A question about the F18 FBW vs the F15

[falcon_120]

Hello guys,

 

I own both modules, and I see a clear difference in how both aircraft, in particular in the way the hornet has quite a lot of inertia while rolling. So in the F15 I get the feeling that i can roll and it is super crisp so when i stop the input the aircraft almost stop instantly, I can almost do a perfect 90 degree roll and stop ,on the hand in the hornet I have a more similar feeling to a non FBW aircraft is that makes sense. When I roll the aircraft have a more pronounced roll inertia and the plane wants to keep rolling unless I roll in the opposite direction a bit.

 

So the question is... Is this how it should feel? Is there a difference with the FBW of the F15 and the one in the F18? Or is just a question of one of the FM being more simplistic maybe?

 

Thanks for the answers

[Kev2go]

F15c technically doesn't have fly by wire but digitally assisted flight controls.

 

Meaning you still have full traditional control linkage ( mechanisims boosted with hydraulics) to various flight control surfaces. if you were to remove the computers, or rather if they would fail aircraft's still basically fully controllable . For the most part the flight control in a f15 just smooths out the inputs and prevents the pilot from pulling to many g's. In an fa18 If you flight controls were to be turned off or just totally fail from damage, then a pilot literally has zero control. They are just literal wires transmitting electrical signals carried over from the flight control computer that interprets pilots stick and pedal input.

 

 

Both f15 and f18 technically have pfm.( Professional flight model) , but I wpuld still think f18e is more in depth due to being a full fidelity module.

 

Cant say fore sure though. It's not like I've flown these irl.

Edited June 10, 2019 by Kev2go

[Harker]

I'd actually bet on the F-15C to have a more accurate FM for the moment. I remember ED working on it and making announcements and videos a few years ago. Apparently, real pilots tested the FM at the edge of the flight envelope and everything.

The F-18's FM is confirmed to be still in development, so I expect it to improve. In the end, I do expect the F-18 to have a more accurate or at least equally accurate FM than the F-15C, due to it being a full module.

[Rainmaker]

F15c technically doesn't have true fly by wire but digitally augmented flight controls.

 

Meaning you still have traditional control linkage ( rods or pulley cables) to various flight surfaces. if you were to remove the computers, or rather if they would fail aircraftis still controllable to a degree. For the most part the flight control in a f15 just smooths out the inputs and prevents the pilot from pulling to many g's. In an fa18 If you flight controls were to be turned off or just totally fail from damage, then a pilot literally has zero control. They are just literal wires transimtting electrical signals carried over from the flight control computer that interprets pilots stick and pedal input.

 

 

Both f15 and f18 technically have pfm.( Professional flight model) , but I wpuld still think f18e is more in depth due to being a full fidelity module.

 

Cant say fore sure though. It's not like I've flown these irl.

 

 

You have a lot of your information wrong.

[GGTharos]

The F-15C had an electro-mechanical CAS, nothing digital or anything resembling FBW.

 

If you lose the hydraulic circuits, you lose control. There are no pulleys, no wires, no manual reversion.

 

The CAS does a lot more than 'smoothing out input' (all fighters use some form of damping), and it has absolutely no g limit.

 

What it does do is provide trimming to 1g, consistent stick force to g ratio, elevator and aileron mixing, as well as the aileron rudder interconnect and rudder limiter based on AOA. There's more, but that's the gist of it.

 

F15c technically doesn't have true fly by wire but digitally augmented flight controls.

 

Meaning you still have traditional control linkage ( rods or pulley cables) to various flight surfaces. if you were to remove the computers, or rather if they would fail aircraftis still controllable to a degree. For the most part the flight control in a f15 just smooths out the inputs and prevents the pilot from pulling to many g's. In an fa18 If you flight controls were to be turned off or just totally fail from damage, then a pilot literally has zero control. They are just literal wires transimtting electrical signals carried over from the flight control computer that interprets pilots stick and pedal input.

[falcon_120]

So lets focus on my only concern, the rolling implementation in game in the F18 vs the F15(because is what i fly the most).

Basically my main issues, or lets say differences in behavior that i cannot fully understand are:

 

-The F18 has a much bigger roll intertia. From level flight apply left input in the X axis and go back to center, what i'm seeing here is that the F15 behaves like I would think and F16 would do, stopping instantly after the input cease and staying with whatever roll angle you stop (which is weird for a non FBW system). The F18 on the other hand seems to suffer from a higher degree of roll inertia so the plane does not stop rolling for a bit after the input is over, and the plane starts like a mini scissor. It seems to me rather an inacuracy of the F15 model than an inacuracy of the F18 one?

 

-The f18 loose trim whenever a weapon is deployed, so launching a amraam generates a lot of roll that you need to trim quickly. This is more pronounced launching a Aim7 sparrow, if you dont trim the plane rolls hard towards the opposite launching station. On the other hand the F15 does not need any trim in the X axis whatsoever to the point where it seems it has a FBW that does this for you, but seems weird.

 

So I guess there are some explanations behind right? Is this just a wrong perception of me or do you feel something similar?

 

Enviado desde mi SM-G950F mediante Tapatalk

[Svend_Dellepude]

Neither F-15, F16 or F-18 has any auto roll trim system. All asymmetri has to be dealt with by the pilot.

Regarding the missiles.

The F-15 needs trimming too, just not as much for various reasons. F-15 has more mass and all missiles are closer to the F-15's CG.

Then there is the dicussion about the drag of the missiles. If drag is excessive ingame compared to IRL the effect is, of course, gonna be exaggerated.

[GGTharos]

-The F18 has a much bigger roll intertia. From level flight apply left input in the X axis and go back to center, what i'm seeing here is that the F15 behaves like I would think and F16 would do, stopping instantly after the input cease and staying with whatever roll angle you stop (which is weird for a non FBW system).

 

 

The eagle's rolling precision is quite incredible for a heavy fighter, and there's a lot of damping that is done by the CAS to help. Not sure if the apparent lack of inertia is correct though.

 

 

It seems to me rather an inacuracy of the F15 model than an inacuracy of the F18 one?

Disengage CAS and see what happens :)

 

 

So I guess there are some explanations behind right? Is this just a wrong perception of me or do you feel something similar?

You do have to trim the eagle for uneven payloads.

Edited June 8, 2019 by GGTharos

[mmtaraval]

I find if I have clean wings, 20% fuel, and flying at around 380kts the f-18 has very sharp roll responses. Also looking at several in-cockpit videos shows this not so snappy roll inertia:

[AKarhu]

F-18's stick throw allows for pretty nice aileron punch against the roll to stop it precisely. With wrist stick (TM Warthog), it appears difficult to me to do accurately.

[ThorHammer]

The Blue Angels don't seem to have any problems snapping rolls and stopping them abruptly...

[BuzzU]

The Blue Angels don't seem to have any problems snapping rolls and stopping them abruptly...

 

Yes, but they fly clean, light planes. We hardly ever do that.

[Wizard_03]

The Blue Angels don't seem to have any problems snapping rolls and stopping them abruptly...

 

They also cheat by using heavier bob weights for more precise inputs in their sticks. ;)

[Kev2go]

The F-15C had an electro-mechanical CAS, nothing digital or anything resembling FBW.

 

If you lose the hydraulic circuits, you lose control. There are no pulleys, no wires, no manual reversion.

 

The CAS does a lot more than 'smoothing out input' (all fighters use some form of damping), and it has absolutely no g limit.

 

What it does do is provide trimming to 1g, consistent stick force to g ratio, elevator and aileron mixing, as well as the aileron rudder interconnect and rudder limiter based on AOA. There's more, but that's the gist of it.

 

but the point is, its loss of hydraulics and not loss of flight control computer that would prevent it from being controllable. in a FBW , if electronics related to the FCS, fail then you retain far less control.

Edited June 10, 2019 by Kev2go

[Kev2go]

The F-15C had an electro-mechanical CAS, nothing digital or anything resembling FBW.

 

If you lose the hydraulic circuits, you lose control. There are no pulleys, no wires, no manual reversion.

 

The CAS does a lot more than 'smoothing out input' (all fighters use some form of damping), and it has absolutely no g limit.

 

What it does do is provide trimming to 1g, consistent stick force to g ratio, elevator and aileron mixing, as well as the aileron rudder interconnect and rudder limiter based on AOA. There's more, but that's the gist of it.

 

Sorry i got the flight control mixed up with whats in F15C and the F15E, which does have digital based Flight control System

 

 

yes CAS is a still a flight control computer to augment control surfaces, but i guess like you say its just a older electromechanical ( Analog category?) found in older aircraft.

Edited June 9, 2019 by Kev2go

[Rainmaker]

but the point is, its loss of hydraulics and not loss of flight control computer that would prevent it from being controllable. in a FBW , if electronics related to the FCS, fail then you have no control.

 

Both the F-15(C,D,E) and the F/A-18C have mechanical connections to the flight control surfaces. I’m not sure where you are sourcing you info from...but it’s wrong.

[Rainmaker]

Sorry i got the flight control mixed up with whats in F15C and the F15E, which does have digital based Flight control System

 

 

yes CAS is a still a flight control computer to augment control surfaces, but i guess like you say its just a older electromechanical one found in older aircraft.

 

C & E are more alike than they are different. C & E will both still fly without AFCS

[Kev2go]

Both the F-15(C,D,E) and the F/A-18C have mechanical connections to the flight control surfaces. I’m not sure where you are sourcing you info from...but it’s wrong.

 

 

I never said the F15's dont have any traditional mechanical connections........ :doh:

 

Stating that the Eagle has a digital flight control system, ( that is not the same as its pure Fly by wire.)

 

That is fact, unless you are going to say the USAF cant get their own information straight either?

 

 

https://www.acc.af.mil/About-Us/Fact-Sheets/Display/Article/199185/f-15-eagle/

 

 

 

"The digital, triple-redundant Lear Siegler flight control system"

Edited June 9, 2019 by Kev2go

[Kev2go]

C & E are more alike than they are different. C & E will both still fly without AFCS

 

 

Yes thats is exactly what i said... They will still be able to fully fly without the flight control system..... Even if it won't be as smooth.

Edited June 10, 2019 by Kev2go

[Rainmaker]

Yes thats is exactly what i said... They will fly..... an F/A18 won't.

 

And you are wrong...the F-18 has many of the same components. It’s not an F-16.

[Rainmaker]

I never said the F15's dont have mechanical connections........ :doh:

 

Stating that the E has a digital flight control system, ( that is not the same as its pure Fly by wire.)

 

That is fact, unless you are going to say the USAF cant get their own information straight either?

 

 

https://www.acc.af.mil/About-Us/Fact-Sheets/Display/Article/199185/f-15-eagle/

 

 

 

"The digital, triple-redundant Lear Siegler flight control system"

 

 

You are ignoring the part of my post that has the words “F-18” in it. ;)

[Kev2go]

And you are wrong...the F-18 has many of the same components. It’s not an F-16.

 

 

And F18 is not a YF17

 

the evolved F18 was designed around FBW system, unlike older more traditional designs like the F15 which are still fully controlled by mechanical control surfaces ( F15X or F15SE or whatever notwithstanding) , with a Flight control system merely dampening control surfaces, auto trimming, and some other things. Be it analog or even a digital system, what the F15 has does not by definition fall under FLy by wire.

 

The only difference is the Viper to the FBW thing further by the air frame being designed around relaxed stability. F16 has a FFB flight stick that only partially moves. The Hornet has a traditional center stick but although not FFB is still relying sensors to read the movements and transmit the electronics signals via wire to pertinent control surfaces. if FBw system gets knocked all it can do is partially pitch the elevators via hydraulic valve, but they don't work if the engines crap out.

Edited June 10, 2019 by Kev2go

[Rainmaker]

And F18 is not a YF17

 

the evolved F18 was designed around FBW system, unlike older more traditional designs like the F15 which are still fully controlled by mechanical control surfaces ( F15X or F15SE or whatever notwithstanding) , with a Flight control system merely dampening control surfaces, auto trimming, and some other things. Be it analog or even a digital system, this does not by definition fall under FLy by wire.

 

The only difference is the Viper to the FBW thing further by the air frame being designed around relaxed stability. F16 has a FFB flight stick that only partially moves. The Hornet has a traditional center stick but although not FFB is still relying sensors to read the movements and transmit the electronics signals via wire to pertinent control surfaces. if FBw system gets knocked all it can do is partially pitch the elevators via hydraulic valve, but they don't work if the engines crap out.

 

Lol. I am very intimate with what the F-15 does, and doesn’t do. My time around it numbers in the tens of thousands of hours. The F-15 actually has more control authority with CAS than without.

 

1-2-54. It’s all there for reading in the flight manual. It’s not exactly hidden. The aicraft still has the capability of staying in air...

[Kev2go]

Lol. I am very intimate with what the F-15 does, and doesn’t do. My time around it numbers in the tens of thousands of hours. The F-15 actually has more control authority with CAS than without.

 

1-2-54. It’s all there for reading in the flight manual. It’s not exactly hidden. The aicraft still has the capability of staying in air...

 

..... you are again misconstruing what I am conveying. I am not saying aircraft like the F15 would be better off without Flight control, am saying that if said flight control system gets knocked out ( or would stop working for whatever reason) , the F15 can still fully fly without CAS.

 

 

And Of course its supposed more authority than aircraft without any comparable aids. There wouldn't be much point of including such systems if didn't. :doh:

Edited June 10, 2019 by Kev2go

[Rainmaker]

..... you are again misconstruing what I am saying. I am not saying aircraft like the F15 would be better off without Flight control, am saying that if said computer gets knocked out, your precious F15 can still fly without CAS.

 

Lol. I know it can. It’s part of the FCF profile to ensure it.

 

The F-18 can also, for many of the same reasons.