Why do some a/c 'scream' in at high speed e.g STUKA bomber?

[Capt. Manuvar]

What is the exact cause of high picth scream you hear in diving aircraft e.g Stuka Bomber?
Is it true that some stukas were fitted with whistles/horns to make the scream louder for psychological effect?
Sometimes you can hear a similar whine when listening to an airliner flying overhead, is this related to the high speed screaming sound?
Thanks for any replies
capt. manuvar

[LowNSlow]

The JU-87 Stuka was fitted with sirens. The P-51 Mustang also makes a whistling noise due to the open gunports on the wings. The Meteor and the Javelin made a wonderful "blue note" for the same reason.

I think it's the older airliners with turbojets rather than the more modern turbofans that make the whistling noise. This is due to the higher volume of high speed hot air passing through them compared to turbofans which have a mass of slower moving cold air surrounding the hot air. I think.

[shortstripper]

If I was some poor unsuspecting aeroplane that was suddenly pointed straight at the ground by the idiot at my controls, I'd probably scream too! ;)

SS

I suppose the ones that don't scream are made of sterner stuff :E

SS

[Capt. Manuvar]

Thanks for the replies. I've heard a similar sound comng from an aerobatic aircraft (pitts or extra, can't remember the exact type).
Capt. M

[CavoBlue]

Reckon LowNSlow hit the nail on the head regarding the diving aircraft.
N just a bit of useless info...think you'll find that the high pitched part of the jet noise from the airliner overhead is due to the fan airflow hitting the stators, same as what you hear when the donks wind up.

[747FOCAL]

You want to hear ringing, get under the flight path of an RB211 at low power and have the bleeds open up. That will wake you up for sure. :E

Some of the "screaming" noise from prop powered aircraft come from the tone shift in prop tip noise caused by more of the tips going supersonic because of the dive.

[AerBabe]

The full debate on the P51 can be found here (http://www.pprune.org/forums/showthread.php?s=&threadid=99542).

[Final 3 Greens]

Capt M

The BAe146/Avro RJ produces a whistling sound, whilst the flaps are travelling, due to aerodynamic factors.

The 146 is more noticeable, as the later RJ had mods to address this 'banshee' imittion, which is quite amusing so long as you knwo the joke (scares the sh@t out of nervous pax.)

[Saab Dastard]

I remember a documentary a couple of years ago about the design of the airbus a380 - the designers were very concerned about airframe noise.

Apparently the vast majority of noise generated when a modern turbofan airliner lands is due to airframe noise, as there's lots of draggy stuff hangin' out! (note technical terms ;) )

Surprised me then, but it makes sense.

SD

[747FOCAL]

The 747 is about 101 dB on approach at cert altitude with all engines off. All of that is airframe noise. A380 should be roughly the same.

[av8boy]

The 747 is about 101 dB on approach at cert altitude with all engines off. Show me.

:)

[JABI]

At least that was Hitlers idea for the Stuka dive-bomber, specially added air horns to increase the terror levels for those being on the receiving end.
Some airplanes actually have a more damaging noise level when heard from the front than the rear, eg the F16 has a higher pitched (more damaging) noise signature when heard from the front.
Think it had to do with the first row of stator vanes or compressor vanes.....
On certain types of Citations they have recently added a little "lip" to the air intakes low on the engine cowling (cooling air for something) to prevent a very high pitched whine as reported by pilots.
So it can be pretty much anything, engine noise/ intake noise/airframe noise...

[747FOCAL]

av8boy,

if your making a joke by asking me to coast in a 747 with all engines off..... haha very funny.

If your serioulsy doubting me than haha on you. There is nothing about the 747 noise certification that I do not know. :p

[av8boy]

The former, not the latter. I was hoping to be clear on that point but sadly I don't always seem to be successful... :(

I considered saying "prove it" (better effect if you knew it was a joke), but erred on the side of caution.

Now that we got THAT out of the way, when's the demo? I promise I'll bring my camera! :O


At least that was Hitlers idea for the Stuka dive-bomber, specially added air horns to increase the terror levels for those being on the receiving end.
The USAF continued this philosophy with the T37. The "tweet" screamed like a banshee (is that non-PC? I worry sometimes about the under-represented banshee constituency), striking terror into the hearts of Undergraduate Pilot Training trainees...
:D

Dave

[GlueBall]

You could also generate lots of decibels in a DC8-62/63 with the inboard reversers at full power stop, and the outboards at reverse idle detent during descent with the gear down. :(

[Diesel8]

Ahh Glueball, so it was you who discovered the 80% loss of aileron effectiveness with the outboards in reverse:)

[Sliding member]

Back to Capt M's first post, he mentioned airliners overhead. Sometimes whilst out I hear a whining sound, quite low pitched, from them which comes from nowhwere as the a/c is just about overhead, normally when a/c is at a lowish level (10k' ish +?) Sounds quite dramatic and makes me look, is it just atmospherics etc or when a/c throttled back?