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Inverted physics might need some seeing to.


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56 minutes ago, wowbagger said:

But, if going inverted starts playing that soundtrack in cockpit, don't change anything please.

Could be justified as a consequence of all that blood rushing to your head. :D

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Just glided 200km while only losing 100m altitude.

 

This module keeps surprising me...

 

I also tried to see what happens when you go inverted with the engine on. As expected, you can increase your top speed this way.


Edited by razo+r
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"Everything is [As Intended], you are just flying it unrealistic manner and simulator can't model all unexpected scenarios so it is a user error, fly it as it is expected to be flown in reality"

That is the answer many will find out about some other modules, like "Can you fly Mi-8 upside down?" or "Can you perform a SA342 autorotation while inverted?".

 

I have only once flown Harrier upside down just to fool around to check how long it takes to empty the feeder tank while pulling negative G's.

And if I remember correctly, I rolled inverted around in a 5-8 degree dive angle and then leveled, and it took maybe 10 seconds before my engine did shut down. At the time I didn't know how to perform the air restart as I didn't remember that button is in the throttle and not inside cockpit, but I recall only to exit the session as I didn't want to go further.

 

I am shocked (but not surprised) of your findings like the unlimited fuel and unlimited glide capability and speed increase.

I have been in the believe that Harrier has a feeder tank that needs positive G forces to be filled.... But I still don't know is it so... 

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3 hours ago, Wisky said:

if you empty your feeder while flying inverted the engine is dead. Air Start is not going to help. You can only land and repair at an airfield.

 

Why does the engine get broken if it runs out of fuel?

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vor 16 Stunden schrieb Fri13:

 

Why does the engine get broken if it runs out of fuel?

well coming from a truck i would assume fuel lines pulling air and being rendered unable to keep sucking in more fuel because the vacuum is lost.

the only thing you can do as a truck driver is pull over and start venting the pipes by unscrewing deair screws in the fuel system while pumping in fuel by turning the engine with the starter until most of the air is gone and the engine finally manages to suck enough fuel to get the system running again.

 

but thats just an assumption. what i did say in my first post is: that in dcs you will not be able to air start her back up if your feeder runs dry. just stating a fact


Edited by Wisky
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1 hour ago, Wisky said:

well coming from a truck i would assume fuel lines pulling air and being rendered unable to keep sucking in more fuel because the vacuum is lost.

 

The aircraft has a feeder tank and fuel pumps for that reason. All the other tanks keeps directed to feeder that has largest pipe to the engine. That feeder tank is pressurized so you can feed engine in negative G's for limited time. Once it is empty, you need to let it refill by the fuel pumps and then relight your engine by air starting. The air start usually happens that you need enough speed to rotate the turbine to start it, but Harrier has own special starter why you don't need it as you can just use compressed air to start it up like on the ground.

 

The engine doesn't get broken, why you don't need to fix it.

 

1 hour ago, Wisky said:

but thats just an assumption. what i did say in my first post is: that in dcs you will not be able to air start her back up if your feeder runs dry. just stating a fact

 

No, you said that the engine gets broken and you need to repair it. That is not a fact. 

As I explained before you that if feeder tank gets empty -> no more fuel -> Engine turns off. 

But usually feeder tanks are fed from other tanks only when there is a positive G forces, why when you pull negative G maneuver your feeder doesn't get filled by other tanks and it is only tank to maintain your engine fuel injection. Once it is empty, you need to refill it. Feeder tanks are usually small ones as they are pressurized so they can constantly keep the fuel going in, when more fuel is fed in the feeder, it keeps pumping it to engine. It doesn't get broken because of that.  The procedure when feeder is empty is to maintain a positive G and have fuel pumps transferring fuel to it.

 

Example the MiG-21Bis has a couple min feeder tank capacity in full afterburner at low altitude. The feeder tank (no:3 IIRC) has so huge pipe to the engine that it can keep delivering fuel to it, but all the other tanks pipes are so small to feeder that they can not keep up with the fuel consumption. Why you are limited to 2 minutes full afterburner at low altitude as your engine sucks all the fuel from it. After that you need to wait a moment to get it feeded and relight the engine - hoping you have the required 500 km/h air speed. 

 

This is reason why in airshows the MiG-21Bis pilots are required to pull the throttle back at that two minutes back to mil power so the feeder can be refilled, and then after X seconds able to use afterburner again. 

 

In a Su-27S the times are different again, like 90 seconds negative G in mil power, but with full afterburner it is just 15 seconds.

 

 

The point is that if Harrier fuel tanks can fill the feeder tank while negative G's, then it shouldn't shut down while flying inverted.

 

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From the Harrier flight manual:

A1-AV8BB-NFM-000
Operating Limitations 4.2.3 

 

”Flight in less than 1g conditions must not exceed 15 seconds continuous duration to avoid oil starvation of the engine bearings.”

 

Even if the fuel is not an issue while inverted, starvation of oil will break the engine.

 


Edited by Schmidtfire
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22 hours ago, Schmidtfire said:

From the Harrier flight manual:

A1-AV8BB-NFM-000
Operating Limitations 4.2.3 

 

”Flight in less than 1g conditions must not exceed 15 seconds continuous duration to avoid oil starvation of the engine bearings.”

 

Even if the fuel is not an issue while inverted, starvation of oil will break the engine.

 

Even if the oil starvation starts to happen, it is not imminent result for engine breaking. We should get a rapid increase to engine malfunction after that as the oil that is on the surfaces starts to be moved out and generate more heat etc. 

 

The Harrier In-Air Refueling tutorial (Full) says that there is two feeder tanks in Harrier and they can not pump fuel in negative G more than 15 seconds as the feeder gets empty. So you would run out first the fuel before starting to risk the engine damage because lack of oil. 

Basically this or that, do not fly inverted further than 15 seconds (better to just keep it in few seconds when wiffing or rolling) 

 

But there should now be coming fixes in 2.7 about the drag and fuel. But let's see do they do anything about the oil as well... 

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