Complex sentence: According to same resources Atak Helicopters front side is heavier than back side so helicopters nose is "looking down" to resolve this additional 137kg added to tail but additional weight caused helicopter get overweighted than it's requirement.
Split into simpler sentences: According to same resources Atak Helicopter's front side is heavier than back side, so helicopters nose is "looking down". To resolve this; additional 137kg added to tail but additional weight caused helicopter get overweighted than it's requirement.