AIM-7 Sparrow

U.S. Navy photo by Photographer’s Mate 3rd Class Joshua Karsten. (041108-N-8704K-008)

The AIM-7 Sparrow air-to-air missile is a supersonic boost-glide missile capable of engaging both aircraft and missiles in all weather conditions. The AIM-7 Sparrow missile is a medium-range air-to-air missile with a max range of at least 16 NM (30 km) for the AIM-7E and at least 38 NM (70 km) for the AIM-7F and AIM-7M. The all-weather capability comes from the missile being radar-guided, more exactly SARH (semi-active radar homing). This means that the seeker of the Sparrow relies on the AN/AWG-9 painting the targets for it and following the radar emissions being reflected off the target.

The F-14 can carry the AIM-7E, AIM-7F, and AIM-7M on four dedicated recesses on the aircraft fuselage and one each on the glove pylons.

Apart from the various improvements to the missile range, seeker, and warhead, the major difference between the different versions is that the AIM-7F and newer missiles can also be guided via pulse doppler illumination in addition to CW as opposed to only CW.

Missile Preparation

Before launch, the AIM-7 missiles need to be prepared by the selection of the MSL PREP-ON pushbutton on the pilot ACM panel. This commands the WCS to start missile preparation for the AIM-7 and AIM-54.

In the case of the AIM-7, the WCS applies electrical power to the missile to pre-heat the electronics and gyros. It also injects CW radar video from the radar to the missiles via an emitter on the aft end of the rail to a receiver at the aft end of the missile. This video is used to tune the AIM-7 missile to the selected CW frequency on the RIO DDD panel. When the individual missiles are tuned and ready, the corresponding missile status windows turn white to indicate a ready missile.

Launch Modes

The two available launch modes for the AIM-7 on the F-14 are the normal mode and the boresight mode. To select the AIM-7 for launch, the pilot selects the SP/PH (sparrow/phoenix) position on the stick weapon selector. Selection of which Sparrow to launch is done automatically by the WCS.

Depression of the weapon selector switches from SP to PH and vice versa. If an STT target is available, the WCS will automatically use the normal mode for launch unless BRSIT (boresight) is selected on the MSL MODE (missile mode) switch on the ACM panel. In all other cases, the boresight mode will be used.

Normal Mode

As the normal mode is used to engage a target tracked in STT, the WCS is capable of using both CW and pulse doppler for guidance. When using CW in the normal mode, the AN/AWG-9 radar uses a dedicated CW antenna to spotlight the tracked target more directly than via the flood antenna. While CW is the normal guidance mode for all AIM-7 variants, it is possible to select the pulse doppler guidance mode instead when using the AIM-7F and AIM-7M missiles.

This is done on the RIO's armament panel with the MSL OPTIONS switch by setting it to SP DP (sparrow doppler). When selected, this causes the WCS to guide the Sparrow missiles using pulse doppler illumination instead.

Regardless of guidance mode, the WCS calculates the missile LAR (launch acceptance region) and displays the missile launch ranges on the VDI and TID. The HUD shows the target diamond and current target range, Rmin and Rmax, while the VDI, DDD, and TID display the attack guidance symbology as well as the above-mentioned missile LAR indications.

Boresight Mode

The boresight mode uses the CW flood antenna on the AN/AWG-9 radar and will cause the missile to track the strongest target return within the flood area. In addition to when launched in boresight mode, the radar will also switch to flood mode when a target is lost, either before launch or after launch, enabling the pilot to try and save the shot by keeping the target within the flood area.