Interesting read on it.
By Dave O'Malley
Inside the glassed-in nose of a Heinkel He 111 bomber, a pilot and his navigator/bombardier sat in silence, a silence that only they recognized beneath the blasting thunder of their ship’s two Jumo V-12 engines. Tonight was a good night to be out over England in the summer of 1942—dark and moonless. Tonight’s target was the city of Coventry—according to Tomas his navigator, just 130 miles to the west. Tomas spoke quietly on my the intercom, “We are just north of Ipswich now, still another 40 minutes to go.” He was glad Tomas knew where they were. The pilot had been to Coventry a year ago, and he hoped this would be the last time. Outside the cockpit, all was total darkness, no light above or below. He no longer could see the vague silhouettes of the others, or even their exhaust flares. Just blackness. The night was a dark friend. So far so good.
Ten seconds later, the comforting cover of night was turned into the blinding light of day. In a single moment, the cockpit had become a searing blue-white room of unholy light crossed by shifting shadows. Within the light, the engines seemed to shriek like banshees. The pilot’s first reaction was incredulity—there was no searchlight that he had seen below, yet somehow it had found him the instant it was turned on. How was it possible? A millisecond later, he reefed the Heinkel into a diving left turn, with Tomas, who had stood up to move down to the bomb aiming position, slamming onto the cockpit glass on the starboard side. The beam of light seemed to follow him down and was so broad, he could not get out of its grasp. He could hear his gunners, Gerhard on top and Arno in the ventral turret hammering away at something with their MG 81s. The cockpit smelled of cordite and an odd whiff of something electrical. While the pilot corkscrewed, tracer rounds started washing by like liquid blobs of light and then rounds started thumping and ripping into his aircraft.
This fanciful scenario was what inventor Sydney Cotton, Air Commodore William Helmore (the godfather of Photo Reconnaissance) and the Royal Air Force had imagined when they invented, patented, built and deployed the 2,700 million candela Helmore Turbinlite aboard a modified Douglas A-20 Havoc (Boston) night fighter. As it turned out, the system was not successful and scenarios such as this never really happened. The German pilot and his crew would continue on to the city of Coventry that August night and, along with others, drop their bombs. It was the last raid on Coventry. Five months later, the lights went out on the Turbinlite concept forever.
By late 1940 and early 1941, the concept of the night fighter was truly coming into its own. Specially dedicated squadrons were forming with specialized tactics, equipment and training. New forms of portable radars were slowly coming into use, but mostly they were only able to get a tracking night stalker to within the general area of an operating enemy bomber. Air Commodore William Helmore, as special scientific advisor to the Chief of the Air Staff, dedicated much of his time on the subject of night fighters and their equipment and, along with Cotton, came up with a concept they called ATI—Air Target Illumination. The idea was to put a searchlight in the nose of an aircraft, and using both ground radar and new RDF (Radio Direction Finding) radar in the aircraft, guide the pilot to within striking distance of the enemy at night. At this point the pilot would switch on his searchlight, illuminate the bomber and accompanying fighters would shoot it down.
The concept of illuminating enemy aircraft at night, for satellite fighters to take out, seemed simple enough, and this alone most likely drove inventors and the RAF to push forward with the concept even as better radars were being developed. The idea was to attach the world’s most powerful searchlight to the nose of a powerful twin-engine night fighter. The light itself was designed for this specific purpose under the patents and direction of Helmore and Cotton and was far more powerful than any military light of the day. To understand exactly how powerful it was, a comparison should be made. The service searchlights in use by the Army and Navy up to this point consumed 150 amps of current. The Helmore Turbinlite drew 1,400 amps. Specially designed 12-volt batteries were created which could discharge in 120 seconds. The 48-battery array was carried in the fuselage and weighed so much (nearly 2,000 lbs) that the Turbinlite aircraft could carry no offensive or defensive armament. The light burned through its carbon rods at a prodigious rate, these being fed mechanically as they were consumed by the arcing electricity from the batteries, generating considerable heat and toxic gas fumes. The heat and gas output problem was dealt with by a chin intake which drove cooling air into the nose section and forced it out through a hydraulically-actuated vent door on the starboard side. The light itself had an elliptical reflector, which projected a horizontal “sausage-shaped” beam of light with a 30 degree divergence. This gave a horizontal light coverage of 950 yards wide at one mile ahead of the aircraft. This powerful and wide beam would light up any bomber ahead for a mile, allowing the accompanying Hurricanes (sometimes Bolton Paul Defiants early on) to spot and attack the enemy aircraft. The two parasite fighters in the team kept station on the Turbinlite Havoc throughout the chase using formation lighting on the Havoc’s wings. This lighting was in the form of a white strip along the trailing edge of the main plane on both sides, illuminated by an angled lamp. Using small elevator inputs, the Havoc pilot was to keep the beam on the enemy as the Hurricanes made their attack.
Of course, operating in relatively close formation in the dark with barely visible lighting required radio work to fully communicate in an environment where hand signals did not work. This meant that instructions and communications via radio could be detected by the enemy. A system of code words and expressions were used to communicate command and intentions—all kept to the bare minimum. The pilot of the Turbinlite Havoc, unable to see the Hurricanes on his wings would ask “ARE YOU SNUGGLING?” (Are you in formation?) If he did see the Hurricanes and wanted them to close formation, he would order this with the single word “CONTRACT” and “EXPAND” if he wished the formation to open up. When the Havoc was within 5,000 feet of the target, the pilot would declare this with the single word “WARM.. If he wanted to tell the Hurricane pilots that he was dropping back he would say “COOLER.” At 3,000 feet back, he would declare “HOT,” to which the Hurricanes were obligated to confirm receipt of the message by saying “UNDERSTAND HOT.” Ten seconds before illumination, the Havoc pilot would say “BOILING.”
The Hurricane pilot had a code as well to communicate with the Havoc in the lead. Approaching the Havoc, and in need of the formation lights, he would say “SHOW UP” and if he felt that station keeping lights were too bright, he would say “CLOSE WINDOWS”. Other signals were “I AM DESOLATE” (I have lost you), “I AM SKYLARK” (I am above you), “I AM SNAKE” (I am below you) and “I AM PANCAKING” (Obliged to return to base). The forward-firing machine guns of the straight Douglas Boston and Havoc night fighters were removed as were any defensive guns. The Turbinlite Havoc carried primitive AI Mk IV airborne interception radar, the RAF’s first air-to-air radar system. The radar was used to bring the Havoc and Hurricane hunter-killer team close to a formation of German bombers and leave the Helmore Turbinlite to illuminate the target. Operation of the radar equipment was just as much an art as it was a science and the effective use of the system depended on the experience and the ability of the operator to correctly interpret the displays on its two cathode ray tubes.
