The clips

• Legal at takeoff. Out of limits at landing. - keepblueup.com/da40
• 960 ft in the book. 2,093 ft today. - keepblueup.com/grass
• Same wind. Two aircraft. Two answers. - keepblueup.com/xwind
• The 60-second walkthrough of all three tools - keepblueup.com/tour

Open these numbers in Weight & Balance

Short link: keepblueup.com/da40

What the clip says

1. DA 40, 300 lb up front, 40.2 gal of fuel
2. Takeoff CG 94.81 in - inside 94.5 to 102.0
3. Burn 35 gal: landing CG 93.88 in, ahead of the 94.5 in limit
4. The fuel sits aft of the CG. Burn it, and the CG walks forward.
5. Check both ends of the flight.

Where each number comes from

• Takeoff CG 94.81 in - inside 94.5 to 102.0computeWB(DA40, empty 1620 lb @ 94.3 in, front 300 lb, fuel 40.2 gal, trip 35 gal) -> takeoff
• Burn 35 gal: landing CG 93.88 in, ahead of the 94.5 in limitcomputeWB(DA40, empty 1620 lb @ 94.3 in, front 300 lb, fuel 40.2 gal, trip 35 gal) -> landing

Open these numbers in the E6B

Short link: keepblueup.com/grass

What the clip says

1. 1,200 ft field, 28 degC: density altitude 3,048 ft
2. POH ground roll 960 ft becomes about 1,311 ft
3. Dry grass x1.20, safety x1.33: plan on 2,093 ft
4. A rule of thumb, not the chart: use the POH for the go/no-go.

Where each number comes from

• 2,093 ft today.C172S, field 1200 ft, 29.92 inHg, 28 degC, POH ISA sea-level ground roll 960 ft -> DA rule x CAA SS09 dry grass x safety
• 1,200 ft field, 28 degC: density altitude 3,048 ftdensityAltitudeFt(pressureAltitudeFt(1200, 29.92), 28)
• POH ground roll 960 ft becomes about 1,311 ftestimatedTakeoffDistanceFt(960, DA, 12%/1000 ft fixed pitch)
• Dry grass x1.20, safety x1.33: plan on 2,093 fttakeoffConditionFactor(dry-grass, level, safety) = 1.596 - UK CAA Safety Sense SS09 (Aug 2024) p.15

Open these numbers in the E6B

Short link: keepblueup.com/xwind

What the clip says

1. Runway 27, wind 320 at 18 gusting 25
2. Crosswind 12.7 kt, 17.7 kt in the gusts
3. C172S demonstrated 15 kt: the gusts are past it
4. C152 demonstrated 12 kt: even the steady wind is past it
5. Demonstrated is not a limit. Your own limit is.

Where each number comes from

• Crosswind 12.7 kt, 17.7 kt in the gustsrunwayWindComponents(RWY 27 = 275 true with 5E, wind 320/18G25 true)
• C172S demonstrated 15 kt: the gusts are past itC172S_PROFILE.demonstratedCrosswindKt - Cessna 172S POH, Section 4 p. 4-5 - "Maximum Demonstrated Crosswind Velocity: Takeoff or Landing ... 15 KNOTS"; Section 5 Figure 5-4 note: "Maximum demonstrated crosswind velocity is 15 knots (not a limitation)."
• C152 demonstrated 12 kt: even the steady wind is past itC152_PROFILE.demonstratedCrosswindKt - Cessna 152 POH (1978), Section 4 - "Maximum Demonstrated Crosswind Velocity ... 12 knots"

Each clip is a screen recording of this website on a phone-sized screen, driven step by step - no animation, no AI-generated footage and no actors. The caption numbers are generated from the same functions the calculators run, and a test fails the build if a caption and the calculator ever disagree. They are rules of thumb and worked examples for planning practice, not a substitute for your POH and current official weather.

Spotted a number that looks wrong? Email contact@keepblueup.com - corrections are logged publicly on the about page.