Will Brussels Airport’s 15-metre noise walls make engine tests noticeably quieter?

Brussels Airport has begun construction of a new aircraft-engine testing site on its grounds in Flemish Brabant, installing a U-shaped acoustic enclosure with walls at least 15 metres high. The airport expects the facility to enter service by January 2027 and says it will reduce the noise reaching residents of Kortenberg, Zaventem and Steenokkerzeel.

The work concerns an unavoidable but unusually intense part of airport operations. After maintenance, technicians must run some aircraft engines at high power before an aircraft can safely return to service. Brussels Airport Company says this happens about 270 times a year. Tests are currently restricted to between 07:00 and 22:00, but individual runs have produced measured peaks of between 50 and 75 decibels at monitoring points around the airport, depending partly on weather conditions.

For nearby residents, the project promises relief from that specific source of ground noise. It will not, however, alter flight paths, runway use, night-flight numbers or the noise created during take-off and landing. That distinction matters across the airport’s densely populated surroundings and in parts of the Brussels-Capital Region, where most complaints and political disputes concern aircraft in the air rather than maintenance tests on the ground.

Belgian public broadcaster VRT NWS and Brussels outlet BX1 reported that construction is now under way. Brussels Airport’s own environmental information describes the installation as a dedicated high-power test area protected by noise barriers. A federal noise-reduction plan published through the airport mediation service is more specific: it anticipates a reduction of roughly 5 to 10 dB(A), especially towards Kortenberg, Zaventem and Steenokkerzeel. Because decibels use a logarithmic scale, that would represent a meaningful change if subsequent measurements confirm the projection.

The project also has a longer history than the start of construction suggests. Brussels Airport announced in February 2020 that it would relocate the testing area after measurements showed widely varying noise effects. It initially envisaged opening a replacement by the end of 2021, but technical development and the permitting process pushed the timetable back. The federal mediation plan notes that ministerial decisions in 1988 and 1991 calling for a covered engine-testing hall were never implemented.

Brussels Airport Company presents the enclosure as part of a wider effort to reconcile aviation activity with its surroundings. It has differentiated airport charges according to aircraft noise since 2004 and says the least efficient aircraft can now pay up to 20 times more. BATC, the information platform operated with Belgian air-navigation provider skeyes, reported that 36% of flights in 2024 used the most noise-efficient aircraft category, up from 25% in 2019. Nevertheless, the estimated number of potentially highly annoyed residents within the 55 dB Lden contour remained broadly stable at 13,323.

The airport’s operational case and the public-policy perspective therefore overlap without being identical. Brussels Airport stresses that full-power tests are safety-critical and argues that acoustic engineering can preserve maintenance activity while reducing nuisance. The federal airport mediation service treats the enclosure as a useful measure but only one component of a broader plan covering flight procedures, night operations and enforcement. Residents concerned about overflight noise should not expect the walls to solve those separate problems.

There is also an EU dimension, though the construction project itself is Belgian. The Flemish Council for Permit Disputes annulled the airport’s 2024 environmental permit in July 2025 because Belgium had not first completed the procedure required by EU Regulation 598/2014 for noise-related operating restrictions. That regulation requires authorities to compare quieter aircraft, land-use measures, operational procedures and restrictions through a cost-effective “Balanced Approach”. The council allowed airport operations to continue under the annulled conditions while the Flemish authorities prepare a replacement permit by June 2029.

No new response to the start of construction was identified from federal Mobility Minister Jean-Luc Crucke or the Flemish environment administration. The immediate test will come after commissioning: Brussels Airport will need to show, through transparent before-and-after measurements, whether the promised reduction is achieved in the communities named as beneficiaries. Completion by January 2027, the measured performance of the enclosure and any further delay are now the points to watch.