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Turboprop Beta Range

Messages
43
Country
unitedkingdom
Hi All,

Comparing different turboprops I have, for example, the 1900d has noticeable beta range effects, it will decelerate even at low speeds quickly at idle without braking action.
However, all other types don't have any deceleration with idle.

Was wondering if any Table covers this effect, or if the best way is to manually calculate and then apply deceleration to the velocity variables with SimConnect?

Thanks
 

Roy Holmes

Resource contributor
Messages
1,784
Country
us-virginia
The Low Speed Idle setting I described above will give you some deceleration, but reverse thrust works very well. I was getting 1600 lbs reverse propthrust per engine in the C-2. That would stop it and it would back up some.
Roy
 

taguilo

Resource contributor
Messages
1,585
Country
argentina
There are two parameters that influence beta behavior in a turboprop:

minimum_on_ground_beta
minimum_reverse_beta


Let's say a basic definition of beta range, which is the section in where prop pitch is controlled by power lever instead of prop/condition lever. It starts just below ground low pitch stop up to max reverse.
This range is variable between different engine brands/models and/or propellers. Low pitch stops can go from high values, like 21º in the Turbine Otter, to very low, like 2º in the KA 350.
Logically, deceleration factor increases as long as prop pitch decreases, and further into negative angles (which usually reach -15º).
In the simulator default turboprop model things are not quite correct. Values above 8-10 degrees of pitch won't produce enough drag for the positive range, so depending on the prop being modeled, I won't go above 8 degrees (minimum_on_ground_beta=8) . That value is fine for nice drag effect until reverse action in negative values. Low values, like 2 degrees (minimum_on_ground_beta=2), are useful for aircraft with high taxi speeds in idle, like the KA350.
For reverse limit the standard -15 degrees (minimum_reverse_beta= -15) is fine for most situations.

Another issue in the sim is related to sound. In real aircraft. typical roaring of prop blades in beta can be heard in the entire beta range, but in the sim's sound system there is only a reverse flag available, which applies to negative pitch values. So if positive pitch beta sound is wanted, it must be done outside of the sound system.

Tom
 
Messages
19
Country
netherlands
There are two parameters that influence beta behavior in a turboprop:

minimum_on_ground_beta
minimum_reverse_beta


Let's say a basic definition of beta range, which is the section in where prop pitch is controlled by power lever instead of prop/condition lever. It starts just below ground low pitch stop up to max reverse.
This range is variable between different engine brands/models and/or propellers. Low pitch stops can go from high values, like 21º in the Turbine Otter, to very low, like 2º in the KA 350.
Logically, deceleration factor increases as long as prop pitch decreases, and further into negative angles (which usually reach -15º).
In the simulator default turboprop model things are not quite correct. Values above 8-10 degrees of pitch won't produce enough drag for the positive range, so depending on the prop being modeled, I won't go above 8 degrees (minimum_on_ground_beta=8) . That value is fine for nice drag effect until reverse action in negative values. Low values, like 2 degrees (minimum_on_ground_beta=2), are useful for aircraft with high taxi speeds in idle, like the KA350.
For reverse limit the standard -15 degrees (minimum_reverse_beta= -15) is fine for most situations.

Another issue in the sim is related to sound. In real aircraft. typical roaring of prop blades in beta can be heard in the entire beta range, but in the sim's sound system there is only a reverse flag available, which applies to negative pitch values. So if positive pitch beta sound is wanted, it must be done outside of the sound system.

Tom
It is been a while, but can you confirm that a low value minimum_on_ground_beta makes the airplane taxi slower and reduces speed faster (prop drag higher)? Thx
 
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