to fly directly at the target and thereby expose the gunner to attack. As TOW developed, it continued to grow larger and gain more range, ultimately emerging as a much larger design similar to the Swingfire. The US suggested the British adopt the TOW, but the necessity for the tracker to be inline with the missile throughout its flight was considered completely unacceptable to the British while the US saw this as irrelevant. Any plans to introduce TOW in British service ended. FV438 Swingfire Initially, some consideration was given to adding four Swingfire missiles to the Chieftain. Their external mounting was a significant problem, and fitting them required changes to the sighting systems, none of which was inexpensive. As the Royal Ordnance L11 main gun underwent development it proved far more powerful than expected and the extra hitting power of the Swingfire was no longer seen as a benefit worth the cost. In November 1962, GOR.1174 was issued for a light vehicle to carry Swingfire instead, selecting the FV432 as its basis. The original design called for a roof-mounted rack with two launcher tubes angled upward at about 30 degrees. This allowed the vehicle to be placed behind barriers or inside entrenchments and the missile would pop up above it to clear the barrier. Aiming was accomplished either by the remote sight or one permanently mounted on an extension on top of the vehicle that also cleared any fortifications in front. The launchers were mounted on a hinge at the rear that allowed them to be lowered for reloading. It swung through an angle of 45 degrees so the front was pointed slightly downward when lowered to allow the loader easy access to the front of the tubes. On firing, the rocket exhaust was directed forward through the tube, thereby eliminating any danger to troops near the vehicle. The rocket blast proved so powerful that it sometimes damaged the control wires or the missile itself. In one test, a simulated hangfire caused a fire that continued burning for three minutes and was believed it would have burned through the launcher and into the vehicle had it not been put out by a fire crew. The forward-exhaust concept was abandoned and a new launcher with open ports at the end of each tube was adopted. On launch, the exhaust hit the rear section of the vehicle deck and was deflected and