Thrust Reverser on Touchdown

[MBot]

According to the manual, the thrust reverse should engage on main wheel touchdown:

 

The thrust reverser flaps will close when the right main landing gear is depressed if reversal is pre-selected. To avoid reversing in an unstable attitude, the reverser flaps will open again after 1 second unless the nose landing gear is compressed. The reverser system will reengage when the nose gear is compressed again. In order to achieve the shortest distance possible, the nose gear should touch the ground as soon as possible after touch down with the main landing gear.

 

In game this is not the case, the thrust reverser only engages on nose gear compression.

[TOViper]

According to the manual, the thrust reverse should engage on main wheel touchdown:

In game this is not the case, the thrust reverser only engages on nose gear compression.

 

I remember Cobra847 writing somewhere that they had problems with the engagement of the reverser someday (due to an update), thus he had to program a work-around in order to make it "work" again.

Something with ED stuff bla bla code break update ...

 

 

 

Don't know if this work-around has ever been on the screen again ...

[outbaxx]

What do you mean exactly? That the flaps don’t start to close when the main gear is compressed? (I guess you would need to look in external view to see this?)

 

According to your quote the nose gear need to compress within 1 second after main gear compression or the closing of the flaps will abort until the nose gear is compressed.

So the nose gear need to be compressed or else the thrust reverser will abort.

 

Cheers

[MYSE1234]

It takes about 1,5 seconds for the flaps to fully close/ open. So unless you compress the nose gear it's not going to be fully closed before it starts to open again.

[frosen]

In game this is not the case, the thrust reverser only engages on nose gear compression.

 

It should only engage on nose wheel touchdown. Regarding the closing of the engine petals I don't know but the function described in the manual sounds likely. If I understand your post correctly there seems to be nothing wrong with how the reverser system works.

[TOViper]

What is written in the manual makes sense to me.

 

 

Just a few thoughts, having in my head a good landing with both main landing wheels on ground):

If I land with 2.96 m/s sink rate (this is maximum allowable for the landing gear), and with a speed less than 320 km/h (this is maximum tyre speed), the AOA - depending on current mass - will be hopefully somewhere around 12° (a little less or more), and pitch attitude somewhere around 9° (a little less or more).

This means - to me - the nose will come down within 1 second after the main landing gear has hit the runway (therefore the 9° of pitch attitude must be "eliminated" by rotation of the aircraft around the axis created by the main landing gear wheels).

 

This action with the intention to avoid that the clam shell doors (in the manual labelled as "flaps" - which I personally consider bad naming) to be opened again.

To have short landing distances, it is a requirement to bring the nose down very quickly ...

 

I will do some tests today if the clam shell doors open again 1 second after I touched the ground with the right main landing gear only.

Will be not too easy, but worth a try. :joystick:

 

 

I love all this ... :)

Edited August 9, 2019 by TOViper

[MBot]

It should only engage on nose wheel touchdown. Regarding the closing of the engine petals I don't know but the function described in the manual sounds likely. If I understand your post correctly there seems to be nothing wrong with how the reverser system works.

 

I don't understand why you emphasise engage versus closing. On touchdown the engine is spooled up. If the flaps are open, the trust goes out of the back end. If the flaps are closed, the thrust is deflected forward.

 

Right now the flaps dont close on main gear touchdown as described in the manual but only after nose wheel touchdown.

[frosen]

I don't understand why you emphasise engage versus closing. On touchdown the engine is spooled up. If the flaps are open, the trust goes out of the back end. If the flaps are closed, the thrust is deflected forward.

 

Right now the flaps dont close on main gear touchdown as described in the manual but only after nose wheel touchdown.

 

Because according to the original aircraft documentation (in Swedish), the thrust reverser should only engage (i.e. produce reverse thrust) when the circuit breaker in the nose wheel assembly is closed which happens when it is depressed. I assume that as long as the petals is not 100% closed the exhaust gases will still escape backwards (although with a higher pressure) which still produce forward thrust. If the closing initiates before the nose wheel is depressed it will still not have time to engage (i.e. close entirely) if the circuit breaker isn't closed within a second, because as someone stated, it will take about 1.5 seconds to close the petals and the petals will reopen before that happens.

 

Ergo, you will only have effective reversed thrust with the nose wheel down.

[MBot]

Thanks for the explanation, I don't know the flight manual and can only go by HB's own documentation.

 

In any case, in DCS the flaps will not start to close until nose gear compression which is still wrong then.

[TOViper]

... If the closing initiates before the nose wheel is depressed it will still not have time to engage (i.e. close entirely) if the circuit breaker isn't closed within a second, because as someone stated, it will take about 1.5 seconds to close the petals and the petals will reopen before that happens.

 

Difficult to read, but I think I can summarize what happens in real life (for me) like this:

 

Situation 1, all good and timely managed:

Event 1: If right main wheel touches ground, clam shell doors begin close (but they will not close fully, it takes some time)

Event 2: Then, if the nose wheel touches ground within one second measured from event 1, the doors continue to close due to the - now closed - switches in the nose landing gear, and therefore the reverser will be fully closed - and thus ready for engagement - a half second after touchdown of nose landing gear.

 

 

My assumption based on your post:

Situation 2, is when the 1 second time span to bring down the nose landing gear is exceeded. I think then the reverser - in its "half open" position, will re-open again, giving the pilot the chance to fly a touch-and-go.

 

Writing is so difficult sometimes ... let's meet and use a big sheet of paper and a pencil ... :smilewink: And a few beers.

[MBot]

That is an excellemt summary TOViper and also how I expect it to work. In DCS that is currently not the case.

[TOViper]

That is an excellemt summary TOViper and also how I expect it to work. In DCS that is currently not the case.

 

 

Damn, and I thought this evening I could do some tests, in the attempt to earn the Nobel Prize for best-intense-testing the DCS Viggen. :megalol:

[MBot]

Any news on reverser closing on main gear touchdown?

[TOViper]

Hi MBot!

 

Haven't heard/read anything about this. According to my perception during the last weeks it is a bit quite around the Viggen ... hopefully because RagnarDa is coding/improving our beloved beast to make it the perfect beast ... :D