The Fatal Torpedo Hit
The only hope of destroying the Bismarck was to slow her down sufficiently for the battleships to be able to catch up with her. This task obviously fell to the aircraft carrier Ark Royal, as only her torpedo planes had the range and weapons to do the job. By the time this plan of action had been decided upon, Force H had already steamed some distance further north before Somerville turned his ships on a course parallel to that of the Bismarck at about noon. Force H was still within range, but it would take longer for the aircraft of the Ark Royal to reach their target.

Preparations were immediately undertaken to launch an air strike against the Bismarck as soon as possible that afternoon. The Swordfish aboard the Ark Royal were fuelled, and 18in torpedoes were latched to their underbellies as their crews were being briefed. At 1450 on 26 May, 15 Swordfish aircraft took off from the Ark Royal and headed for the last known position of the Bismarck. Their pilots had just been advised that their target was alone in the area, but in fact the light cruiser Sheffield had been ordered to move up astern of the Bismarck and keep her under observation. The signal concerning the Sheffield had not been deciphered on the Ark Royal in time to alert the Swordfish pilots.

Flight of Swordfish torpedo planes attack HMS Sheffield by mistake.

The Swordfish pilots obtained radar contact with what they thought was Bismarck (Sheffield) at 1540 and pressed their attack against the ship shortly after. Fortunately, the Sheffield was not hit by any of the 11 torpedoes that were launched against her. All of the Swordfish aircraft returned safely to Ark Royal at about 1700.

At 1740, the Sheffield obtained contact with the Bismarck and started to shadow her.

The fuel shortage caused by the Prince of Wales' fateful hit required the Bismarck to steam at only 20 knots so that she would have sufficient fuel to reach St Nazaire. Topping off her tanks in Norway or from a tanker at sea would certainly have eased the situation, but that had not been done. Had the Bismarck been able to steam at 28 knots, she would have already been under the protective cover of the Luftwaffe by that afternoon.

Second air strike from HMS Ark Royal is successful in disabling the Bismarck.

Aboard the Ark Royal they knew they only had one more attempt in trying to stop or at least slow down Bismarck as the German battleship would reach the French coast the next day. At 1915, another fifteen Swordfish took off from the Ark Royal.

Diagram of the attack by the Swordfish on Bismarck.

The Swordfish attack took place at 2047. Bismarck was hit by a torpedo amidship which caused no damage. But then she was hit by a torpedo in the starboard rudder area. According to the rudder indicator, the rudder was jammed at 12º or 15º to port (the sources disagree here). Despite that the German anti-aircraft fire was very intense none of the Swordfish aircraft was shot down.

The Fatal Torpedo Hit
The different opinions
The different sources about the history of the Bismarck are disagree about what actually happened during the last air attack against the Bismarck. The outcome of my research seems to state the fact that:
1. Accounts differ as to the number of torpedo hits (two or three) and the order in which they occured.
2. All the sources agree that Bismarck turned to port when the fatal torpedo came towards her.
3. The Bismarck's rudder indicator indicated that the rudder was jammed either 12° or 15° to port. They disagree about that too.

Between 2130-2155, Bismarck fired six salvoes from 14,000 meter (15,000 yards) against the Sheffield which had just come insight. The Sheffield was not hit but some splinters disabled her radar, killed three men and injured six more.

At 2140, Admiral Lütjens sent the following message to Group West: "Ship unable to maneuver. We will fight to the last shell. Long live the Führer".