The A2A Simulations Community

Agree.

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Nice find!!! I hope you're right!!!!

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Patrick

Attaching the sound to RPM is not the right way to do this. While Prop RPM is a component of how much sound is generated by the prop, just as much of the sound is determined by the prop pitch. A perfect example of are turboprop aircraft powered by the Allison 501D / T-56 and its later RR AE2100 derivative. These engines and props are direct-drive turboprops, thus they operate a lot like a piston engine. The only thing that changes with throttle movement is the prop pitch to take the additional torque and thus provide more power. The difference in sound is massive as the big Aeroproducts Constant Chord (CV-580, C-130A-E & L.188), Hamilton Standard Hydromatic (C-130H, P-3, and CV-5800), or Dowty-Rotol (C-130J) props move to accept the power of the 4000+ HP engine behind it.

Additionally, the ENGINE tone on a piston or jet aircraft will change independent of prop RPM as additional power is added. It tends to get a deeper tone even with the same RPM being provided by the prop. Consequently, when reduced towards (and to) idle, the engine tone tends to "lighten" as the load is removed from the crankshaft.

BTW, comparing cars to airplanes never works. Two totally different theories behind operation, two totally different methods of propulsion being dealt with, so just because something goes one way in a car small-bore, low compression gas engine, don't expect it to translate to a large-bore, high compression aircraft piston engine in any way.

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CAPflyer you are absolutely right, was my thought too. Hope to hear this differences maybe in the first patch..

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FSX SP2 DX9.Addons:FSG2010,REX OD, AS2012, PMDG, DA Do27, Dodosim, A2A accusim all, Katana4X,Coolsky DC9 Classic, Swiss Pro,ORBX all, Fly Tampa, DRZEWIECKI DESIGN, FS Dreamteam, FranceVFR Haute Normandie 3D...

Hi CAPflyer,

you are right regarding the different sounds of Prop and Engine (Combustion, various mechanical and Gas charge and discharge noises). But in terms of compression, we should not mix up the compression ratios and the reasons because of choosing different ones for car and airplane engines. The compression ratios of airplane engines are often much lower than the ones of car engines. There are different reasons for this. One reason is that smooth running is very desirable for aircraft engines to relieve the bearings and gears. Another reason (applies for the early GA engines) is because they need to be able to be started by hand, and by windmilling in flight.

If you compare the compression ratio of an average natural aspired aircraft engine (O-360 5,9L: 180HP: 8,5) and a typical natural aspired car engine (2,8L VR6: 174HP: 10,0) the car has higher compression ratio. This is just an example, of course you need more parameters to get the higher specific power output of the car engine, and of course I know that car engines see a MUCH lighter load spectrum over their lifetime. If you use a car engine with exactly the same load spectrum of an aero engine, it would come apart pretty soon

Charged engines, no matter if cars or airplanes, need the lower compression ratio because of the "knocking" (detonation) limit. The RR Merlin V12 for example was 6,0 compressed. What stresses an engine is the BMEP, not the compression ratio. The lower the BMEP, the longer the engine will last.

I hope, this was not too off-topic. The Info above is partly taken from my own experience and daily work during turbocharger development, and maybe someone knows more about aircraft engines and can add something.

Best Regards,
E.

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Hello,

Very interesting information about the engines and I agree about the sound difference, you not only have the engine sound changes but even louder than that sometimes is the prop cutting through the air especially untill it unloads and where your standing in relation to the plane, I really like that sound, and the smell too Looking for that Spitfire soon.

See ya, Rockitglider

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Capflier, although I'd like to see all the details you explain implemented regarding engine+prop sound, I'm happy if no longer I have to hear the engine idling during an aproach while the rpm needle points to 2450 rpm. It's obvious that an engine outputing let's say 1000hp will sound a lot louder and massive that the same engine with the throttle fully retarded even if the rpm are the same. What I find annoying is how fsx does it all wrong and uses de same 'sound logic' for engines with variable and fixed prop pitch.
If A2A models all the complexity of the sound that comes out from an engine at different rpm and at different work loads that would be optimal, but if they have made a simpler model at least it's a beginning and we know how they improve everything release after release.

It seemed that nobody cared about that idle sound at high rpm (the most obvious situation), I'm glad to see I was not alone.

Crim, 2 questions -

1) What FSX aircraft specifically are you talking about?

2) How much real world experience do you have?

The reason I ask is because none of the default FSX aircraft operate incorrectly as far as sound goes. You pull the throttle on a 182 back to idle, and all you hear is wind, even with the prop potentially turning at 1200+ RPM. I've not seen an engine that will "idle" with the prop still doing 2400+ RPM. If you're talking "flight idle", then yes, you should still hear some engine sound, but it's not going to be much nor is there going to be enough prop sound to overcome the wind in many cases.

One of the biggest misunderstandings out there for Flightsim is that people get the wrong idea about how a plane sounds up front from sitting in the cabin. Things sound totally different. In the cockpits of most jets, you don't hear the engines except on takeoff and during landing other than a dull background noise because the avionics and the wind overtake them. In single engine pistons, once the power comes back, the wind takes over the sound as well. On many twins, all you ever hear are the props (no engine noise), and when they "unload", even that sound is imperceptible over the wind.

Let me give you a good example of what I'm talking about, taken by me - http://www.youtube.com/watch?v=5-EDmjwl1i8

Note around 1:40 when the pilot pulls the power off. That's the WIND you're hearing, not the prop. The engine is not even at idle, but I can hear the gyros spinning more than the engine.

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I think you are telling the same thing than me but thinking that I'm saying the opposite.

For example, cruising with the P-47 the engine sounds like it is turning at 2100 rpm and outputing some good power. If you move back the throttle to the idle position, thanks to its constant speed prop mechanism, the number of turns of the engine in a minute will still be the 2100, that doesn't change as long as there is enough air ramming into the prop blades (I know you don't need all the details, is that I'm trying to be clear this time). What it's gone is the power output. But what you hear in FSX is the same slow paced *pop pop pop pop* of the engine idling at 1000 rpm, the very same sound it makes when the plane is sitting on the ground at 1000 rpm.

Take into account that I'm talking only of engines with constant speed props. Those are the ones I'm complaining about.

I had a PPL, but only have flown fixed pitch prop planes...

Bonjour,

Very nice update !

I just bought Spitfire WOP2 Solo few weeks before...
A2A offers ONLY 8 dollars discount and 5 dollars more for one bundle order (Accusim included)...excuse me, but such offer is not SERIOUS !!!

I think I will not buy this update for such poor offer. I have to pay AGAIN almost at full price for updating.

Sorry !

N.B. still have P47+Accusim+3D lights...

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Jean
PP on FS

Dude, for what you are getting, it's cheap in every sense of the word!

Even if they would price it to PMDG's standards, it would be well worth it!

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Lukas

Sorry Guy, but not for me ! in such terms, I must pay twice.

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Jean
PP on FS

EchoTango,

Please PM me your order info.

Scott.

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A2A Simulations Inc.

Can't wait of course, for the P-51 Mustang and the F-4 Phantom II with Accusim

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