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Integration of a more complex solution for over-the-horizon ATC communication via the ARC-210 radio did not increase the share of mishaps due to communication hardware and software failures for the RQ-1.
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The trends in the MQ-1/Predator and RQ-2/Pioneer failures due to Power/Propulsion are very similar. The share is in the 20-30 percent range (23 percent and 29 percent, respectively) for the early, A-model systems, but doubles to the 50 percent range (53 percent and 51 percent respectively) in the later models. MQ-1 Block 30 upgrades address this issue.
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The trends in the MQ-1/Predator and RQ-2/Pioneer failures due to Flight Control issues are also very similar. From the A-model to the B-model, the share decreases by over one-half (39 percent to 23 percent and 29 percent to 15 percent, respectively). This may be attributed to a better understanding of the aircraft aerodynamics and flight control as well as self-imposed flight restrictions for certain operating environments.
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Despite any noticeable shifts of failure modes among the aircraft from the early to the late model, the reliability trends for the UA continued to be positive. This indicates an awareness of, and attention to, system deficiencies on the part of the designers and operators.
The average values for the failure modes for all five subsystems are presented in Figure H-2. This view of the Predator, Pioneer, and Hunter UA fleet provides a good introduction into a similar perspective on foreign UA reliability.
APPENDIX H – RELIABILITY
Page H-4
UAS ROADMAP 2005
Power/Prop 38%
Flight Control Comm Human/Ground Misc
FIGURE H-2. AVERAGE SOURCES OF SYSTEM FAILURES FOR U.S. MILITARY UA FLEET (BASED ON 194,000 HRS).
Power/Prop Flight Control Comm Human/Ground Misc
28%
FIGURE H-3. AVERAGE SOURCES OF SYSTEM FAILURES FOR IAI UA FLEET (BASED ON 100,000 HRS).
Israeli Defense Forces have also accumulated over 100,000 hours of operational flight experience with their UA. The manufacturer of most of these UA, Israeli Aircraft Industries (IAI), has documented the causes of failures across the past 25 years of this experience and made recommendations for improving reliability based on this analysis. Of current U.S. UA systems, both the Pioneer and the Hunter originated as IAI designs, and the Shadow evolved from the Pioneer’s design. For these three reasons, any examination of U.S. UA reliability would be incomplete without examining the reliability of their Israeli counterparts and predecessors.
The data trends derived from the U.S. UA operations summarized in Figure H-2 are remarkably similar (within 10 percent) to that of the Israeli UA fleet for all failure modes. With twice as many flight hours for the U.S., it is not surprising that the share of failures due to flight control is less. Given that the IAI data is also based on a substantial number of flight hours as well, one can argue that the U.S. is facing the same technical and operational problems of other operators. Furthermore, because manufacturing techniques and supply quality differ from one country to the next, it is interesting to ask the question “Why are the failures modes still similar?” One answer points to external factors and the operating environment itself, including weather and the low Reynolds number flight regime.
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