Among the specifications of Iran-140 A/C, we can refer to the fact that the APU of this Aircraft is considered as a part of A/C empty weight, in spite of all competetive prop-jets in which the APU is optional and considered as a part of load.
The APU not only removes the dependence of A/C to aerodrome ground equipment, but also it can be operated in cruise altitude when one of the engines is inoperative. In this case, then APU operates as the other engine and helps the aircraft to safely fly.