It is astonishing that an austere modification to an early 1970s helicopter by a tiny team resulted in a world speed record that stands to this day, despite big budget development programmes by the USA’s leading rotorcraft manufacturers

The stealthy RAH-66 Comanche provided an object lesson for Boeing and Sikorsky in the need to avoid excessive requirements, requirement creep, developmental delays and poor management

By the time the X2 made its final flight in July 2011, Sikorsky had built the mock-up of a Light Tactical Helicopter derivative of the X2. It differed from the later S-97 Raider prototypes in having a tricycle landing gear, stub wings for armament, chevron-type tailfins and a more streamlined, slender profile, while the engine intakes and nacelle were more prominent

The first Sikorsky S-97 Raider prototype (N971SK) was written off after a hard landing while hovering at the William P Gwinn Airport, Jupiter, Florida, on August 2, 2017. The aircraft lifted into a low hover and immediately experienced extreme roll oscillations that led to the coaxial rotors intermeshing, taking 1.2m off each blade and "creating a cloud of blade fragments and grey dust"

Взлетает вертолет-демонстратор X-2
The tiny, lightweight X2 technology demonstrator proved the basic configuration used by both Raider and Defiant, and indeed by the derived Raider X and Defiant X. Some believe that it may not be further scalable to address the larger FVL categories

The Sikorsky X2 demonstrator was actually built by Schweizer and had a Schweizer model designation (SHM-41A). The aircraft initially wore the US civil registration N41AX

The S-97 Raider demonstrator will be 20% smaller than its FARA successor, the Raider X, to accommodate the T901-900 turboshaft engine.
The X2 lineage is immediately obvious in the larger S-97 Raider. The first prototype flew on May 22, 2015 and the second followed on June 19, 2018 replacing the first aircraft after its accident

The Defiant X will benefit from research carried out by the Sikorsky Autonomy Research Aircraft (SARA), a modified Sikorsky S-76B flying laboratory used to prove Aircrew Labor In-Cockpit Automation System (ALIAS) technology

The XH-59A Advancing Blade Concept (ABC) rotor system aircraft taxiing at the US Marine Corps Development and Education Command Air Facility. The aircraft had two 3,000lb st Pratt & Whitney J60-P-3A turbojet engines to offload the main rotor

The Defiant X looks sleek, streamlined, stealthy and futuristic, especially when compared with current battlefield rotorcraft, which often look little different from their predecessors.
The Defiant X’s engine shrouds and reshaped trailing edges are noticeably different to the SB-1