Weight before fuel: payload runs out first
A Meridian holds 170 gallons. With a family of five aboard and nothing in the lockers it can carry about 108 of them, and 200 lb of weekend bags takes that to 78. Most owner-pilots know this in their bones; the app now does the arithmetic on every trip so the crew does too.
01The four numbers
Basic empty weight, maximum takeoff weight, maximum landing weight and maximum zero fuel weight. Settings holds them per airplane and the presets load typical figures (a Meridian: about 3,420 empty, 5,092 takeoff, 4,850 landing and zero fuel). Replace them with the figures from your own weight and balance sheet; airplanes drift after avionics and interiors.
02Payload, then fuel
A trip takes a passenger count and a bag weight. Payload is people at your per-person weight (190 by default) plus bags. Zero fuel weight is empty plus payload, and it has to stay under max zero fuel weight. Whatever is left between zero fuel weight and max takeoff is available for fuel, at 6.7 pounds a gallon for Jet A. The trip header shows all of it in one line, and the leg cards cap departure fuel at the smaller of the tanks and that figure.
03Landing weight
Each leg also shows takeoff weight and landing weight. Landing weight is zero fuel weight plus the fuel you land with, and on a short hop with full tanks it is easy to land over the limit. The card turns that red so it gets noticed on the ground rather than in the flare.
04What this is not
There is no center of gravity here. Arms, moments and the envelope live in the POH and on your loading sheet, and JetDesk says so next to every weight. The purpose is to catch the trip that was never going to work with full tanks before anyone starts pumping.
More field notes
Reserve fuel, and the alternate nobody plans
How JetDesk decides whether a leg makes reserve, and why the alternate is where most fuel stops really come from.
Why block time swings twenty minutes
How the FAA winds aloft forecast becomes a groundspeed for each leg, and why the return leg costs more than the outbound one.
What the owner report should say
The monthly numbers an aircraft owner actually wants, and why estimate versus actual matters more than the total.