Even today there are very few alternatives for the Sikorsky CH 53. Several air forces fly them and their maintenance is usually excellent. BTW, it is fine with me if you want to put trust in the Iranian Air Force, but underequipped and outperformed they are. Their air force is that of a beggar's nation, as is often said by military aviation experts. This crash came as no surprise, and more will follow.
Militants loyal to Islamic State claim suicide bombings in Nigerian capital (Reuters)
from the article: Iran jet fighter crashes near site of Bushehr nuclear reactor