▁ 2 7 7 ▁single - cy l inder , ▁two - stroke ▁power plant . ▁With ▁this ▁engine ▁the ▁R X - 2 8 ▁had ▁an ▁empty ▁weight ▁of ▁. ▁ ▁The ▁avail ability ▁of ▁the ▁ ▁Rot ax ▁ 3 7 7 ▁engine ▁lead ▁to ▁a ▁higher - power ed ▁version ▁of ▁the ▁R X - 2 8 , ▁which ▁was ▁designated ▁the ▁R X - 3 5 . ▁This ▁Be aver ▁model ▁was ▁fitted ▁with ▁flo ats ▁and ▁continued ▁in ▁production ▁by ▁Spect rum ▁A ircraft ▁until ▁they ▁ceased ▁business ▁in ▁ 1 9 9 2 . ▁ ▁Building ▁on ▁the ▁success ▁of ▁the ▁single - se at ▁Be aver ▁models , ▁Spect rum ▁A ircraft ▁introduced ▁the ▁two - place ▁Be aver ▁R X ▁ 5 5 0 ▁in ▁ 1 9 8 6 ▁and ▁it ▁quickly ▁became ▁the ▁most ▁popular ▁ul tr al ight ▁tra iner ▁in ▁Canada . ▁The ▁combination ▁of ▁its ▁predict able ▁and ▁do cile ▁handling , ▁along ▁with ▁the ▁reliable ▁Rot ax ▁ 5 0 3 ▁ ▁engine , ▁ens ured ▁its ▁success . ▁ ▁Int ending ▁to ▁improve ▁on ▁the ▁R X ▁ 5 5 0 , ▁Spect rum ▁introduced ▁the ▁Be aver ▁R X ▁ 6 5 0 ▁in ▁ 1 9 9 1 , ▁int ending ▁to ▁place ▁it ▁in ▁the ▁Advanced ▁Ult ra - light ▁Aer op lane ▁category ▁( AU LA ) ▁in ▁Canada . ▁The ▁R X ▁ 6 5 0 ▁has ▁doors ▁that ▁fol d ▁up wards