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Loving the new Mossie Monday Series. Well done.


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1 hour ago, grafspee said:

Some say that for initial roll right throttle is pushed a but further then left, once speed is gained all throttles for take off power.

 

Think you mean the opposite graf mate, otherwise you'd be definitely making donuts!

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@Nealius he used different way of take off, he hold brakes run up engines too full power then he shoots out  almost instantly to speed where rudder effectiveness is enough to ride straight. Pilot's notes for mossie mention that plane roll pretty straight at take off.

1 hour ago, DD_Fenrir said:

 

Think you mean the opposite graf mate, otherwise you'd be definitely making donuts!

Yeah 🙂 exactly Left throttle further then right 🙂 I was thinking about rudder 😛


Edited by grafspee
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4 hours ago, Nealius said:

I wish we had a controls indicator view on that takeoff. From another thread I understand the Mossie to have poor rudder authority at slow speed due to the lack of prop wash over the tail. This makes me wonder how we keep her straight on initial takeoff roll. In Sunstag's video I don't see any differential brake usage and I don't think he mentioned anything about leading one throttle ahead of the other either. 

Yeah there's a lot missing in that video. Clearing the engines (he mentioned it on the flaps) as well. Compared to that, I still facepalm in the startup video, when he puts an emphasis on how you enable the LEFT magneto switch FIRST! - as if that makes any sort of difference, while other things that were omitted most definitely would!

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I imagine it is to do with two things:

 

1:

 

Criticalengine1.jpg

 

So it is good practice to always start with the left engine. 

 

2:

Most multi engine aircraft take power from one engine, seemingly the left engine in most cases. So you will always want to run that engine first. 

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2 hours ago, Krupi said:

I imagine it is to do with two things:

 

1:

 

Criticalengine1.jpg

 

So it is good practice to always start with the left engine. 

 

2:

Most multi engine aircraft take power from one engine, seemingly the left engine in most cases. So you will always want to run that engine first. 

You got  it wrong. He states that they alternated which engine to start first to check on the vacuum pumps. I'm talking about which MAGNETO on either engine to flick up first - before even starting the engine.

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14 minutes ago, peachmonkey said:

So this is totally normal?  I'm just asking...

 

In all other sims (as well as in DCS A8) when the RPM gauges dance like that it means there's a serious problem with the engine.

 

 

IMG_i9hulf.gif

 

 

Take a look at this video. 

First run of Merlin 25 engine in 50 years! - YouTube

 

When the engine is running you can clearly see the RPM gauge (top left side of his panel in the video) jumping around, as it does in our Mossie, so I would say this behaviour is accurate. Why it happens I'm not sure, could be a vibration issue or indeed how the gauge itself works. If it gets it's signal from the ignition system it could be electronic noise causing it? I'm not sure.


Edited by bart
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33 minutes ago, bart said:

 

Take a look at this video. 

First run of Merlin 25 engine in 50 years! - YouTube

 

When the engine is running you can clearly see the RPM gauge (top left side of his panel in the video) jumping around, as it does in our Mossie, so I would say this behaviour is accurate. Why it happens I'm not sure, could be a vibration issue or indeed how the gauge itself works. If it gets it's signal from the ignition system it could be electronic noise causing it? I'm not sure.

 

 

I seriously doubt it's due to the vibration as that would reduce the lifetime of such a critical instrument. I'm trying to find the type of tachometer used in Merlins. There's:

  • fully analog mechanical with a flexible shaft from the crank all the way to the needle via gearing
  • analog + magnetic with a flexible shaft from the crank to the magnetized core, and the resultant magnetic field drives the face needle
  • electrical/speed sensor:  a magnet is located on a rotating shaft (crank or auxiliary) and a pickup contact that gets tripped by the revolving magnet

All 3 of those should be rather precise.

 

Now I wonder if this is somehow tied to the variable pitch propeller?  I.e. it constantly tries to adjust towards the steady RPM's but its mechanism has an intrinsic delay and therefore they are never fully in sync.

 

But none of the fluctuations make much sense from the point of normal and healthy operation of the engine.  Maybe it's vacuum based??

 

@NineLine, can you possibly unravel the mystery behind it?  😄

 

 

 

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1 hour ago, peachmonkey said:

So this is totally normal?  I'm just asking...

In all other sims (as well as in DCS A8) when the RPM gauges dance like that it means there's a serious problem with the engine.

 

Can't say it's correct but this Periscope Films de Havilland video shows similar RPM gauge behaviour from a Whitley Mk.V ? bomber with Merlin 10 engines.

 

 


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12 minutes ago, peachmonkey said:

I'm trying to find the type of tachometer used in Merlins.

 

To my untrained eye (from the Merlin 25 start up video) it looks like there's a cable drive shaft (running from the cam shaft) that drives a three phase ? tacho generator.

 

Mosquito Merlin 25.jpg

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1 hour ago, peachmonkey said:

In all other sims (as well as in DCS A8) when the RPM gauges dance like that it means there's a serious problem with the engine.

Just don't take "other sims" as a measure for anything 🙃 . Yes, RL engines, props and governors do change and needles in instruments do dance up and down, that's how it works, sometimes it's due to engine, governor, props, themselves, sometimes it's just how the instruments work (remember, 80yo instruments, they weren't perfect), who cares, it happens as seeing it depicted like that is cool as hell.

 

S!


Edited by Ala13_ManOWar

"I went into the British Army believing that if you want peace you must prepare for war. I believe now that if you prepare for war, you get war."

-- Major-General Frederick B. Maurice

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3 minutes ago, Ala13_ManOWar said:

Just don't take "other sims" as a measure for anything 🙃 . Yes, RL engines, props and governors do change and needles in instruments do dance up and down, that's how it works, sometimes it's due to engine, governor, props, themselves, sometimes it's just how the instruments work (remember, 80yo instruments, they weren't perfect), who cares, it happens as seeing it depicted like that is cool as hell.

 

S!

 

 

but of course, absolutely no argument there. 🙂  I'm just a hobbyist in love with the WWII aviation.

 

I'm just trying to understand the mechanics behind it. DCS simulates a new aircraft, so there's got to be an actual reason behind these fluctuations, i.e. it must be modeled (hopefully? :D) in accordance to manuals and a published expectations of this instrument. I'd love to research it on my own but I have no idea how to even begin to tackle this. I presume we need to get the actual part number of this tachometer to get a full understanding of its operation.

 

Also, does RPM gauge fluctuate like that in the DCS Spit IX?  I don't think it does, does it?

 

 

 

 

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16 minutes ago, peachmonkey said:

Also, does RPM gauge fluctuate like that in the DCS Spit IX?  I don't think it does, does it?

 

No it doesn't, however it's a completely different type of gauge. The Mossie gauge has two hands like a clock, the smaller hand reading 0-1000 rpm steps (0 to 1 on the dial) and the larger one, the one we are seeing the fluctuations on, measuring 100 rpm steps (0 to 1 on the gauge = 0 to 100 rpm), so on your gif above what we are seeing is an rpm fluctuation of around 50 rpm. The gauge is reading 2830 to 2880 rpm, averaging around 2850 rpm.

 

Spitfire rpm gauge is a single handed affair.


Edited by bart
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15 minutes ago, bart said:

measuring 100 rpm steps (0 to 1 on the gauge = 0 to 100 rpm), so on your gif above what we are seeing is an rpm fluctuation of around 50 rpm.

 

the higher resolution display of the oscillation definitely makes sense, but then it also means that these Merlins can't maintain the steady RPM's neither in taxiing nor in level flight. I find it pretty hard to believe since all of the engine power specs indicate RPM's down to 50 or even 25, in which case making those specs to be totally bogus and unreliable. But I don't know how Merlins work, so I'm just approaching it from a rather distant objective point of view. Such RPM fluctuations may also negatively effect the variable-pitch prop mechanism itself, just imagine it being jerked like that every half a second.

 

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That settles the argument, I guess 😁. Thanks for posting.

 

3 hours ago, peachmonkey said:

 

but of course, absolutely no argument there. 🙂  I'm just a hobbyist in love with the WWII aviation.

 

I'm just trying to understand the mechanics behind it. DCS simulates a new aircraft, so there's got to be an actual reason behind these fluctuations, i.e. it must be modeled (hopefully? :D) in accordance to manuals and a published expectations of this instrument. I'd love to research it on my own but I have no idea how to even begin to tackle this. I presume we need to get the actual part number of this tachometer to get a full understanding of its operation.

Would my RL experience count at all since it's not in a Mossie or anything alike? Does it count I've seen instruments do that in many other planes, IRL but also warbirds vids? You would have to just believe me. And, my point anyway was, stop worrying about little unimportant things and enjoy the beast. Anyway, I'll tell you an argument 😁 .

 

The easy thing to do would be making those needles point a perfectly defined value and that's all. To make them dance in a precise range matching the exact behaviour of the engine at any given time, take a closer look, both engines aren't synchronized at all, and "dancing band" ( :biggrin: I just made the name up, right) doesn't match either, and not just making them move the same bit always and just that… That my friend is a hell of a lot coding. Why would they bother in the first place to depict such a thing if it weren't real? Remember, on top, Mr nick Grey, their boss, has flown the type and knows the behaviour, what would it look like to him with something so blatantly wrong if it weren't real? You're welcome 😉 .

 

S!

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"I went into the British Army believing that if you want peace you must prepare for war. I believe now that if you prepare for war, you get war."

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4 hours ago, peachmonkey said:

You've come to experience my learning process. 🙂 Or should I say "unlearning" process of the information I've absorbed through the computer flight simulators. 🙂  

Don't worry, we all have been there at some point :thumbup:.

 

S!

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"I went into the British Army believing that if you want peace you must prepare for war. I believe now that if you prepare for war, you get war."

-- Major-General Frederick B. Maurice

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Gotta say I had no idea they did this,so I've learnt something........thanks for bringing it to our attention peachmonkey 👍

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On 9/15/2021 at 12:39 AM, peachmonkey said:

 

haven't seen this in A8 (my main plane I fly). Is this something that all allied aircraft have? Seems pretty strange..

 

I see it in the A8 when in that bad-RPM range and the thing tries to shake itself to death.

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