The Evaluation of the Low Probability of Intercept Altimeter (LPIA) and its Impact on EA-6B Operations

The purpose of this study was to evaluate the performance of the Low Probability of Intercept Altimeter (LPIA) Radar Altimeter (RADALT), which was selected to replace the AN/APN-194 RADALT, as installed in the EA-6B Prowler and conclude how the new system will impact the tactical operation of the EA-6B aircraft if allowed to proceed to and pass the operational phase of testing in its current status.

The LPIA was selected to replace the APN-194 as part of the overall EA-6B aircraft Block III test program in order to comply with the Chief of Naval Operations’ (CNO’s) mandate to install the Ground Proximity Warning System (GPWS) in all U. S. Navy tactical aircraft. Although other options were initially available, Program Manager Aviation (PMA)-209, the avionics program manager, insisted LPIA be used and classified the equipment as “off-the-shelf.” They believed it would require minimal testing since it had already been successfully tested and installed in two other fleet platforms (P-3 and C-2). No mention was made of the problems discovered or the failed attempt to integrate the system into the F/A-18 Hornet and S-3 Viking aircraft.

The initial evaluation was originally scheduled for approximately 12 flight hours, however two test analyze fix periods of that magnitude have already been conducted on the LPIA and several deficiencies have been discovered. Currently, in the opinion of the author, the LPIA is unsuitable to support the EA-6B’s mission needs. PMA-234, the EA-6B Program Manager has decided to give British Aerospace Engineering (BAE), the prime contractor, and PMA-209 one more opportunity to fix the deficiencies prior to the start of Block III flight test.

The author concludes that if the LPIA is allowed to proceed in its current condition and is introduced to the fleet, it would have detrimental effects on the EA-6B’s operational capability. If the system fails developmental testing (DT), an alternate means to supply height above the terrain to GPWS will have to be explored. The author recommends specific improvements, which may produce an effective system that is suitable for EA-6B operations.