▁Field ▁for ▁testing ▁on ▁ 2 7 ▁July ▁ 1 9 2 7 , ▁but ▁it ▁quickly ▁became ▁apparent ▁that ▁the ▁Pack ard ▁engine ▁did ▁not ▁have ▁sufficient ▁power ▁to ▁compens ate ▁for ▁the ▁ 8 0 0   l bs ▁of ▁extra ▁weight , ▁the ▁craft ▁performing ▁more ▁poor ly ▁than ▁its ▁prede cess or , ▁and ▁the ▁project ▁was ▁quickly ▁abandoned . ▁ ▁Spec ifications ▁( X P - 4 ) ▁ ▁See ▁also ▁ ▁References ▁ ▁Notes ▁ ▁Bibli ography ▁▁ ▁Angel ucci , ▁En zo . ▁The ▁American ▁F ighter ▁from ▁ 1 9 1 7 ▁to ▁the ▁present . ▁New ▁York : ▁Or ion ▁Books , ▁ 1 9 8 7 . ▁. ▁▁ ▁Dor r , ▁Robert ▁F . ▁and ▁David ▁Donald . ▁F igh ters ▁of ▁the ▁United ▁States ▁Air ▁Force . ▁London : ▁Temple , ▁ 1 9 9 0 . ▁. ▁ ▁Jones , ▁Lloyd ▁S . ▁U . S . ▁F igh ters : ▁Army - A ir ▁Force ▁ 1 9 2 5 ▁to ▁ 1 9 8 0 s .. ▁Fall bro ok , ▁California : ▁A ero ▁Publish ers , ▁Inc ., ▁ 1 9 7 5 . ▁. ▁ ▁External ▁links ▁ ▁Joe ▁B aug her ▁page ▁on ▁the ▁XP - 4 ▁▁ ▁US AF ▁Museum ▁page , ▁with ▁pictures ▁ ▁Bo eing ▁P - 0 4 ▁P - 0 4 ▁Category : Single - eng ined ▁tra ctor ▁aircraft ▁Category : Bi plan es <0x0A> </s> ▁S lim