CO2 and the surface

[Sandman_28054]

Patrol 27: Report to area Abuse and await further orders.

Date: August 10, 1944.

Departing from Fremantle.

No problem. Loadout: 16 type 34 fish; 8 (four fore, 4 aft; Cuties)

I'm in the area arounf area abuse, and I get the message:

Radar Contact, bearing 345 degrees, long range.

Again, no problem.

Set dive planes for 165 ft.

At 160' I order ahead slow.

I cruise like this for 90 minutes.

Order Periscope depth.

Radar incates target moving away "very fast".

Again no problem.

I order surface and speed to flank.

Problem: once on the surface, the CO2 guage is still rising.

Long story short, I ran out of air on the surface.

Hints anybody?