Why is the DCS F16 departing controlled flight after pilot ejection?

[darkman222]

That may sound like a stupid question. But why does the DCS F16 depart from controlled flight after pilot ejection? Looks like the FLCS gets disconnected and the aircraft gets into an unstable flight condition as it would if the FLCS failed. Is it realistic? Or is it just game design that other players know that this F16 is dead?!

Seems to behave differently in multiplayer and single player. In MP the F16 likes to pull up and snap its wings. In SP it just slowly banks down into the ground after ejection.

Edited November 8, 2021 by darkman222

[alexscott292]

Relaxed static stability.

Conventially designed aircraft have the centre of gravity ahead of the aerodynamic centre which is counterbalanced by the tail creating a balancing downward force.  The F-16 locates CofG behind the aerodynamic centre.  Eject a huge mass out of the front and the CofG moves so far back the stability becomes unmanagable.

 

I can't explain the difference between MP and SP.

[Frederf]

It's a really interesting question what FLCS and the rest of the airplane does on ejection. It looks like in DCS the control surfaces remain in the last position prior to ejection which can cause some really interesting behavior. I wonder what really happens. Would the controls neutralize since the pilot has done the ultimate "let go"? Does the FLCS have a particular routine triggered by ejection? Does the engine auto-shut down? Is electrical power interrupted

[darkman222]

Thats my question. Exactly. What would engineers design for that case? I would assume that the best case would be if the aircraft just should continue to fly the last direction. So the pilot can point the aircraft where he wants it to crash, after he ejected.

A shift of the center of gravity would ocurr. But I googled that the seat weighs about 70 kg plus the pilot 80 kg. Thats a weight shift of 150 kg in front of the COG. The F16 compensates quick and well if you'd jettison all stores simultaneously. Not really sure about that explanation, although the pilot and seat are really far away in front of the COG.

And if the controls surfaces remained in the last position, although the pilot would have let go of the stick, if the FLCS still remains functional, but kept the last input, it would prevent the jet from snapping the wings anyway.

I guess there is some game design going on here. Imagine on multiplayer if you followed an F16, you did not see the pilots ejection of and you keep following him for 15 minutes in afterburner just realizing there was no actual player in it

Edited November 11, 2021 by darkman222

[Frederf]

One thing I consider is if an ejection is commanded but the pilot doesn't leave (faulty signal, faulty seat) he absolutely wants to remain in control of the engine and FLCS. What about 2-seat models? The simplest system is not to do anything different when the meat bag leaves. If a bird flies up and moves the throttle the engine changes. If he nudges the stick it moves the surfaces. That's my guess. Sticking in last commanded position seems not likely.

[Machalot]

Make sure to distinguish between two conditions:

1. control inputs remain at last position

2. control surfaces remain at last position

In case 1, the FLCS could continue to function and maintain the last commanded G and roll rate.  The aircraft might be pulling up or down, rolling left or right, and would just continue on its curved path until it either stalls or crashes.

In case 2, the FLCS no longer has a job, and the aircraft will depart and tumble (if it is in a statically unstable configuration, i.e. negative static margin aka "relaxed stability").  I don't know if the F-16 has any fuel/payload configurations that are statically stable (positive static margin) before or after pilot ejection, but in that case (if rolled upright and depending on power setting) the jet would likely enter a phugoid oscillation and gradually spiral to the ground.  If the thrust setting is high enough to provide excess power, it could climb for a long time before running out of fuel.

[Frederf]

In DCS it's surfaces, they're locked. A constant stick input in pitch would involve the tailerons moving.

I might try a few other airplanes. They might all go frozen surfaces in the sim including ones without any hydraulic controls. EDIT: Yeah even a Bf-109K-4 with full rudder will freeze full rudder on bailout which makes no physical sense.

Edited November 12, 2021 by Frederf

[Tormox]

Another point worth considering is the force applied to the control stick by the seat rocket motor firing. It is just an educated guess, but on the basis of how cockpits are arranged I would not consider impossible that, upon pilot ejection, the seat rocket fires and the deriving blast pushes the stick forward, hence determining the aircraft to pitch down (provided the FLCS still works)

[Machalot]

1 hour ago, Frederf said:

In DCS it's surfaces, they're locked. A constant stick input in pitch would involve the tailerons moving.

I might try a few other airplanes. They might all go frozen surfaces in the sim including ones without any hydraulic controls. EDIT: Yeah even a Bf-109K-4 with full rudder will freeze full rudder on bailout which makes no physical sense.

 

Seems like DCS may just stop the aircraft systems sim on ejection.

[Falconeer]

On 11/11/2021 at 9:53 PM, darkman222 said:

A shift of the center of gravity would ocurr. But I googled that the seat weighs about 70 kg plus the pilot 80 kg. Thats a weight shift of 150 kg in front of the COG. The F16 compensates quick and well if you'd jettison all stores simultaneously. Not really sure about that explanation, although the pilot and seat are really far away in front of the COG

If we remove the seat and canopy for maintenance and we would not put the jet on jacks or remove the engine (yes, it happens for seat/canopy removal) the f16 wil tip over and sit on its tail

As a matter of fact, there is a diagram in the books, showing which actions you should take if you are removing components from the jet to prevent tipping over 

Edited November 12, 2021 by Falconeer

[darkman222]

Right, the canopy goes too. That adds to the pilot and seat weight loss. Now we have about 300 kg of weight loss in the front of the jet. But, wouldnt a functional FLCS still be able to compensate that?

[Machalot]

1 hour ago, darkman222 said:

Right, the canopy goes too. That adds to the pilot and seat weight loss. Now we have about 300 kg of weight loss in the front of the jet. But, wouldnt a functional FLCS still be able to compensate that?

It might be physically possible depending on the size and power of the elevons and actuators.  But we don't know if the FLCS is scheduled to function in that mass configuration, nor if it is notified of (or can detect) the change in mass properties. 

Edited November 14, 2021 by Machalot

[Nealius]

On 11/9/2021 at 7:14 AM, darkman222 said:

Seems to behave differently in multiplayer and single player. In MP the F16 likes to pull up and snap its wings. In SP it just slowly banks down into the ground after ejection.

MP seems to have a lot of issues when it comes to transmitting client aircraft data to the server then back to the client(s). I've seen jets pop wheelies on catapult shots and jets in a flat spin warp their nose between positions in the spin instead of smoothly spinning, etc. The faster the object moves the more trouble the data has in getting transfered. Just a flaw in the code. 

Edited November 14, 2021 by Nealius

[TobiasA]

The question is: Why do you guys eject from a plane that is still flying straight?

[darkman222]

Short answer: On a dogfight multiplayer server: Out of fuel or out of ammo.

Not very realistic either I know

[darkman222]

Seems to be a DCS thing. Yesterday my virtual pilot got shot when I was fighting on a MP server, while I had the guns button depressed. I was watching my aircraft from the outside drawing nice tracer circles. So I guess when you eject its the same like the pilot being dead. The last input is kept. Which will be of course most of the time pulling up when ejecting.