(S (S (SBAR (S (SBAR (S (PP-SBJ (BASENP (NN 飛行機)) (IN が)) (VP (PP-OBJ (BASENP (NN 機首)) (IN を)) (VBV 下げ))) (INTE て)) (S-NSBJ (S-NSBJ (PP (NP (PP (BASENP (NN 山)) (IN の)) (NN 中)) (IN に)) (VP (VP (NN 墜落) (VBV し)) (VP (MD た)))))) (NN とき)) (COMMA 、) (S (PP-SBJ (NP (S-REL (BASENP-SBJ (NN 経験)) (ADJP (NN 豊富) (MDO な))) (BASENP (NN ３１) (NN 歳))) (IN は)) (VP (NP (PP (BASENP (NN 夜間)) (IN の)) (BASENP (NN 任務) (NN 中))) (VP (MDV だっ) (VP (MD た)))))) (PERIOD 。))
飛行機 が 機首 を 下げ て 山 の 中 に 墜落 し た とき 、 経験 豊富 な 31 歳 は 夜間 の 任務 中 だっ た 。
The experienced 31-year-old was on a night mission when his aircraft crashed nose-down among mountains .