LASoctoberB6 From Japan, joined Nov 2006, 2380 posts, RR: 1 Posted (4 years 10 months 1 week 4 days 7 hours ago) and read 6332 times:
My house is located under the FUZZY7/SUNST2 arrival in Las Vegas. Besides hearing the odd-sounding A320s fly over (like a deeply pitched low whistle), I notice another major sound. I get the feeling its when the speedbrakes are up and you can hear that sort of rumbling sound underneath them. Sometimes, the rumbling dissipates when it's just past directly overhead. I don't know, it's hard to explain. When on-board an aircraft and its on approach, the pilots will use the speed brakes, which I'm well aware you all know. The turbulence from the disruption of the airflow over the wings creates the same kind of rumble which can be heard all throughout the plane. Well, I can tell when they come up and do their business. Did this make sense? I hope so..
musang From United Kingdom, joined Apr 2001, 872 posts, RR: 6
Reply 2, posted (4 years 10 months 1 week 3 days 16 hours ago) and read 6017 times:
I often hear A320 series aircraft make a curious varying pitch rough whistling sound as they come over my place. From where they are in the arrival, I deduce that an initial flap extension is what's causing it, but have never asked an Airbus pilot. Or could it be the belly landing lights extending?
The 146/RJ series make a considerable "howling" noise as the flaps go to the initial setting (can't remember what that was) which can even be heard in the flight deck.
747fan From United States of America, joined Jun 2007, 1194 posts, RR: 1
Reply 4, posted (4 years 10 months 1 week 3 days 13 hours ago) and read 5884 times:
From what I've observed IAE-powered A320's make that whistling sound that was described, its a rather eerie sound in my opinion. I've noticed it when the aircraft are still far enough out that the flaps/landing gear haven't been deployed; an example is A320's flying downwind over the Hudson River & Manhattan into LGA.
TupolevTu154 From Germany, joined Aug 2004, 2188 posts, RR: 27
Reply 6, posted (4 years 10 months 1 week 1 day 17 hours ago) and read 5410 times:
Quoting musang (Reply 2): The 146/RJ series make a considerable "howling" noise as the flaps go to the initial setting (can't remember what that was) which can even be heard in the flight deck.
The first time I heard this on the ground underneath base for 08 at LGW I was absolutely terrified, I had no idea what it was and it scared the living sh*t out of me! Obvously I am now aware of what it is. I was sat in 12A on approach to EDI on a BA RJ100 and as soon as the flaps started to extend the noise could be heard very loud in the cabin. I guess it's the exhaust being disturbed by the extendig flaps.
I know all too well about the howling/whistling A32X's make, I live in sight of LGW's downwind, base and final legs and hear them all day every day courtesy of U2 and BA A319's.
Obviously depending on weather conditions, etc., the trailing vortices will not typically dissipate right after the aircraft passes overhead. Indeed, vortices can stick around for a long time (and left on their own, they will slowly descend toward the ground). So you might actually hear them well after the airplane has passed overhead.
However, I'd wager it's pretty unlikely that you'd hear them from an airplane passing 8000' overhead.
With that said, since all the noise from an airplane is transmitted by air pressure disturbances, I guess you could make the argument that all the noise comes from the wake
fly2hmo From , joined Dec 1969, posts, RR:
Reply 12, posted (4 years 10 months 1 week 9 hours ago) and read 4916 times:
Quoting LASoctoberB6 (Thread starter): The turbulence from the disruption of the airflow over the wings creates the same kind of rumble which can be heard all throughout the plane
It's really hard to tell what sound you are hearing. It is highly unlikely you can hear the wake turbulence anywhere above 500ft AGL Aside from the engines, the most significant source of exterior sound will be the landing gear and flaps. Even a plane in a clean configuration makes plenty of noise. I've noticed planes flying over head at what seemingly is idle speed get much noisier as the extend the gear. Heck it is really obvious from inside the cabin as it is.
On a side note, gliders can be surprisingly noisy.
Quoting aerdingus (Reply 3):
Just curious..are they CFM or IAE birds? I think the CFM's sound mad. I've been thinking of how to describe them, and they do sound whistley..
You're probably thinking of IAE engines. The CFM A320s, and 737s for that matter, don't make that distinctive sound.
Quoting 747fan (Reply 4): From what I've observed IAE-powered A320's make that whistling sound that was described, its a rather eerie sound in my opinion.
Agreed. First time I heard an A320 when I was a kid it sent major shivers down my spine.
Quoting fly2hmo (Reply 12): It's really hard to tell what sound you are hearing.
This is why I need to get a voice recorder! But, even if I did, it would be hard to catch one making the noise. One, because they don't all do it, and two, Not a lot of A320s fly over nowadays due to US Airways' 50 percent reduction in service here.
Our 737 classics - the only limitation is no speed brake below 1000 feet radio altitude. Flap 40, gear down - the speed brakes are quite dramatic in terms of noise and vibration! I don't have to do it often, but I enjoy a challenge, and yes, a quick reassurance on the PA is important. I feel that idle thrust, and dirty as possible gives the best possible descent angle, which is more important than descent rate in a short cut situation.
CC I know you were referring to wing speed brakes. On the 146 series there was no limitation of course, indeed manufacturer's recommendation was to fully deploy the brake at 100 feet on the approach.
CosmicCruiser From United States of America, joined Feb 2005, 2255 posts, RR: 15
Reply 16, posted (4 years 10 months 6 days 21 hours ago) and read 4686 times:
Quoting musang (Reply 15): I know you were referring to wing speed brakes
Correct. I flew a Sabreliner for a while with the speed brake on the underside of the fuselage and there was no restriction for obvious reasons. We used to just crack it open on app to help keep the power spooled up. On 727, dc-10, md-11 no-no. In fact on the -11 if you extend the flaps with the speedbrake deployed you get a warning.
musang From United Kingdom, joined Apr 2001, 872 posts, RR: 6
Reply 19, posted (4 years 10 months 6 days 1 hour ago) and read 4467 times:
Quoting TupolevTu154 (Reply 6): on a BA RJ100 and as soon as the flaps started to extend the noise could be heard very loud in the cabin. I guess it's the exhaust being disturbed by the extendig flaps.
Made an enquiry - its know as "flap hoot" in BAe, and comes from the gaps in the flap track fairings/canoes/boats/call them what you will, as they start to open on extension. As the gaps expand, there comes a point where the whistling stops.
146s had brush seals at the flap track on the fuselage wing root. On the RJ series these were replaced by a three stage telescoping plastic seal which kept the slot fully covered. It made little difference though, as most of the noise came from the canoes. If these seals stuck in the open position we could depart according to the CDL with no time limitation if I remember correctly.
Getting back to A320s, the short whistle I hear as they fly overhead (at an estimated 8 to 10,000 feet based on their position) reminds me more of the 146/RJ sound than anything engine related. I asked a 320 crew at work the other day - they were not familiar with the sound, so I guess that tells us its not audible from the F/deck.