SM UC-66 was a German Type UC II minelaying submarine or U-boat in the German Imperial Navy (German: Kaiserliche Marine) during World War I. The U-boat was ordered on 12 January 1916 and was launched on 15 July 1916. She was commissioned into the German Imperial Navy on 14 November 1916 as SM UC-66.[1] In five patrols UC-66 was credited with sinking 32 ships, either by torpedo or by mines laid. UC-66 was sunk by HM seaplane No. 8656, a Curtiss Model H-12,[2] off the Isles of Scilly on 27 May 1917. The wreck was found by divers in 2009. This is a notable early aircraft success against a U-boat.[3]
A Type UC II submarine, UC-66 had a displacement of 427t when at the surface and 508t while submerged. She had a length overall of 50.35m (165.19feet), a beam of 5.22m (17.13feet), and a draught of 3.64m (11.94feet). The submarine was powered by two six-cylinder four-stroke diesel engines each producing 300PS (a total of 600PS), two electric motors producing 620PS, and two propeller shafts. She had a dive time of 48 seconds and was capable of operating at a depth of .
The submarine had a maximum surface speed of and a submerged speed of . When submerged, she could operate for at ; when surfaced, she could travel at . UC-66 was fitted with six mine tubes, eighteen UC 200 mines, three torpedo tubes (one on the stern and two on the bow), seven torpedoes, and one 8.8sp=usNaNsp=us Uk L/30 deck gun. Her complement was twenty-six crew members.
| Date | Name | Nationality | Tonnage[4] | Fate[5] | |
|---|---|---|---|---|---|
| 11 February 1917 | Ada |  United Kingdom | 187 | Sunk | |
| 11 February 1917 | Vasilissa Olga |  Greece | 1,400 | Sunk | |
| 11 February 1917 | Woodfield | United Kingdom | 4,300 | Damaged | |
| 12 February 1917 | Afric | United Kingdom | 11,999 | Sunk | |
| 12 February 1917 | Lucent | United Kingdom | 1,409 | Sunk | |
| 15 February 1917 | Alma Jeanne |  France | 33 | Sunk | |
| 15 February 1917 | Argos | France | 26 | Sunk | |
| 15 February 1917 | Desire Louise | France | 31 | Sunk | |
| 17 February 1917 | Driebergen |  Netherlands | 1,884 | Sunk | |
| 17 February 1917 | Ootmarsum | Netherlands | 2,313 | Sunk | |
| 17 February 1917 | Trompenberg | Netherlands | 1,608 | Sunk | |
| 21 February 1917 | Energy | United Kingdom | 25 | Sunk | |
| 21 February 1917 | K.L.M. | United Kingdom | 28 | Sunk | |
| 21 February 1917 | Monarch | United Kingdom | 35 | Sunk | |
| 22 February 1917 | Ambon | Netherlands | 3,598 | Damaged | |
| 11 March 1917 | HMS Bayard | 220 | Damaged | ||
| 12 March 1917 | Einar Jarl |  Norway | 1,849 | Sunk | |
| 12 March 1917 | Forget-Me-Not | United Kingdom | 40 | Sunk | |
| 12 March 1917 | Glynymel | United Kingdom | 1,394 | Sunk | |
| 12 March 1917 | Memnon | United Kingdom | 3,203 | Sunk | |
| 12 March 1917 | Reindeer | United Kingdom | 52 | Sunk | |
| 13 March 1917 | Try | United Kingdom | 34 | Sunk | |
| 17 March 1917 | City of Memphis |  United States | 5,252 | Sunk | |
| 17 March 1917 | HMS Mignonette | 1,250 | Sunk | ||
| 18 March 1917 | HMS Alyssum | 1,250 | Sunk | ||
| 19 March 1917 | Armoricain | France | 261 | Sunk | |
| 20 March 1917 | HMHS Asturias | 12,002 | Damaged | ||
| 20 March 1917 | Hazelpark | United Kingdom | 1,964 | Sunk | |
| 21 March 1917 | Avance | United Kingdom | 57 | Sunk | |
| 22 March 1917 | Efeu | Norway | 569 | Sunk | |
| 17 April 1917 | Clan Sutherland | United Kingdom | 2,820 | Damaged | |
| 22 April 1917 | Arethusa | United Kingdom | 1,279 | Sunk | |
| 23 April 1917 | HMT Rose II | 213 | Sunk | ||
| 27 April 1917 | Quantock | United Kingdom | 4,470 | Damaged | |
| 1 May 1917 | Bagdale | United Kingdom | 3,045 | Sunk | |
| 1 May 1917 | John W. Pearn | United Kingdom | 76 | Sunk | |
| 1 May 1917 | La Manche | France | 335 | Sunk | |
| 25 May 1917 | Sjaelland | United Kingdom | 1,405 | Sunk |