Learn how landing weight changes VREF and VAPP, why extra flap can reduce speed, and how pilots choose a safe landing configuration.
In Aviation & Real-World Flying, a heavier landing weight requires a higher approach speed at the same flap setting because the wing must produce more lift. More flap can lower that speed, but weight does not choose the flap setting by itself; runway length, wind, surface condition, climb performance and approved aircraft procedures also control the configuration.
Why does landing weight increase approach speed?
For the same aircraft configuration, reference speed changes approximately with the square root of weight: speed ratio ≈ √(weight ratio). A 10% increase in landing weight therefore produces roughly a 4.9% increase in the aerodynamic speed requirement, assuming the same flap setting and manoeuvre.
Transport aircraft performance systems account for this through VREF or VLS. The target approach speed, usually VAPP, then includes any corrections required for wind, icing, system failures or operating procedure. Our aircraft-specific landing-speed calculation method explains how those speeds fit together.
This relationship is not permission to calculate an operational speed from the formula alone. Use the aircraft's approved tables, flight-management system, performance tool or handbook because configuration, centre of gravity and certification margins are already built into the published speed.
Does a heavier aircraft need more landing flap?
A higher landing weight does not automatically require a greater flap setting. It raises the reference speed for every available configuration; pilots then choose an authorised flap setting that satisfies landing-distance, handling and climb-performance requirements.
Greater flap extension increases maximum lift and usually reduces VREF, but it also adds drag. Our explanation of how flaps alter lift, drag and stall speed covers the underlying aerodynamics.
| Consideration | Fuller flap setting | Reduced flap setting |
|---|---|---|
| Reference speed | Generally lower | Generally higher |
| Drag and thrust required | Higher | Lower |
| Landing distance | Often shorter because of the lower touchdown speed | Usually longer |
| Go-around climb | More flap drag can reduce climb margin | Less drag may improve climb performance |
| Typical use | Often favoured when runway distance is limiting | May suit a long runway or an aircraft-specific operational requirement |
A heavy aircraft on a short or wet runway may need the fuller permitted landing configuration to keep speed and stopping distance manageable. Another combination could be climb-limited, however, making reduced flap preferable or requiring a lower landing weight. The 737 Flaps 30-versus-40 performance comparison shows how this trade-off works on a specific airliner.
Do not adopt reduced flap merely because the wind is strong. Crosswind recommendations and flap restrictions differ by aircraft, operator and system status; the approved procedure controls.
How are landing weight, flap setting and VAPP calculated?
- Establish the predicted landing weight. Use the expected aircraft weight at touchdown, not take-off weight or zero-fuel weight. In a simulator, confirm that the flight-management system and performance tool contain the same payload, fuel and units.
- Check the landing limits. Compare the prediction with maximum landing weight and any lower performance-limited weight. Extra flap or extra speed does not make an overweight landing structurally acceptable.
- Enter the runway conditions. Account for runway length, slope, wind, pressure altitude, temperature, dry or contaminated surface, braking action and relevant system failures.
- Compare authorised configurations. Use the aircraft's approved performance data to find which flap settings meet both landing-distance and missed-approach climb requirements.
- Obtain the configuration speed. Read VREF or VLS for the actual landing weight and selected flap setting. Changing either variable requires a new speed.
- Apply the specified approach correction. Add only the wind or other correction required by that aircraft's procedure. Some systems calculate VAPP automatically, so adding the same correction again produces an unnecessarily fast approach.
- Cross-check before final approach. Verify landing weight, flap selection, speed bug and displayed VAPP against the final performance calculation.
Airbus logic is a useful example: predicted landing weight and configuration affect VLS, while the approach correction produces VAPP. Our A320 simulator speed examples show the result without treating one typical speed as valid for every flight.
What changes for light aircraft?
Many light-aircraft handbooks publish a recommended approach speed based on maximum gross weight rather than providing a speed for every possible landing weight. Although the actual stall speed falls as the aircraft becomes lighter, pilots should not reduce the published approach speed using the square-root formula unless the handbook provides an approved weight correction.
Flap choice may instead be prescribed for a normal, short-field, no-flap or crosswind landing. Loading still affects the aerodynamics, but the handbook procedure takes priority over an improvised calculation.
What mistakes cause incorrect landing speeds?
- Using stale weight data: holding, diversions and fuel burn can move the aircraft into a different weight band.
- Mixing kilograms and pounds: this can produce a plausible-looking but seriously incorrect result.
- Reading the speed for the wrong flap setting: a reduced-flap VREF used with full flap, or the reverse, breaks the performance calculation.
- Confusing IAS with groundspeed: approach references are normally indicated airspeeds; wind changes groundspeed and may also require a defined additive.
- Adding wind twice: an FMS or add-on may already have incorporated the correction into VAPP.
- Assuming extra speed is always safer: excess speed increases kinetic energy, float and stopping distance. A stabilised approach at the calculated speed is safer than carrying an arbitrary margin.
What if landing weight changes during descent?
Recalculate the landing data whenever a meaningful weight, runway, weather or configuration change occurs. Modern systems may update VLS or VAPP as fuel burns, but the crew still verifies the final flap and speed combination.
Once established on final, do not chase minor one-knot changes. If a late recalculation leaves the aircraft outside stabilised-approach criteria or invalidates the landing-distance assessment, the correct response is a go-around rather than forcing the landing.