Aviation enthusiasts can tell if it’s an Airbus A220 taking off just by the distinctive sound it makes. This howling sound is sometimes described as sounding something like a whale, and is indirectly related to its Pratt & Whitney PW1500G geared turbofan. Variants of the PW GTF also power the Embraer E-Jet E2 series and some of the Airbus A320neos, but those aircraft do not have the same degree of howling sound.
The Airbus A220 is distinctive from the rest of the aircraft in Airbus’s lineup as it started out as the Bombardier CSeries and was only sold to Airbus after it had been developed. While the A320, A330, A350, and A380 share some design elements, the same can’t be said of the A220. Even though the A220 is one of the quietest aircraft in its class, there were some complaints by residents living near Zurich Airport in 2018 when the aircraft debuted. These complaints specifically accuse the A220 of being noisy due to the ‘whale’ sound.
Not Caused By Engines As Such
The Airbus A220 (formerly CSeries) comes with a distinctive low-power combustor/combustion tone. The howling sound is variously described as a whale, wailing, or siren-like sound that rises and falls. This is audible because the aircraft’s PW1500G geared turbofans are so quiet, and is the result of a specific aerodynamic/ventilation combination.
The high-pitched howling sound is audible during takeoff and its initial climb. It is caused by the aircraft’s cabin pressurization and air conditioning system. The sound is still apparent on the Embraer E-Jet E2 aircraft powered by the PW1900G variant, although it’s less apparent than on the A220. It is the least noticeable on the Airbus A320neo with its PW1100G variant of the PW GTF engine family.
Some engines do have their distinctive sound. For example, old Pratt & Whitney JT8D engines had a distinctive buzz-saw noise. JT8D engines powered the Boeing 727, Boeing 737 Original, DC-9, and MD-80 airliners. Buzz sounds were common on early commercial aircraft. Contributing factors included low-bypass turbofan architecture, fan noise, and the lack of advanced noise suppression technologies that are now standard.
The A220’s Sound During Take Off
As stated, the distinctive A220 take-off sound is caused by the aerodynamic/ventilation dynamics related to the aircraft’s cabin pressurization and air conditioning. The A220’s PW1500G engines are bleedless engines that do not extract high-pressure bleed air from the compressor for cabin pressurization and air conditioning, unlike other engines.
The A220 has dedicated electric-motor-driven cabin air compressors (CACs) located in the bell fairing. They take ambient ram air, compress it, and feed it into the aircraft’s environmental control system. As the aircraft takes off (and the aircraft is in a high-power phase), a strong aerodynamic whistling or howling tone is created.
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Airbus A220 characteristics (per Airbus) |
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|---|---|
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Lower fuel burn |
25% compared with the previous generation aircraft |
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Passenger capacity |
100-160 |
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Powerplant |
Pratt & Whitney PW1500G |
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Range |
3,400-3,600 nautical miles |
The audible frequency is roughly 400–800 Hz. The sound starts right after takeoff when the environmental control system packs switch to high flow, reaches a peak, and then fades as the aircraft climbs, and the inlet doors then modulate or the ram pressure changes. Pratt and Whitney’s VP and Regional Jet GTF Engine GM, Graham Webb, has said the sound is a low-power transient combustor tone. He stated that the pressure changes against the combustion structure create an effect similar to blowing over the opening of a bottle.
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Why The Sound Is Not So Apparent On Other Aircraft
The whale sound was an unintended side effect of the Airbus A220’s particular cabin air inlet duct geometry and lack of acoustic mitigation. But it is now a loved attribute of the regional jet. Airbus and Embraer were able to engineer their aircraft with PW GTF engines to avoid the sounds. Embraer has a different cabin air compressor arrangement, although the compressors are still electric. Among the differences is more acoustic damping.
The Airbus A320neo is optionally powered by the PW1110G-JM GTF, and it uses the same basic principle as the A220. However, the A320neo is designed with a flush NACA-style scoop inlet on the lower fuselage (the A220 has a protruding scoop). The ducting is also designed with a heavier acoustic lining. Airbus was able to benefit from Bombardier’s earlier design that had early noise complaints about the howl, and designed the A320neo to mitigate it.
Consequently, the A320neo’s noise is more of a low-frequency and conventional “roar.” Another contributing reason why it isn’t heard on older aircraft is that older aircraft’s engines are much noisier. These older, noisy engines would drown out and mask the sound. The PW GTF’s noise reduction is around 75% quieter compared with previous-generation aircraft.
Other Distinguishing Characteristics Of The A220
While the ‘whale sound’ of the A220 is one of the attributes that set the A220 apart from other aircraft, it is not the only one. When looking at the A220 head-on, it’s hard not to notice how big the engines are relative to the aircraft’s narrow fuselage. The A220 does not have the distinctive “bark” of Airbus A320s (more on that below) or the rumble of older Embraer E-Jets powered by CF34 engines. It also doesn’t have the loud spool-up whoosh of the GE90.
Inside the cabin, some passengers have compared the A220 to the Boeing 787 Dreamliner, with some calling it a “mini” 787. One of the most notable features of the aircraft is its large windows, which are the largest of any Airbus aircraft to date. In addition to the large windows, other features include modern climate control, a higher cabin pressure, large overhead storage space, and a quiet cabin.
Another way to determine if the aircraft is an A220 is to check the operator. In the United States, they are operated by Delta Air Lines (145 ordered), JetBlue (100 ordered), and Breeze Airways (90 ordered). In Canada, they are operated by Air Canada (65 ordered), but not by WestJet. In Europe, their top operators are Air France—KLM, airBaltic, SWISS, and ITA Airways. They are not so common outside of North America and Europe, although EgyptAir has 12 examples, Korean Air has 10, and Australia’s QantasLink has ordered 29. Other operators include Iraq Airways, Air Tanzania, Air Niugini, and Air Vanuatu.
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The Airbus A320 “Barks” While Taxiing
The Airbus A320 may not sing like a whale, but it does “bark” like a dog. The barking is heard during taxiing, both before take-off and after landing. The “bark” is caused by the Power Transfer Unit (PTU) and is also heard on the widebody Airbus A330. The sound is that of the PTU undergoing self-tests to ensure hydraulic system redundancy. To ensure redundancy, the A320 is designed with three hydraulic systems, so that other systems are available should one fail.
The PTU is a hydraulic device that transfers power between systems to maintain 3000 psi of pressure. The PTU operates automatically. It detects pressure differences between the systems and transfers the needed power as required. The hydraulic power is used to operate some of the aircraft’s vital systems, like landing gear, the engine reverse thrust doors, and flight control surfaces.
The PTU typically activates after both engines are started, although it can run when only one engine is running. After the engines are switched on, the aircraft’s warning computers check that the PTU is functioning and get the unit to perform a self-test. Like the howling sound on the Airbus A220, the barking sound is a normal part of the aircraft’s operation and is nothing to worry about. The PTU can bark during flight, but if it did, it might not be audible to passengers as the roar of the engines would likely drown it out.
A Successful Aircraft With Emerging Engine Issues
Paradoxically, the distinctive acoustic signature of the A220 is partly due to the aircraft’s very quiet fan noise because the PW1500G is a very large and slow-turning fan. Its takeoffs and approaches are much quieter compared with previous-generation aircraft. Besides the acoustic signature, another way for those wanting to set the A220 apart from other jets is by looking at the landing gear. The aircraft sits higher on its landing gear compared with E-Jets or A320s relative to its fuselage height. The cockpit also appears to have a big windshield and a small nose due to its cockpit windows being low and wide.
Development work on the CSeries began in 2008, and it entered service in 2018 and was renamed the A220. It has proven to be a reasonably popular regional aircraft and has competed well against the Embraer E-Jet. So far, the aircraft has accumulated almost 1,000 orders with around half delivered. While that is much fewer than the aspirational target of 3,000 Airbus hoped for, it is respectable for a regional jet.
Pratt & Whitney seems to have fallen on hard times when it comes to engines compared with GE Aerospace. GE and Rolls-Royce have effectively pushed it out of the widebody engine market. PW has focused on its GTF engines for narrowbody and regional aircraft. However, issues with the engine have proven extremely problematic for A320neo aircraft. Until recently, its GTF engines on A220s had escaped these issues. However, issues have started merging recently, causing more of the aircraft to be grounded.
