The Intruder Dornier Do 17 Z-7 and Z-10 1940–1941

On the blog today, Chris Goss, author of Dornier Do 17 Units of World War 2, gives a brief overview of his book.

In June 1940, Maj Wolfgang Falck, formerly of 2 Staffel/Zerstörergeschwader 76 (2./ZG 76) and latterly commander of I./ZG 1 was tasked to form a nightfighter unit for defence of the Reich. The preferred nightfighters were the Messerschmitt Bf 110 and Junkers Ju 88C-2/C-4 but there would also be two versions of the Do 17 used as nightfighters – the Z-7 Kauz I and the Z-10 Kauz II (‘Kauz’ translated as ‘Screech Owl’). The glazed nose was removed from a Do 17 Z-3 and replaced by the nose from a Ju 88C-2/C-4. The armament was three 7.9mm machine guns and one 20mm cannon and the aircraft designated the Do 17Z-7. This was soon found to be unsatisfactory and an entirely new nose designed which increased the armament to four machine guns and two cannon. In the tip of the nose was an infra-red spotlight called Spanner-Anlage which was later replaced by first-generation FuG 202 Liechtenstein radar. This aircraft was now designated the Do 17Z-10.

Precise numbers of Do 17Z-7 and Z-10s are hard to define but it is thought that eight Z-7s were produced and the survivors were later converted to be Z-10s of which around 11 were produced. The Z-7 first entered service with I./Nachtjagdgeschwader 1 (I./NJG 1) on or about 22 June 1940 and the first recorded combat probably came on the early hours of 29 June 1940 when a Whitley of 58 Squadron flown by Plt Off Bill Espley reported damaging a nightfighter near Eindhoven. A Do 17Z-7 of 1./NJG 1 coded G9+GK and flown by Uffz Hugo Schwarz was damaged in combat and later crash-landed near Mönchengladbach. Schwarz and his radio operator Fw Gerhard Palm were both injured while the engineer Fw Ludwig Born later died of his wounds.

In August 1940, the Do 17Z-7s and Z-10s now became part of II./NJG 1. The Gruppe would be commanded by Maj Karl-Heinrich Heyse, an experienced bomber pilot. Two of the Staffel operated the Ju 88C-2/C-4 – 4 Staffel was commanded by Oblt Herbert Bönsch while 6 Staffel was commanded by Oblt Karl Hülshoff. Just 5 Staffel appears to have operated the Do 17Z-7/Z-10 and was commanded by Hptm Rolf Jung. However, Maj Heyse would be reported missing in action over the North Sea on 23 November 1940 while flying a Ju 88C-4 and was replaced by Hülshoff and, as on 11 September 1940 II./NJG 1 had become I./NJG 2, command of Hülshoff's 3./NJG 2 went to Oblt Ulrich Mayer.On 17 July 1940, Oberst Josef Kammhuber was given command of the new 1 Nachtjagddivision. He firmly believed that suitably converted bombers such as the Do 17Z and Ju 88 flown by experienced crews would be ideal for Fernnachtjadg (long range nightfighter) missions over the UK and later said:

‘When I want to kill wasps, I smoke out their nest. I don't swat insects in the air one at a time, I go to the nest when they are in!’

So it was that II./NJG 1 and then I./NJG 2 began intruder operations over British airfields from Gilze-Rijen in Holland.

It is difficult to tie the majority of 2./NJG 2's kills to the Kauz II as it was only used in very small numbers and was soon replaced by the Ju 88C. For example, during the period June to October 1940, Do 17Z-7s and Z-10s were only used on 19 nights flying 22 sorties. Uffz Vincenz Giessübel flew his first intruder mission in a Do 17Z-10 on the night of 15/16 November 1940 and only flew another three before the end of the year.

However, the first recorded successful interception by a Do 17Z-10 came on the night of 9 September 1940 and was the first success of the war for Fw Hermann Sommer of 5./NJG 1, albeit his claim was optimistic. He had taken off from Gilze-Rijen at 2105hrs and claimed to have shot down a Blenheim in the circuit at RAF Waddington in Lincolnshire at 2315hrs. Although not mentioned in any detail in the 15 Squadron records, it is believed that Sommer attacked a Blenheim flown by Plt Off James Kee who was the pilot of one of ten aircraft briefed to attack Ostende harbour. All that it is said is that he was attacked by an enemy aircraft and successfully landed the damaged aircraft at RAF Wyton.

The first confirmed kill by a Do 17Z-10 came at 2125hrs on 16 October 1940 and was credited to Lt Ludwig Becker. 4./NJG 1 was still operating the Do 17Z-10 before converting to the Bf 110 shortly afterwards; Becker recorded the following:

‘I was well positioned at the correct altitude of 3300m and directed onto enemy by a series of continual corrections. Suddenly I saw an aircraft in the moonlight about 100m above and to the left. On moving closer I made it out to be a Vickers Wellington. Slowly I closed in behind and aimed a burst of five to six seconds duration at the fuselage. The starboard engine caught fire immediately and I pulled my aircraft up. For a while the Englishman flew on, losing height rapidly. The fire died away but I then saw him spin towards the ground and burst into flames on crashing.’

The Wellington was not English but Czech and from 311 Squadron engaged in at attack on Kiel. Plt Off Bohumil Landa and three of his crew were killed when the bomber crashed at Oosterwolde in Holland but two more crew were captured.

The first confirmed intruder success and almost definitely caused by a Do 17Z-10 was a Hampden shot down by Lt Heinz Völker near Scampton at 0030hrs on 28 October. The 49 Squadron Operational Record Book states what happened:

‘One aircraft was attacked by an enemy aircraft while circling the Q site on return. The aircraft suffered slight damage including three burst tyres and shot accumulator. Hampden X3027 landed in the sea half a mile off Skegness. It is believed that they had been shot up by an enemy aircraft while over this aerodrome [Scampton].’

The damaged Hampden X3001coded EA-H was flown by Plt Off John Green who landed without incident at 0140hrs but there were no survivors from Plt Off John Bufton's aircraft. Völker would then claim a Blenheim over the North Sea on the night of 22 December again probably flying a Do 17Z-10 but this cannot be matched with any RAF losses. In 1941, Völker would convert to the Ju 88C-2/C-4 and fly with 3./NJG 2 claiming another five RAF aircraft on intruder missions, becoming one of the most successful intruder pilots to date. There would be one more claim for him when at 0130hrs on 22 July 1941, he collided with a Wellington of 11 Operational Training Unit which was preparing to land at RAF Bassingbourne, both aircraft then crashing at Ashwell in Hertfordshire with the deaths of the three German and eight RAF aircrew. 

There are only three other nights where Luftwaffe records specifically mention Do 17Z-10s shooting down RAF aircraft. The first was the night of 10/11 February 1941 when four aircraft, three of them flown by Hptm Rolf Jung, Oblt Albert Schulz and Lt Joahnnes Feuerbaum, were involved. The first claim was made by Oblt Schulz whose claim was optimistic and no losses can be attributed to his attack. Furthermore, he actually attacked RAF Coltishall where Spitfires of 222 Squadron and Hurricanes of 255 Squadron were carrying out night flying practice; 222 Squadron reported afterwards:

‘While night flying was in progress at about midnight, one enemy aircraft was seen by Sgt [Rainford] Marland to be making the circuit behind the aircraft flown by Sgt [Norman] Ramsay who was then fired upon. Sgt Marland made five separate attacks on this e/a which was identified as an Me 110. Shortly afterwards incendiary bombs were dropped and two hangars sustained slight damage. A second stick was dropped and it is believed that e/a was then intercepted by a Hurricane [Sgt Leslie Barnes of 257 Squadron] and chased out to sea.’

Hptm Jung, with his crew Uffz Theo Schürks and Uffz Herbert Thomas were the next to claim and reported:

‘Take-off at 2345hrs, landing at 0346hrs, over target area 0100–0300hrs. Observed four landing aircraft near illuminated airfield 10280. Own plane was detected too early. The lights of the airfield were switched off. Dropped 120 incendiary bombs on accommodation and hangars from 0100–0145hrs in three attacks from 500m altitude. Observed numerous persistent fires. Fired at fire brigade crews in six low-level attacks. Observed six landing aircraft at airfield 10242 at 0220hrs. Attacked an aircraft at 100m altitude, the navigation lights were immediately switched off, further pursuit was without any result. Shot down a Wellington near 10242 in 200m altitude at 0230 hrs. After two bursts of fire, the right engine burned and the plane exploded in the air. Despite the air combat there was well-aimed light anti-aircraft fire, six hits in own machine. Attacked a Bristol Blenheim with three bursts near Great Yarmouth at 800m altitude at 0300hrs.The Blenheim was shooting recognition signals (red-yellow).Hits and fire effect recognized perfectly. Further observation of the aircraft was not possible. Subsequent loss of the aircraft can be expected.’

The only loss than can be attributed was a Wellington from 115 Squadron and captained by Sgt Harry Rogers which was returning from an attack on Hannover. The pilot managed to crash-land at Narborough near Swaffham in Norfolk with just the rear gunner suffering injuries.

On the night of 7/8 April 1941, Lt Hans Feuerbaum almost got another victim while flying a Do 17Z-10 when he claimed a Hudson near Wells flown by Plt Off Charles Alexander DFM. On the way home Feuerbaum then claimed what he thought was a Hereford but was probably a Whitley of 51 Squadron flown by Plt Off Gordon Mattey which reported being attacked by a German aircraft 60 miles east of Flamborough Head, Mattey being slightly wounded in the action. Feuerbaum would claim just one more RAF aircraft on the early morning of 3 May but he was possibly flying a Ju 88C; even the crew of his intended victim, a Whitley of 77 Squadron flown by Sgt Mills, failed to recognize what their assailant was flying.  Feuerbaum would live another one month and one day as he and his crew would be killed on 4 June near Whitby in Yorkshire when their Ju 88C-2 flew into the ground in bad weather.

The final kill that can be attributed to a Do 17Z-10 intruder went to recently promoted Fw Vincenz Giessübel who shot down an 11 Operational Training Unit Wellington over RAF Bassingbourne at 0050hrs on 24 April1941 and which then crashed onto and destroyed a second Wellington. It was Giessübel's 37th operational flight of the war and he would continue to fly the Do 17Z-10 with 2./NJG 2 on another 33 operational flights, failing to increase his score, his last operational flight being on 13 October 1941, after which he only flew the Ju 88C-4.

Do 17Z-10 losses were understandably light due to the small numbers involved and around 13 October 1941, intruder missions ceased by order of the Führer who wanted to see RAF bombers burning on German territory rather than British airfields. On 13 October 1940, Do 17Z-10 coded R4+DK crashed on landing at Gilze-Rijen injuring Uffz Erich Götz and two crew. Then on 9 November 1940, Ofw Herbert Schmidt flying R4+HK was damaged by Flak on an intruder sortie and crash-landed at Gilze-Rijen. Finally on 5 February 1941, Oblt Otto Hauser's R4+BK went missing on an intruder sortie. The second and last combat loss which also saw the last Do 17 to crash on British soil during the war came on 8 May 1941 when Fw Wilhelm Lettenmeier's Werk Nummer 2843 coded R4+GK was intercepted by a Beaufighter of 25 Squadron flown by Plt Off David Thompson with radar operator Plt Off Leslie Britain; initially the British crew had difficulty getting behind the German aircraft due to its low speed: 

‘I throttled back which caused exhaust flames to appear from our aircraft which was up moon of the Dornier which apparently sighted the Beaufighter and immediately made a steep turn to port in an attempt to evade and did evade the first burst of one second which I fired attacking on the starboard beam at a range of 100yds. I followed the Dornier which continued on a straight course after making the steep turn to port giving me the impression that the pilot of the Dornier thought he had succeeded in evading me. I followed him and fired two further one second bursts at about 100yds range from below and to starboard and I saw hits from the first burst and after the second burst the port motor of the Dornier caught on fire.’

Flight engineer Uffz Herbert Thomas recalls what happened next:

‘There was an awful crash and grinding noise and the port engine began to burn brightly. The noise was terrific. My first reaction was to get the canopy clear, close the fuel tap, cut the ignition, cut everything. I went to help Lettenmeier but our Dornier simply went down. The fire closed on the cockpit and together we gave the command to get out. Tracers went under me and the Bola [gondola] but I could not find the switch for the bale out buzzer so with a great effort I forced open the hatch against the airstream. I climbed onto the radio operator's position and to my surprise found that Georg [Uffz Herden] was still at his post. I screamed at him to jump and together we got out.’

Both survived but the pilot was killed (sadly David Thompson would be killed in a flying accident 8 July 1941). Do 17 crashed at West Fen, Medlam Drain, Carrington in Lincolnshire and hit the ground at high speed, exploded and caused a deep crater. The body of Wilhelm Lettenmeier was found 100yds away with an unopened parachute. Despite being the first (and last) Z-10 to crash on land, all that the RAF could find of note was a plate stating the aircraft had been made by Dornier at Friedrichshafen, traces of machine guns were found as well as a single 15mm round and that it had been carrying 1kg incendiaries.

Although the Do 17Z-10 soldiered on, it was soon replaced by more adept nightfighters, namely the Bf 110, Ju 88C-4 and even the Do 215 B-5. The last recorded incident involving a Do 17Z-10 came on 19 September 1941 an aircraft of 2./NJG 2 suffered an undercarriage collapse at Gilze-Rijen.

To read more, pre-order your copy of Dornier Do 17 Units of World War 2.