How Flying Works
Why Some Landings Are Hard and Some Are Smooth
On 3 May 2019, a Miami Air International Boeing 737 landed at Naval Air Station Jacksonville in a thunderstorm, carrying 143 people home from Guantánamo Bay. It touched down roughly 1,600 feet past the landing threshold, in heavy rain, on a runway with no grooves cut into it to drain water away. The tyres hydroplaned, unable to grip through the film of water building up under them, and the aircraft slid off the end of the runway into the St. Johns River. Everyone survived. The NTSB blamed an extreme loss of braking grip from heavy rain on the ungrooved runway. It also found the crew had flown an unstable approach, landed fast and been slow to deploy the speedbrakes, but concluded the jet could not have stopped on that runway even without those errors. It’s a sobering reminder of how thin the margin gets on a wet runway. On a wet or short runway, the long, gentle, barely-felt touchdown people read as skill is often the more dangerous choice.
Why firm is sometimes exactly right
Runway margin disappears faster than passengers tend to think. On a wet or contaminated surface, braking can be much weaker. A soft, floating touchdown that uses several hundred extra feet of runway before the wheels are firmly down is a real problem on a short, wet or sloping runway. Flight 293 shows how little margin a wet runway leaves. A firm arrival puts weight on the main wheels straight away. That’s the trigger that lets the spoilers deploy, the brakes bite and reverse thrust work, and a gentle float delays all of it. Wet runways without grooves add another risk: hydroplaning, where the tyres ride on water instead of gripping. A firm touchdown helps by getting the tyres spinning and gripping sooner.
Animated
Greaser, firm or hard: what happens at touchdown
Firm (on purpose) (about 4 ft/s downward at touchdown): A positive touchdown. On a wet or short runway this is the correct technique: the tyres push through the water and the brakes start working sooner. For scale, airliner landing gear must be designed to take 10 ft/s at maximum landing weight. Values are illustrative.
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Where “hard” officially starts
Passengers judge a landing by feel. Engineers use two numbers.
The first is sink rate, how fast the aircraft is coming down at touchdown. Boeing designs its airliners to absorb 10 feet per second, about 600 feet per minute, at or below maximum landing weight. The second is the g-load at touchdown: how hard the gear is pushed, measured against normal gravity. At 1g you feel your ordinary weight. A typical hard-landing threshold is around 2.6g, so for an instant the structure carries more than two and a half times its usual load.
A “firm” landing on a wet runway is normally well under both. It feels solid because the gear compresses quickly, not because anything was close to a limit.
If a landing does exceed a threshold, the aircraft’s recorders flag it and a hard-landing inspection is mandatory before the next flight. Many manufacturers also set lower cautionary triggers, so engineers can look at gear and structure before a problem has any chance to build.
Overweight landings, for example after an early return, use a tighter limit: roughly 360 feet per minute, or 1.7g.
What repeated hard landings actually cost
That doesn’t mean landing hard is free. Modern airliners record the vertical acceleration at touchdown. A landing harder than a set limit automatically triggers an inspection of the airframe and landing gear before the next flight. That costs real time and money, even when nothing is wrong. So “smooth” isn’t just about passenger comfort, but it isn’t a safety benchmark either. The aircraft manual itself says a firm landing is the intended, correct technique in certain conditions, not something merely tolerated.
Sources & Further Reading
Common Questions
Frequently Asked Questions
So a hard landing isn't a sign of a bad pilot?
Not automatically, and it can be the opposite. On a wet, contaminated or short runway, a firm, positive touchdown is the correct technique, and sometimes the one the manual requires. A smooth, floating landing that uses up extra runway is the riskier choice there, even though it feels nicer.
Why does a firm landing help on a wet runway?
Water, snow or ice on the runway can sharply cut braking and raise the risk of hydroplaning, where the tyres ride on a film of water instead of gripping. A firm touchdown puts weight on the wheels straight away, and that’s what lets the brakes, spoilers and reverse thrust start working. A soft float delays all of that, and every extra metre used before touchdown is a metre less to stop in.
Does the aircraft record how hard a landing was?
Yes. Modern airliners record landing data, including the vertical acceleration at touchdown. A landing harder than a set limit automatically triggers an inspection of the airframe and landing gear before the aircraft flies again.
Why do some landings feel smooth even in a crosswind?
Crosswind technique often produces a firmer, more controlled touchdown on purpose. Pilots put getting the aircraft firmly on the centreline and under control ahead of a gentle arrival. In gusty crosswinds, a “greased” landing can mean the aircraft floated further off-centre than is safe.
Last reviewed: October 2026. Facts that change, such as fleets, airspace and airline ownership, are re-checked on a schedule. Spotted an error? Email contact@skyplus.news and we’ll fix it. See how we check facts.