reported 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.

[Andurula]

nullThe throttle position when the gear warning horn goes off and the throttle full aft.  That is a lot more that 1/4 inch.  The warning horn off position also corresponds with 7 inch of boost which can't be right.

[VampireNZ]

ED do seem to have nailed the actual Mozzie manual well in that "The undercarriage warning horn sounds when the main wheels are not locked down and the throttles are less than 1/4 open" - as using the VKB config software my throttles are outputting exactly 25.0% at the warning horn (note it must be BOTH throttles at 1/4 or below to sound horn).

However, there definitely seems to be something funky going on with how much boost is being applied at low throttle openings! Watching the formation flying of of Mozzie KA114 fitted with Merlin 25 engines in Auckland and you can catch a glimpse of the boost gauges sitting around 0 lb boost and he is just dropping in and out of the horn with the throttle pretty much stood up - prob dropping into the negative boost area to slow it up now and then. (non-historic boost gauges but 0 lb boost is still at 12'oclock.) He looks to be flying around 180 MPH - but don't know if he has a little flap out or not - prob not. Doesn't really matter as it is more the throttle postion to boost output ratio that is the problem, not how much power it has.....that's for another post lol. 

But definitely not sitting up at 7 lb and dropping in and out of the horn as we are in DCS!

Something else quite strange is how there is no manifold change or effect on the engine at all during flight in the DCS Mozzie for the first 1/2" or so of throttle travel. then it jumps up to 0..then races around to 8 at very low throttle settings? This would definitely have an adverse effect and also indicate that the throttle/boost curve is not quite right.

I have attached the ref vids below - first one is quite dark so only catch a glimpse of the settings, but it is stable flight the whole time as he is in formation. Second vid is in same aircraft with much better view of gauges. Interesting to watch the takeoff and how the manifold pressure reacts at certain throttle settings. Also interestinig to note in second vid he is flying around at -1 boost at around 180 MPH - no warning horn.

EDIT: Was also thinking this could be related to why the DCS Mossie throttle stops are located at +14 lbs, instead of the actual figure for the Merlin 25 of +12 lbs.

 

 

Further to the above - I have also included the boost curve info for reference/comparison purposes. Firstly some information from the Merlin engine manual regarding the PROGRESSIVE boost cam.

Below is what I would consider a reasonable boost/throttle position progressive curve that more closely matches what can been seen in in-flight videos of the Mosquito - I note this is not specifically based on any info as I have been unable to find any. However, you will note it is a lot more likely example of a PROGRESSIVE boost curve than that shown in the second graph in red - which is what we currently have in DCS. All figures taken from a Mosquito at Channel map at 1,000'.

I think most people would agree the Blue curve would be much more likely than the Red curve for a progressive relationship between throttle position and boost - and would also enable lower power settings that don't require the throttles to be below 25%. I specifically note the settings for 0 lb boost as seen in one of my ref videos just skirting the upper limit of the 25% mark.

 

I realise the Mosquito doesn't really get any attention regarding development any more - but as a Kiwi I feel it is my obligation to try and fix her up lol. I understand ED may not have the available manpower to address the issues with the Mozzie and would happily change the values myself if ED would point me in the right direction.

Edited February 9 by VampireNZ

[Nealius]

It seems like, with enough research and calculating, we could come up with a user-defined slider curve to fix the throttle range at the user level while we wait for ED to address this, though with the default curve I notice that the throttle stops engage right at my physical AB detent on my Warthog throttle.

[Skewgear]

Maybe someone could email Avspecs and ask how the throttle cables and quadrant are set up on the real thing?

From memory, the Merlin 60 series doesn't have any non-linearisation features for throttle response (i.e. cable movement and action at the carburettor is directly proportional to quadrant input). I'll have a look through the Merlin 24 manual in a bit.

[Andurula]

The problem is the horn is on at +7 boost.  No amount of throttle control curve or saturation is going to fix it.

How the cable is rigged to the carburetor is not important.  The important part is rigging the warning horn switch correctly.  At the moment it is not.

This is a software fix, not a systems modeling fix.  They don't model the systems in THAT much detail.

[NineLine]

FYI, this was reported a while ago, just not addressed internally, yet. Thanks. 

[Chipwich]

I fly the DCS Mossie often and IMHO, the landing gear horn is a non issue.  As a post mentioned earlier, the trick is to set boost just above the horn, then modulate your airspeed with small movements of the RPM/propeller pitch controls. When flying single player, it seems that that AI are flying at or just below an airspeed that induces the horn, but again, a simple drop in RPM, lets you fly in formation with the AI horn free until the tanks run dry.  Not a problem in multiplayer unless your flight lead is damaged or asleep.  During approach to landing, you are going to have to deal with it until you get the gear down, but that's pretty comparable to a friend's Arrow that I fly IRL.  And although the horn is annoying (it's meant to be), there is no damage going on. Piper installing that horn in the Arrow was a good thing and has saved many an owner some embarrassment and needless expenditure.

That is not to say that the DCS Mosquito is perfect, but it hits the mark in so many places that you do yourself a disservice allowing something as simple as the gear horn interfere with your enjoyment.  And watching in cockpit videos of flying Mosquitos, I'm not sure that it's wrong.

[VampireNZ]

On 2/18/2025 at 2:21 AM, Andurula said:

The problem is the horn is on at +7 boost.  No amount of throttle control curve or saturation is going to fix it.

How the cable is rigged to the carburetor is not important.  The important part is rigging the warning horn switch correctly.  At the moment it is not.

This is a software fix, not a systems modeling fix.  They don't model the systems in THAT much detail.

&

8 hours ago, Chipwich said:

I fly the DCS Mossie often and IMHO, the landing gear horn is a non issue.  As a post mentioned earlier, the trick is to set boost just above the horn, then modulate your airspeed with small movements of the RPM/propeller pitch controls. When flying single player, it seems that that AI are flying at or just below an airspeed that induces the horn, but again, a simple drop in RPM, lets you fly in formation with the AI horn free until the tanks run dry.  Not a problem in multiplayer unless your flight lead is damaged or asleep.  During approach to landing, you are going to have to deal with it until you get the gear down, but that's pretty comparable to a friend's Arrow that I fly IRL.  And although the horn is annoying (it's meant to be), there is no damage going on. Piper installing that horn in the Arrow was a good thing and has saved many an owner some embarrassment and needless expenditure.

That is not to say that the DCS Mosquito is perfect, but it hits the mark in so many places that you do yourself a disservice allowing something as simple as the gear horn interfere with your enjoyment.  And watching in cockpit videos of flying Mosquitos, I'm not sure that it's wrong.

The main problem is not the horn - it is the fact Boost climbs FAR too quickly based on throttle position - i.e. you are only at 25% throttle position or slightly below (hence yes you get the annoying horn) but pulling +7 boost, which is completely ridiculous. Your RPM setting in the Mosquito is not determined by the silencing the gear warning horn - it is set by engine parameters/performance/longevity. My blue line graph above is even still a bit 'loose' on boost as further investigation revealed that you were even further into the throttle travel at +0 boost than the 28-ish % I show.

So I re-iterate - it is NOT letting something as 'simple as the gear horn interfere with your enjoyment" - yes I know that is the OP, but that is just a nasty by-product of completely fantastical throttle/boost/engine mapping characteristics of the DCS Mosquito at the moment, that yes is hampering the enjoyment of this product I purchased somewhat. If I wanted arcade fantasy simulation I could play a different arcade flight sim. Could it be fixed - of course.....we shall see.

[Chipwich]

@VampireNZ, maybe the Mossie just got patched.

Never mind.  This was just me flying at 8,000 ft., requiring higher throttle to achieve boost.  I tried again at sea level and 1/4 is getting 7 lb boost.

 

I flew the Mossie and Spit back to back to back today to compare their engine performance, and at least at 2700 RPM and just under 4 lb boost, the two aircraft are identical at 26% throttle on my VPC T-50CM3 throttle.  The Mossie gear warning horn is correctly coming on at 25% throttle, but boost is now just below 4 lb. See image below 3.9 lb, but horn has not sounded yet as indicated by the two red lights on the gear indicator being out.

Mossie @ ~ 26% throttle.

 

Spitfire @ ~ 26% throttle.

 

Edited February 21 by Chipwich

[Andurula]

On 2/18/2025 at 7:34 PM, Chipwich said:

I fly the DCS Mossie often and IMHO, the landing gear horn is a non issue.  As a post mentioned earlier, the trick is to set boost just above the horn, then modulate your airspeed with small movements of the RPM/propeller pitch controls. When flying single player, it seems that that AI are flying at or just below an airspeed that induces the horn, but again, a simple drop in RPM, lets you fly in formation with the AI horn free until the tanks run dry.  Not a problem in multiplayer unless your flight lead is damaged or asleep.  During approach to landing, you are going to have to deal with it until you get the gear down, but that's pretty comparable to a friend's Arrow that I fly IRL.  And although the horn is annoying (it's meant to be), there is no damage going on. Piper installing that horn in the Arrow was a good thing and has saved many an owner some embarrassment and needless expenditure.

That is not to say that the DCS Mosquito is perfect, but it hits the mark in so many places that you do yourself a disservice allowing something as simple as the gear horn interfere with your enjoyment.  And watching in cockpit videos of flying Mosquitos, I'm not sure that it's wrong.

My "annoyance" is not that you can't use the Mossie with the gear horn not operating correctly.  My annoyance is that you can't fly it the way the aircrews in WWII used to fly it.  If you use typical cruise settings, as has been written by many sources, the warning horn is on.  Of course you can push the throttle up and fly faster but you give up the range and endurance that real Mossie crews worked with.
 

In the end, it is a sim versus game thing.  If you don't care about flying an accurate model in an accurate matter - and honestly most DCS players don't and that's okay - then it is a very minor quibble.