European helicopter experts are working within the framework of the Friendcopter
programme to reduce helicopter noise emissions. Defining low noise flight procedures
is a promising line of research that Eurocopter is actively pursuing.
In developing a more environmentally friendly helicopter,
Eurocopter has for many years been focusing on the fight
against noise as a key issue. The design offices of the companies
that would later form Eurocopter were already looking into
noise reduction in the 1970s. Their unstinting work resulted in
three generations of the Fenestron tail rotor, each quieter than
the last. With noise levels way below the regulatory requirements,
Eurocopter now possesses the quietest range of helicopters
in the world. Nevertheless, environmental pressure
necessitates that the hard work be continued.
Unlike the Clean Sky programme, which also aims to make
aircraft more environmentally friendly, the European
Friendcopter programme involves a more advanced level of
technology and is entirely dedicated to helicopters. Noise is
central to this project, on which Eurocopter is working with some thirty partners, including several research centres.
“An important aspect of Friendcopter relates to low noise procedures,
and this is defined in three ambitious goals,” explains
Marc Gervais, who is in charge of this Eurocopter work group.
“In the first place, we wanted to propose a European methodology
for acquiring and analysing the necessary data for the
definition of low noise procedures. We then needed to create a
reliable tool to calculate the noise footprint on the ground and,
ultimately, to perfect these procedures.”
A flight test campaign, one of the most exhaustive carried out in
this field to date, was performed with an EC130. Every possible
manoeuvre was tested in order to acquire a comprehensive
database, including stabilised flight procedures (takeoffs,
approaches and overflights) and non-stabilized flight procedures
(acceleration, turns and decelerating steep approaches).
As many as 36 microphones were set up over an area
of approximately 45 hectares (780 m x 580 m). “This is a truly exceptional test procedure,” insists Marc Gervais. “By way
of comparison, the certification of helicopters is normally
performed using only three microphones on the ground.
But, during these tests, we employed the same method
that was used for the certification of the Airbus A380.” And
even though they are still being analysed, the results promise
a wealth of information. An indication of this potential is the
fact that the Eurocopter team won an award for the initial report
that it presented at the latest European Rotorcraft Forum
For the benefit of everyone
“At the same time, we have also developed HELENA
(HELicopter Environmental Noise Analysis), a tool that predicts
noise footprints,” continues Marc Gervais. “HELENA will allow
us to measure the environmental impact of helicopters more
accurately. It is a tool that is very well adapted to rotary wing
aircraft because it not only takes into account noise levels on
the ground, but also the very particular characteristics of noise
directivity, including the question of advancing and retreating
blades, which makes helicopter noise studies more complex
than those for airplanes. HELENA will be ready by the time the
Friendcopter project draws to a conclusion, and we will then
use it to assess the modifications made to helicopters as part
of the Clean Sky programme.”
Two versions of HELENA have been developed: the first for
manufacturers and research centres, and the second for public
users such as operators, and the airport and aviation authorities
- all of whom are potentially interested in a precise assessment
of the noise impact of helicopters.
“Beyond noise reduction procedures, Friendcopter also covers
other noise-related subjects,” adds Marc Gervais, who cites
engine noise reduction as an example. But engine manufacturers
are not the only companies affected by this issue: engine
integration, and the shape, position and design of tail pipes and
air intakes are the helicopter manufacturer’s responsibility.
Finally, mention should also be made of work being carried out
on active noise control systems for main rotors. Friendcopter is
investigating this field as part of its overall objectives to reduce
noise, and Eurocopter is also conducting its own research programme
on this subject.
The next step for this research will be to apply the Friendcopter
results within an actual regulatory framework. This will assess
whether helicopters using the new procedures will be compatible
with other air traffic.