What Is That Sound?


#1

We live in a prevailing wind glide path, sometimes I hear a sort of whine/whistle sound when aircraft are on approach. Is it the sound of a changing wing surface? Are pilots “dumping their flaps” to decrease altitude without decreasing forward speed? I can hear this distinctive sound come on suddenly, it doesn’t fade in. Feedback appreciated on my questions and this incident.

Posted: Thu Jan 03, 2008 3:14 pm Post subject: KBTV Emergency Landing CRJ flaps prob


Burlington, Vermont - January 2, 2008

A plane had to make an emergency landing Wednesday night at Burlington International Airport.

An AirWisconsin flight, a regional carrier for US Airways, was approaching the airport when it reported a problem with its flaps. The Canadair regional jet had 51 people on board. After one aborted landing attempt, the plane was able to land safely.

“They had flap trouble, so the pilot took all the time in the world to make sure that he had enough front weight to get us down, and he did it perfectly,” said passenger Paul Lauzon of Montreal. “Overall, everybody did what they needed to do, everybody inside was quite calm. I guess it happens, and I guess it did, but I guess overall everything is good and we’re happy to be here.”

The temperature and wind chill dipped well-below zero Wednesday night, but the weather was not believed to have contributed to the plane’s mechanical difficulties.

WCAX News


#2

Could also be the engines; they tend to whine rather than roar at lower power settings.


#3

Landing gear going down increase the noise quite a bit if they are close overhead.


#4

Could be wrong but I have never detected a difference in sound from the ground depending on whether the flaps were up, down, or in transition. I doubt it could be the flaps. Probably just the different power settings like mduell said. Especially if it is a 757 in question!


#5

I’m not too sure about the 75, but I know that your D10, L10, 747, 767,777,C5 etc all whine. The fan blades are going supersonic. But usually on arrival you wouldn’t hear that. This is more of a high power setting climbout scenario. Awesome sound none the less, the A-10 and CRJ are also culprits of the engine whine.


#6

A320’s whine over my house. Im 10 miles west of PBI. 95 % are Jet Blues. I think an airtran uses an A320 sometimes. I do not hear the whine with any Boeing Aircraft flying over.


#7

Of course you don’t. Boeing doesn’t whine like Airbus does! :slight_smile:

That’s a joke, my son! Don’t take offense! Wash, rinse, repeat. If you don’t like the joke, then wash it out of your brain. Caution: do not iron your clothes while they are on your body.


#8

Airtran does not use A320’s.

The noise is not a product of the aircraft manufacturer, but the engine manufacturer. The A320 family is offered with two different engine suppliers, both of which have a different sound.


#9

No, I like it! I like it alot!

OK, of course that makes sense. I wasn’t thinking as usual! Thanks for the info!


#10

If I remember correctly, and it’s been a while since I took an aircraft noise course, there are 3 different types of noise produced by an aircraft.
Engine, airflow and mechanical.

Back in the days of the B707 and B727 the most notable sound near an airport was the engines. The aircraft of the day used turbojet engines and made a lot of noise coming and going. The turbofan engine on the other hand was much quieter and usually had a distinctive roar on takeoff/initial climb. It took decades to go from the old versions found on B747-200s DC-10s and L101s to what we have today just about fleet wide. Since the introduction of the turbofan engine, and the much quieter environment under the aircraft, another sound became more noticable and drew the wrath of tree hugger noise groups…

Airflow noise is what it implies. Noise caused by air flowing over the surface of the aircraft. When the airframe gets dirty i.e. extension of gear, flaps, slats, speed brakes and other stuff. The airflow noise increases as it passes across those sufraces that are hanging out. This is the whining sound heard near an airport as an aircraft slows and configures for landing. Engine noise also tends to increase to make up for the dirty airframe.

Mechanical noise is most noticable on the ground when there are no other sounds to interfer with it. The most common is the clacking of the fan blades as the wind passes through an engine at the gate, the opening and closing of doors and any other noise associated with the aircraft. As far as the APU goes I think it is classified as mechanical. Airport neigbors most often complain about mechanical noise during aircraft RONs on quiet windless nights. I live 6 miles from KBWI and I can hear the APUs in the distance in the very early morning hours.

Another factor that tends to increase noise complaints is a two fold problem. Aircraft operating under a low ceiling - noise will reflect off the cloud deck just above the aircraft and with a ceiling of say 3500 or below when an aircraft is easy to see. That type of noise complaint is filed as “I saw it and therefore it made too much noise.” Doesn’t matter how far away the aircraft was.


#11

The only planes that whine are the jet blue’s A320’s. And an accasional airtran. DL, WN, CO, AA, etc do not whine. Im sure they are all in similar flight modes ( dirty) Im thinking its more mechanical with the type of engines they are using.


#12

Right. On DL, WN, CO, AA, it is the passengers who are doing all whining!


#13

I agree, Jetblue is great, especially with their tv’s for my kids, the new aircraft for my wife, etc. However, we just flew CO PBI-EWR and can’t complain. had a sandwich ( actually 3 because i ate the kids too )each way, brought the laptop for the movie and they were on time :slight_smile:


#14

IIRC jetBlue has V2500 powered A320s, while the others have CFM56 powered B737s and Pratt powered DC9 derivatives for DAL/AAL.


#15

I live south of KBWI underneath the “45 to the downwind” landing west on RWY 28. Aircraft at that point are usually between 230 and 220 kts and are insturcted to reduce airspeed to 190 kts (less if it will be a tight visual approach) at that point and dumped from 3 or 4 thousand down to 2.

At that point the aircraft start to dirty up, slow down and go down.

They all whine. Some more than others.


#16

Are taking about women?


#17

Mark is correct. Further, the V2500 has a very distinct sound that could be said to resemble a “whine or whistle” at low power settings while reducing speed to configure for approach.


#18

Thanks for the info. Its the V2500’s on the JBU A320’s during power reduction that I am hearing. My wife willl even say Jet Blue when she can hear them.


#19

I think United and the former America West run the V2500 as well. They sound different than the NWA/FFT/USA A320’s. As far as the “whine” you hear, I’m guessing it’s from certain flap settings as the plane approaches. It’s more of a whistle, really. I hear it on every single A318-321 as they approach KSAN or KPHX or wherever I might be at the time,regardless of what airline it is. Speaking of flap settings, how many have noticed that the 737-NG at full flaps is soooo much quieter than the 737 Classic? Much less wake noise, too…