Thank you everyone for your answers, they are really helpful. You guys are correct that Mach number is generally more important for top speed and that a few knots difference at sea level realistically wouldn't be that big of a deal.
Mostly I was just curious of the Thunderstreak's top speed at sea level since I've seen quite a few different numbers from 595kt from the SACs up to 601kt from a few books (that's why I thought that the performance tests for the SACs could have been with Pylons attached).
P
PStickney
The info you provided is really interesting to me, what book do you have that gives the top speed with Pylons off as 600kt for the W-7 engine? Most of the sources I've seen have said that despite the more powerful engine, the W-7 Thunderstreak wasn't any faster than the W-3 engine variant.
The numbers come from the Dash-1 for the F-84F, specifically
T.O. 1F84(25)F-1, Flight Manual for USAF Series F-84F-25 and Later Aircraft,
Issued 15 February 1963, and updated on 23 September 1963.
The specific data I posted is from the Range Cruise Chart curves for the airplane in that specific configuration at 100% power.
I'm assuming that you're referencing the SAC Charts posted by Ryan Crierie at alternatewars
(A great resource, he's done a lot of hard work to collect that up)
Those charts were released in Sept, 1958 in the case of the -7 SAC, and March, 1957 for the -3 SAC. SAC Chart Data and Flight Handbook Data come from Flight Test Data (if available), and the provenance is noted in the charts.
Note that Flight Test Data is always corrected to Standard Conditions. so that comparisons are valid.
In the case of the J65-W-3 powered '84s, the data source for the SAC Chart are the Contractor's Flight Tests, and the USAF Phase IV Flight Tests,
In the case of the J85-W-7 Chart, the basis is the same Flight Tests as the -3 to determine the aircraft's drag data, and estimated engine performance.
Performance Basis for the Manuals are (except in the case of a Preliminary Manual, issued during Initial Flight Test) the reduced results of the flight tests themselves. (Albeit that fuel consumption numbers are "pessimized", increased beyond the test figures) These numbers are checked periodically by follow-on flight tests, and the manuals updated accordingly.
Note that for Transonic aircraft, like the Super Hog/Thud's Mother/Thunderstreak the top speed is far enough into the drag rise region that increases in powe can produce little, if any, change in Vmax. (Climb performance, which peaks at lower speeds, will benefit proportionally more.)
So - it looks like what we have here is a case of the SAC Charts using the 1954-55 Test Data, and, in the case of the -7 engine, estimated thrust data.
The 1963 manual is using measured test data.
There's a danger in cutting things too fine - the differences in individual aircraft of the same version will vary by more than the differences we're seeing here.
In Aviation, valid answers will always start with "That Depends..." - context is everything, and conditions, both environmental and mechanical count for a lot.
When evaluating information, it's important to know the Who, What, When, Where, Why/How of the sources of the data being used to derive that information.
Then, if you're of an Engineering Bent (Like Me) you take the data back to first principals, use it to derive the basic characteristics, then see if things like Drag Coefficients or Powerplant Performance are plausible.