Interview 3


Interviewee profile: Industrial, involved in WP4
Tags used: flight test – design – integration – wind tunnel test – high maturity level.


Jet and Airframe noise specialist, Airbus Operations SAS.

Q1: You are involved in the activities dedicated to the reduction of landing gear noise. The developed solutions are to be investigated in full scale during flight test. Could you please explain us the preparatory work performed by the partners before the flight tests? 
A1: The sources of landing gear noise are identified and the different technologies in AFLoNext to reduce landing gear noise have already been evaluated. Therefore, the first task was to select the low-noise treatments for flight tests. Comparing both their potential of noise reduction, their complexity and the associated costs allowed us to select a set of four to five technologies that are promising to provide significant noise reduction at aircraft level. This treatments were designed and manufactured at model scale to prove their low-noise potential in a wind tunnel test using an realistic model that represents the flight test platform (ATRA aircraft). The results of this test supported by numerical data will provide last information to design the treatments for flight tests. This process is coupled with the certification loop including loads and stress verification, material verification and airworthiness checks before the permit to fly may be received to start flight tests.

Q2: What are the challenges of the design of the low-noise treatments and their integration on the landing gear? Are you aim to suppress/reduce the landing gear noise itself or also any interference noise that caused from interaction of the landing gear with any other aircraft component?
A2: The challenges of design and integration are manifold and slightly different for flight test and wind tunnel test. The design on the wind tunnel model is strongly handicapped by model scale. Parts that are easy to manufacture at full scale may cause an issue at model scale due to their small size. Since noise generation is size-dependent additional aspects for wind tunnel test model design have to be taken into account.
For flight tests, there are a lot of integration constraints to be accounted for, such as weight, reliability, maintainability and non-interference with the functionalities of landing gear systems.
Low-noise add-on treatments generally aim at reducing landing gear itself after landing gear design is frozen.
Ideally, acoustic criteria would have to be incorporated at the landing gear design stage for new development. The landing gear and wing system should even be considered as a whole for global optimisation of aircraft noise.
Regarding the interference between landing gear with the wing system, the objective within the frame of AFLoNext is to investigate the optimisation of flap deflection angle to minimise landing gear noise and landing gear flap interaction noise. 

Q3: A wind tunnel test proving the low noise treatments efficiency was conducted and ended in December 2014. What were the conditions in which the wind tunnel test was performed? What are the main results and conclusions which you can draw from the wind tunnel test? To which extent do they influence the flight tests?
A3: The wind tunnel test was performed in NWB configured in anechoic open test section. The model tested was an A320 1/11th scale wing equipped with slats and flap and a main landing gear. Several slats and flaps settings were tested for flow velocity and angle of attack representative of approach condition, in order to assess installation effect on landing gear noise as well as landing gear flap interaction noise.
Both a baseline landing gear configuration and a low-noise landing gear configuration (landing gear equipped with noise reduction technologies) were tested in order to assess low-noise technology benefit on aircraft noise in installed configurations.
Data appraisal has yet to be conducted but on-line data preliminary analysis show evidence of the importance of the contribution to overall noise of the landing-gear flap interaction noise source.
These wind tunnel test results will be confronted to flight tests that will be performed next year.

Q4: It is planned that the investigated technologies reach a high maturity level because of the flight test preparation and the flight test itself. Could you please explain if and how the results of the flight tests could be further developed and exploited?
A4: First of all, flight test data will be analysed and used for proper technology evaluation. This will cover the assessment of the technologies separately and all together on the aircraft platform selected for flight test. A sufficient noise reduction at aircraft level has to be proven to trigger a way forward for further development.
In case of any unexpected shortfall re-designs may be necessary. Even in case the technologies do provide the overall noise reduction level expected, further optimisation of the tested technologies or the coupling with further low-noise treatments could be conducted. The availability of the AFLoNext flight test data is a very valuable item in this process. This is also the case for the complete loop of technology certification to make the technologies available for serial aircraft.
A further step will arise afterwards, to adapt the technologies that proved their potential of noise reduction to other aircraft platforms.