F14 Aero notes: (rjh@zaretto.com); aero V1.2; updated 2021-01
-------------------------------------------------------------

The original aerodynamic model that I created in 2014 was primarily
using windtunnel data from AFWAL-TR-80-3141 parts I and III – however
back in 2018 I found some new data in documents TM-X-62244
(longitudinal) https://github.com/Zaretto/fg-aircraft/issues/59 and
TM-X-62306 (lateral)

Adjusted engine power tables based on the NASA-TM-104326 but adjusted
to match known performance points. Still needs more work

Correct simulation of analogue and digital flight controls (and SAS)
based on based on the schematic data in NASA-TM-81833

Added DLC simulation based on the data in NASA-TM-81833 but also with
both the original DLC which uses all spoilers between -4 and 17
degrees for both roll control and DLC and the mod AFC 735 which uses
the inner spoilers for DLC using the full deflection (-4 +50) and the
outer spoilers for roll control.

New APC with accurately simulated APC based on "NASA TM-X-81833. see
https://i.imgur.com/gAbAGeE.png

When the damage is turned on the flaps and slats will both receive
damage as a result of overspeed conditions. This will have the same
aerodynamic effect as flap retraction - however also the flaps and
slats will get jammed if overspeed continues for an extended period.

Estimated / non wind tunnel or flight test data
-----------------------------------------------
* All negative alpha values have been estimated based on experience
  and using NASA CR-1756 747-100 (Boeing D6039643 VolII) to validate
  the basic concepts.
* Stores coefficients
* Wing Sweep and mache effects are based on values from VSPAERO

General features
----------------
    * Complete simulation of the airframe and the various 
      features.
    * Engine simulation is really only accurate for thrust; 
      this is a limitation of JSBSim
    * Flaps and slats can be damaged by overspeed
    * Excessive G will tear a wing off
    * Digital and analog simulation of Flight Control system
    * APC
    * DLC
    * Arrestor wire simulation based on aircraft mass and speed
      - overspeed landing will result in less efficient or non 
        effective arresting wires 

Missing features
----------------
    * No ACLS
    * No RATS for GE engines

Validation of aero V1.2
-----------------------

Mostly the validation has been by flight testing; but also the
coefficients have been compared against the original data sources to
ensure that the values are consistent with the originating data.

Overall error is within 2% of published; Figure 11-8. Landing Approach
Airspeed (15 Units AOA) in NAVAIR 01-F14AAP-1, also in NAVAIR
01-F14AAP-1.1 Figure 7-1 Approach Speed DLC netural- Flaps down (15
units AOA) two engine gives us 136 kts IAS; which when allowing 8knots
for DLC gives us also 124 kts IAS.

Also I’ve used photographic references to cross check; photo(2) below
is useful because I can see that it is onspeed from the lights on the
nose gear; with some matching of my model against the photo it appears
that the pitch angle is around 6 to 7 degrees.

1. https://www.airhistory.net/photo/173772/163414
2. https://www.airhistory.net/photo/134161/163897
3. https://i.imgur.com/aXvizJU.png 

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F-14A (TF-30) October, 2015

The new F-14A JSBSim has the TF-30 engines fitted. As part of this change a basic compressor stall model was added (as these engines are famous for this). The model attempts to follow the documentation in the released MIR (Lt. Hultgreen, F-14A) and information in NATOPS.

A compressor stall or surge is basically a difference in pressures between the LPC and HPC usually caused or related to disruptions in the axial flow. To model this I've added P0(alpha,beta) (we already had PB (which is more like P8 or P12)) and DP3(N1) (based on the UH-1 Blackwhawk gas generator model). These are then used together with some constants to come up with a model that will likely induce a compressor stall below 80% N1 (as per NATOPS) at alpha starting >5 degrees, beta > 0 degrees, with a lag filter to fudge the lack of different HPC/LPC speeds (the JSBSim turbine model does not use gasgen so as such the HPC/LPC will always follow each other which requires a this fudge). 
