The Published Gross-Weight Gap Is About 1,200 Pounds

The weight gap is real, but the popular endpoints are wrong—and rotor count alone cannot explain where those pounds went.

Correct the numbers before explaining them

Joby’s current specification lists a maximum gross weight of 2,400 kilograms, or 5,300 pounds. Archer described Midnight at approximately 6,500 pounds when it announced the aircraft’s full transition flight. The widely repeated comparison of 4,800 pounds against 7,000 pounds does not match those manufacturer disclosures.

These are gross or takeoff-weight figures, not empty-airframe weights. They include the aircraft and whatever combination of occupants, baggage and usable energy is allowed for that mission. A comparison should not label the difference “airframe mass” unless both companies publish empty-weight values on the same basis.

Gross weight is an architectural budget

Every aircraft design allocates maximum weight among structure, batteries, propulsion, landing gear, cabin, avionics, thermal systems, occupants and reserves. Both companies target payload around 1,000 pounds for a pilot and four passengers. If those payload statements hold on certified configurations, the remaining difference sits somewhere in empty aircraft and usable energy—but public headline specifications do not reveal the split.

Midnight’s twelve engines, six battery packs and six booms plausibly contribute to installed mass. Joby’s six larger tilt units, four packs and carbon-composite structure create a different ledger. It is still too simple to say Archer is heavier “because it has twelve motors.” Smaller motors may weigh less individually, while structure, battery capacity, landing loads and certification margins can dominate.

Hover power feels every pound

Vertical flight must produce thrust equal to weight before creating any climb. Added mass therefore raises required thrust and generally hover power. The exact penalty depends on total rotor disk area and efficiency; twelve propellers may distribute load differently from six larger ones. Weight alone cannot predict which aircraft uses less energy during takeoff.

The mass also appears during transition, maneuvering and landing. Structure has to carry certified load factors, and landing gear must absorb defined sink rates at approved weights. A heavier aircraft is not automatically inefficient if its propulsion disk area, payload or structure scales with it, but it imposes larger forces on pads and recovery equipment.

Payload fraction gives useful context

A 1,000-pound payload is about 19 percent of Joby’s published gross weight and about 15 percent of Archer’s approximate figure. That arithmetic is informative but incomplete. It does not state empty weight, battery reserve or whether the full payload is available at maximum range. The certified weight-and-balance envelope will show which combinations operators can dispatch.

Cabin utility also matters. Four nominal seats do not guarantee four adults plus bags in every condition. Operators may have to trade passenger load against range or weather, as conventional aircraft do. A lighter gross weight can reduce energy demand while also leaving less room for equipment; a heavier limit can represent capacity as well as burden.

Infrastructure sees dimensions and downwash too

Vertiport design is not governed by weight alone. Rotor span, downwash, charging equipment, fire response and obstacle clearance shape the site. Still, gross weight affects structural loading for elevated pads, towing and disabled-aircraft removal. A 1,200-pound difference can matter when retrofitting a rooftop even if it barely changes a ground-level apron.

Evidence that would settle the comparison

Request certified maximum takeoff weight, operating empty weight, battery mass, maximum payload, payload-range curves and center-of-gravity limits. Add hover energy at matched weight and atmospheric conditions. Those values reveal whether one architecture turns mass into useful range, payload or redundancy more effectively.

Until then, avoid reverse-engineering a complete aircraft from a gross-weight headline. The reliable statement is narrower: Joby publishes 5,300 pounds; Archer has flown transition at roughly 6,500 pounds; both target four passengers plus a pilot; and the detailed mass breakdown is not public.

Weight should be measured at dispatch

Operators will weigh people and bags against a flight-planning limit that changes with route, temperature and reserve. That practical number may sit below structural maximum takeoff weight. A useful service report would show average dispatched mass, payload denied for weight, and energy per occupied seat-mile. Those records reveal whether lower gross weight creates efficiency or simply a tighter payload envelope, and whether a larger aircraft converts its added mass into dependable capacity.

Weight growth during certification should be tracked too. Added shielding, stronger fittings, revised landing gear or production tolerances can consume margin late in a program. The figure that matters is the approved production configuration, weighed with its required equipment—not the cleanest prototype or an early digital model.

Bottom line

The best public comparison is approximately 5,300 versus 6,500 pounds at the gross-aircraft level. That gap affects hover, structures and infrastructure, but its cause cannot be assigned to extra rotors without component and empty-weight data.