CASA IREX cheat sheet

IFR cruising altitudes in the US use the semicircular rule: magnetic course 0-179 degrees uses odd thousands (3000, 5000, 7000...); 180-359 degrees uses even thousands (4000, 6000, 8000...).

Standard takeoff minimums for part 91 operators are 1 statute mile visibility for single-engine and 1/2 statute mile for multi-engine aircraft; higher published minimums override these.

Alternate airport required when the destination forecast from 1 hour before to 1 hour after ETA has ceiling below 2000 feet or visibility below 3 statute miles.

Precision approach minima use a decision altitude (DA); non-precision approaches use a minimum descent altitude (MDA) with a missed approach point.

Approach category is based on Vref at maximum certificated landing weight: Category A below 91 knots, B 91-120, C 121-140, D 141-165 knots.

Instrument currency requires 6 approaches, holding procedures, and intercepting/tracking courses within the preceding 6 calendar months; a 6-month grace period follows.

The pilot in command may deviate from IFR rules in an emergency but must notify ATC and, if requested, file a report within 48 hours.

Minimum safe altitude (MSA) shown on approach charts guarantees 1000 feet obstruction clearance within 25 nautical miles of the primary navigation facility.

Standard lapse rate in the troposphere is about 2 degrees Celsius per 1000 feet; use it to estimate freezing level from surface temperature and dew point spread.

Freezing rain implies a warm layer aloft above a subfreezing surface layer; structural icing risk is greatest in the 0 to -20 degrees Celsius range.

A ceiling is the lowest broken or overcast layer; VFR flight requires ceiling at least 1000 feet and visibility at least 3 statute miles (Class E surface rules).

Convective SIGMETs cover severe thunderstorms, embedded thunderstorms, hail 3/4 inch or greater, and surface winds 50 knots or more.

Low-level wind shear alerts (LLWAS) and microburst detection matter most within 1000 feet of the surface where recovery margin is smallest.

Density altitude rises about 120 feet per degree Celsius above standard temperature at a given pressure altitude, degrading climb and landing performance.

Icing forecasts use SLD (supercooled large droplets) and ceiling/visibility criteria; known icing conditions require certified anti-ice/deice equipment.

Radar echo tops and VIP levels indicate storm intensity; VIP 3-4 corresponds to moderate to heavy turbulence and hail potential.

VOR radials are magnetic bearings from the station; the CDI shows course deviation and TO/FROM indicates whether the selected course leads to or from the station.

A VOR receiver check tolerance is 4 degrees for airborne/ground checks and 6 degrees for the VOT test; log the date, place, and error.

ILS localizer provides lateral guidance within about 35 degrees of the runway centerline; glideslope is typically 3 degrees and usable only within published coverage.

GPS RAIM availability must be verified for the intended approach; if RAIM predicts outage, a non-GPS approach or alternate means is required.

RNAV (GPS) approaches may be LNAV, LNAV/VNAV, or LPV; LPV provides vertical guidance similar to a Category I ILS but requires WAAS.

DME distance is slant range; error increases with altitude, so DME reads higher than ground distance at high altitude over the station.

NDB/ADF bearings are relative to the aircraft; the ADF needle points to the station relative to the nose, and magnetic bearing equals relative bearing plus magnetic heading.

Required navigation performance (RNP) adds onboard performance monitoring and alerting; RNP 0.3 means lateral deviation contained within 0.3 nautical miles 95 percent of the time.

Weight and balance: total moment equals weight times arm; center of gravity equals total moment divided by total weight, and must fall within the CG envelope.

Density altitude formula approximation: pressure altitude plus 120 times (OAT minus ISA temperature in Celsius).

Takeoff and landing distances increase with altitude, temperature, weight, and tailwind; a 10 percent increase in weight raises takeoff distance roughly 20 percent.

Fuel planning uses trip fuel plus reserve (45 minutes for IFR part 91) plus alternate and contingency fuel; monitor burn against plan at each checkpoint.

True airspeed increases about 2 percent per 1000 feet of altitude for a given indicated airspeed in the lower troposphere.

Load factor in a level turn equals 1 divided by cosine of bank angle; a 60-degree bank yields 2 G and raises stall speed about 41 percent.

Use the aircraft POH/AFM performance charts for the specific model; interpolate between chart lines for weight, altitude, and temperature.

CG too far aft reduces static stability and can make stall recovery difficult; CG too far forward raises stall speed and pitch forces.