Good evening all.One thing that is always amazingly prominent to me when flying on a 737 is the sound of the engines spooling up. As an example watch this video and fast forward to 5.20, and when the engines spool up to increase taxi speed that amazing "whoosh" sound can be heard. http://www.youtube.com/watch?v=o8Oa2wE4_yMIf I recall correctly the sound is heard when the engines spool up to a certain percentage, but when the engines stabalize at that percentage the sound dissipates.Can anyone tell me what it is and what causes this as I've never experienced it on any other aircraft? Cheers.

If I heard that on any aircraft I was flying on I'd wanna get off ;) seriously tho the CFM56 is equipped on many types. I fly on the A320 and 330 a lot for business, both aircraft types in the airlines fleet use a varient of the CFM56, however I always book a seat in front of the engines as the sound is amazing from that angle. Maybe that's why I've never heard it.

however I always book a seat in front of the engines as the sound is amazing from that angle. Maybe that's why I've never heard it.

See your just lucky you can actually book a seat on a 737! Its always been ryanair or easyjet for me who operate a free seating policy. I usually end up taking the rear set of stairs to avoid the mad crowd surge at the forward stairs meaning I usually end up over the wing! :(

I just asked our resident engine mechanical expert Paul about this - he's literally sitting on an NG at FL400 right now and of course he knows the answer:It's the VBV (Variable Bleed Valve) - it dumps air off the compressor while the engine is accelerating or decelerating to help avoid a compressor stall.

Nice.

I just asked our resident engine mechanical expert Paul about this - he's literally sitting on an NG at FL400 right now and of course he knows the answer:It's the VBV (Variable Bleed Valve) - it dumps air off the compressor while the engine is accelerating or decelerating to help avoid a compressor stall.

Thanks very much Ryan!

Ryan,I've never heard a true answer on this before! When fueling aircraft, I always heard this from the 737. However, it seems like it's only the classics. I've never heard this from a NG before. It's an awesome sound that's very distinct and prominent.For what it's worth, PMDG's first NG, I always used Dres Braabens (sp) sounds. They have this unique whine too!

Ryan,I've never heard a true answer on this before! When fueling aircraft, I always heard this from the 737. However, it seems like it's only the classics. I've never heard this from a NG before. It's an awesome sound that's very distinct and prominent.For what it's worth, PMDG's first NG, I always used Dres Braabens (sp) sounds. They have this unique whine too!

Hi, where can I download this unique special sound set for the 737 ? Thanks in advance, Pascal

I just asked our resident engine mechanical expert Paul about this - he's literally sitting on an NG at FL400 right now and of course he knows the answer:It's the VBV (Variable Bleed Valve) - it dumps air off the compressor while the engine is accelerating or decelerating to help avoid a compressor stall.

One little question... Would that been modeled?

It's hard to get it completely right without fully bypassing the FS sound system for engine sounds (which we might do in the future), but yes something that sounds close should be there. The CFM56-7B on the NG doesn 't make this sound nearly as prominently as the CFM56-3 on the classics does though - I paid really close attention to this on a bunch of SWA flights I've been on recently and it happens all the time with slight power changes on the classics but pretty much only as the engines are brought up just before takeoff on the NGs.

Depends if it's audible in the cockpit I guess...

The CFM56-7B on the NG doesn 't make this sound nearly as prominently as the CFM56-3 on the classics does though - I paid really close attention to this on a bunch of SWA flights I've been on recently and it happens all the time with slight power changes on the classics but pretty much only as the engines are brought up just before takeoff on the NGs.

I concur, It does make it though, and perhaps I just had "ear out" for it but It was always clearly heard externally after I finished pushing a NG out of the gate and they would apply thrust to get moving. If onboard any time the throttles were moved from idle to a mild taxi thust this could be heard.

Depends if it's audible in the cockpit I guess...

Oh its audible alright, I have flown jumpseat on numorious occasions, its much quieter but you can defianatly hear in the flightdeck. It was also replicated in the CAE NG full motion sim. When travelling in the cabin I found it could be heard better if your seated forward of the N1 blades. And after working on the ramp with NGs day in and day out I found this to be the biggest characteristic of the way the NGs sound. Its music to my ears :) and one of about seven hundrend and thirty seven reasons why the NG is my favorite aircraft. Oddly enough, I never had any successful attempts at truly capturing that sound with any camera I had. And it seems after going several youtube videos, seems I'm not the only one.

Oh its audible alright, I have flown jumpseat on numorious occasions, its much quieter but you can defianatly hear in the flightdeck. It was also replicated in the CAE NG full motion sim. When travelling in the cabin I found it could be heard better if your seated forward of the N1 blades. And after working on the ramp with NGs day in and day out I found this to be the biggest characteristic of the way the NGs sound. Its music to my ears :) and one of about seven hundrend and thirty seven reasons why the NG is my favorite aircraft. Oddly enough, I never had any successful attempts at truly capturing that sound with any camera I had. And it seems after going several youtube videos, seems I'm not the only one.

It is a beautiful sound! Glad that it can be heard from the cockpit so PMDG have no choice but to implement it... :(

Listing to the engine from a passenger point of view must of been some treat.....:(

Thanks for info Ryan!!Looking forward to it!!