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 altitude above the runway when four things are simultaneously true:
- You’re on the right glide path — flight-path angle within ±1° of the standard 3°.
- You’re at the right speed — IAS within tight tolerance of Vref (or ±10 kt of your approach average, depending on the aircraft).
- You’re descending at a sane rate — vertical speed within ±200 fpm of the approach average; for jets, typically not exceeding 1,000 fpm sustained.
- You’re not maneuvering aggressively — bank angle under 5° (small corrections only, no big banks below 1,000 ft).
If you can tick all four boxes at the gate altitude, 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 (~ 580 m) forward across the ground. At a 140-kt approach speed that’s a 740-fpm descent rate.
“On glideslope” doesn’t mean centered on the ILS needle exactly — it means within a tight band of the ideal angle. Real airline SOPs typically allow ±1 dot of glideslope deviation in the last segment. FLARE uses ±1° of flight-path angle, which is roughly the same window: about 30 ft above or below the ideal trajectory at the 1,000-ft gate.
For GA and tailwheel aircraft FLARE relaxes this to ±1.5° because those aircraft often fly steeper approaches (a Cub on short final might be at 5°+, and that’s normal).
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 based on weight, flap setting, and conditions.
Real airline FOMs typically allow Vref + 5 / -5 kt, sometimes +10 kt with gusts. FLARE’s universal-aircraft fallback uses ±10% of Vref (or ±10 kt, whichever is larger) — slightly looser, because in a sim we don’t always have precise weight data and the small Cessnas in MSFS sometimes have wildly different “Vref” values across mods. For cataloged aircraft, FLARE uses the published per-aircraft tolerance.
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 bleeds 600+ feet of float distance, eats stopping distance, and increases the chance of a tail strike 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. FLARE checks that your vertical speed at the gate is within ±200 fpm of the running approach average from 1,000 to 500 ft.
Why a running average? Because what matters is that you’re not chasing the glidepath with big pitch corrections. 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, not in a stable energy state, and you’ll likely flare with momentum you didn’t plan for.
What “bank under control” really means
Bank angle limits below 1,000 ft are about energy management and obstacle clearance. Banking 30° to overshoot the centerline at 800 ft might feel like a recovery, but in reality you’ve added load factor (which stalls you closer to the stall speed at your current weight), 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 state every frame (30–60 Hz, depending on MSFS performance) from short final through touchdown. As you descend through 500 ft AGL and again at 300 ft AGL — the two gates that match the airline VMC standard plus an inner final-commitment check — FLARE evaluates all four criteria in parallel.
Both gates must pass all four criteria for a “stable” score of 100. Hit only the 300-ft gate and your stability score drops to 70. Miss both and you score 0 on this criterion.
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 a strong predictor. A landing that scored well on stability also scored well on most other criteria, because a stable approach naturally produces 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 FLARE sees in the data:
- 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: failed speed criterion at both gates.
- Glideslope chasing — repeatedly correcting back to glideslope with 500–800 fpm vertical-speed swings. Result: failed stable-descent-rate criterion.
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 ops 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. If you want to see your own approach stability per landing, it shows up in the Score breakdown panel on every landing detail page in the portal.