DCS: BO-105 3D/FM Announcement and Discussions

[The_Fragger]

BO-105 Development Report

During the last few months, the Miltech-5 team has been hard at work on developing a completely new set of functionalities for the BO-105 helicopter. Simulating helicopters is a long and complex endeavor, and throughout our journey the team has learned valuable lessons along the way. Development cycles often require taking a step back, and realistically assessing the needs and wants of the community. Your ever-increasing standards and expectations do not fall of deaf ears, and we have taken draconian measures to meet them. In concrete terms, this means we had to go back to the proverbial drawing board, take an honest look at what the team could realistically achieve with existing tech… and we concluded that we had to change the way we do things.

We needed to set a new benchmark in terms of helicopter flight dynamics fidelity and more accurately simulate various aircraft systems, devices, and components. “MEDUSA” is the name of our own internal software framework, specifically built from scratch to better simulate realistic aircraft physics, including behavior according to their mass and properties.

The traditional way to simulate a specific user action (for example, moving a switch in the cockpit) is to cause a chain of actions, which then are checked for all possible situations. Here is an example on how things were typically computed prior to using MEDUSA:

• Is electrical power available?

• Is the relevant circuit breaker pressed in?

• Is the device useable/undamaged?

• If all previous conditions are met, results of all connected devices are calculated.

Hardware Devices

The MEDUSA software considers individual devices/components as dynamic objects, which are in turn affected by environment arguments, and react accordingly. Any external change of arguments does not require a specific software module anymore. The reaction is an automatically computed result based on the combination of all device results. Electrical, fuel, hydro-mechanical and oil lubrication systems of the simulated helicopter are as close to an integrated 1:1 representation of the real helicopter as can be.

One of the most critical physics models to get right is the rotor assembly. Each rotor blade is divided into 10 sectors. Each sector computes:

• Sector speed

• Sector lift

• Sector drag

• Sector momentum

• Sector centripetal forces
   

 

All sector forces are added, which in turn affect the entire helicopter. The three images below show calculations in different situations. The green bars show the lift development, the red bars the induced drag. The first image has the collective in downmost position.

The second image shows the collective raised 7 degrees upwards.
The third image shows the collective raised in the uppermost position.


 

This approach ensures that special situations like autorotation or blade stall are dynamically computed and affect the whole flight model.

Special care was also taken to accurately model rotor blade stall, which can lead you into dangerous situations. If a helicopter is in a rapid descent (vertical velocity greater than 800 ft/min) with almost no forward movement, the inner blade sectors 1, 2 and 3 have a resulting angle of attack (AoA) greater than 18 degrees. This is partly caused by blade twist (8 degrees), collective position and the direction of streaming air caused by the abrupt descent. The physical position of the inner sectors affect the lift vector, which in this case is reduced to almost nothing) and the pilot has almost no possibility to recover. Why? Well, a natural reflex to decrease the decent rate would be to raise the collective further up… but the side effect of doing so further increases the blade angle, which is already stalling. The image below represents the stream of air in a blade stall situation.



The beauty behind this concept is that the stalling blade is recognized as physical result by the rotor device software.

In other news, the electrical and fuel supply systems are done. The turboshaft simulation still needs a bit more tuning since the modelling of the compressor and the combustion chamber are not quite where they need to be yet. The next step will be the integration of the gearbox and the rotor systems. In parallel, another team is working on integrating the module with the DCS SDK (Software Development Kit) interface.

The Miltech-5 team has already shown the advanced stages of our photorealistic replica of the BO-105’s cockpit and helicopter body, but we thought it was important to share what goes on under the hood when it comes to systems, flight model and component interactions. The BO-105 is an exciting challenge, and we are very excited to share further upcoming features as we approach the finish line. We will keep you informed continuously about the development progress.

 

Edited February 2, 2024 by The_Fragger

[Raven (Elysian Angel)]

Nice! If it works as advertised, MEDUSA sounds like the future of (helicopter) flight simulation  

[cloose]

A little hard to read but great info. Thanks The_Fragger and Good luck.

[rato65]

Thanks for the update, and for the details about internatl decisions you made to allow developing a realistic simulation. I know from different projects outside DCS that simulation development takes incredible much of time, and of course long-breath-motivation. Considering the very high level of functional realism given in DCS your way is understandable and appreciated with the Bo-105 project. However, I hope it will succeed and it will become available at some stage, sometimes it might be worth a consideration to provide a non-final technology for feedback from the community to see if everything is on the right path. But this is not easy, I understand.

Anyway, great to learn this is not dead, and I am very much looking forwrard to the future of the Bo-105 - as are many others I suppose. Good luck!

Edited February 3, 2024 by rato65

[unknown]

Great news, i can't wait to fly this beauty!

[Guille H. Mono]

Why I keep hearing that this module "will come in three versions, of which two are flyable and one is only AI"?

It is a good way to create expectations and then ruining them in the same sentence.

 

[zerO_crash]

Fantastic stuff, especially since helicopter dynamics are among the most complex to recreate in the digital environment. Such a methodical, yet accurate approach, is definitely the way to go.

 

It's also good to hear that you'll be creating more helicopters

[hermes7226]

How big is the team working on the module? 

[The_Fragger]

On 2/13/2024 at 6:29 AM, hermes7226 said:

How big is the team working on the module? 

3 Guys.

[MAXsenna]

19 hours ago, The_Fragger said:

3 Guys.

No girls and a pizza place? 9

[Raven (Elysian Angel)]

On 1/26/2025 at 4:57 AM, MAXsenna said:

No girls and a pizza place? 9

Can't have any distractions if you only have a 3 man team

[MAXsenna]

Can't have any distractions if you only have a 3 man team

That's true!

Sent from my SM-A536B using Tapatalk

[The_Fragger]

BO-105 - DE-ICING

The Critical Role of Air Intake Anti-Icing Systems in Turbine Engine Performance

The air intake system is a fundamental component of any turbine engine, directly influencing engine performance, efficiency, and safety. Under specific meteorological conditions, ice accretion within the air intake can significantly restrict airflow, posing a severe risk to engine operation. A pertinent example is the Allison 250 turboshaft engine, which features an air intake diameter of merely 10 cm—small enough to be obstructed by something as trivial as a compacted snowball. Ice accumulation reduces the mass flow rate of air to the compressor, potentially leading to compressor stall or, in extreme cases, complete engine flameout.

Mechanisms of Ice Formation in Air Intakes

Contrary to common assumptions, ice can form within the air intake even when ambient temperatures are above freezing. This phenomenon is primarily driven by the thermodynamic effects of pressure and temperature changes within the intake system. The air intake does more than channel ambient air toward the compressor; the compressor actively induces a pressure drop in the intake, resulting in adiabatic cooling.

For instance, if the ambient atmospheric pressure is standard (1013 hPa), the induced pressure within the air intake may decrease to approximately 960 hPa due to compressor suction. This pressure drop leads to a corresponding temperature decrease of around 3°C. Consequently, ambient air at 2°C can cool to -1°C within the intake duct. Additionally, the rapid reduction in pressure causes moisture in the incoming air to condense into microdroplets. Upon contact with the sub-zero inner surfaces of the air intake, these droplets freeze, leading to ice accretion. This process mirrors the sublimation of water vapor into frost on cold surfaces, a phenomenon observable on frosted windows during winter.

Design and Functionality of Air Intake Anti-Icing Systems

To mitigate the risk of ice formation, turbine engines are equipped with sophisticated anti-icing systems that maintain the air intake's internal surfaces above freezing temperatures. These systems typically utilize bleed air extracted from intermediate stages of the compressor.

After ambient air enters the intake, it undergoes compression to pressures reaching approximately 6500 hPa, with corresponding temperature increases to around 250°C by the fifth stage of the compressor. At this stage, a pilot-controlled bleed valve allows a portion of this high-temperature, high-pressure air to be diverted and routed to the air intake’s outer skin. The hot bleed air heats the intake structure, thereby preventing moisture from condensing and freezing on the internal surfaces.

Operational Implications and Performance Trade-Offs

While bleed air anti-icing systems are effective in preventing ice formation, their use introduces certain operational trade-offs. Diverting bleed air from the compressor reduces the mass airflow available to the combustion chamber, impacting both the combustion efficiency and overall engine performance. This reduction necessitates an increase in fuel flow to maintain the required turbine inlet temperatures (TIT), which, in turn, affects the engine's specific fuel consumption (SFC).

Moreover, during engine start-up—particularly under cold-soak conditions—activating the anti-icing system can prolong the time required to achieve the kerosene flash point of approximately 48°C in the combustion chamber. This extended start-up cycle increases the electrical load on the aircraft’s battery system, potentially limiting the number of available start attempts in battery-dependent start configurations.

Additionally, bleed air is frequently utilized for environmental control systems (ECS), including cabin pressurization and heating. The concurrent demand for bleed air in both anti-icing and ECS functions can further diminish available engine power, particularly in high-demand flight phases such as takeoff and climb.

Conclusion

The air intake anti-icing system should be engaged whenever the outside air temperature drops below +2°C, as these conditions are conducive to ice formation. Such temperatures are commonly encountered both on the ground during the autumn and winter seasons and at altitude when traversing the freezing level during ascent. However, it is imperative for flight crews to consider the operational penalties associated with anti-icing system activation, including increased fuel consumption, reduced engine performance, and potential impacts on aircraft range, service ceiling, and payload capacity.

Efficient management of the anti-icing system, in accordance with the aircraft’s operating manual and prevailing atmospheric conditions, is essential to ensuring both flight safety and optimal engine performance.

Simulation Accuracy with MEDUSA

The programming with MEDUSA will simulate these processes with a high degree of realism, accurately reflecting real-world engine behavior and the operational dynamics of the anti-icing system.

Edited February 1 by The_Fragger
Correction

[Whirley]

Love the technical updates, thanks!