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P-4M9 Oblique Wing Technology Demonstrator

The P-4M9, initially codenamed as the 9P004A series, is another asymmetric, variable geometry aeroplane developed independently by Kerbal Central Institute of Aerohydrodynamics, the largest aircraft manufacturer in South Kerbin. It is the first KCIA aeroplane that was designed to be asymmetrical from the beginning. The P-4M9 is equipped with a revolutionary Oblique Wing for the purpose of studying the feasibility of gaining different L/D curves along with different airspeed. Lift is exchanged for drag. The characteristics of a wing of a given area that generates lift and drag at a given speed and angle of attack are called the lift coefficient (CL = L/ one half air density x airspeed x wing area) and the drag coefficient (CD = D/ one half air density x airspeed x wing area), respectively. The ratio after dividing them is the lift-to-drag ratio. The point on the curves where the least drag coefficient is exchanged for the most lift coefficient is the maximum lift-to-drag ratio (L/D Max). Since the lift coefficient and drag coefficient are only related to the angle of attack when the geometric shape of the wing remains unchanged, therefore, when the airspeed increases or decreases, the coefficients will only change proportionally, and the lift-to-drag ratio curve remains unchanged. If the geometry of the wing can be changed to match different airspeeds, then at a specific airspeed, there can be a corresponding optimal lift-to-drag ratio, which can increase efficiency and improve performance. Customers interested in importing this ugly beauty may notice the mention of the "Oblique Wing". Yes, this structure is an integral piece spanning the top of the airframe. It is driven and connected to the airframe through a heavy-duty electric servo, rather than connected directly to the airframe like traditional-looking two independent wings.

Just like the legendary 9P002 HSPD (P-2SM3) series, the ending of the P-4 series can be defined as successful, however, its early development was fraught with difficulties. How to ensure that the center of pressure (lift) was maintained within an acceptable range at all times was the biggest issue that troubled its lovely designer BunnyFenger. Eventually, the 7th improved model was installed a [encrypted] at the end of the right horizontal stabilizer, and the [encrypted] on the right side of the [encrypted] was twisted to offset the [encrypted] at a small expense of non-SAS stability. After all, the P-4M7 could calmly complete the transition from a straight wing to an oblique one with SAS engaged. The 8th and 9th improved models comprehensively revised the control logic of the fly-by-wire system to smoothen the handling quality. There are no stacked engines or hiding control surfaces, there is no momentum wheel, and there is no trick. What you see is what it really is.

The practicality of the Oblique Wing in Kerbin's atmosphere still requires more test flights to determine. The P-4M9 may not be the perfect test platform, but it should provide valuable insights to Kerbin scientists.


WARNING: Folding the wing without engaging SAS voids the warranty.

NOTAM 1: Press 1 to toggle the engines; Press 4 to fold or unfold the wing with pre-arranged FBW settings.

NOTAM 2: For your safety, do not try to overwrite FBW settings without fully understanding them. *I mean, if the thing looks unusual, there must have been a reason ( ͡° ͜ʖ ͡°)

NOTAM 3: The P-4M series is not for supersonic flights. The oblique mode gains more maneuverability at low speeds. Due to the limitations of Kerbin's materials science, KCIA currently does not have an ideal solution to suppress the wobbling of the Oblique Wing at high airspeeds, which is pretty similar to what happened on Earth on their Forward-Swept-Wing aeroplanes. Therefore, it is recommended to switch the wing back to straight mode when exceeding 150 m/s.

Jan 2025 in Vancouver