[VSKYLABS Test-Pilot Notes] issues 22nd October 2022
Remember...this is X-Plane. The aircraft is not in competition with DCS with all that related to high-tech combat avionics, radars and weapon systems. However...it shines like a star in all that is related to predicted/realistic aircraft performance, handling and non-combat aspects.
DISCLAIMER:
There is a catch here! - how could it be defined as 'realistic' if the aircraft was never developed in the real-world? how it can be compared to a parallel *real* aircraft?
The answers for this good question is as followed: a)That claim is 100% right!. and b)we did out best to deliver the most authentic jet-fighter simulation of this type, using the most advanced physics based flight simulation in our days - X-Plane 12, and with the use of extensive actual real-world experience and knowledge of how fighter aircraft are designed, built, being flown, perform, handles. This is a serious scientific based aircraft simulation of an hypothetical aircraft.
Flight Control System (FCS) Modes - General Considerations:
Advanced jet fighters usually have an adaptive/selective flight control system that can be tuned to cover multiple flying configurations or states throughout the flight envelope. For example, asymmetric payload configurations, or such that affects cg and aircraft tendency to depart under certain maneuvers or speeds.
In the VSL F-19, loading configuration is simple; two AA missile and a single AG missile...all internally-carried (no additional drag). Fuel tanks affects cg but it can me managed without a particular hassle; done automatically, and can be managed manually with the use of the tank-pressurization system that allows to over-pressure one tank over the other, and by doing this, we can balance or un-balanced the tanks, which are arranges in a 'forward' and 'aft' configuration.
*Fuel tanks management is taking part in high-altitude aircraft performance, due trim control. It will be addressed in a separate report.
The wing-shape for the F-19...slender delta wing with long chines that makes it an all-aircraft-slender delta wing planform...introduces stability issues in certain situations, mainly due to the pitch-up tendency in high AOA. Add a pitch-axis thrust vectoring capability (elevator surface acts as a thrust vectoring vane), and you are now having issues when flying fast and 'HOT' (AoA speaking).
In FCS DGFT mode, the aircraft will 'obey' your commands easily. If you are flying an intensive low-altitude, high speed/ high-g pattern (as seen in the low-altitude video down below), there is a lot of stick work. You push, you roll, you pull, fast paced and decisive control inputs. When flying fast, say above Mach 0.9, this can get you in trouble as you can over-stress the aircraft in a second. Remember, you will ask and it will give you what you've been asked for. This is a non-issue in medium speeds (the opposite happens as the slender delta wing planform gives a very docile, predictable and stable natural response to control inputs).
In FCS TACTICAL mode, the fly-by-wire and art-stability are set to a more conservative state, allowing the pilot to 'abuse' the controls at high-speeds while providing larger safety margins with various rates and G's limitations.
The F-19 80's concept presented the following pattern: To penetrate low and fast, deliver the payload, and skim out low and fast (if possible). In reality, things can get messy, and the fact that it is a low-observable aircraft (stealth), the chances of close enemy encounter during daytime may get in fact higher. The aircraft could be spotted visually, and that happens in the 'visual-range'..which is quite close. In addition, due to its limited maximum speed performance, it could be chased easily. This was also the case in the MicroProse 80's F-19 simulator... and we are trying to recreate the concept...right? 😎
So, the F-19 in our case, should be able to fly fast, low and aggressive without breaking up, and also should be capable for close-range dogfight. For the reasons mentioned above, the flight control system has two operational modes: Tactical, and Dogfight.
Food for thoughts:
The SR-71 airframe is similar in so many ways to the Testors F-19 design. In fact, putting the 3-view drawings one over the other, you'll see that the nose and chine section geometry is pretty much identical. Imagine the SR-71 intended for Mach-3 high altitude runs, but also being intended of tight maneuvers as well. In such a case, the on-board flight control system would have been built with several control modes, just like almost any multi-role fighter...
The following is quoted from the VSKYLABS F-19 Flight Manual:
FCS (Flight Control System) modes:
The VSKYLABS F-19 FCS features two control modes:
- Emergency/Dogfight.
- Norm/Tactical.
Norm/Tactical mode provides an AOA limiter with higher threshold. The effect on flight and handling is a smoother ride. Set the FCS to Norm/Tactical mode after takeoff, when cruising or flying the aircraft on a ferry mission. This mode is also the mode to set when flying at high speeds/low altitude, and when using the autopilot.
Emergency/Dogfight mode provides wider aircraft operation throughout the flight envelope. Use this mode for takeoff and landings as it provides more control throws in case of emergency. Using this mode during high AOA maneuvers such as in short-range dogfight or aerobatics will increase aircraft turn performance but might lead to faster airspeed bleed due to excessive drag.
When starting a flight (with engines running), the FCS default mode is Emergency/Dogfight.
