Class A: Using Performance Data - ATPL 032 — Performance

The five take-off limits, chart by chart

The take-off analysis runs the same day through five charts, and the performance-limited take-off mass is the lowest of the five answers (with the structural maximum standing over them all). Knowing which chart tends to win is half the exam question:

Field-length-limited (FLLTOM) — enter with OAT, pressure altitude, wind, slope and flap; bites on short runways, hot and high, with tailwind or contamination.

Climb-limited — the WAT chart, blind to the runway; bites hot and high even with kilometres of concrete to spare.

Obstacle-limited — the net-flight-path check; bites where close-in obstacles stand off the departure end while field and climb are comfortable.

Tyre-speed-limited — bites hot and high with the lower flap settings, where the lift-off TAS runs closest to the tyres' rating.

Brake-energy-limited — the VMBE check; bites hot, high and heavy with tailwind or downslope, where the reject's energy peaks.

V-speeds, RTOM tables and the assumed temperature

With the mass settled, the V-speed tables turn it into V1, VR and V2: enter with the actual take-off mass, flap and thrust rating, interpolate between rows, and apply the footnote corrections for wind, slope, QNH and bleed configuration. The regulated take-off mass (RTOM) tables compress the whole analysis into one page per runway: for each flap, wind and temperature column they tabulate the maximum mass and the speeds that go with it, with correction rows for QNH and bleeds. They also hand over the flex calculation ready-made: find the highest temperature column whose tabulated mass still covers the actual mass: that temperature is the assumed temperature of the flex lesson, and the V-speeds are read in that column for the actual mass. And after a rejected take-off, the data does not let the aeroplane simply taxi back and try again: the brake cooling tables, entered with the mass and the speed at which the reject began, give the minimum cooling time before the brakes can again absorb a full stop.

Drift-down data

The drift-down graphs of the en-route lesson get read in three directions:

Forwards — mass, ISA deviation and anti-ice status go in, and the net stabilising (level-off) altitude comes out.
Backwards — start from the terrain, add the 2,000 ft clearance to the highest relevant obstacle, and read off the maximum mass whose net level-off still sits above that figure: the escape-route mass limit.
Along the path — the tables give fuel, time and distance from the cruise level, and the descent between any two levels is the difference between their rows, the same subtraction the climb tables taught.

Landing data sheets

The landing side mirrors the take-off ladder with three rungs and a footnote:

Field-length sheet — converts a landing mass into the required distance, or a given LDA backwards into a field-length-limited mass, with the 60 per cent and wet factors of the landing lesson built in.
Climb-limit sheet — the landing WAT chart, giving the approach-climb- and landing-climb-limited mass for the day's temperature and altitude.
The lowest wins — the maximum allowable landing mass is the lowest of the climb-limited mass, the field-length-limited mass and the structural maximum landing mass.
Quick-turnaround table — entered with the landing mass, it gives the brake cooling time of the previous lesson's limit.

The five take-off limits, chart by chart

Check you understood

V-speeds, RTOM tables and the assumed temperature

Drift-down data

Landing data sheets