More Hawker Typhoon exploits from Peter Brett - part 26
On 6th April [1944] I had my first flight in an 'RP' (Rocket Projectile) Typhoon, practising 30 degree dives on to a target in Poole harbour. Then, on the 11th April, the squadron was moved to Llanbedr in North Wales to undergo a ten day rocket firing course. The flight there was quite eventful since we were forced by weather to land at Weston Zoyland. This airfield had a particular runway that was very short, only some 850 yards, and as luck would have it this was the one in use that day. The C.O. warned us all by radio before we landed and told us that, if we did not touch down very near the start of the runway we were to open up and go round again. I managed to get down fairly shortly after crossing the boundary but all of us had difficulty stopping in time. In my case it resulted in the brakes overheating so badly that, just after I turned off the runway, there was a loud bang, the starboard wing dropped, and I swung sharply to the right. My starboard tyre had burst and I was stuck. The squadron managed to take off later in the day when the weather improved but I had to remain another day until a spare wheel was brought down (in a motorcycle and sidecar!) and fitted so that I could follow them. During this ten day course I flew several different aircraft but not 'my' HF-E since it was not returned modified with rocket rails until after the course was over.
It surprised me that some of the pilots were a bit worried as to what would happen when they fired their rockets, especially when firing a salvo of eight projectiles. It appeared that they were worried about recoil! We had been told that the effect of firing a salvo of rockets was the equivalent of a broadside from a light cruiser! This made some pilots think that they were going to experience the recoil equivalent to the firing of eight naval guns! Had this really been the case the aircraft would have fallen apart from the shock! In reality of course there was no recoil at all since, if anything, the rockets tried to pull the aircraft forward. They were held onto the guide rails by a short length of 16-SWG soft copper wire which was there to prevent them sliding off if the aircraft happened to get too nose-down. On firing, the copper wire broke, and the rocket released.
Each rocket consisted of a tube about four inches in diameter and about five feet long which contained the solid fuel motor. The fuel was a very fast burning, waxy looking piece of extruded plastic explosive, in the form of a cross. To the front end of this was screwed on the warhead which could be of several types. The most common was 60lb explosive but we also used 40lb armour piercing, 60lb phosphorus incendiary and even 40lb anti-personnel heads. These latter had a small propeller at the front. When fired the propeller rotated and unscrewed a thread which allowed a 3ft long telescopic probe to extend out of the front. This probe ensured that the explosive went off before the rocket buried itself in the ground and thus had the maximum blast effect. At the rear end of the motor tube were clipped on four fixed vanes, which were just flat steel plates which kept the missile straight in flight. The whole assembly was over six feet long and weighed some 150 pounds. It took two men to load each one on to its rails, which themselves were formed of twin aluminium tubes on which the rocket hung by means of a sort of twin 'coat-hanger' of thin steel strip.
The aiming of the rockets was much less haphazard than the aiming of the bombs. The reflector gunsight normally projected an orange image of a circle with a dot in the middle, bisected by a horizontal line with a break in the middle, on to the windscreen. The break in the horizontal line could be varied in width by adjusting a knurled ring below the sight. The idea being that you set it to give the apparent wingspan of the aircraft you were attacking at the optimum cannon range. In order to sight the rockets, the image had been turned 90 degrees so that the line with the break in the middle was vertical. Instead of aiming with the dot, you used the top of the lower half of the line as an aiming point and, by adjusting the gap and consequently the height of the tip of the bottom line, could adjust the site for various angles of dive - even down to zero angle for low level attacks. The trajectory of the rocket projectile was somewhat odd in that whilst the motor was firing, for about the first three seconds of its flight, the trajectory was practically level (relative to the attitude of the aircraft). As soon as the motor burnt out, the projectile followed a normal ballistic curve like a shell or a bullet. The trajectory therefore depended on the aircraft speed at the moment of firing. Whatever speed this was, the motor added another 600mph or so during its burning, so that the final speed at motor burn-out could be anything from about 800mph to over 1000mph.
Somehow I seemed to be able to judge the trajectory quite well and I gained a reputation as a 'Dead-Eye Dick' with RP's, thus redeeming my abysmal failure as an air-to-air cannon marksman. With eight rocket rails carrying eight rockets and sometimes also with long range tanks the performance of the Typhoon was sadly depleted except in the dive when the increase in speed was dramatic! Since 'my' aircraft had not yet been returned, when we were due to leave Llanbedr and return to the South coast, I was unlucky enough not to draw an aircraft and had to make the trip as a passenger in an Anson. As soon as we returned to Tangmere we were posted yet again. This time to Thorney Island where we were under canvas as a mobile 'airfield', obviously in preparation for the invasion of Europe, but of course with no idea when this would be.
[There is some youtube footage here http://www.youtube.com/watch?v=KrdfbrwcuM8 of rockets being assembled, loaded and fired. Note the black and white stripe paint scheme on the Typhoon wings. PB tells me this was done just before D-Day to aid in the identification of Allied aircraft. ==TOW]