This unusual looking Mi-17PP was stored at Krumovo in Bulgaria. The PP is a radar jamming version and would accompany plain trooping helos and attempt to jam the radar of SPAAGs like the Gepard. Those are very effective against helos. The serial is 431,

and although faded can just be read on the cowling ahead of the left engine exhaust. This specialist jammer is 'HIP-H'.

Done