Preflight calculators

Three numbers you work out before you fly, and all three are the kind that decide a go or a no-go rather than merely informing one.

Weight and balance plots the loaded aircraft against its envelope, so an out-of-limits result is visible as a point outside a shape rather than buried in arithmetic. Crosswind component resolves a reported wind into the crosswind and headwind parts, which is what you compare against the demonstrated limit and the runway you have. Density altitude is the one that catches people: on a hot day at altitude the aircraft performs as though it were far higher than the field elevation, and the effect on climb rate and takeoff roll is larger than most pilots expect.

These ask you for your aircraft's numbers rather than guessing them. Arms, moments, empty weight and demonstrated crosswind all come from your POH, for your tail number, at its current equipment state. No generic type data is substituted, because a tool that quietly used a typical Skyhawk for your Skyhawk would be worse than no tool.

Weight and balance and density altitude both fail in ways that do not look like failure. An aircraft can be under max gross weight and still be outside its centre of gravity limits, so a weight check that passes tells you nothing on its own: the loaded moment has to land inside the envelope, which is why that tool plots a point rather than printing a total. And density altitude is cumulative, not a single correction. Heat, field elevation and humidity stack, so a 3,000 foot strip on a 35 °C afternoon can perform like 6,000 feet or worse, which lengthens the takeoff roll and flattens the climb gradient at the same time.

The crosswind number people get wrong is the headwind half. Resolving a wind gives both components, and the one that decides whether the runway is long enough is the headwind, not the crosswind. A quartering tailwind reduces the crosswind figure while making the ground roll worse, so reading only the crosswind against the demonstrated limit can pass a takeoff that the runway will not support.

None of this replaces the POH or a preflight briefing. Each page states where its answer stops being reliable, and that section is not boilerplate.