757 engine power RR-PW

Archived from groups: alt.games.microsoft.flight-sim (More info?)

what is the "inlet_area" related too though? i think my install of the 757
is smaller than a 737's?! i thought it was the whole "fan" area of the
engine???

--
From Overlag - Adam Webb
"Gregory" <flightsim.maps@bkwds.comcast.net> wrote in message
news:j691g1p3236b2g2liuvntto1kpbue6fna4@4ax.com...
>
> The 757 thread a few days ago sparked some interest.. had Osky 757
> folder zipped onto `Aircraft Hanger' folder.. and then got a few more
> via download. Now here's a case-in-point. Since then have been
> Configuring, Editing, Analyzing, and converting 32-bit textures to
> DXT1 and DXT3.. and now have TWO flyable 757's.. one with PW
> and the other RR power.
>
> The comment was.. cut throttles and it `drops like rock'. Well the Cdo
> looks ok.. however here's some interesting info. The AIR files are
> ALMOST IDENTICLE!!
>
>
>
> AIR FILE
>
> Compare: (<) B757-200-PW-PW2043.txt (33170 bytes)
> with: (>) B757-200-RR-RB211-535E4B.txt (33179 bytes)
>
> 22c22
> < Engine Type: PW2043
> ---
>> Engine Type: RR RB211-535E4B
>
> 109c109
> < Max Range: 3,900 nm (7,222 km)
> ---
>> Max Range: 3,395 nm (6,286 km)
>
> 1288c1288
> < 0.000000 52.000000 82.500000
> ---
>> 0.000000 51.725000 82.500000
>
> 1389c1389
> < FIELD 0x540 0x0 DOUBLE 1.020000 *EGT Scale Factor
> ---
>> FIELD 0x540 0x0 DOUBLE 1.001000 *EGT Scale Factor
>
>
> And here's the Engine Data (exactly the same) with polynomials fitted
> over top.. followed by some brief comments.
>
> http://home.comcast.net/~flightsim/752_1506.gif
>
> http://home.comcast.net/~flightsim/752_1507.gif
>
>
> You see now the 0.9M Thrust Factor curve dips as throttles (and CN1)
> are cut.. in addition to the MSFS DEFAULT Mass Flow 1507 which is fat
> in the Hi-mach region for low engine revs. The two combined will
> produce a negative thrust.. which is essentially like a `reverse
> thrust' while descending at hi-speed / low revs.
>
> ALso the 0.9M Thrust Factor 1506 seems VERY aggressive.. nothing
> like climbing at 4,000 fpm direct to hi-cruise while loaded!! It's a
> nice rocketship sometimes!!! { grin } 757s are potent IRL..yes?
>
>
>
> AIRCRAFT CFG
>
> Here's another important result of Aircraft.cfg analysis.. the INLET
> AREA plays a BIG role in multiplying 1507 Mass Flow table. It explains
> the significant difference in the performance between PW
> and RR sims. THIS NEEDS to be LOOKED AT more carefully!!
>
>
> Compare: (<) 757-200 Northwest NC - PW\Aircraft.cfg (14398 bytes)
> with: (>) 757-200 American - RR\Aircraft.cfg (15615 bytes)
>
> 128,133c128,133
> < bypass_ratio = 6.00
> < inlet_area = 33.5757 <<< important data
> < rated_N2_rpm = 29920.0
> < static_thrust = 43734.0
> < afterburner_available =0
> < reverser_available =1
> ---
>> bypass_ratio = 4.36
>> inlet_area = 51.250 <<< important data
>> rated_N2_rpm = 29920.0
>> static_thrust = 43500.0
>> afterburner_available = 0
>> reverser_available = 1
>
>
> Bypass ratio hasn't been found to have an effect.. static thrust is
> from MFG's data sheet. Rated N2 RPM is high but has no real effect..
> more like 12,000 rpm IRL?
>
>
> ..can we fly it now?? :-))
>
>
> -Gregory
>
>

Archived from groups: alt.games.microsoft.flight-sim (More info?)

On Mon, 15 Aug 2005 20:32:42 +0100, "Adam Webb"
<adam@ajmysecondname.eclipse.co.uk> brought the following to our
attention:

>what is the "inlet_area" related too though? i think my install of the 757
>is smaller than a 737's?! i thought it was the whole "fan" area of the
>engine???

what is smaller?.. the inlet.. or the folder size?

Inlet area is the engine nacelle opening.. the FAN area essentially.
You can find an image, scale it, and come up with a diameter which is
very close.. then find the Area. The bigger the Area.. the less Net
Thrust. A very small Inlet Area results it LOTS of usable Thrust.


Fn = Net Thrust

Fg = Gross Thrust


Fn (Net Thrust) is found as follows: Fn = Fg - Fr


Fg = Static_Thrust * delta2 * TBL(1506)

Fr = A_inlet * V / g * TBL(1507) g = 32.174


Fr = MF * TAS(fps) / g

MF = A_inlet * delta2 * sqrt(theta2) * TBL(1507)



So Inlet area determines the Mass Flow.. that's why TBL1507 is called
Mass Flow Factor. Is that clear? Best to ask Aero Engineer for more
details. I just know enough to skillfully manipulate the numbers.  


-g