USAF versus NVAF


The United States was deeply embroiled in South East Asia. Addled political considerations dictated that military action must take the form of a carefully graduated response to aggression from North Vietnam, with the result that the USAF and USN went to war with one hand tied behind their backs.

For most of the Rolling Thunder period, the North Vietnamese airfields were inviolate, and the potentially overwhelming American air power was not brought to bear against them. Bombing restrictions were later eased, but the elimination of the NVAF on the ground never seems to have been given any form of priority. This was an error of the first magnitude.

The NVAF made no attempt to wrest air superiority from the Americans. Had they tried, there can be little doubt that they would have failed, with heavy losses. Instead they pursued a policy of what has been termed air deniability, putting up just enough strength to make the USAF and USN divert a considerable amount of effort from their main offensive strength to countering them. Not every American incursion was opposed by the North Vietnamese fighters. At times they responded in strength, while at others they stayed on the ground and left the defensive battle to the SAMs and AA artillery.

In theory, the NVAF opposing the might of the USAF and USN appeared a David and Goliath struggle. The numerically most important North Vietnamese fighter in the early years was the MiG-17. Firmly subsonic in level flight even though fitted with afterburning, its main armament consisted of large calibre cannon. Generally considered pleasant to fly, at speeds above 450kt the controls began to stiffen, giving very high stick forces. At high subsonic speeds this made it very slow in the rolling plane, and thus slow to commence a turn, although being lightly wing loaded it was very agile at more moderate speeds.

The MiG-17s were supplemented by a handful of early MiG-21Cs. This model MiG-21 was claimed to be capable of Mach 2, but in fact the only way in which it could get there was by running itself out of fuel. It was certainly supersonic, but had a low dynamic pressure limit, which restricted its speed below about 5,000ft to Mach 1.05. The American fighters could reach Mach 1.20 with a full head of steam, giving them nearly 100kt advantage.

Like the MiG-17, the MiG-21 was armed with large calibre cannon. It also carried a pair of AA-2 Atoll air to air missiles, as very occasionally did the MiG-17. The radar on both fighters was range-only, and they were thus dependent on close ground control to get them into position and warn them of impending attacks. Both were short legged and fuel-critical. Like the MiG-17, the MiG-21C was lightly wing loaded, and agile throughout the subsonic regime.

The USAF fielded two genuinely Mach 2 capable fighters in the theatre. The Republic F-105D Thunderchief was designed to penetrate modem defensive systems at high speed and medium altitude to deliver tactical nuclear ordnance accurately on target. It carried a 20mm M61 cannon, and a single AIM-9B Sidewinder for self defence. The heaviest single seat, single engined fighter ever to enter service, the Thud, as it was unattractively called, had a very small wing area with a consequently high wing loading, aggravated by the heavy load of conventional ordnance typically carried in Vietnam. While fast in the rolling plane, it turned like a tram. In air combat it had one great advantage; at lower altitudes it was the fastest thing in the sky.

The McDonnell Douglas F-4 Phantom II had been designed as a fleet air defence interceptor, able to patrol far out from the carrier for extended periods, detect intruders at long range on radar, and destroy them from way beyond visual distance. Twin engines improved its survivability; a two man crew coupled with a state of the art radar and avionics fit gave it the ability to detect opponents over forty miles distant under the right conditions, while a full load of eight missiles; four AIM-7D Sparrows and four AIM-9B Sidewinders, gave outstanding combat persistence. The Phantom had good acceleration and a high rate of climb; wing loading was considerably lower than that of the Thud. Neither Phantom nor Thud could match the two Russian designs in a straight co-speed turning engagement in the subsonic regime, but initially there seemed no reason why they should do so. The Thud would not seek aerial encounters; this was not its function. It would attack at high speed; hit the target, then turn around and bug out even faster. Only under exceptional circumstances could it be caught from astern, which was the only real danger area against the weaponry carried by the North Vietnamese fighters, and if anything got in its way it had the firepower to defend itself. The Phantom? Why, that could detect enemy aircraft and kill them with “shoot `em in the face” missiles before they were even aware that they were under attack. It was too fast for its opponents, and its avionics and weapons were too clever. It was a different generation fighter; combat between Phantom and a MiG-17 looked rather like matching a Spitfire against a Sopwith Camel.

Once the shooting started, reality proved rather different from the elaborate theories. Many factors intruded which tended to level out the odds against the NVAF fighters. Supersonic speeds were only attainable with the help of afterburning, but this was so prodigal of fuel that its use had to be sparing. Full ‘burner has been likened to pouring fuel through the necks of eight milk bottles at once. The American fighters operated far from home, and were often hard pressed to get back to a tanker, let alone base. Their pilots were forced to fly with one eye constantly on the fuel gauge. Consequently afterburning could only be used when the need was great; for acceleration, on the attack run, gaining height rapidly, and keeping kinetic energy levels high during hard manoeuvring. The result was that for perhaps 95 percent of the mission, the Mach 2 monsters dawdled along at speeds of between 400 and 450kt, which placed them well within the performance envelope of even the elderly MiG- 17, and ensured that contrary to theory, they could be caught from astern.

Speeds in excess of Mach 1 were the exception rather than the rule, and were generally achieved only briefly during combat, or during the egress from the target area. The NVAF MiGs, short legged though they were, operated mainly within about forty miles of their bases, which made fuel shortage much less of a problem for them. Security of base, which for much of the war was ceded to them without opposition, also helped, as did “Tom Tiddler’s Ground”; a no-go area along the Chinese border, in which the NVAF was safe from American pursuit.

The next levelling factor was in the field of avionics. In a pure fighter versus fighter scenario, the Westinghouse radar of the Phantoms gave tremendous theoretical advantages, allowing their crews to detect oncoming MiGs at ranges far beyond where the NVAF MiG pilots, dependent on visual acquisition, could possibly detect them. Early detection gives the initiative, which in air combat is vital. The difficulty was that a pure fighter versus fighter scenario is a peacetime training exercise, and has little to do with war.

In practice, the North Vietnamese pilots operated under tight Russian style ground control. The respected Soviet commentator. Colonel V. Dubrov, was later to comment that at this stage the controller was of equal importance to the pilot. Suffice it to say that the NVAF fighter controllers, backed by a comprehensive ground radar network, had a broader picture of the air situation than did the Phantom backseater crouched in his cockpit. Operating without the psychological pressure that comes of knowing that at any moment a missile may burst through the windshield, they calmly directed their fighters into favourable attack positions, or warned them of impending danger. As the war progressed they got very good at their work. After all, they had plenty of practice! The austere NVAF fighters were thereby enabled to operate efficiently, even without an effective on-board search radar. Only when close combat was joined were they on their own.

The Phantom crews were almost totally reliant for situation information on their on-board search radar, operated by a rated pilot in the early days, and by a specialist operator later on. This had several drawbacks. Firstly its field of look was limited to a pie shaped scanning area extending about 60 degrees to each side of the nose, and a few degrees in azimuth. While it could be trained up and down, anything outside its volume of scan would not be detected. Its “look-down” capability was limited, and targets could easily be missed in the ground clutter. Its display was of the analogue type, which needed skilled interpretation to get good results. Neither was it infallible.

It is widely known that air combat victories tend to fall to the same handful of pilots; but it is less often appreciated that in South East Asia victories often went to the same machines, regardless of who was flying them. While in a few cases this was because the successful Phantoms were fitted with special gadgets such as Combat Tree, which was a MiG IFF interrogator, the main reason was that the radar and weapons systems of some machines were far more reliable and better performing than the average. Finally, the MiG-17 and 21 were rather small radar reflectors, especially from the frontal aspect, and could only be detected when they were well within the maximum theoretical range of the Phantom radar.

Not only aircraft but weapons systems were another source of levelling the odds. The American AIM-7 Sparrow missile was a semi-active radar homer, guiding on reflected radar emissions from its parent fighter. Before launch, the radar had to be switched into attack mode, or locked on, which meant that it could look only at one target, and did not continue to scan. This gave an effect akin to target fixation in a guns attack where the pilot is aware of nothing but his opponent, and ceases to watch the sky around for further threats. Only when the attack had either succeeded or failed could the radar be used to resume a watch on the surrounding sky. But even as the radar was unable to detect the MiG-21 until it was fairly close, it could not be locked on to such a small target until it was even closer, while for the Sparrow seeker to guide successfully, the range could not exceed more than seven or eight nautical miles. If the Sparrow attack failed, the combined closing speed of the two fighters ensured that the gunless Phantom would be committed to a head-on pass against a gun armed adversary within seconds.

While the radar of the Phantom could detect MiGs at a reasonable distance, it was often unable to identify them, and a couple of “own goals” were scored in the early days of the conflict. This proved a great handicap, as in most situations it made visual identification of targets obligatory. This was further aggravated by having two services raiding the North; the USAF based mainly in Thailand, and the USN operating from carriers on Yankee Station in the Gulf of Tonkin. While attempts were made to keep the friendly forces clear of each other, the occasional overlap was inevitable and the potential for disaster always present. At a stroke the Phantom lost its greatest advantage; the ability to kill from beyond visual range, and this was responsible for forcing it into the close combat arena against lighter and better turning opponents. The gunless Phantom was therefore forced to break a cardinal rule of warfare, and fight on the enemy’s terms.

Close combat quickly highlighted the weak points of the Phantom. It could not turn tightly without bleeding off energy at a very high rate. In its design stage, the accent on performance had caused the cockpit canopy to be faired closely into the fuselage to minimise drag; this also minimised rearward view, thus increasing its vulnerability to attack from behind. Its missiles were not instantly available; they needed a settling period before launch. Nor could they be launched at loadings of more than 2 to 2.5g. Finally they had a minimum range of about half a mile before they armed themselves and began to guide. An opponent inside this distance was safe from attack until Phantoms began to carry guns. Sparrow and Sidewinder had been designed to kill non-manoeuvring targets; the agile NVAF MiGs were not so co-operative, with the result that kill probabilities fell from a theoretical 80 percent to between eight and 15 percent. The Phantom did however have some good solid virtues, and these were put to work in an attempt to redress its failings. Sometimes described as a triumph of thrust over aerodynamics, it was a very powerful machine. When its radar and missiles worked well, it was deadly. It had plenty of scope for improvement; the later slatted wing F-4E with an internal gun and a better radar introduced later in the war enhanced its close combat abilities considerably. Its two man crew could be used to advantage in a visual range fight; the backseater took his head out of the office and became a spare pair of eyes checking the vulnerable six o’clock area, in fact two in every five visual sightings were made by the guy in the back. In so far as tactical circumstances permitted, it became a matter of handling it to its strengths, keeping energy levels high, and avoiding energy depleting hard turns where possible.

Nor was it enough just to defeat the NVAF fighters. The defences were multi-layered, with surface to air missiles and radar directed anti-aircraft artillery. While concentrating on one, it was all too easy to fall victim to another. Watching a SAM curve through the air, even at a distance, was compulsive viewing, but with attention distracted in this way, a MiG could sneak into the vulnerable rear quadrant, launch a couple of Atolls, and depart unnoticed. A tremendous overall effort had to be made to protect the American fighters over enemy territory. These were the force multipliers. Typically, there were tankers to give fuel on both the inbound and outbound legs; Wild Weasel or Iron Hand defence suppression aircraft attacking gun and missile batteries en route; ECM birds Jamming search, gunlaying and missile guidance radars; chaff bombers in the later stages of the war, laying a corridor of chaff through which the strike force could advance undetected; the airborne early warning aircraft orbiting way back and keeping a wary eye open for enemy fighter activity; and a SIGINT (signals intelligence) bird monitoring enemy electronic traffic. As a general rule, the force multipliers outnumbered the bomb carriers, often by as many as two to one, without taking escort fighters and pre-and poststrike reconnaissance aircraft into account. Often more than fifty aircraft were needed although only sixteen of them actually attacked the target. The force multipliers made no direct contribution to the weight of ordnance delivered. This was prodigal of resources, but given the state of the art at that time, and the strength of the defences, it was necessary.

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