Aircraft Equipped With Active Noise Control System

UK airline Flybe has taken delivery of its 50th Q400 airliner. The aircraft is equipped with the 1,000th installation of Ultra Electronics’ Active Noise Control (ANC) system which is called the Active Noise and Vibration Suppression (ANVS) system on Q400 and other Bombardier Q-Series aircraft. Since the introduction of the ANVS system to Bombardier’s Dash 8 aircraft in 1996, the aircraft have been known as Q-Series airliners, signaling a new era in turboprop passenger comfort. The “Q”, obviously, means quiet.

Flybe, previously known as British European, placed an initial order for four Q400 airliners in March 1999. Subsequent orders were announced in 2003, 2005 and 2007, confirming Flybe as the largest operator of the aircraft type. Flybe which operates 190 routes in 13 countries, carried 7.5 million passengers in 2008.

“The Bombardier Q400 airliner has been the dominant factor in our growth and success,” said Jim French, Chairman and Chief Executive Officer of Flybe. “It has excellent operating economics, amazing performance, and the ANVS system contributes significantly to its outstanding passenger comfort.”

“Flybe operates the largest fleet of the world's most technologically advanced turboprop,” said Gary R. Scott, President, Bombardier Commercial Aircraft. “The Q400 airliner is optimized for short-haul service and Flybe’s successful experience with our high-speed turboprop's capabilities in European markets has set a standard which other airlines around the world can follow.”

Firm orders for the Q400 airliner have reached 347 aircraft, with 233 having been delivered as of January 31, 2009.

The Active Noise and Vibration Suppression (ANVS) System The ANVS system is the product of a program by Bombardier Aerospace that began in 1988 to find a solution for the noise and vibration concerns in turboprops. For the next few years, state-of-the-art systems were evaluated. The results, while promising, did not deliver the level of comfort that Bombardier wanted.

By October 1993, Ultra Electronics Ltd. of Cambridge, England had conducted successful demonstrations of Active Tuned Vibration Absorbers (ATVA) on a submarine and it was decided to try them out in the Dash 8 turboprop. By this time it was recognized that much of the cabin noise was generated by vibrations. Eliminating vibrations would help eliminate noise.

In mid-1995, after exhaustive testing, the ANVS system was perfected. It goes to the source of the noise — airframe vibration induced by pressure pulses from the propeller blades “beating” against the fuselage. Microphones concealed in the passenger cabin measure noise levels which are sent to an onboard microprocessor, together with propeller rpm and cabin pressure differential. The microprocessor then signals ATVAs attached to the fuselage frames to initiate out-of-phase counter vibrations to diminish the magnitude of the original  vibrations. Therefore, the noise-generating vibrations are dampened at their source so that most noise never enters the passenger cabin. An improved propeller synchrophaser with an accuracy of +/-5 degrees reduces the pressure pulses at the outset.

In conjunction with the ANVS system, the Dash 8 cabin was re-designed to eliminate or reduce bothersome rattles and buzzes. Interior components are “soft mounted” using elastomeric snubbers, while joints between components are acoustically sealed. Modified sidewall and floor panels reduce resonance. New thermal blankets — the insulation surrounding the cabin structure — have improved acoustical properties to absorb noise better.

FMI: www.bombardier.com, www.flybe.com/environment