Unsung Hero: The AIM-7 Sparrow [Part I]

AIM-7 Sparrow: Table of Contents

Despite the growing popularity of Cold War servers, the vast majority of players see the AIM-120 AMRAAM as the iconic western missile of DCS.
The AMRAAM, a still upgraded and updated product of the 80s, benefitted either directly or indirectly by the advancements of its two illustrious predecessors: the familiar AIM-54 Phoenix, and the AIM-7 Sparrow. In a sense, the AIM-120 joins parts of the capabilities of the AIM-54, in the AIM-7’s size.

If the AIM-54 Phoenix is nothing new on these pages, the AIM-7 has never had a chance to shine. In DCS, and in a funny and twisted parallel, in real life, its development has seen highs and lows, but it is finally in a shape stable enough to make it worth studying.

From a Problematic Genesis…

The AIM-54 Phoenix is an old missile, developed in the ’60s. But if the “54” is old, the “7” is prehistory. The Sparrow, in fact, comes into the world to satisfy the requisites of development programs of the 40s, entering service in the mid-50s.

The Navy and the Air Force entered the 1960s in very similar positions. Both services had a new fighter aircraft – the McDonnell Douglas F-4 Phantom II. Both services tactically emphasized long-range intercept using the AIM-7 Sparrow III missile, and both believed that the greatest threat came not from enemy fighters, but rather from long-range Soviet bombers.
The late 1950s emphasis on intercept and the emerging tactical nuclear strike mission not only drove fighter aircraft design but also fighter pilot training, which saw less and less need for retaining aerial-combat or dogfighting skills.

Brad Eldward – TOPGUN The Legacy. Page 85.

The first Sparrow was a beam-rider (think about the 9K121 Vikhr operated by the Ka-50), and was initially conceived as an anti-bomber missile to fend off the Soviet hordes of the Cold War.
Comes the Vietnam War, and the Sparrow’s wings were shattered. The performance of the AIM-7E was disappointing at best, achieving a hit rate of 15.8%, and a kill rate of 9.2%.
All sorts of justifications were attributed to the debacle: climate, mediocre maintenance, lack of training, poor tactics, no IFF. Whatever the actual reason was, or the combination of reasons were, the results were unsatisfactory.
Fast-forward a decade and the Iranian managed to achieve slightly superior successes, doubling the positive outcome of the Americans in Vietnam.

While the AIM-9 Sidewinder is usually described as the best short-range air-to-air missile of the war, Iranian experience with the AIM-7 matched that of US pilots in Vietnam, who found that the weapon sometimes functioned well, but on other occasions was totally useless. But unlike American pilots, the Iranians never used the AIM-7 in dogfights. It was employed exclusively in medium-range engagements, being fired from a forward aspect at a range of 12 km (seven miles). While most pilots remained unimpressed with the AIM-7, careful handling and precise pre-flight checks assured a kill probability of more than 20 per cent – twice that achieved in Vietnam.

Tom Cooper, Farzad Bishop – Iranian F-14 in Combat. Page 80.

…to a Brilliant Future (Past)

As the dust scattered by the Iranian-Iraqi war of the 80s was slowly settling, Saddam Hussein decided to stir the waters of the Gulf once again. This time by invading the adjacent State of Kuwait. The year is 1990.

The following conflict sees the complete air and ground domination by the coalition forces, led by the Americans, with the secondary contribution of British, French, Italian, Egyptian, Saudi, and many other forces.
The first stages of the war are dominated by a massive air campaign (watch with video by The Operations Room, it really deserves it). At the end of the War, just a few months later, the Sparrow has redeemed itself, scoring an impressive 68.2% hit rate, and a kill rate of 59.1%.

The AIM-7 Sparrow is a medium range, all-aspect, all-weather, semi-active radar guided missile. In addition to its air intercept role, Sparrow variants have been utilized as air-to-surface and surface-to-air weapons since the missile’s inception in 1946. Unlike many of its predecessors, the current Sparrow (AIM-7M) is a reliable and highly lethal weapon.

P-825/02 p.101

For comparison, the AIM-120 was employed for the first time in December 1992, and so far, has achieved a kill ratio between 40% and 50% (depending on the sources).

Physical Characteristics

AIM-7 Sparrow in DCS

The AIM-7 is considered a poor missile, as players are used to the performance of the AIM-54 and the AIM-120 (or non-NATO equivalents) in non-realistic or non-restricted servers. In the appropriate time-frame, instead, it is still a valid missile, although sometimes inferior to similar non-NATO solutions.

The Sparrow implemented for the F-14 has been, for a prolonged period, different from the version used in other modules made by Eagle Dynamics. Recently, some technical blockers have been solved, and the F-14 is using the same implementations used by the Hornet and the F-15.
Since the F-14 has been operative for over 30 years, its AIM-7s have seen several upgrades. The versions available in DCS are:

• AIM-7E-4: supported by the F-14, but not available in-game yet (02/10/2022).
• AIM-7F: entered service in 1976, it had a dual-stage rocket motor, solid-state electronics and larger warhead. It has a much better effective range than the AIM-7E, and it is the first AIM-7 to support Pulse Doppler guidance;
• AIM-7M: entered service in 1982 with a new monopulse seeker, better EMC resistance and other features. Its combat record during the Gulf War drastically changed how the AIM-7 was perceived by the general public and military enthusiasts;
• AIM-7MH: similar to the AIM-7, it features numerous improvements, such as Home-On-Jam (HOJ) and lofting capability;
• AIM-7P: produced since the 1987, the AIM-7P is a late variant, featuring a new radar fuse and improved guidance, on top of a new uplink for mid-course guidance.
  Note: it is unclear if any of such features are implemented in DCS.

AIM-7 Guidance

The AIM-7 Sparrow can be boresighted or launched in STT mode, both PSTT and PDSTT.
The default launch method uses a Continuous Wave antenna to guide the missile (for both boresight and STT). Since the introduction of the AIM-7F, the Sparrow can be guided using the Pulse Doppler illumination, hence increasing its potential range and reliability against Chaffs (in theory, in DCS it is another matter), whilst introducing two weak points in the form of notching (MLC) and absence of Doppler shift (ZDF).
To select PD guidance, the RIO actions the MSL OPTIONS switch, selecting “SP PD”.

When the AIM-7 Sparrow is employed in boresight, the CW antenna is used and the missile homes on the strongest target return in the flood area.

The Missile Speed Gate (MSL SPD GATE) knob offers some options for the employment of the AIM-7 in real life. However, the knob is not modelled as it is beyond the fidelity of the air-to-air missiles in DCS, at the moment.
In real-life, these are the effects of the selector switch:

• WIDE: only used with the AIM-7 and there is no radar lock with the target. The PD frequency sweeps the entire missile radar frequency range;
• NAR: used with the AIM-7, but only the Sparrow’s frequency range are swept;
• NOSE, NOSE QTR, TAIL QTR and TAIL are used to inform the WCS that the target is locked on a position matching the switch.

DCS Limitations

Unfortunately, the MSL OPTIONS switch, presently, is not fully implemented. The reason is the missile guidance logic in DCS, which relies of the launching platform to determine whether lock is achieved and maintained or not. Thus, as long as the F-14 tracks the target, then the missile is guiding. Therefore, there is no point in using the SP PD option of the MSL OPTIONS switch right now, as it has no effect on the guidance.
However, since the tracking depends on having a radar lock, the player is left with the option of choosing between PSTT and PDSTT. Since Pulse can be effortlessly used even in look-down situations and PDSTT suffers from ZDF, Pulse mode seems like the most efficient radar mode at the moment.
On the other hand, switching from TWS / RWS to PDSTT is much simpler, as the return can be captured directly from the DDD. A good RIO can also somewhat offset the ZDF, and switching MLC to off, prevents notching.

Loft Control and Employment

Recent versions of the AIM-7 feature an automatic loft trajectory when the distance is greater than a certain amount. The effect is similar to the well-know AIM-54: post launch, the missile climbs, trading speed for altitude as the rocket motor burns. Later, it uses the altitude accumulated to maintain energy and manoeuvrability as it dives onto the target.

The following list is a quick recap of how lock, trajectory, and guidance can be maintained or manipulated:

• Normal mode (PSTT, PDSTT): the loft trajectory depends on the missile itself and the range, and the radar guides the missile to the target.
  7MH, 7P loft automatically. 7M, 7F and older versions fly straight towards the target.
  The radar mode used to obtain the lock does not matter (e.g. VSL, PD/P STT from the backseat, etc);
• “Assisted” Loft: by changing the pitch of the F-14, the loft trajectory can be exaggerated if present, or forcibly enabled in the 7F and older;
• ACM Mode (front seat): the flip cover disables any sort of loft, no matter the range or the type of Sparrow used. It also prevents the Radar Intercept Officer from launching the missile;
• Boresight Mode (front seat): the AIM-7 can be launched in flood mode if the pilot selects the appropriate function. The AIM-7 flies towards the strongest return in its scan area;
• TCS guided: the radar can be slaved to the TCS, thus maintaining the target illuminated and the missile guidance even when the STT lock is broken.

The effects of the three forms of loft control and their effects along different ranges, altitude, speed and other factors are much more complex than expected, and will be discussed in the next parts of this study.