Beta range simulation

[josecolme 9]

I know that MSFS itself isn't very good at simulating the ranges of operation of propellers, but I just wanted to make sure if it was on my side or the plane itself. If I move the throttle from idle forward, only fuel flow moves up to a certain point with no indication other than fuel flow. This is beta range, and given what I said earlier, it can possibly explain that. But It shouldn't not have any indications at all. I remember that moving the throttles slightly on the real plane, even on the ground, would give an increase in all parameters. Also, I believe this has already been noted by somebody else with proper numbers, but the reaction of moving the prop lever to a different setting has too little of an effect on the torque value. A common practice we had to set climb or cruise was to set 5 psi less trq than required and lower the props to the needed value. This would set the trq almost exact to the desired value. The sim does simulate this reaction but the values don't correspond to the actual aircraft.

 

Hopefully this input is of some value. I'd be glad to help out in making this a better product for all.

 

[Jan R. Storelvmo 67]

As far as I know beta range is not simulated yet. This totally breaks the turboprop experience. Asobo promised to fix all turboprop issues by sim update 6. This has not happened yet. There are still many open issues. There's also a new QA session on Wednesday with Asobo, so I hope this issue will be brought up. 

[metzgergva 210]

The reaction on TQ when changing prop RPM in flight has been verified multiple times with the consulting pilot. Same is valid for the total TQ range.

Beta range is defined as changing prop blade angle from low idle to idle reverse. In this range the prop moves from +10° to -15°. That is simulated and can be activated by pressing F2 or using a throttle control setting that allows the whole throttle lever travel. It is also underlaid with a sound change and can be used very well for reducing roll forward to stop and reverse roll action.

[josecolme 9]

19 hours ago, metzgergva said:

The reaction on TQ when changing prop RPM in flight has been verified multiple times with the consulting pilot. Same is valid for the total TQ range.

Beta range is defined as changing prop blade angle from low idle to idle reverse. In this range the prop moves from +10° to -15°. That is simulated and can be activated by pressing F2 or using a throttle control setting that allows the whole throttle lever travel. It is also underlaid with a sound change and can be used very well for reducing roll forward to stop and reverse roll action.

That I understand, sorry if I didn't explain myself well. What I mean is in the positive spectrum of the propeller's operating range. When I move the power levers from idle forward, there is only a fluctuation of fuel flow and nothing else. up to maybe one fourth or a third of travel of my throttle quadrant do the other parameters start to react. I doubt that it is a calibration issue, otherwise fuel flow wouldn't move either. In real life, the initial reaction of Ng and Trq happens a lot earlier than this. Just for the record I am in no way trying to contradict the consulting pilot as I'm sure it's somebody with good twin otter experience (probably more than me). I speak from my own, I have about 1000 hours on it. So again I do offer my help as I actually love the work you guys have done and would like to help and make it better.

[josecolme 9]

Well, it seems that after the update some work must have been done because that issue isn't present anymore. Now I have inverted ailerons. But that is so evident I'm sure that will be fixed soon.

Keep up the good work!

[malc_yorks 0]

On 1/25/2022 at 9:47 AM, metzgergva said:

... or using a throttle control setting that allows the whole throttle lever travel....

 

I have not spent a lot of time trying to get this to work (only bought the twotter a couple of days ago) and not had much success.  Is there a way of setting this in MSFS controls or should I start trying to do this via FSUIPC? (I use CHPro Yoke and Pedals, no throttle quadrant.)

 

[teeloo 18]

On 1/26/2022 at 6:16 AM, josecolme said:

That I understand, sorry if I didn't explain myself well. What I mean is in the positive spectrum of the propeller's operating range. When I move the power levers from idle forward, there is only a fluctuation of fuel flow and nothing else. up to maybe one fourth or a third of travel of my throttle quadrant do the other parameters start to react. I doubt that it is a calibration issue, otherwise fuel flow wouldn't move either. In real life, the initial reaction of Ng and Trq happens a lot earlier than this. Just for the record I am in no way trying to contradict the consulting pilot as I'm sure it's somebody with good twin otter experience (probably more than me). I speak from my own, I have about 1000 hours on it. So again I do offer my help as I actually love the work you guys have done and would like to help and make it better.

 

Fully agree. Same thoughts here. I thought the aerosoft version has a beta-ish ranger from Idle to about 1/4 or 1/5 on the power levers as no torque is generated. 

[Jan R. Storelvmo 67]

On 1/26/2022 at 6:16 AM, josecolme said:

That I understand, sorry if I didn't explain myself well. What I mean is in the positive spectrum of the propeller's operating range. When I move the power levers from idle forward, there is only a fluctuation of fuel flow and nothing else. up to maybe one fourth or a third of travel of my throttle quadrant do the other parameters start to react. I doubt that it is a calibration issue, otherwise fuel flow wouldn't move either. In real life, the initial reaction of Ng and Trq happens a lot earlier than this. Just for the record I am in no way trying to contradict the consulting pilot as I'm sure it's somebody with good twin otter experience (probably more than me). I speak from my own, I have about 1000 hours on it. So again I do offer my help as I actually love the work you guys have done and would like to help and make it better.

 

Same here. While I've never flown a Twin Otter in real life, I did some testing with a friend of mine who owns the Twin Otter. All I can say is something is definitely off with the way beta range is simulated. Hopefully this will be improved with SU 8. 

I also noticed you seem to need a lot of breakaway power to get the plane moving from a stand still. This tendency is also present with other turboprops like the Kodiak and default Caravan. 

 

One question: When in-flight with the power levers at idle at 75% rpm. What happens in the real Twin Otter when you set the prop rpm levers to max with the power levers at idle? In the sim they there are no changes in rpm. I used to fly the Dash 8 (different engines than the Twin Otter), and on this plane the rpm is constant regardless of powersetting. When you go from cruise rpm to max on short final, you get max rpm even with power levers at flight idle. You also get significant drag due to the fine pitch. 

[C525B 13]

On 1/29/2022 at 8:48 AM, Jan R. Storelvmo said:

One question: When in-flight with the power levers at idle at 75% rpm. What happens in the real Twin Otter when you set the prop rpm levers to max with the power levers at idle? In the sim they there are no changes in rpm. I used to fly the Dash 8 (different engines than the Twin Otter), and on this plane the rpm is constant regardless of powersetting. When you go from cruise rpm to max on short final, you get max rpm even with power levers at flight idle. You also get significant drag due to the fine pitch. 

 

Reference material: https://www.youtube.com/watch?v=V_-qDEAfRig

 

I think what you're talking about is the airspeed/power where the props fall off the governors.  When the video starts, they're 100 KIAS, prop levers are full aft, and torque is showing zero (so probably flight idle).  FO pushes the props full forward and there is no increase in RPM.  Then CA adds power to about 10PSI at 70 KIAS and there is almost no change in RPM.  So, I'd say yes...the props should be well off the governors on approach and the Aerosoft Twotter is pretty accurate in this regard.

[IGrant 51]

The engine and prop behavior seem pretty well simulated outside the current limitations of the sim. Remember that the props maintain RPM by changing blade pitch which takes a bigger bite out of the air. They effectively use the air for leverage against the force that the engine is putting through them to maintain the requested RPM. At low power and high RPM settings, the engine may not be exerting enough force to require the blades to bite. You won't see torque rise until they need to. Think of if you had to limit a motorboat's top speed by putting oars into the water. If the motor wasn't pushing out enough power to even reach the top speed, you wouldn't have to put the paddle in the water. If the motor was a full throttle you'd have have the oar fully in the water which would be exerting a tremendous amount of force on the water.

 

Beta range is where the prop blades will move independent of engine power and doesn't work at all like the normal range you are used to. It's effectively the other way around, and is something that every MS/LM flight sim hasn't really gotten right to date.

 

To address the OP, correct, there is no torque rise at very low throttle positions but the turbine speed does increase (bottom engine guages).

[Jan R. Storelvmo 67]

2 hours ago, IGrant said:

The engine and prop behavior seem pretty well simulated outside the current limitations of the sim. Remember that the props maintain RPM by changing blade pitch which takes a bigger bite out of the air. They effectively use the air for leverage against the force that the engine is putting through them to maintain the requested RPM. At low power and high RPM settings, the engine may not be exerting enough force to require the blades to bite. You won't see torque rise until they need to. Think of if you had to limit a motorboat's top speed by putting oars into the water. If the motor wasn't pushing out enough power to even reach the top speed, you wouldn't have to put the paddle in the water. If the motor was a full throttle you'd have have the oar fully in the water which would be exerting a tremendous amount of force on the water.

 

Beta range is where the prop blades will move independent of engine power and doesn't work at all like the normal range you are used to. It's effectively the other way around, and is something that every MS/LM flight sim hasn't really gotten right to date.

 

To address the OP, correct, there is no torque rise at very low throttle positions but the turbine speed does increase (bottom engine guages).

 

Thanks for the answer. The reason for asking is that I'm used to the Dash 8 which has different types of engines. I was just curious regarding how the Twin Otter works compared to the Dash 8. It's been waaaay too long since I did my ATPL subjects and PT6 theory  

[Jan R. Storelvmo 67]

A few more questions;

 

Is beta allowed in-flight on the Twotter? Is it possible (technically) to go into beta when airborne?

Is there a mechanical stop for the power levers at flight idle like on the Dash 8? On the Dash 8 you have to lift the gates on the power levers to go into disc (beta). 

 

Also, no prop sync for the Twotter?

[metzgergva 210]

In reality there is a idle stop on the PL. If you look carefully at the videos, the handles can rotate a bit and that little wire on the left side is unlocking the stop to go into beta and then into reverse.

That stop and rotation is not modeled....plain speaking too complicated and not foreseen in MSFS.

[IGrant 51]

5 hours ago, Jan R. Storelvmo said:

A few more questions;

 

Is beta allowed in-flight on the Twotter? Is it possible (technically) to go into beta when airborne?

Is there a mechanical stop for the power levers at flight idle like on the Dash 8? On the Dash 8 you have to lift the gates on the power levers to go into disc (beta). 

 

Also, no prop sync for the Twotter?

 

The only aircraft I know of that's officially certified to use beta in flight is the Pilatus PC-6. That being said, the need to use beta in flight is a pretty niche situation. You wouldn't really want it 99% of the time.

 

There are gates to protect against accidentally dropping into beta like you mention. I don't think there are any aircraft that don't have some sort of a gate, however, there is nothing stopping you from moving through the gate into beta while in flight. The only aircraft that I'm aware of that physically locks you out of beta is the PC-12 which has some sort of lock out pin that engages with out weight on wheels. I know of one instance where a new B1900D pilot accidentally dropped into beta on short final thinking that he could just bring the power levers all the way back and not worry about it. In fact, it's a now legendary response where I work because the pilot was shocked that he was able to do it and our CI responded 'oh yeah, the only thing stopping you from doing that is the AFM!'.

 

The Dash 8 has much bigger props that turn a lot slower. Max RPM is 1050-1100 IIRC where as I think minimum flight RPM on PT-6 installations is going to be around 1400 so the governors are probably working a lot more on the Dash 8. On the Dash 8 the props pretty much turn at the RPM you select with the condition lever - feather/850/900/Max and you don't really need to worry about it. With planes like the Twin Otter and especially King Airs, you need to advance the power levers slowly to allow the governors to catch the props because even with the prop levers at max, the props won't be turning at max RPM at low power settings. When they reach max speed and the governors catch them you often see some fluctuations in RPM for a moment. You can always tell when a pilot is too harsh with power advancement because the fluctuations are quite audible as the governors try to get the prop RPM under control. A good practice is to advance the power levers slowly and then pause for a moment as the props reach max RPM to let the governors settle down and then advance the power levers to take off power.

[Jan R. Storelvmo 67]

8 hours ago, metzgergva said:

In reality there is a idle stop on the PL. If you look carefully at the videos, the handles can rotate a bit and that little wire on the left side is unlocking the stop to go into beta and then into reverse.

That stop and rotation is not modeled....plain speaking too complicated and not foreseen in MSFS.

 

Maybe it would be possible to add a sound when you hit the mechanical stop for idle, similar to the CRJ og Airbus. 

[Jan R. Storelvmo 67]

3 hours ago, IGrant said:

 

The only aircraft I know of that's officially certified to use beta in flight is the Pilatus PC-6. That being said, the need to use beta in flight is a pretty niche situation. You wouldn't really want it 99% of the time.

 

There are gates to protect against accidentally dropping into beta like you mention. I don't think there are any aircraft that don't have some sort of a gate, however, there is nothing stopping you from moving through the gate into beta while in flight. The only aircraft that I'm aware of that physically locks you out of beta is the PC-12 which has some sort of lock out pin that engages with out weight on wheels. I know of one instance where a new B1900D pilot accidentally dropped into beta on short final thinking that he could just bring the power levers all the way back and not worry about it. In fact, it's a now legendary response where I work because the pilot was shocked that he was able to do it and our CI responded 'oh yeah, the only thing stopping you from doing that is the AFM!'.

 

The Dash 8 has much bigger props that turn a lot slower. Max RPM is 1050-1100 IIRC where as I think minimum flight RPM on PT-6 installations is going to be around 1400 so the governors are probably working a lot more on the Dash 8. On the Dash 8 the props pretty much turn at the RPM you select with the condition lever - feather/850/900/Max and you don't really need to worry about it. With planes like the Twin Otter and especially King Airs, you need to advance the power levers slowly to allow the governors to catch the props because even with the prop levers at max, the props won't be turning at max RPM at low power settings. When they reach max speed and the governors catch them you often see some fluctuations in RPM for a moment. You can always tell when a pilot is too harsh with power advancement because the fluctuations are quite audible as the governors try to get the prop RPM under control. A good practice is to advance the power levers slowly and then pause for a moment as the props reach max RPM to let the governors settle down and then advance the power levers to take off power.

 

Looks like I've been spoiled with the Q400 where you practically could slam the power levers to take-off power without having to worry about it. Never saw any issues with the props struggling to maintain rpm UNLESS you had a malfunction (like often happened in the sim). Anyways, thank you for a very informative post  

 

Yeah, and by the way...another questions (yes, I'm sure you're starting to get tired of me now). 

 

What's your opinion on the beta simulation in the AS Twin Otter? Something seems a bit off in my opinion. I tested it with a friend of mine who bought it and beta seems very week during landing. On the Dash 8 it's really powerful. Full disc is plenty of stopping power, especially on the 100 series, but on the Q400 as well. I used to fly short field operations on the Dash 8-100 a few years ago. Lots of fun, but could get hairy during winter time. 

[IGrant 51]

48 minutes ago, Jan R. Storelvmo said:

 

Looks like I've been spoiled with the Q400 where you practically could slam the power levers to take-off power without having to worry about it. Never saw any issues with the props struggling to maintain rpm UNLESS you had a malfunction (like often happened in the sim). Anyways, thank you for a very informative post  

 

Yeah, and by the way...another questions (yes, I'm sure you're starting to get tired of me now). 

 

What's your opinion on the beta simulation in the AS Twin Otter? Something seems a bit off in my opinion. I tested it with a friend of mine who bought it and beta seems very week during landing. On the Dash 8 it's really powerful. Full disc is plenty of stopping power, especially on the 100 series, but on the Q400 as well. I used to fly short field operations on the Dash 8-100 a few years ago. Lots of fun, but could get hairy during winter time. 

 

Full reverse should be plenty of stopping power on just about any turboprop. MSFS on the whole doesn't do a great job of modeling turboprops so the Twin Otter is only as good as the MSFS platform allows for. I do find that full reverse is more than enough to get me stopped quickly, HOWEVER, I am not using a reverser axis at present. I'm just using the button at the bottom of the axis on my Bravo to 'decrease throttle'. As such, I can't modulate it or get a good feel for it. After a few moments I'm at full reverse and by then I'm slowed enough and I'm popping the lever out of reverse range.

 

One MSFS nuance I've noticed is that there doesn't seem to be enough prop drag. In my experience you can reduce power to zero torque quite easily with out much drama. At zero torque the props should effectively be big speed brakes and there should be some pretty rapid deceleration. That might have an affect on why it feels like beta is weak.

[C525B 13]

1 hour ago, IGrant said:

One MSFS nuance I've noticed is that there doesn't seem to be enough prop drag. In my experience you can reduce power to zero torque quite easily with out much drama. At zero torque the props should effectively be big speed brakes and there should be some pretty rapid deceleration. That might have an affect on why it feels like beta is weak.

 

Yep, as many know, that unfortunately has been carried over from FSX/P3D.  I remember when there was a flight dynamics mod for the old Carenado C208 in FSX where someone had the idea for a secret gauge in the panel that modulated invisible spoilers to simulate prop drag.  Definitely teaches you not to slam the power lever back, but the effect may have been a bit exaggerated.  You could make some really short landings though!

 

Prop drag specifically was one of the things they said would be improved by the new propeller dynamics in SU8.  Should be awesome...but...I also use X-plane, so I know the consternation that comes with big changes to the game's whole flight model, especially when the change breaks every payware aircraft you own and you have to wait for the devs to come around and update all their aircraft.

[Jan R. Storelvmo 67]

8 hours ago, C525B said:

Prop drag specifically was one of the things they said would be improved by the new propeller dynamics in SU8.  Should be awesome...but...I also use X-plane, so I know the consternation that comes with big changes to the game's whole flight model, especially when the change breaks every payware aircraft you own and you have to wait for the devs to come around and update all their aircraft.

 

Yes, along with several other things with the new prop simulation. I'm really excited. However, I think Seb at Asobo said the new prop simulation could easily be enabled and that the old legacy model would still be present which is great. Personally I think it's really awesome that Asobo is doing something with the core simulation (aerodynamics, physics etc). It's been untouched since those FSX days and really needs an overhaul. P3D never did anything to improve the simulation, but relied on 3rd parties. This keeps backward compatibility, but is really bad for new innovation.