The first model Beaver was the RX - 28 including the category 's maximum 254 lb ( 115 kg ) empty weight .
The RX - 28 is a simple lightweight single - seat aircraft that was intended to comply with the US FAR 103 Ultralight Vehicles category .
The first model Beaver was the RX - 28 , a simple lightweight single - seat aircraft that was intended to comply with the US FAR 103 Ultralight Vehicles category , including the category 's maximum 254 lb ( 115 kg ) empty weight .