Flightmodel difference Safir 91D?

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SuredT
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Flightmodel difference Safir 91D?

Post by SuredT » 03 Oct 2006, 20:05

Hello to the Beta testers,

I asked Alex in another post about the peculiarty that when I am flying with cruise power in a Safir 91D and I adjust the RPM (with the propellor control) from 2400 to for instance 2200 I get an increase in engine noise.

Alex answered that it was a MSFS bug and he could do nothing about it.

But why is it that when I do this in the HB-DBL I do NOT get this increase in sound?

Second question: (without pretending to be a better BETA tester than all you guys who have spent zillion hours doing this on de Safir project and I admire you for this, but I am just curious)

When I fly in the SF3 with cruise power and I chop the power to idle, the nose of the aircraft goes up and in the HB-DBL the nose does NOT change in attitude?

These 2 differences give me reason to believe there is a difference in the flightmodels between the HB and the SF3?
Am I wright or wrong?
I am just curious, absolutely no critic on your beta testing.

I must admit that at this moment I do not know what the RLA does in real life, but normally the nose should go down in an single engine airplane.
The first thing I am going to do when I fly in the real RLA is to test this to satify my own curiousity.

Regards, Sjoerd

DNovet
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Post by DNovet » 03 Oct 2006, 20:16

Sjoerd,

The HB-DBL bears as one of few - if not even the only one - a 3-bladed propeller, together with a different engine.
Because of this, slip-stream-effects from prop-wash are very different, also trim behaving differently in reallife.

Cheers,

Daniel

franco
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Post by franco » 05 Oct 2006, 17:33

In any case I never have found real aeroplanes with an engine more noisy with lower propeller rpm (I say noise but for me engine plane sound is celestial music, in particular on RR merlins). This is a strange thing . :-D

DNovet
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Post by DNovet » 05 Oct 2006, 19:33

franco,

That point has also been risen during beta-test.

As a matter of fact, we did not have the funding or sponsoring, to get high-quality sound-equipment in a Safir and start flying around just for the joy of sound. As a matter of fact, i was close to get a friend of mine with the right equipment but then again, problem was having the money to fly to record some music...
And - as a second-step-problem - we did also not have the tools to do proper sound-sampling.

Maybe a point someone would like to do some sponsoring, so it can be incorporated in the next update? *blinkinganeyetowardfranco* ;)

Cheers,

Daniel

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Sebastian
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Post by Sebastian » 29 Apr 2007, 14:44

May I take this thread back to its origin question, the difference between the B-model and C/D-model in flightdynamics (flying, not the engines)?

I got a look at the aircraft.cfgs of all versions and the C- and D-verison use the same settings, while the B-model uses other values in yaw-MOI and empty-weight-MOI.

My impression is that the B-model reacts a bit faster on opposite roll adjustments.
Greetings from the Ruhrgebiet, Germany

Sebastian

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snave
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Post by snave » 29 Apr 2007, 19:31

The aircraft .cfg alters the parameters in the .air file, and is NOT the place to look for differences in flight models.

You will need a properietary reader for the .air file - and a sound knowledge of aerodynamics and the interraction of a range of computer parameters when used to create such a virtual flight model, and then you will be able to discern the differences. If you look at how the models are defined in the sim you will find B, C and D models have SEPARATE folders, then HB has yet another. So the differences are substantial. HB represents an advance on the D-model, with any changes made in airframe, engine, prop and elsewhere. The three-blade, CS prop is what makes this a more tricky proposition to correctly sound-model in FS, as the FS engine contains a fundamental error in how the engine note is related to power, not prop speed. This is fine for a fixed-pitch prop, but entirely wrong for a constant-speed unit. You can work around it, but all the aircraft here share the majority of their sound files and only the sound .cfg is different, so if CS prop sounds right, it would be wrong for the fixed-pitch versions or vice versa.

But having said that, unlike Franco I have flown a CS prop airplane (a Vans RV-7) that actually did just that - noisier at lower engine rpm. It is the story for another thread to tell you why. :)

Suffice to say, the flight modelling IS different, and is entirely reasonable that it is so. I haven't flown a Safir, but I have flown a variety of aircraft which differ only in the choice of engines and props, and they certainly do display very different characteristics. In fact, come to think of it, two supposedly identical aircraft can display very different characteristics! Rigging is still a very important part of deciding how an aircraft flies and it is entirely possible to make two identical aircraft pitch in a different way on power reduction or application, let alone the way heavily modfied aircraft like `HB` might behave...

However, in specific response to the B and C models I refer you to the manual. Which tells you that the C model had tanks in the wings, whereas the B model had a large tank in the fuselage. There's your answer about the different roll mechanics...

Personally, I think it is part of the charm of these aircraft that they do respond differently, and you have to remember the flight models were tested by real Safir pilots, so if it comes to the crunch, we are not in any position to argue!
:-D
Simon Evans

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Sebastian
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Post by Sebastian » 29 Apr 2007, 20:58

Thank you for that detailed answer! Of course, I read the manual and not every addon that comes with different versions of a certain plane do take care of subtile little differences in the flightmodel. Nice to read that Sibwings took care of differences between two-tank-models and one-tank-models, three-bladed props and two-bladed ones and so on.

As time goes by there are still new features to find in this outstanding addon! Simply great!
Greetings from the Ruhrgebiet, Germany

Sebastian

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