To demonstrate the non-inferiority of QVA149 110/50 µg o.d. to fluticasone/salmeterol 500/50 µg b.i.d. in terms of trough Forced Expiratory Volume in one second (FEV1) (mean of 23 hours 15 min and 23 hours 45 min post QVA149 dose) following 26 weeks of treatment in patients with moderate to severe COPD.