Images of the Israeli F-35I ‘Adir’ stealth fighter have surfaced on the internet for the first time. The pictures show two Israeli F-35s flying on non-stealth mode over Lebanon.
The images were posted by a correspondent with the Lebanese satellite television station, Al-Manar TV and Al-Nour radio. The aircraft were initially believed to be Israeli F-15s.
According to defense analyst David Cenciotti, the images revealed that the aircraft were flying on non-stealth mode with their ‘radar reflectors’ on, carrying AIM-9X missile rails, making them intentionally visible to radars.
Cenciotti, the founder of The Aviationist, explains that stealth aircraft such as the F-22 Raptor or the F-35 Lightning II are equipped with Luneburg lenses that make the low observable (LO) aircraft visible to radars.
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He says these devices are installed whenever the aircraft don’t need to evade the radars and during ferry flights when the pilot communicates with the Air Traffic Control.
According to Cenciotti, this practice is usually followed during training or “operative missions that do not require stealthiness; or, more importantly, when the aircraft operate close to the enemy” radars or intelligence gathering sensors.
He further explains the stealthiness of aircraft and how it is vulnerable to detection from low-frequency radars due to the resonance.
Tactical fighter-sized stealth aircraft are built to defeat radar operating at specific frequencies — usually high-frequency bands — where the radar accuracy is higher, he maintains.
However, once the frequency wavelength exceeds a certain threshold and causes a resonant effect, LO aircraft become increasingly detectable. For instance, ATC radars, that operate at lower-frequency bands are theoretically able to detect a tactical fighter-sized stealth plane whose shape features parts that can cause resonance.
Radars that operate at bands below 300 MHz (lower UHF, VHF, and HF radars), such as the so-called Over The Horizon (OTH) radars, are believed to be particularly dangerous for stealth planes: although they are not much accurate, they can spot stealth planes and be used to guide fighters equipped with IRST towards the direction the LO planes might be, he maintains.
F-35s deployed abroad usually feature their typical four radar reflectors: to exaggerate their real RCS (Radar Cross Section) and negate the enemy’s ability to collect any detail about their LO “signature”.
This phenomenon was noticed during the USAF’s short mission to Estonia and then Bulgaria on August 30, 2017. Four US Marine Corps F-35B Lightning II joined two USAF B-1B Lancers for the Joint Strike Force’s first show of force against North Korea: the F-35Bs flew with the radar reflectors, a sign they didn’t want their actual radar signature to be exposed to any intelligence gathering sensor in the area, Cenciotti adds.