Masters Theses

Date of Award

5-2006

Degree Type

Thesis

Degree Name

Master of Science

Major

Aviation Systems

Major Professor

Robert B. Richards

Committee Members

Charles T. N. Paludan, George W. Masters

Abstract

Flight clearance for carriage and release of a weapon on board an aircraft is a complex process, and involves myriad tests in order to first establish a flight envelope within which separation testing may commence. Though the author was also integrally involved in the air worthiness testing that immediately preceded AGM-154A Joint Standoff Weapon (JSOW) separation and launch testing on the F/A-18 Hornet, this thesis will focus exclusively on those latter elements.

Developmental testing to establish safe separation for jettison and launch envelopes included fit checks, ground jettison tests, in-flight jettison tests from both outboard and inboard aircraft weapons stations and initial launch testing to establish the starting point for follow-on weapons systems testing. These tests began in early 1994, with the first JSOW jettison flight event happening on 8 March 1994 and the first launch on 13 December 1994. Though the test program is now dated, the analysis of the methodology successfully used in this program is as pertinent today as it was in 1994. Test methods discussed in this document remain the standard for ordnance separation testing, and review of how those methods were applied to the Joint Standoff Weapon test program ten years ago may still provide valuable insight to any organization attempting to discern the safest, most cost-effective method for conducting ordnance separation testing in modern test programs. The purpose of this thesis is to clearly document and assess the iterative flight test methodology used throughout the JSOW test program, and to also document in detail and draw conclusions based upon the results of the jettison and launch separation flight test program.

The desired F/A-18C/D launch envelope to be cleared in this case was 0.60 to 0.95 Mach, +10 to -45 degrees pitch angle and 200 ft AGL to 30,000 ft MSL. Separation testing consisted of both jettison and launch testing. As launch releases were predicted to exhibit better separation characteristics, the test matrix built up from the most benign to the most severe jettison condition, thereby clearing the launch envelope along the way. Once jettison testing was completed, a demonstration of the launch release at the most severe jettison condition was to be conducted to verify JSOW safe separation characteristics in the launch mode. Initial wind tunnel analysis predicted that at the most critical separation condition, the separating store would not only violate the safe release condition requirement of 6 inches clearance, but it would actually impact the fuel tank during separation.

Test methodology was fairly straight-forward – proceed through the flight test matrix until the edge of the envelope, as indicated by unsatisfactory jettison characteristics, was determined, then proceed with launch testing with active control surfaces until unsatisfactory separation characteristics or the full desired envelope were attained. In contrast, data collection, reduction and analysis techniques were extensive and complex. As each JSOW test point necessarily expended a valuable (and expensive) test asset, it was hoped that by investing in a robust separation model based initially upon wind tunnel analysis, and by updating that model with separation data derived from photogrammetric analysis and on-board aircraft and weapon telemetry data during separation, the fidelity of that separation model could be improved and validated adequately such that some planned separation test points could be skipped. The data collection effort included photogrammetric targeting of launch aircraft and weapons, on-board high speed cameras, on-board aircraft and weapon telemetry of multiple parameters, and ground and chase aircraft video.

A total of 15 flights expending 12 JSOW test vehicles were required to clear the jettison envelope for the outboard station between 8 March 1994 and 12 October 1994. Three more flights expending three additional JSOW test vehicles were required to clear the inboard jettison envelope between 18 October 1994 and 1 December 1994. JSOW positional data derived from aircraft and weapon telemetry and photogrammetric analysis were successfully used to update and validate the JSOW separation mode, which enabled the omission of five test points. Separation characteristics were satisfactory for each of the 15 JSOW jettison test points. Separation characteristics of the JSOW in the launch mode matched predictions and met all requirements of the specification for release, thus clearing the flight envelope for follow-on functional testing of the weapon in-flight.

Conclusions are drawn upon the applicability and effectiveness of the flight test methodology, and upon the separation characteristics of the JSOW from the F/A-18 throughout the separation test program. For the high profile JSOW test program, the iterative modeling and simulation used throughout separation testing was extremely effective at improving overall test safety and efficient use of extremely expensive test assets. For future test programs that may benefit from the extensive lessons learned with iterative modeling and simulation using multiple data sources in this test program, the author recommends consideration of methodology similar to that used for AGM-154A JSOW. The author also emphatically recommends use of the Integrated Test Team concept for future test programs, wherever feasible. Finally, the author makes specific recommendations as pertains to the jettison and launch envelopes of the AGM-154A JSOW when released from the F/A-18C/D aircraft.

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