11.1 Transport Aircraft Structural Weight Limits: Definitions & Rules

Transport Structural and Operational Weight Limits

A dispatcher checks weights at several different points: before taxi, at takeoff, without usable fuel, and at landing. Each limit answers a different structural or performance question. A large unused takeoff-weight margin does not authorize exceeding zero-fuel weight, a cargo-compartment limit, the center-of-gravity envelope, or a destination landing limit. Use the assigned aircraft's approved weight-and-balance records and performance data; the illustrative numbers below are not Boeing operating data.

Empty Weight and Zero-Fuel Weight

Manufacturer's empty weight, basic empty weight, operating empty weight, and dry operating weight are related accounting terms, but their detailed inclusions vary with the manufacturer's and operator's approved system. Read the applicable definition rather than assuming that every term has one universal Part 25 formula. Basic empty weight commonly includes installed equipment, unusable fuel, and specified operating fluids. Operating empty weight or dry operating weight adds the crew and operating items included in that operator's planning basis, such as catering and specified water quantities. Avoid adding an item twice because it appears both in the aircraft record and on the load sheet.

For this guide's examples, OEW is the aircraft ready for the proposed operation, including its accounted operating items and crew, but excluding usable fuel and payload. Payload includes passengers, their baggage, and cargo under the applicable approved weight program. A maintenance kit may be an operating item or separately accounted load; its classification and location must follow the operator's records.

$$\text{ZFW}=\text{OEW}+\text{Payload}$$

Zero-fuel weight excludes usable fuel, including usable fuel in approved center tanks. Maximum zero-fuel weight (MZFW) is an approved structural limit on this nonfuel weight. Wing fuel can provide bending relief because its distributed weight opposes some aerodynamic wing loading. This explains why an aircraft can have a takeoff limit much greater than its zero-fuel limit. It does not mean wing fuel cancels every structural load, that MZFW is simply fuselage weight, or that adding fuel cures an excessive ZFW. Fuel distribution and any required minimum wing fuel are separate aircraft-specific constraints.

The zero-fuel payload ceiling is:

$$\text{Payload}_{\text{ZFW ceiling}}=\text{MZFW}-\text{OEW}$$

That ceiling is only one comparison. The actual allowable payload can be lower because of takeoff performance, landing performance, CG, compartment loading, floor strength, or required fuel. A dispatcher must resolve all applicable limits together.

Certified Maximum Weights

The certified ramp allowance is an aircraft value; it is not defined by the flight's planned taxi fuel. Operationally, ramp weight equals planned takeoff weight plus expected ground fuel consumption. If the approved MRW is 174,900 lb and MTOW is 174,200 lb, their difference is 700 lb regardless of whether today's taxi estimate is 400 or 800 lb. Both limits still apply.

MLW must not be confused with a touchdown-rate prescription. Under § 25.473, the certification landing-load assumptions include a limit descent velocity of 10 ft/s at design landing weight and 6 ft/s at design takeoff weight, subject to the rule's provisions. These are design conditions, not target operational sink rates. An emergency overweight landing uses the applicable emergency authority and aircraft procedure; runway performance, climb capability, and any required post-landing inspection still matter.

Performance Limits and Loading Equations

A performance-limited takeoff weight incorporates the runway, available declared distances, elevation, temperature, wind, configuration, climb, obstacles, brake energy, tire speed, and other applicable approved restrictions. The second-segment twin-engine certification climb minimum is 2.4% gross, not 2.4% net. Obstacle calculations use the applicable net path. Do not substitute a certification gradient for a full runway analysis.

Landing performance may impose a limit below structural MLW. For the applicable turbine-airplane dispatch calculation, § 121.195 includes the destination dry-runway 60% requirement and the turbojet wet-runway 115% requirement unless the approved provisions permit a different qualifying landing distance. Use the full rule and aircraft data, and check approach and landing climb capability too. A TAF change can require reassessing expected runway conditions; it does not predict one fixed weight penalty for every aircraft.

For a fixed planned takeoff fuel and trip burn, a useful simplified departure comparison is:

$$\text{ATOW}=\min\begin{cases} \text{Structural MTOW}\\ \text{Performance-limited TOW}\\ \text{MZFW}+\text{Takeoff Fuel}\\ \text{Structural MLW}+\text{Trip Burn}\\ \text{Performance-limited LW}+\text{Trip Burn} \end{cases}$$

These comparisons do not waive CG, compartment, fuel-distribution, alternate-airport, en route, or other constraints. Trip burn also changes with weight and routing, so a real planning system may need iteration. A fixed-burn classroom example should say explicitly that its burn is supplied.

$$\text{Allowable Ramp Weight}=\min(\text{ATOW}+\text{Taxi Fuel},\text{Approved MRW})$$ $$\text{Underload}=\text{ATOW}-(\text{OEW}+\text{Payload}+\text{Takeoff Fuel})$$

Underload describes margin against the selected comparison. It is not automatic authorization to board that much cargo or fuel; additional loading can change fuel burn, CG, compartment loading, or the governing limit.

Worked Example: Destination Landing Limit Controls

Assume a hypothetical transport has OEW 91,400 lb, MZFW 138,300 lb, MTOW 174,200 lb, MLW 146,300 lb, and MRW 174,900 lb. For this exercise, supplied departure performance permits 170,800 lb and destination landing performance permits 143,100 lb. Fixed trip burn is 13,400 lb, taxi fuel 800 lb, takeoff fuel 21,200 lb, and booked payload 42,600 lb.

First check nonfuel loading: ZFW is 91,400 + 42,600 = 134,000 lb, below MZFW. The zero-fuel payload ceiling is 138,300 − 91,400 = 46,900 lb. Next calculate the five departure candidates:

ATOW is therefore 156,500 lb. Planned takeoff weight is 91,400 + 42,600 + 21,200 = 155,200 lb, leaving 1,300 lb underload in this fixed-data exercise. Predicted landing weight is 155,200 − 13,400 = 141,800 lb, below both landing limits. Planned ramp weight is 155,200 + 800 = 156,000 lb. Allowable ramp weight is the lesser of 156,500 + 800 and 174,900, or 157,300 lb.

Dispatch Traps and Corrective Decisions

An unexpectedly short taxi can leave actual takeoff weight higher than planned. For example, loading to 174,900 lb and burning only 400 lb leaves 174,500 lb, above a 174,200-lb MTOW. The dispatcher and PIC must obtain a compliant loading or fuel-consumption solution before takeoff using approved procedures and coordination; the guide should not prescribe holding with engines or APU running as a universal remedy. Burning required flight fuel can create a separate fuel shortfall.

If a revised destination analysis lowers allowable landing weight by 6,000 lb, reassess payload, required fuel, runway selection, routing, and the actual resulting landing weight. Offloading payload may solve the issue; a longer suitable runway may also help. Merely choosing a closer alternate does not raise the destination's landing limit. Reducing alternate fuel could lower takeoff and landing weight only if the revised fuel and alternate plan satisfy every applicable requirement. Communicate the revised loads and performance assumptions before release concurrence.

Official References

Source check: 2026-10-12. FAA W&B handbooks and current addenda; AC 120-27F aircraft W&B control; Transport landing-load assumptions § 25.473. For operational use, apply current issued authorizations and the assigned aircraft’s approved data.