down bubble

From the bubble of air in the glass tube of the inclinometer, a gauge that indicates the submarine's vertical trim.

down bubble (not comparable)

1. (nautical) having a downward trim (of a submarine); usually follows the number of degrees
   • 1958, Run Silent, Run Deep, 00:01:25

     Two degrees down bubble. Hold her at 60.

   • 2000, Overdue and Presumed Lost, by Arthur MacMahan, page 181

     Dissatisfied with Sailfin's sluggish response, he turned the iron wheel a bit more until the bubble rode backward, indicating that the submarine's stern had lifted relative to the dipping bow. A glance at the calibrations etched into the brass plate behind the liquid-filled glass tubing told him that Sailfin's nose has dipped the required amount. "We have ten degrees down bubble, sir."

• up bubble
• lose the bubble
• angle of attack