Landing performance

Landing distance is from crossing the 50-ft (15 m) screen height to full stop.

Factors that increase landing distance

Factors that decrease landing distance

• Lower mass and low DA
• Headwind (every 10 % of TAS as headwind reduces LDR by ~10 %)
• Uphill runway (gravity component decelerates)
• Dry asphalt instead of grass/wet
• Full flaps (for given type)
• Precise approach profile with correct Vref

Shortest landing — combination of factors

The shortest landing distance required is obtained with the combination of headwind and upsloping terrain:

• Headwind reduces ground speed at touchdown.
• Upslope shortens roll through gravity braking.
• Both factors act cumulatively → maximum reduction.

For short runways with wind options, the pilot picks the headwind direction onto an uphill runway.

Landing flaps — function and effect

Landing flaps serve two main purposes:

• Lower stall speed (Vs0) and thus lower approach and touchdown speed → shorter rollout.
• Higher sink rate at same speed → steeper approach without IAS rise, clear sight on threshold.

Consequence: landing with full flaps is normally standard for the shortest landing.

Spoilers on final approach

Spoilers are deployable surfaces on the wing that — when extended — reduce lift and increase drag. Common on gliders, transport aircraft, and some high-performance PPL types.

Effect on final approach when spoilers are deployed:

• Loss of lift → minimum speed (Vs) becomes higher (the pilot must fly faster to avoid stall).
• Increased drag → approach (glide) angle becomes steeper (the aircraft descends more steeply at the same speed).

→ Spoilers are an efficient way to lose altitude on a steep approach without excess IAS or exceeding flap limits.

Engine failure on approach — flaps for best glide

On engine failure during approach, to achieve the best glide angle (max L/D), the pilot must leave or bring the flaps to neutral (fully retracted):

• Flaps extended → more drag → worse glide angle → shorter glide distance.
• Flaps neutral (0°) → minimum drag → best glide angle → max glide distance.

The pilot decides: if the emergency field is in glide range with flaps 0° → fly there, deploy flaps only just before touchdown (to bring Vref back near stall reserve).

When the approach must be extended

Sometimes the pilot finds the approach is too short (e.g. ATC asks "extend downwind", or the pilot is too high and would touch down too early).

With engine power

The most efficient and least dangerous method to extend the approach is to increase engine power:

• More power → more thrust → higher TAS and longer time per leg.
• The approach lengthens, the touchdown point moves further along.

Without engine power (e.g. after engine failure)

If the pilot has no engine power (engine failure, or deliberate power-off approach), the most efficient method to extend the approach is:

• Retract flaps — reduces drag, improves glide angle.
• Retract spoilers (if deployed) — same effect.
• Adjust airspeed to best-glide speed (Vbg) — maximum glide distance.

This flattens the descent and moves the touchdown point further.

AFM corrections — safety margin

As with take-off, many AFM charts give conservative values:

• Headwind: count 50 %
• Tailwind: count 150 %

Operational practice

• Strict Vref (AFM-specific, typically 1.3 × Vs0).
• Aim point just before the threshold, stabilised approach from 500 ft AGL.
• On any deviation > 10 KIAS or > 100 ft/min from planned profile: consider go-around.

Example: asphalt vs grass

Typical Cessna 172 at MTOM with 5 kt headwind, ISA, asphalt: LDR ≈ 450 m. On dry grass: LDR ≈ 540 m. On wet grass: LDR ≈ 600 m. (Illustrative — use your AFM.)