Rules of thumb (ROT) are quick ways / mental aids to calculate a large array of ground and in-flight information which can simplify your life (and let your brain get back to other things). These are alphabetical.
NOTES:
- CG = climb gradient (FPNM), also degrees nose up from level
- DG = descent gradient (FPNM), also degrees nose down from level
- DIST = distance
- FPM = feet per minute (vertical speed indicator, this is a RATE & depends on groundspeed)
- FPNM = feet per nautical mile (this is a GRADIENT and doesn't change with groundspeed)
- GS = ground speed (divide GS / 60 to get NMPM)
- HAT = height above touchdown
- MPM = miles per minute (a version of groundspeed [GS])
- NMPM = nautical miles per minute (GS / 60)
- PDP = planned decision point (in conjunction with a visual descent point [VDP])
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- 5 rules-of-thumb you can use on your next flight.
- Crosswind, takeoff and landing, descents, ILS
- 5 rules-of-thumb you can use on your next flight.
- Glideslopes, descents, course corrections, windshear, gusty approaches.
- 50/70 Rule (for aborting takeoffs).
- It should be 50% of planned takeoff distance, not runway.
- 60-1 rule (probably the most universal)
- Altitude: see Descents below.
- Approaches (in gusty winds): add half the gust factor to normal final speed
- Civil Twilight: usually 20-35 after sunset
- Climb gradient
- Climb gradient (FPNM) to climb rate (FPM) using ground speed (GS)
- NMPM x FPNM = FPM (350 FPNM needed @ 80kts = 466 FPM)
- FPNM = DG (angle) x NMPM (GS) x 100.
- Course corrections (1 degree is 1 nm at 60 nm from a VOR station)
- Crosswind (estimate)
- 30 degrees off = 50% wind speed
- 45 degrees off = 75% wind speed
- 60 degrees or more off = ~100%
- Descents:
- 1 degree of descent = 100 feet lost in 1 NM (this is gradient)
- Altitude to lose/distance = FPNM (which is also degrees nose down)
- Altitude to lose/time = FPM (which is vertical speed)
- Pro tips for private pilots: descend like a jet jockey.
- When to begin descents?
- 3-6 Rule: ALT/3 (distance) and 5 or 6 x GS (descent rate)
- ALT/FPM x GS (5000’/500 x 1.5 = 15NM)
- ALT/3 (for 3°) (5000’/3 = 16.67NM). This is altitude to lose.
- Degrees = ALT/DIST (3.3° = 10000' / 30 nm)
- Required rate: ALT/DIST x GS (4900’/7NM x 1.5 = 1050 FPM)
- Fuel:
- Distance / GS = Time
- Time x Fuel Burn Rate
- Glideslope descent rates (for 3 degrees)
- Groundspeed / 2 and add a zero (90 kts = 450 FPM)
- Groundspeed x 5, (120 kts = 600 FPM)
- Remember, this is a RATE not a GRADIENT!
- 3 degree glideslopes always have a 300 FPNM gradient
- Two easy rules-of-thumb for calculating a 3-degree glide slope.
- Gusty wind approaches: add half the gust factor to normal final speed
- ILS course width:
- Crossing the threshold, 1/2 dot localizer deflection = about 1/2 the runway width. So a half dot off as you approach the runway, you'll be looking at the runway edge lights
- Knowledge Check/Quizzes:
- If you have a 100 knot groundspeed...6Qs.
- You're flying toward fix that's 20 NM… 6Qs.
- Questions by Fly the Wing.
- Landing distance: 10% weight increase = 20% takeoff & landing distance increase
- Master Equation: MPM x FPNM = FPM (or groundspeed x gradient = rate)
- I call this the master equation because it can get you almost anywhere
- Mental math for pilots. (bm)
- Mental math for pilots. (FI).
- PDP = TIME to MAP – (10% of HAT)
- Required rate: ALT/DIST x GS (4900’/7NM x 1.5 = 1050 FPM)
- Takeoff
- 7 ROT for takeoff performance.
- Abort decision (the 50/70 rule).
- My opinion: should be 50% of planned takeoff distance, not runway.
- Reality Check: The 70-50 rule needs to go away. (AOPA)
- Distance:
- 10% weight increase = 20% takeoff & landing distance increase
- Increases about 10% for every additional 1,000 feet of density altitude
- Useful aviation formulas every pilot should know. (FI).
- Weather / Weather Related:
- Hot weather: 3 rules of thumb.
- Summer flying, 3 ROTs.
- Windshear is double peak wind: if a microburst is 30 kts, you could get 60 kts shear
- VDP (visual descent point)
- FPM = DIST x GS
- HAT/3 = DIST @ 300 FPNM (adjust for DME)
- FIG -
