Lessons Learned-Realities and Recommendations

Unmanned research vehicles have proven useful for evaluating new aeronautical concepts and providing precision test capability, repeat­able test maneuver capability, and flexibility to alter test plans as nec­essary. They allow testing of aircraft performance in situations that might be too hazardous to risk a pilot on board yet allow for a pilot in the loop through remote control. In some instances, it is more cost – effective to build a subscale RPRV than a full-scale aircraft.[1047] Experience with RPRVs at NASA Dryden has provided valuable lessons. First and foremost, good program planning is critical to any successful RPRV project. Research engineers need to spell out data objectives in as much detail as possible as early as possible. Vehicle design and test planning should be tailored to achieve these objectives in the most effective way. Definition of operational techniques—air launch versus ground launch, parachute recovery versus horizontal landing, etc.—are highly dependent on research objectives.

One advantage of RPRV programs is flexibility in regard to match­ing available personnel, facilities, and funds. Almost every RPRV project at Dryden was an experiment in matching personnel and equipment to operational requirements. As in any flight-test project, staffing is very important. Assigning an operations engineer and crew chief early in the design phase will prevent delays resulting from opera­tional and maintainability issues.[1048] Some RPRV projects have required only a few people and simple model-type radio-control equipment. Others involved extremely elaborate vehicles and sophisticated control systems. In either case, simulation is vital for RPRV systems development, as well as pilot training. Experience in the simulator helps mitigate some of the difficulties of RPRV operation, such as lack of sensory cues in the cock­pit. Flight planners and engineers can also use simulation to identify significant design issues and to develop the best sequence of maneu­vers for maximizing data collection.[1049] Even when built from R/C model stock or using model equipment (control systems, engines, etc.), an RPRV should be treated the same as any full-scale research airplane. Challenges inherent with RPRV operations make such vehicles more susceptible to mishaps than piloted aircraft, but this doesn’t make an RPRV expend­able. Use of flight-test personnel and procedures helps ensure safe oper­ation of any unmanned research vehicle, whatever its level of complexity.

Configuration control is extremely important. Installation of new software is essentially the same as creating a new airplane. Sound engineering judgments and a consistent inspection process can eliminate potential problems.

Knowledge and experience promote safety. To as large a degree as possible, actual mission hardware should be used for simulation and training. People with experience in manned flight-testing and develop­ment should be involved from the beginning of the project.[1050] The criti­cal role of an experienced test pilot in RPRV operations has been repeat­edly demonstrated. A remote pilot with flight-test experience can adapt to changing situations and discover system anomalies with greater flex­ibility and accuracy than an operator without such experience.

The need to consider human factors in vehicle and ground cock­pit design is also important. RPRV cockpit workload is comparable to that for a manned aircraft, but remote control systems fail to provide many significant physical cues for the pilot. A properly designed Ground Control Station will compensate for as many of these shortfalls as possible.[1051] The advantages and disadvantages of using RPRVs for flight research sometimes seem to conflict. On one hand, the RPRV approach can result in lower program costs because of reduced vehicle size and complexity, elimination of man-rating tests, and elimination of the need for life-support systems. However, higher program costs may result from a number of factors. Some RPRVs are at least as complex as manned vehicles and thus costly to build and operate. Limited space in small airframes requires development of min­iaturized instrumentation and can make maintenance more difficult. Operating restrictions may be imposed to ensure the safety of people on the ground. Uplink/downlink communications are vulnerable to outside interference, potentially jeopardizing mission success, and line-of-sight limitations restrict some RPRV operations.[1052] The cost of designing and building new aircraft is constantly rising, as the need for speed, agility, stores/cargo capacity, range, and survivability increases. Thus, the cost of testing new aircraft also increases. If flight-testing is curtailed, however, a new aircraft may reach production with undiscovered design flaws or idiosyncrasies. If an aircraft must operate in an environment or flight profile that cannot be adequately tested through wind tunnel or computer simulation, then it must be tested in flight. This is why high-risk, high-payoff research projects are best suited to use of RPRVs. High data-output per flight—through judicious flight planning—and elimination of physical risk to the research pilot can make RPRV operations cost-effective and worth­while.[1053] Since the 1960s, remotely piloted research vehicles have evolved continuously. Improved avionics, software, control, and telemetry sys­tems have led to development of aircraft capable of operating within a broad range of flight regimes. With these powerful research tools, scientists and engineers at NASA Dryden continue to explore the aeronautical frontier.