The Messerschmitt Bf 109 K-4 was the final production variant of the 109, the ultimate refinement of the long-serving 109 design, which had first flown in 1935.
The K-series (Kurfürst - or maybe Konrad according to 'new' evidence, or perhaps Karl ) was introduced in late 1944 as an attempt to standardize the numerous earlier G-series sub-types (G-1 through G-14), which had become increasingly complex to produce and maintain. Production started in Regensburg during August 1944 while the various Gustav sub-types continued to be manufactured in parallel, including from September 1944, the G-10. Production and assembly was soon widely dispersed in the Bavarian forests while completed airframes were flight tested at two main centres, Amberg-Schafhof and Obertraubling. The K-series machines were planned as 'complete' aircraft - most of the Gustav 'options' were considered as 'standard' on the K-4, so 'add-on' Rüstsätze sets were basically limited to the R6 automatic pilot PKS 12. The K-4 was the only version of the K-series to enter mass production, as other planned variants (K-2, K-6 etc.) were only built in very limited numbers - perhaps just one prototype in the case of the K-6. Around 1,200 examples of the K-4 were delivered. The design featured a more refined fuselage/cowling with a fully retractable tall tail wheel, the larger vertical tail with bigger main wheels with new gear doors and amended wing bulges, all for better stability, along with a standardised Erla Haube for better visibility and MW 50 power boosting - the filler point of which is moved forward on the starboard fuselage. Other (external) recognition features could be the position (on the port side) of the fuel filler point, moved forward by one frame - as is the radio access hatch, also now higher up on the fuselage in comparison to the Gustav, while the DF loop is moved back one frame. Internal detail differences were numerous, including a new fuel circuit and instrument panel based on that of the Me 262. The K-4 primarily equipped Gruppen of Jagdgeschwader JG 4, JG 27, JG 52, JG 53, and JG 77. The idea that the K-4 could be a dangerous machine with its excellent climb rate and speed is difficult to prove in the face of overwhelming Allied air superiority, especially from P-51s and P-47s.
The K-series (Kurfürst - or maybe Konrad according to 'new' evidence, or perhaps Karl ) was introduced in late 1944 as an attempt to standardize the numerous earlier G-series sub-types (G-1 through G-14), which had become increasingly complex to produce and maintain. Production started in Regensburg during August 1944 while the various Gustav sub-types continued to be manufactured in parallel, including from September 1944, the G-10. Production and assembly was soon widely dispersed in the Bavarian forests while completed airframes were flight tested at two main centres, Amberg-Schafhof and Obertraubling. The K-series machines were planned as 'complete' aircraft - most of the Gustav 'options' were considered as 'standard' on the K-4, so 'add-on' Rüstsätze sets were basically limited to the R6 automatic pilot PKS 12. The K-4 was the only version of the K-series to enter mass production, as other planned variants (K-2, K-6 etc.) were only built in very limited numbers - perhaps just one prototype in the case of the K-6. Around 1,200 examples of the K-4 were delivered. The design featured a more refined fuselage/cowling with a fully retractable tall tail wheel, the larger vertical tail with bigger main wheels with new gear doors and amended wing bulges, all for better stability, along with a standardised Erla Haube for better visibility and MW 50 power boosting - the filler point of which is moved forward on the starboard fuselage. Other (external) recognition features could be the position (on the port side) of the fuel filler point, moved forward by one frame - as is the radio access hatch, also now higher up on the fuselage in comparison to the Gustav, while the DF loop is moved back one frame. Internal detail differences were numerous, including a new fuel circuit and instrument panel based on that of the Me 262. The K-4 primarily equipped Gruppen of Jagdgeschwader JG 4, JG 27, JG 52, JG 53, and JG 77. The idea that the K-4 could be a dangerous machine with its excellent climb rate and speed is difficult to prove in the face of overwhelming Allied air superiority, especially from P-51s and P-47s.
Having already given up a Staffel - 9./JG 77 - to the 'defence of the Reich' earlier in the year as well as pilots and aircraft to I./JG 53, III./JG 77 under Hptm. Armin Köhler abandoned their remaining Gustavs and departed Hungary during mid-September for rest and refit in Germany, transiting via Vienna to land in Neuruppin, Berlin on or around 13 October 1944. By the end of the month they had taken on strength a full complement of brand-new Bf 109 K-4s, around 75 machines. V./KG 2 was incorporated into the Gruppe as a fourth Staffel (see Prien JfV Teil 13/VI, page 46).
By 1 November 1944 around 155 K-4s had been delivered; in addition to III./JG 77, both JG 4 and JG 27 had K-4s. III./JG 27 were scrambled for the first time against a huge USAAF raid on 2 November. Ten K-4s were lost, along with nine pilots (four KIA) - only Uffz. Arno Mittmann (11./JG 27) filed a claim, a P-51 shot down south-east of Aschersleben. The first K-4 'victory'...
During the 'calm' that followed in November, III./JG 26 received some 35 K-4s and a further similar number went to III./JG 4 at Alteno. Intercepting a force of 200 B-17s raiding hydrogenation plants at Merseburg and Leuna on 21 November, the K-4s of III./JG 4 accounted for four Viermots but lost at least four to the P-51s, including 'black 5' (WNr. 330321) flown by Uffz. Rolf Langestroer of 10. Staffel. On 26 November III./JG 27 up from Grossenhain (east of Leipzig on the Elbe) intercepted another huge USAF bomber formation raiding fuel installations in central Germany, well over one thousand aircraft including some 500 escort fighters. Some 13 K-4s were lost, four pilots were KIA while ace and Staffelkapitän 12./JG 27 Oblt. Emil Clade who had only recently returned to combat after injury was downed by P-51s but managed to bail out over Vechta. In his memoir he recalled;
"I was hanging from my parachute, but the wind was spinning me around and this pendulum motion threatened to slam me violently into the ground as I descended at about eight metres per second. But it stopped just before I hit the ground - I landed in a trench with soft soil. Once again, I had been lucky. That same evening, I was back with the unit and noticed the many empty spaces within the Gruppe. The next day we went back into battle..."
27 November saw another large-scale USAF raid (1149 bombers accompanied by 900 escorts). Luftwaffe fighter losses totalled some 81 machines. Both II. and III./JG 27 lost K-4s as did III./JG 26 - WNr. 330372 'white 21' flown by Oblt. Gottfried Schmidt of 9./JG 26 came down near Münster, the 4th victory of 356th FG P-51 pilot Cpt. Ray Withers. Having lost most of its K-4s III./JG 26 converted onto the D-9 during January 1945..
"I was hanging from my parachute, but the wind was spinning me around and this pendulum motion threatened to slam me violently into the ground as I descended at about eight metres per second. But it stopped just before I hit the ground - I landed in a trench with soft soil. Once again, I had been lucky. That same evening, I was back with the unit and noticed the many empty spaces within the Gruppe. The next day we went back into battle..."
27 November saw another large-scale USAF raid (1149 bombers accompanied by 900 escorts). Luftwaffe fighter losses totalled some 81 machines. Both II. and III./JG 27 lost K-4s as did III./JG 26 - WNr. 330372 'white 21' flown by Oblt. Gottfried Schmidt of 9./JG 26 came down near Münster, the 4th victory of 356th FG P-51 pilot Cpt. Ray Withers. Having lost most of its K-4s III./JG 26 converted onto the D-9 during January 1945..
Below; III./JG 4 Bf 109 K-4. Visible in this poor-quality image are the outer main gear doors, retractable tail wheel, tall tail, Morane antenna and the vertical bar of III. Gruppe on the RV bands.
In III./JG 77 the mostly new pilots were virtually straight out of flight training and flying under the guidance of a handful of experienced 'mentors'. There were relatively few losses during conversion training - which given the Luftwaffe 'fixation' on the 'Big Blow' was largely focused on 'group' takeoffs and flying in large formations. On 27 November Lt. Ottmar Zieher (flying 'gelbe 8' WNr. 330 176) and Ofw. Karl Gabriel in 'gelbe 3' (WNr. 330 221) collided during a training flight and were killed.
III./JG 77 was declared 'operational' ('einsatzbereit') with 55 serviceable Bf 109 K-4s (68/55) and 58 pilots (62/58) at the end of November 1944. The first combat sortie of the 'new' III./JG 77 was flown in concert with the rest of the Geschwader on 2 December - scrambled against 8th AF bombers attacking rail targets in the south-west of the Reich, Fhr. Willi Schmitz of 10./JG 77 flying 'red 2' (WNr. 330 151) crashed attempting to get airborne from Neuruppin while Obfhr. Bartholomäi had to belly-land WNr. 330 185 with engine damage. The Gruppe subsequently shifted to Düsseldorf to support the imminent Ardennes offensive.
At the end of the November, III./JG 3 had received its first 10 Bf 109 K-4s. Eleven more arrived in December - the first loss was an 11. Staffel machine, WNr. 330455, reported on 2 December.
Below; Bf 109 K-4, WNr. 330 230, "white 17" assigned to the newly reconstituted 9./JG 77 in Neuruppin, November 1944. Visible is Lt. Hans-Werner Renzow, leader of 10. Staffel (in cap) leaning on the windscreen. This early K-4 (note antenna mast on canopy) was lost on 1 January 1945 with 10./JG 77 pilot Uffz. Heinrich Munninger at the controls. (shot down and killed north-east of Antwerp).'White 17' is just one of the subjects on the new AIMS decals 'Bf 109 K' decal sheet designed for the Kotare 1:32nd Bf 109 K-4 kit.
Below; Uffz. Alfred Nitsch - former recce pilot and instructor - in the cockpit of his 12./JG 77 'blue 3' at Neuruppin, late October 1944. The aircraft is K-4 WNr. 330 177. Note the antenna mast on the folding hood section, a feature of an early series machine. WNr 330 177 was lost during the Ardennes campaign on 23 December at Houverath with Fw. Hans Rossner at the controls.
Note the 'C3' fuel-filler stencil indicating that the K-4's DB 605 D has been uprated to take 96 octane fuel in conjunction with MW 50 power boosting. Note on the lower part of the engine fairing one of the four fixation points for the transformer powering certain cockpit instruments. WNr of Hackler's machine may have been 330 196. Another 'gelbe 10' WNr. 331 503 was lost on 26 December near Liege, pilot Uffz. Benno Kobsch KIA.
All fighter Gruppen flying the Bf 109 K-4 were in action on the Western Front from 17 December in support of the German 'Wacht am Rhein' ground offensive through Belgium. III./JG 4 lost five K-4s in combat with 366th FG P-47s, while III./JG 27 lost three K-4s and two pilots. At least 20 Bf 109 K-4s were lost on 18 December, including ten III./JG 27 machines. III./JG 77 lost its first K-4s on operations during the course of this second day of the offensive. Victories were increasingly rare. From 2 November to 29 December, only three Luftsiege were awarded to 12./JG 27, two of which were credited to StaKa Clade: one P-47 on 25 December and another on 26 December, both Thunderbolts shot down during defensive patrols by III./JG 27 in the Saint-Vith sector. Operating over this front no fewer than 12 III./JG 77 Bf 109 K-4s were lost on 23 December in combat with 373rd FG P-47s. Lt. Hans Renzow, StaKa of 10./JG 77, claimed two P-47s. That same morning Maj. Karl-Heinz Langer's III./JG 3 claimed three B-26 Marauders west of Liège. After the guns of his K-4 jammed, Fhr. Adolf Tham of 10. Staffel (Bf 109 K-4 WNr. 330456) voluntarily rammed the 574th BS B-26 coded 4L-P (s/n 42-107597 flown by 1st Lt Ralph Lesmeister). Tham's wing sawed into the tail of the B-26 instantly killing the tail gunner. The rest of the American crew bailed out and were taken captive. Despite having his port wing torn off in the collision Tham himself managed to take to his chute and thus also survived the attack..he re-appeared at Lippspringe several days later with it under his arm..
On the last day of 1944 and following recent aircraft losses, particularly during the bombing of Düsseldorf/Lohausen, a group of pilots from III./JG 77 left for Regensburg to pick up new aircraft. A few new recruits arrived from Neuruppin to fill the gaps in the pilot ranks. Although still 'top secret', the next day's operation 'Bodenplatte' did not prevent offensive patrols from being flown;
" On the afternoon of 31 December, 20 Bf 109 K-4s from what remained of our III./JG 77 were airborne under the command of Lt Hackler (StaKa 11./JG 77). Our mission was hunting enemy fighter-bombers attacking ground targets. We were then to land at Dortmund. Visibility was very poor: the cloud deck was at 300 m, while wisps of fog and cloud descended to the tree tops. Uffz Heinrich Munninger was my wingman. Over Münster, Spitfires dove down on us through a break in the clouds. Two Bf 109s were shot down." (Uffz Johann Twietmeyer, 10./JG 77)
During the two-against-one combat, three JG 77 pilots were in fact downed.. Ofhr Fritz von Rath (10./JG77) was killed near Memer, Lt Gerhard Eck (11./JG 77) was reported missing in the Münster sector; finally, Fw Karl Böttner (11./JG 77), a veteran of North Africa and an ace with 25 victories, was wounded in the leg. He was able to jump clear of his K-4, but the shock of the parachute opening caused him to lose a fur-lined boot and he hit the ground with a partially frozen foot. He did not return to the front..
Below; Fw Karl Böttner in Bf 109 K-4 'yellow 6' at cockpit readiness Note antenna mast on folding hood.. Born 11 Aug 1921, Hanover. In 1942 in EJG Ost. Went to 8./JG 77 in Jan 1943. Claimed his 25th victory on 23 Aug 1944. Was at that time in 11./JG 77. Shot down by Spitfires in 'yellow 2' (WNr. 330196) and WIA on 31 December 1944 and in Lazarett until 8 May 45. Deceased in 1995.
On the last day of 1944 and following recent aircraft losses, particularly during the bombing of Düsseldorf/Lohausen, a group of pilots from III./JG 77 left for Regensburg to pick up new aircraft. A few new recruits arrived from Neuruppin to fill the gaps in the pilot ranks. Although still 'top secret', the next day's operation 'Bodenplatte' did not prevent offensive patrols from being flown;
" On the afternoon of 31 December, 20 Bf 109 K-4s from what remained of our III./JG 77 were airborne under the command of Lt Hackler (StaKa 11./JG 77). Our mission was hunting enemy fighter-bombers attacking ground targets. We were then to land at Dortmund. Visibility was very poor: the cloud deck was at 300 m, while wisps of fog and cloud descended to the tree tops. Uffz Heinrich Munninger was my wingman. Over Münster, Spitfires dove down on us through a break in the clouds. Two Bf 109s were shot down." (Uffz Johann Twietmeyer, 10./JG 77)
During the two-against-one combat, three JG 77 pilots were in fact downed.. Ofhr Fritz von Rath (10./JG77) was killed near Memer, Lt Gerhard Eck (11./JG 77) was reported missing in the Münster sector; finally, Fw Karl Böttner (11./JG 77), a veteran of North Africa and an ace with 25 victories, was wounded in the leg. He was able to jump clear of his K-4, but the shock of the parachute opening caused him to lose a fur-lined boot and he hit the ground with a partially frozen foot. He did not return to the front..
Below; Fw Karl Böttner in Bf 109 K-4 'yellow 6' at cockpit readiness Note antenna mast on folding hood.. Born 11 Aug 1921, Hanover. In 1942 in EJG Ost. Went to 8./JG 77 in Jan 1943. Claimed his 25th victory on 23 Aug 1944. Was at that time in 11./JG 77. Shot down by Spitfires in 'yellow 2' (WNr. 330196) and WIA on 31 December 1944 and in Lazarett until 8 May 45. Deceased in 1995.
For more on the K-series see Jochen Prien, Peter Schmoll ('Me 109 Produktion und Einsatz'), Christophe Cony and Jean-Louis Roba - the four-part series on the Bf 109 K in issues 242-245 of 'Avions' is one of my preferred reference sources on the type.