On the night of the 14th June 1943 Bomber Command visited the German city of Oberhausen. The Oboe equipped Mosquitoes of the Pathfinder force located the centre of the old town with their sky markers and the main force bombed accurately through the cloud. Nevertheless of the 197 Lancasters taking part 17 were lost, a rate of 8.4%. The German nightfighter defences were becoming better organised and their Airborne Interception radar was making a difference.
But the use of the German radar also provided an opportunity, because once the frequency was known to the British Air Ministry scientists it was possible build a detector from which RAF fighters could home in on their Luftwaffe counterparts. The RAF had been very reluctant to let their own highly secret Airborne Interception (AI) radar sets operate over enemy territory, because if the planes were shot down and the equipment discovered the Germans would be able to build their own counter measures.
Eventually it was decided to allow the new detector device codenamed ‘Serrate’ to be combined with an older version of the AI sets. They were mounted in Beaufighters. Twenty two year old Wing Commander J.R.D. Braham was one of the first to use Serrate system sucessfully, together with his navigator/ AI operator Flying Officer ‘Sticks’ Gregory:
Sticks was now continuously scanning the Serrate and AI scopes. ‘I’ve got a number of indications of night-fighters, Bob. I’m taking the strongest-looking signal. Turn starboard 10 degrees and let’s see if we can get this one.’
We were now flying towards the signals emitted by a German night—fighter’s AI. The technical limitations of Serrate gave us no idea how close or far the aircraft was until we picked up contact on our own AI, but we could tell his relative position to us in space.
Flak appeared in the distance and bombers ahead of us were now under attack. ‘Sorry, Bob, that signal has disappeared. But I have another. Port 20 degrees.’
I banked the Beau round to our new course and the aircraft rocked suddenly as we hit the prop-wash of another aircraft in front of us. I couldn’t see anything but it was probably one of our own bombers. Again after a short chase, no luck.
The Serrate signal disappeared, but always there were others indicating the presence of large numbers of enemy fighters. It seemed that the enemy left his AI on only for short periods.
By now we were approaching the Ruhr and the flak ahead was becoming intense as the bombers started to unload. Fires and explosions could be seen for many miles away as Oberhausen received mortal blows.
But this wasn’t a one-sided battle. Off to the right there was a vivid flash in the sky, then a flaming comet streaked earthwards. I noted the position and cursed. It was probably one of our bombers.
‘Keep a good check on the equipments, Sticks. There arc plenty of Huns about.’ Up ahead was another fire in the sky, gradually sinking lower and lower to crash in a sheet of flame, marking the grave of another aircraft. Things were getting hot. We were close to the flaming ruins of Oberhausen and the sky above us was filled with bursting anti-aircraft shells and the flares released by the Pathfinders to show the main force where the bombs should be dropped.
There were so many bombers over the city that the German gunners couldn’t hope to aim at individual aircraft. They threw up a curtain of steel in the hope of driving off their tormentors. It was in vain. The attack continued.
By now the leading bombers were turning away from the target and setting course for home. So skirting the flaming city, we headed back among their tracks. So far, I had only seen fleeting glimpses of dark shadows as we passed close to one or two of our bombers, although we flew through the prop-wash of many as we criss-crossed the stream in what seemed a fruitless search for the many German fighters.
Then there was excitement in Sticks’s voice, as he called, ‘Bob, I’ve got another signal, turn gently port.’ As I manoeuvred the Beau I counted three other aircraft on fire in the air within my range of vision. I knew our bombers rarely shot down a German night-fighter so I could only assume the enemy was exacting vengeance for the raid.
‘Bob, I think this one is behind us. The signal is strong.’
‘Have you anything on the AI yet?’
‘No, but keep turning’
It was an eerie feeling, knowing that we were playing a deadly game of hide-and-seek with an unseen foe.
‘Bob, I’ve AI contact 2,000 yards behind. Hard as possible port.’ ‘Are you sure it isn’t one of our bombers?
‘Yes. It isn’t. The Serrate and AI signals match up. Keep turning, he’s only about 1,000 yards and 20 degrees on your port and a little above. Now ease the turn a little, and watch it. You’re closing fast, you should see him in a second. He’s only 600 yards and still well over to port.’
‘I’ve got him, I’ve got him,’ I yelled excitedly.
In the moonlight I caught a glimpse of an aircraft on my port beam. At that moment he straightened out, heading south at 10,000 feet. An Me 110. Perhaps he had lost me on his AI. At 400 yards’ range I opened fire, gradually easing off the deflection so that as I rolled in astern of him the dot on my electric gunsight was centred on his fuselage.
Explosions appeared all over the Me. Burning brightly he dived steeply towards the earth. By now Sticks had his head out of the ‘office’ and was shouting encouragement as he watched our enemy crash in a mighty flash of flame.
This was no time to relax. ‘Keep a look-out on your set, Sticks. There are lots ofthe blighters about.’ Checking the position of our fight, I noted that the Me 110 had crashed on the north-east shore of the Zuider Zee.
Wing Commander J.R.D. Braham was one of the top scoring RAF aces of the war. See J.R.D. Braham: Scramble!: An Autobiography
A good history of the use of Serrate can be found at Lancaster-Archive.