Stealth aircraft

Aircraft designed to reduce detection by radar, infrared, acoustic, or visual sensors. Their design combines low-observable shaping, materials, and operational tactics.

Radar cross-section: A measure of how strongly an object reflects radar energy toward a receiver. Shaping and surface treatments aim to reduce the radar echo used to detect aircraft.
Lockheed F-117 Nighthawk: A U.S. attack aircraft designed around low radar observability and used in combat from 1989. Its faceted surfaces made it an early operational example of radar-stealth design.
Passive radar: A radar technique that detects targets using transmissions from other sources rather than its own transmitter. It can complicate stealth tactics that focus on reducing returns to conventional active radar.
Aircraft shaping: The arrangement of an aircraft's surfaces and edges to achieve aerodynamic or other design goals. Stealth requirements make surface alignment and edge geometry central airframe constraints.
Pyotr Ufimtsev: A Soviet physicist whose work on diffraction helped explain how radar waves scatter from shaped surfaces. His mathematical analysis informed later aircraft radar-signature calculations.
Radar-absorbent material: Material engineered to absorb portions of incident radar energy rather than reflect it. Such coatings and structures can complement the aircraft's radar-deflecting shape.
Northrop Grumman B-2 Spirit: A U.S. long-range flying-wing stealth bomber introduced into service in the 1990s. Its flying-wing planform combines long-range bombing with reduced radar observability.
Bistatic radar: A radar arrangement with its transmitter and receiver at separate locations. Separated viewing angles can expose reflections that a stealth shape directs away from a monostatic radar.
Fly-by-wire: An aircraft control system that transmits pilot commands electronically to flight-control actuators. Some stealth airframes use aerodynamically unstable designs that require computerized flight control.
Denys Overholser: An American engineer associated with applying Ufimtsev's diffraction methods to stealth-aircraft design. His work helped translate scattering theory into practical low-observable aircraft concepts.

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