Why Final Approach Speed Is Set at Exactly 1.3 Times Stall Speed

FAA guidance establishes that, absent specific manufacturer performance data, pilots should fly final approach at 1.3 times the stall speed in landing configuration — known as 1.3 Vso — providing a 30% margin above aerodynamic stall speed. The FAA also recommends flying the base leg of the traffic pattern at 1.4 Vso before reducing to 1.3 Vso on final.

Applied to a Cessna 172, with a full-flap stall speed (Vso) of 40 knots, the formula produces a base leg target of 56 knots and a final approach target of 52 knots. For a Cirrus SR22, with a Vso of 64 knots, the same multipliers yield a base speed of 90 knots and a final approach target of 83 knots, closely matching the manufacturer's recommended 80–85 knots.

These baseline targets are calculated at maximum certificated landing weight. When an aircraft lands below that weight, its stall speed drops because the wings need less lift, and flight safety guidance recommends decreasing the gross-weight target speed by 5% for each 10% reduction in actual gross weight — a ratio derived from the principle that stall speed varies with the square root of aircraft weight.

For transport-category aircraft certified under FAA 14 CFR Part 25 and EASA CS-25, the concept is formalized as Reference Landing Speed (Vref), using a 1-g stall speed (Vs1g) rather than conventional Vso, with regulations requiring Vref to be established at no less than 1.23 Vs1g. On aircraft such as the Airbus A320neo or Boeing 737 MAX 8, the flight management computer calculates Vref dynamically from actual landing weight. Airline standard operating procedures add a further buffer to produce Vapp: a minimum of five knots above Vref plus half the steady headwind component plus the full gust increment above that, capped at 15–20 knots. An airliner with a Vref of 135 knots flying into a ten-knot headwind gusting to 20 knots would target a Vapp of 150 knots.

On higher-performance aircraft, pilots also guard against the region of reversed command — the aerodynamic state below the minimum drag point where flying slower requires more power to maintain a stable descent. Pilots of aircraft such as a Cirrus SR22 or a Piper Seminole (PA-44-180) typically carry a five-to-ten-knot buffer above 1.3 Vso to stay clear of it.

Letting speed decay from a target 83 knots toward 70 knots sharply increases induced drag, causing descent rate to rise; attempting to arrest the sink without adding throttle can escalate toward a stall. Large high-bypass turbofan engines compound the risk on transport aircraft, since they can require five to eight seconds to spool from flight idle to full go-around thrust — part of why Vapp builds in its own margin on top of Vref.

The consistency across aircraft classes is the point: whether the reference is Vso for a piston single or Vs1g for a swept-wing transport jet, the underlying rule is the same 1.23-to-1.3 multiplier over stall speed, adjusted for how each airframe and engine type behaves near the edge of the envelope. That uniformity is what lets flight training, manufacturer performance charts and airline SOPs all speak the same aerodynamic language even though the numbers on the airspeed tape look nothing alike.

What differs by segment is how the margin gets layered on. General aviation pilots apply a fixed multiplier and a manual weight correction; transport crews let the flight management computer calculate Vref from actual landing weight and then add a further human-specified buffer, Vapp, sized to engine spool time and wind. The extra margin on turbofan aircraft exists specifically because a five-to-eight-second spool lag leaves less room to recover from a low-energy state than a piston engine's near-instant throttle response.

Where this matters operationally is in how crews and pilots recognize and correct energy decay before it becomes a stall risk — the region of reversed command being the clearest case, where adding power rather than pitch is the only way out. Training programs and SOPs that keep reinforcing the arithmetic behind these speeds, rather than treating them as numbers to memorize, are what keeps the margin meaningful across such a wide range of aircraft types.