Weapon File: Red Top

Final Red TopThe De Havilland Red Top was an infra-red guided air-to-air missile and was the successor to the earlier Firestreak. Often viewed as merely an upgraded Firestreak the Red Top is in fact a far more potent and mature weapon.

Development of Red Top began under the codename Blue Jay Mk.4 before being re-designated Firestreak IV for operational use. However, De Havilland argued that the changes to the weapon were so dramatic that a new name should be selected and therefore it was named Red Top to distinguish it from its forebear. Whereas the Firestreak looked like something out of a 1930s Flash Gordon serial the new missile was more modern yet menacing to look at. It was certainly larger being a noticeable 13cm longer and weighing an extra 40lbs and having redesigned wings of greater span but it was inside the weapon that made the greatest difference.

red topIn developing Red Top the De Havilland team completely reassessed the layout of the Firestreak. One of the more unusual decisions taken in building the original weapon was to place the warhead in the tail of the missile around the motor. Not only did this limit the size of the warhead but it also limited its effectiveness upon impact. In Red Top the warhead was placed behind the seeker assembly in the nose and consisted of 68lbs (compared to Firestreak’s 50lbs) of explosive triggered by a proximity detonator. Like Firestreak the new weapon was controlled by four guidance fins at the rear that gave it excellent agility.

Guidance for the weapon was provided by the Violet Banner infra-red seeker. For the early 1960s this was a very sophisticated scanner and was one of the first infra-red missiles to introduce a cooling system in the seeker head to improve the infra-red image of the target. In all infra-red guided missiles (and even infra-red cameras) background heat from inside the sensor such as that generated by the hot electronic equipment or the heat built up on the seeker’s window as a result of friction as the missile flies though the air can overpower the comparatively weak signal of the target. Cooling the seeker head therefore clears up the infra-red image of the target and dramatically increases sensitivity.

Red Top missileThis led to a general belief that Red Top was the world’s first all-aspect infra-red air-to-air missile however this is not entirely true. Red Top could only engage targets from the front that were travelling at supersonic speeds thanks to the target developing a rather large heat plume from its engines and the friction-heating of the fuselage at high speeds. For targets travelling at subsonic speed then a more traditional rear-hemisphere attack was required. An often cited problem with the seeker however was that cloud inhibited its effectiveness in tracking a target but it is important to note that this was a common problem with all infra-red weapons of the day. While this would potentially be a drawback fighting tactical aircraft at low to medium altitude it remained a very effective weapon intercepting high altitude bombers where there was little cloud. The seeker was aided by the launch aircraft’s own radar which can transmit the location of the target to the missile while its on the rail so that the seeker is looking directly at the target upon launch.

hawker_seavixenRed Top was cleared for service in 1964 and armed the RAF’s English Electric Lightning F.3/6 and the Royal Navy’s De Havilland Sea Vixen FAW.2 (right). While the Gloster Javelin was armed with the earlier Firestreak plans to equip it with Red Top were shelved due to the aircraft’s impending retirement. Of the two aircraft that carried Red Top operationally the Sea Vixen was arguably the better platform for the weapon having a second crewman who could plot and prosecute the target more efficiently without having to fly the aircraft as well. The Sea Vixen could carry up to four weapons whereas the Lightning could only carry two (theoretically the Lightning could carry four weapons but plans for additional weapons to be carried under the wing pylons for export aircraft never materialised).

Lightning Red TopHowever the Lightning’s own performance actually increased the performance envelope of the missile. When flying at speeds in excess of Mach.1 at the Lightning’s service ceiling of 54,000ft the Red Top could generate enough energy to reach an altitude in excess of 70,000ft. The Lightning’s supersonic speed also increased range and reports from testing claim the weapon flying out to a head-on target range of 7-8 miles (when in the chase position this range will decrease as the target is moving away and so the weapon has to overtake it). Carrying the quite heavy weapon did impose restrictions on the light and aerodynamically pure Lightning and pilot notes for the Lightning F.6 model dictated that whilst armed the aircraft should not fly passed Mach 1.75 so as to not overstress the airframe.

Any infra-red air-to-air missile developed in the 1960s will ultimately be compared to the US AIM-9 Sidewinder family. Compared to the AIM-9B Sidewinder, Red Top was a far superior weapon with a more sophisticated seeker, longer range, greater agility and a substantially more powerful warhead. The AIM-9B also had a very limiting launch load factor of just 2.6G whereas Red Top could be fired at up to 4G making Red Top the better weapon in a dogfight. The only real advantage the AIM-9B had was that it was much lighter weighing just 180lbs compared to Red Top which weighed in at nearly 340lbs and could be more easily integrated on to a wider array of aircraft. This latter fact was the key to its export success compared to most other air-to-air weapons of the era including Firestreak and Red Top. When you consider that the primary Soviet close-in air-to-air missile for the 1960s and 70s was the AA-2 “Atoll”, a reverse engineered AIM-9B, then it can be claimed that Red Top was better than this weapon also.

Red Top & AIM-9B SidewinderThe AIM-9B’s extremely poor showing over Vietnam forced rapid development of an improved model, the AIM-9D Sidewinder and this had advantages and disadvantages when compared to Red Top. The AIM-9D had a marginally longer head-on range compared to Red Top again dependant on the conditions at launch. Red Top still had the more sensitive seeker and its larger window gave it a better view of the world outside. Also Red Top’s larger warhead meant that it was more likely to destroy whatever it hit or inflict fatal damage with a proximity hit. It’s interesting to note however that when the Royal Navy selected McDonnell Douglas’ F-4 Phantom II in its Anglicized F-4K Phantom FG.1 form both Red Top and AIM-9D were tested against each other. The Admiralty decided to keep the AIM-9D as the aircraft’s primary close-in weapon despite Red Top already being supported in service with the Sea Vixen. The main reason cited for this was to simplify the introduction of the already overly complex British Phantom to squadron service.

Consequently, Red Top was withdrawn from Royal Navy service in 1972 when the Sea Vixens were retired leaving the Sidewinder armed Phantoms as the Fleet Air Arm’s primary fighter. Red Top continued to arm the RAF’s Lightnings until 1988 and in July of that year the very last live round was fired over Cardigan Bay, South Wales (see top image).

  • Wingspan : 0.91 metres (2.95ft)
  • Length : 3.32 metres (10.89ft)
  • Body Diameter : 0.23 metres (0.75ft)
  • Weight : 154 kilograms (340lbs)
  • Warhead : 31 kg (68.3 lb)
  • Speed : Mach 3.2 (2436 mph)
  • Range : 7.5 miles
  • Service Ceiling : 70,000+
  • Launch Load Factor : 4G
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De Havilland Hornet F.3 vs. Dornier Do.335A-1 Pfeil

Battle of the Super Twins

Do355 De Havilland Hornet

Twin engine fighter designs met with mixed success during the Second World War. Some, like the P-38 Lightning or Bristol Beaufighter met with considerable success. Others however such as the Messerschmitt Bf110 or Westland Whirlwind didn’t enjoy as much at least in the daylight role. The concept was not lost entirely on aircraft manufacturers however who realized that in order to be successful against single engine types a twin engine fighter needed to be as light as possible or fitted with two powerful enough engines to compensate for the extra weight. The advantages to twin engine fighters was enough to spur this development. Twin engine fighters could carry more fuel making them excellent escort aircraft for bombers. They could also carry heavier armament and have radar installed for a night fighter capability.

Towards the end of the war the single engine types such as the Spitfire, P-51 Mustang and Fw190 were still the rulers of the sky but a steady stream of new twin engine fighters had started to make their mark also. In the UK the De Havilland Mosquito had proven a superlative weapon being able to adapt to numerous roles and excelling in nearly all of them. Encouraged by this success the engineers at De Havilland took the basic design and scaled down the fuselage in to an even lighter and more streamlined design for use by a single pilot and this produced the De Havilland Hornet fighter.

In Germany they had taken an entirely different approach however. As early as 1938 German engineers had realized that one of the biggest problems encountered by twin engine types was the increased drag from having the two engines on the wings and the weight penalty this incurred on agility. They therefore began experimenting with mounting the first engine in the forward fuselage and a second engine in the rear of the fuselage turning a pusher propeller. This had the advantage of creating a much more streamlined aircraft that had the power of a twin engine fighter but with the aerodynamic efficiency of a single engine type. Bizarrely, the German Air Ministry initially insisted this configuration be developed in to a bomber first but the project eventually collapsed before being revised again late in the war with the need for a new twin engine fighter. Fortunately for allied bomber crews the resulting Dornier Do.335A-1 Pfeil never entered service before the war ended.

For this comparison I am looking at the Hornet Mk.III (Hornet F.3) compared to the Do 335A-1 Pfeil. Neither of these aircraft reached frontline service before VE-Day and therefore it is a fair comparison of what they could have achieved against each other in combat. One important thing to note is that the Do 335A-1 was not as developed as the Hornet and therefore we can’t claim for certain that how the aircraft appeared in 1945 is not necessarily how the production version would have appeared. That being said the early plans for the Do 335A-1 were in this configuration so it is possible that this is how it would have gone in to combat at least initially.

Performance

DH 103 Hornet

The De Havilland Hornet was powered by a pair of Rolls-Royce Merlin 130 12-cylinder inline engines mounted in pods on the wings. These developed an impressive 2,080hp each and this hurtled the Hornet to a speed of 472mph at 22,000ft but this began to drop off considerably around the 30,000ft mark it reaching a speed in the region 340mph and further still when it reached its service ceiling of 35,000ft. These figures would be improved in later variants.

do335a-1

The Do 335A-1 was powered by two of the proven Daimler Benz DB-603A-2 inverted-V engines producing 1,750hp each; 3,500hp in total. The DB-600 series of engines, like the Rolls-Royce Merlin family for the Allies, were the engines that took the Luftwaffe fighter force through the war. They were tough, reliable and generally considered to be superior to the equivalent Merlin variant except in the later stages of the war when Allied engine technology caught up. These engines took the Do 335A-1 to a very respectable 478 mph at 28,000 feet in tests; something that most single seat fighters struggled to achieve even in 1945. The aircraft had a service ceiling of 37,400ft and could climb to its normal operating height of 26,000ft in just under 14 ½ minutes.

Armament

Hispano

The De Havilland Hornet was armed with a quartet of 20mm Hispano cannons mounted in the forward fuselage. This arrangement was becoming standard practice for RAF fighters as it provided the best balance of hitting power and weight considerations on the aircraft. These offered an effective rate of fire of 6-700 rounds a minute with a muzzle velocity of around 860m/s which was enough tear a Messerschmitt Bf109F in half. Ground attack ordinance covered a wide array of bombs and unguided rockets. Up to two 1,000lb bombs could be carried on hardpoints under the wing. Alternatively, eight 60lb RP-3 rockets could be carried which was reported to give aircraft like the Hornet the same firepower as the broadside of a battleship armed with 5.5inch guns.

MG120

The Do 335-A1 sported a powerful MK-103 30mm cannon firing through the spinner of the forward propeller in a configuration proven by both the Bf109 and the Fw190 albeit with smaller calibre weapons to suit their size. The explosive warhead of this shell could inflict very heavy damage on an enemy aircraft and was optimized for bringing down the B-17 Flying Fortress and B-24 Liberator quickly before their defensive guns could be brought to bear on the attacking aircraft. It was capable of firing up to 380 rounds a minute and was ideal for quick slasher attacks on bombers. This weapon was backed up by a pair of 20mm MG151/20 cannons(see above image)mounted in the forward engine cowl. This was one of the great air-to-air weapons of World War II and saw use on a variety of aircraft ranging from the Bf109 to the Me262 jet fighter. Depending on the type of shell being fired the weapon had a rate of fire between 600 and 750 rounds a minute and was the weapon of choice for engaging enemy fighters. For a projected ground attack role the Do-335A-1 was able to carry up to 1,000lbs of ground attack ordinance.

Manoeuvrability

DH 103 Hornet2

The Hornet suffered from the same problem that all multi-engined aircraft that house their engines on the wings suffer; heavy rotational inertia. In layman’s terms this is having to overcome the weight of the engines being mounted further away from the aircraft’s centre of gravity than on an equivalent single engine type to such an extent that roll rate falls off substantially. To reduce this as much as possible designers tried to place their engines as close to the fuselage as possible but in piston engine aircraft this was made difficult by the diameter of the propeller. Thanks to the unique construction methods employed by De Havilland, namely of the balsa-ply configuration, the aircraft remained very light despite its size compared to single seat types and with its two Rolls-Royce Merlin engines it achieved 400hp per ton.

do335 3

The disadvantages of having its two engines mounted in pods on the wings was totally negated by the Do335A-1. It therefore enjoyed a high rate of roll, superior to that of the Hornet and other similarly configured twin engine types, but the weight of the second engine in the tail slowed it down in the latitudinal plane particularly when in the nose down attitude when the aircraft was working against its lift forces to achieve flight. It was still a heavy aircraft and its two engines developed approximately 363hp per ton.

Misc

Hornet

Without question the Hornet pilot enjoyed one of the best views out of the cockpit compared to many other types thanks to its teardrop shaped canopy. As proven by its Mosquito forebear it was also relatively easy to produce compared to all-metal fighters thanks to its wood-based construction of the fuselage and wings. This also made repairing it considerably easier.

do335 2

The Do.335A-1 pilot had a much poorer view from his cockpit than the Hornet and many contemporary fighters. This was especially true in the aft most quadrants and was largely a result of the positioning of the rear engine and fuel tanks. This would probably have been addressed in later models but the urgency with which the aircraft was needed meant that it work had to go ahead with getting the aircraft in to service. Construction of the Do335A-1 was no easy feat as there had been no other aircraft like it before and so converting existing production facilities to accommodate the new type was wrought with difficulty. This was made immeasurably worse by destruction of many of those facilities by allied bombing raids.

Conclusion

The Hornet was an exceptional aircraft and proved most adept at the ground attack role (ironically the original role envisioned for the Do335) but in the air the Dornier “wonder weapon” was the superior aircraft enjoying a higher speed at altitude and a superior roll rate. It’s worth noting that the differences between the two aircraft’s performances are of a similar percentage to those between the Supermarine Spitfire V and the Focke Wulf Fw190A and in that instance the Fw190A’s advantages inflicted a heavy toll on the Spitfire V. Therefore there is the highest probability that in combat with one another the Do335A-1 would better the Hornet.

do335 4

The Hornet had the bigger punch however thanks to its four 20mm guns which when total firepower is considered out-punched the Do335A-1’s mixed calibre arrangement. Also the close coupling of all the Hornet’s guns made training them all on to a single target significantly easier as opposed to the cowl and spinner mounted weapons of the Do335A-1. The Hornet pilot also had superior vision which was crucial in a dogfight.

There is one final note worth mentioning about the differing configurations of these two aircraft. The Do335A-1’s inline arrangement of its two radial engines meant that an attacking enemy fighter could lay down a stream of bullets along the fuselage and potentially knock out both engines in a single pass especially in an attack from the forward hemisphere. The Hornet on the other hand with its two engines mounted much wider apart would be a much more difficult aircraft to knock out in a single pass.