I've been noticing a noise from specifically A220-300 and one A320-232 aircraft overhead. Does anyone know the altitude and/or speed they deploy the landing gear at?

Posted by TrailbyDesign@reddit | aviation | View on Reddit | 13 comments

I've been in my local airports flight path for 20+ years and all planes sound about the same. About 6 months ago I started hearing this, what I can describe as a whiring down from some aircraft. I've been tracking them on flightradar just to see if there was a pattern. Most times I've heard it, it's been a Breeze Airbus A220-300 between 2000 and 3500 ft. and ~180 to 250 kts, and one Jetblue A320-232. I'm never outside when it happens but it is easily hearable inside. I think it's the landing gear being deployed but it's such a strange noise. I've had other Breeze A220s fly over at 6000 ft and 300 kts and they don't make the noise. Does anyone know what the altitude or speed for gear deployment is on an A220? I've looked through landing and takeoff charts but they are usually about weight and distance calculations. I'm not saying going crazy yet but my next step is to setup a sky cam.

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Speedbird14@reddit

A simple way of explaining the "Beluga Whale" sound from the PW1000G family of engines: It has to do with the design of the gearbox and the airflow through the engine.

The core is spinning a lot faster than the N1 fan. When spooling up, the mismatch of engine component rpm creates an audible resonance you hear.

Also: The A320 series used to have a unique whine while flying at lower speeds on climb out or approach. The airflow over the fuel overpressure protector holes under the wings created a high pitch audible whine.

Think of the sound a bottle makes when you blow air across the top, but at a higher pitch. Engineers designed vortex generators to be installed ahead of the FOPP holes to reduce the noise footprint of the aircraft to meet stricter noise abatement regs.

I miss the sound tbh. You always knew an airbus was coming before you could see it.

Bigbang-Seeowhee@reddit

As someone living under the approach path (or whatever you call it in English) of an airport I hear a howling noise when the planes start extending the flaps at about 3500 ft. If you've never heard it before you might look up at the sky and wonder if there's something wrong with the aircraft.

tfm992@reddit

It's engine spoolup likely, the GTF makes a very distinct noise.

It's unlikely to be gear, we don't deploy landing gear above 270kt, normal around 180, although I have been known to deploy faster and up to FL150 as the gear makes a great brake, it's very rare this happens.

Gear before being stabilised on final is normally when we are too high/fast and struggle to get the speed down, such as an ALT constraint that we need to hit at FL120 or higher (which on that airport is still too high ideally for 18 approach) and we often pass at around FL180 due to traffic in the neighbouring sector.