This is used when a person must do something without much planning or training.  The contraction combines the words ‘I’ and ‘will’.

我得憑經驗［或感覺］瞎碰。

由於事前沒有計畫，或缺少訓練，只能臨時憑感覺碰運氣，憑舊有的經驗去做，這就是片語 fly by the seat of my pants 的含義。