F-15c drag and weight

[humptydumpty]

Hi,

 

HOPE THIS IS IN THE RIGHT SECTION.

 

DCS 1.5.2 / 2.0

 

I was trying out the F-15 in Nevada , firstly both these addons are very good.

 

But I have noticed something with the F-15 , I maybe wrong don't know as I have never flown a real one.

 

I tried a touch n go at Nellis but didn't maintain the glideslope and also the thrust was not correct I guess which made me come in like a rock but as I was on a touch n go I climbed back up after touchdown and retracted the gears and not sure if I looked at the gear light but as I had a bumpy hard touchdown I checked the external view and noticed my left gear was still out.

 

Now this got me wondering , shouldn't the aircraft be more heavy on the left because there is more weight and drag on the left side. I didn't even need more thrust or need to adjust any of the controls , the aircraft was flying like a normal one flies in DCS.

 

A similar thing happened with the Mig21bis and I could literally feel the aircraft more heavy on the left and had to apply right rudder with some right aileron to keep her leveled with more thrust. I am not comparing the developer point of these but just a basic LIFT WEIGHT DRAG THRUST principles.

 

Definitely the DCS model is very responsive quick in climbs turns and banks. The aircraft does feel easy to ride.

 

Could someone shed a light on this ?

 

 

OOPS MOD I PUT THIS IN THE 1.5.2 SECTION PLEASE MOVE IT 2.0

 

 

Thanks.

Edited January 18, 2016 by humptydumpty

[humptydumpty]

Oops this should be in the BELSIMTEK section.

[Anatoli-Kagari9]

Zulfi,

 

open a new thread there and copy & paste this to that new thread :-)

[humptydumpty]

Yeah I guess you are right.

[GGTharos]

Now this got me wondering , shouldn't the aircraft be more heavy on the left because there is more weight and drag on the left side. I didn't even need more thrust or need to adjust any of the controls , the aircraft was flying like a normal one flies in DCS.

 

More drag yes, more heavy, no ... the other side has a landing gear too you know :)

 

Anyway it might not be modeled right, but on the other hand you're going slow so drag has a bit less effect.

[SinusoidDelta]

It sounds to me like CAS was doing its job then.

[humptydumpty]

More drag yes, more heavy, no ... the other side has a landing gear too you know :)

 

Anyway it might not be modeled right, but on the other hand you're going slow so drag has a bit less effect.

 

 

Yes there is the other landing gear also to account for but when they are down the whole scenario changes.

 

Because of the left landing gear which is stuck causes more drag which would require more thrust and if the thrust is not given it will lead to more weight and non of these were required as the aircraft was flying very normal.

 

I wasn't slow as I had just climbed back from a touch n go.

 

Yes could be they haven't modeled it as yet, probably will notice it in the PFM.

 

Thanks.

Edited January 19, 2016 by humptydumpty

[humptydumpty]

It sounds to me like CAS was doing its job then.

 

???

 

Do you mean the FBW system ? I thought the F15's don't have a FBW like the F16 and I actually don't like FBW :) hate it when I don't have control.

Edited January 19, 2016 by humptydumpty

[GGTharos]

Because of the left landing gear which is stuck causes more drag which would require more thrust and if the thrust is not given it will lead to more weight and non of these were required as the aircraft was flying very normal.

 

No, it won't lead to more weight. That is physically impossible.

 

I wasn't slow as I had just climbed back from a touch n go.

 

That could be 200kts, could be 300 ... Do you know the speed?

[GGTharos]

???

 

Do you mean the FBW system ? I thought the F15's don't have a FBW like the F16 and I actually don't like FBW :) hate it when I don't have control.

 

It had something like an FBW... And without it, you'd have no control.

[humptydumpty]

No, it won't lead to more weight. That is physically impossible.

 

 

 

That could be 200kts, could be 300 ... Do you know the speed?

 

 

Hmm Well I thought drag does create more weight because of less thrust hence less lift.

 

 

Actually I didn't watch the speed I just climbed up. But yes it could have been in those regions.

Edited January 19, 2016 by humptydumpty

[JINX_1391]

???

 

Do you mean the FBW system ? I thought the F15's don't have a FBW like the F16 and I actually don't like FBW :) hate it when I don't have control.

 

CAS = Control Augmentation System. The F-15 is dual hydraulic and FBW; making up the CAS. I think what SinusoidDelta was trying to say is the CAS system was correcting the aircraft for you. Thus the CAS applied the correct amount of roll/yaw/pitch to negate the "feel" of an extended gear.

 

For the weight vs. drag discussion. The gear weighs the same extended or retracted, so no physical weight is ever gained (although I have had a few losses before). More drag is created with extended gear, and as a result the aircraft may feel "heavier" because of the change in aerodynamic posture.

 

I hope that helps and I'm not too far off with my logic.

[humptydumpty]

CAS = Control Augmentation System. The F-15 is dual hydraulic and FBW; making up the CAS. I think what SinusoidDelta was trying to say is the CAS system was correcting the aircraft for you. Thus the CAS applied the correct amount of roll/yaw/pitch to negate the "feel" of an extended gear.

 

For the weight vs. drag discussion. The gear weighs the same extended or retracted, so no physical weight is ever gained (although I have had a few losses before). More drag is created with extended gear, and as a result the aircraft may feel "heavier" because of the change in aerodynamic posture.

 

I hope that helps and I'm not too far off with my logic.

 

 

Yes you are correct the weight is already there its nothing extra.

[SinusoidDelta]

Yes I was implying CAS was correcting the issue for you. Commanded roll was 0 so it applied differential stabilator to maintain a zero roll rate. F-15 is not FBW, it's hydraulically boosted augmented controls. At high air speeds it would cause some asymmetry.

[GGTharos]

CAS does not zero out un-commanded roll; roll trim is manual as per -1 and the maintenance manual.

[humptydumpty]

Yes I was implying CAS was correcting the issue for you. Commanded roll was 0 so it applied differential stabilator to maintain a zero roll rate. F-15 is not FBW, it's hydraulically boosted augmented controls. At high air speeds it would cause some asymmetry.

 

Yep you were

 

 

BTW is the F-15 an AFM or PFM ?

[GGTharos]

It is PFM.

[tarracta]

The flight and damage model is still very, very far away from realism. In nearly every combat situation I think "oh dear, this may not happen in reality".

 

Just yesterday I flew a mission over 2 hours with a burning wing (which I got from a very bad takeoff) ... burning for hours with a big fireball and smoke trail, but not any consequences regarding the flight behaviour or while doing the mission, no fuel leakage or anything else ...

 

But ya, for that it's an arcade flight sim module.

[GGTharos]

Unimplemented damage effects don't make it arcade. If you want arcade, I suggest you look at the 'real deal', like HAWX or Ace Combat.

[pepin1234]

Yep you were

 

 

BTW is the F-15 an AFM or PFM ?

 

we are not sure what is going on with the F-15 flight model. The drag and weight with external fuel tanks is a fake. You can get 25000m with full external fuel tanks and a full combat payload, also you can keep in combat with three fuel tanks and do maneuvers like hell.

 

Just do a test by yourself and see the real.

 

I open a thread about this situation and was closed and censured, look here: http://forums.eagle.ru/showthread.php?t=155452

[Sweep]

we are not sure what is going on with the F-15 flight model. The drag and weight with external fuel tanks is a fake. You can get 25000m with full external fuel tanks and a full combat payload, also you can keep in combat with three fuel tanks and do maneuvers like hell.

 

Just do a test by yourself and see the real.

 

I open a thread about this situation and was closed and censured, look here: http://forums.eagle.ru/showthread.php?t=155452

 

This might help:

 

http://www.avialogs.com/index.php/en/aircraft/usa/mcdonnelldouglas/f-15eagle/to-1f-15a-1-flight-manual-f-15a-b-c-d-aircraft-block-7-and-up.html

[GGTharos]

Did you compare to the -1?

 

If not, quit saying that it's fake since you haven't found anything of use.

 

we are not sure what is going on with the F-15 flight model. The drag and weight with external fuel tanks is a fake. You can get 25000m with full external fuel tanks and a full combat payload, also you can keep in combat with three fuel tanks and do maneuvers like hell.

 

Just do a test by yourself and see the real.

 

I open a thread about this situation and was closed and censured, look here: http://forums.eagle.ru/showthread.php?t=155452

[pepin1234]

Why do you think this flight manual can help to get more than 25000m with full max payload with the current F-15 flight model and do all maneuvers with fuel tanks?

 

So do you think with more weight and drag you get more altitude? A 9Th year schoolboy know enough physics to know something is going wrong with the F-15 flight model.

[GGTharos]

I think you should compare F-15 performance the flight manual.

 

You some random test that has no basis in reality, then you complain it's fake without comparing it to real data.

 

All you said was 'look I got to 25000m with all this!'

 

You say how you got there (but I know you did a zoom climb, which is the only way you can get up there)

You didn't say how long you stayed up there ( ... could you stay up there? I know you couldn't ;) )

 

It's funny that you claim it's fake when you haven't even bothered to compare performance against the real performance charts. Right now the only think that is fake here is your attempt to pass this off as a valid complaint.

 

BTW, did you know that the drag force is reduced at high altitudes? Do you know why?

[SinusoidDelta]

we are not sure what is going on with the F-15 flight model. The drag and weight with external fuel tanks is a fake. You can get 25000m with full external fuel tanks and a full combat payload, also you can keep in combat with three fuel tanks and do maneuvers like hell.

 

Just do a test by yourself and see the real.

 

I open a thread about this situation and was closed and censured, look here: http://forums.eagle.ru/showthread.php?t=155452

 

25,000 meters? You can't be serious. I don't think you could even zoom climb to 80kft with 3 bags and you could never do it with full fuel as you have to burn fuel to fly. I don't know if "maneuvers like hell" is a technical term but let's not go down this path. Make points with data and it will speak for itself. I've done quite a few tests and while I've found inaccuracies, none are of the severity you are claiming.