Unmanned Aircraft Systems Roadmap 2005-2030 - Federation of ...

UAS ROADMAP 2005
17%
14%
12%
19%
38%
APPENDIX H – RELIABILITY
Page H-5
Power/Prop
Flight Control
Comm
Human/Ground
FIGURE H-2. AVERAGE SOURCES OF SYSTEM FAILURES FOR U.S. MILITARY UA FLEET
(BASED ON 194,000 HRS).
22%
11%
7%
28%
32%
Misc
Power/Prop
Flight Control
Comm
Human/Ground
Misc
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.
MQ-1 and MQ-9/Predator
RQ-1A. The Predator experienced low mission completion rates during its initial deployment in the
Balkans in 1995-1997. While the primary causal factor was weather, system failures did account for 12%
of the incomplete missions. Mission-level operational data from the system deployed in Hungary was
used to perform a limited assessment of system reliability based on data covering missions from March
1996 through April 1997.
Out of the 315 Predator missions tasked during that timeframe, weather and system cancellations kept
nearly two-thirds on the ground (60 percent). Of the remaining missions that were launched, slightly
under one half were subsequently aborted. These aborts were due to system (29 percent), weather (65
percent), and operational issues (6 percent) that included airspace conflicts, operator errors, and crew duty
limitations.
Data indicates that 38 missions (12 percent) were scrubbed due to system failures, an additional 18
system aborts (6 percent) that did not result in mission cancellation (due to launch of another aircraft or
weather hold), and other issues which kept the Predator on the ground 6 times (2 percent). Out of this