Luftwaffe responses.

  Part 7.  

Anti Courier Flights Operations.

  The Allied operations.  


The BOAC wartime logo.




A converted Mosquito FB Mk.VI in BOAC "livery".  Drawing by Mr. Nils Mathisrud ©, with his kind permission.


A Lodestar.  Drawing by Mr. Nils Mathisrud © (VINGTOR), with his kind permission.

  A DC-3 of ABA.   The Dakota, which ferried V-2 parts to the UK.  


  Throughout the war British Overseas Airways Corporation (BOAC) continued their airline operations mostly in support of the war effort.  One of the more spectacular routes established were the one from Leuchars in Scotland to Bromma near Stockholm in Sweden.  The first flight was conducted as early as 12 April 1940 and continued at irregular intervals with two flights about a month.  A more regular service started in August 1941.  The aircraft employed included Hudsons, 12 Lodestars, Whitleys, CW-20 (C-46), Dakota (C-47) and 10 Mosquitos.  Among the passengers were Scandinavian nationals, who wanted to go to the UK and join the fight against Germany, but also individuals even more vital to the allied war effort.  Professor Niels Bohr , who helped design the "Atom Bomb" flew from Bromma 6/7 OCT 1943 in the converted bomb bay of a Mosquito.  The SOE and MI 5 was deeply involved in some of the passengers and cargo ferried.  Part of V-Weapons, which through malfunction had crashed in Sweden was ferried on this route.  Material collected by the Clandestine Danish Intelligence Service was complied in Sweden, processed and passed to MI 5.  And finally Sweden sold ball bearings to the allies, which were also ferried along this route.  Many of the aircrew were Norwegians, who had fled the country after the German occupation, were enlisted and trained in the RAF and were on contract with BOAC.  
  The Swedish airline "AB Aerotransport" (ABA) company serviced the route with DC-3 from 16 FEB 1942, until it suffered some losses in the autumn of 1943.  The service was then interrupted until 9 OCT 1944, when it was resumed utilizing converted B-17s.  Swedish aviation 1940-1949  
  From 31 MAR 1944 the USAAF also participated in these operations employing the C-47 and C-87 Liberator in  "Operation Sonnie", where in the nature of things the OSS was deeply involved.  1.200 interned allied airmen, who had come down in Sweden, were returned to join the fight.  About 500 sorties were flown by the USAAF, with only one aircraft lost, and that to a weather related accident.  
  One source states that a total of 2784 sorties were flown by all operators for a total loss of 8 aircraft.  The average number of sorties seems to have been around 5 nightly.  The reason for the low loss-rate is explained below, but it should also be noted that I JK to a large extend did not even attempt to commit fighters against the courier flights.  


The memorial erected in honor of the crew who lost their lives in the accident mentioned above.



The routes used.


  Leuchars, the base station of the BOAC operation.  

The German response.



A Ju 88C-6 of 12./NJG 3, the same version was used by 10./NJG 3 Via J. Junker ©, with his kind permission.



A wonderful profile of the aircraft above by Simon.

  The Germans were fully aware of the flights, and as the Luftnachrichten Dienst expanded it became - at least in theory - possible to intercept and shot down the transports.  For the flights over Norway it was a question of expanding the radar coverage and providing night fighters.  For the flights through The Skagerak (the waters between Norway and Denmark) the matter was more complicated.  The radar horizon against an aircraft at 1.000 ft extends to about 35 nautical miles (NM).  The gap is about 70 NM.  Flying below 1.000 ft it is thus possible to fly through the Skagerak undetected.  Without a radar altimeter, based on a forecast altimeter setting, flying at night, over water, below 1.000 ft is however a somewhat "interesting" experience.  So the flights were probably made at 1.000 ft or above MSL.  Up till JUL 1942 the flights could be conducted with complete impunity, since there were no German radarstations along the coast.  SCHAKAL became operational 15 JUL 1942, HYÄNE and HABICHT in MAR 1943.  


A "tracer map" from FLUKO Kolding 5/6 MAR 1943 noting: "3 Fdl. Kuriere Schweden - England, 4 Fdl. Kuriere England - Schweden".  Judging from the points where the tracks were first detected and later faded, the allied aircraft were flying at 2.000 ft.

  By the spring of 1943 the complex of Flugmeldemess Stellungen had been expanded in Southern Norway and Northern Denmark so that 75 % of Skagerak was covered by Würzburg-Riese above 1.500 ft.  It was thus possible to control night fighters in the area employing Seeburg-Lichtenstein Verfahren.  A special command tasked to counter the courier flights, NJRF 111, was established at FlH Aalb.-West and 10./NJG 3 was assigned to the NJRF along with the radarstations mentioned above.  Please see map below.  10./NJG 3 was based at FlH Aalb.-West with frequent detachments to FlH Lister.  


Location of the units involved.


  Radar coverage against an aircraft flying at 1.000 ft.  
  The flights usually followed a track along the blue line, and if the allied aircraft flew at 1.000 ft, it would be impossible to perform and interception utilizing any kind of radar.  If the aircraft flew at 2.000 ft or above, it would at best be possible to track it for up to 20 min with a Würzburg-Riese.  This assumption is confirmed by the KTB of I JK, which consistently reports tracking of the courier aircraft for about 25 min.  It then became a question of the speed-ratio between the Allied aircraft and the German fighter.  The normal procedure was for the fighter to orbit the Funk Feuer at the Stellung.  When the allied aircraft was being tracked by the Würzburg Rot, the interception would start.  In case of a C-46, C-47 or Loadstar the speed-ratio was about 1:2.  If the allied aircraft followed the track above, the German fighter would roll out behind the allied aircraft after about 10 min, and it would be within W-R range for another 10 min.  This should be sufficient to close with and engage the allied aircraft.  Even if the German fighters were on ground alert at Aalb-West or Lister, a "slow mover" (Loadstar/C-47) at 2.000 ft or above could easily be intercepted if all levels in the command and control chain acted correctly and timely.  If the allied aircraft flew at 1.500 ft, it would be passing out of W-R range by the time the German fighter had completed the interception.  The problem was that the control of the fighter could not be handed over from one Stellung to another.  In an attempt to overcome this problem, Wassermann S radars were set up at WOLF, HYÄNE and SCHAKAL in the spring of 1943.  At the same time these Stellungen were provided with 2 Y-Linien.  The concept was, that the Wassermann should track the allied aircraft and the Y-Linien should track the fighter.  The Wassermann could only give a very rough altitude indication and in an attempt to solve this problem, Freya Fahrstuhls were provided to FUCHS, HYÄNE and SCHAKAL.  This radar could give a fairly accurate height indication out to about 70 NM.  But the problem was the law of physics, not equipment.  When the Mosquito was introduced the problem became almost insurmountable.  The cruising speed of a Mosquito approached that of the maximum speed of a Ju 88C-6.  A small number of Fw 190 from 10/JG 11 were then employed, and JG 11 actually succeeded in shooting down a few courier aircraft.  A Mosquito could only be intercepted, if the German nightfighter was pre-positioned in the gap, and it had a sufficient speed advantage.  
  The Freya Fahrstuhl at HYÄNE.  Col (ret'd) F.G. Tillisch.   Lt. Ziems of 10./JG 11 posing in front of a Fw 190A.  Via J. Junker ©, with his kind permission.  
  Routes through Norway.  The red circle indicates the Würzburg Riese coverage.  The northernmost route seems to be based on very hard intelligence.  In 1944 the allies had an almost complete picture of the dislocation the German radarstations in Norway, which was also fully exploited on the 12 NOV 1944 attack on Tirpitz.  From the autumn of 1944 a small number of nightfighters were stationed in Southern Norway.  


 A Ju 88G from NJ Staffel Norwegen.  © Kjetil Aakra with his kind permission.