Can VHF Radar and Its Lock-After-Fire Capability Defeat Stealth Aircraft?

While VHF radar (Very High Frequency radar) can provide some advantages in detecting stealth aircraft, its effectiveness varies based on the specific radar configurations and the stealth technologies employed by the aircraft. This article explores the capabilities and limitations of VHF radar in detecting and engaging low-observable aircraft, particularly focusing on lock-after-fire (LOAF) missiles.

Understanding Radar Wavelengths and Angular Resolution

The effectiveness of radar in detecting stealth aircraft is often attributed to the radar's wavelength. Generally, the longer the wavelength, the more effective the radar becomes in detecting low-observable (LO) aircraft. However, longer wavelengths come with trade-offs, such as lower angular resolution for a given size of the radar platform. This makes it challenging to achieve both detection and accurate tracking for a given radar size.

VHF Radar for Early Warning and Missile Engagement

VHF radars, designed for early warning, tend to have broader beams and lower angular resolution, but they can detect aircraft at much farther ranges. These radars, such as the Royal Navy's Type 42 destroyer radars, can effectively identify the presence of low-observable aircraft but struggle to generate precise target tracks necessary for weapons engagement. The Type 42's 965 and 1022 radars, though capable of detecting aircraft at over two hundred miles, were not sufficient for detailed tracking and were only used for early warning and cueing missile systems.

High-Frequency Radars for Precision Tracking

For precision tracking, higher-frequency radars, such as the 992 and 996 radars, were introduced. These radars can scan the sky every two seconds rather than every eight seconds, generating more precise target tracks. However, precision target tracks are crucial for weapon systems like the Sea Dart, which requires both good angular resolution and the ability to lock onto and engage targets accurately. The Sea Dart was guided by the I-band pencil-beam tracking radar, Radar 909, which could lock onto a target and illuminate it with continuous-wave J-band energy, enabling the missile to home in on the target.

Challenges in Detecting and Engaging Stealth Aircraft

While VHF radars can detect stealth aircraft, the issue arises when attempting to turn this detection into a usable target track for weapons systems. Passive radar detection, such as that provided by VHF radars, is effective in identifying the presence of low-observable aircraft but may only provide rough location data. This information is insufficient for LOAF missiles, which require precise target tracks to function effectively.

Limitations of Active Radar Sensors

Active radar seekers, designed to operate in the seeker band, are highly sensitive to low radar cross-section (RCS) targets. However, this very sensitivity limits their detection range. They are effective in detecting stealth aircraft but have a shorter range compared to high-fidelity radars. Additionally, IR sensors, which are often used alongside radar, also have limited ranges and can be easily confused or jammed.

Lock-After-Fire (LOAF) Missile Engagement

LOAF missiles are designed to be lofted or fired after the target has been detected by a radar, such as a VHF radar, and then homed onto the target using a semi-active seeker. The challenge with LOAF missiles is that they are much easier to confuse or jam compared to missiles that are initially guided to the target. The seeker of a LOAF missile is looking for a general target, making it more susceptible to decoys and jamming. In contrast, a missile that is engaged with a more precise track by a higher-frequency radar is less vulnerable to such interference.

Conclusion

While VHF radar can detect stealth aircraft and provide early warning, its limitations in generating precise tracks make it challenging to engage such aircraft effectively using lock-after-launch missiles. The combination of high-frequency radars for precise tracking and VHF radars for early warning and general detection provides a more robust approach to countering stealth aircraft. Future developments in radar technology and missile systems will continue to address these challenges to enhance overall effectiveness in detecting and engaging low-observable targets.