F-14A Acceleration Data Comparison

[NoGravitas]

According to The Pentagon Paradox (pg 249), written by James P. Stevenson, an F/A-18A and an F-14A had a drag race in 1980 to determine the Hornet's compliance with design requirements for acceleration (the requirement for the hornet was to accelerate from 0.8 Mach to 1.6 Mach at 35,000 feet in 110 seconds). Both aircraft were close to full fuel and carried two Sparrows, two Sidewinders, gun, and full ammunition. The results were:

 

F-14A, 35,000 feet

Mach 0.8-1.2: 56 seconds

Mach 0.8-1.6: 114 Seconds

 

When performed in DCS with calm conditions and +15°C, 29.92 InHg (ISA standard), 90% fuel and the same ordnance with the two sparrows located in the tunnel (picture attached) we get:

 

DCS F-14A, 35,000 ±200 feet

Mach 0.8-1.2: 121 seconds (+116%)

Mach 0.8-1.6: 224 Seconds (+96%)

The timer was started once the throttle levers reached maximum thrust position.
 

Here are the results of the other aircraft mentioned in that section of the book:

F/A-18A 35,000 feet

Mach 0.8-1.2: 52 seconds

Mach 0.8-1.6: 134 Seconds

DCS F/A-18C 35,000 ±250 feet

Mach 0.8-1.2: 74 seconds (+42%)

Mach 0.8-1.6: 167 Seconds (+25%)

These models are different, and the F/A-18A was still undergoing development so differences are expected.

 

F-16A 35,000 feet

Mach 0.9-1.6: 70 seconds

DCS F-16C bl.50 35,000 ±100 feet

Mach 0.9-1.6: 82 seconds (+17%)

Again, these models are different so comparison accuracy is lower.

 

The F-14A difference is significantly higher than the other modules and makes me suspicious of the A model Tomcat. It's completely possible there were more variables during the real test that were not described, but the major items like payload and fuel state were addressed. I'm sure that Heatblur has much more expansive data sets than I what I have so I guess I'm looking for reassurement that this data set is wrong, and that the DCS module is accurate to the real data set. I greatly appreciate Heatblur's development of the Tomcat and it is by far my favorite in DCS. Because of that I am trying to contribute to making it the most realistic as well.

 

Thanks,

NoGravitas

 

 

P.S.

Out of curiosity I tried the same test at 26,000 feet with and got:

DCS F-14A, 26,000 ±200 feet

Mach 0.8-1.2: 72 seconds

Mach 0.8-1.6: 132 Seconds

There is no comparison data for this altitude but there is a notable reduction in acceleration times. I've heard of a drag "bug" above 30kft but my understanding is that it would affect all modules, not just the tomcat.

 

[Skysurfer]

There is a known bug with drag/thrust in the current Tomcat versiom which got introduced in a recent update. The team is aware of it and the flight model in regards to drag, acceleration and thrust is very much WIP still. 

[NoGravitas]

Do you have any more information on that? Is it just the A model? What altitude does it diverge? Where does it lay in the list of priorities?

[Victory205]

Performance data for the A at 35K from .8 to 1.6 IMN with 4/4/0 and FAMMO at 60,000 pounds is ~180 seconds. At 25K, it takes slightly more time to accelerate to the same Mach number (which results in a higher TAS at the lower altitude), around 190-200 seconds. The data is estimated based on flight test with P414A engines.

 

Big difference in transonic acceleration if the aircraft is unloaded. The data assumes not, the anecdote from the book is undetermined. 

 

BTW, the F18 is much slower than the F14A at the top end, especially as weapons, pylons and tanks are added. Referencing your book excerpt, the Legacy Hornet with 2x2 likely can’t reach 1.6 IMN at 35K in level flight. Even then, you are talking close to a minute longer to reach it’s Mmax compared to the Tomcat reaching the same velocity, with plenty of additional speed available when the Hornet hits the wall.

 

My guess is that the numbers from the Paradox Book reflect an unloaded with a descent in the profile. Either way, it’s a pretty thin example and the numbers demonstrate that. Authors are pretty bad at getting details correct.

 

All of this is in work on the DCS F14 as well.

Edited April 5, 2021 by Victory205

[NoGravitas]

I would love to see raw data from flight test. Can you point me to where you got these numbers?

[fat creason]

There's a performance manual for the F-14A and B you can find fairly easily if you look. Aspects of the performance are being tuned so it may be better to hold off until the update is released.

[captain_dalan]

7 hours ago, fat creason said:

There's a performance manual for the F-14A and B you can find fairly easily if you look. Aspects of the performance are being tuned so it may be better to hold off until the update is released.

Will this coincide with the clouds?

[fat creason]

 

[Katj]

I know I've seen charts that pointed towards excess thrust starting to increase from Mach 1.1-ish, but in DCS it seems like Mach 1.2 is a brick wall.

I can't find said charts now, though. Does anyone have them?