Emerald Group Publishing Limited
Copyright © 2008, Emerald Group Publishing Limited
Measurement flights at Schiphol halved
Article Type: Safety notes From: Aircraft Engineering and Aerospace Technology: An International Journal, Volume 80, Issue 4
The number of measurement flights for standard maintenance of the instrument landing system (ILS) at Schiphol Airport were reduced by half as of 1 June 2007. Many measurement flights will be replaced by ground measurements, reducing night time noise nuisance in communities surrounding the airport.
The ILS allows pilots to land safely, even when visibility is poor. Antennae located alongside and at the end of the runway emit radio beams that mark out the ideal flight path. The ILS has to function perfectly, in accordance with international requirements of the ICAO. Ground equipment monitors the system and emits an alarm signal if disturbances are detected. LVNL regularly inspects the ILS as well as the alarm system. These inspections take place on the ground, via runway measurements, and in the air, by way of measurement flights. These measurement flights must be conducted in the evenings, starting after the last takeoff peak and sometimes ending around midnight, depending on the runway in question. A study jointly conducted by air traffic control, The Netherlands (LVNL) and NLR, commissioned by the Knowledge and Development Centre Mainport Schiphol, indicated that the number of measurement flights could be reduced.
In the study, NLR made use of a computation model that accurately predicts how an ILS radio beam functions when influenced by ground factors (such as humidity) and buildings. NLR’s Air Transport Safety Institute conducted a statistical analysis of data previously collected during measurements in the air and on the ground. The study indicated that the ground measurements and monitor alarms are sufficient. Even under extreme circumstances –, e.g. after heavy rain and during extended drought – the ground measurements can replace some of the measurement flights.