Declines in Availability of Super Hornet Fighter Aircraft

Presentation by Edward G. Keating, CBO’s Deputy Director of National Security, at the 2024 Conference of the Western Economic Association International.

1. Presentation at the 2024Conference of the Western Economic Association International
Edward G. Keating
Deputy Director, National Security Division
July 1, 2024
Declines in Availability of Super Hornet
Fighter Aircraft
For more information about the conference, see https://weai.org/conferences/view/14/99th-Annual-Conference. These slidesreprise material previously published in Congressional
Budget Office, Availability and Use of the F/A-18E/F Super Hornet Fighter Aircraft(February 2023), www.cbo.gov/publication/58687and Congressional Budget Office, DECKPLATE
and AMSRR: Comparing Two Ways to Measure the Availability of F/A-18E/F Super Hornet Aircraft (July 2023), www.cbo.gov/publication/59098.

2. The F/A-18E/F Super Hornet Is the Navy’s MostAdvanced
Nonstealthy Fighter Aircraft

3. 2
Percent
0
20
40
60
80
100
1991 1996 2001 2006 2011 2016 2021
Other DoN
aircraft
F/A-18C/Ds
Super Hornets
(F/A-18E/Fs)
DoN = Department of the Navy. These data are from the Navy’s DECKPLATE data system.
CBO Reports Steep Declines in Availability Rates of F/A-18E/F
Super Hornets and Their Predecessor F/A-18C/D HornetsFrom2007 to2014
An aircraft’s availability rate
is the percentage of time it
can be flown on training or
operational missions.

4. 3
Did something befall F/A-18C/Ds and Super Hornets between 2007 and 2014?
Availability rates of other DoN aircraft also declined, but not as steeply, and the
decline started later.
Could the observed decline in availability rates be a measurement issue? In other
words, have availability standards become more stringent?
Why did Super Hornet availability fall so much comparatively early in the fleet’s life?
The Super Hornet fleet is 14 years youngerthan the F/A-18C/D fleet, on average.
The Decline in Availability of F/A-18C/Ds and Super Hornets
Raises Many Questions

5. 4
In addition to calculating availability by calendar year, we calculate availability by
age:
§An aircraft’s first month of operation is “Month 0.” The end of an aircraft’s tenth
year of operation is “Month 120.”
§Any specific calendar month corresponds to different month numbers for different
aircraft.
§We fit a cubic regression of the form
"#$%&$'%&%()=$+'×-./(ℎ+1×-./(ℎ!+2×-./(ℎ"
We Additionally Estimate Availability as a Function of Aircraft Age

6. 5
0
20
40
60
80
100
0 5 10 15 20 25
Percent
Age
F/A-18C/Ds
Super Hornets
(F/A-18E/Fs)
Availability Rates of Hornets, by Age
We Estimate That a 10-Year-Old Super Hornet Has Roughly the
Availability Rate of a 20-Year-Old F/A-18C/D

7. 6
When asked about the lower availability of Super Hornets, the Navy noted many
contributing factors, including the greater levels of galvanic corrosion arising from
the greater use of composite metals in Super Hornets.
Another potential factor contributing to the difference in availability is the
possibility that funding for maintenance was greater during the period when the
F/A-18C/Ds were in their early years than it was during the early years of Super
Hornets. Funding differences prompt a consideration of the extent to which
declining availability is a function of the vicissitudes of funding choices.
We Do Not Know Why Super Hornets Seem to Have Aged More
Adversely Than F/A-18C/Ds

8. 7
0
20
40
60
80
100
2017 2018 2019 2020 2021
Percent
AMSRR
DECKPLATE
Annual Availability Rates for the Super Hornet Fleet
AMSRR = Aviation Maintenance Supply Readiness Report; DECKPLATE =Decision Knowledge Programming for Logistics Analysis and Technical Evaluation.
Adding Complexity to Our Analysis of Availability Are the Different
Results Reported by DoN’s Different Systems
The Navy’s newer system
for tracking the availability of
aircraft, AMSRR, shows
higher and rising availability
rates for Super Hornets. The
older system, DECKPLATE,
shows lower availability
rates and no clear trend in
recent years.

9. 8
DECKPLATE records the actual number of hours in a month that a specific
aircraft was coded as being available, based on details of maintenance tasks
performed on the aircraft.
AMSRR provides a daily projection of whether an aircraft will be able to perform
missions that day. The aircraft’s availability is not reduced for overnight
maintenance if no operations at night are planned.
DECKPLATE data go back to 1990, but monthly AMSRR data on Super Hornets
start in March 2017. Thus, we lack the ability to do longer-run analyses with
AMSRR.
The DECKPLATE and AMSRR Systems Measure Availability
Differently

10. 9
0
20
40
60
80
100
2017 2018 2019 2020 2021
Percent
AMSRR
DECKPLATE
Correlations of Availability Rates With Flying Hours
AMSRR’s Availability Rates Correlate More Closely Than
DECKPLATE’s With Monthly Flying Hours for Super Hornets
The credibility of an aircraft
availability metric is
enhanced when it correlates
closelywith observed usage
of aircraft; the correlation
accords with intuition that
more-available aircraft
would fly more.

11. 10
0
20
40
60
80
100
2017 2018 2019 2020 2021
0
100
200
300
2017 2018 2019 2020 2021
Percent Hours
AMSRR
DECKPLATE
Fleetwide availability rates Annual flying hours per aircraft
A Puzzling Result in AMSRR: Super Hornet Availability Rates
Increased While Annual Flying Hours per Aircraft Decreased

12. 11
0
20
40
60
2017 2018 2019 2020 2021
Percent
Over 60 hours
30 to 60 hours
No hours
0 to 30 hours
Frequency of Various Amounts of Monthly Flying Hours per Aircraft, by Year
That Counterintuitive Finding Is Explained by a More Even Distribution
of Flying Hours Across the Super Hornet Fleetin Recent Years

13. 12
Our analysis, requested by the House Armed Services Committee, shows that
availability of Super Hornets, as measured using data from DECKPLATE, has
degraded more quickly than availability of F/A-18C/Ds.
In recent years, the Navy has increased procedures to combat corrosion as part of
depot-level maintenance of Super Hornets.
Some data indicate recent improvements in Super Hornet availability. Specifically,
the Navy’s AMSRR system seems to measure availability more usefully than
DECKPLATE,and data from AMSRR show an increase in availability of Super
Hornets since 2018.
So What Has Been Going On With Super Hornets?

14. 13