29 December 2010

The Chrysler SERV: Thinking Out of the Box for Space Travel

Chrysler SERV ascends on its aerospike engine
By the late 1960s, the groundwork was being laid down that would eventually evolve in the Shuttle Transportation System that today is in the twilight of its career. The NASA-led studies that involved the major aerospace contractors of the day was divided into "phases" and at each phase candidate contractors had to demonstrate their concepts to the Manned Spacecraft Center (MSC) at the Johnson Space Center outside of Houston. Apollo was run out of the NASA headquarters in Washington, but the technical reach of a reusable spacecraft meant that NASA wanted the program leadership to be at a field center run by engineers- and at the time, only Houston and the Marshall Space Flight Center (MSFC) in Huntsville, Alabama, had the technical expertise for such an undertaking. Not wanting to put its eggs in one basket, though, NASA established on 6 July 1970 the Alternate Space Shuttle Concepts (ASCC) study to evaluate alternative concepts and proposals to what was already under development in cooperation with the aerospace industry and the MSC in Houston. Given that the MSC had it hands full, program leadership of the ASCC was assigned to the MSFC in Huntsville. Over 29 configurations were studied and millions in funding were provided. A joint submission by Grumman/Boeing was evaluated, along with one from Lockheed and one from Chrysler, which at the time had a thriving space division that had been in business since 1962 building the first stages for the Saturn I rocket and Saturn IB rocket. Chrysler's ASSC proposal was the recipient of a $1.9 million study contract for what has to be one of the most unorthodox if not outright unique space shuttle concepts ever taken seriously by NASA. 

Schematic diagram of the Chrysler SERV
Chrysler's design was called the SERV- Single-stage Earth-orbital Reusable Vehicle- and it looked like nothing else under study at the time. It was a large conical vehicle that looked like a supersized Apollo command module. It was 65 feet high and 90 feet in diameter with a central payload bay 23 feet wide and 60 feet long. Liquid hydrogen and liquid oxygen tanks then surrounded the payload bay to fill the rest of the volume of the SERV. Its propulsion engine was highly innovative and developed with assistance from Rocketdyne- the SERV had a 12-module liquid oxygen/liquid hydrogen aerospike engine integral to the base of the SERV that was 87.4 feet in diameter and just over 8 feet long. The engine developed an astounding 5.4 million pounds of thrust (by comparison, each Space Shuttle Main Engine develops about 400,000 lbs of thrust at launch). Each of the 12 modules were interconnected and each had a set of turbine driven fuel pumps that could run as high as 120% to compensate for the failure of any pair of pumps in the 12 modules. The engines designed were so powerful, that the SERV's aerospike had to be throttled back to 20% just before reaching "max-Q"- the point of highest aerodynamic stress to prevent overstressing the SERV during its ascent to orbit. A series of doors could close over the aerospike modules to protect them during re-entry. 

SERV with the MURP spaceplane. Note the doors for the jet engines.
At launch, the SERV weighed in at approximately 4.5 million lbs and different modules could be attached to the top of the SERV- the most studied were an external extension to the payload bay and the other was what was called the MURP- Manned Upper Reusable Payload, which was a small orbiter design with flick-out wings on return to Earth. The MURP could carry up to ten astronauts. Launches would have taken place from large concrete pads as the SERV had its own landing legs to support its weight. To return to the Earth, the SERV would re-enter the same way as the Apollo command module did, with the blunt end first and protected by thermal tiles. But instead of a water landing, at an altitude of 25,000 feet, a set of intakes and exhaust ports opened and four banks of seven jet engines (that's right, twenty eight engines!) powered by JP-4 fuel would start up and provide deceleration and maneuver capability that would bring the SERV back home for a soft landing on its own landing legs. The planned landing site for the SERV would have been on the skid strip at Cape Canaveral adjacent to the Kennedy Space Center. 

Chrysler's space division would have built the SERV at the Michoud facility that today has been responsible for the Space Shuttle's external tank. A specially-modified transport ship would then take the completed SERV to the Kennedy Space Center. Chrysler estimated that each SERV would cost $350 million each. However, by the time the ASCC studies were winding down, the Chrysler SERV got little attention as the design submissions from Lockheed and Grumman/Boeing were decidedly much more "conventional" than the SERV- but the SERV is a fascinating exercise in aerospace development when preconceived notions are cast aside and an innovative solution is found to meet an exacting set of requirements! 

Source: Space Shuttle: The History of the National Space Transportation System- The First 100 Missions by Dennis R. Jenkins. Specialty Press, 2001, p123-125.

28 December 2010

The Rocket-Boosted P-51 Mustang

In September 1944 the first operational unit of Messerschmitt Me 262 jet fighters was established under the command of the celebrated ace Major Walter Nowotny of the Luftwaffe, his unit being tasked with the operational development of tactics for the fighter and being named "Komando Nowotny" in honor of that significance. USAAF heavy bomber crews had ready been encountering the Me 163 Komet rocket interceptor for several months but the persistence of the jet over the point-defense nature of the Komet made the 262 a more significant threat in the eyes of the Allies. After Nowotny was killed in combat in November 1944, the unit became Jagdgeschwader 7 (JG 7), the first operational jet fighter unit in history. However a threat that the Me 262 posed in the threat, it was quickly realized that it was most vulnerable during its landing and takeoff phases of flight as early jet engines of the day suffered from long spool up times. If American fighter pilots could get at the 262 at its home bases, then its speed advantage was negated. 

The distinctively marked Fw 190 D-9s of JV 44
In response, not only did the Luftwaffe bases of the 262 boast more robust air defenses in the form of anti-aircraft artillery, German fighter pilot Adolf Galland's fighter unit, Jadverband 44 (JV 44) had also come up with another tactic to defend the 262s. At the time, Galland had become a very vocal critic of the Luftwaffe's tactics and operational decisions to the point of becoming quite the thorn in the side of Hermann Goering, the head of the Luftwaffe. It was thought by Goering and his command staff that if Galland were given front line command of a unit, he might be killed in action which would get him out of their hair. Galland was tasked to gather the best fighter pilots he could find to operate the 262 as JV 44 was formed in February 1945. To deal with marauding American fighters over their bases, one of Galland's men formed what was called the Platzschutzstaffel (airfield protection squadron). Equipped with Focke Wulf Fw 190 "Dora 9s" which had excellent performance at low to medium altitudes, the Dora 9s were painted with a distinctive red/white stripped pattern on the underside of the fuselage so they could be recognized and not fired up on by the anti-aircraft artillery of JV 44's base. Each time Galland sent up 262s on an intercept mission or 262s were recovering at the base, the distinctively-marked Dora 9s were airborne. 

Ground testing the Aerojet rocket-equipped P-51D
Fighting past the the Platzschutzstaffel's combat air patrols wasn't the most ideal situation as American fighter pilots also had to deal with the AAA. With the first American jet fighters still a ways from operational employment, various methods were considered to deal with the Me 262 jet menace. One of the few concepts that did make it to the flight test stage was a rocket-boosed North American P-51D Mustang. With an approximately 100mph speed advantage over the Mustang, it was felt that a rocket booster of some sort could bring the P-51D a burst of speed that would allow it to battle the Me 262 at altitude instead of over the Luftwaffe's home fields. Tail number 44-73099 was pulled from the production line for modification with an Aerojet liquid rocket engine installed in the lower aft fuselage just behind the radiator and ahead of the tailwheel. The rocket engine used two hypergolic fuels- red fumaric acid and aniline with the fumaric acid acting as the oxidizer. Both were extremely toxic and corrosive and each was housed in a pressurized, 75-gallon tank, one under each wing and much smaller than the standard Mustang drop tank. 

With the lower aft fuselage painted with a reflective material to prevent heat damage from the rocket engine, all the pilot had to do was flip a simple off/on switch on the left side of the cockpit to activate the rocket engine. North American test pilot Bob Chilton took the modified Mustang to the air for the first time on 23 April 1945 and at 21,000 feet, he fired the rocket engine and the Mustang surged forward another 100mph. The two 75-gallon tanks were sufficient for one minute of operation. Several test flight were made, but the underwing tanks, even though smaller than the standard fuel drop tank, induced a considerable amount of drag that prevented the rocket-boosted Mustang from really getting the most out of that one minute of rocket-boosted flight. By the time the USAAF took delivery of the 44-73099, the Germans had surrendered unconditionally and the operational need for the rocket boosted Mustang faded into aviation history. 

27 December 2010

Enjoy the Holidays!

I don't have much in terms of blog postings this week as I'm currently on vacation in the Washington DC area visiting family and of course engaging in as much avgeekery as possible with a visit today to the National Air and Space Museum (my last time here was back in 2007) and if time allows, a repeat visit to Udvar-Hazy at Dulles. I neglected to have something posted for Christmas Day as last year I featured the Apollo 8 lunar mission and their now-famous reading of the opening of the Book of Genesis. This time I wanted to share a video created by long time friend Brian Wiklem of the Jet-X Millenium Series of diecast airliner models. Over the past several years when he was at the helm of Jet-X I had the distinct pleasure of creating some of the box artwork for his model releases. He created this video several years ago and even when it's not Christmas I enjoy watching it. 

The music is Jerry Goldsmith's soundtrack to the Disneyland California Adventure ride "Soarin' Over California". May all of my readers have a wonderful holiday season with their family and friends- I will endeavor to have perhaps one or two posts this week!

22 December 2010

How Aleksandr Yakovlev's Rivalry with Pavel Sukhoi Did Him In

Aleksandr Yakovlev
The 1950s and 1960s in Russian combat aircraft development were marked by intense rivalries between the various design bureau (OKBs) heads. Nowhere else was this seen than with the rivalries between the respective OKBs of Artem Mikoyan, Pavel Sukhoi, and Aleksandr Yakovlev. During the Second World War, Yakovlev's OKB was one of the dominant forces in Russian aviation, having built thousands of fighters for the Soviet air forces. OKB MiG (Mikoyan and his partner, Mikhail Gurevich) was rapidly rising to prominence during the war. OKB Sukhoi really didn't start to establish itself until well after the war (some say that Stalin had a dislike of Pavel Sukhoi as one reason). As the jet age dawned, Yakovlev took a conservative approach that saw the first Yak jet fighters as jet derivatives of his wartime piston engined designs whereas MiG and Sukhoi were willing to push the envelope and advance the state of the art. A rivalry between Sukhoi and Mikoyan developed with Mikoyan gaining the upper hand against both Yakovlev and Sukhoi with the MiG-15, MiG-17, and MiG-19 fighter designs which outclassed comparable aircraft from Yakovlev. When in the 1950s the Soviet military command wanted a supersonic interceptor, it was Sukhoi's delta winged Su-9 (NATO code name Fishpot) that edged out Mikoyan's design based on an enlarged MiG-21 fighter. First flying in October 1957, the Fishpot was certainly fast, but it was handicapped by the poor reliability of its Lyulka AL-7F turbojet. In those days, it was rare for an AL-7F engine to last beyond 200 flight hours- and that's not time between overhauls, the reliability of the engine was so poor that few engine units lasted past 200 flight hours, an abysmal figure. The radar set in the conical shock cone of the nose inlet was limited as well. 

Sukhoi Su-9 "Fishpot"
Of course, having the Su-9 having much in common with the Su-7 (NATO code name Fitter) tactical fighter did make selecting the Su-9 for production much easier. But the Sukhoi OKB knew that the Soviet Air Defense Forces (PVO) was not pleased with the performance of the Su-9 and with only 924 examples built, an upgraded Su-11 was introduced. But it would be built in very limited numbers. At the time, the Soviet leadership had decreed that the "missile age" had made many aircraft designs obsolete, and like the infamous Duncan Sandys Defence White Paper in the UK that mortally wounded the British aerospace industry, numerous aircraft and engine projects were canceled and only those designs that were developments of existing designs were allowed to continue to develop. As the Yakovlev OKB had already in production the Yak-25/26 interceptor (NATO code name Flashlight) and attack variants, it proceeded with a supersonic design in the Yak-28 (the interceptor variant having the NATO code name Firebar and attack version being the Brewer). Three features made the Yak-28 more attactive than the Su-9/Su-11 family- first, it used the Tumansky R-11 turbojet was showing itself in the MiG-21 to be much more reliable and durable than the Lyulka AL-7F, secondly it had two engines which gave in a perception of safety over the single-engined Su-9/Su-11 family, and thirdly, having a nose free for a larger radar set than what was possible with the nose intake arrangement of the Sukhoi design meant that production was switched over to the Yak-28 instead, the interceptor version being the Yak-28P. 

Yakovlev Yak-28P "Firebar"
Sukhoi wasn't going to be one-upped by Yakovlev, though. Taking as a baseline the limitations of the Su-9/Su-11 family. OKB Sukhoi set about to create a vastly improved interceptor in the shape of of the Su-15 (NATO code name Flagon). The Su-15 was designed from the outset to be superior to the Yak-28P- it used two of the same Tumansky R-11 engines and used lateral box intakes to leave the nose section free for the same large radar set used on the Yak-28P, the Oryol-D radar. Being a development of the Su-9/Su-11 family, though, it managed to avoid cancellation like so many other projects in the 1958-1959 timeframe in the Soviet Union. Interestingly, the Yak-28P and the Su-15 were produced in the same factory- in the Soviet Union, the OKBs only did design and flight test work with workshops for building prototypes. The designs were then handed off to independent factories for production.  At the time, the Novosibirsk aircraft factory No. 153 was responsible for the Yak-28P production and it was assigned production of the Su-15 once it had passed its State acceptance trials in 1962. Given that both the Yak-28P and the Su-15 used the same powerplant and radar, producing both at the same plant made logistical sense. And there was irony in the decision as the same plant built the Su-9/Su-11 interceptors that were replaced in production at that very plant by the Yak-28P. And now the plant was gearing up to produce more Su-15s with the intent of replacing the Yak-28P with the PVO. 

The sole Yakovlev Yak-28-64 prototype
Not willing to lose out to Pavel Sukhoi, Aleksandr Yakovlev dispatched one of his sons to the Novosibirsk plant to learn as much as he could about the Su-15 design (Yakovlev had two sons who worked for him- one would end up designing the Yak-40/42 airliners and the other would be responsible for the Yak-52 trainer). Seeing the threat posed by the Sukhoi design to the Yak-28P, Yakovlev set about designing an upgraded version provisionally designated the Yak-28-64 (due to work on it beginning in 1964). Many of the features of the Su-15 were incorporated into the Yak-28-64, primarily in moving the Tumansky R-11 engines to the rear of the fuselage from the wings. One of the criticisms of the Yak-28P was that having wing-mounted engines gave the aircraft a poor rate of roll and adverse handing characteristics in an single engine-out situation. Moving the engines to the fuselage resolved these concerns. The tail unit and the wings remained close to that of the Yak-28 and the unique bicycle landing gear was retained. The single ventral fin of the Yak-28P was changed over to a twin ventral fin arrangement for stability. Given that OKB Yakovlev had little experience with fuselage-mounted lateral intakes, Yakovlev incorporated a copy of the Su-15's lateral box intake design on the Yak-28-64. 

The prototype Yak-28-64 was rolled out in 1966 and it proved in flight tests right off hand to be a dog. In fact, the Yak-28-64's performance was even worse than that of the Yak-28P, the very aircraft that was being superseded by the Su-15. Numerous unpleasant handling characteristics were also uncovered and some of the landing issues present in the Yak-28P thought to be cured in the Yak-28-64 persisted (such as aileron reversal at high speeds). It didn't take long to realize that the Yak-28-64 was a dead end and the project was abandoned by Yakovlev. 

Sukhoi Su-15 Flagon
A look at some of the production figures during this rivalry is telling. Just over 900 Sukhoi Su-9s were built at the Novosibirsk factory. Less than 100 Su-11s were built. Replaced in production at the factory by the Yakovlev Yak-28P, over 400 examples were built before it was completely supplanted by production of the Su-15, of which over 1,200 were built. The attack versions of the Yak-28 had to be continually upgraded with no less than 10 versions, each in relatively small production batches around 200 or so. Having been topped by Sukhoi in the interceptor arena with the Su-15, the Soviet air forces replaced the attack versions of the Yak-28 with another Sukhoi design, the Su-17/Su-22 family (NATO code name Fitter) which proved more reliable and versatile operationally. 

The Yak-28-64 and the rivalry with Pavel Sukhoi damaged OKB Yakovlev for good. His designs were considered by the Soviet air forces to be unreliable and obsolete, at the worst, limited in performance at best. For years no other Yakovlev combat aircraft design was taken seriously by the Soviet military high command and even the VTOL Yak-36 design was supremely limited in its utility. Even Yakovlev's submissions to the  competition that resulted in the MiG-29 Fulcrum and the Sukhoi Su-27 Flanker (Yak-45 and Yak-47, respectively) were decidedly archaic in appearance and failed to use some of the latest advances in aerodynamics. Most Yakovlev designs following the abandonment of the Yak-28-64 were either light aircraft or airliners, areas that were more heavily influenced by his sons than by Aleksandr Yakovlev himself. 

Source: OKB Yakovlev: A History of the Design Bureau and its Aircraft by Yefim Gordon. Midland/Ian Allan Publishing, 2005, p215-230. Additional material from Paul Martell-Mead at the Secret Projects forum. 

20 December 2010

Soviet Wild Weasels: Part Three (Missiles)

Kh-28 missile being loaded on Vietnamese Sukhoi fighter bombers
I briefly touched upon the subject of anti-radiation (or anti-radar) missiles in the previous blog post on the specialized aircraft designs that were developed in Russia as counterparts to the American Wild Weasels. Despite the introduction of nuclear weapons in Soviet suppression of enemy air defense (SEAD) doctrine in 1959, there were misgivings within the Soviet air forces on the effectiveness of nuclear weapons against targets like early warning radars and air defense sites. The first dedicated anti-radar missile (ARM) was the Kh-28 (NATO code name AS-9 Kyle), work on which began in 1963. Initially the Kh-28 was designed to be used by the proposed Yakovlev Yak-28N I mentioned in the previous blog post. Work on the Kh-28 by the Raduga design bureau proceeded in tandem with the much larger Kh-22 anti-shipping missile- in fact, in many aspects the Kh-28 is a scaled-down version of the larger Kh-22 that was carried only by bomber aircraft.

Like its larger sibling, the Kh-28 used a liquid propellant rocket engine as the technology of the day meant that solid rocket motors, while being easier to handle and employ, didn't have the range that was needed for the Kh-28, which was on the order of 75 miles, considerably more than any American ARM design at the time. Weighing approximately 1,500 lbs, the Kh-28 was not a light missile. When the Yak-28N was canceled in 1972, when the Kh-28 went into service, it was to be carried by the Sukhoi Su-17 Fitter fighter bombers, a single missile on the centerline station with an associated guidance pod carried on the right inboard wing pylon. The targeting system for the Kh-28 was tuned specifically to counter the American Nike-Hercules SAM radars and as well as the British Thunderbird and Bloodhound SAM radar systems. The first production versions of the Sukhoi Su-24 Fencer strike bomber also had provisions to carry the Kh-28 on one wing pylon and the associated guidance pod on the opposite wing pylon. Besides the liquid fuel handling issues, the main drawback of the Kh-28 was that it had to be preset to a given enemy radar frequency on the ground before the mission. Despite this, the Kh-28 remained in production until 1983 and was exported to several client states. 

Kh-25MP on a Sukhoi Su-17 Fitter
When the Soviet air forces introduced the Mikoyan MiG-27 Flogger strike derivative of the MiG-23 fighter, in th early 1970s, the Kh-28 was simply too large for the MiG-27 to carry. As a result, a smaller ARM had to be developed for use by the Flogger. The Kh-27 was developed by the Zvezda design bureau as a variant of the Kh-23 air-to-surface missile which had the NATO code name AS-7 Kerry. The Kh-23 was roughly in the same class as the American AGM-12 Bullpup missile. The Kh-27 homed in on enemy radar emissions like the Kh-28, but it featured a new solid rocket motor and an onboard autopilot that allowed it to be fired outside the radar range of its target. Being smaller in size, though, the Kh-27 had a much shorter range of approximately 30 miles, just a bit longer than its American contemporary, the AGM-45 Shrike. A MiG-27 carrying the Kh-27 needed a guidance and targeting pod to be carried as well. The Kh-27 entered service in 1977, but was limited in its deployment as it was rapidly superseded in front line service by the improved Kh-25. The numbering seems odd that a lower number is more advanced than the Kh-27, but the Kh-25 (NATO code name AS-10 Karen) is actually a family of missiles with different warheads and seeker heads that was developed from the Kh-23 family of missiles. In the Kh-25 family, the specific ARM variant is designated Kh-25MP which uses the same seeker head as the Kh-27. Both the MiG-27 Flogger and the Sukhoi Su-17 could carry and employ the Kh-25MP. Being a modular family, the Kh-25 family of missiles' closest counterpart in the West would be the AGM-65 Maverick, but having a longer range than the Maverick. The ARM version of the Kh-25, the Kh-25MP, has its own NATO code name, AS-12 Kegler.

Kh-58 on display in front of a Sukhoi Su-24 Fencer
Despite the tactical flexibility afforded by the more advanced Kh-27/Kh-25MP missile, there was still a need for a missile with the long range that the older generation Kh-28 possessed. The Raduga design bureau was asked again to develop a successor to the Kh-28 with the same range and performance but having more advanced features and more tactical flexibility. This missile became the Kh-58 (NATO code name AS-11 Kilter) which featured a solid rocket motor to dispense with the handling of corrosive fuels. It was a different design than what the Raduga OKB had been used to, most of its work on cruise missile type weapons, so the Kh-58 was its first design to have cruciform fins. Carried on a specialized pylon adapter that swings the missile downward and away from the launch aircraft before rocket ignition, the Kh-58 was introduced in 1982 just before the Kh-28 ended production. Designed from the outset to counter the radar systems of the Hawk and Patriot SAM missiles, the Kh-58 is a big missile weighing 1,400 lbs with a range of 75 miles. Its carrier aircraft include the MiG-25BM Wild Weasel variant of the Foxbat, the Su-22 Fitter, and the Su-24 Fencer. While the necessary equipment was internally carried on the MiG-25BM (mentioned in the previous blog post), both the Su-22 and the Su-24 needed an external guidance pod. On the Sukhoi Su-24 Fencer this is the Fantasmagoria pod that functions much like the HTS (HARM Targeting System) used on the Lockheed Martin F-16CJ variant of the Falcon. An improved version of the Kh-58 then followed that was designated Kh-58U and it possessed a remarkable range of 155 miles. The Kh-58's closest analog in the West is the Anglo French AS37 Martel missile, but with a much more impressive range than the Martel. 

Kh-31 test round on the intake pylon of an Su-27 Flanker

When the United States introduced the AGM-88 HARM (High-speed Anti-Radiation Missile), it was clear that American ARMS were gaining in parity with Soviet designs. The HARM had a speed well in excess of Mach 2 and a range greater than 60 miles. The response from the other side of the Iron Curtain came from the Zvezda design bureau which developed the Kh-31 (NATO code name AS-17 Krypton). The Kh-31 is a scaled-down derivative of the much larger P-270 Moskit ship-launched anti-ship missile (NATO code name SS-N-22 Sunburn). The Moskit was unique at the time in using a ramjet to sustain the rocket engine for long ranges at high speeds. the Kh-31 uses a similar ramjet system that acts as a solid rocket engine at ignition, then switches over to a ramjet once it reaches its high cruise speed of Mach 3.6! In fact, the design team for both missiles was the same. Weighing the same as the Kh-58 missile, the Kh-31 was much faster, more advanced and highly accurate. The Kh-31 entered service in 1988 with an anti-shipping variant becoming operational a year later that targeted the advanced AEGIS radar systems of US Navy surface combatants. Unlike previous Russian ARM designs, the Kh-31 is much more flexible and can be carried by nearly all of the tactical aircraft in Russian service from the MiG-29 Fulcrum, the Sukhoi Su-24 Fencer, and the entire Su-27/Su-30 Flanker family. China has a license built version of the Kh-31 that can be carried by its Su-30 Flankers and its Xian JH-7 strike fighters. The first versions delivered were designated KR-1 and were optimized against Taiwanese radar frequencies, but more recently a version of the Kh-31 with more Chinese-specific avionics has entered service as the YJ-91.

Interestingly, when the US Navy canceled its AQM-127 SLAT (Supersonic Low Altitude Target) in 1991, the remaining funds from the program were used in 1996 to purchase a small number of Kh-31s from Russia for use as MA-31 target drones. The missiles were delivered to Boeing lacking the warheads and military avionics and Boeing (back then the work was being done by McDonnell Douglas before it merged with Boeing) added the necessary equipment to convert it into a supersonic target drone. While a follow-on buy was planned, the MA-31 was really on an interim solution as it didn't meet the requirements fully that were laid down for the SLAT program. In 2000 Orbital Sciences was given the definitive contract for the GQM-163 Coyote target missile.

Sources: Soviet/Russian Aircraft Weapons Since World War II by Yefim Gordon, Midland Publishing 2005.  
Wild Weasel Fighter Attack: The Story of the Suppression of Enemy Air Defences by Thomas Withington. Pen and Sword Aviation, 2008

17 December 2010

Soviet Wild Weasels: Part Two (Aircraft)

Yakovlev Yak-28PP "Brewer-E"
Last night we took a look at the nuts and bolts of Soviet suppression of enemy air defenses (SEAD) doctrine and tactics. Tonight we'll continue along that them with a look at the aircraft that filled the role of  "Wild Weasels" in the Soviet air forces. Like the United States, the Russians had put into service several specialized aircraft that were used to knock out and/or jam enemy radars and surface-to-air missile sites. These aircraft were based upon established production types much in the same way the USAF Wild Weasels were adaptations of production fighter aircraft. The first aircraft to fill this role was the Yakovlev Yak-28N, an experimental adaptation of the Yak-28 "Brewer" attack aircraft. This version of the Brewer was the first Russian development for a Wild Weasel-class aircraft; work began by OKB Yakovlev in 1964-1965 with a production Yak-28I being set aside in 1965 for conversion to the -28N configuration. The attack Yak-28I had the "I" suffix as it was equipped with the Initsiativa-2 ground-mapping/bombing radar in a ventral radome aft of the nose gear. On the Yak-28N, the Initsiativa-2 radar was replaced by radar pulse detection unit that would seek out and locate enemy radar emissions and provide targeting data to Raduga Kh-28 (NATO code name AS-9 "Kyle") missiles, one each under the outer wings. The Kh-28, which I'll discuss in a subsequent post, was the first Russian anti-radiation missile to be fielded with the first operational examples coming out in 1964. 

By the time operational testing of the Yak-28N was completed around 1972, it had been far outclassed by contemporary Russian and American designs and the project was canceled. However, the work that had been put into the Yak-28N wasn't wasted as the Soviet air forces still needed a battlefield electronic warfare aircraft that better performance and was more flexible than the existing design in use, the Tupolev Tu-16PP Badger which clearly by 1972 was too big and too slow to survive in hostile airspace. The Yak-28 was again used as the basis for the Yak-28PP electronic warfare aircraft that crammed the jamming equipment of the Tu-16PP into a much smaller airframe. All of the armament provisions of the Yak-28 were deleted and four different jamming systems were installed in the Yak-28PP, which was marked by a number of dielectric bulges and blisters on the fuselage. The jamming systems generated so much heat that two heat exchangers were installed in the lower aft fuselage ahead of the aft bicycle gear to help cool the avionics. The outer wing pylons were fitted with rocket pods that fired chaff ahead of the aircraft to help sow chaff corridors to protect inbound strike packages. Below each engine nacelle of the Yak-28PP was a system for deploying bundles of fiberglass-based chaff strips in mass quantities. The role of the Yak-28PP was to accompany inbound strike packages with three of the ECM -28PPs sowing a chaff corridor on each side of the strike aircraft formation as well as using its powerful jamming equipment to blind NATO air defense radars. The first Yak-28PPs completed their State acceptance testing just as the Yak-28N was canceled. Most of the Yak-28PPs that were built (NATO code name "Brewer-E") were based with the Soviet forces in East Germany. 

MiG-25BM armed with Kh-58 missiles
The cancellation of the Yak-28N in 1972 came about due to the arrival of an aircraft with significantly higher performance that would become the first Russian production Wild Weasel-class aircraft, the Mikoyan MiG-25BM "Foxbat-F" based on the production interceptor version. It was recognized early on in the Foxbat's flight test program that a high-flying, high-speed aircraft would make an ideal SEAD aircraft- as it was proved itself immune to interception during operations over the Sinai prior to the Yom Kippur War, a SEAD Foxbat could out-fly defending fighters, fire its anti-radiation missiles, and streak back with impunity. While early anti-radiation missiles like the Kh-28 mentioned already were heavy, the newer generation of anti-radar missiles like the Raduga Kh-58 (NATO code name AS-11 "Kilter") were much lighter and imposed little performance penalty on the Foxbat. 

Mikoyan MiG-25BM Foxbat-F in East Germany
At first the MiG-25BM was to be a dual-role reconnaissance/SEAD aircraft, the concept being that it would use its SEAD capability to allow it to penetrate deep into NATO airspace to complete its reconnaissance mission. By 1977 both the Soviet air forces and Mikoyan realized that the aircraft would be compromised in both roles and different Foxbat variants were developed for each role, with the MiG-25BM being the definitive SEAD variant. The MiG-25BM featured an integrated avionics package called Yaguar (Jaguar) that not only detected and located enemy radars, but it also networked with the Yaguar systems of other MiG-25BMs to allow a "wolf pack" of SEAD Foxbats to operate deep into NATO territory and share data and targeting information with other members of the wolf pack. The Yaguar system included target designation functions that cued the seeker heads of the four Kh-58 missiles that the MiG-25BM carried. In addition to the missiles, nuclear warheads could also be delivered to either knock out SAM missile sites or generate an EMP to short out communications and electronic systems. Several internal active ECM jammers were also carried which not only protected the MiG-25BM from air defense radars but could also counter fighter radars as well. The Foxbat-F was in production from 1982 to 1985, but the complex systems of the aircraft meant that only 40 examples were built. Nearly most were assigned to units stationed in East Germany and were unusual in being the only Foxbats to wear camouflage as the reconnaissance and interceptor variants were gray in color. Despite production ending in 1985, continued technical problems that had to be resolved meant that the first MiG-25BMs weren't operational in East Germany until 1988 with the Group of Soviet Forces Germany (GSFG), which ultimately withdrew from German soil in 1994. 

Kh-58 missile on an Su-24M, Fantasmagoria pod below it
The last SEAD aircraft developed for the Soviet air forces was the Sukhoi Su-24M "Fencer-D", but by this time the Fencer-D was less an dedicated SEAD asset and more an attack aircraft that had SEAD capabilities. Unlike the Yak-28N and the MiG-25BM that housed a large amount of equipment internally, technological advances meant that the Fencer-D could carry most of the radar detection and location equipment in a pod mounted on the centerline underfuselage which was called Fantasmagoria, with -A, -B, and possible -C version depending on the internal configuration of the pod. This was similar to the USAF where the Lockheed Martin F-16CJ replaced the specialized F-4G Phantom Wild Weasel. The F-16CJ had a small pod called the HARM Targeting System (HTS) that performed the same role as the Russian Fantasmagoria pod. The Su-24M could carry two kinds of anti-radiation missile, either the Kh-58 as was used by the MiG-25BM or the newer Kh-31 (NATO code name AS-17 "Krypton") missile. 

Sukhoi Su-24M Fencer-D, note the Fantasmagoria pod
The closest that Russian SEAD aircraft came to being committed to action came during the Soviet invasion and occupation of Afghanistan fron 1979 to 1988. During the war, Tupolev Tu-16 Badgers were used to bomb Mujaheddin positions, but were often tracked by Pakistani air defense and early warning radars. It was proposed to use the Su-24Ms to knock out the Pakistani radars which were providing warning information to Mujaheddin forces, but it was realized that it represented a significant escalation of the conflict and only limited cross-border raids were conducted with SEAD protection. During the Russian-Georgian War of 2008, it is believed that Su-24Ms were used against Georgian air defense positions, but poor tactical coordination resulted in the Georgians shooting down two Fencers. 

The last installment of this series will take a closer look at the anti-radar missiles that the Russians fielded for their SEAD assets. Stay tuned!

Source: Wild Weasel Fighter Attack: The Story of the Suppression of Enemy Air Defences by Thomas Withington. Pen and Sword Aviation, 2008, p100-102. 

16 December 2010

Soviet Wild Weasels: Part One (Doctrine/Tactics)

The Soviet military high command watched with intense interest the American experience in dealing with the dense enemy air defense environment in the skies over North Vietnam. From the lessons noted, the Soviet military had made two conclusions about the American experience- first, that the USAF and the US Navy had placed considerable importance in the suppression of enemy air defenses (SEAD) with specialist aircraft like the Wild Weasels, specialist weapons like the AGM-45 Shrike, and tactics in dealing with what was essentially a Soviet model air defense system protecting North Vietnam. Their second conclusion was that the technological primacy of the United States would the main offset to the Soviet and Warsaw Pact numerical superiority in the event of a conflict in Europe. This meant that not only could they expect the NATO Alliance to deploy sophisticated anti-radar weapons, but that the same technological advances gave NATO a potent air defense system of its own that would have to be dealt with in the event of a Soviet invasion of Western Europe. While both the Soviets and the Americans favored a layered approach to SEAD with specialist aircraft, weapons and tactics, the main difference lay in the operational use of SEAD assets.

Soviet doctrine had SEAD an integral, if not indivisible part, of air operations over Western Europe. While SEAD was primarily a function of specialist units for the NATO Alliance, Soviet SEAD operations were present and integrated into every level of the air battle as their strategy called for "santized" corridors through western airspace to allow their strike aircraft to ingress and egress their targets in the West. For the NATO Alliance, SEAD operations focused on specific locations and weak spots that ELINT (electronic intelligence) had mapped out. Given the numerical inferiority of the SEAD forces of NATO, a focused effort as opposed to a broad effort made more sense. From 1959 onward Soviet doctrine included the early use of nuclear weapons. While tactical and battlefield nuclear weapons were to be used against targets relevant to the land battle- supply depots, troop concentrations, and the like, the SEAD effort called for a series of high-altitude nuclear detonations over Western Europe which would generate a significant amount of electromagnetic pulse (EMP) that would short out electronics of alliance weapons systems and wreak havoc with communications.

Unlike the West where SEAD aircraft were grouped in specialist units, the Soviet Air Force and its Warsaw Pact allies had their SEAD assets parceled out to what were called "task groups"- these were squadron to wing-sized organizations that were assigned from four to eight SEAD aircraft. When a task group was assigned a target, it was the responsibility of the SEAD aircraft to clear the way for the strike package across predefined "santitized" air corridors across West Germany. The prime targets for the Soviet task groups were NATO's air bases and nuclear weapons bases. The SEAD aircraft of the task group were then responsible for dealing with any residual air defense assets that remained after the initial nuclear salvo. The Soviets in particular were concerned with the dispersal of tactical nuclear assets like the Pershing intermediate range ballistic missile and the locations of the alliance's nuclear weaponry were high on any task group target list. 

Soviet planners envisioned NATO's air defenses as a pyramid with the airborne early warning aircraft (like the  Boeing E-3 Sentry AWACS) and early warning radars as the top of the pyramid, disseminating information to other air defense assets that formed the intermediate and lower levels of the pyramid. Realizing that the AWACS aircraft and early warning radars were a key node in the NATO air defenses, considerable effort was apportioned to neutralize these assets, the idea that it would deprive the alliance of the overall picture of the evolving battle. In making the shrewd assessment that there were less AWACS aircraft and early warning radars than lower level, shorter range systems, the Soviets counted on confusion as part of the effort against these more numerous systems which could easily be engaged having lost their long range vision. Though such battlefield systems were still effective as NATO wasn't as reliant on central control as the Soviet air defense model, they were sure to be less coordinated with the key node at the top of the pyramid neutralized. 

Another key difference in the Soviet SEAD doctrine was a reliance on both stand-off weapons and stand-off jamming. While American SEAD and electronic wafare aircraft functioned close to their targets to insure a kill, the Soviets favored longer ranged weapons that could saturate the area and stand-off jamming using specialist aircraft that could jam radars from even a hundred miles out. These jamming aircraft were usually based on either bomber aircraft like the Tu-16 Badger or the Tu-22 Blinder or transport aircraft like the An-12 Cub. The Soviets even fielded a stand-off jamming helicopter version of the Mi-8 that could jam radar systems out to 62 miles. Barrage jamming from stand off ranges would fill the skies with static while SEAD aircraft assigned to the task groups could prosecute specific air defense assets as part of the integrated plan to deprive NATO of its nuclear weapons and aircraft. Shorter-ranged battlefield systems like the British Rapier SAMs or the French Roland were essentially ignored unless they were specifically arrayed in defense of a task group target. These short range systems were to be dealt with by artillery units of the Soviet and Warsaw Pact armies. Anti-radar missiles were reserved soley for high-value assets and targets in the Soviet doctrine as it was felt that over-saturating those assets was the only way to defeat the West's technological superiority. 

Soviet planners envisioned the "sanitized" air corridors over West Germany to be approximately 30-35 miles wide and 124 miles deep. To hit all the necessary high value targets of the alliance, six corridors were needed and a combination of jamming, chaff, and nuclear weapons would keep those corridors open. These corridors were meant to allow the strike packages of the task groups to cross past the most dangerous air defenses which were expected to be over West Germany. Once exiting the corridor on the western end, strike packages then followed their own routes to targets, protected by the organic SEAD aircraft that were assigned to each task group. Many of these corridors were opened up not just by SEAD aircraft, but also by artillery as mentioned already, and by surface-to-surface battlefield missile systems like the SS-21 "Scarab" which had a range of 45-70 miles and could be fitted with a radar-seeker to hit air defense radars. The SS-21 in particular was expected to be used against the Raytheon Hawk SAM batteries. 

The closest that the Soviets and the Warsaw Pact came during the Cold War to using these tactics came during the 1968 Prague Spring in which Alexander Dubcek's reformist government began a series of liberalizing moves in Czechoslovakia that alarmed the Soviet leadership. Following the failure of negotiations through early August to dissuade the Prague government from moving forward, on the night of 20-21 August 1968, over 200,000 Soviet and Warsaw Pact troops invaded the country. Realizing that Czech radars and military units would see the invading forces and supporting aircraft, the Soviet air force initiated an intense, six-hour long barrage jamming effort that blinded the radars while electronic warfare versions of the Antonov An-12 transport sowed an impressive chaff corridor 230 miles long that not only allowed Soviet airborne forces to take Prague, but it also protected the jamming aircraft as well behind curtains of radar-blocking chaff. The corridor was maintained and renewed with more chaff for the six-hour duration of the initial invasion. Other specialist aircraft jammed the Czech communications networks, keeping their own forces from mounting a response to the invasion. 

The next post in this series will take a closer look at the specialist aircraft that were the Soviet counterparts of the Wild Weasels and tasked with destroying NATO's air defense radars and SAM sites. Stay tuned!

Source: Wild Weasel Fighter Attack: The Story of the Suppression of Enemy Air Defences by Thomas Withington. Pen and Sword Aviation, 2008, p92-100. 

12 December 2010

The Reverse Lend-Lease of the Bristol Beaufighter

When the attack on Pearl Harbor brought about the entry of the United States in the Second World War, not one single aircraft was in operational use that was capable of night fighting let alone equipped with an airborne intercept radar. The US military, however, had long been cognizant of the need for a night capability and ten months prior to the attack on Pearl Harbor had already awarded a contract to Northrop for the prototype XP-61A Black Widow night fighters. In the interim, the Douglas A-20 Havoc light twin bomber was modified with British AI (air intercept) Mk. IV radar sets that were built by MIT and an underfuselage pannier that housed four 20-millimeter cannons. This Havoc variant was designated P-70 and the prototype made its first flight in September 1941 before the US entry into the war. It's little known that this interim night fighter conversion did have the name "Nighthawk" but it was rarely used in practice. While most Douglas P-70 Nighthawks remained in the United States to train crews bound for night fighter operations, a small number did serve in the Southwest Pacific where the aircraft was found to be slow and lacking in high altitude performance. 

On 26 January 1943, the USAAF activated its first dedicated night fighter squadron, the 414th Night Fighter Squadron, in Florida at Kissimmee Army Air Field with sixteen officers and enlisted personnel transferred in from other units. Three other squadrons (415th, 416th, and 417th NFS) were also established in Florida where the USAAF had its School of Applied Tactics in Orlando. Given the highly technical nature of night fighting by radar, pilots were specially selected for their technical skills and above average flying skills. The radar operators were selected were the first AI (airborne intercept) radar observers to come from a special training program started by the Army Air Forces. At Kissimmee AAF the pilots and radar observers trained together as a team on the Douglas P-70s. After a month of training, the crews of the 414th NFS were sent to the UK for further training with RAF night-fighter crews on Airspeed Oxfords, Bristol Blenheims, and Bristol Beaufighters. With the P-61 Black Widow not expected to be operational in Europe until the end of 1944 to early 1945, a "reverse" Lend-Lease was arranged in which over 100 radar-equipped Bristol Beaufighters were transferred to the USAAF as they were more capable than the underpowered P-70s used in training. The 414th NFS's radar observers found the transition from the American copy of the AI Mk.IV radar set to the British version. Although identical, wartime experience introduced a set of improvements to the British sets on the Beaufighter that the American versions on the stateside P-70s lacked. To give you an idea of the limitations of the airborne radar sets of the day, the British AI Mk.IV was only usable over 15,000 feet due to ground clutter at lower altitudes and had a detection range between 400 feet to only as far out as 3 miles! 

Following their respective conversion training, the pilots and radar observers of the 414th NFS reunited at RAF Valley in Wales where they took delivery of twelve Beaufighter Mk.VIFs. With additional training through the early summer of 1943, they were joined by the 415th NFS and the two squadrons of American Beaufighters shipped out to North Africa. The second group of squadrons, the 416th and 417th NFS, followed them in August 1943 to North Africa as well. Leaving the UK in groups of five aircraft and led by a Coastal Command Beaufighter for long-distance navigation. After stopping over in Gibraltar, the Beaufighter squadrons then proceeded to their operational bases in Tunisia and Algeria. Operational necessity, however, had the American crews flying daytime interdiction missions against German and Italian aircraft making supply runs to North Africa across the Mediterranean Sea. On the first combat mission for the American Beaufighters, a Heinkel He 115 floatplane was shot down by aircraft from both the 414th and 415th NFS. By the end of the month, however, wiser heads prevailed that didn't wish to waste the specially-trained night fighter crews on daytime air and shipping interdiction missions. Night time enemy air activity would be quiet for the remainder of 1943 until the Allied landings at Anzio, Italy, on 22 January 1944. With the beach heads only thirty miles from Rome, for the next four months some of the most savage fighting until the Battle of the Bulge took place as the Germans tried to overrun the Allied pocket at Anzio. Luftwaffe bomber units based in southern France increased their night time raids on the landing zones and the American Beaufighter squadrons were moved to an improvised base on the island of Corsica to be better positioned to intercept the nocturnal Luftwaffe raiders. 

On 23 January 1944, the day after Allied forces hit the beach at Anzio, 1Lt. James Anderson would of the 414th NFS would score the first night kill for the American Beaufighters against a Dornier Do 217. That first night many of the pilots of the 414th NFS would fly two, even three missions from their improvised base. Of the twelve Beaufighters in the squadron, nine of them flew nearly nonstop that first night. By the time Allied gains at Anzio had been consolidated, the 414th NFS had converted to the vastly improved AI Mk. VIII centimetric radar set. The squadron was then moved to the mainland in October 1944 and two months later converted to the Northrop P-61 Black Widow. The 415th NFS operated from bases in Sicily after moving across the Mediterranean, as did the 416th NFS where they covered the Allied supply line from North Africa to Italy. The 416th eventually got moved forward to Italy itself as well while the 417th stayed behind in North Africa to cover the rear logistics areas of the Allied invasion of Italy before moving to Corsica in 1944. By that time, those three squadrons had also converted to the AI Mk. VIII centimetric radar set for their Beaufighters. In addition to the night fighter patrols, the three squadrons' Beaufighters also flew night intruder missions against ground targets as well throughout Italy during the drive northward from Anzio. 

With the Beaufighter squadrons now based on Corsica, they were well-placed to protect the Allied invasion assembly areas for the August 1944 landings in southern France, Operation Anvil-Dragoon. In addition to night fighter patrols of the rear logistics areas on Corsica and the assembly points for the invasion fleet nearby, the squadrons were also tasked with night intruder missions on various Vichy and German targets in southern France in the run up to the 15 August landings between Cannes and Toulon. Once the Allies had captured the port city of Marseilles, the 417th NFS was moved forward to Le Vallon in the Rhone River valley to intercept German reconnaissance flights and raids on Marseilles where incoming Allied forces were being disembarked. Other missions included the continued nocturnal raids and patrols for increasing numbers of midget submarines seeking to disrupt the Allied shipping in Marseilles harbor. By this point the Beaufighters were over three years old and much overhaul work had been delayed due to the combat situation. In less than three months, the 417th NFS alone would lose nine Beaufighters to technical problems. By the end of 1944, the USAAF decided to begin the drawdown of Beaufighter operations- the 414th NFS, still operating in Italy, was the first to convert to the P-61 Black Widow in December. The 415th NFS, operating near Nancy, France, converted to the P-61 Black Widow as well. The 416th NFS traded in its weary Beaufighters for the De Havilland Mosquito NF Mk. XIII and the 417th NFS, the last of the four night fighter squadrons, was moved northward to Belgium and traded in its Beaufighters for the P-61 Black Widow in March 1945, marking the end of the unique "reverse" Lend-Lease operation for the USAAF. 

Source: Air Fan International, July 1996, Volume 1, Number 5. "Southern Beaus- USAAF night fighter operations in the Mediterranean during World War II" by Rene J. Francillon, p54-63. 

11 December 2010

27 Years Before the Eagle Was the First F-15

The Northrop P-61 Black Widow, despite having a wingspan of 66 feet and being the size of most medium bombers, possessed a high speed and maneuverability that made it a candidate for further development into a very-long range day fighter. With the war in the Pacific now on the front door step of the Home Islands, there arose a need for a fighter with a very long range to escort the Boeing B-29 Superfortress bombers from their bases in the Marianas and China to Japan and back. The development of the Lockheed XP-58 Chain Lightning was hobbled by troublesome powerplant issues and innumerable deficiencies uncovered in the flight test program for the Fisher XP-75 Eagle meant that the USAAF had to fall back on a long range version of the Thunderbolt, the Repubic P-47N. Not feeling that this was the optimum solution, the USAAF authorized development of twin-seat, twin-engine escort fighter designs to meet the need for a long-range B-29 escort. North American was issued a contract to develop the P-51 Mustang into the P-82 Twin Mustang while Northrop was given a contract to develop a day fighter version of the P-61 Black Widow. 

To save time given the pressing needs of the Pacific War, two P-16B Black Widow airframes were pulled from the production line (the aircraft were 42-39549 and 42-39557) to be modified into the XP-61E prototypes. The primary modification was the replacement of the center crew nacelle with a new nacelle that had only 50% of the cross-section of that of the Black Widow. Instead of housing three crew members, the new nacelle sat two pilots in tandem under what was a the time the world's largest single-piece bubble canopy. The air intercept radar in the nose of the Black Widow was replaced with four 50-caliber machine guns which would form the new fighter's main armament. The four 20mm cannon in the belly of the nacelle were retained on the XP-61E. Extra fuel tanks in the new crew nacelle aft of the cockpit gave the aircraft a 1,158-gallon fuel load, nearly double the 640-gallon capacity of the Black Widow. In addition, the XP-61E could carry four 310-gallon external fuel tanks as opposed to the just two external tanks of the Black Widow. 

By the time of the XP-61E's first flight on 20 November 1944 from Northrop's facility in Hawthorne, California, the war in the Pacific had progressed rapidly and the landings on Iwo Jima in February 1945 gave the USAAF an airfield that was halfway between its main B-29 bases in the Marianas and Japan. Basing of P-51 Mustangs on Iwo Jima now made the need for an escort fighter with the same range as the B-29 superfluous. However, with the planning underway for the Allied landings on the home island of Kyushu on October 1945 (Operation Olympic) and the landings on the main island of Honshu (Operation Coronet) set for the spring of 1946, a need arose for fast, agile reconnaissance aircraft to map the planned invasion zones and associated targets. While realizing that the reconnaissance need would ultimately be met by the Hughes XF-11 and the Republic XF-12 then under development, the USAAF wanted an interim design based on the XP-61E designated the F-15A Reporter. With an estimated eventual need for 320 F-15As, the USAAF ordered the first batch of 175 Reporters in June 1945 as Northrop's design would be ready much sooner than either Hughes or Republic's custom-tailored versions. 

Given that all that was needed was removal of the four 20mm cannon in the belly of the central crew nacelle and replacement of the 50-caliber machine guns in the nose with camera equipment, Northrop had the first XF-15 Reporter ready in only five weeks. The six camera stations in the nose could accommodate 17 different types of cameras in 24 combinations. With the armament removed, the F-15A would have a range of over 4,000 miles with 1,330 gallons (increased over that of the XP-61E thanks to the removal of the underbelly cannons) internally and another 1,240 gallons in the four external tanks. Despite such promising performance, the second XF-15A prototype was not completed until 10 August 1945 due to the need to fit turbosuperchargers to the Pratt & Whitney R-2800 radial engines, the day after the second atomic bomb was dropped on Nagasaki. 

With the Japanese unconditional surrender on 15 August 1945, the need for reconnaissance coverage for the invasion of Japan evaporated, but the USAAF recognized the need for detailed mapping of Japan and its occupied territories to support the postwar occupation and reconstruction of the country. As a result, the original purchase contract for 175 F-15A Reporters escaped the wholesale cancellations that swept the US aircraft industry following the end of the war. However, the contract was amended from 175 examples to just 36 aircraft on 21 May 1946. The first production F-15A Reporter was delivered to the USAAF on 4 September 1946. The planned penultimate reconnaissance aircraft of the war, the Hughes XF-11 and the Republic XF-12 Rainbow, made their first flights in 1946 on 7 July and 7 February, respectively. Tail number 45-59302 was the first operational F-15A accepted into service and was named "Klondike Kodak" and photomapping operations were started in July 1946 with the 8th Photo Reconnaissance Squadron based at Johnson AB in Japan. Over the next 30 months the 8th PRS's fleet of Reporters mapped Japan, South Korea, and the Philippines. Only two aircraft were lost in those 30 months, an impressively low-loss rate given the long range nature of the photomapping missions. In addition, the 7th PRS and the 63rd PRS operated clandestine reconnaissance missions from Yokota and Johnson AB in Japan, presumably over Communist-held areas in China, Korea, and possibly over the Soviet Union. 

In June 1948, following the establishment of the US Air Force as independent branch of the military the year prior, the F-for-foto designation was changed to the R-for-reconnaissance prefix and the F-15A become the RF-61C (with F now standing for fighter). The 8th PRS, the main unit that operated the small group of Reporters, was redesignated the 8th Tactical Reconnaissance Squadron as a result of the designation change, but by this point Reporter operations were being drawn down with the first aircraft going into storage. The last RF-61C Reporter was stricken from active duty on 14 March 1950, only three months before the Korean War broke out. 

The non-operational history of the F-15A/RF-61C Reporter included the use of a single aircraft (45-59318) in Operation Thunderstorm from 1946 to 1947 along with several other P-61B Black Widows. This particular Reporter was disposed of by the USAF in November 1949. The first Reporter prototype (45-95300) was used for another 17 months by the USAF and Northrop on a variety of test programs before it was passed onto the National Advisory Committee on Aeronautics (NACA, the predecessor organization of NASA), where it was operated from Moffett Field, California between 1948 and 1950 to carry aloft various test shapes and scale flying models to be dropped from high altitudes. By 1951 when all other Reporters had been scrapped, this first Reporter went on the US civil register as N5093V and even did a short stint in Mexico as XB-FUJ, both times in an aerial spray role. In returned to the United States in the operation of the US Forestry Service as N9768Z where it was modified with a large fire retardant tank under the central crew nacelle. Operated by Aero Enterprises of Fresno, California, on behalf of the USFS, it was nicknamed the "Pregnant Widow" and was lost when it crashed near Hollister, California during a retardant drop on 6 September 1968. 

Source: Air Fan International, September 1996, Volume 1, Number 6. "Northrop Reporter- The first F-15 was no Eagle" by Alain Pelletier, p54-62. 

09 December 2010

Baptism of Fire; The North Vietnamese Air Force in 1965

Following the French defeat at Dien Bien Phu in 1954 that resulted in the partition of Vietnam in to the North and South, the Ministry of Defense for the Communist north embarked on an upgrade of the country's military infrastructure which included laying the foundation for a modern jet-equipped air force. All the former French and Japanese airfields were modernized to handle jet fighters and by the summer of 1955, nine bases had been made operational. In March 1956 the first group of 110 North Vietnamese flight students were sent abroad for flight training- most went to China, some went to the Soviet Union. One-third of the students were earmarked for fighter aircraft, another third for transport aircraft, and the last third directed into helicopter training. At the end of the year, the Chinese military assisted in setting up local flight training programs at the air bases of Cat Bai and Gia Lam, with MiG-15UTI two-seat trainers soon to follow. By 1958, the Vietnamese People's Air Force (VPAF) had 44 operational airfields capable of operating the more capable Mikoyan MiG-17 "Fresco". Just a year later all primary flight instruction took place in North Vietnam, but advanced jet conversion to the MiG-17 still had to take place in the Soviet Union, the first group of VPAF pilots making the conversion to the Fresco in 1960. A few months later, the North Vietnamese had arranged for a second operational conversion site in China to accelerate the build up of jet fighter pilots. By 1962 the nascent VPAF had 36 MiG-17s as its front-line jet fighter along with a small number of MiG-15UTI trainers. On 3 February 1964 the VPAF established the 921st Fighter Regiment at Noi Bai AB as the first operationally-trained Vietnamese fighter pilots returned from the Soviet Union. It would be quite an accomplishment in just 10 years for a nation as limited in resources as North Vietnam. 

Following the Gulf of Tonkin incident on 2 August 1964, President Lyndon Johnson ordered Operation Pierce Arrow which saw Navy aircraft from the carriers Ticonderoga and Constellation hit targets in North Vietnam, opening the first US air combat missions of the Vietnam War.  The VPAF at the time was still not at an operational state to defend against these initial strikes but the perceived American aggression intensified Soviet and Chinese logistical support to bring the VPAF up the strength. VPAF commanders feared the USAF and US Navy would use their numerical advantage and tactical experience to vary their attack patterns, but to their surprise, US forces adhered to very routine and obvious patterns that made planning interception missions easy. Even worse, the Vietnamese could determine the possible target area as US reconnaissance aircraft would make repeated runs against certain areas the day prior to an attack. Continued escalation on both sides resulted in Operation Flaming Dart in March 1965 which then transitioned to the 44-month long Operation Rolling Thunder that would finally introduced air combat over the skies of Vietnam.

The first strikes of Operation Rolling Thunder took place on 2 March 1965 when a USAF strike force of Republic F-105D Thunderchiefs and North American F-100 Super Sabres hit an ammunition dump near Vinh in the far southern part of North Vietnam and out of range of the VPAF's small MiG force. As the air strikes of Rolling Thunder moved northward over the course of the month, the VPAF prepared for action. On 3 April 1965 the 921st Fighter Regiment went on alert and six MiG-17swere armed and prepared for takeoff. Observing the US reconnaissance flight patterns led the VPAF to conclude the rail bridges at Ham Rong were the target and ground radars were already tracking the inbound US Navy strike force. With pilots already sitting in their cockpits, the order was given at 0940 to scramble to intercept the strike force on the VPAF's first operational combat mission. Four of the MiGs were the "intercept flight", responsible for attacking the Navy strike force. Two more MiGs formed the "covering flight" to follow the intercept group and defend against any attacks. Flying in a "finger four" formation, Pham Ngoc Lan was the flight leader, with Phan Van Tuc as his wingman on the left, Ho Van Quy as #3 on the right, and Tran Minh Phuong in the #4 position. The group raced southward at low level to avoid getting targeted by an over-enthusiastic SAM units and it also masked the group from airborne radar. 

Arriving in the vicinity of the bridge, the four VPAF pilots could see a mixed force of Vought F-8 Crusaders and Douglas A-4 Skyhawks attacking the bridge. The four accelerated and then pulled up to gain an altitude advantage against the strikers which had not seen their approach. Pham Ngoc Lan and his wingman zeroed in on a pair of unsuspecting Crusaders. His wingman, Phan Van Tuc, fired his MiG's cannon first before Pham Ngoc Lan had to cut across him to narrow the distance and fired on one of the Crusaders at only 400 yards, scoring hits and an explosion. Believing that another pair of Navy aircraft were closing in on them from below and to the right, Pham Ngoc Lan had his wingman take the lead and Phan Van Tuc fired again, scoring hits on a second aircraft that crashed. It would later turn out after the war that the Crusader Pham Ngoc Lan thought he had shot down was severely damaged, but its pilot, Lt. Commander Spence Thomas of VF-211 from the USS Intrepid, managed to nurse his stricken Crusader to an emergency landing at Da Nang where it had to be written off due to battle damage. Phan Van Tuc's kill was most likely the A-4C Skyhawk that was listed by the US Navy has having been downed by AAA fire. 

The MiG force was then ordered to return to base before running out of fuel (the MiG-17s were short-legged, particularly as it took a lot of afterburner use in dogfights to maintain speed), but the flight leader, Pham Ngoc Lan, got separated from his men and his compass failed. Having trained in the area during his basic flight instruction, he had a rough idea where he was and with his fuel supply dwindling, he set up to make a crash landing on the banks of the Duong River south of Hanoi. Ignoring his ground controller's order to bail out, Pham Ngoc Lan wanted to try and save the MiG knowing that there were only a small number operational with the VPAF. Missing a sampan by only a few feet, his aircraft skipped along the water and knocked him unconscious before coming to rest on a mud flat. When he came to, he found himself surrounded by a local Vietnamese militia pointing their guns at him, thinking he was a downed American pilot. Despite showing them his identity papers, it took a local village elder to defuse the situation. Given that Pham Ngoc Lan was born and raised originally in the South, his accent made him sound like he was from South Vietnam which complicated matters. Before long a helicopter from his base arrived to retrieve him and the MiG was also recovered and put back into service, a testament to the toughness of the design. Returning his base, he found out that the other men of his flight had managed to land safely. 

The aggressive performance of the VPAF that day surprised the Americans as they weren't expecting any significant aerial opposition. However, while the VPAF managed to learn and adapt into facing a numerically and technologically superior adversary in their subsonic MiGs, rigid doctrines and political interference would continue to handicap the US war effort for years to come.  Pham Ngoc Lan would finish out the war with three kills and his wingman, Phan Van Tuc, would finish out the war as an ace with six kills.

Since that day in 1965, the Vietnamese government made the third of April a public holiday called "Air Force Day".

Source: MiGs Over North Vietnam: The Vietnam People's Air Force in Combat, 1965-1975 by Roger Boniface. Stackpole Books, 2010, p1-9.