The Pros and Cons of S-Duct Intakes

In aircraft that are operated by jet engines, an intake, or an inlet, the engine is required to capture and slow down the air within the engine before it reaches the combustion chamber. Not all intake ducts are created equal, as there are multiple varieties available on the market, all of which offer different advantages and disadvantages. One of the popular choices for jet engines is an S-duct intake, that of which is shaped like the letter “S” and offers unique functions. While most commercial jets and other aircraft that require an even number of engines will choose a “straight-through” duct, the S-duct was invented as a solution for trijet designs. This blog will look specifically at the pros and cons of procuring an S-duct intake for your jet engine.

S-duct intake valves offer two major advantages over other design types. First, employing an S-duct intake allows for an aircraft design with shorter fins. The fins of an aircraft function primarily to improve stability during flight. They are shaped similar to small wings with their flight control designed surfaces. Due to the configuration of a system with an S-duct, the balance of weight along the aircraft’s longitudinal axis is less sensitive and therefore requires less additional stability.  Along the same principle, the S-duct also allows for a more convenient positioning of the aircraft’s engine. As the S-duct was designed for a trijet, or a jet plane with three engines, the S-duct allows for the third engine to be placed in a central position, with the other two engines on either side of the fuselage, creating a perfect balance. Additionally, the positioning of the S-duct is lower to the ground than that of alternative options, so it makes for easy access for workers and engineers.

While the S-duct was designed for the aforementioned reasons, it has been found to offer the added advantage of reduced drag. In fact, airplanes that use S-ducts may experience up to a 4% reduction in drag as compared to airplanes that use straight-through intake ducts. In turn, aircraft that use S-ducts are more efficient in that they can travel longer distances while consuming less fuel.

Although the efficiency and structural design of S-ducts makes them wise choices for many planes, not all aircraft operators should opt for this choice of intake valve because there are a few disadvantages to consider. First, S-ducts have a more complex design than their straight-through counterparts, making them more costly to both produce and install. Furthermore, as they are designed for applications that involve an odd number of engines, they are uncommon on many commercial jets. As there are multiple types of intake valves available for procurement, it is important for any potential buyer to understand the benefits and drawbacks of whichever design they aim to procure. For many situations, the S-duct offers exactly what your aircraft needs, so begin the procurement process today with ASAP Aerospace.

Owned and operated by ASAP Semiconductor, ASAP Aerospace is a leading online distributor of aircraft parts for various applications. As an AS9120B, ISO 9001:2015, and FAA AC 00-56B accredited enterprise with a NO CHINA SOURCING pledge, we guarantee that our ever-expanding inventory is of the highest-caliber for our loyal customers. If you are in the market for reliable engine parts, make us your purchasing partner today when you submit a Request for Quote form as found on our website. As we are equipped to offer expedited shipping on both domestic and international orders alike, we ask that you include all relevant details regarding your purchase, such as shipping deadlines and target prices, to ensure that your Instant RFQ is met with a custom quote for your comparisons. To learn more, contact us at any time via phone or email; we are available to help 24/7x365.


December 5, 2022

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