[INVESTIGATING]Spool down sound only audible inside cockpit - ED Forums
 


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Old 09-13-2020, 09:50 PM   #1
Cornelius
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Default [INVESTIGATING]Spool down sound only audible inside cockpit

Currently the spool down sound is not audible
  • when the canopy is open
  • in the F2 exterior view
  • probably in Multiplayer from other players (could not test)


[Needs more clarification and then probably it's own bug report:]
Furthermore the spool down sound is audible during flight which shouldn't be the case as the fast deceleration solenoid is only activated with weight on wheels, if I'm correctly informed.
Attached Files
File Type: trk missing Spool downl.trk (150.9 KB, 4 views)
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Last edited by Cornelius; 09-16-2020 at 07:11 AM.
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Old 09-13-2020, 10:54 PM   #2
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+1 good call noticed that also
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Old 09-15-2020, 07:04 AM   #3
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When reporting bugs please add a short track replay showing the issue

thanks
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Old 09-15-2020, 11:07 PM   #4
vstolmech513
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Quote:
Originally Posted by Cornelius View Post
Furthermore the spool down sound is audible during flight which shouldn't be the case as the fast deceleration solenoid is only activated with weight on wheels, if I'm correctly informed.

The fast deceleration solenoid was removed and the cannon plug tied off almost 15 years ago. The spool down sound I believe you are referring to can be heard anytime that you retract the throttle from high RPM location to idle quickly. I will agree that the sounds are now horrible in the cockpit as they used to be pretty darn spot on. The only time you should hear the spool down sound is as the RPM comes down rapidly, like from max to idle in <2 secs. but it seems like any rapid retraction causes that spool down sound to play and mixed with the normal sound of the motor it sounds like a dying cat.
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Old 09-16-2020, 07:14 AM   #5
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trackfile added and the other topic separated in first post
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Old 09-16-2020, 07:50 AM   #6
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Quote:
Originally Posted by vstolmech513 View Post
The fast deceleration solenoid was removed and the cannon plug tied off almost 15 years ago. The spool down sound I believe you are referring to can be heard anytime that you retract the throttle from high RPM location to idle quickly. I will agree that the sounds are now horrible in the cockpit as they used to be pretty darn spot on. The only time you should hear the spool down sound is as the RPM comes down rapidly, like from max to idle in <2 secs. but it seems like any rapid retraction causes that spool down sound to play and mixed with the normal sound of the motor it sounds like a dying cat.
Okay. Thanks for clarification. Unfortunately i can't find any useful translation or explanation about what a cannon plug is*

As I understand it now you have to be on the ground to hear that sound, while in vertical flight it would mean that you are in free fall before you are able to hear it. In horizontal flight, the air which enters the engine will prevent a rapid reduction of the RPM anyway.

In my opinion this should be addressed together with the Engine Spool time and responsiveness and then probably get it's own bug report...

*
Spoiler:
Although I found this 4 years old photo. Description:"Marine Lance Cpl. Francis Reeves, assigned to 13th Marine Expeditionary Unit (MEU), inspects a T1 cannon plug on an AV-8B Harrier II on the flight deck of amphibious assault ship USS Boxer"

https://www.alamy.com/stock-photo-16...ip%3d0%26pl%3d

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Old 09-22-2020, 05:16 PM   #7
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Quote:
Originally Posted by Cornelius View Post
Okay. Thanks for clarification. Unfortunately i can't find any useful translation or explanation about what a cannon plug is*

As I understand it now you have to be on the ground to hear that sound, while in vertical flight it would mean that you are in free fall before you are able to hear it. In horizontal flight, the air which enters the engine will prevent a rapid reduction of the RPM anyway.

In my opinion this should be addressed together with the Engine Spool time and responsiveness and then probably get it's own bug report...

Sorry, just now seeing your reply. A cannon plug is just a connector from a wire bundle to a component. All they did was cut the wire, wrap it with a sleeve and tie it back on itself.



Your comment about horizontal flight preventing a rapid reduction of RPM is not correct. A jet engine will only spin as fast as the combustion section is burning a set amount of fuel that gets determined by the Fuel Metering Unit (FMU) which is set by throttle position, which in turn spins a turbine at the back of the jet. These are what actually spin the compressors (which is what sucks the air into the intake but only at the speed the turbine is spinning it at).



In the above image you can see the firewall in the middle of the picture (it's grey with a cutoff pipe coming out of it) with the High Pressure Compressor (HPC) just in front of it. The ring you see would be where the cold nozzle sits on the jet. Air cannot force itself into the compressor and make it spin faster nor can it keep it from slowing down. The turbines in the back are painted red to show where the hot exhaust gas is, and those are what spin the compressors in the front, not the other way around. If you add more gas (throttle up), the engine spins the turbines faster. Take gas away (go to idle), then it spins them slower.

Any air that is flowing into the intake that the engine does not need gets either pushed out of the intake or gets vented through what are called boundary layer doors on the inside of the intake (the flaps are spring loaded and circled in red below). These also prevent supersonic air from entering the engine, and vents the air upwards behind the canopy (if you look at the F2 view with the canopy open you can see the large white squares that are covered by the canopy when it's closed).



Now whether or not you can hear that sound on the ground or not in DCS externally or in the cockpit only should get looked at but has nothing to do with the thread that you linked. You can view my reply to that thread here and see that there doesn't seem to be anything wrong or modeled incorrect about the responsiveness or the spool time. The only real issue I can see is how long it takes to go from full throttle to idle. I clocked it at around 7-7 1/2 seconds where in the real jet it takes about 5-5 1/2. Almost every function of the engine and its acceleration and performance can be seen in this video of a high power:



These are just my findings and what I see on my end. Not meant to make anyone mad or take away from what you might be seeing on your end. Strictly for information only.
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