The Society of Flight Test Engineers 




Maj. Zach A. McCarley
Experimental Test Pilot, Naval Air Weapons Center, CA
Lt. Col. Timothy R. Jorris, Ph.D.
Director, Hypersonic Combined Test Force , 412th Test Wing, Edwards AFB, CA

  The F/A-18 E/F in the US Navy’s (USN) inventory is currently configured with the M-61A2 Vulcan cannon. The M-61A2 is the aircrafts internal gun system and has a rotating cluster of six barrels that fires 20-mm electrically-primed ammunition at 6,000 or 4,000 rounds per minute. A variety of Armor-Piercing Incendiary (API), High Explosive Incendiary (HEI), and training rounds are available. It was recently reported that the F/A-18 strafing accuracy seemed less than anticipated in certain combat scenarios. The subject matter experts identified several possible contributors to the suspected targeting error. Four factors were identified; each had two levels or options available during a given strafing run. The factors were Ammunition, either M56/M55 or PGU-28/PGU-27; Software, either Legacy or Upgraded; Altitude Source, either radar or system computed; and Radar, either APG-73 or APG-79. The chief pilot elicited the help of the statistics expertise at Edwards AFB. Using Design of Experiments (DOE), they collectively developed a matrix of factors to identify the contributors to any errors. Incidentally, the number of flights determined with DOE was substantially less than the original estimates. Wind was another strong potential influence on accuracy; however, since winds could not be controlled, they were recorded and input into the statistical analysis.
  The results found statistically significant contributors to strafing accuracy. These statistically significant results are compared against operationally significant error values. Flight test analysis results are presented, and the data collection lessons learned will be addressed since they made the final analysis possible by eliminating several sources of measurement errors. The presentation will also address the future actions being taken as a consequence of collecting such compelling and supportable evidence via statistically defensible flight test results.