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. 

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.

The Origins of Red Flag

I had started this blog out as a way of sharing a lot of the interesting aviation history I come across in the course of my reading. I'm a bit attention-deficit when it comes to reading, I usually jump between numerous books at once as I've really never been able to read one book straight through then start another. The benefit of this little quirk of mine is that what I post in this blog can be quite varied. Most of the time as I'm reading, I'll put a little dog ear on pages that I think have good material for this blog and over time, you can guess that most of my aviation books have little dog ears in the lower corners. I'll have several possible topics rattling around in my head at any given time and then when I have the chance to sit down and start a post, it's just a matter of seeing which one topic I've been ruminating over comes easiest to type! The topic I had planned for today got postponed as I learned via my regular Twitter stream this morning that on this date thirty-five years ago the first Red Flag exercise was held at Nellis AFB, Nevada. I just happen to be currently reading Steve Davies' wonderfully engaging book Red Eagles: America's Secret MiGs and it details the origins of the now-famous combat aircraft exercise that is held several times a year at Nellis. 

This past weekend I had posted about those first secret MiGs that operated out of Area 51/Groom Lake. The operational exploitation of the MiGs was but one of the first steps taken by the US Air Force and the US Navy to reverse the sagging fortunes of US fighter pilots over the skies of Vietnam. In 1966 the Tactical Fighter Weapons Center (TFWC) was established at Nellis AFB as the leading school house of fighter tactics evaluation and training. One of the keys to the TFWC was making use of the 12,000 square miles of uninhabited desert terrain north of Nellis that gave in the words of Steve Davies "the playground for America's finest fighter pilots". One of the earliest projects based out of the TFWC was the "Red Baron" reports. Since 1966 the Department of Defense's Weapon Systems Evaluation Group had been collecting a wealth of information on every one of the 320 MiG encounters in Vietnam until July 1967 that involved either the McDonnell F-4 Phantom or the Vought F-8 Crusader. That exhaustive data set became Volume I of Red Baron. Volumes II and III analyzed another 259 MiG encounters by Republic F-105 Thunderchiefs as well as other US aircraft. That three-volume set of data became Red Baron I. In 1969, Red Baron II covered 625 MiG encounters from 1967 to the end of Operation Rolling Thunder at the end of 1968. Later, Red Baron III completed the comprehensive analysis of the air war. 

The Red Baron reports were incredibly detailed with interviews of crew members and pilots with questions to be answered such as "Where were you when you first saw the bogeys?" or "What altitudes and speeds were being used in setting up the engagement?". The bottom line of the Red Baron reports was quite simply that American fighter pilots in Vietnam were not familiar enough with fighting dissimilar aircraft- what was needed was DACT- Dissimilar Air Combat Training. Red Baron went even further, recommending that the USAF provide its fighter pilots with realistic enough training based on the detailed study of all of the MiG encounters in the classified reports. One recommendation was the use of actual enemy aircraft (which stemmed from the programs I posted about this weekend) or realistic substitutes. That recommendation led to the formation of the USAF Aggressors, units operating Northrop T-38 Talon trainers and F-5E Tiger II fighters as surrogates for enemy MiGs. The pilots of the Aggressors specialized in emulating Soviet tactics, even using their own organic GCI controllers. 

The first Aggressor squadron stood up at Nellis AFB in the summer of 1972, but some of the founders and proponents of the Aggressors wanted to push the training even further. While the first Aggressor squadrons were wildly successful to the point that two overseas Aggressor squadrons were established (one in the Philippines at Clark AB for PACAF and one at RAF Alconbury for USAFE), it was a well-known fact from the Red Baron reports that new fighter pilots in the skies over Vietnam had a disproportionately low life expectancy. Other USAF studies had shown that the majority of combat losses (even outside of Vietnam) occurred within a new pilot's first ten combat missions. Once getting the eleventh combat mission, a new pilot's survival chances quickly improved due to experience. The solution was an elegant one that dovetailed nicely with the mission of Nellis AFB, that of the Aggressors as well as the secret MiG force then based at Area 51/Groom Lake. Recreate the first ten combat missions for pilots in the training environment at Nellis AFB using not only the Aggressors and the MiGs, but also the air-to-ground ranges to improve the accuracy of strike aircraft crews. In May 1975, the Tactical Air Command commander, General Robert J. Dixon, gave his approval for the formation of Red Flag with the first exercises to be held in six months. 

In that hectic six months, the most realistic training environment was created at the weapons ranges north of Nellis AFB. Not only were there to be fighter and strike aircraft, but also electronic warfare aircraft, transports and tankers. Reconnaissance assets would participate. Captured Soviet radar systems and facsimilies were arrayed in the ranges along with an integrated missile and anti-aircraft gun defense system. Targets were laid out and finally, the Aggressors would play the part of enemy MiGs (eventually even the secret MiG force participated). Right on schedule, on 29 November 1975, Red Flag I took place with 37 aircraft, 561 personnel and a total of 552 sorties were flown.

Today's Red Flag is a three week exercise in which entire squadrons deploy with their maintenance and support personnel as if on a wartime deployment. The average Red Flag exercise will have around 100 aircraft with several thousand personnel. Units from all branches of the US military participate as well as Allied nations where an invitation to Red Flag is considered an honor and testament to a foreign unit's professionalism. Since that first Red Flag exercise thirty-five years ago today, it's estimated that over half-a-million personnel have been trained, over 300 types of aircraft have participated and well over thiry nations have participated. 

Source: Red Eagles: America's Secret MiGs by Steve Davies. Osprey Publishing, 2008, p24-37.

How A Top Secret Program Restored American Air Superiority

At the height of the Vietnam War, the skies were filled with technologically-advanced American aircraft from both the US Navy and the USAF, yet the air battles were a thread-bare echo of past glories in the 1950s skies over Korea's MiG Alley. By 1967 the Navy had a kill ratio of only 3.7 to 1 (3.7 MiG kills for every Navy fighter lost to a MiG) and the USAF was even worse, with a kill ratio of only 2.2 to 1. By comparison, at the end of the Korean War, the USAF pilots of the North American F-86 Sabre alone had a kill ratio of 10 to 1. While various studies and reports like the Navy's Ault Report offered many suggestions, the basic fact of the matter was that the art of dogfighting as a skill had been lost. In the USAF, for instance, the solution in the 1960s to an increasing accident rate in the McDonnell Douglas F-4 Phantom II was to simply ban air combat maneuvering training (ACM)- the accident rate fell, but legions of Air Force Phantom drivers entered the skies of Vietnam with little experience in knowing that their aircraft could and couldn't do in a dogfight with North Vietnamese MiGs. While a the solutions that eventually restored American supremacy in the skies are complex and beyond the scope of today's blog post, the foundations were being laid down in the black world in the latter half of the 1960s. 

The story begins on 16 August 1966 in the Middle East. Operation Rolling Thunder, the sustained air bombardment of North Vietnam, had begun the year prior and would continue until 1968. Monir Radfa, an Iraqi Air Force captain, took off in his Mikoyan MiG-21F from Rashid AB outside of the Iraqi capital for what was supposed to be a local navigation exercise. Instead, he made a dash to the southwest at low level, intending to defect to Israel. The Jordanians failed to intercept him as he streaked low across their country, the RJAF's Hawker Hunters too slow at low level. Once over Israel, he lowered his landing gear and wagged his wings to two intercepting Israeli Mirage III fighters, signaling his intentions and was escorted to Hatzor AB and given asylum. With the MiG-21 being one of the most potent fighters in the Arab air forces that threatened Israel, they immediately set about flight testing the MiG-21 for over 100 hours over the next 12 months, learning its strengths and weaknesses and teaching the Mirage III pilots (the French delta was the main fighter of the IDF in those days) how to defeat the MiG in a dogfight. Initially hesitant to share its prize with the United States, Israel eventually concluded an agreement brokered by the US Defense Intelligence Agency (DIA) to loan the MiG-21 to the US for study in exchange for being allowed to buy the F-4 Phantom II, the American front-line fighter of the day. At the time the Israelis had made several overtures to the Johnson Administration to purchase the Phantom, only to be rebuffed out of a fear by President Johnson of escalating matters in the Middle East. Now that the Israelis had leverage, the Phantoms would be on their way and the US would finally get to study its vaunted adversary in the skies of Vietnam up close. 

The MiG was disassembled and transported by a Lockheed C-5 Galaxy to the USAF's secret testing base at Groom Lake, Nevada (Area 51). Responsibility for evaluation of the MiG-21 was given to the USAF's Foreign Technology Division (FTD) that was part of the Air Force Systems Command based at Wright-Patterson AFB in Ohio. AFSC assigned all of its programs with the code word prefix "HAVE". For example, the original stealth demonstrator aircraft that gave rise to the Lockheed F-117 Nighthawk was code named "HAVE BLUE". In the case of the MiG-21 on loan from Israel, it was code named "HAVE DOUGHNUT". Two categories of flight testing were performed on the MiG- the first type concerned technical analysis- performance, flight envelope, engineering, structures, and so on. The second part of the tests were operational- the MiG would be flown in mock dogfights against US fighter aircraft. Because AFSC/FTD's emphasis was technical in nature, most of the HAVE DOUGHNUT flying concerned technical analysis. 

The first flight out of Groom Lake took place in January 1968 and continued until April of that year before the MiG was returned to Israel. For three intensive months, the MiG was flown in various profiles to determine how it could be detected by both radar and infrared systems, it flew against the bombers of the Strategic Air Command to see how well the bombers' systems could detect and counter it, and infrared signature tests were carried out using a specially-fitted T-39 Sabreliner that could mount the seeker heads of various missiles in the US inventory. Out of a total of 102 sorties flown as part of HAVE DOUGHNUT, 33 sorties were devoted to operational testing in mock dogfights with the USAF and 25 sorties were devoted to mock dogfights with the Navy. 

Not four months after the end of HAVE DOUGHNUT, two Syrian MiG-17Fs on a navigation exercise got lost and inadvertently landed at an Israeli air base. Acquisition of the MiG-17s was of high importance to the United States as the MiG-17, though slow and dated, was nimble and the main adversary type encountered in the skies of Vietnam. Though limited to subsonic performance, VNAF MiG-17s were flying circles around American fighter pilots leading to the dismal kill ratios I mentioned above. After testing by the Israelis, the two MiG-17s were then turned over to the United States for analysis. The first MiG-17 made its first US flight at Groom Lake in January 1969 with the code name HAVE DRILL. The second MiG-17 then flew in March of that year with the code name HAVE FERRY. Both programs wound down by June 1969 and the findings were shared with the Navy's new TOPGUN school that was established to reintroduce dogfighting skills to Navy pilots. In addition, the findings of HAVE DOUGHNUT, HAVE DRILL, and HAVE FERRY were shared with the instructors at the USAF's Fighter Weapons School at Nellis AFB, Nevada, where they would go on to establish the Red Flag exercises. 

On 25 November 1969 a Cambodian Khmer Air Force pilot defected to South Vietnam in the Chinese copy of the MiG-17F, the Shenyang J-5. The USAF pilot who flew the MiG-17 in HAVE FERRY and HAVE DRILL, Col. Wendell Shawler, was tapped by the AFSC/FTD to go to South Vietnam and make several evaluation flights of the J-5 to establish that it had the same flight characteristics as the MiG-17. This short program of just five flights from Phu Cat AB in South Vietnam was code named HAVE PRIVILEGE. 

As a result of these four top secret exploitation programs, both USAF and Navy fighter tactics were changed and pilots were once again trained to exact as much capability and performance out of the aircraft as possible to win the dogfight. It wasn't until 1989 that a Pentagon official confirmed that in the 1981 combat of two US Navy F-14 Tomcats versus two Libyan Sukhoi Su-17 fighters over the Gulf of Sidra that the tactics used had been developed out of mock combat testing with US-operating Soviet fighters. Not long afterwards, HAVE DOUGHNUT, HAVE DRILL, HAVE FERRY, and HAVE PRIVILEGE were declassified. What didn't get mentioned was that a much bigger program succeeded those programs and would remain top secret for 20 years! But more on that program in a future blog post! 

Source: Red Eagles: America's Secret MiGs by Steve Davies. Osprey Publishing, 2008, p16-20.

Foxbats Over the Sinai

By 1971 the Soviet Union had built up the Egyptian Air Force to unprecedented levels in the Middle East in the years since the 1967 Six-Day War when the Israelis caught the majority of the Egyptian air arm on the ground. Despite the rearmament effort and 20,000 military advisers, the Egyptians were still in no position to confront the Israeli Air Force over the Sinai. The three-year War of Attrition between Egypt and Israel ended in 1970 when President Nasser of Egypt died of a heart attack. With no gains being made by either side, Nasser's successor, Anwar Sadat, ended the campaign and set about the planning of what would be the 1973 Yom Kippur War. While direct Soviet military involvement was out of the question given the atmosphere of detente that was building between the Soviet Union and the United States, Soviet Premier Leonid Brezhnev authorized the deployment of a reconnaissance task force of MiG-25 "Foxbat" aircraft to Egypt to scout the Israeli defenses on the east bank of the Sinai. It was a bold decision given that most new Soviet aircraft are kept secret for several years, let alone deployed overseas. Operational testing of the Foxbat began in 1970 and there were a multitude of technical problems uncovered that left both the Soviet Air Force (VVS) and the Air Defense Forces (PVO) reconsidering accepting the aircraft for operational service. 

The Deputy Minister of Aircraft Industry, Aleksey Minayev, was a former engineer with OKB Mikoyan who had participated in the development of the MiG-25 before assuming his ministry position at the Kremlin. Being well aware of the VVS and PVO hesitations with the new aircraft, it was Minayev that suggested the deployment of the Foxbat the Middle East in the reconnaissance role. He had no trouble in getting the military to agree to the idea as they were anxious to really see the aircraft operate in a realistic environment to see what it could do and decide then whether or not to proceed with the deployment of the aircraft. It was agreed that the interceptor version of the Foxbat would be unsuitable for the deployment as that would have been considered an overt act and a small handful of interceptors would have been unable to hold off the Israelis. Discussion within the Kremlin came to a consensus that sending the reconnaissance version would do more good as they could provide information on the Israeli defenses in the Sinai. 

Four MiG-25s that were undergoing operational testing were selected for deployment. Two aircraft were MiG-25Rs, which was a pure reconnaissance variant and the other two were MiG-25RBs that were dual-role reconnaissance/strike aircraft. Ironically, the RB variant of the Foxbat came about due to a perceived need for a high-speed strike aircraft to counter the Israeli's deep penetration flights with McDonnell F-4E Phantom IIs during the War of Attrition to knock out Egyptian targets. The formal deployment orders were issued in March 1971 and a team of test program technicians that were ironing out the Foxbat's bugs would accompany the task force to Egypt. To save time, the personnel were flown to Cairo-West AB in Egypt aboard Antonov An-12 "Cub" transports and the Foxbats had their wings, tails and engines removed for transport about Antonov An-22 "Cock" transports. However, it was found that even stripped down, the MiGs were just barely too wide and too high to fit into the An-22 cargo hold as the main landing gears were getting stuck in the aft cargo door. A technician suggested reversing the main landing gear legs so they pointed inward and replacing the mainwheels with those from a MiG-21. This provided enough clearance to get the MiGs aboard for transport to Egypt. At Cairo-West, the Egyptians had already built hardened aircraft shelters for the Foxbats and the Soviet team reassembled the Foxbats inside the shelters. 

The first test flights began in April over Egyptian territory. The design bureau for the Foxbat's massive R15B-300 engines, OKB Tumansky, also had a team in place that managed to tweak the engines to allow the Foxbat to "sprint" at full afterburner for a full 40 minutes, well over the previous three minute limit used in operational testing in the Soviet Union. The first operational reconnaissance mission took place on 10 October 1971. Operating in pairs, two MiG-25s streaked up the Mediterranean coast from the Nile Delta to the Israeli-Lebanese border at 70,000 feet at high speed only 17 miles off the Israeli coast. Interceptions were attempted by F-4 Phantoms but failed to engage the Foxbats. A month later, a single MiG-25 overflew the northern Sinai to image the Israeli defenses there. This time the Israelis had two stripped down F-4 Phantoms ready which attempted to shoot down the MiG with AIM-7 Sparrow missiles. The missile's proximity fuses failed to cope with the Mach 3 speeds and detonated harmlessly past the speeding Foxbat. After an increasing number of overflights of the Sinai that resulted in failed intercepts, the Israelis were incensed. As the Soviet pilots maintained strict radio silence, the Israelis had no choice but to station F-4 patrols near Cairo-West AB, hoping to shoot down a MiG on takeoff. To counter this tactic, Egyptian MiG-21s from other airbases would converge on Cairo-West when the Foxbats were ready to takeoff. At least two MiG-21s would streak down the runway at low level, followed by the pair of Foxbats and then followed by another two MiG-21s to cover the rear until the Soviet pilots were at speed and altitude out of reach of the prowling Phantom patrols. 

Missions were typically flown in pairs and operated at over 70,000 feet at full afterburner. At Mach 3, a Foxbat pair could cover in just two minutes the entire length of the Suez Canal that separated Egyptian and Israeli forces. Fuel was burned off at 1,000 lbs per minute as the aircraft maintained full afterburner. The inlet ducts would heat up to 608 degrees Farenheint (320 degrees Celsius) and the aircraft skin would measure 577 degrees Farenheint (303 degrees Celsius). Pilots reported the glass canopy was so hot that it would burn their fingers if it was touched during a mission. The cameras operated automatically as the MiGs covered 1 kilometer a second. In addition, the onboard ELINT sensors would pinpoint the locations of Israeli radars, communications nodes, and ECM units. On descent and approach back to Cairo-West, the Foxbats were again met by Egyptian MiG-21s all the way to runway touchdown. Two missions a month were flown and by the end of 1971 the Soviets were making routine deep penetration flights over the Sinai with impunity. Even the Raytheon Hawk SAM units in the Sinai were useless as they were only medium altitude surface-to-air missiles with an engagement envelope that topped off at 40,000 feet. 

By the spring of 1972 the Israelis were protesting the Soviet flights to the United Nations, but it was Anwar Sadat that ended the reconnaissance flights. Frustrated that the Soviets were not training his pilots in the aircraft and that it was not being offered to him for sale, the last straw came after a superpower summit when both Brezhnev and Nixon agreed on maintaining the status quo in the Middle East. Realizing that the Soviets were not going to help him retake the Sinai, Sadat ordered nearly all of the Soviet advisers out of the country and preceded to plan for war without their assistance. Sadat issued an ultimatum to the Soviets as well that they had one week to decide to sell Egypt the Foxbat or have them out of the country. By the middle of July 1972, the reconnaissance task force had returned to Russia and the performance of the Foxbat resulted in the VVS and PVO accepting the aircraft for formal operational deployment. 

Sadat launched the October 1973 Yom Kippur War and made startling gains against a complacent Israeli military while the Syrians attempted to retake the Golan Heights in the north. As the course of the war gradually came to favor the Israelis, Sadat was at a point where he was considering accepting a cease-fire. To prompt him to end the war quickly, Brezhnev ordered two MiG-25s back to Egypt to conduct a series of reconnaissance missions over the Suez Canal to prove to Sadat the Ariel Sharon's units had crossed the west bank of the Suez into Egypt and the Egyptian Third Army was completely surrounded by the Israelis. The imagery shown to Sadat forced him into accepting the cease-fire ending the October war. The Foxbats stayed until 1974, but most of their missions by this point had been focused on monitoring US naval activity in the eastern Mediterranean. Once again frustrated that Egypt was still not being offered the Foxbat and that he had no authority over their use, he ordered the Soviets back out of the country again in 1975, ending the last active Soviet involvement in the Middle East. 

Source: OKB Mikoyan: A History of the Design Bureau and its Aircraft by Yefim Gordon and Dmitriy Komissarov. Midland Publishing, 2009, p324-345.

The Experimental STOL Demonstrator That Fooled NATO

Impressed with the performance of the McDonnell F-4 Phantom II that had just been introduced into service with the US Navy, the Soviet Air Force asked the Mikoyan design bureau (OKB Mikoyan) for a successor to the MiG-21 "Fishbed" that could counter the F-4 on equal terms. The first attempt by the OKB was the experimental Ye-8 demonstrator that was based on the MiG-21. However, the Ye-8 suffered from numerous technical problems that led to the loss of the first prototype and before the second Ye-8 could be flown, priorities with the Soviet Air Force command staff had changed on the characteristics of the replacement design and now emphasized STOL performance as it was felt that the long runways needed by most Soviet fighters were vulnerable to attack by NATO's intermediate-range ballistic missiles. STOL performance would allow the fighter to be deployed to remote areas away from the main air bases in the Soviet Union and Eastern Europe. Mikoyan's studies of STOL configurations were subsequently narrowed down to two configurations- one using variable-geometry "swing wings" and one using lift engines. Although using lift engines would be simpler in theory, swing wings allowed for more space in the fuselage for fuel and weapons. Although Artyom Mikoyan himself favored swing wings, a 1961 report by the prestigious Russian aerodynamic institute, TsAGI, concluded that there were considerable aerodynamic issues as well as construction issues with variable geometry wings. 

While there had not yet been any flight testing of swing wing designs in the 1960s in the Soviet Union, Mikoyan already had experience with STOL jet lift fighter technology, having flown in 1966 the Ye-7 (also referred to as izdeliye 23-01, izdeliye meaning "article", usually in reference to demonstrator or prototype) which was a MiG-21 modified with two lift jets in the center fuselage. Mikoyan divided his team into two groups- one group did further studies of the swing-wing design and the other group studied the same design, but with delta wings and lift jets instead of the swing wing. Mikoyan's nephew, Vano Mikoyan, was placed in charge of both teams. As jet lift had already been flight tested, it was agreed to fly that version first while the other team refined its work on the swing-wing version. The jet lift version was designated in-house as izdeliye 23-01 (a reuse of the Ye-7's designation) and had a single Khachaturov R-27F afterburning turbojet as the main cruise engine with 11,400 lbs of thrust and two Kolesov RD36 lift engines mounted in the mid-fuselage and angled 5 degrees forward from vertical to provide a slight forward thrust vector. A dorsal aft-hinged door opened up during flight along with auxillary inlet doors to provide air for the lift engines which exhausted through a belly-mounted grid of vectorable deflector vanes that could also direct lift engine thrust forward for braking on landing. 

 

Because the new Sapfir radar system was larger than any radar system used previously, a nose inlet was impossible and the 23-01 had half circle lateral intakes with a central shock cone similar to that fitted to the Lockheed F-104 Starfighter and the Dassault Mirage series of fighters. To augment the lift from the delta wing of the 23-01, the flaps were blown with engine bleed air when lowered. The delta wing resembled that of the MiG-21, but was scaled up for the increased size and weight of the 23-01 design. While there was no radar system aboard the 23-01 nor were there any fire control avionics, a 23mm cannon was fitted under the fuselage just aft of the cockpit and dummy K-23 missiles were fitted under the wings (the K-23 had the NATO designation AA-7 Apex and in operational Russian service was designated R-23). The 23-01 prototype was even painted in the light gray color used by the air defense units of the Soviet Air Force and it made its first flight on 3 April 1967. 

The 23-01's flight test program revealed that it flew just as poorly as the MiG-21 STOL demonstrator that proceded it, the Ye-7. Test pilots noted a considerable amount of instability bordering on loss of control on takeoff due to interactions between the lift jets and the wings. On landing, it was found that the exhaust of the lift jets was getting ingested into the main engine, robbing it of power. The only solution was to increase the landing speed, but then this negated any STOL benefit of having lift engines! Pilots expressed concern at what to do in case of the loss of one of the lift engines on takeoff or landing before the wing had generated sufficient lift. At altitude the lift engines were deadweight and it compromised the maneuverability of the 23-01. The short flight test program confirmed Artyom Mikoyan's favoring of the swing wing configuration, but the aircraft continued flying until the 23-01 could be demonstrated to the public at the Moscow Domodedovo air show in July 1967. With its operational color scheme and weapons loadout, the Soviet Air Force announced its designation as the MiG-23PD, giving Western analysts the impression it was a possible production type. In fact, NATO even went as far to assign the 23-01 the code name "Faithless" as a result, believing that jet lift would be a feature of the MiG-23! After the air show, the 23-01 was retired and donated to the Moscow Aviation Institute for maintenance training and subsequently got scrapped. 

The first flight of the world's first production variable-geometry aircraft, the General Dynamics F-111, in December 1964 showed TsAGI's original 1961 report in error and work on the swing wing version of the 23-01, designated in-house by Mikoyan as the 23-11, was increased. In fact, the Mikoyan designers scrutinized every photograph and inflight footage of the F-111 to determine how the Americans had solved problems that TsAGI only 3 years earlier deemed too difficult to overcome with present technology. The 23-11 made its first flight on 10 June 1967 only one month before the STOL 23-01 was unveiled to the public at Domodedovo. The 23-11 became the first production version of the MiG-23, the MiG-23S (S referring to the Sapfir radar) which used most of the fuselage of the 23-01 and the empennage but added lateral box inlets and a new swing wing. NATO would assign the MiG-23 the code name "Flogger".

The flight test program of the MiG-23/23-11 showed that swing wings very closely approached the field performance of the jet lift STOL 23-01. While the 23-01 at a takeoff run of 1,500 feet, the MiG-23 had a takeoff run of 1,800 feet. Landing the 23-01 required 1,100 feet and the MiG-23 could do it in 1,400 feet. In addition, the MiG-23 proved to be a far more versatile design on account of the performance accorded by its variable geometry wings. Nevertheless, the jet lift 23-01 remains an unusual historical aviation curiosity that fooled NATO into thinking it was the production configuration of the MiG-23!

Source: OKB Mikoyan: A History of the Design Bureau and its Aircraft by Yefim Gordon and Dmitriy Komissarov. Midland Publishing, 2009, p255-257. 

The Mikoyan I-320 Interceptor

One of the best aspects of being an avgeek comes when you find out about an aircraft you never knew even flew. I recently got the vastly upgraded edition of OKB Mikoyan and learned about the I-320 two-seat all-weather interceptor. From several different angles it looks a lot like the MiG-17 and it's clearly derived from that aircraft. In the late 1940s the Soviet Ministry of Defense issued a specification for a long-range interceptor- three bids were submitted from the OKBs of Lavochkin, Sukhoi, and Mikoyan. Late to the party but accepted for consideration was also a design from OKB Yakovlev. All of the designs were twin-jet aircraft.

Mikoyan's submission had the internal designation I-320/R-1 and it was designed and built in 1949- in tandem with the development of the famous MiG-15/17 family of jet fighters, accounting for its similarities in general layout. The main difference, however, was that the I-320 was a much larger and heavier aircraft with two crew and two engines. The engines were uniquely mounted in a stepped-tandem arrangement. The forward jet engine was mounted low in the forward fuselage with its exhaust semi-recessed underneath the fuselage just behind the cockpit. The aft engine was mounted in the aft fuselage just behind the wings much in the same way as the single engine of the MiG-15/17 with its exhaust at the end of the fuselage under the cruciform tail. The large nose intake had two splitters instead of the one intake splitter of the smaller MiG-15/17. The central portion of the nose intake fed the forward engine and the two lateral portions fed ducts that ran on each side of the cockpit to the aft engine.

The pilot and radar operator sat side-by-side under a broad cockpit canopy. This way both crew could scan the radar scopes and the radar operator had full dual controls and could relieve the pilot on long air patrols. The Toriy-A radar was mounted in a bullet-shaped projection above the nose intake and two 37mm cannons flanked the intake on each side of the nose.

Powered by two Klimov RD-45 engines of 5,000 lbs thrust, the I-320 was rolled out in April 1949 and made its first flight that month. Mikoyan's flight tests continued through 1950 and the aircraft was then delivered to the Soviet air defense forces, the PVO, for state acceptance and combat testing. The first version of the I-320, the R-1, didn't get accepted due to some stability issues at high speeds. Following the R-1 version in flight testing was the R-2 version which had more powerful Klimov VK-1 engines (the VK-1 was an upgraded and more reliable version of the earlier RD-45 engine used on the R-1 variant), aerodynamic refinements, and a third 37mm cannon mounted under the nose. With better performance in testing with the PVO, the R-2 got a more advanced Korshun radar to replace the earlier Toriy-A unit. During operational testing in 1951, a 37mm shell exploded in the feed belt and damaged the R-2's nose.

Mikoyan took the opportunity to try and rectify some of the stability issues dogging the I-320 as the R-2 was being repaired. As a result, it was redesignated as the R-3 version. The repaired and upgraded aircraft made its first flight on 31 March 1951 and it would make 60 flights during state acceptance trials for a total of nearly 46 flight hours. However, the I-320 never went into production as its performance was deemed inadequate. With the cancellation of Lavochkin's design, the La-200, and the crash of the Sukhoi entry, the Su-15 (the first use of the designation, not to be confused with the later and totally different Su-15 "Flagon" interceptor), Yakovlev's late entry won the competition and went into production as the Yak-25. For a while, though, Mikoyan retained the R-1 and the R-3 versions of the I-320 interceptor to develop instrument landing systems for the Soviet Air Force.

Source: OKB Mikoyan: A History of the Design Bureau and its Aircraft by Yefim Gordon and Dmitriy Komissarov. Midland Publishing, 2009, p127-130.

The VDRK Motor Compressor Engine: The Sort-of-a-Jet

As 1944 began, Soviet aeronautical experts were already filtering through information of successful flight tests of British and American jet aircraft and the impending service introduction of rocket- and jet-powered aircraft in the Luftwaffe. The Soviet GKO (State Defense Committee- a wartime organization that ran the Soviet Union during the Second World War), headed by Stalin, quickly concluded that the different efforts by engineers doing research on jet propulsion at the time needed to be consolidated under one organization, the NKAP (People's Commissariat for Aviation Industry). By March of 1944 officials of the NKAP were ready to present Stalin proposals to accelerate Soviet aeronautical technology to match that of the Luftwaffe, but most importantly to keep up with the British and the Americans. Semyon Lavochkin, Artyom Mikoyan, and Pavel Sukhoi of their respective design bureaus (called OKBs) were instructed to develop jet fighters as a matter of national security. At the time, though, jet engine technology in the Soviet Union wasn't as far advanced as that of either the Germans or the British and American teams. Both Sukhoi and Mikoyan went looking for an alternative with more technical maturity to speed the development process of their candidate designs. 

If we roll back the clock a bit to 1942, a special section within the famous aeronautical and hydrodynamics institute, TsAGI, in Moscow, was set up to explore jet propulsion. One TsAGI engineer, Ghenrikh Abramovich, had devoted time to study the use of a piston engine to drive a separate compressor that would force air into a combustion chamber like a jet engine, only the thrust from the combustion chamber was used purely for propulsion and would not be used to drive a turbine as was the case with a jet engine. Piston engine supercharger technology at the time was mature enough that work on what was called a "motor compressor engine" was simply a derivation of that work as many Allied engines used exhaust driven turbines to compress air for the supercharger to allow piston engines to operate at high power levels at higher altitudes. A motor compressor engine simply used a drive shaft to drive the compressor instead of exhaust gases. 

(I should note here that some versions of the Pratt & Whitney R-4360 Wasp Major radial engine actually had a shaft-driven supercharger inside the engine. This would later lead to the VDT (Variable Discharge Turbine) which will be the subject of a future entry on this blog.)

The intended production version of the motor compressor engine was designated the VDRK. The piston engine drove an axial compressor in the VDRK with then not only drove compressed air like a supercharger to the engine, but also served the radiators. But the air was then passed into a combustion chamber mixed with fuel and ignited, allowing the VDRK's exhaust to act as a rudimentary jet booster. Both Sukhoi and MiG design bureaus selected the Klimov VK-107 liquid-cooled inline engine which via an auxiliary gearbox, drove the VDRK booster. At 23,000 feet the VDRK not only boosted the speed of the aircraft, it also boosted the power of the Klimov engine from 1,650 hp to 2,500 hp, making it an effective supercharger as well. An air inlet below the Klimov inline engine fed the VDRK. On takeoff, 95% of the piston engine's power drive the propeller. But once at altitude, a clutch was engaged which shifted some of the power to a step-up gearbox to drive the VDRK. The main engine's radiator was directly behind the axial compressor with a small diverter duct to feed compressed air to the engine like a conventional supercharger. The air that wasn't fed into the diverter was then mixed with fuel sprayed from seven nozzles and ignited by sparkplugs. At this point in the engine, the duct expanded to form a combustion chamber made of stainless steel to withstand the heat. At the very end of the fuselage a two part eyelid-like nozzle modulated the exhaust flow like a rudimentary adjustable engine nozzle. 

In May 1944 the MiG bureau began work on their design using the Klimov/VDRK engine, the aircraft being designated I-250. The NKAP instructed MiG to have two prototypes ready for testing as high-altitude interceptors by late winter 1945. The specification called for the I-250 to be able to reach 16,400 feet in 4.5 minutes (less if not using the VDRK), a maximum speed of 502 mph (again, less if the VDRK was not engaged) and a service ceiling of 39,000 feet with the VDRK engaged. The armament was one 23mm cannon and two 12.7mm machine guns. By October the mockups were being reviewed by the NKAP and engine testing at TsAGI showed that the combustion chamber of the VDRK needed to strengthened. Given the urgencies of war, prototype construction had already started with the first flight of the I-250 on 4 April 1945 and on its third test flight, the VDRK was engaged for the first time. The second I-250 prototype was completed the following month, flying for the first time on 25 May 1945. 

However, technical issues with the VDRK booster kept popping up and in July 1945 the first I-250 was lost with its test pilot when G-limits were exceeded and the tailplane failed. By this point the NKAP had concluded that the future of fighter aircraft lay with pure jet engines, but that the I-250 project was to continue to provide an aircraft that would give pilots experience in high speed flight. Sukhoi's Su-5 design was canceled as inferior to the MiG I-250 and a pre-production batch was ordered at the end of July for ten aircraft to be delivered at end of December. Power failures, winter fuel rationing and mounting technical challenges with the construction of both the aircraft (sometimes designated MiG-13) and the Klimov/VDRK engine meant that only one aircraft was built by the deadline. As a result, Stalin had the head of the NKAP arrested and a committee formed to investigate the reasons for the delays. Numerous directors, from the aircraft factory to the engine factories involved, were severely reprimanded (I cringe to think what a Stalinist reprimand involved) and the plant manager where the VDRK was built and his quality control manager were arrested and charged with industrial sabotage. 

Despite this, another FIFTY aircraft were ordered in February 1946 and the first pre-production batch had yet to be completed let alone start State certification trials! A new deadline for July 1946 was set and when this deadline failed to be met, 24-hour shifts were imposed on all the manufacturing facilities involved in MiG-13 production. Seven airframes were completed, but the VDRK engines continued to be source of technical obstacles. It was already August 1946 when the eighth aircraft from the original ten-aircraft order first flew and it promptly suffered an engine fire. It wasn't until September of that year that the first aircraft were delivered to the Air Force for acceptance trials. 

Oddly enough, at a meeting on 29 November 1946 chaired by Stalin himself, the pure jet MiG-9 and Yak-15 would be the main jet fighters of the Soviet Air Force and with the astounding prospect of getting superior jet engines and technical assistance from Britain, there would be no future for motor compressor engines. Despite this, Stalin instructed that acceptance trials for the I-250/MiG-13 continue and that production capacity be retained. By May 1947 the acceptance trials were in full swing and the Klimov/VDRK combination was FINALLY operating at specification. Since the Soviet Air Force was no longer interested in the aircraft, the naval air arm, AVMF, was convinced to accept the aircraft as an escort fighter for torpedo bombers. State acceptance trials were to continue under AVMF auspices at Riga on the Baltic coast, but continuing reliability problems and bad weather meant that only six flights had been completed by January 1948 and the VDRK had only been engaged once, and that one time was only 1.5 minute ground run. On 3 April 1948 the I-250/MiG-13 was declared as having failed its State acceptance trials and the aircraft faded into historical obscurity. By that time, the prototype of the MiG-15 jet fighter had already taken place in December 1947, powered by a license-produced Klimov version of the Rolls-Royce Nene engine obtained openly and with the approval of the British government!

Source: OKB Mikoyan: A History of the Design Bureau and its Aircraft by Yefim Gordon and Dmitriy Komissarov. Midland Publishing, 2009, p35-39.

One of the unique features of the Mikoyan MiG-23/27 Flogger fighter aircraft is that compressed air for the pneumatic systems is stored inside the main undercarriage legs and axles. The main pneumatic system fed off a 12.1 liter "bottle" inside the right undercarriage leg to operate the cabin pressurization, canopy operation, moving the sliding panels that cover the gaps on the variable-geometry wings, the main wheel brakes, main fuel valve, braking parachute deployment, activating the emergency drive for hydraulic system and closing the air vents in the avionics bays. A smaller 1.75 liter "bottle" inside the right wheel axle supplied compressed air to the radar bay and avionics heat exchanger which used fuel as coolant.

A 12.1 liter "bottle" in the left main undercarriage leg supplied compressed air for emergency lowering of the landing gear, folding of the ventral fin and operation of the brakes. A smaller 1.75 liter "bottle" in the left wheel axle supplemented the emergency systems on the Flogger. The main valve to fill the compressed air circuits in both main landing gears was located in the left main wheel well.

Source: MiG-23/27 Flogger- Soviet Swing Wing Fighter/Strike Aircraft by Yefim Gordon and Keith Dexter. Midland Publishing/Aerofax, 2005, p52.