Undercarriage warning horn at +7 psi boost - early onset when throttle moved back

[grafspee]

3 hours ago, some1 said:

 To obtain +7 boost in Mosquito's Merlins on the ground in DCS you need roughly 26% of joystick input.

- To obtain 44 inHg in Mustang's Packard Merlin on the ground in DCS you need roughly 37% of joystick input. (44 inHg is equivalent to +7 boost)

That alone raises an eyebrow. 

 

For me it does not, different boost regulator different supercharger gearing, different engine rpm when running 7lbs boost on the ground.

For me this only says P-51 /= mosquito.

I think this warning sound also informs pilot that he operate engines below single engine power requirement, very useful when flying low, but this is only my guessing, this is why horn sounds very early, unlike P-51 when horn fires up when throttle is closed, in case P-51 it reminds to drop landing gear   

Edited October 17, 2021 by grafspee

[Art-J]

+7 @ 2650 is for "max continuous", but I've noticed that at least in cruise flight at low altitudes, one can get down to +4 PSI without triggering the sound just by using much lower RPM. About 2000 will do.

[some1]

1 hour ago, grafspee said:

For me it does not, different boost regulator different supercharger gearing, different engine rpm when running 7lbs boost on the ground.

For me this only says P-51 /= mosquito.

You're coming up with even weirder guesses why it's supposed to work like that.

My point is, we don't know. It's hard to obtain reliable data on this subject without actually flying the airplane, and even ED/TFC doesn't have one AFAIK. 

[grafspee]

3 minutes ago, some1 said:

You're coming up with even weirder guesses why it's supposed to work like that.

My point is, we don't know. It's hard to obtain reliable data on this subject without actually flying the airplane, and even ED/TFC doesn't have one AFAIK. 

This is my point as well, if ED would not research this topic deep enough or didn't have time or desire to do it, they would copy paste throttle from spitfire or P-51, so when they put some effort in modeling this and it behave different then one in P-51.

[some1]

20 minutes ago, grafspee said:

if ED would not research this topic deep enough or didn't have time or desire to do it, they would copy paste throttle from spitfire or P-51

Actually, I just checked and it looks like copied from Spitfire. +0 is at 17% throttle, +7 at 26% throttle, and at 50% throttle both aircraft make around +11 boost. 

Different supercharcher system (2 stage vs single stage), different carburetors, different linkage, same throttle. Magic, or super powerful boost regulator. 

Edited October 17, 2021 by some1

[grafspee]

11 minutes ago, some1 said:

Actually, I just checked and it looks like copied from Spitfire. +0 is at 17% throttle, +7 at 26% throttle, and at 50% throttle both aircraft make around +11 boost. 

Different supercharcher system (2 stage vs single stage), different carburetors, different linkage, same throttle. Magic, or super powerful boost regulator. 

 

Maybe they did.

Maybe Merlin 66 and 25 share same boost regulator and V-1650 has different boost regulator.

Edited October 17, 2021 by grafspee

[some1]

The Merlin Boost regulator wasn't that powerful. It did not work at all at 0 PSI or below. 

Here's a nice description what it could do and what not. https://www.enginehistory.org/Piston/Rolls-Royce/R-RmerlinABC/R-RmerlinABC.shtml

Edited October 17, 2021 by some1

[grafspee]

I know that in p51 boost regulator kick in at 41inch. Late p51b got boost regulator with regulation range starting from 26inch or so. Apparently dcs p51 is mix of early/late version.

Edited October 18, 2021 by grafspee

[Nealius]

19 hours ago, Art-J said:

I've noticed that at least in cruise flight at low altitudes, one can get down to +4 PSI without triggering the sound just by using much lower RPM. About 2000 will do.

That's roughly in line with cruise power, isn't it? 1800-2200/+4?

[Holbeach]

Eco cruise at sea level is 2300 rpm @ 4 lb boost.

I doubt they did that for 200 miles, with the horn blowing.

 

..

[ac5]

3 hours ago, Holbeach said:

Eco cruise at sea level is 2300 rpm @ 4 lb boost.

I doubt they did that for 200 miles, with the horn blowing.

 

..

Very doubtful indeed.....

[Art-J]

11 hours ago, Nealius said:

That's roughly in line with cruise power, isn't it? 1800-2200/+4?

Yes, although my previous "low altitudes" comment needs a revision I admit, with "low" being a relative term (especially when flying on Nevada map! ). On Caucasus one in a free flight mission, +4  @2300 suggested by Holbeach is possible only above 5500 ft, cause that's where throttle levers are forward enough. 

Edited October 18, 2021 by Art-J

[NineLine]

From our Mossie SME "the gear horn switch is mounted 3/4s of an Inch or an Inch off the throttle stop"

[some1]

2 hours ago, NineLine said:

From our Mossie SME "the gear horn switch is mounted 3/4s of an Inch or an Inch off the throttle stop"

And what boost does the engine produce 3/4s of an inch from the throttle stop? Is that a Mosquito engine? Right now we have the exactly same boost at partial throttle positions in DCS Spitfire and Mosquito,  even though the induction system in those engines differs a lot. 

[gulredrel]

*bump* Stumbled across this thread after installing trial version.

I don't question that the warning horn button is mounted at the position described above. But I highly doubt that this throttle position corresponds to +7 boost at ground level.

Hope this can be reviewed again.