Delta Virtual Airlines Water Cooler - Fleet 757 overpowered?

Delta Virtual Airlines Water Cooler | Airline Operations | Fleet 757 overpowered?

DVA7130
Senior Captain, B727-200
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Posted onPost created on June 15 2011 21:00 ET by Ryan Morse

I have a problem with the Fleet 757. At cruise I often will have a GS of 570, with no wind. I have been comparing the CFG's of the fleet 757 and the CS 757 demo. (fleet on left) Does any one see any major differences that could cause this? I do also have problems with N2 being high, but I guess that can be explained by the rated_N2_rpm being much higher.
Thanks

Ryan Morse (DVA7130)

DVA9589
First Officer, A320

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Posted onPost created on June 16 2011 00:19 ET by Randy Donnelly

We noticed that also on Vatsim. You blew by us on our way to COS like we were standing still. You sarted way behind us and ended up a 100mi ahead of us. PMDG 737 using ASE weather. It caused a little concern with ATC. Having RW upper level winds makes a huge difference also. Call ya Blubyme smile

The fleet 757 probably has way less parasitic drag programmed in it. engine numbers are similiar.

Randy Donnelly

First Officer, A320

Posted onPost created on June 16 2011 01:02 ET by Ryan Morse

Hmm, for the sake of VATSIM controllers. Could anybody please donate me a number with a decimal to live in my parastic_drag_scalar line?

Ryan Morse (DVA7130)

DVA1008
Senior Captain, B757-200

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Posted onPost created on June 16 2011 11:04 ET by Matt Young

The parasitic drag isn't what you want to change. Parasitic drag accounts for dirt, dead bugs, and other things that would be parasites to the airframe. You MIGHT want to change induced drag, but I'm not necessarily convinced that's where the problem lies. Without doing some test flights and tuning myself, I'm not going to throw any numbers at you.

Matt Young

Senior Captain, B757-200

Posted onPost created on June 16 2011 22:37 ET by Randy Donnelly

Ya. Thats what I was thinking. Bugs dont have that much drag. smile

I stand corrected

[flight_tuning]
cruise_lift_scalar =1.000
parasite_drag_scalar =1.000
induced_drag_scalar =1.1
elevator_effectiveness =1.0
aileron_effectiveness =1.0
rudder_effectiveness =1.0
pitch_stability =1.000
roll_stability =1.000
yaw_stability =1.000
elevator_trim_effectiveness =0.800
aileron_trim_effectiveness =1.000
rudder_trim_effectiveness =1.000

Randy Donnelly

First Officer, A320

Posted onPost created on June 16 2011 23:44 ET by Ryan Morse

It looks like your Induced drag is lower than the fleet's.

Ryan Morse (DVA7130)

DVA1763
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Posted onPost created on June 17 2011 00:55 ET by Steve Pickle

A GS of 570 with ZERO wind seems very believable to me.

Mach .82 is 542 knots, so if you factor in altitude etc., that's about right. You should really consider investing in Active Sky Evolution if you fly online often.

Steve Pickle (DVA1763)

DVA2728
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Posted onPost created on June 19 2011 19:46 ET by Shane Olguin

You know, if you add this to the issue tracker I can have Luke assign it to me and I'll take a look.

Shane Olguin (DVA2728)

Posted onPost created on June 20 2011 23:00 ET by Shane Olguin

I think I'll just start working on this one and see what I can come up with. Was this in FS9 or FSX?

Shane Olguin (DVA2728)

Posted onPost created on June 20 2011 23:15 ET by Shane Olguin

Oiiii... well I just looked at everything. This is going to need a complete makeover! It's all over the place. I should be able to help out though as I have some reasonably good data for PW2040s. I work on C-17s at work and they use the military equivelant of that engine so I've got some great data for engine parameters. I'll get to work!

Shane Olguin (DVA2728)

Posted onPost created on June 20 2011 23:58 ET by Ryan Morse

Yeah, I always had a funny fealing with it. It is FSX.

Ryan Morse (DVA7130)

Posted onPost created on June 21 2011 10:56 ET by Shane Olguin

Got it, I'm working on it now.

Shane Olguin (DVA2728)

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Posted onPost created on June 21 2011 11:22 ET by Charles Carter

Matt Young wrote:

The parasitic drag isn't what you want to change. Parasitic drag accounts for dirt, dead bugs, and other things that would be parasites to the airframe. You MIGHT want to change induced drag, but I'm not necessarily convinced that's where the problem lies. Without doing some test flights and tuning myself, I'm not going to throw any numbers at you.

Parasite Drag includes many things, one of the biggest components of parasite drag is form drag. Form drag is drag from the form of the airframe. Every little (and large) piece of the plane that protrudes into the airflow increases form drag, and therefor parasite drag. You could include bug guts and dirt in that, but the airframe itself is what generates the majority of parasite drag.

Induced Drag is the drag that is generated as a by-product of creating lift because of changing the direction of airflow around the wing.

*None of this necessarily helps with the fleet 757 problem, but should provide a little better understanding of aerodynamics. :-)

Charles Carter

Senior Captain, MD-88

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Posted onPost created on July 17 2011 14:53 ET by Dustin Thames

I was having the same issue with the QW757, but discovered that the model was using PW2043's (instead of PW2037) on the 752 model. Not sure if this is happening here, but thought I'd throw it out there.

EDIT: Just took a closer look at the cfg files above. Static thrust for a PW2037 (engine on DAL's 757-200 fleet) is 37530 pounds, so the fleet thrust is a little bit higher than normal. The engine in the CS757 cfg you have above is a PW2040, which is only on DAL's 757-300 fleet, IIRC. I also agree that the N2 value in the fleet 757 is incorrect. The one in the CS cfg is closer to reality.

Dustin Thames

First Officer, B777-200

Posted onPost created on July 18 2011 19:15 ET by Randy Donnelly

Overpowerd. probably not. Too slick, perhaps. Rw aviation engineers would love to have that problem!

Randy Donnelly

First Officer, A320

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