*CAEP stands for Committee on Aviation Environmental Protection. More information availablehere

What does the colour of the dot and the number inside the dot represent?

The colour of the dot represents the performance band of an airline for a particular metric. For example, a red dot against the CDA metric means that the CDA compliance for the given airline was less than 70% of all arrivals.

Metric 1:

Quota Count (QC):

RAG thresholds:

Green: best 75% of airlines 
Red: worst 10% of airlines 
Amber: remaining airlines

Metric 2:

Chapter number:

RAG thresholds:

Green: Less than 2 (on average quieter than Ch14H)
Amber: Between 2 and 4, inclusive of 2 but less than 4
Red: greater than or equal to 4

Strategic emissions metrics

Metric 3:

NOx:

RAG thresholds:

Green: best 75%
Red: worst 10%
Amber: remaining airlines

Metric 4:

CAEP Standard (engine emission certification):

RAG thresholds:

Green: Less than 2
Amber: Between 2 and 8, inclusive of 2 but less than 8
Red: Greater than or equal to 8

Operational metrics

Metric 5:

Continuous Descent (CDA) Violations:

RAG thresholds:

Red: less than 70% compliance
Amber: 70% to 90% compliance
Green: more than 90% compliance

Metric 6:

Track Keeping:

RAG thresholds:

Red: less than 95% compliance
Amber: 95% to 100% compliance
Green: 100% ocompliance

Metric 7:

Late or early movement:

RAG thresholds:

Red: less than 95% compliance
Amber: 95% to 100% compliance
Green: 100% compliance

Metric 8:

4pc Climb Rate Violations:

RAG thresholds:

RAG is based on the ranking on 4pc climb rate metric.
Green: only for Rank #1
Red: for the remaining which are lower than Rank#1

Metric 9:

Airline engagement:

RAG thresholds:

Red: Missed all meetings
Amber: Attended some of the meetings
Green: Attended all meetings

The number inside the dot represents the position of the airline in the metric. The ranking position of an operator is driven by their relative performance against the best and worst performer in the metric. For certain metrics multiple airlines may achieve the same number of points, this means those airlines will all be ranked #1. For example in the 4% climb metric if multiple airlines have 100% compliance (e.g.no failures) they will all achieve #1.

Why can an airline have an amber status and still be high up the table?

This is due to the weighting of each metric. If an airline scores well in all operational metrics and has a number of amber scores in the strategic metrics, their score and position in the league table would be higher than an airline who scores well in the strategic metrics but has some amber ratings in the operational metrics. As previously explained, an airline will get more points for doing well in the operational metrics as they have more influence over the performance.

Why do some airlines appear with ‘short haul’ or ‘long haul’?

Heathrow has a wide variety of airline operators. An airline can use just one aircraft type (such as an Airbus A320) or it may operate a mix of aircraft types to serve it’s route network. The calculations need to consider the different operating capabilities of smaller, short haul aircraft versus larger ones on long haul services. In our programme, a ‘short haul’ aircraft is one which has a maximum take-off weight of less than 200 metric tonnes. We split single airlines when the ‘short haul’ operation is more than 20% of overall movements, but less than 80% of all flights. This is to prevent ‘masking’ of results should one part of the operation be performing very well whilst the other part may not be. This is to reflect the fact that some of the metrics in the Fly Quieter and Greener programme favour larger aircraft but in other areas it is easier to perform better with smaller aircraft.

The nine metrics

Each metric is assigned a “RAG” (Red, Amber, Green) status based on the performance bands set for that indicator as previously explained. Individual metric scores and calculations will not be published due to the sensitivity of some data.

Where the table shows amber dots, the airlines have met Heathrow’s minimum performance targets, but there is room for improvement. Green dots show they have exceeded our minimum standards but they still may not be 100% perfect. If the airline has a red or amber dot in a particular area, we use this visual indicator as a trigger to work with the airline to improve their scores for the next iteration of the table.

1. Noise quota/passenger number

This is a relative noise “efficiency” metric which scores the noise efficiency of an operator’s fleet, recognising that whilst larger aircraft may have higher average noise levels, they also carry more passengers. It is calculated by dividing the sum of quota count points (QC) for arrivals and departures by passenger numbers.

Just like all other metrics, the calculation described is divided by number of movements; this provides a balance between a QC/passenger number or QC/movement metric which will tend to overly bias long haul or short haul carriers respectively.

2. Chapter number (noise certification)

Each aircraft is required to have a noise certificate which can be used to determine its relative performance against ICAO noise standards called Chapters. This allows us to recognise “best in class” and compare performance across different fleets that airlines operate on their flights to and from Heathrow. In the first step, a ‘nominal’ Chapter number score is assigned on the basis of the certification of the aircraft associated with each individual flight, using the scoring mechanism as shown in the table below. In the second step, in order to account for the increased sensitivity of neighbouring communities to noise in the evening and night hours, a time adjustment factor is applied to the ‘nominal’ Chapter number score for flights operated in the evening period (between 19:00 and 23:00 local time) and in the night time period (between 23:00 and 07:00 local time), as explained below. Using these principles we favour airlines that operate modern, quieter aircraft.

For more information on Chapter number charging categories please refer to Heathrow’s Conditions of Use (visitheathrow.com and search for “Conditions of Use”).

The points above are adjusted by a factor of 1.5 and a factor of 2 for evening (19:00-23:00 local time) and night (23:00-07:00 local time) periods respectively.

3. NOx emissions/Pax no

This is a relative emissions “efficiency” metric which is in many ways similar to the noise quota/pax no in the noise metrics set. For each arrival and departure we calculate the total mass of NOx emissions, based on the certified values and accounting for the number of engines for the aircraft associated with individual flights. The aggregate of certified NOx emissions for all flights of an airline are then divided by the aggregate passenger number.

4. CAEP standard (engine emissions certification)

Each engine has to be certified against the emissions standards produced and published by the ICAO’s Committee on Aviation Environmental Protection. This allows us to recognise the use of more efficient engine technology by giving better scores to aircraft that are compliant with the more recent and more stringent CAEP standards. Taking into account the specific aircraft associated with each arrival and departure, we determine the CAEP standard compliance and assign a specific score against each flight based on the table below. The score is based on the certification value for a single engine.

5. Continuous Descent Approach (CDA) violations

CDA involves arriving aircraft maintaining a steady angle of approach during the descent towards the airport, as opposed to a stepped approach which involves periods of prolonged level flight. This reduces noise because it requires less engine thrust and keeps the aircraft higher for longer. By following a CDA on arrival, the noise on the ground can be reduced by up to 5dBA in areas away from the final approach paths. The purpose of the indicator is to capture the non-CDA arrivals and so reduce the disturbance caused.

6. Track keeping (TK) violations

Departing aircraft are required to stay within the corridors of ‘Noise Preferential Routes’ (NPRs) – 3km-wide corridors in the sky, designated by the Government to ensure predictability of aircraft departure routes until they reach 4000ft above mean sea level. The track deviations indicator is expressed as the proportion of departures that flew outside the NPRs below 4000ft. Instances where this occurs for reasons outside of the airline’s control are excluded for the calculation e.g. due to weather avoidance.

7. Early or late movements between 23:30 and 04:30

This metric focuses on flights that take place during the time period within which the neighbouring communities are most sensitive to aircraft noise. For the purpose of this metric, we count the night flights that have operated between 23:30 and 04:30 local time and have not been granted a dispensation (e.g. due to medical emergency) and that are not exempt from the night quota system.

8. 4% climb failure

Departing aircraft are required to maintain a minimum climb rate of 4% between 1000ft and 4000ft. The metric indicates those airlines that do not have 100% adherence as indicated by the red dot.

9. Airline Engagement

The purpose of this metric is to highlight airlines who have attended airport meetings or have been in contact with Heathrow to discuss their performance including noise abatement requirements, night flights and future initiatives.