Iran Air flight 215, a Fokker 100, suffered a failure of one of the hydraulic systems. Consequently, the main undercarriage could not be lowered. Even manual attempts to deploy the undercarriage using an emergency procedure proved fruitless due to a technical failure (seizing) on the landing gear door up-lock mechanisms. The flight crew then performed a main gear-up landing at Tehran-Mehrabad Airport, Iran. There were no injuries and there was no fire. Investigation results show that the aircraft had suffered hydraulical issues on prior flights. Causes: The aircraft involved accident due to the main gear up landing on the runway. The Aircraft Accident Investigation Board (AAIB) determines that the accident took place due to a combination of failures in hydraulic system and L/G manual extension. The investigation revealed that the contributive factors in human failures were as: – Not following procedures – Ineffective maintenance – Pilot nonstandard action to HYD #1 pump fault light based on QRH on previous flight IRA.214