GAO claims that the F-18E accelerates from 0.8M to 1.2M:
52.8s at 5,000 ft
50.3s at 20,000 ft
64.85s at 35,000 ft
Are the numbers true? Spoiler alert, with a very high probability - no.
At the acceleration time of the F-18C:
21.0s at 5,000 ft
34.6s at 20,000 ft
55.80s at 35,000 ft
as well as differences in thrust-to-weight:
10.49% at 5,000 ft
6.42% at 20,000 ft
3.02% at 35,000 ft
there is simply no place for such a difference in acceleration time (especially at 5,000 ft). And the acceleration curve of the F-18E looks like some kind of nonsense.
I have found absolutely no documentary evidence for the acceleration time data provided by the GAO. Moreover, the GAO does not name the exact source from where this data is taken.
Also, GAO does not refer to this data in the DOD responses, although such a gap in acceleration speed is definitely not in favor of the F-18E.
The F-18E has 25% greater wing area, is 3 tons heavier empty, and has considerably worse aerodynamics in favor of radar reducing features and materials.
The F-18E data is navy calculated data, the F-18C data is from NAVAIR testing conducted in 1993. The F-18E and F-18C are similarly loaded with 60% fuel, 2x AIM-9, and 2x AIM-120 for the acceleration and turn rate tests.
Weight with 2x AIM-9, 2x AIM-120, and 60% fuel // Thrust & thrust to weight at 0.8 mach
F-18C, ~30,576* pounds // 19,342 lb-f per, 1.26:1
F-18E, ~41,961* pounds // 22,299 lb-f per, 1.06:1
*(assuming each AMRAAM to be 345 pounds and each AIM-9 to be 185 pounds)
37% heavier, larger, draggier, and with 19% less thrust to weight. Considerably less optimized for wave drag - instead focusing on shapes more optimal for reduced radar cross section and spacing for ordnance. Featuring more prominent high-alpha devices that produce much more induced drag.
It is no wonder the F-18E accelerates considerably worse than the F-18C, especially with the enhanced performance engines.
It is my belief that the data may have been stretched to imply the F-18E is worse than it really is, but what I see does not seem to contradict itself. Without a CFD of the F-18E as compared to the F-18C we cannot definitively say that the trend of worse acceleration is an outlier in this particular document.
The fact that the F-18E accelerates worse is obvious. No one argues with this. But the fact that it accelerates almost THREE TIMES worse at 5.000ft looks like outright drivel.
I’m guessing there might be a typo. In fact, there are possible values:
I quoted the weight for 60% fuel and 4 missiles - the differential between the two is 37% as I stated.
41,961 is 137.235086% of 30,576.
That is 37.24% weight increase.
I quoted the difference for 0.8 mach at sea level, standard day temperatures. That is not shown on page 82. It only shows static speeds for sea level. Additionally, the weight appears not to match other known data, so I stated the weights I used for measuring.
If you consider the weights they provided;
F-18C: T/W of 1.161
F-18E: T/W of 1.061
Difference; 9.4%
The requirement for the F-18C’s specific excess power was at least 700 ft/s at 0.9 mach or something like that if I recall correctly. The F-18E’s drops to approximately 663 ft/s or so. You can see this on the following pages;
The problem is more so drag than anything else as I stated before. The F-18E is far draggier than the F-18C and it has worse thrust to weight. The design is made worse for transonic flight region (specifically where these acceleration comparisons are being made, intentionally and with the goal of smothering the F-18E on paper).
The Chief Test Pilot of the F/A-18E/F said “Lot XIX C/D will nose out a clean E/F in a drag race from 0.85 to 1.2 at 35,000 ft”, as like mentioned in NSIAD 96-98.
He did said “F/A-18E/F subsonic performance in both MIL and MAX power is significantly superior to that of a C/D”, but this is different story.
You dropped the F-18C and F-18E weight table by yourself.
F-18C - 33.325 lbs
F-18E - 42.023 lbs
(42.023-33.325)/33.325*100% = 26%
The T/W difference is not a static concept. It varies depending on the height and other parameters.
IMHO, the pilot’s words are absolutely no proof of anything. They cannot be used as an argument for technical specifications. The pilot is just a talking head.
However, even with this in mind, there are no proofs for an almost threefold difference in acceleration speed.
@MiG_23M According to the material that you threw at me, it takes ~ 45-48 seconds from 0.8M to 1.1M at 10,000 ft. (it takes too long to get to 1.125M).
Right, the time to accelerate becomes increasingly slower as it approaches the maximum speed at that altitude. This is a function of excess power - the F-18E has less than the F-18C.
In order to meet the IOC, testing will be limited to the F/A-18 E/F midboard stations. Following midboard station testing, the program will test SDB II and BRU-55 on inboard stations and the SDB II and BRU-61 four-place launcher on midboard and inboard stations.
The GBU-53 seeker is multimode (SALH, MMW & IIR ) and additionally has GPS / INS (LOAL) point & area targeting w/ Post release (and 3rd party) guidance update capabilities.
And as such having 8~28 of them at a time seems a little much especially considering they can be backported to all existing airframes that currently have access to the SDB-I (e.g. A-10C, F-16C, F-15E)
