If you fly long enough (in a sim or in a real cockpit) you’ll hear “stabilized approach” said about a thousand times. The phrase has a specific, well-defined meaning, and it shows up in real airline SOPs as a hard go-around criterion. This post walks through what it actually is, where the rule comes from, and how FLARE measures it from MSFS telemetry.
The short version
An approach is “stabilized” at a given height above the runway when four things are true at once:
- You’re on the right flight path: on the glideslope, or on a steady path of about 3° to the runway.
- You’re at the right speed: no faster than Vref + 20 kt and no slower than Vref, and not wandering.
- You’re descending at a sane rate: for jets, typically no more than 1,000 fpm.
- You’re not maneuvering aggressively: only small heading and pitch corrections, wings close to level.
Airline versions add a few housekeeping items (landing configuration set, power appropriate, briefings done), but those four are the heart of it. If you can tick all four boxes at the gate, you’re stabilized. If even one is missed, you’re not.
Where the rule comes from
The stabilized-approach concept dates back to the 1970s, when accident investigators noticed that runway excursions and undershoot accidents almost always traced back to an unstable final segment. The Flight Safety Foundation’s Approach-and-Landing Accident Reduction (ALAR) task force formalized the rule in the late 1990s. Most major operators adopted it as a hard go-around criterion shortly after.
The standard you’ll see in airline FOMs (Flight Operations Manuals):
- By 1,000 ft AGL in IMC: the aircraft must be stabilized. If it isn’t, go around.
- By 500 ft AGL in VMC: the aircraft must be stabilized. If it isn’t, go around.
That’s it. There’s no “almost stable”, no “stable enough”, no “I think we can save it.” The cost of a missed approach is fuel and 8 minutes of flying. The cost of pushing an unstable approach to landing has, historically, been measured in lives.
What “on glideslope” really means
The standard glideslope is 3° below horizontal, about a 5% gradient. For every 100 ft of descent, you’re moving 1,900 ft (about 580 m) forward across the ground. At a 140-kt groundspeed that’s a 740-fpm descent rate.
“On glideslope” doesn’t mean exactly centered on the ILS needle; it means within a tight band of the ideal path. Real airline SOPs typically allow about one dot of glideslope deviation in the last segment. FLARE measures your actual flight-path angle instead, and when you’re following a published vertical path (an ILS glideslope, or an RNAV approach in its final approach mode) it checks you were within ±1.5° of 3°.
On a visual approach there’s no published path to follow, and 3° is a convention rather than your target, so FLARE doesn’t hold you to it. It checks that the path you flew was steady: within ±2° of the one you’d established, plus a 1,500 fpm limit so a uniformly steep dive is still caught. A Cub on a steep 5° final is fine as long as it’s a steady 5°.
What “on speed” really means
Vref is your reference landing speed: the speed at which the aircraft, in landing configuration, is flying at 1.3 times its stall speed. It’s calculated per landing from weight, flap setting and conditions.
Real airline FOMs typically allow Vref + 5 / −5 kt, sometimes more with gusts. At the stability gates FLARE asks a slightly different question: did your speed stay steady? It compares your speed at each gate with what you flew over the previous 300 ft, with a tolerance set by the aircraft’s category (7% of Vref for most airliners, 8% for light singles, never less than 10 kt). Whether you were fast or slow is reported separately, and the Coach tells you, against a Vref adjusted for the weight you landed at.
The most common failure mode here isn’t being slow (you’d feel that, and the aircraft would warn you); it’s being fast. Carrying 20 extra knots into the flare can add 600 ft or more of float, eats stopping distance, and makes a tail strike more likely if you over-rotate trying to slow down with pitch.
What “stable rate of descent” really means
This one’s subtle. It doesn’t mean “exactly 700 fpm” or any specific value; it means consistent. A descent that wanders between −400 and −1,200 fpm in the final segment is unstable even if every individual value is within reasonable limits, because the corrections themselves are big and reactive. They tell you you’re not in trim or in a stable energy state, and you’ll likely flare with momentum you didn’t plan for.
FLARE judges this through the flight-path check above: a wandering descent rate shows up as a wandering path. (It used to compare your descent rate at each gate with your average since 1,000 ft, but a descent rate should change as you slow down and configure, so that check was retired in favor of the geometric one.)
What “bank under control” really means
Bank angle limits below 1,000 ft are about energy management and obstacle clearance. Banking 30° to correct back to the centerline at 800 ft might feel like a recovery, but in reality you’ve added load factor (which raises your stall speed), lost altitude in the turn, and probably overshot in the opposite direction. The 5° limit is a hard “no big corrections” rule: anything that needs more bank than that is a go-around.
How FLARE measures it
FLARE samples your flight 50 times a second from 1,000 ft AGL through the landing. As you descend through 500 ft AGL and again at 300 ft AGL (the airline VMC gate plus an inner final-commitment check) it evaluates three checks at each gate: steady speed, bank under 5° and the right path. It uses the median over the last stretch of descent, so a single bump doesn’t fail you.
Both gates stable scores 100. Stable at 500 ft but not at 300 ft scores 70; stable only at 300 ft scores 50; neither scores 30. If FLARE never saw a gate (you started on short final), it scores you from the gate it did see instead of counting it against you.
Approach stability is weighted 10% of the composite score, less than descent rate or G-force because the touchdown moment matters more. But it’s upstream of everything else: a stable approach tends to produce a controlled flare and a centered touchdown. The two are linked in the cockpit, and they’re linked in your FLARE grade.
What this means for your sim flying
Most sim pilots fly unstable approaches without realizing it. The two most common patterns:
- Late configuration: flaps extended below 500 ft, gear coming down at 300 ft. The aircraft is decelerating and re-trimming through the gates instead of settling into a steady state. Result: a failed speed check at both gates.
- Glideslope chasing: repeatedly correcting back to the glideslope with 500–800 fpm vertical-speed swings. Result: a failed path check.
The fix in both cases: be configured by 1,500 ft AGL. Flaps set, gear down, speed bleeding to Vref smoothly, trimmed. The last 1,000 ft should be small inputs only.
If you can’t get stable by 1,000 ft, the answer in real operations is to go around. FLARE won’t penalize you for going around: it scores the landing you actually make. A go-around followed by a stable approach beats a forced landing every time.
The composite scoring engine is documented in detail in our methodology post. Your approach stability for every landing is in the Score breakdown on the landing page in the portal, and the Coach cards in the desktop app point out an approach that wasn’t stable.