Direct proof of use
The clearest public record of Su-22 combat use in the Syrian Civil War is the June 18, 2017 Tabqah incident. U.S. Central Command reported that pro-Syrian regime forces attacked the Syrian Democratic Forces-held town of Ja'Din south of Tabqah at about 4:30 p.m. Syria time, after which coalition aircraft conducted a show of force and coalition personnel used the Russia deconfliction line.
CENTCOM then reported that at 6:43 p.m. a Syrian regime SU-22 dropped bombs near SDF fighters south of Tabqah and was immediately shot down by a U.S. F/A-18E Super Hornet in collective self-defense of coalition partner forces. Reuters reporting carried by The Guardian and Al Jazeera repeated the coalition account while also noting the Syrian army's statement that the aircraft had been on a mission against Islamic State fighters near Raqqa.
Sources: CENTCOM Tabqah SU-22 Release, Guardian Reuters Syrian Aircraft Report, Al Jazeera Raqqa Province Report
Timeline
The documented sequence began with a pro-government ground attack on Ja'Din, continued with coalition attempts to halt or de-escalate the fighting, and culminated in the Su-22 bombing run and shootdown later the same afternoon.
Contemporary reporting placed the incident in Raqqa province during the anti-ISIS campaign around Raqqa and Tabqah. Air & Space Forces Magazine described the shootdown as part of a wider pattern of U.S. aircraft striking or downing pro-Syrian government aircraft and drones in that area during the same period.
Sources: CENTCOM Tabqah SU-22 Release, Al Jazeera Raqqa Province Report, Air and Space Forces Syrian Fighter Report
Operational role
In this documented incident, the Su-22 functioned as a Syrian government ground-attack aircraft. The evidence supports a fire-support or strike role against forces near the SDF-held line south of Tabqah, not a separate claim about every Syrian air-force Su-22 sortie during the war.
The reporting also separates the weapon's use from the later shootdown result: the conflict-use claim is that a Syrian regime Su-22 dropped bombs near SDF fighters, while the loss of the aircraft came from the U.S. coalition response after that bombing.
Sources: CENTCOM Tabqah SU-22 Release, Guardian Reuters Syrian Aircraft Report, Air and Space Forces Syrian Fighter Report