Wulstan Tempest succeeded in setting fire to the airship, which came down near Potters Bar. All 19 crew died, many jumping from the burning airship. For the next raid, on 27–28 November, the Zeppelins avoided London for targets in the Midlands. Again the defending aircraft were successful: L 34 was shot down over the mouth of the Tees and L 21 was attacked by two aircraft and crashed into the sea off Lowestoft. There were no further raids in 1916 although the Navy lost three more craft, all on 28 December: SL 12 was destroyed at Ahlhorn by strong winds after sustaining damage in a poor landing, and at Tondern L 24 crashed into the shed while landing: the resulting fire destroyed both L 24 and the adjacent L 17. 1917 To counter the increasingly effective defences new Zeppelins were introduced which had an increased operating altitude of and a ceiling of . The first of these S-class Zeppelins, LZ 91 (L 42) entered service in February 1917. They were basically a modification of the R-class, sacrificing strength and power for improved altitude. The surviving R-class Zeppelins were adapted by removing one of the engines. The improved safety was offset by the extra strain on the airship crews caused by altitude sickness and exposure to extreme cold and operating difficulties caused by cold and unpredictable high winds encountered at altitude. The first raid of 1917 did not occur until 16–17 March: the five Zeppelins encountered very strong winds and none reached their targets. This experience was repeated on 23–24 May. Two days later 21 Gotha bombers attempted a daylight raid on London. They were frustrated by heavy clouds but the effort led the Kaiser to announce that airship raids on London were to stop; under pressure he later relented to allow the Zeppelins to attack under "favorable circumstances". On 16–17 June, another raid was attempted. Six Zeppelins were to take part, but two were kept in their shed by high winds and another two were forced to return by engine failure. L 42 bombed Ramsgate, hitting a munitions store. The month-old L 48, the first U class Zeppelin, was forced to drop to where it was caught by four aircraft and destroyed, crashing near Theberton, Suffolk. After ineffective raids on the Midlands and the north of England on 21–22 August and 24–25 September, the last major Zeppelin raid of the