Experts from Lufthansa Technik will be equipping the 100th aircraft of the Lufthansa A320 fleet with sound-reducing vortex generators in the next few weeks. The Lufthansa Group and German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt, DLR) project is part of the research group “Quieter Transport” (“Leiser Verkehr”), has thus reached an important milestone. Since November 2014, Lufthansa has equipped its short and medium-haul aircraft of the types Airbus A319, A320 und A321 with the noise-reducing components on the underside of the wings. It is the first airline in the world to do so. In total, 157 aircraft in the short and medium-haul fleet are being equipped with a vortex generator. Newly built Airbus aircraft have already been delivered to Lufthansa with the sound-reducing technology since the beginning of 2014. More than 200 Lufthansa jets will fly much more quietly in future.
Flyover measurements taken by Lufthansa in cooperation with the DLR show vortex generators remove annoying tones and significantly reduce the overall noise level of the aircraft when landing – by up to four decibels at distances of between ten and 17 kilometres away from the airport. According to information from the manufacturer, this effect is even greater further away from the airport. These tones were previously created by airflows over circular pressure equalisation vents for the fuel tanks on the underside of the wings during flight. The new components generate an air vortex over the pressure equalisation vents for the fuel tanks that effectively prevent these tones from being created.
This measure is part of the Hessian “Noise Protection Alliance“, which was agreed by the state government of Hesse and the airline industry.
MD-11 measurement flights made by Lufthansa Cargo in Magdeburg-Cochstedt
Equipping or converting the A320 fleet is one of the most extensive voluntary measures for active sound reduction undertaken by Lufthansa to date. A further possibility to significantly reduce aircraft noise will be intensively tested in the next few weeks in flyover measurements over several days at Magdeburg-Cochstedt airport with two MD-11 freight aircraft from Lufthansa Cargo. Modified sound suppression has been installed on the engine intakes of the General Electric CF6-80C2 engines. In the MODAL project, sponsored by the German Federal Ministry for Economic Affairs, Lufthansa has already carried out investigations on a Lufthansa Technik engine test bench in Hamburg together with the DLR. This first step produced the main evidence that the so-called Hardwall Acoustic Panels in the engine intake have a noise-reducing effect. Now, in the second step, the effectiveness of the panels under real conditions is being investigated. In addition, Lufthansa expects findings to be made about reductions in landing gear noise achieved by covering the cavities in the aircraft landing gear.
During the flyover measurements at Magdeburg-Cochstedt, the aircraft approaches the airport several times, as if it were landing, and then overflies the airport several times in a certain configuration. Other constituents of the measurements programme are take-off flights with ground measurements at various engine revolution levels. Numerous microphones on the ground record the sound of the aircraft flying at different heights during every flyover. The measurement data will form the basis for possible approval of the modification for the existing Lufthansa Cargo MD-11 fleet.
The most important measure for reducing flight noise is continual investment in new aircraft. The Lufthansa Group will receive a total of 259 aircraft of the latest generation by 2025. Thus in future, 59 state-of-the-art aircraft – 34 Boeing 777-9Xs and 25 Airbus A350-900s – will supplement the long-haul fleet of the Lufthansa Group. The A350-900 will already be delivered from 2016. The noise emissions of the new models are considerably lower than those of today’s aircraft.