[Jsbsim-users] Some mental exercises for the JSBSim community

[Bill G. <bi...@ho...>]

Greeting all,

 

It’s been pretty quiet here for a while. Thought I’d throw out some JSBSim projects for you all to think about. They are just some metal exercises. I’m sure they can all be done, and I’m not suggesting that you do them… unless you have nothing else to do  ☺   These are projects that I’ve thought about over the years, some of which I’ve actually worked on a bit.

 

 

Air Traffic Controller

Background and problem statement: I was actually posed with this problem. A French company won a contract to build an Air Traffic Control (ATC) simulator, for an airport near Charles De Guallle airport. It had to simulator 200+ different types of aircraft, from brake release on the runway to departing the pattern for their destination, following ATC directions. It also had to handle incoming traffic, say from 50 miles out to landing. The aircraft varied from light aircraft, small twins, and large passenger aircraft. There would be a varying number of aircraft in the air at any one time.

 

My partial solution: I wrote up a nice proposal for them, describing how to solve the problem with the least painful method. I didn’t win the work, and they probably used my solution to help them along. With Datcom, the aircraft models would be simulated fairly accurately, to allow JSBSim to fly them. I was going to generate JSBSim models in Datcom for a few of the aircraft, and let them flesh in the rest of the aircraft using their people, as time allowed. I was going to write a generic autopilot, which was the key to the successful completion of the project. I was going to attempt to parameterize all of the autopilot constants, so that little to no tuning was required for each aircraft. I don’t know how they solved the problem, but they might have gone with some dead-reckoning solution. It wouldn’t look as realistic as actually flying the aircraft.

 

 

Magic Carpet

Problem Statement: The Navy has a program called “Magic Carpet”, for the F/A-18 (and eventually other aircraft) which will auto-land an aircraft on a carrier deck. Keep in mind that the carrier deck is not parallel to the carrier’s centerline. Initially, consider the carrier just steaming straight ahead with no cross-winds or sea states. The aircraft approaches from a ways off, maybe at a heading different than the carrier’s. It has to enter the pattern at a set altitude, decide when to turn in for the base leg and for final. A particular glide slope must be maintained. Don’t forget to put the hook down, and when those wheels hit, you go to full throttle. (In training in a T-45, if you land just ONCE and don’t go to full throttle, you wash out.)

 

Mark it harder:  (a LOT harder)

1.     Make the sea state something more serious, like a sea state 3, where the aircraft carrier is pitching and rolling in the waves. When the carrier pitches down, the ‘meatball’ is going to move, and your aircraft might actually be BELOW the level of the deck, right before touchdown (and hopefully not impact). Ideally, you would want to land when the carrier has reached a peak or trough in that pitch cycle, because the vertical velocity of the deck would be near zero. If not, you have to account for the deck vertical velocity. If it’s coming up, and you are coming down. That could result in a VERY hard landing.

2.     Add in a cross wind.

3.     Do it all with a failed engine.

 

 

Call For Fire/ Close Air Support

Problem statement: Ground troops call in for air support, and provide what is call the “9 line” of information, about where the target is, local conditions, where the bad guys are, where the good guys are, what munitions they would like gift-wrapped and delivered, etc. There will be a CAS (Close Air Support) aircraft nearby that will come in strafe or drop ordinances (or flyers, if you wish). So, program an aircraft to loiter nearby, and when it receives the call, the CAS aircraft sets up an approach, figures out when to drop the weapon for it to reach the target, then the CAS goes back on station. When the weapon is dropped, an instance of JSBSim flies the weapon to the target. 

 

Background: I was posed this problem by a company doing a Call For Fire simulator. The Aero engineer that provided the simulation for them was pretty clueless (I worked for him years ago. Dilbert’s Pointed Haired Boss was modeled after him). The aircraft would come in sometimes pointed at the sky. If the ground troops weren’t ready, the aircraft would just hang motionless in the air. I put a proposal together for them, but couldn’t get my foot in the door.

 

My partial solution: Datcom can help with the aerodynamics of a ‘dumb’ bomb. To figure out where to drop the weapon, I figure you could run an instance of JSBSim at a very low rate, like 1 hz, just to figure the impact point. Calculate the horizontal distance from impact point to the target. As you approach the target, the distance from the impact point to the target will decrease until it either reaches zero (the target), or decides that it is as close as it can get (the distance to the target starts to increase). Weapon is dropped, and flown by JSBSim, maybe at a higher rate than 1 hz, until impact. Scoring happens.

 

Make it harder: 

1.     Add guns to the CAS aircraft. Fly the bullets to the target. (maybe not every bullet, but a subset, and probably the first and last)

2.     The target is situated such that a particular approach is required, such as being in a canyon.

3.     Multiple (2, 4, or more) aircraft flight is providing air cover. Fly the aircraft in formation from outside the gaming area in one of several standard flight formations, starting in formation and remaining in formation until they reach station. Once there, they break and circle, so that there is always someone that is closest to the target. The closest CAS attacks when the 9-line information is received, while the other aircraft remains on station, ready for a subsequent attack.

4.     Fly the multiple aircraft on station in formation, and attack with two aircraft at a time.

5.     Make the aircraft in the flight dissimilar (mix of F-16, A-10, F/A-18, F-35, etc.)

6.     Add winds on the ground, maybe some turbulence.

7.     Add ‘smart’ weapons, such as a JDAM, which can steer itself towards the target. Of course, you have to direct the weapon towards the target. The release point decision might change, to ‘Yes, it can probably get there’, to ‘Much higher probability of hitting the target’, in case you don’t or can’t overfly the target. Release of a JDAM-type weapon might be from a high altitude to protect the mother ship. 

 

 

Top Gun

Background and problem statement: In a recent article in Aviation Week, they talked about having unmanned ‘companion’ wingmen (controlled either remotely or autonomously) fly with manned aircraft into battle. Sounds interesting, so make up some scenarios of your own:

1.     Fly out to the gaming area in formation, reposition into an attack formation when the enemy aircraft are within range, maintain formation during the ‘fur fight’. This means that the lead aircraft would have to be programmed to perform various combat maneuvers based on where the enemy is, and the unmanned aircraft would hang in there. You also have to program the enemy aircraft, hopefully with different decisions so that both sides aren’t flying the identically same maneuver.

2.     Let the flight consist of only unmanned aircraft, and program to attack the enemy, either solo or in pairs, firing guns or missiles as required.

3.     Go “head-to-head” with your friends and their aircraft. You’ll need to use FlightGear for an out-the-window visual, and maybe they have something else for a God’s Eye view of the gaming area. Compete for HUGE prizes…. Okay, bragging rights only.

 

 

So, think you are going to get any sleep tonight?

 

Enjoy yourselves, and be safe out there,

 

Bill