Reverse Thrust

[Reddog]

Is there a way to increase the reverse thrust on the default C208B so it will move back ward??

[bstolle]

Download the new FDE from simviation.com or flightsim.com and you can taxi backwards (besides having a much better PT6 simulation as well)

[Reddog]

Download the new FDE from simviation.com or flightsim.com and you can taxi backwards (besides having a much better PT6 simulation as well)

That's what I have and it doesn't move backwards.

[bstolle]

Weird, just tried and even at MTOW she moves backwards. Looks like a throttle calibration issue and you don't get full reverse thrust.
Check with the tooltips enabled. At max reverse the throttle tooltip should read 'reverse 30%'
R U using SP2 or Accel ? The new FDE has been tested only with Acceleration....

[Reddog]

Weird, just tried and even at MTOW she moves backwards. Looks like a throttle calibration issue and you don't get full reverse thrust.
Check with the tooltips enabled. At max reverse the throttle tooltip should read 'reverse 30%'
R U using SP2 or Accel ? The new FDE has been tested only with Acceleration....

using SP1 and SP2, no accl. thottle tooltip says that. checked other turboprops with reverse and they all work.

[bstolle]

using SP1 and SP2, no accl. thottle tooltip says that. checked other turboprops with reverse and they all work.

Then it's most probably that you don't have acceleration installed as this definitely improves engine/prop behaviour.
What you can do is to increase the reverse thrust in the cfg file.

[GeneralEngineData]m
min_throttle_limit = -0.30

Just increase the min_throttle_limit up to -100%

BTW, reverse does work but it doesn't necessarily means that you can taxi backwards...

[thunder100]

A big trigger of Reverse trust on Prop's is here

[propeller]
fixed_pitch_beta = 0
low_speed_theory_limit = 80
prop_sync_available = 0
prop_deice_available = 1
prop_feathering_available= 1
prop_auto_feathering_available= 1
min_rpm_for_feather = 400
beta_feather = 88
power_absorbed_cf = 1
defeathering_accumulators_available= 0
prop_reverse_available = 1
minimum_on_ground_beta = 15
minimum_reverse_beta = -15

But be careful with it can have odd other effects

Roland

[bstolle]

A big trigger of Reverse trust on Prop's is here
[propeller]
minimum_reverse_beta = -15

Not really, as the advance ratio is extremely low at that speed and hence the effectiveness very low regardless of the blade angle.
Especially with the new 208 FDE which has a completely new and much more realistic prop.

[Reddog]

Then it's most probably that you don't have acceleration installed as this definitely improves engine/prop behaviour.
What you can do is to increase the reverse thrust in the cfg file.

[GeneralEngineData]m
min_throttle_limit = -0.30

Just increase the min_throttle_limit up to -100%

BTW, reverse does work but it doesn't necessarily means that you can taxi backwards...
I know, it does work in slowing the a/c down on landing. Will try your suggestion.

BTW, does Static Thrust have anything to do with it?? The reason I ask is that on my other a/c that do work the ST= is a lot higher than on your 208.

[bstolle]

BTW, does Static Thrust have anything to do with it?? The reason I ask is that on my other a/c that do work the ST= is a lot higher than on your 208.
ST is realistic, but works in the opposite direction (when talking about moving backwards), so increasing ST would actually counter reverse thrust created by the prop.

[mal998]

Use number shown below and she will back up very nicely using F2 key:

prop_reverse_available = 3 //1 unfortunately MS does not always remark some of their parameters accurately

the higher this number the faster she will back up. if you have a rudder control you will be able to steer her R/L backwards. use F1 to disengage. be careful using brakes when backing up she will end up on her tail.

[bstolle]

That's the perfect solution !!! Thanx a lot for that one :)
Every other mentioned solutions has the serious drawback of screwing up Ng, Np or both.....

[Reddog]

Use number shown below and she will back up very nicely using F2 key:

prop_reverse_available = 3 //1 unfortunately MS does not always remark some of their parameters accurately

the higher this number the faster she will back up. if you have a rudder control you will be able to steer her R/L backwards. use F1 to disengage. be careful using brakes when backing up she will end up on her tail.

That did it works now. Thanks for that tip.

[mal998]

Happy to help.

[napamule]

Trouble is that any wind, even 5 kts, will 'hold' the ac where it won't move in reverse sometimes. The solution lies in the amount of 'maximum_torque' available.

[turboprop_engine]
maximum_torque= 15900.000 //orig=10614.000 //Max torque available (ft-lbs)

THIS is where you control how effective the reverse thrust is going to be (to overcome wind, uphill climb, cnt pt drag, etc). The line above is the 'important' one as far as how MUCH reverse thrust you are going to get (thus 'overcome' wind, etc). Try it and see. It's NOT the 'static thrust'. Static thrust can be -99999.000. No matter.

Other Tips:
*Adjust the 'maximum_torque=x' value until you get ac to move easily at the above 'min_throttle_limit' value (in (General_Engine) section-usually '-0.14' but can be as much as '-0.39' or so). It's all easier if you have a gauge that shows % of power (throttle) to 'see' 'min_throttle_limit'. Using F3 to reduce amount of 'min_throttle_limit' will allow some 'control' of how fast ac moves. When torque is too much you can reduce the min throttle limit (trial & error). Play one against the other. Every model is different.

*When you are in reverse thrust and press F1 you will jump forward 30 ft with Turbo-Props especially. To prevent this, press F3 (2 times), F2 (2 times), back & forth, about 3 times and ac will not jump.

*To prevent tail strike due to brake while moving in reverse, make sure that the value of 'empty_weight_CG_position' is at least +1 more than 'reference_datum_position' value (it's longitudial value). This can be +2, or +3 more. Trial & error will determine which value works best. At any rate, this is where you adjust for no tail strike due to braking when moving back in reverse thrust. Not cnt pts or moving engines or fuel tanks. OK? OK! Happy reverse in FSX to you all.
Chuck B
Napamule

[mal998]

If you change the COG numbers, the flight dynamics of the aircraft may be affected.

[napamule]

mal998,
You are right. It will prevent the backwards tip on brake when moving in reverse. A '+1' value increase, per se (ie: on it's own), is not going to RUIN the dynamics/handling. That is not possible.

And while we are disgusting things: what happens if I enter: 'prop_reverse_available= -1' ? Have you tried it? How about a value of '-3'? Have you tried that? Quote: ' // unfortunately MS does not always remark some of their parameters accurately'. They also did not run any 'trial & error' tests for values other than 1 or 3? I did.
Chuck B
Napamule

[bstolle]

1.The solution lies in the amount of 'maximum_torque' available.
[turboprop_engine]
maximum_torque= 15900.000 //orig=10614.000 //Max torque available (ft-lbs)
THIS is where you control how effective the reverse thrust is going to be
2To prevent tail strike due to brake while moving in reverse, make sure that the value of 'empty_weight_CG_position' is at least +1 more than 'reference_datum_position' value (it's longitudial value).

1. If you increase mx torque you not only change reverse thrust but forward thrust as well, totally ruining the performance going backward and forward.
2. Why do you want to prevent a tail strike when moving in reverse? That's exactly what happens IRL as well
BTW, altering the CG by 1ft or more seriously affects handling!

[mal998]

Changing the COG could change the nose up/down attitude and the climb/decent characteristic of the aircraft when airborne.

[napamule]

Quote:'It COULD effect handling'. A strong wind could do the same. What I suspect 'happened' is that you inherited a set of lousy FDE's and ANY change anywhere COULD (of course) be 'blamed' for ruining the handling. It's just so easy to ASSUME things are a certain way, and set in concrete, because 'that's the way it's always been...'. Or, was 'made up' to apease the crowds. Like the nose up attitude. The horiz stab incidense does more to effect THAT than the CofG ever (EVER!!) will. But I am talking to the hand I imagine. Cheesh.

This is why I hate to discuss flight dynamics because there is always one or two that will argue all day about something that does not apply to flight simulator at all (although it DOES apply to 'real' flying). 1 ft change to CofG does NOT ruin your handling IN FLIGHT SIMULATOR. A bad set of FDEs (dynamics) WILL ruin your handling. Don't mix them up. And don't cite real dyanmic parameters to 'apply' in flight simulator. It just don't work that way. Flt Sim is DIFFERENT to real. Even flying ac in sim is different. OK? OK! So don't change anything. Leave your FDEs the way they are. Fly like you alway fly. Rely on the modeler to provide you with instructions ('how to fly') in the 'ReadMe' txt file. Right? Right. And ck the various forums for 'no reverse thrust', 'bounce on landing', 'shaking sitting on runway', 'tip over on tail on brake when in reverse', 'airplane won't turn on taxi', etc, etc. It's all there. Over and over. Same ole questions. Again and again. Something has GOT to change, I do believe. But, minds are hard to change. That I know.
Chuck B
Napamule

[bstolle]

Quote:'It COULD effect handling'. A strong wind could do the same.
And don't cite real dyanmic parameters to 'apply' in flight simulator. It just don't work that way

Don't know where your weird aggressiveness comes from but:

A strong wind affects handling???? The plane doesn't care at all if its flying straight and level with 0kts wind or 50kts wind.
Of course real flight dynamics work in FSX, you just can't simply use real world numbers.

BTW:
1. A too far aft CG will reduce pitch stability (like IRL)
2. A too far forward CG can prevent you from stalling the plane due to too little elevator power (also like IRL)

[napamule]

bstolle,
I am not agressive in any way. This is 'shop talk'. If you are not scientifically adept (ie: aeronautical engineer or mechanically inclined) then don't INVENT stuff. I am sorry, but you are using terminology that is not scientific. It's also vague. What is 'too far' for 'aft CofG' (did not know there was a SET reference position for CofG). By sheer OBSERVATION you can determine, and I am sure you will agree, that ALL models (default and 3rd party) are all DIFFERENT when it comes to CofG. It's never at the same point as the other aircraft. If you don't agree then I contend you don't have enough FDEs experience. Either you know it, or you don't. There is no guessing.

You say 'too far' 'aft CofG' will 'reduce pitch stability'. What does THAT mean? You can't pull up? Or you can't nose dive? Or the aircraft will not stay level? If it's the latter then you need to learn to use elevator pitch trim, as IRL.

Then you say 'too far' 'forward CofG' will prevent stalling due to 'elevator power'? What elevator power? If you cut throttle and pull nose up it will stall when it reaches a certain speed. So you don't have enough elevator area? Your elevator up/down limit(s) are not right? Your controls elevator axis is not calibrated? Your (flight tuning) entry for pitch stability is =5.0? It don't make any sense to blame ONLY the CofG. That's not scientific. Or true. Why? Because a lot of cfg entries are WRONG and no one is the wiser. It's 'tradition' to let some 'nube' (or program) do the 'brain work' for you and then you just accept it without any question. Not scientific.

You say a 'strong wind'. (I said a 5 kt wind will prevent you from backing into the wind if you are using reverse thrust and you only adjust (1). 'prop_reverse_available= 1' and (2). 'min_throttle_limit= -0.35'. Please define 'strong wind' and whether you can move backward against it using reverse thrust. And if not, what would you adust to remedy this. This is the original theme of thread, you know. Setting CofG to '=1.000, 0.000, 0.000' will NOT cause/lead to 'too little elevator power' (?) or 'reduce pitch stability' (?). Bogus.
Chuck B
Napamule

[bstolle]

1. If you are not scientifically adept (ie: aeronautical engineer or mechanically inclined) then don't INVENT stuff. I am sorry, but you are using terminology that is not scientific.
2. You say 'too far' 'aft CofG' will 'reduce pitch stability'. What does THAT mean? You can't pull up? Or you can't nose dive? Or the aircraft will not stay level? If it's the latter then you need to learn to use elevator pitch trim, as IRL.
3. If you cut throttle and pull nose up it will stall when it reaches a certain speed.


1. ROFL
2. As you apparently don't even know what reduced pitch stability means, this discussion is totally useless.
3. wrong

Have a nice day :)

[napamule]

bs,
Quote: 'Please define 'strong wind' and whether you can move backward against it using reverse thrust. And if not, what would you adust to remedy this. This is the original theme of thread..'

About 'reduced pitch stability' (whatever this means), will this do?
Longitudinal static stability is the stability of an aircraft in the longitudinal, or pitching, plane under steady-flight conditions. This characteristic is important in determining whether a human pilot will be able to control the aircraft in the longitudinal plane without requiring excessive attention or excessive strength.

A mathematical analysis of the longitudinal static stability of a complete aircraft (including horizontal stabilizer) yields the position of center of gravity at which stability is neutral. This position is called the neutral point. (The larger the area of the horizontal stabilizer, and the greater the moment arm of the horizontal stabilizer about the
aerodynamic center, the further aft is the neutral point.) The static center of gravity margin (c.g. margin) or static margin is the distance between the center of gravity (or mass) and the neutral point. It is usually quoted as a percentage of the Mean Aerodynamic Chord. The center of gravity must lie ahead of the neutral point for positive stability (positive static margin). If the center of gravity is behind the neutral point, the aircraft is longitudinally unstable (the static margin is negative), and active inputs to the control surfaces are required to maintain stable flight.

Some combat aircraft that are controlled by fly-by-wire systems are designed to be longitudinally unstable so they will be highly maneuverable. Ultimately, the position of the center of gravity relative to the neutral point determines the stability, control forces, and controllability of the vehicle.

Quote: 'this discussion is totally useless'. I say I need to know if your ac will move backwards into a wind of 5 kts in FSX by using reverse thrust, and if not, what adjustment(s) would YOU make to aircraft cfg or air files? Help me out here. Forget the attitude.

And: To repeat: Moving the CofG 'forward by 1 foot' will not 'ruin' your dynamics (handling or stability) but IN FACT it will INCREASE your 'stability'. I hope you don't continue to argue against the facts on this point. But it's the reverse thrust question that needs answering. Anytime this week is 'ok'.
Chuck B
Napamule

[mal998]

"Could 'a Would 'a

Quote:'It COULD effect handling'. A strong wind could do the same. What I suspect 'happened' is that you inherited a set of lousy FDE's and ANY change anywhere COULD (of course) be 'blamed' for ruining the handling. It's just so easy to ASSUME things are a certain way, and set in concrete, because 'that's the way it's always been...'. Or, was 'made up' to apease the crowds. Like the nose up attitude. The horiz stab incidense does more to effect THAT than the CofG ever (EVER!!) will. But I am talking to the hand I imagine. Cheesh.

This is why I hate to discuss flight dynamics because there is always one or two that will argue all day about something that does not apply to flight simulator at all (although it DOES apply to 'real' flying). 1 ft change to CofG does NOT ruin your handling IN FLIGHT SIMULATOR. A bad set of FDEs (dynamics) WILL ruin your handling. Don't mix them up. And don't cite real dyanmic parameters to 'apply' in flight simulator. It just don't work that way. Flt Sim is DIFFERENT to real. Even flying ac in sim is different. OK? OK! So don't change anything. Leave your FDEs the way they are. Fly like you alway fly. Rely on the modeler to provide you with instructions ('how to fly') in the 'ReadMe' txt file. Right? Right. And ck the various forums for 'no reverse thrust', 'bounce on landing', 'shaking sitting on runway', 'tip over on tail on brake when in reverse', 'airplane won't turn on taxi', etc, etc. It's all there. Over and over. Same ole questions. Again and again. Something has GOT to change, I do believe. But, minds are hard to change. That I know.
Chuck
Napamule"


Chuck, Chuck, Chuck,

I never said anything COG "ruining" handling. I said it may affect the attitude of the aircraft while in flight. Oh and BTW, I already answered the question to which the original poster responded by saying "That's the perfect solution !!! Thanx a lot for that one. Every other mentioned solutions has the serious drawback of screwing up Ng, Np or boththanks it works"

And to be clear, I don't inherit things, I build them. You can try out my latest macinations when you fly Virtavia's new F-111. That would be my flight dynamics that you'll be enjoying, as I did the files for that little beauty.

But, you're the expert here so I'll leave you to your strongly held point of view, napa-mule.

[napamule]

You wanted to promote your Virtavia F-111. Ok, fair enough. But since I don't buy (or ever intend to) any add ons I will never 'enjoy' your 'creation' (yeah right).

Send me the model and I will run it through my hanger and fly it and give you feedback. I want to know what 'PERFECT' FDEs (according to you) look like. (And from Virtavia, no less-go figure).
Chuck B
Napamule
'Napamule' means 'Napa Auto Parts' delivery driver (or 'mule'). My last job before I retired. I wouldn't make fun of your 'handle'. Your face, maybe. But not your username.

[Rich]

Sorry would someone who has the ability please put the clampers on this thread it gets so boring when the great I am keeps sticking his oar in.



:sleep::sleep:

[Moparmike]

Well guys,

The OP has found a solution to his problem and offered thanks. After that, a lively discussion on flight dynamics in real-world and FSX (yes, they can intermingle). And lastly, the name-calling has begun...

That means it's time to shut it down and move on to other things.