Stealth aircraft typically fly subsonic in contested areas to maximize their stealth capabilities and minimize the risk of detection. This operational choice stems from the following factors:
1. Radar Signature and Aerodynamic Design
• Stealth aircraft are designed with smooth, angular surfaces to scatter radar waves, but supersonic flight generates shock waves that increase their radar cross-section (RCS).
• At supersonic speeds, the airflow over certain parts of the aircraft (e.g., leading edges and engine inlets) can create regions of higher radar reflectivity, potentially compromising stealth.
2. Infrared (IR) Signature Management
• Supersonic flight generates significantly more heat due to air compression around the aircraft and increased engine output. This heightened heat signature makes the aircraft more vulnerable to infrared-based detection systems and heat-seeking missiles.
• Subsonic speeds reduce engine heat and aerodynamic friction, minimizing the infrared signature.
3. Acoustic Signature
• Breaking the sound barrier creates a sonic boom, which can be detected by ground-based acoustic sensors or enemy forces. Subsonic flight avoids this, helping maintain low observability.
4. Fuel Efficiency and Mission Range
• Supersonic flight consumes far more fuel than subsonic flight. In contested areas, fuel efficiency is critical to extending mission range and maintaining loiter time for reconnaissance or strike missions.
• Subsonic speeds allow stealth aircraft to stay in the air longer, providing greater operational flexibility.
5. Avoiding High-Speed Predictability
• At supersonic speeds, the aircraft’s trajectory becomes more predictable due to momentum and limited maneuverability. This can make it easier for advanced missile systems or radar networks to calculate intercept points.
• Subsonic flight allows for greater flexibility in route planning and sudden maneuvers, making detection and targeting more challenging.
6. Mission Objectives and Threat Avoidance
• In contested airspace, stealth aircraft often prioritize evasion over speed. Their design focuses on penetrating defenses undetected rather than relying on speed to outrun threats.
• Supersonic flight may be reserved for specific scenarios (e.g., escaping a high-threat zone or intercepting an enemy) but is generally avoided when stealth is paramount.
Examples in Practice
• The B-2 Spirit and F-117 Nighthawk, both stealth platforms, operate exclusively at subsonic speeds, as their designs prioritize low observability.
• While the F-22 Raptor and F-35 Lightning II can fly supersonically, they typically operate subsonically in contested environments to preserve stealth and reduce their detectability.
Conclusion
Flying subsonic in contested areas aligns with the core principle of stealth: avoiding detection. While supersonic speeds can provide tactical advantages in specific situations, the increased radar, infrared, and acoustic signatures, coupled with reduced fuel efficiency and maneuverability, make subsonic flight the preferred choice for stealth operations in high-threat zones.
