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Old 12-31-2018, 10:27 AM   #21
jcomm
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Originally Posted by msalama View Post
Aides off, and you could still maintain your heading with wheel brakes only, taking off with approx. 1.4 ATA on the MAP gauge it seemed. This can't be right...
If you look carefully he maintains 1,2 ATA until around 150km/h, which means that enough propwash has already developed, by that time, for the rudder trim tab to start doing it's job. Since a few versions ago the 109, as well as the 190 if I'm not wrong ( ? ) also allow for the setting of their ground trim tabs for rudder and aileron - we don't know if the video was recorded when this additional aid was already available, and that ground adjustable trim tab set considerably starboard ?

P.S.: Yet, I actually can't observe any rudder deflection even eventually induced by that rudder trim tab ...

The only thing that the DCS 109 does not have, probably due to a limitation in it's core FDM, is the chance for multiple ( more than two ) control compensators contributing to a control surface. Probably a maximum of two are allowed, and since in the 109 and the 190 there are actually 3 "pitch control contributors" - elevator, stabilator and elevator trim tab - only the first two can work. In another combat flight simulator that allows for all of the three, we have a fixed, set by the developers and not adjustable by the user, elevator trim tab, and as power is added during takeoff, one can see the elevator deflect ( down ) compensating for the pitching up tendencies of the K-4 with a filled MW50 tank ( although the weight of the MW50 tank is probably also well compensated by the heavier engine ? ).

Overall, I don't say DCS is perfect, of course it isn't for sure, but it is a very close approximation in many levels to the possible PC-based modelling of a prop aircraft, given the limitations imposed by a combat simulation game.

Some years ago I discussed in a thread started by me the fact that there was a weird effect noticeable on the P51d when taking off with the first point of flaps, full power and a good deal of crosswind. Instead of turning upwind the aircraft, at the beginning of the takeoff run, showed a tendency to yaw downwind, and the downwind wing a slight tendency to want to come up, resulting in the virtual pilot having to use at that phase rudder into and aileron away from the wind ?????? How was such effect possible ?

I found out later, and even sent Yo-Yo the document with the mathematical development, the "proof of concept", from an aerodynamics text book. The reason was, just as Yo-Yo pointed out on that thread, the fact that indeed the deflected propwash acting over the root of the downwind wing, and the downwind tail surfaces was enough to cause the additional lift, and associated drag as well as the asymmetric hit of tail surfaces, and the resulting downwind moments at that initial phase of the takeoff run...

So, I tend to accept, with due imitations of course, most of the outcomes I get from DCS aircraft I own ( only those by ED/Belsimtek, until the Christen becomes available :-) )
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Old 12-31-2018, 10:35 AM   #22
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SORRY! Double post :-/
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Old 12-31-2018, 12:47 PM   #23
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Did one more - taking off with ~1.2ata and manual pitch 12 o'clock
You can see my settings at the end of the video - no assists and trim tabs all set to 0

The faster you get the harder it is to keep it on track and obviously the takeoff isn´t that nice overall but still it´s possible without touching the pedals.

Since the last video I´ve also done a complete new installation of DCS on another hard drive so I don´t think anything is broken on my end.


@msalama
Yeah, trim nose heavy for takeoff - I prefer to trim it full nose heavy.


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Old 12-31-2018, 12:57 PM   #24
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No, I believe you, the evidence is there so there's nothing to debate. I just wonder why it clearly cannot be done on my end is all... weird stuff
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Old 12-31-2018, 12:58 PM   #25
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Quote:
Probably a maximum of two are allowed
What makes you think so?
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Old 12-31-2018, 04:08 PM   #26
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Originally Posted by msalama View Post
What makes you think so?
Because otherwise we would probably be given the chance to also set the ground adjustable elevator trim tab that exists in the 109.
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Old 12-31-2018, 04:35 PM   #27
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Quote:
ground adjustable elevator trim tab that exists in the 109
Does it? I've always thought it had rudder and aileron tabs only, plus a variable incidence tailplane without a presetable fixed tab.
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Old 12-31-2018, 05:50 PM   #28
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Default take off

this is take off of bf-109 g12 preaty similat to k-4 i gues, I noticed one very interesting thing
check ATA gage its scaled to 2.0
ED give us 1.98 ata K-4
check during take off, stick hard to right so aleirons works at low speeds
check what ata pilot is runing we will not get 1.8 ata sound of db605 ever
another thing oil pressure durign start up rising ver yvery slowly not like in dcs launching in to sky like saturn V
https://www.youtube.com/watch?v=wR8SOB1Fmbg

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Old 12-31-2018, 07:22 PM   #29
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Thx for the video grafspee

It's interesting to notice:

.) not even 1,2 is used for takeoff power, while in DCS most "pilots" slam the throttle or use 1,4... Most of the time I see it at maybe 1,1 ATA in the video..

.) SLIGHT rudder input. Maybe there was some significant starboard wind component, but the amount of rudder used to correct for the drift is minimal, maybe due to the conservative ATA used ?

So, after watching the video I am even less surprised that with toe brakes only, aileron ( at near rotation speed and after airborne ) and correct pitch, the real thing can probably also be made to takeoff without rudder input.

@msalama : yes there are also ground adjustable elevator trim tabs on left and right elevators. You can easily glimpse it in RW footage but even on ED's Web page for the Bf109 K-4 here:

https://www.digitalcombatsimulator.c...urst/index.php

for example on the third photo from the left in the first row...
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Old 12-31-2018, 09:55 PM   #30
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Quote:
You can easily glimpse it in RW footage
Except that they're not necessarily trim tabs, but something else altogether (see the DCS manual pic f.ex.). Any SME guys around?
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