How ACARS measures your flight

What the numbers on your PIREP mean and where they come from, so you know what counts.

Flight phases

ACARS follows the flight from the gate: boarding, pushback, taxi, take-off, climb, cruise, descent, approach, landing, taxi-in and arrival at the gate.

A phase changes only once the aircraft has been in it for a few seconds, so a gust or a quick pitch change doesn't flip it back and forth.
The cruise starts when you hold a level for about a minute. A level you pass through while climbing isn't counted.
Once you start the descent for real, the flight stays in descent: a short level-off on the way down isn't a new cruise.

Landing rate and G-force

The landing rate is your vertical speed at the moment the wheels touch, taken from the simulator's own touchdown value where it gives one, otherwise from the samples just before touchdown.
G-force is read many times a second around touchdown, so a short spike isn't missed.
Touchdowns within 10 seconds of each other count as one landing with bounces.
The G-force on the PIREP is that of the first contact. A bounce's G shows on its own row in the touchdown list.
The counted touchdown is your last landing. Staff can count another one (for example the real landing, not a bounce). The landing rate, G-force, landing grade and passenger reviews then follow that touchdown and the PIREP is re-scored; the bounce count and the list of touchdowns stay.
If the touchdown falls in a gap in the data (the simulator or the connection stalled at that moment), ACARS doesn't guess a rate. The PIREP shows the landing as not seen by ACARS: no rate is scored, it gets no passenger reviews, it isn't in your landing average, and staff take a look.
A landing rate you type in yourself (on a manual PIREP or a claim) shows as typed in, not graded. It earns no landing points or passenger reviews and isn't in your landing average.

Fuel and times

Fuel used is measured from the start of the take-off roll to touchdown, so fuel burnt at the gate and on the ground doesn't count against you. The same figure is used for the finances and for the comparison with your SimBrief plan.
That comparison uses the plan's trip fuel (the burn from take-off to landing), so it's like for like. A plan without a trip fuel figure is compared with its ramp fuel less landing fuel, and the PIREP says "planned burn" instead of "planned trip fuel".
Block time runs from off-block to on-block. Taxi-out, air time and taxi-in are shown separately.
Flight facts (ACARS 2.8.63 and later): the PIREP also lists the fuel burnt in each part of the flight (taxi out, take-off and climb, cruise, descent and approach, taxi in), the highest altitude, IAS, climb and descent rates, the G in the air, the steepest bank, the lowest fuel and the wind at take-off. Fuel loaded on the way isn't counted as burnt. The wind is the simulator's wind at the aircraft, not the tower's report.
Flight data (ACARS 2.8.65 and later): the PIREP also shows your time at night and in IMC (in cloud or under 5 km of visibility), the share of the flight on autopilot, the cruise's averages (level, TAS, Mach, outside air temperature), the highest TAS and Mach, the coldest outside air, the hottest EGT, any ice, the cabin's altitude, the take-off thrust (N1), centre of gravity, trim and weather, reverse thrust and the autobrake at landing, the height you switched the autopilot off and whether you flew the approach on the ILS. What your simulator or aircraft doesn't give shows as not read rather than a wrong figure: many airliner add-ons keep their autopilot, autobrake, weight and balance and radios to themselves. The flight log also notes the autopilot and autothrottle going on and off, the selected altitude, reverse thrust and the COM radios.
Holds (ACARS 2.8.66 and later): each hold under Flight data, with its level, how long it lasted and how many laps. A hold is all the way round at a level held, for a lap or more, at least 2,000 ft above the ground and outside a circuit. Nothing is judged.
Time paused in the air is shown on the PIREP. Your airline decides whether it counts as flight time. The average ground speed and fuel per hour leave the paused time out; when you paused for more than 10% of the time in the air, they aren't shown.
If ACARS was closed in the middle of the flight and you continued it, the PIREP says how long it wasn't tracked. That time stays in the block time, but it counts as paused: it is taken off your credited hours (and so off the hours for ranks, points per hour and pay), whatever your airline's rule for pauses. Flights filed before 3 October 2026 keep the hours they got. This needs ACARS 2.8.26 or newer; older versions don't report the gap.

The approach and the runway

With the runway data installed, the PIREP shows:

Glide slope: your height against a 3° path to the runway you landed on, from 10 nm to about 200 ft, in dots as on an ILS (one dot is about 0.35°). Heights above the ground are measured from the wheels, not the middle of the aircraft.
Lined up: how far left or right of the extended centreline you were over the last 10 nm.
Stable approach gates: speed, vertical speed, gear and flaps at the heights your airline sets. From ACARS 2.8.44 they are checked only on final: within 10 nm of the runway, lined up with it, at your height above the runway (not above the ground under you), so a STAR over hills far out is no gate. From ACARS 2.8.61 a gate is also unstable when you are more than 20 kt faster than your aircraft type's usual approach speed (or than your SimBrief plan's landing VREF plus 5 kt, when the plan has landing figures); an A320's limit is about 160 kt.
Touchdown point: how far past the threshold you touched down. Good is inside the touchdown zone (up to 3,000 ft, or a third of the runway on a long runway); early is the first 500 ft, short before the threshold, long past the zone.
Runway overrun (ACARS 2.8.63 and later, with the touchdown zone rule on): the landing roll was still faster than 30 kt more than 100 ft past the end of the runway. It costs nothing unless your airline gives it points.
Displaced threshold: where a runway's landing threshold is set back from its start, the touchdown point, the percentage, the runway left and the long limit use the length available for landing, not the whole runway. The PIREP shows the displaced part and the runway diagram draws it.
Where you parked: where the flight ended (engines off). Ending on a runway, or away from every stand and apron (for example on a taxiway), can cost points when your airline uses those checks. Stands and aprons come from OpenStreetMap; at an airport where none are mapped, only the runway is judged.
Flare: how much of your sink rate at 50 ft you took off before touchdown. The grade is capped: sinking faster than 1,000 fpm at 50 ft gives at most fair (faster than 1,400, poor); a touchdown firmer than 240, 400 or 600 fpm gives at most good, fair or poor; and a bounce or a second touchdown within a minute gives at most fair. The PIREP says what held the grade down.
Approach score (ACARS flights): one figure from 0 to 100 for the final approach from 1,000 ft down to 50 ft, with a grade (Very stable, Stable, Some corrections, Unstable). It starts at 100 and loses points for gates that weren't stable, an unsteady or fast sink rate, an unsteady speed, banking more than 10° below 500 ft and being off the glide path; each part has its own cap, so one bad figure can't take it all. When ACARS 2.8.65 read an ILS on NAV1, the glide path is judged more closely than on a visual approach. It doesn't change your points.
Take-off: the runway, how far along it you lifted off, and your climb over the first minutes. The distance is from the start of the runway when the runway data knows where the runway starts, otherwise from the threshold. A lift-off beyond the far end shows as "past the runway end", and a figure worked out from positions far apart is marked "about".

Detailed flight analysis

If your airline has turned on Detailed flight analysis, your PIREP page shows more of the flight: every touchdown, the fuel at the gate, at take-off, at landing and at the arrival gate, the taxi and air times, a vertical profile of your altitude along the route, and how far you strayed from the planned route. The route comparison needs a planned route on the booking (the route or your SimBrief plan).

New airlines start with it on. Staff switch it on or off under Staff → Airline settings → Optional features, in the Flight analysis group.

Flight checks

ACARS watches for handling faults (stall warning, overspeed, taxiing too fast...), procedures (beacon, lights, parking brake...) and integrity.

A check your simulator or aircraft can't report is shown as not reported and never counts against you.
A check your airline set to 0 points and no review is only logged: the PIREP shows it as "logged, no points", and it doesn't take away the clean-flight bonus.
The tail strike check uses each type's own pitch limit: 11° by default, lower for long-bodied types such as the A321, 737-900, 757-300, 777-300 and A340-600. For the A320 and A321 (and their neo versions) it uses Airbus's figures: in the take-off rotation, when the main gear struts are extended, 13.5° and 11.2°; at the touchdown and on the landing roll, with the struts compressed, 11.7° and 9.7°. For the 737-900, 757-300, 777-300 and A340-600 only the struts-compressed limit is known, which every normal rotation passes, so their take-off roll is not checked; their touchdown and landing roll are.
Some add-on aircraft don't report their switches through the simulator's standard values. An aircraft profile tells ACARS which switches work and what the flap lever positions are called. If your aircraft has none, ACARS offers to record one after the flight (Teach Vaeroly this aircraft); Vaeroly checks it before every copy of ACARS uses it.
Some airlines judge the lights and switches only for aircraft with a verified profile. The PIREP then says whether they were judged.
The beacon isn't judged on aircraft without a separate beacon, where the strobes are the anti-collision light or one switch works both (for example the Diamond DA40, DA42 and DA62, the Cirrus SR22 and Vision Jet, the TBM 930), nor on a few add-ons whose beacon the simulator doesn't report.
The same goes for other readings an aircraft doesn't have or doesn't report: no flap check on aircraft without flaps (the Piper Cub, Extra, Pitts, gliders), no light, pitot heat or transponder checks on aircraft with no electrics (the Cub, gliders), and no light checks on add-ons that keep their lights to themselves (several X-Plane airliners, some P3D Airbus, the iFly 737 MAX's landing lights and strobes). A transponder the simulator reports in its ground mode isn't judged at take-off.
From ACARS 2.8.63: Touchdown too fast for the type (more than 25 kt over the type's usual approach speed, or over your SimBrief plan's landing VREF plus 5 kt; types without a known approach speed aren't judged) and Speed brakes out below 1,000 ft (out for 3 seconds or more on the approach below 1,000 ft above the runway; not on the BAe 146 and gliders, which fly the approach with them out, nor on aircraft that don't report the lever). Both start at 0 points: they are logged until your airline gives them points.
From ACARS 2.8.65: Ice with the anti-ice off (ice on a tenth or more of the airframe for 30 seconds in flight with the engine and wing anti-ice off), Cabin climbing too fast (the cabin altitude climbing faster than 2,000 fpm for 10 seconds in flight: pressurisation off or failing) and Door open while moving (a door open for 3 seconds or more while taxiing faster than 5 kt or in flight). They start at 0 points. Aircraft that keep their anti-ice and pressurisation to themselves (most airliner add-ons), aircraft without a pressurisation model and aircraft whose doors the simulator doesn't report aren't judged.
Time acceleration is logged each time you change it. It sends the flight to staff to look at; it costs no points. Some airlines allow a short burst.
The crew centre also runs its own integrity checks on every PIREP. We don't publish how they work.

For what each check costs at your airline, open your airline's Scoring rules page. What happens to a PIREP after it's filed is in What the PIREP statuses mean.