Since well before heavier than air flight was even possible, parasite aircraft have held a curious attraction. There is something compelling about the idea of a smaller flying machine being launched from a larger one, even more so if that aircraft can be recovered too. Parasite aircraft sometimes make a good deal of sense but on the whole their disadvantages outweigh any practical benefit to be had from parasitism. Here are the best of this scarce but brilliant breed.
11. Bristol Scout and Felixstowe Porte Baby
This massive flying boat designed by John Cyril Porte and named with lazy irony ‘Baby’ was designed and used as a maritime patrol aircraft. First flown in late 1915, 11 were built and remained in service until the armistice in 1918, a remarkable longevity of service for an aircraft of this generation. For its entire operational life the Baby was the largest flying boat built in the UK. The appearance of the Baby also happened to coincide with the high point of the Zeppelin raids on Britain. This bombing campaign inspired an almost hysterical response, not least because there was simply no effective defence in 1916 and the enormous airships seemed to be able to operate over Britain with impunity.
One of the many schemes proposed to counter the Zeppelin menace was to mount a small fighter aircraft onto the long-ranged Baby which would then patrol over the North Sea, east of the British Isles. If a Zeppelin were encountered, the fighter would be released to effect an interception and then fly back to land if near enough or ditch in the sea. The flying boat could then pick up the (hopefully) victorious pilot and everyone would fly back for tea and medals. Thus the prototype Porte Baby was modified as the mothership for a standard Bristol Scout. Fairly obscure history was made when Bristol Scout number 3028 piloted by Flight Lieutenant MJ Day successfully separated in flight from the Baby (flown on this momentous occasion by Porte himself) at a height of 1000 feet over Felixstowe. Despite the project ultimately going nowhere, the Admiralty deciding (prophetically) that it was too clumsy and dangerous to pursue further, the Bristol Scout had become the first parasite aircraft in history.
10. Messerschmitt Me 328 and Dornier Do 217
Given the somewhat fantastical nature of the parasite fighter as a concept, it should come as no surprise that Nazi Germany (ever willing to try something crazy) spent a lot of money and time on the idea. It should also come as no surprise that the German entry in this select field was ill-conceived, dangerous, built on the cheap, and ultimately contributed nothing to the German war effort. It all started in the standard fashion, massive Luftwaffe bombers were being designed and an effective means of defence for them was sought. The idea that they could take along their own escort fighter was an attractive one. Messerschmitt started work on such a design in 1941, envisioning an aircraft towed aloft by an He 177 or Ju 388 on the end of a flexibly-mounted rigid bar, or carried on the back of their own giant Me 264 bomber. From the outset the concept was muddled, both a fighter (Me 328A) and bomber (Me 328B) were proposed and the emphasis of development would flit back and forth between the two, before all manner of different schemes of varying levels of impracticality would be proposed. None came to fruition.
Despite being regarded as a semi-disposable aeroplane, the Me 328 as it emerged was impressive on paper: costing about a quarter of the price of a conventional fighter such as the Fw 190, it was intended to have a top speed of around 500 mph. The fighter version was to be armed with two 20-mm cannon. As a bomber the aircraft was intended to be flown to the East coast of the US and then released to deliver a 500 kg bomb at a speed rendering it effectively beyond interception. The pilot was to ditch at sea and be rescued by a U-boat. Construction was mostly of wood but the most radical aspect of the design was its engines – the Me 328 was to be powered by two Argus pulse jets, identical to those that powered the V-1 flying bomb. Ultimately it would be the engines that doomed the programme.
It started well enough though, two prototypes were built and glider flights were made from a Do 217 carrier aircraft. In unpowered flight the aircraft was promising and seven powered prototypes were built. Unfortunately the pulse jets caused such appalling vibration (as well as being deafeningly loud) that the Me 328 was virtually uncontrollable. The pulse jets were tried fitted to the rear fuselage and under the wings but nothing could stop the shakes, there is an unconfirmed report that one of the prototypes actually vibrated itself apart in flight. Whether or not that actually happened, flights ceased and the programme was effectively over by mid 1944.
Despite the fact that the aircraft was totally unsatisfactory, the Me 328 popped up in countless other proposals right up to the end of hostilities. Me 328s were envisioned to be fired from rails and fired from U-boats and used as a suicide weapon (probably – it is unclear if the pilot was definitely intended to die, it would have been exceptionally difficult to get out). The proposed Me 328C was to be powered by a turbojet which should have cured the vibrations but construction never began.
9. Mcdonnell XF-85 Goblin and Boeing B-29 Superfortress
In the Convair B-36 the USAF had a bomber of hitherto unprecedented size. Impressive though it undoubtedly was, doubts were tacitly admitted as to its ability to defend itself even with the prodigious armament of sixteen 20-mm cannon lavishly distributed amongst nose and tail turrets along with six remotely controlled retractable turrets. The B-36 was possessed of such enormous range that a conventional escort fighter would be impractical, however taking along a parasite fighter to chase off any hostile aircraft impertinent enough to attempt an interception was an entirely different matter. Hence the existence of the XF-85 Goblin, by a considerable margin the smallest jet fighter ever to fly.
Opinions were, and remain, divided as to the practicality of the F-85/B-36 combination. Designed by a team led by Herman D. Barkey, who would later oversee the development of McDonnell’s slightly more successful F-4 Phantom, the tiny McDonnell, despite its comical appearance, was an extremely well executed response to the parasite requirement. Nonetheless its ability to adequately defend its mothership, or even itself, is open to question. The cuddly Goblin first flew some eight months after the rather more imposing MiG-15 and although the XF-85 apparently handled well, its projected top speed was slower than the Soviet aircraft (and the projection turned out to be rather optimistic) and it was armed with a mere four .50 cal machine guns. Furthermore, given that the Goblin’s dimensions were precisely tailored to the size of the B-36 bomb bay development potential was necessarily limited. Having said that, the Goblin’s projected performance was generally up to the standards of the day and the USAF was very keen on the parasite fighter. It was planned at one stage for every tenth B-36 to be a dedicated fighter carrier with provision for three or four Goblins although all B-36s would have the provision to carry at least one.
In the absence of a B-36 with trapeze equipment fitted, initial flight tests were to be handled by a suitably modified B-29, nicknamed ‘Monstro’. After a few tests to check the flying characteristics of the combined B-29/XF-85 combination, the Goblin made its first free flight on 23rd August 1948. Released from 20,000 feet, test pilot Edwin Schoch flew the aircraft for about ten minutes before attempting to hook back on to the trapeze. This was expected to be the trickiest aspect of parasite fighter operation and so it proved. Turbulence around the underside of Monstro was more severe than expected and the tiny jet collided hard with the trapeze, smashing the canopy and tearing off Schoch’s oxygen mask and helmet. An observer on the B-29 saw the helmet fall away and thought it was Schoch’s head. He succeeded in landing the aircraft conventionally (with head still attached) though the XF-85 was damaged in the process and seven weeks would elapse while repairs and modifications took place.
Further attempts were a mixed bag. Schoch succeeded in engaging with the trapeze on the second free flight in October 1948. However when the definitive retractable hook was fitted, severe aerodynamic buffeting added to the difficulty of the hooking process. In seven flights the XF-85 managed to re-engage the trapeze on only three occasions. The last (unsuccessful) attempt was made by Schoch in April 1949 and ended with a landing on the skid at Muroc field. The tubby Goblin flew for a total of two hours 19 minutes during its short life and had proved that the concept was at least possible, though apparently difficult. To further muddy the waters, some years later no less a personage than Chuck Yeager stated that he thought the XF-85 a good idea and that the reason for its failure was the lack of flying skill of Edwin Schoch. However poor Schoch was unable to answer this accusation having been killed in a flying accident in 1951. To be fair, over the years Yeager seems to have had an extremely poor opinion of virtually everyone’s flying skill except his own.
McDonnell proposed a swathe of changes to improve the ability of the aircraft to engage the trapeze, most significantly a telescopic trapeze structure extending beyond the turbulent air below the carrier aircraft. But it was not to be, Air Force command, under pressure to curtail spending (as usual), cancelled the XF-85 project citing its relatively modest performance and the high level of pilot skill required to reattach the aircraft to its carrier. This was the end for the egg-like Goblin but did not spell the end of USAF interest in other parasite aircraft, as we shall see…
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8. Scaled Composites SpaceShipOne and White Knight
Winner of the $10 million Ansari X prize for for the first non-governmental organisation to launch a reusable crewed spacecraft into space twice within two weeks, SpaceShipOne achieved its design goals in a mere six powered flights. The project was first considered in 1994 and schemed by Burt Rutan at Scaled Composites, the announcement of the Ansari prize the following year adding impetus to its development. However it should be noted that although it did indeed win the $10 million, the whole program cost about $25 million. The project would never have seen the light of day of it weren’t for the support of billionaire and aviation enthusiast Paul Allen who completely funded the project.
Rutan has a history of designing aircraft that feature unusual structures or layouts and the White Knight/SpaceShipOne was no exception. The twin booms, high engine placement, and flattened ‘W’ shape of White Knight are all features epitomising it for its role as a mothership. So far, so strange looking but the real icing on the cake is its crazed forward fuselage design sporting a profusion of small circular windows scattered seemingly at random around its nose. The same forward fuselage design with 16 portholes is shared by both aircraft. The small, thick windows are arranged so as to give a clear view of the horizon in all of the standard flight attitudes and were as large as engineers would allow for the immense pressure differences they would need to handle at the edge of space. This makes perfect sense for SpaceShipOne but why apply the same configuration to White Knight? The answer is twofold, firstly replicating the forward fuselage for both aircraft helped keep costs down. But intriguingly the second reason is that White Knight was designed as a ‘flying simulator’ to act as a training vehicle for SpaceShipOne pilots and be able to mimic the flight characteristics of the spaceplane. The cockpits of the two aircraft are basically identical. Of the tiny windows Doug Shane, the project’s operations director and one of its four test pilots said that “While it’s certainly not the best visibility of any airplane, it’s more than adequate”
SpaceShipOne seems to have a more conventional layout than White Knight but it has one particular trick that is not at first apparent in the form of its ability to ‘feather’. This entails the entire rear section of the aircraft swinging upwards, transforming it into an aerodynamically stable shape with very high drag. As such it descends relatively slowly back down to Earth after its short sharp Mach 3 scramble up and out of the atmosphere. Despite the high ground speed, indicated airspeed never exceeds about 270 knots due to the very thin air at the altitudes it travels through – topping out at the Kármán line, internationally regarded as the edge of space, which equates to an altitude of 100 km (or 328000 ft, reflected in SpaceShipOne’s N328KF registration). Perhaps surprisingly, given the nature of most 21st century craft, the spaceplane is manually controlled and there is no autopilot. “If you get in there and do a half-assed job, you’ll go to only 200,000 feet.” said Mike Melvill, one of the other test pilots and the first to take SpaceShipOne to the 100 km design altitude on July 21st 2004.
Ultimately SpaceShipOne first achieved its goal and won the prize on October 4th 2004 in the hands of Brian Binnie. further flights were planned but Rutan made the decision not to risk the craft now that it had made history and all future flights were cancelled. SpaceShipOne now resides at the Smithsonian Institute’s National Air and Space Museum in Washington, D.C. and is currently displayed with the Bell X-1 and Linbergh’s transatlantic Ryan NYP. Meanwhile White Knight was utilised as a carrier aircraft for drop tests of Boeing’s unmanned X-37 spaceplane. In 2014 White Knight flew for the last time, to Everett field and retirement as part of Paul Allen’s Flying Heritage Collection. Since then a developed version designed for six passengers and two crew, the imaginatively named SpaceShipTwo, carried by White Knight Two, has been developed. The first example tragically broke up killing one of its two crew in 2014. A second example is undergoing testing at the time of writing.
7. Short Mayo Composite: Short S.20 ‘Mercury’ and S.21 ‘Maia’
Throughout the 1930s, the Atlantic mesmerised airlines. A potentially exceptionally lucrative market, it was known that it could be crossed since 1919, Lindbergh emphatically reinforcing the point in 1927 but it remained tantalising just out of reach, in a practical sense at least, until the very last weeks before war erupted in September 1939. The big problem was that the amount of fuel required to get an aircraft from London to New York for example, was so great that the aircraft could carry no passengers or cargo. In the absence of a suitable aircraft, means were sought to cheat the problem. Imperial Airways spent a great deal of time and effort developing in-flight refuelling (with some success) but also pinned their hopes on parasitism, with this: the Short Mayo Composite.
To be strictly accurate of course, two commercial aircraft had crossed the Atlantic several times with fare-paying passengers aboard in the form of the Graf Zeppelin and Hindenburg. The latter’s fiery demise rather put people off the prospect of crossing the Atlantic suspended under a massive inflammable gasbag however and emphasis shifted to making the journey in a conventional heavier-than-air machine. Lacking an aircraft with sufficient endurance, Robert Mayo, Imperial Airways’ Technical General Manager proposed a system wherein a small, long-range seaplane on top of a larger carrier aircraft, using the combined power of both to bring the smaller aircraft to operational height, at which time the two aircraft would separate, the carrier aircraft returning to base while the other flew on to its destination. The upper component aircraft was not intended to carry passengers but air mail.
The aircraft that emerged was undeniably spectacular, consisting of a fairly heavily modified Short C-Class ‘Empire’ flying boat named ‘Maia’ and designated S.21, and a totally new design, the Short S.20 named ‘Mercury’, the messenger of the Gods – though its not clear that the Romans had the delivery of air mail in mind for him originally. Maia flew first in July 1937 with Mercury following it into the air a couple of months later. The connecting mechanism was ingenious, allowing for limited movement of both components relative to each other. When release was imminent, the flying trim of Mercury could be checked before the pilots released one lock each. The final lock holding the craft together was automatic, releasing Mercury when it achieved 3000 pounds-force (13 Kn). This meant that Mercury was effectively straining upwards and the effect was that on release Maia would tend to drop away whilst Mercury climbed sharply, minimising any chance of collision. The first separation was achieved in February 1938. This was followed up by the first transatlantic flight on July 21st. After the Composite took off from Southampton, Mercury was released over Shannon in Ireland and continued alone to Boucherville, near Montreal in Canada. This represented the first commercial crossing of the Atlantic by a heavier-than-air aircraft. This was followed up by a record-breaking flight of 6,045 miles (9,728 km) from Dundee in Scotland to Alexander Bay in South Africa, between 6 and 8 October 1938. This remains the longest flight ever achieved by a seaplane.
Ultimately aircraft development caught up with the Mayo composite. Although it achieved its design goal with aplomb, it seemed an excessively complicated way to carry 1000 lbs of mail to America. A year to the day after Mercury’s transatlantic flight the Short S.26 G-Class flying boat flew for the first time. The G-Class had non-stop transatlantic ability effectively rendering the Mayo concept obsolete at a stroke. One month later in August 1939 Imperial Airways began a scheduled transatlantic mail service, utilising a regular C-Class flying boat, refuelled in flight to enable it to make the crossing non-stop. Sadly the outbreak of war prevented the G-Class ever seeing service on its designed route and caused the air-refuelled service to cease less than a month after it began. Maia was destroyed by German bombers in Poole Harbour in May 1941 and Mercury was used by 320 Squadron RAF for a time before being broken up for scrap in August 1941. An ignominious end for a briefly glorious seaplane.
6. Rockwell International Space Shuttle Orbiter and Boeing 747 SCA
Taking parasitism to a new level, the world’s first flying spaceship needed to be tested before being fired into the cosmos. Furthermore since the very beginnings of the project it was known that the shuttle orbiter would have to be ferried from airbase to airbase. Initially the specification required for conventional air-breathing engines to allow the shuttle to fly under its own power in the atmosphere. Unfortunately this was problematic, the orbiter was roughly the same size as a DC-9 but over twice the weight and much less aerodynamic yet could carry far less fuel. With five engines (as opposed to a DC-9’s two) the maximum ferry range considered possible by a self-propelled orbiter was 500 miles, which was not acceptable. An alternative system was sought and coincidentally Robert Salkeld of the System Development Corporation was making presentations around this time on the subject of air-launched fully-reusable spacecraft during which he would show images of the aforementioned Short Mayo composite as an example of a large two-stage aircraft. Nasa had made thousands of unpowered landings with F-104s, and later the X-15 and the Northrop lifting body aircraft, which demonstrated that repeated, accurate landings from high altitude in fast aircraft with small wings were relatively simple. A series of tests with a Convair 990 and B-52 proved that dead stick landings in large aircraft were not only adequately safe and controllable but arguably easier than conventional approaches: on one occasion a Nasa pilot who had never flown a multi-engine aircraft before successfully landed a B-52 unpowered – when tasked with landing the aircraft in a standard shallow-angle powered approach he was unable to do so.
And so it was decided that the Shuttle Orbiter would glide to landing. To ferry and test the spacecraft a carrier aircraft would be required, Nasa toyed with the idea of a new build aircraft (John Conroy of ‘Guppy’ fame proposed an enormous twin fuselage monster of an aircraft bearing a distinct resemblance to Paul Allen’s Stratolaunch) but time and budgetary considerations compelled Nasa to seek an off-the-peg solution. Only two contenders were seriously considered, the Lockheed C-5 Galaxy and the Boeing 747. The choice fell on the latter after it was discovered in wind tunnel tests that if the C-5 pilot failed to execute the separation manoeuvre perfectly, the Orbiter would tear the tail off the aircraft. As a T-tailed design that would effectively mean the loss of the airframe (and likely the crew as well) as all the rear control surfaces would be removed. The aerodynamics of the 747 naturally aided separation, and even if the worst happened, the 747’s horizontal tail surfaces would be unaffected and the aircraft was known to remain controllable even with a substantial chunk of vertical tail missing.
First flight of the combined 747 and Orbiter took place in February 1977, with the first in-flight separation taking place six months later. This was Space Shuttle Enterprise (OV-101), built purely for atmospheric test and never fitted with engines or a functional heat shield. Five free flights were made from the 747 carrier aircraft followed by many, many captive trips. Since the retirement of the shuttle, Nasa’s shuttle carriers found themselves without a purpose – though N905NA was utilised on one occasion to ferry Boeing’s Phantom Ray UCAV from St. Louis, Missouri, to Edwards Airbase. Both are now retired and preserved.
5. Leduc 0.10/0.21 and Sud-Est Languedouc/AAS.01
After the war the French aviation industry worked incredibly hard in an ultimately successful attempt to drag itself back up to world standard. There was no shortage of crazy French research types throughout the late forties and fifties, now mostly obscure outside of francophone aviation enthusiast circles. One of the most impressive and successful was the Leduc series of ramjet aircraft. Ramjets are fascinating engines, so simple that they contain no moving parts, yet efficient at supersonic speeds up to about Mach 4. Unfortunately they won’t work at all at standstill and produce negligible thrust until about half the speed of sound. Any ramjet powered flying machine is therefore a great contender to be a parasite aircraft and construction of a French ramjet powered aircraft with a top speed of Mach 0.85 (about 650 mph or 1000 km/h) had begun as early as 1937(!). Amazingly the semi-completed ramjet was kept secret at the Breguet factory and escaped the notice of the German occupiers throughout the war. Work resumed on the radical aircraft in 1945.
The aircraft was the brainchild of René Leduc, an engineer whose background was in thermodynamics rather than aviation. Leduc worked for the Breguet aircraft company in the 1920s and whilst here he began to consider alternative forms of power to the standard piston engine and propellor arrangement of all aircraft up to that point. In 1930 he attempted to patent a pulse jet only to find it had already been invented. The same thing happened again when he tried to patent the ramjet in 1933 but found that it had been proposed by Rene Lorin in 1913. However, although he hadn’t been the first to invent the ramjet, Leduc was the first person to actually build and demonstrate a working ramjet engine in 1936. This was sufficiently impressive for a scaled up version to be commissioned to power a manned aircraft, the Leduc 0.10, and after the drawn out construction period necessitated by the small matter of a world war, all was ready for the first powered flight in 1947.
First powered flight occurred on 21st April 1949 over Toulouse. On that occasion the mothership was the remarkable AAS.01, this being in actual fact a prototype of a four-engined derivative of the wartime Heinkel He 177, originally designated He 274. Two prototypes of the He 274 were built by Breguet during the war and were ready for flight testing as Allied forces approached. The order was given by the German authorities to destroy the new aircraft to prevent them falling into enemy hands, however this order was carried out in a less than enthused fashion and both prototypes survived with only minor damage. After the war both were completed to flying status and saw extensive service on various research programmes.
Initial flight tests were encouraging, the Leduc 0.10 flew at 420 mph on its first flight and subsequent tests eventually saw it attain Mach 0.85 which was pretty hot stuff for 1949. The two original Leduc 0.10s (a third was built somewhat later) were not the first ramjet powered aircraft to fly, but they were the first manned aircraft wherein a ramjet was the sole means of propulsion. After this proof of concept, Leduc shifted his attention to the Leduc 0.21, essentially similar to its predecessor but scaled up by around 30%, with tip tanks added to the wings. The new aircraft was still air launched and completed a detailed flight test programme from 1953 to 1956 to develop an automated control system for the ramjet. A total of 284 free flights was made during which the 0.21 reached a top speed of Mach 0.95.
Buoyed by the relative success of his ramjets so far Leduc moved on to the next version, the 0.22. The air-launched Leducs were purely research aircraft but the end result was always intended to be an interceptor. This time the aircraft was not a parasite. It was equipped with a regular turbojet and could take off conventionally and accelerate to a speed whereby the ramjet could function. Unfortunately, although designed for Mach 2, the Leduc had not been area-ruled and was subject to so much transonic drag that it was unable to break the sound barrier. This setback could probably have been overcome with a redesign but the Leduc was cancelled as part of a swathe of government cuts to French aviation projects. French hopes were pinned on the Dassault Mirage III instead – probably correctly as it turned out given the immense success of that aircraft. With no state funding Leduc was forced to wind up the aviation side of his business but happily Rene Leduc’s company is still in operation today producing hydraulic equipment.
4. Project Tip Tow, Tom-Tom, and FICON: Republic F-84 and Boeing B-29/Convair B-36
After the less than stellar experience gleaned with the XF-85 Goblin parasite fighter one might have assumed the USAF would avoid flirting with further unconventional parasite projects but the concept persisted. Attention shifted from the purpose-built tiny aircraft that could be wholly contained within the fuselage of the carrier aircraft to some means of bringing a conventional fighter aircraft along for the ride.
The focus of initial development was on wingtips. German engineer Dr Richard Vogt had come up with the concept of increasing range by connecting two aircraft at the wingtip and experiments in support of this had been conducted in Germany on two light aircraft during the war. Having emigrated to the US under the auspices of Operation Paperclip Vogt’s concept of wingtip towing provoked interest, initially in the concept of a manned light aircraft acting as a fuel tank for the larger aircraft. Experiments began with a C-47 and a Culver PQ-14, the two aircraft were not able to engage or disengage but were attached by a leather strap that was slack for take off and landing allowing the two aircraft to fly in formation. At altitude the strap was winched in by the C-47 until the wingtips abutted.
Meanwhile it was realised that as well as a fuel tank the wingtip towing system might work with an escort fighter that could attach or detach at will. The B-29 and F-84 were selected as the obvious choices for this application but as no studies had been done on the feasibility of the system the USAF returned to the C-47/PQ-14 pairing for further experiment. In the course of tests flown in 1949 it was found that the little Culver could indeed dock and undock from the C-47’s wingtip but that it was not easy at first. Vortices around the wingtip of the larger aircraft were difficult to overcome and once attached the pull on the Culver’s wingtip constantly tried to roll the aircraft over. Test pilot ‘Bud’ Anderson found he could counteract the rolling tendency by using the elevators (somewhat counter-intuitively) but the rolling issue was a harbinger of things to come. Despite early difficulties Anderson found that with practice coupling and uncoupling the aircraft could be achieved relatively easily, even at night. Not everyone had the same experience, of the nine pilots who ultimately flew these tests, two were unable to achieve contact.
Experience garnered from these experiments suggested that a F-84 Thunderjet/B-29 Superfortress combination was potentially practical. Flight test of suitably modified F-84s and B-29 began in 1950 codenamed Project MX-1016 but more commonly known as Tip-Tow. From the outset this was a more difficult prospect than hooking up the little Culver to a C-47. Wingtip vortices were more severe and the wing of the B-29 proved considerably more flexible than the C-47. Nevertheless, hook-ups and disconnections were demonstrated, first with one fighter and then with a pair, the first hookup of both F-84s with the Superfortress occurred on 15th September 1950.
The pilots of the F-84s found that they could shut off their engines and restart in flight and the whole concept appeared to be feasible, subject to overcoming some teething issues. Chief amongst these was that, just like the Culver attached to the C-47, the Thunderjet pilots had to continually control their aircraft in the tow to prevent them rolling over onto the Superfortress. Republic Aircraft developed an automatic control system to prevent this which was in testing by March 1953. On 24 April 1953, the left-hand F-84 hooked up and the automatic system was switched on. The F-84 immediately flipped over onto the wing of the B-29 and both crashed with loss of all five B-29 crew and the F-84 pilot. The pilot of the right-hand F-84 of the bomber was Bud Anderson but he was able to pull up and away from both aircraft. This accident effectively ended Project MX-1016 but it did not quite spell the end for the wingtip attachment concept.
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The USAF had expended time, effort and lives but the B-36 was still just as vulnerable as when they had started and a different parasite concept was now proposed. If the large and slow B-36 were vulnerable, why not have not have it carry a small, fast aircraft to the vicinity of the target and have that deliver a tactical nuclear weapon while the big B-36 aircraft loitered safely out of range of any air defences? This concept came to be known as FICON for FIghter-CONveyor. Once again the F-84 was chosen as the parasite, an F-84E was modified with a nose hook and a B-36 was fitted with a trapeze. Initial tests, once again flown by Bud Anderson, proved that the concept was workable but the F-84, most of which stuck out below the carrier plane, was causing too much drag and compromising range capability. The decision was made to switch to the swept-wing F-84F and to get more of the new aircraft to fit into the bomb bay its tailplane was given extreme anhedral. At the nose the aircraft received the all important hook to achieve recovery. It was a tight squeeze – once loaded into the bomb bay of the B-36 there was only 6 inches of ground clearance and the parasite’s external fuel tank (or atomic weapon).
Although a possible nuclear strike role remained as an option for the combination, the primary role for the aircraft was now seen as strategic reconnaissance. During 1953, whilst the new parasite was being prepared, the original F-84E and B-36 combination flew simulated reconnaissance missions against Air Force Base targets in the US. USAF fighters were only able to intercept the ‘hostile’ aircraft on two out of six missions and it was concluded that the FICON system had a good chance of successfully penetrating the air defence network of the Soviet Union. The success of these missions and the suspicion that the B-52 (which had first flown in 1952) would soon render the system obsolete added an urgency to the programme and developmental flying continued apace. The ubiquitous Bud Anderson flew the first trapeze tests with a swept wing F-84 and Republic built 25 production RF-84Ks specifically for the FICON role. On December 7th 1955 the first operational hook-ups of B-36 with parasite RF-84K fighters was achieved. Capt. Bobby Mitchell took off in his RF-84K from Larson AFB and rendezvoused with Maj. Clyde Perry’s crew in their GRB-36D bomber. Mitchell flew his Thunderflash onto the trapeze and Lt. O.C. Rutter raised the RF-84K into the bomb bay. Once safely stowed with the bomb bay doors closed up against the fighter’s fuselage, Mitchell climbed out to greet Rutter. After a cup of coffee with the crew, Mitchell climbed back into his fighter, was lowered, restarted his engines and flew off. A couple of hours later, Lt. Walter Rudd became the second parasite pilot to hook up and detach. Before releasing the second fighter, the GRB-36D made a low pass over Larson AFB and Maj. Oscar L. Fitzhenry, the 348th BS operations officer, was quoted as saying, “Results proved to be above and beyond our greatest expectations.” Perhaps. In reality hookups with the carrier aircraft proved challenging for experienced test pilots under ideal conditions. In combat or in adverse weather, by regular service pilots, they proved extremely difficult and several RF-84Ks were damaged attempting the manoeuvre. Operations were maintained for a year or so but the success of both air-refuelled B-52s and the U-2 in the nuclear strike and reconnaissance roles respectively doomed the obsolescent B-36 and FICON was consigned to history.
Bizarrely, whilst FICON development was in full swing, it was decided to have a look at wingtip-towing again. One of the FICON B-36s was suitably modified for towing swept wing RF-84Fs using a claw system. As before, wingtip vortices made hooking up difficult and the procedure was just as problematic as ever. Eventually on September 23rd 1956 test pilot Beryl Erickson made contact with the wing tip of the JRB-36F with a small angle of yaw. Immediately, his Thunderflash started to pitch up and down violently. There was no emergency method to sever the connection between the aircraft, so the RF-84F ultimately tore the wingtip clean off the larger aircraft, part of the JRB-36F scissors mechanism remaining firmly clamped in the jaws of the Thunderflash’s claw. No one was hurt but this incident predictably ended Project Tom-Tom flight tests.
3. Curtiss F9C Sparrowhawk and USS Macon and Akron
The US Navy stuck with the large rigid airship as a potential instrument of war long after other major powers had abandoned these giants as impractical and dangerous. At least, as the world’s sole major producer of helium, the American airships were an order of magnitude less flammable than their European equivalents. The fantastic endurance possible with a large airship operating in a scouting role was attractive but the vulnerability of such a massive and relatively slow vehicle could not be overlooked. It was schemed that the airship would not directly reconnoitre anything of interest but stand off at a safe distance and despatch conventional aircraft to investigate more closely. Following successful trials with a Vought UO-1 and the Zeppelin-built USS Los Angeles, the trapeze system for launching and recovering aircraft in flight was fitted to the Navy’s two newest dirigibles USS Akron and the slightly later Macon. The aircraft ultimately employed for the task, the Curtiss F9C, was a pre-existing design that Curtiss had developed in response to a requirement for a lightweight carrier fighter. The original requirement was abandoned, though the Curtiss had been adjudged the best of the three designs submitted for test and thus when the new requirement for a similar aircraft for airship use came about, with an emphasis (for obvious reasons) on small size and low weight, the Curtiss fighter fitted the bill more or less off-the-shelf. Or at least up to a point, the F9C was advanced in that it was Curtiss’s first aircraft to feature a metal monocoque fuselage as well as stamped aluminium wing ribs but it was hardly suited for the observation role it was ostensibly tasked with. The pilot had a hell of a lot to keep him occupied, ‘normal’ 1930s reconnaissance aircraft took along a second crewman as an observer and operate the radio but no room for him in the Sparrowhawk. The tiny cockpit had nowhere convenient to put the radio morse key, and where it ended up made its use awkward. There was no room at all for the navigation/scouting board, so it was mounted on the control column. Interestingly the F9C retained its carrier capability, an arrestor hook could be fitted and on at least one occasion the Sparrowhawks flew down from their unique aerial aircraft carrier to land on the conventional nautical aircraft carrier USS Lexington. Ultimately eight would be built including two prototypes. All would see service from the flying aircraft carriers, with brief but considerable success.
First of the dirigibles to fly in September 1931 was USS Akron which could carry three of the diminutive parasite Sparrowhawks. As first flown however, neither Akron’s trapeze system nor her aircraft were ready and it would be a full seven months before she could boast her full complement of scouting aircraft and the crew to fly them. By then the necessity for her aircraft had became painfully obvious. In January 1932 Akron failed to find an “enemy” flotilla during an exercise, embarrassingly (though unsurprisingly perhaps) the massive airship was herself spotted by two destroyers within the force she was unable to find. The first F9C hooked on to Akron’s trapeze in May 1932 but she was again aircraft-less when she participated in June’s Pacific fleet exercises. Akron at least managed to sight the ships she was scouting for this time but was immediately intercepted by 13 carrier aircraft. Her commander Charles E Rosendahl gamely stating that it was “perfectly apparent” the Sparrowhawks would have fended off their attackers had they been aboard. Over the next few months launching and recovery operations from Akron’s trapeze were perfected but time was not on their side as Akron was lost in a thunderstorm less than a year later on April 3 1933. Tragically only three men survived from the crew of 84.
Barely a fortnight later USS Macon emerged from her hangar for the first time. Modified with experience gained from the Akron she was a notably more successful ship capable of carrying five Sparrowhawks as opposed to the earlier airship’s three. Over the next two years the Macon and her Sparrowhawks would be kept busy, developing the art of operating from the trapeze and eventually becoming a well-honed and efficient scouting platform. In the course of these operations it was realised that the aircraft did not require their landing gear so it was removed and replaced with an external fuel tank, allowing a 30% increase in range. Her greatest moment occurred in July 1934 when Lieutenant Commander Herbert Wiley, one of the three survivors of the Akron crash, took the Macon on an unauthorised jaunt to show his superiors what she was capable of. Wiley knew that President Franklin Roosevelt was due to be travelling from Panama to Hawaii aboard the heavy cruiser Houston with a second cruiser as escort. With nothing more than newspaper reports to go on, he calculated an intercept course from Moffett Field, California (named incidentally, after Admiral Moffett who had lost his life in the Akron disaster) based on his estimate of the Houston’s course and speed and set off to prove the value of the airship as a strategic scouting platform. At 10am the next day Wiley believed they should be at the correct position to effect an interception and launched two Sparrowhawks. Sure enough, just before noon, the aircraft found the President’s ships.
On board the Houston, confusion reigned as to where these small aircraft had come from as all US carriers were known to be in the Atlantic at that time. Confusion briefly turned to fear as some observers mistook the Sparrowhawk’s belly fuel tank for a bomb. But more knowledgeable heads pointed out the telltale ‘skyhooks’ mounted on the top wings of the mystery aircraft. After returning to the Macon, the Sparrowhawks flew low over the Houston and dropped the latest newspapers from San Fransisco as well as stamps franked with a special Macon cachet – Wiley knew Roosevelt was an avid stamp collector. “The president compliments you and your planes on your fine performance and excellent navigation” radioed the Houston. Navy top brass were less thrilled by Wiley’s failure to reveal the true nature of the trip and the fact that Macon had been out of communication for many hours. Disciplinary action was threatened but ultimately called off, allegedly after the intervention of Roosevelt himself. Buoyed by his success, Wiley was eager for the Fleet manoeuvres set for Spring 1935, training in air operations had been intense and the Macon was now fitted with a radio homing beacon allowing the Sparrowhawks to return to the airship no matter what course they or it followed after launch. This feature made it the first, and to date only, genuinely effective airborne aircraft carrier. It was arguably the finest very-long-range airborne early warning system of the pre-radar age and Wiley was keen to prove his ship’s true worth.
However it wasn’t to be, the Macon had suffered damage in severe turbulence over Texas in April 1934. Temporary repairs had been made but never completed and when she was caught in gusty conditions over the Pacific in February 1935 an ill-defined report of damage in the area where the repairs had not been completed led Wiley to order ballast to be dropped and the engines throttled to idle. Either too much ballast was dropped or the engines were delayed in idling as the Macon shot up above her ‘pressure height’ (the altitude at which the gasbags start to automatically vent helium through emergency valves to prevent from rupturing). She remained above pressure height for a full sixteen minutes, venting helium until the inevitable happened – too much gas was lost to sustain flight and the huge Macon plunged, relatively slowly, but uncontrollably, into the water, taking four Sparrowhawks with her. Lessons had been learned since the loss of the Akron, Macon carried lifejackets and rafts both of which had been absent from Akron, and only two of the 83 men on board lost their lives. Herbert Wiley had now survived the loss of both the US Navy’s most advanced airships. Sadly, there was no longer an appetite to replace such a costly behemoth as the USS Macon and the world’s only flying aircraft carrier was consigned to history.
2. North American X-15 and Boeing NB-52
Most of the US X-planes were parasites and the most exciting of the lot was the X-15. Back in 1947, Chuck Yeager flew the X-1 past the speed of sound and into the history books. Back then Yeager had the luxury of being able to hang out in the relative comfort of the B-29 mothership until they were high enough to begin his flight, then he just had to climb into the X-1, close the door and whizz off into the wild blue yonder. Ten years and 3000 mph later the X-15 was too big to be crammed into a fuselage, even in the cavernous bomb bay of a Stratofortress. The X-15 pilot had to sit in his restrictive pressure suit in the tiny cockpit of the X-15, slung under the wing of the NB-52, from before take off all the way up to release altitude.
The X-15 flights may have taken place over fifty years ago but they are still incredible. In 199 flights over just under ten years it repeatedly exceeded height and speed records and remains the fastest manned aircraft ever flown (Mach 6.7 which equates to 4520 mph (7274 km/h) or a shade over 2 km per second). On two occasions it exceeded the Kármán line, 100 km up, and as such is generally considered to have entered outer space. The NB-52 that launched nearly all these tests was possessed of some interesting superlatives too. NB-52 ‘Balls 8’ was built in 1955 as an RB-52 reconnaissance model and was acquired by NASA in 1959 specifically for X-15 mothership use. Fitted with a pylon between the fuselage and engine pod, Balls 8 was subsequently employed on many other projects, particular highlights being the hypersonic X-43, various lifting bodies such as the X-24 and Pegasus, a rocket capable of taking a payload from the NB-52 to low Earth orbit. Balls 8 was eventually retired on 17 December 2004 (101 years to the day after the Wright Brothers’s first flight) at which point it was the oldest active B-52 in service and the only active B-52 still flying that wasn’t an H model. Somewhat counterintuitively it also had the lowest total airframe time of any operational B-52. It is now on public display at Edwards AFB.
The X-15 programme was extremely successful and unusually safe considering the extreme nature of the flight regime it was exploring. But there were accidents, one X-15 broke its back on landing, another rolled on landing, leading to crushed vertebrae for its pilot John McKay. Worst of all was Flight 191. Due to the aircraft yawing in the extremely thin air at 266,000 feet (82 km), the X-15 ended up entering denser air at lower altitudes whilst at right angles to its direction of flight. At 230,000 feet the aircraft entered a Mach 5 spin. Despite managing to recover from the spin at 118,000 ft pilot Michael Adams found himself hurtling downwards, upside down, at over four times the speed of sound. It should have been a relatively simple matter for Adams to roll the aircraft back to normal and effect a landing but a fault in the X-15s control system led to the aircraft pitching up and down wildly, pulling 15G with each oscillation. The aircraft disintegrated 10 minutes, 35 seconds after launch, killing Adams.
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The accident completely changed the attitude of both the Air force and NASA to the X-15 and despite both parties agreeing to finance further tests throughout 1968, only another eight flights would be made. The potential benefits of X-15 flights were no longer considered worth the high cost and considerable risk and the final flight was made by Bill Dana in October 1968. Thus ended the flying career of the most spectacular parasite aircraft in history. Never again would a research aircraft be this thrilling.
1. ‘Звено’ SPB: Polikarpov I-16 and Tupolev TB-3
In July 1941 an oil depot in the Romanian town of Constanţa was dive-bombed by Polikarpov I-16s. Not in itself, one would think, a particularly surprising act given that the war on the Russian Front had begun in the previous month. However this particular raid caused considerable confusion amongst the Germans and Romanians who witnessed it. Constanţa was well beyond the range of a Polikarpov I-16, let alone one loaded down with bombs, so where had these fighters come from?
The answer of course was that they had been carried there under the wings of a mothership. They were the parasitic attacking component of the ‘Sostavnoi Pikiruyuschiy Bombardirovschik’ (‘Combined Dive Bomber’), and were the ultimate expression of a concept called the ‘Zveno’ (‘Link’) or ‘Aviamatka’ (Aerial Mothership). The Zveno was the brainchild of Vladimir Vakhmistrov, engineer and occasional test pilot of the Soviet Air force test institute (the NII VVS). He had worked on the concept for a decade before the beginning of hostilities and now was its time to shine.
Vakhmistrov had specified four potential applications for his Zveno concept, the delivery of fighters beyond their conventional range, providing bombers with escort fighters all the way to and from the target, the ability to equip fighter-bombers with heavier bombs than they would be able to take off with on their own, and the simple expedient of using the added thrust of parasite aircraft to get a heavily laden bomber into the air. Initial experiments involved a twin engine TB-1 bomber and two I-4 parasol monoplane fighters. The I-4 was normally a biplane but for Zveno use the bottom wing was removed in order to clear the TB-1’s propellors, with apparently no discernible change in performance or handling. First flight of this combination ‘Zveno-1’ occurred 3 December 1931 with the I-4s piloted by A. F. Anisimov and a pre-fame Valery Chkalov, who would later attain something akin to superstardom for his test piloting exploits in the mid-thirties. Vakhmistrov himself directed proceedings from the front turret of the bomber. An error in the sequence of releasing the parasites by the bomber crew resulted in one of the fighters prematurely separating and the other remained firmly locked to the wing. However the TB-1 and attached I-4 remained in controlled flight and the second fighter was soon released without further incident. Later, release control would be handled by the pilots of the parasites, normal procedure being to release the tail lock first so that the aircraft came under the control of the pilot, then pull back on the stick to separate completely from the TB-1.
With the concept proved to be workable, Vakhmistrov set about testing various combinations of aircraft and theorising operational uses for his Zveno. Early experimentation was largely concerned with discerning which aircraft types were best suited to the system and maximising the amount of aircraft that could be connected. A TB-1 with the somewhat more potent Polikarpov I-5 as the parasites flew in 1933 designated Zveno-1a. More radical was Zveno-2 which added a third I-5 over the fuselage, this time to a four engine Tupolev TB-3. As with Zveno-1, the addition of the extra thrust of the added aircraft more than overcame any drag or weight penalties they incurred and performance was actually enhanced over a conventional TB-3. Fitting the I-5s to the wings was a relatively simple affair utilising ramps and muscle power but attaching the central Polikarpov onto its mounting was an order of magnitude more difficult. Rather than going through the rigmarole of getting it into position the I-5 was just locked in place, acting as a fifth engine for the TB-1. Eventually the wings and tail were removed and the Polikarpov fuselage acted solely as an engine nacelle, albeit one with a ‘pilot’ on board to operate the engine controls.
Zveno-3 reversed the overwing approach taken so far and fitted two parasites under the wings of the TB-3, these being Grigorovich I-Z monoplanes. The I-Z was itself an interesting design in its own right, being a fighter fitted with two single-shot 76.2-mm (3 inch) recoilless cannon though these were removed for the Zveno trials. Despite being a monoplane, the fixed undercarriage I-Z possessed extremely limited ground clearance under the wing of the TB-3. This problem led to an unfortunately cumbersome system of operation wherein the wheels of the parasites and TB-3 all rested on the ground – the parasite mounting permitted vertical movement of the two underwing fighters relative to the TB-3 so that they could roll over uneven ground on take off. Once airborne, the parasites were to lock their respective mountings in a fixed position for flight; if the parasites were not rigid in flight, the bomber became extremely difficult to control. This unfortunately led to the only serious accident of the whole Zveno project when I-Z pilot Korotkov incorrectly timed the locking manoeuvre, broke the docking frame and crashed into the underside of the TB-3’s wing. As the bomber came in for an emergency landing with both fighters still attached, the slow landing speed of the TB-3 fell below the stalling speed of the I-Z, which fell away, killing Korotkov.
This accident was in contrast to the general success of the Zvenos so far and Vakhmistrov started looking at the possibility of re-docking the parasites in flight. It was felt that turbulence above the mothership would probably be severe and that a ventral trapeze would be the best approach for attempting the first in-flight attachment. This time the position of the trapeze precluded a conjoined take off so the two aircraft flew to altitude separately. On 23 March 1935, the TB-3 and I-Z performed the world’s first mid-air docking between two fixed wing aircraft to become Zveno-5.
Attention had now shifted to an exciting new fighter, the Polikarpov I-16. The world’s first low-wing, retractable undercarriage, cantilever monoplane fighter was somewhat beyond the state-of-the-art in military aircraft design of the early thirties. One feature in particular lent itself to Zveno use: retractable undercarriage. When mounted under the wings of the TB-3 with gear up, the I-16 offered sufficient ground clearance to do away with the unwieldy attachment of the I-Zs. Vakhmistrov set to immediately with Zveno-6 which mounted two I-16s under the wings. Despite the groundwork of Zveno-5, these were not able to reattach in flight but the developed Zveno-6 featured a retractable trapeze under each wing onto which the I-16s could attach or detach at will. The procedure, whilst demonstrated to be possible, was deemed too difficult for service use however.
Final fling of Vakhmistrov’s pre-war experiments was the ‘Aviamatka’ which appeared in public carrying five parasites, the lower component of which could attach or detach at will. Vakhmistrov’s plan was for one TB-3 to be accompanied by eight I-16 parasites as a form of long-range airborne patrol craft. The parasites would never all hook on at once but rotate, attaching or detaching as required. They could also take on fuel from the mothership. Although some tests were carried out in support of this concept, including in flight fuel transfer, the full eight-parasite composite never saw the light of day. The Aviamatka was seen as simply too cumbersome to be effective. Despite this, interest in a simpler twin-parasite I-16 carrier to function as a composite bomber continued, especially from the Navy. Ultimately only six operational Zveno-SPB’s comprising six TB-3s with twelve I-16s were delivered, forming the 2nd ‘Special’ Squadron attached to the 32nd IAP (Fighter Regiment) of the 62nd Aviation Brigade of the Black Sea Fleet. They were stationed in Crimea.
In the opening stages of the Great Patriotic War, the Black Sea Fleet Air Force was tasked with destroying industrial targets in Romania. The most important of these was the King Carol I bridge over the Danube which carried the Ploiești-Constanţa oil pipeline from the oilfield at Ploiești and was critical for the Axis war effort. After several attempts to destroy the heavily defended bridge with conventional bombers, the target was given to the Zveno-SPB squadron though as a combat test, it was decided to attack the oil depot first. On 26th July 1941, two Zveno-SPB aircraft performed a textbook attack on the depot in daylight with no losses. The fighters disconnected 40 km (25 miles) from the target and returned home under their own power. After this convincing demonstration, two raids on the bridge were flown, on the first the parasites successfully dive-bombed from an altitude of 1800 m (5,900 ft) and again returned home with no losses despite heavy anti-aircraft fire. The second raid took place on the 13th August 1941. Three Zveno-SPBs approached the target and the six fighters scored five direct hits on the bridge, completely destroying one of its spans. On the way back, the fighters strafed Romanian infantry and once again suffered no losses.
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It is not known how many missions were flown in total but it was probably around 30. As well as severing the oil pipeline, Zveno-SPBs were responsible for destroying a dry dock in Constanţa and a bridge across the Dnieper. This garnered some attention at high level as Soviet forces in general (and the air force in particular) were on the back foot in the first months following the launch of Operation Barbarossa. The main obstacle to getting more Zvenos into the air was the lack of TB-3s available fitted with the Mikulin AM-34FRN engine, variants with other motors not being sufficiently powerful to carry the bombed up I-16s. Admiral Kuznetsov asked Stalin for additional AM-34FRN-engined TB-3s from the Air Force so they could be converted to Zveno-SPB carriers but the request was denied. Aircraft losses were so great at this early stage of the war that the Air Force needed every conventional aircraft it could lay its hands on. The success of the Zveno-SPBs was acknowledged but it was undeniably a complex system and seen as a luxury the Soviets could ill-afford at this stage in the war. Operations continued into 1942 but by then it was becoming apparent that both the I-16 and especially the lumbering TB-3 were too vulnerable in the face of German numerical and technical air superiority and the briefly effective fighting career of Vakhmistrov’s incredible creation was over.
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Fairchild AU-23A Armed Pilatus Turbo-Porter 72-3 Janes – Sufficient put into service to not be relevant.
*Pave Coin Beech A36 Bonanza Janes 72-3. Other aircraft included the Piper PE1 Enforcer (turbine Mustang) – Janes 81-2, AU-23 and 24 (above), Cessna O-1, U-17 and O-2 and Cessna A-37.
SAAB-MFI-17 (only 300kg external load capability) 72-3 Janes
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