Takeoff Performance
Monitoring

01 — THE PERFORMANCE CONTRACT

One result, many connected assumptions

Takeoff performance may be understood as an operational relationship among the aircraft, the crew and the conditions that actually exist. The assessment is based on defined assumptions that may include aircraft weight and center of gravity, runway and declared distances, takeoff position, surface condition, slope, environmental conditions, configuration, thrust or power setting and obstacle environment.

The calculated speeds, thrust setting and required distances are not independent values. They are connected outputs generated from the same assumptions. If the runway changes, the original calculation may no longer apply. If an intersection departure is accepted, the available distance and takeoff position must correspond to that departure. If actual takeoff weight differs materially from the weight entered into the approved performance system, the outputs may not represent the aircraft about to depart.

The same principle applies to configuration. A calculation based on one flap setting cannot be separated from that setting. A reduced-thrust or assumed-temperature calculation depends on the assumptions and limitations used to generate it. Runway condition, wind and environmental parameters cannot be changed without determining whether the previous result remains valid under applicable procedures.

A mathematically correct value used in the wrong operational context may be as hazardous as an incorrect value. Takeoff performance is a connected operational model that must remain aligned with the aircraft, runway, takeoff position and conditions throughout preparation and takeoff initiation.

02 — HOW THE CHAIN CAN BREAK

Agreement does not always prove validity

The modern performance process contains several information sources and interfaces. Data may originate in load control, dispatch documentation, aerodrome information, NOTAMs, meteorological reports and the operator’s approved performance system. It may then be transferred into an EFB, performance application, FMS or another aircraft system. Every transfer provides an opportunity for verification, but may also introduce error.

An incorrect takeoff weight may originate in the load sheet, remain from a previous sector or result from confusion between zero fuel weight and takeoff weight. A runway change may occur after the original calculation. An intersection may be accepted without recalculation for the revised distance. An assumed-temperature or derate value may be entered incorrectly. V-speeds may be transposed, retained from an earlier calculation or entered accurately from a calculation based on incorrect information.

EASA Safety Information Bulletin 2016-02R1 identifies examples involving incorrect mass, center-of-gravity data, V-speeds, thrust parameters, runway information, configuration and operational changes that were not incorporated into the performance assessment. The bulletin provides safety information and recommendations; it is not a mandatory operational instruction.

Cross-checking is essential, but its quality determines what it can detect. Confirming that the FMS value is identical to the EFB value establishes that both systems contain the same number. It does not necessarily establish that the value represents the correct weight, runway, intersection, weather condition or configuration.

Operator procedures determine how these questions are addressed. NFA does not introduce an alternative verification procedure. Its educational role is to explain why a complete-looking check may still fail when it verifies agreement without verifying operational meaning.

03 — ACHIEVED PERFORMANCE

When the aircraft begins to reveal the error

Once thrust is applied, the aircraft begins to produce actual performance. The planned model is no longer only a calculation; it is being compared, implicitly or explicitly, with physical acceleration.

Flight crews have historically had limited means of objectively comparing achieved and planned performance during the roll. A large aircraft may appear to accelerate normally even when acceleration is lower than expected. Long runways can reduce the visual prominence of abnormal runway consumption. Darkness, reduced visibility, limited peripheral references and unfamiliar aerodromes may further weaken subjective assessment.

Experience may help recognize a gross abnormality, but human perception is not a calibrated, aircraft-specific monitoring system. Pilot perception may contribute to recognition, but cannot by itself provide the modeling, quantitative comparison or repeatability that may be available from a certified or approved function.

The aircraft may nevertheless present indications requiring attention under applicable procedures: a thrust setting that does not agree with the briefing or indications, unexpected configuration, abnormal engine indications, speeds developing differently from expectation, unusual runway consumption or an aircraft response inconsistent with the crew’s mental model.

Planned and achieved performance do not automatically remain consistent simply because the takeoff has begun.

These observations must not be converted into unofficial universal checkpoints. A particular speed by a taxiway, a visual halfway point or an improvised elapsed-time check cannot be generalized without an approved technical basis.

04 — INVESTIGATION EVIDENCE

How an error can survive the system

Melbourne — Airbus A340-541, A6-ERG

On 20 March 2009, an Airbus A340-541 registered A6-ERG commenced a reduced-thrust takeoff from runway 16 at Melbourne Airport. A takeoff weight approximately 100 tonnes below the actual takeoff weight had inadvertently been used in the performance calculation. The resulting thrust setting and reference speeds were lower than required for the aircraft’s actual weight.

The aircraft did not become airborne as expected after rotation was initiated. It sustained a tail strike, overran the runway end and damaged aerodrome infrastructure. After additional thrust was selected, the aircraft became airborne and subsequently returned to Melbourne. No injuries were reported.

The ATSB found that the erroneous data and its effect on performance planning passed through subsequent checks without detection. Multiple people interacted with the information, several operational steps were completed and the takeoff proceeded. The error survived the system.

The ATSB global study

The ATSB report Take-off Performance Calculation and Entry Errors: A Global Perspective, AR-2009-052, documented 20 international and 11 Australian occurrences identified between 1 January 1989 and 30 June 2009. The study found different combinations of incorrect figures, data entered incorrectly, information not updated, omitted data, inadequate risk controls, time pressure, distraction, task-experience limitations, training and crew-management factors.

There was no single error path and therefore no single solution capable of preventing or detecting every occurrence.

Paris Charles de Gaulle — Boeing 737-800, SU-BPZ

On 16 August 2008, a Boeing 737-800 registered SU-BPZ departed Paris Charles de Gaulle Airport at night from runway 27L, entering from intersection Y11. The available runway length had been temporarily reduced because of construction work.

The reduction—approximately one-third of the runway length—was not incorporated into the takeoff-performance assessment. During the takeoff, the aircraft struck temporary runway-end lights and markers protecting the construction area before becoming airborne and continuing to its destination. The BEA investigation led to safety recommendations concerning the certification and operational use of onboard performance-calculation systems.

The event demonstrated that a computerized tool may produce internally correct results while operating from an incorrect runway assumption. Verifying the transfer of its output does not establish that the operational context entered into the tool was correct.

These occurrences should not be reduced to statements that crews should simply have noticed. More useful questions examine how information entered the process, why barriers failed, when a mismatch could reasonably have been recognized and which defenses could reduce recurrence.

05 — TOPMS

A proposed additional detection barrier

A Take-Off Performance Monitoring System is intended to provide an additional detection barrier against certain unsafe takeoff conditions. It is not a universally installed function, and the term must not be treated as describing one standardized capability across all aircraft, operators or jurisdictions.

On 1 July 2025, EASA published NPA 2025-01, Take-off Performance Parameters and Position Errors — Large Aeroplanes. The consultation period closed on 3 October 2025.

The proposal describes three complementary functions:

The proposal would require F1 and F2 for new large-aeroplane designs. F3 would additionally apply to the category defined in the proposal as large transport aeroplanes. For that purpose, the NPA uses an MTOM threshold of at least 35 tonnes together with passenger or cargo criteria, while excluding regional turboprops and most business jets from the F3 scope.

For certain already approved designs, the proposal also envisages future production applicability through Part-26 for aircraft operated in commercial air transport. These provisions remain proposed and depend on the final regulatory process, adopted text and effective dates.

The three functions address different failure paths. A parameter-consistency check may identify an impossible value but fail to identify a plausible value belonging to another weight or runway. Position monitoring may confirm that the aircraft is on the expected runway while remaining unable, by itself, to establish that selected thrust is adequate. Real-time performance monitoring begins only after the aircraft starts moving and consuming runway.

A certified system would operate within a defined design and certification envelope. It must not be assumed to evaluate every surface condition, environmental uncertainty, aircraft state or operational scenario. Any alert must be interpreted through certified system logic and approved operator procedures.

Where installed, certified and applicable to the existing conditions, TOPMS may provide an additional detection barrier within the limits of its approved capability.

06 — V1 AND THE DECISION ENVIRONMENT

Credibility must be established before speed removes options

V1 belongs to a certified and operational takeoff-performance framework. Its meaning cannot be reduced to a generic statement that it is simply the speed at which the aircraft must continue. Its exact definition and operational use must come from the applicable certification basis, aircraft documentation and operator procedures.

V1 should not become the first moment at which performance credibility is considered. Data integrity, configuration and runway-position defenses should be addressed before takeoff. The purpose of an approved monitoring function is to support earlier detection where its certified capability permits; it is not to create an improvised high-speed decision technique.

NFA does not establish independent rejected-takeoff criteria. Applicable callouts and crew response to any alert remain governed by aircraft certification, installed-system logic and approved operator procedures.

As the aircraft accelerates, the decision environment becomes progressively less tolerant of uncertainty, delayed recognition and incomplete communication.

07 — OPERATIONAL APPLICATION

Protecting the model throughout the departure sequence

Before takeoff

The crew establishes a shared and current operational model incorporating aircraft weight and center of gravity, runway and departure direction, takeoff position and available distances, runway and environmental conditions, aircraft configuration, thrust or power plan and the resulting performance outputs.

The objective is not merely to complete individual entries. It is to ensure that the entries describe the same intended takeoff.

After a late change

A change involving runway, intersection, weather, load, configuration or another operational assumption may invalidate part or all of the previous assessment. The professional question is not whether the numerical change appears small, but whether an assumption supporting the original calculation has changed.

Recalculation, re-entry, re-verification and any required briefing must follow the approved operator procedure.

During takeoff initiation and acceleration

The crew monitors the aircraft using the indications, callouts and procedures approved for the aircraft and operation. Any installed monitoring system must be interpreted through its certified logic and the operator’s approved response. Subjective impressions or visual runway references must not be converted into unofficial universal decision points.

After an anomaly

Unexpected acceleration, abnormal runway consumption, data discrepancies, position errors or calculation-tool difficulties may provide valuable safety information. Reporting and flight-data-monitoring processes can identify hazards that may not be visible from one flight alone.

08 — PROFESSIONAL COMPETENCY

Technology, procedures and TEM as layered defenses

Takeoff-performance assurance is a system competency involving dispatch, load control, aerodrome information, performance software, flight-crew procedures, aircraft systems, training, reporting and safety monitoring.

This connects directly with Threat and Error Management. A threat may be a late runway change, short turnaround, complex intersection, disrupted calculation, changed runway condition or incomplete information. An error may involve weight, runway, configuration, thrust, weather or data entry. The undesired aircraft state may be a takeoff using performance different from the model understood by the crew.

Effective TEM does not depend on predicting one particular mistake. It depends on complementary barriers capable of detecting different paths toward the same unsafe condition.

Technology, procedures, cross-verification and professional monitoring do not compete. They form layers of defense.

The runway is a finite operational resource continuously consumed during takeoff. Before thrust application, the crew retains time to question, calculate, compare and correct. Once the roll begins, that time contracts rapidly.

A calculation must be understood, not merely copied. A cross-check must examine meaning, not merely agreement. A takeoff must be monitored as an evolving flight-path event, not assumed to be safe because thrust has already been applied.