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Global Hawk, Predator, Hunter, and Pioneer fleet for the period 1986 through 2003. Class A mishaps are
those aircraft accidents resulting in loss of the aircraft (in Naval parlance, “strike”), human life, or causing
over $1,000,000 in damage2. These data show a mishap rate (i.e., Class A accidents per 100,000 hours of
flight) of 20 for Predator, 47 for Hunter (24 since the major reliability improvements in 1996), 88 for
Global Hawk, 281 for Pioneer, and 191 for Shadow. For comparison to two manned military aviation
mishap rates, the U-2 and F-16 have cumulative Class A mishap rates of 6.8 and 4.1 per 100,000 hours,
respectively. Comparing to non-military aircraft, general aviation suffers about 1 Class A mishap per
100,000 hours, regional/commuter airliners about a tenth of that rate, and larger airliners about a
hundredth of that rate.
With the exception of Pioneer and to a lesser extent Shadow, these statistics make it apparent that the
reliability of UA is tracking that of early manned military aircraft, and maturing to approach an equivalent
level of reliability to their manned military counterparts. Specifically, the early Pioneers (as discussed
later in this appendix) had an analog air data system, problems with ship-board EMI, and generally
suffered from poor design practices. (A planned conversion to a more reliable engine for the Pioneer
never took place.) Compared to this low benchmark, the Hunter program has seen continuous reliability
enhancements from efforts initiated in the mid-1990’s to improve hardware and maintenance. Not
surprisingly for the higher-end systems, the Predator has enjoyed relatively high and stable reliability
2 Per OPNAV Instruction 3750.6R, “Loss of a UAV is not a Class A unless the cost is $1,000,000 or greater.” All
Pioneer mishaps discussed are therefore Class B Mishaps.
UAS ROADMAP 2005
APPENDIX H – RELIABILITY
Page H-3
throughout its ACTD to operational phases, and the Global Hawk appears to be tracking the reliability of
its manned counterpart, the U-2.
The reliability trends calculated during these flight hours are detailed in Tables H-1 and H-2. Following
these data is a discussion about the individual UA systems and how their fielding and operation contribute
to the reliability data.
0
100
200
300
400
500
600
700
800
900
100 1,000 10,000 100,000
Cumulative Flight Hours
Class A or B Mishaps per 100,000 Hours
Pioneer
U-2
Global Hawk
Hunter
Predator
F-16
Shadow
FIGURE H-1. U.S. MILITARY AIRCRAFT AND UA CLASS A MISHAP RATES (LIFETIME), 1986 – 2004.
TABLE H-1. SUMMARY OF UA RELIABILITY FINDINGS.
MTBF (hrs) Availability Reliability
Mishap Rate
per 100,000 hrs
(Series)
Mishap Rate
per 100,000 hrs
(Model)
RQ-1A/ Requirement n/a n/a n/a n/a
Predator Actual 32.0 40% 74% 43
MQ-1B/ Requirement 40 80% 70% n/a
Predator Actual 55.1 93% 89% 17
20
RQ-2A/ Requirement 25 93% 84% n/a
Pioneer Actual 9.1 74% 80% 363
RQ-2B/ Requirement 25 93% 84% n/a
Pioneer Actual 28.6 78% 95% 179
281
RQ-5/ Hunter Requirement 10 85% 74% n/a
(pre-1996) Actual n/a n/a n/a 255
RQ-5/ Hunter Requirement 10 85% 74% n/a
(post-1996) Actual 21.2 99% 97% 24
47
RQ-7/
Shadow Actual n/a 85% 98.8% 191 191
UAS ROADMAP 2005
APPENDIX H – RELIABILITY
Page H-4
Table H-1 summarizes the reliability metrics for all military UA examined in this study. With respect to
the required values as outlined in the operational requirements and specifications, green and red signify
instances in which the actual values meet or fall short of the requirements, respectively. In the case of the
mishap rate per 100,000 hours, no requirements were identified. In addition, requirements are not
available for the RQ-1A/Predator due to their development after concluding its ACTD (discussed later in
this appendix), nor are they available for the Global Hawk due to relatively low flight hours.
The mishap rate per 100,000 hours is presented in two ways. The model/series mishap rate illustrates
“before and after” gains made in reliability and operations between subsequent versions of the same UA
model. The model mishap rate is a snapshot of the combined performance of all versions of each UA
model. It incorporates all mishaps over that fleet’s cumulative flight hours.
In all cases except for the RQ-2/Pioneer, the UA systems examined in this study exceed operational
requirements. The shortfalls in the RQ-2A reliability performance (shown in red) were amended with the
next generation RQ-2B with the exception of the availability metric. Table H-2 presents the failure
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