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? re: FSX turboprop engine inlet area


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Hi guys,

 

Seeking to understand a commonality I'm seeing with all native FSX turboprops and most others. In [turbineenginedata], the parameter 'inlet_area' is typically set to 1.0, which I'm understanding that to indicate the dimensional area of the ducted inlet in square feet.

 

Looking at other turbine-driven aircraft (jets, turbofans, etc.), this variable is indeed variable and goes up logically (a Learjet will have a ~4'^2 area whereas something big like a 747 will have a huge area).

 

Is a global 1'^2 inlet area right for turboprops?

Uich gwennen na'wanath ah na dhin,

an uich gwennen na ringyrn ambar hen.

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The inlet_area=1 for turboprops is fairly standard. I just compared the KingAir to a P3C Orion and the air inlets are small compared to fanjets like the 747 or 737. For a bigger turboprop you can adjust the size if you want, but most developers decided that 1 was good enough.

Still thinking about a new flightsim only computer!  ✈️

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The inlet_area=1 for turboprops is fairly standard. I just compared the KingAir to a P3C Orion and the air inlets are small compared to fanjets like the 747 or 737.

 

I suppose there's reasons for that. ;)

 

1. Invoking Bernoulli's Principle to force a massive amount of air through a small restriction*.

2. The debris gate at the inlet would be pointless if the inlet was larger.

3. The propeller.

 

For a bigger turboprop you can adjust the size if you want, but most developers decided that 1 was good enough.

 

Ahh, the dichotomy of being ultra-realistic vs. messing around with details that do not matter as much to the onboard physics engine. :)

 

Thanks for the quick reply. Was wondering if there was indeed a method to the madness, and I'm reminded yet again that turboprops are still turbine engines though they suck everything through a stir straw before the bang and blow stages. :)

 

* These are details that were most likely slept through in high school physics.

Uich gwennen na'wanath ah na dhin,

an uich gwennen na ringyrn ambar hen.

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Actually, the physics is fairly straightforward:https://en.wikipedia.org/wiki/Turboprop

 

In aircraft, like the 747, 737, using a turbofan engine, it needs to suck in mass quantities of air to be mixed with fuel and burned to become exhaust thrust.

 

In a turboprop, less air is needed to mix with the fuel to provide power to the propshaft and the thrust is provided by the prop.

Still thinking about a new flightsim only computer!  ✈️

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In aircraft, like the 747, 737, using a turbofan engine, it needs to suck in mass quantities of air to be mixed with fuel and burned to become exhaust thrust.

Actually, in a turbofan, the air that goes to combustion is only a small portion of the air that is needed, and the rest goes to the "fan" which acts as a kind of specialized propeller. This NASA article has a very helpful diagram and a good explanation of the operation of a turbofan: https://www.grc.nasa.gov/WWW/k-12/airplane/aturbf.html and you can even run various animations (airflow, temperature, pressure) to visualize it further. You can contrast it with this page on turbojet engines: https://www.grc.nasa.gov/WWW/k-12/airplane/aturbj.html and this page on turboprops: https://www.grc.nasa.gov/WWW/k-12/airplane/aturbp.html

 

They also have a page on the core gas turbine assembly: https://www.grc.nasa.gov/WWW/k-12/airplane/Animation/turbtyp/etcs.html

 

Finally, here is a link to NASA's Beginner's Guide To Aeronautics, which is aimed at Middle to high school students (and link for younger ones, as well): https://www.grc.nasa.gov/WWW/k-12/airplane/index.html

 

Good stuff there.

 

Larry N.

As Skylab would say:

Remember: Aviation is NOT an exact Science!

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Good stuff; thank you guys. :)

 

It does go to prove some of my observations of these turbofan engines -- especially on, for example, the P&W P1500's powering the Airbus A220 -- the hot section is tiny in comparison.

Uich gwennen na'wanath ah na dhin,

an uich gwennen na ringyrn ambar hen.

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