SAER
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Overview
The SAER is the weighted average (by demand) of the Arrival Efficiency Rate and Departure Efficiency Rate. It measures the extent to which an airport handled the number of aircraft it indicated it could accommodate, and how well the demand was met. For more information, see the FAA briefing System Airport Efficiency Rate (SAER).
Purpose
Throughout each day, airport air traffic control facilities periodically report the number of aircraft arrivals and departures that they are capable of handling hourly based on the current weather conditions, traffic mix, and runway configuration. The enroute centers rely upon those reported acceptance/departure rates to regulate the flow of aircraft to and from the facility. The system airport efficiency rate (SAER) is a good indicator of overall system performance. It measures the extent to which the airport facility handles the number of aircraft they indicated they could accommodate, and how well the demand is met. The best employment of available ground resources (e.g., airport runways and taxiways, landing and takeoff procedures, and air traffic control resources) will result in the highest available airport efficiency rate.
Data Sources for Calculation
Every day, approximately 50 airports provide the following data for the previous day through the Operational Information System, an Intranet site established by the Command Center:
- Hourly Airport Arrival Rate (AAR)
- Hourly Airport Departure Rate (ADR)
The number of actual arrivals and departures used for calculating the SAER are referred to in ASPM as Efficiency Counts. The Efficiency Counts are tabulated on a next-day basis using data from the Traffic Flow Management System (TFMS) and augmented with OOOI data provided by ARINC and TFMS, and ASQP data each month from BTS. The arrival demand is calculated by comparing the time the aircraft expected to land (based on its departure time and estimated time en route) with the actual landing time. Flights that land within 15 minutes of the expected time are given one unit of demand. Each additional 15 increments between the expected landing time and the actual landing time is counted as an additional unit of demand.
- Airport arrival and departure rate is the number of airport arrivals and departures that the facility can handle for that hour.
- The airport departure and arrival efficiency rates are combined and summed by quarter-hour to provide an overall system airport efficiency rate. Hourly rates for the entire operating day are weighted by arrivals in determining daily, monthly, and yearly totals.
- AAR and ADR data are received from designated facilities and are based on weather conditions, runway configurations, and arrival and departure traffic mix. Whenever AAR, ADR, or runway configuration changes during the day, additional records are provided with updated information. This information is then established in ASPM for 15-minute time periods for the entire day.
SAER Metric Calculation
The calculation of SAER metric depends on two variables, Arrival Efficiency Rate and Departure Efficiency Rate.
Arrival Efficiency Rate
The Arrival Efficiency Rate is the number of arrivals divided by the lesser of the Arrival Demand or the facility-set Arrival Rate, expressed as a percentage. The Arrival Efficiency Rate is a measure designed to determine how well the demand for arrivals is met and is determined by three factors:
- arrivals during a given quarter hour, or how many aircraft actually landed during that quarter hour
- arrival demand for a given quarter hour, or how many aircraft wanted to land during that quarter hour
- airport arrival rate, or the facility-set airport arrival rate for that quarter hour
Arrival Demand Computation
Demand is calculated from the following variables for each flight:
- Start of Demand = Wheels Off Time + Filed Enroute Time
- (this is the time the flight expects to arrive, i.e., wheels-on)
- End of Demand = Wheels On Time
- (this is the time the flight actually arrived at the arrival airport)
If a flight arrives within 15 minutes of the expected arrival time, it receives one unit of demand within that 15 minute period. Additional units of demand accumulate in subsequent 15-minute increments for aircraft that arrive more than 15 minutes past the expected arrival time.
Departure Efficiency Rate
The Departure Efficiency Rate is the percentage of time departures that are greater than or equal to departure demand or the facility-set departure rate. The percentage is determined by dividing actual departures by the lesser of the departure demand or the departure rate. The Departure Efficiency Rate is a measure designed to determine how well the demand for departures is met and is determined by three factors:
- departures during a given quarter hour, or how many aircraft actually departed during that quarter
- departure demand for a given quarter hour, or how many aircraft are expected to depart during that quarter;
- Airport Departure Rate, or the facility-set airport departure rate for that quarter hour
Departure Demand Computation
Demand is derived from the following variables for each flight:
- Start of Demand = Gate-Out Time + Unimpeded Taxi-Out Time
- (this is the time the flight should leave the departure airport, i.e., wheels-off)
- End of Demand = Wheels Off Time
- (this is the time the flight actually departed the airport). When a flight is issued an EDCT, the duration of EDCT Delay is subtracted from the departure demand and added to the Arrival side, not allowing negative demand. See EDCT for EDCT Departure Delay calculations.
Flights that depart within 15 minutes of the expected departure time receive one unit of demand within that 15-minute period. Flights that leave more than 15 minutes late accumulate additional units of demand in subsequent 15-minute increments. Therefore, departure demand for a particular flight can occur in several 15-minute time periods.
Example
At ATL on 8/28/2005, for the quarter hour from 16:00 to 16:14:
| Departures: 19 | Arrivals: 21 |
| Departure Demand: 20 | Arrival Demand: 42 |
| Departure Rate: 24 | Arrival Rate: 22 |
| Departure Efficiency: 19/20 = 95.00 | Arrival Efficiency: 21/22 = 95.45 |
APM Modules Reporting on SAER Metric
SAER metric is reported on in the following Aviation System Performance Metrics (ASPM) modules and reports:
