Two questions regarding 737 sound

[sho69607]

Hello, 

I have a couple questions regarding sounds.

1.) Is the engine roar you hear in the sim what you actually hear in the cockpit of a 737 during takeoff? Realistic or not, it sounds absolutely amazing! That and the extremely loud pack noise which 737's are known for. 

2.) Is it normal for the pack noise to get louder as you increase thrust? I especially notice on the ground when taxiing.

[Litjan]

Hi,

yes, the sound of the engines is realistic - when we got noise cancelling headsets in our cockpit I always slipped them off my one ear during take-off and landing so I could hear the engines better - especially during approach I found that it really helps if you can hear the engines wind up and down. During cruise it really helps to have those headsets, though - the airconditioning (and airflow at higher speeds) is really loud. Note that we have a preference slider for the aircon sounds - a lot of people are bothered by the sound (I wish we had that slider in the real aircraft, too!!)

The airflow from the packs will modulate with the bleed pressure available. There are basically two spots where bleed air gets drawn from the engine, one is called the low-pressure bleed (5th compressor stage) and the other is the high-pressure (9th compressor stage). The modulating and shutoff valve controls how much high-bleed air pressure gets drawn - it opens during low engine RPM to allow more high pressure air, otherwise the bleed pressure would drop too much and you would have a problem supplying the packs and/or anti-ice systems during high altitude flight and idle power, for example.

When you have the engines at idle, this valve is pretty much fully open - now the engine RPM governs how much bleed pressure there is (you can see this on the pressure indicator, too). The airflow is a function of bleed pressure, so at idle it will modulate with the engine RPM. Once the pressure gets high enough, that little valve says "ok, this is enough pressure, I am gradually closing now" - and you can see the pressure stay static at that point, even if you increase RPM further.

Cheers, Jan

 

[sho69607]

15 hours ago, Litjan said:

Hi,

yes, the sound of the engines is realistic - when we got noise cancelling headsets in our cockpit I always slipped them off my one ear during take-off and landing so I could hear the engines better - especially during approach I found that it really helps if you can hear the engines wind up and down. During cruise it really helps to have those headsets, though - the airconditioning (and airflow at higher speeds) is really loud. Note that we have a preference slider for the aircon sounds - a lot of people are bothered by the sound (I wish we had that slider in the real aircraft, too!!)

The airflow from the packs will modulate with the bleed pressure available. There are basically two spots where bleed air gets drawn from the engine, one is called the low-pressure bleed (5th compressor stage) and the other is the high-pressure (9th compressor stage). The modulating and shutoff valve controls how much high-bleed air pressure gets drawn - it opens during low engine RPM to allow more high pressure air, otherwise the bleed pressure would drop too much and you would have a problem supplying the packs and/or anti-ice systems during high altitude flight and idle power, for example.

When you have the engines at idle, this valve is pretty much fully open - now the engine RPM governs how much bleed pressure there is (you can see this on the pressure indicator, too). The airflow is a function of bleed pressure, so at idle it will modulate with the engine RPM. Once the pressure gets high enough, that little valve says "ok, this is enough pressure, I am gradually closing now" - and you can see the pressure stay static at that point, even if you increase RPM further.

Cheers, Jan

 

Wow thanks for the detailed explanation on all this! I have flown the NG series a lot on p3d, so having the chance to see a detailed model of a 737 classic on X-plane shows how very different the two generations of aircraft are. This is only based on sim experience, but I am sure the two aircraft feel quite different to fly in the real world. One thing I noticed is the VNAV decent is not quite as precise in the -300 as it is in the NG series. Maybe this is by design? I often have to use FLCH or V/S to meet altitude restrictions.

Edited August 7, 2020 by sho69607

[Litjan]

I would think that the "feeling" of flying the 737-300 and the NG (at the same weights) is pretty much the same - not having flown the NG in real life. I know that our 737 feels exactly like the 737s I flew in real life.

Our VNAV is likely not as refined as the one on the PMDG. It (and some other FMC features like HOLDS, PROG page,...) is slated for improvement but was never really completely working.

Here are two threads I made specifically for prospective buyers and to get new customers up to speed on the current status:

Cheers, Jan

 

[sho69607]

1 hour ago, Litjan said:

I would think that the "feeling" of flying the 737-300 and the NG (at the same weights) is pretty much the same - not having flown the NG in real life. I know that our 737 feels exactly like the 737s I flew in real life.

Our VNAV is likely not as refined as the one on the PMDG. It (and some other FMC features like HOLDS, PROG page,...) is slated for improvement but was never really completely working.

Here are two threads I made specifically for prospective buyers and to get new customers up to speed on the current status:

Cheers, Jan

 

The aircraft is far more usable than it was initially that's for sure. The VNAV thing is a small issue for me as there are other ways to plan a descent if needed. The immersion factor and sounds are by far some of the best I have seen in flight sims though!

[SteamingSpoon]

Hi,

I just picked up the 737 on sale and having been an XP user for the better part of a year now I can definitely say I'd been missing out without the IXEG. This is a really well made airplane -- and after two flights I haven't faced any issues. 

However, the sound on engine startup (default sounds) seem to be WAY too loud - specifically the dry motor spool before lightoff at 25 N2. It sounds okayish in the cockpit, but as soon as I shift to a cabin view on startup it feels as if someone's brought a sputtering lawnmower within a foot of my ears. Add to that the fact that the packs are off so the sound feels even louder. This is in contrast with the normal idle/high thrust/cruise sounds which definitely sound more more accurate. I can record a small video to demonstrate this, but hopefully you guys are aware of what I'm talking about! Other than that, no major issues and complaints and I'm really happy I picked up this airplane!

[Litjan]

Hi,

this sounds (haha) definitely weird. The starter of the CFM56 is a turbine that is powered by compressed air (usually from the APU) - so it should be a loud "woosh" as if someone punctured a highpressure gas bottle. Definitely not a lawnmower...

There is a "sawtooth" sound at low RPMs that is emulating the grating and low-freq vibrations you can feel when the engines just start turning.

I have to doublecheck the sound in the cabin - I have not done so yet, I think - only listened to the startup from the cockpit (try with the windows open!) and from the outside camera.

That being said - we are in the process of moving sounds to FMOD (from OpenAl) and that should cure a lot of the "sound curiosities" we still get from time to time.

Cheers, Jan