In Seattle today and watching a DL A220 on approach, writing this at 2:36pm PST. Flight coming in from Austin.

What's causing the howling sound during approach? It last for a few seconds, but happens every time. Thoughts welcome. Thanks!

seat1a wrote:

In Seattle today and watching a DL A220 on approach, writing this at 2:36pm PST. Flight coming in from Austin.

What's causing the howling sound during approach? It last for a few seconds, but happens every time. Thoughts welcome. Thanks!

It is known, it is the GTF (Geared turbo fan) jet engine, which makes at different trust levels strange noises, including at one trust level the the howling sound.

It is also called the "GTF Whale song".
https://www.youtube.com/watch?v=XkFMuIheC3g

https://twitter.com/flightradar24/statu ... 25026?s=21

Podcast on the noise.

Months ago I would hear the ghoulish moaning of the gtf engines when arriving on 17L or 17C. Since I hadn’t heard it in a while, I thought the haunted souls had gone hunting elsewhere.

I was actually going to ask the same thing about A*3*20's. Whenever a 320 series jet flies over, the moment it comes into hearing range it sounds like a landing UFO. "Beeeyoooooooo." Engine inlet shape or something? No other airplane does that and it's loud and distinct every time.

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N766UA wrote:

I was actually going to ask the same thing about A*3*20's. Whenever a 320 series jet flies over, the moment it comes into hearing range it sounds like a landing UFO. "Beeeyoooooooo." Engine inlet shape or something? No other airplane does that and it's loud and distinct every time.

I have been told that that is the speed brakes being stowed......

Also the The PW 777s howl exactly like that.

N766UA wrote:

I was actually going to ask the same thing about A*3*20's. Whenever a 320 series jet flies over, the moment it comes into hearing range it sounds like a landing UFO. "Beeeyoooooooo." Engine inlet shape or something? No other airplane does that and it's loud and distinct every time.

Probably the airline didn’t install the fuel vent sound reduction device.

hayzel777 wrote:

N766UA wrote:

I was actually going to ask the same thing about A*3*20's. Whenever a 320 series jet flies over, the moment it comes into hearing range it sounds like a landing UFO. "Beeeyoooooooo." Engine inlet shape or something? No other airplane does that and it's loud and distinct every time.

Probably the airline didn’t install the fuel vent sound reduction device.

Fuel vents! Interesting. It seems that every US-based airline's 320's make the "UFO" noise.

https://www.oharenoise.org/noise-manage ... -2020/file

Haven't head a A 220. I wonder if it's louder than a descending RR Sprey equipped BAC 1-11. Now that was a howl. On takeoff It crackled and shook your fillings. Miss those days.

N766UA wrote:

hayzel777 wrote:

N766UA wrote:

I was actually going to ask the same thing about A*3*20's. Whenever a 320 series jet flies over, the moment it comes into hearing range it sounds like a landing UFO. "Beeeyoooooooo." Engine inlet shape or something? No other airplane does that and it's loud and distinct every time.

Probably the airline didn’t install the fuel vent sound reduction device.

Fuel vents! Interesting. It seems that every US-based airline's 320's make the "UFO" noise.

https://www.oharenoise.org/noise-manage ... -2020/file

It depends on the age of the aircraft. Newer aircraft typically come with the fuel vent vortex generators installed/service bulletin applied at delivery from Airbus. The SB can be retrofitted, and is being applied to many older A320s out there in the US. B6 is doing this SB during C-checks, others airlines I do not know as some A320s in DL/UA/AA are old and may be getting retired so it may not be worth modifying those aircraft.

Heard a similar sound on a PrimeAir 767 a few minutes later. Same fuel vents?! LOL

Heard a similar sound on a PrimeAir 767 a few minutes later. Same fuel vents?! LOL

B6JFKH81 wrote:

N766UA wrote:

hayzel777 wrote:

Probably the airline didn’t install the fuel vent sound reduction device.

Fuel vents! Interesting. It seems that every US-based airline's 320's make the "UFO" noise.

https://www.oharenoise.org/noise-manage ... -2020/file

It depends on the age of the aircraft. Newer aircraft typically come with the fuel vent vortex generators installed/service bulletin applied at delivery from Airbus. The SB can be retrofitted, and is being applied to many older A320s out there in the US. B6 is doing this SB during C-checks, others airlines I do not know as some A320s in DL/UA/AA are old and may be getting retired so it may not be worth modifying those aircraft.

If I recall what I've heard correctly, every A320 family aircraft built from sometime in 2014 onward has been fitted with the vortex generators at the factory (including all NEOs). AA's sharklet A321s and all DL A321s have the mod. The ex-US fleet, AA's sharklet A319s, the ex-NW fleet, and all of UA's fleet don't. Although I've heard a few ex-US CFM A321s go overhead without howling, so either AA is retrofitting them or the noise is related to airspeed or something.

The howl sounds so satisfying and it'll be sad to see it go. It makes the A320 series so unique.

seat1a wrote:

Heard a similar sound on a PrimeAir 767 a few minutes later. Same fuel vents?! LOL

Many widebodies make similar howling noises with their large engines. The CF6 used on many Prime Air 767s can sound interesting. But as far as I'm aware, the fuel vent noise is unique to the A320.

N766UA wrote:

I was actually going to ask the same thing about A*3*20's. Whenever a 320 series jet flies over, the moment it comes into hearing range it sounds like a landing UFO. "Beeeyoooooooo." Engine inlet shape or something? No other airplane does that and it's loud and distinct every time.

The sound I *think* you’re describing is caused by the speed brakes being open (beeeyooooooo) or closed (whoooop). It is not unique to the A32X but is definitely pronounced! Any jet with speedbrakes makes this sound to varying degrees.

The whistling sound on approach from older A32X is from air blowing across underwing fuel vents.

The howling sound described by the original poster is also heard on the Embraer E2 jets, which also have geared turbofans. I suppose we will be hearing more of these interesting sounds in the coming years!

I was on a LX A220 once when it started making funny noises like this, first time I'd heard it, and it was like what the hell was that? Now I know!

orlandocfi wrote:

N766UA wrote:

I was actually going to ask the same thing about A*3*20's. Whenever a 320 series jet flies over, the moment it comes into hearing range it sounds like a landing UFO. "Beeeyoooooooo." Engine inlet shape or something? No other airplane does that and it's loud and distinct every time.

The sound I *think* you’re describing is caused by the speed brakes being open (beeeyooooooo) or closed (whoooop). It is not unique to the A32X but is definitely pronounced! Any jet with speedbrakes makes this sound to varying degrees.

The whistling sound on approach from older A32X is from air blowing across underwing fuel vents.

The howling sound described by the original poster is also heard on the Embraer E2 jets, which also have geared turbofans. I suppose we will be hearing more of these interesting sounds in the coming years!

Thanks!

I was on one a few days ago. When the flaps came out they made a howling sound. Very similar to the sounds the BAE 146 used to make with movements of the flap system.
Beauty of an aircraft took off like a rocket.

orlandocfi wrote:

N766UA wrote:

I was actually going to ask the same thing about A*3*20's. Whenever a 320 series jet flies over, the moment it comes into hearing range it sounds like a landing UFO. "Beeeyoooooooo." Engine inlet shape or something? No other airplane does that and it's loud and distinct every time.

The sound I *think* you’re describing is caused by the speed brakes being open (beeeyooooooo) or closed (whoooop). It is not unique to the A32X but is definitely pronounced! Any jet with speedbrakes makes this sound to varying degrees.

The whistling sound on approach from older A32X is from air blowing across underwing fuel vents.

The howling sound described by the original poster is also heard on the Embraer E2 jets, which also have geared turbofans. I suppose we will be hearing more of these interesting sounds in the coming years!

This video is a perfect example of the different A320 sounds: https://youtu.be/Tg4RgCbcc8k

The description has more detail, but the speedbrake sound starts at 0:25 and the FOPP whine at 0:45 (which I've also heard on climbout as well as approach)

CriticalPoint wrote:

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N766UA wrote:

I was actually going to ask the same thing about A*3*20's. Whenever a 320 series jet flies over, the moment it comes into hearing range it sounds like a landing UFO. "Beeeyoooooooo." Engine inlet shape or something? No other airplane does that and it's loud and distinct every time.

I have been told that that is the speed brakes being stowed......

Also the The PW 777s howl exactly like that.

Was going to mention those...there’s also a howl in the CFM56-3 and RR Trent 700.

Back to OP's topic of the A220 howling sound... It is most certainly from the engines.

D L X wrote:

https://twitter.com/flightradar24/status/1335965511293825026?s=21

Podcast on the noise.

For those of you without the time to listen to the 45 minute podcast:

The explanation comes from P&W's VP and General Manager of the GTF Program. From the interview:

-- He describes the "howl" as a "transient combustor tone" in lower power regions. All engines basically have their own flavors of these tones; this one is unique to the GTF on the A220. (Which describes OP's observation)
-- He mentioned that is mostly "typical on an autopilot approach" as the engines are at lower power, making small adjustments within this regime. Also common on taxi and startup.
-- This is unique to the A220's GTF as the GTFs on other aircraft simply have different dimensions, and the resonance doesn't produce the same howl.

BONUS FACT from the interview: The green area ahead of the fan is an ablative material P&W unofficially refers to as "blue goo." It's an engineered material (it's not painted) that offers a tighter seal between the fan blade an the ablative material than previous-generation materials.