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modes analysis for each UA model.
TABLE H-2: SUMMARY OF UA FAILURE MODE FINDINGS
Power/
Propulsion
Flight
Control Comm Human/
Ground Misc
RQ-1A/ Predator 23% 39% 11% 16% 11%
MQ-1B/ Predator 53% 23% 10% 2% 12%
RQ-2A/ Pioneer 29% 29% 19% 18% 5%
RQ-2B/ Pioneer 51% 15% 13% 19% 2%
RQ-5A/ Hunter* 38% 5% 31% 7% 19%
Aircraft
RQ-7/ Shadow 38% 0% 0% 38% 24%
* The vast majority of all Hunter aborts (58 percent) were due to weather.
There are several noteworthy trends from the summary data in Table H-2.
The failure due to Human/Ground related issues is significantly lower for the MQ-1B Predator. This
may be largely due to the increased use of simulators for Predator training, as well as enhancements
made in situational awareness.
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.
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, Amodel
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.
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.
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.
UAS ROADMAP 2005
APPENDIX H – RELIABILITY
Page H-5
38%
19%
14%
17%
12%
Power/Prop
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).
32%
28%
11%
22%
7%
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
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