift
Sudden lift increase as the rotor leaves its own downwash, typically 16–24 kts. Aerodynamics →
Eustachian tube
Connects middle ear to throat, equalizes pressure. Open during ascent (passive); must be actively opened during descent. Aeromedical →
External-load operations § 133
Helicopter cargo carried below the airframe via a sling. Class A (rigid), B (free-swinging short line), C (free-swinging long line), D (human external cargo). Long-line & vibration →
F
FAA-H-8083-XX
FAA handbook series. Key ones: 8083-2 (Risk Management), 8083-3 (Airplane Flying), 8083-4 (Helicopter Instructor's), 8083-9 (Aviation Instructor's), 8083-15 (Instrument Flying), 8083-16 (Instrument Procedures), 8083-21 (Helicopter Flying), 8083-25 (Pilot's Handbook).
FAR Federal Aviation Regulations
14 CFR. Primary sections referenced on this site: Part 61 (pilot certification), Part 91 (operating rules), Part 107 (sUAS), Part 135 (commercial ops), SFAR 73 (R-22/R-44).
FAF Final Approach Fix
Begin timing here on every approach, even ILS. Marked on charts with a Maltese cross for non-precision and a lightning bolt for precision. Approaches →
FG Fog
METAR code for fog with visibility < 5/8 SM. Commercial Weather →
FIRC Flight Instructor Refresher Course
16-hour course (online or in-person) that satisfies CFI renewal. CFI Responsibilities →
FISH RIB
Hypoxia symptoms: Fatigue, Impaired judgment, Sense of well-being, Headache, Reduced vision, Improper decisions, Blue lips. Aeromedical →
Feathering Feather
Rotation of a blade about its spanwise (long) axis — i.e., pitch change. What cyclic and collective actually command. Flight Controls →
Flare
Pitching the nose up at the end of an autorotation (or approach) to trade airspeed for reduced rate of descent and reduced ground speed. Aggressive on a full-touchdown auto; subtle on a normal approach. Maneuvers →
Fenestron
Eurocopter ducted fan-in-fin tail rotor. Quieter, safer for ground handling, heavier, less efficient at high speed. Tail Rotor →
Föhn effect
Warm dry wind on the leeward side of a mountain after moisture has been wrung out on the windward climb. Mountain Flying →
FOI Fundamentals of Instruction
FAA knowledge test on teaching theory — a prerequisite for the CFI practical. FOI →
FRAT Flight Risk Assessment Tool
Numeric or checklist-based pre-flight risk score with go/no-go thresholds set in advance. ADM/CRM →
Freewheeling unit Sprag clutch
Disengages the rotor from a failed engine so the rotor can keep spinning in autorotation. Systems →
Fully articulated rotor
Rotor system where each blade flaps, leads/lags, and feathers independently. Subject to ground resonance (unlike semi-rigid). Systems →
FZRA / FZDZ
METAR codes for freezing rain (FZRA) and freezing drizzle (FZDZ) — supercooled liquid that freezes on contact with the airframe. Clear-ice producer; exit immediately. Icing →
G
GARRF
Visual illusions: Ground-based, Atmospheric, Runway width, Runway slope, Featureless terrain. Aeromedical →
Glideslope GS
Vertical-guidance component of an ILS. Beam thickness 1.4°, angle typically 3°. Front course only — never trust on a back course. Approaches →
Governor
Sensing device that automatically maintains rotor RPM by adjusting throttle. Common on turbines and many pistons. Flight Controls →
GPS Global Positioning System
Satellite-based navigation. WAAS-augmented receivers support LPV approaches. RAIM monitors signal integrity. Instruments →
GRABCARD
IFR-required equipment per § 91.205(d): Generator, Radios, Attitude indicator, Ball, Clock, Altimeter (sensitive), Rate-of-turn, Directional gyro. Instruments →
Graveyard spiral
Vestibular illusion in which a sustained turn feels straight; pilot pulls back to arrest descent, tightening the spiral. Vestibular illusions →
Gross weight
The aircraft's current total weight in flight. Maximum gross weight is the certification limit; operating gross weight is what you actually loaded today. Weight & Balance →
Ground effect
Reduced induced drag and increased lift efficiency within ~1 rotor diameter of the surface. Aerodynamics →
Ground resonance
Self-energizing oscillation of the fuselage on a fully articulated rotor system. Recovery: lift off (or close throttle if RPM is low). Hazards →
Gyroscopic precession
Force applied to a spinning disc reacts 90° later in the direction of rotation. Compensated by swashplate offset. Aerodynamics →
H
HEMS Helicopter Emergency Medical Services
§ 135 helicopter EMS operations. Single-pilot night IFR profile, time-critical missions, unprepared LZs. Higher IIMC and weather-related risk than most rotorcraft ops. HEMS & Night Ops →
H/V diagram Height/Velocity / Dead Man's Curve
Combinations of altitude and airspeed where survivable autorotation is not possible. Most relevant during takeoff. Aerodynamics →
Hanger bearing
Bearing that supports the tail rotor drive shaft mid-span. Failure introduces vibration and can let the shaft contact the tail boom. Transmission →
Holding
Racetrack pattern flown over a fix while waiting for a clearance. Three entry types — see DFRATE and the 70° pen rule. Holding →
Hover Hovering
Stationary flight — zero translation relative to the ground. Tail rotor counters main-rotor torque, cyclic counters drift, collective holds altitude. Highest-power-required state in the H/V diagram; ground effect reduces required power within ~1 rotor diameter AGL. Hovering →
HOTS Higher Order Thinking Skills
Application, analysis, synthesis, evaluation. CFI's goal — moving students past rote and understanding. Lesson Planning →
HSI Horizontal Situation Indicator
Combines DG and CDI in one instrument. Eliminates reverse sensing on a back-course localizer. Instruments →
Hyperventilation
Over-breathing depletes blood CO2; symptoms (tingling, lightheadedness, dizziness) mimic hypoxia. Recovery: slow controlled breathing, talk out loud, breathe into a bag if needed. Aeromedical →
Hypoxia
Insufficient oxygen reaching tissues. Four types: Hypoxic, Hypemic, Stagnant, Histotoxic. Stages: ICDC. Symptoms: FISH RIB. Aeromedical →
I
IAF Initial Approach Fix
Beginning of the initial approach segment. Provides 1,000 ft terrain clearance. May be skipped under radar vectors. Approaches →
IAS Indicated Airspeed
What the airspeed indicator reads — uncorrected for any errors. Instruments →
ICEFLAGGS
Vestibular illusions: Inversion, Coriolis, Elevator, False horizon, Leans, Autokinesis, Graveyard spin/spiral, Somatogravic. Aeromedical →
IFR Instrument Flight Rules
Operating rules for flight by instruments alone (without external visual reference). IFR track →
IGE / OGE
In Ground Effect / Out of Ground Effect. IGE hover requires less power than OGE. Aerodynamics →
IIMC Inadvertent IMC
VFR pilot enters IMC unintentionally. Recovery: maintain control, climb, course toward VMC, communicate, comply. IFR Emergencies →
ILS Instrument Landing System
Precision approach combining localizer (lateral) + glideslope (vertical) + marker beacons. Approaches →
IMARTHA
IFR arrival prep: ATIS, Approach brief, Frequencies, Workload split. Front-load prep in cruise. Arrivals →
IMSAFE
Personal preflight: Illness, Medication, Stress, Alcohol, Fatigue, Emotion. ADM/CRM →
INCRAM
Approach brief: ID, NAVAID, Communication, Radio, Altitude, Missed approach. Approaches →
Induced drag
Drag produced as a byproduct of lift. Decreases as airspeed increases. Aerodynamics →
Induced flow
Downward airflow through the rotor disc — the air the rotor pushes down to produce lift. Aerodynamics →
IPC Instrument Proficiency Check
Required to regain instrument currency after 6 months of inactivity beyond the 6-month grace period. Endorsements →
Isogonic line
Magenta dashed line on a sectional showing magnetic variation. East is least, west is best. Navigation →
J
Jet-A
Kerosene-based turbine fuel. Used in turbine helicopters; never in piston engines. Fuel System →
K
Kollsman window
Adjustable barometric scale on the altimeter. Setting 29.92 = pressure altitude; setting local altimeter = indicated altitude. Instruments →
L
LAANC
Low Altitude Authorization and Notification Capability. Online approval system for sUAS in controlled airspace. Operating Rules →
LDA Localizer-type Directional Aid
Localizer not aligned with runway. Course width 3°–6°. Approaches →
Lead-lag
Forward-aft motion of a rotor blade in the plane of rotation. Accommodates the speed change a flapping blade undergoes via conservation of angular momentum. Only present on fully articulated rotors. Rotor System →
Lee waves
Standing waves on the leeward side of a mountain ridge. Lenticular and rotor clouds reveal them when air is moist. Mountain Flying →
LLWAS Low-Level Wind Shear Alert System
Network of anemometers around an airport detecting wind shifts at the surface. Alerts ATC; controllers relay to pilots on approach. Wind shear →
Localizer LOC
Lateral-guidance component of an ILS. Course width 5°. Range 18 NM, 4,500 ft above antenna. Odd tenths between 108–112 MHz. Approaches →
Long-line
Class B/C external-load operation using a 50-200 ft line. Pilot looks through the chin bubble or a side door, and references the load — not the aircraft — for hover position. Long-line & vibration →
Low-G Pushover
Rotor unloaded (G < 1). In a semi-rigid head, tail-rotor thrust rolls the unloaded disc right; the pilot's instinct to add left cyclic causes mast bumping. Recovery: gentle aft cyclic to reload the rotor. Rotor System →
LTE Loss of Tail Rotor Effectiveness
Aerodynamic — not mechanical. Most common at low airspeed with high power. Aerodynamics →
M
Magnus effect
Lift generated by a rotating cylinder due to differential surface velocity. Underlies how rotating airfoils produce lift. Aerodynamics →
Mayday
International distress call for immediate threat to life — fire, structural failure, loss of control. Format: "Mayday Mayday Mayday, [callsign], [position], [intentions]." Higher priority than Pan-Pan. Emergency comms →
Marker beacon
Audio + visual signal at fixed points along an ILS — Outer (blue, 400 Hz, ~4-7 NM), Middle (amber, 1300 Hz, ~3,500 ft from runway), Inner (white, 3000 Hz, only on Cat II/III). Largely replaced by GPS waypoints. ILS approaches →
MARVELOUS VFR C500
Mandatory IFR reports: Missed approach, Airspeed change, Reaching hold, VFR-on-top, ETA, Leaving hold, Outer marker, Unforecast wx, Safety, Vacating, Final fix, Radio failure, Compulsory reporting points, 500 fpm climb/descent inability. Holding →
Mast bumping
Semi-rigid (teetering) rotor failure mode. In low-G, teetering exceeds the mechanical stop and the hub contacts the mast — typically catastrophic. Cause of several fatal Robinson accidents. Rotor System →
MCA Minimum Crossing Altitude
Lowest altitude to cross a fix when proceeding into a higher MEA segment. Clearances →
MDA Minimum Descent Altitude
Hard floor on non-precision approaches. Cannot descend below without required visibility and runway environment. Approaches →
MEA Minimum Enroute Altitude
Guarantees usable nav signal over an airway segment. Lost-comm: fly the highest of MEA / Expected / Assigned. Clearances →
METAR
Hourly weather observation. Format: station, time, wind, vis, weather, sky, temp/dew, altimeter. PPL Weather →
Microburst
Small (< 2.5 NM), short-lived (< 15 min), high-intensity downburst. Up to 6,000 fpm down, 90 kt headwind/tailwind shear. Commercial Weather →
Missed approach point MAP
The point at which a missed approach must begin if visual references aren't established. On precision: at DA. On non-precision: at a designated fix or after timing from FAF. Approaches →
MOA Military Operations Area
Airspace separating military activity from IFR traffic. VFR may enter when active (caution recommended). Navigation →
MOCA Minimum Obstruction Clearance Altitude
Provides obstacle clearance and nav signal within 22 NM of a VOR. May be lower than MEA. Clearances →
Moment
Weight × arm. The rotational force an item exerts about the datum. Total CG = total moment ÷ total weight. Weight & Balance →
MON VOR Minimum Operational Network
Backup VOR network ensuring usable signal at 5,000 AGL anywhere in CONUS, with a MON airport within 100 NM. GPS-outage redundancy. Approaches →
Mountain wave
Standing wave train downwind of a ridge in stable airflow with strong perpendicular winds (>25 kt). Lenticular clouds at the crests, rotor clouds tumbling below ridge height. Mountain Flying →
MRA Minimum Reception Altitude
Lowest altitude where an off-course NAVAID signal can be received to identify a fix. Used when MRA > MEA at the fix. Clearances →
MSA Minimum Sector Altitude
Lowest altitude providing 1,000 ft clearance over obstacles within a 25 NM sector around a navaid. Emergency reference on approach plates. Clearances →
N
NDB Non-Directional Beacon
Low-frequency ground transmitter used by ADF receivers. Mostly legacy. Instruments →
NOTAM Notice to Airmen
Time-critical aeronautical info — runway closures, equipment outages, TFRs. Now officially "Notice to Air Missions." PPL Weather →
NOTAR No Tail Rotor
MD Helicopters anti-torque design using fuselage boundary-layer circulation plus a directed thrust nozzle instead of a tail rotor. Lower acoustic signature, no exposed tail rotor. Tail Rotor →
O
ODP Obstacle Departure Procedure
Provides obstacle clearance from terminal area to en-route structure. May be flown without ATC clearance. Clearances →
OROCA
Off-Route Obstruction Clearance Altitude. 1,000 ft (non-mountainous) / 2,000 ft (mountainous). No nav signal guarantee. Clearances →
Otoliths
Inner-ear structures sensing gravity and linear acceleration. Cannot distinguish gravity from acceleration — source of somatogravic illusion. Aeromedical →
P
PAPI / VASI
Visual glideslope indicators. PAPI = four lights, more precise. VASI = bars, less precise. Approaches →
PAR Precision Approach Radar
Most precise radar approach. ATC issues lateral and vertical guidance throughout. Allows no-gyro procedure. Approaches →
Parasite drag
Drag from non-lifting surfaces — fuselage, hub, gear, tail boom. Increases with airspeed. Aerodynamics →
PAVE
Pre-flight risk inventory: Pilot, Aircraft, enVironment, External pressures. ADM/CRM →
PEDS
VOR check recording: Place, Error, Date, Signature. Approaches →
Pendular action
Fuselage swinging like a pendulum from the rotor mast. Avoid by smooth, deliberate control inputs. Aerodynamics →
Personal minimums
Pilot-set go/no-go limits more conservative than FAA legal minimums — add buffer for currency, fatigue, weather. Often raised after recent lapses. Risk management →
PFACTION
Immediate NTSB notification: Property > $25k, Fire in-flight, Accident, Collision in-flight, Turbine failure, Illness, Overdue, No control. Part 107 Emergencies →
Pinnacle approach
Approach to a ridge or hilltop with no surrounding obstacles. Different airflow than confined area; tail-rotor effectiveness and demarcation line awareness are critical. Confined-area ops →
Pitch angle vs angle of attack
Pitch angle = angle between chord line and rotor hub plane. AOA = angle between chord line and relative wind. Different. Aerodynamics →
Pitot-static system
Pressure-sensitive system feeding ASI, altimeter, VSI. ASI uses both pitot and static; altimeter and VSI use static only. Instruments →
PIREP / AIREP
Pilot reports of weather conditions in flight. AIREPs are automated from airliner systems. Severe/extreme turbulence is reportable as Urgent PIREP. Commercial Weather →
POH Pilot's Operating Handbook
Manufacturer's operating manual — limitations, normal/emergency procedures, performance charts. The authoritative single-aircraft reference. Cabri G2 →
Precession
Gyroscopic property: force applied to a spinning gyro produces a reaction 90° later. Aerodynamics →
PrePARE
Teaching process: Preparation, Presentation, Application, Review and Evaluation. FOI →
Pressure altitude
Altitude indicated when the altimeter is set to 29.92 in Hg. Reference for performance charts and (above FL180) for cruising. Equals true altitude only on a standard day; correct for non-standard temperature to get density altitude. Density altitude →
Profile drag
Friction drag from blade surfaces passing through air. Doesn't change much with AOA, but increases with airspeed. Aerodynamics →
R
RAIM Receiver Autonomous Integrity Monitoring
GPS receiver function that checks signal integrity. Required for non-WAAS GPS approaches. Instruments →
Relative wind
Direction of airflow relative to the airfoil. For a rotor blade, the resultant of rotational velocity, induced flow, and aircraft motion. Aerodynamics →
Remote ID
14 CFR Part 89 — UA broadcast identification system. Required for all Part 107 operations. Part 107 Safe Operation →
Retreating blade stall
In forward flight, the retreating blade's AOA increases until it stalls. Limits VNE. Recovery: reduce collective, reduce airspeed, descend, increase rotor RPM. Hazards →
Rigid rotor
Rotor hub with no flapping or lead-lag hinges — blades absorb dissymmetry of lift via flexural bending. Crisp response, tolerates negative-G. BO-105, Lynx, and some MD designs. Rotor System →
Rime ice
Milky, opaque, brittle ice from rapid freezing of small droplets. Forms -10°C to -20°C, typical in stratus. IFR Emergencies →
Rotor RPM
Helicopter rotor speed. Cabri G2 green arc 515–540 RPM. Low rotor RPM blade stall is fatal — never let it droop. Systems →
S
SBT Scenario-Based Training
Lesson built around a realistic mission. Develops ADM and judgment. Lesson Planning →
SDF Simplified Directional Facility
Localizer-type approach with wider beam (6° or 12°). May be offset from runway centerline by up to 3°. Approaches →
Semi-rigid rotor Teetering
Two-blade rotor, blades teeter as a unit. Used on R22/R44. Cannot lead/lag — immune to ground resonance but vulnerable to mast bumping. Systems →
Settling with power Vortex Ring State
Powered descent into the rotor's own downwash. Three conditions: 300+ fpm descent, low airspeed, 20-100% power. Recovery: Vuichard or standard. Hazards →
SFAR 73
Special Federal Aviation Regulation governing R-22 and R-44. Awareness training, model-specific endorsements, recurrent reviews. Checkride →
SHARPTT
No procedure turn required: Straight-in, Hold-in-lieu, Arc, Radar vectored, NoPT, Teardrop, Timed. Approaches →
SID Standard Instrument Departure
Pre-published departure with obstacle clearance. ATC clearance required to fly. Decline by writing "NO SID" on flight plan. Clearances →
SIGMET
Significant meteorological info — severe weather over wide areas. Convective SIGMETs cover thunderstorms in CONUS. Commercial Weather →
Slant range
Direct distance from aircraft to a DME ground station. Differs from ground distance, especially at high altitude near the station. Instruments →
SLD Supercooled Large Droplets
Liquid water droplets larger than ~50 microns at sub-freezing temperatures. Cause severe ice that runs back past de-ice boots. Exit immediately if encountered. Icing →
Slope landing
Touch uphill skid first, then lower downhill skid. Most common cause of dynamic rollover. Maneuvers →
Somatogravic illusion
Acceleration interpreted as a pitch-up; deceleration as pitch-down. Common on takeoff into IMC — pilot reflexively pushes the nose down. Vestibular illusions →
Spatial disorientation SD
Loss of awareness of attitude, altitude, or motion relative to the earth. Three categories — visual, vestibular (inner ear), and somatosensory ("seat of pants"). Trust the instruments. Spatial disorientation →
SPECI
Special METAR — issued when conditions change significantly between scheduled hourly observations. Same format as METAR with "SPECI" prefix. Weather Products →
Special Use Airspace SUA
Airspace with restricted access: Prohibited, Restricted, Warning, MOA (Military Operations Area), Alert, CFA (Controlled Firing Area), NSA (National Security Area). Each has its own entry rules. Special Use Airspace →
SVFR Special VFR
VFR in controlled airspace with weather below standard minimums. Requires ATC clearance, 1 SM visibility, clear of clouds. Day VFR only without instrument rating + IFR-equipped aircraft. VFR Weather Minimums →
STAR Standard Terminal Arrival
Pre-published arrival route from en-route to a fix near destination. Decline with "NO STAR" on flight plan. Arrivals →
Sterile cockpit
Discipline of restricting non-essential conversation and tasks during critical phases — taxi, takeoff, approach below ~1,000 ft AGL, landing. ADM/CRM →
Stratus / cumulus / cirrus
Three primary cloud types. Stratus = layered/featureless (rime ice common). Cumulus = puffy (turbulence inside). Cirrus = high, ice-crystal.
T
TAF Terminal Aerodrome Forecast
24–30 hour weather forecast for an airport. Issued 4× daily. Format similar to METAR plus time-grouped changes (FM, TEMPO, BECMG, PROB30). PPL Weather →
Tail rotor Anti-torque rotor
Smaller rotor on the tail boom producing lateral thrust that counters main-rotor torque. Pedal input changes its pitch (not RPM). Distinct failure modes — drive shaft, hanger bearing, gearbox, pitch link — drive distinct emergency procedures. Tail rotor →
TAS True Airspeed
Actual speed through the air mass. CAS corrected for non-standard density. ≈ CAS at sea level on ISA day; increases ~2%/1,000 ft. Instruments →
Teardrop entry
Holding pattern entry: cross fix, turn 30° from inbound, fly 1 minute, turn back. Holding →
TEMPO
TAF group meaning "temporary." Fluctuating conditions lasting less than half the period — e.g., TEMPO 1822 9999 means brief unrestricted visibility between 1800Z and 2200Z. Weather Products →
TFR Temporary Flight Restriction
Time-limited airspace closure. Stadium, presidential, disaster, sporting events. Check tfr.faa.gov before every flight. PPL Weather →
The Leans
Most common vestibular illusion — the sensation of leaning after a sub-threshold roll has gone undetected and the pilot then rolls back to level. Vestibular illusions →
Time of useful consciousness TUC
Time between exposure to inadequate oxygen and loss of effective performance. 30,000 ft = 1–2 minutes; 25,000 ft = 3–5 minutes. Aeromedical →
Torque
Newton's third law applied to a rotor: as the engine spins the rotor one way, the fuselage tries to spin the other way. Counteracted by tail rotor thrust. Aerodynamics →
TRACON
Terminal Radar Approach Control. Bridge between airport tower and en-route structure. Mostly Class B/C. Clearances →
Translating tendency Tail rotor drift
Tail rotor thrust pushes helicopter laterally. Counteract with cyclic. Causes left skid to hang lower in CCW rotor systems. Aerodynamics →
Translational lift
Free additional lift gained when the helicopter moves forward through undisturbed air. ETL — effective translational lift — typically reached at 16-24 kt as the rotor moves out of its own downwash. Translational lift →
Transverse flow effect
Right rolling tendency through ETL in CCW rotor systems. Apply left cyclic. Aerodynamics →
"Troubled T"
Black triangle with "T" on approach plate. Indicates non-standard takeoff minimums or ODP exists — look it up in the TPP. Clearances →
Turn coordinator TC
Gyroscopic instrument showing rate of turn and coordination (ball). Senses both yaw and roll due to 30° gyro mounting. Electric. Instruments →
V
VDP Visual Descent Point
Point on a non-precision approach from which a normal descent from MDA may be made if runway is in sight. Approaches →
Vestibular illusions
Sensory mismatches from the inner ear when visual reference is lost. Common forms: the leans, graveyard spiral, Coriolis illusion, somatogravic illusion, elevator illusion. Vestibular illusions →
VFR-on-Top
ATC-authorized IFR clearance to fly VFR cruising altitudes. Comply with both VFR cloud clearance and IFR minimum altitudes. Clearances →
VLOS Visual Line of Sight
Part 107 requirement. Pilot must see the aircraft unaided (corrective lenses OK). Vision aids only momentarily. Part 107 Operating Rules →
VNE Velocity Never Exceed
Maximum airspeed. Limited primarily by retreating blade stall on helicopters. Drops with altitude (-2 kt/1,000 ft on Cabri G2). Systems →
VODGA
VOR receiver checks: VOT, Own check, Dual check, Ground check, Airborne check. Recorded with PEDS. Approaches →
VOR VHF Omnidirectional Range
Ground-based radio nav. Two signals (rotating + reference) determine the radial. Accurate to ±1°. Approaches →
VSI Vertical Speed Indicator
Pitot-static instrument showing rate of climb/descent. Lags 4–5 seconds. Not IFR-required — break the glass for alternate static if blocked. Instruments →
Vuichard recovery
Settling with power recovery — lateral cyclic + power increase + lateral anti-torque. Quickest exit, minimum altitude loss. Hazards →
Vy / Vne / Vfe / Va
V-speeds. Vy = best rate of climb. Vne = never exceed. Vfe = max with flaps extended (not applicable to most helicopters). Va = maneuvering speed.
W
WAAS Wide Area Augmentation System
GPS augmentation providing higher accuracy. Required for LPV approaches. Instruments →
Weathercock instability
LTE region 285°–315° relative wind off the nose. Tail rotor authority decreases as the wind tries to weathervane the nose; demands aggressive pedal input. LTE →
Weight & balance
Datum, arm, moment, basic empty weight, max gross. Forward CG = no flare authority. Aft CG = tail boom strike risk. Systems →
Wind shear / LLWS
Sudden change in wind speed/direction. LLWS = 10 kt or more per 100 ft within 2,000 ft of surface. Commercial Weather →
No matches. Try a shorter or different term.