When I was six years old, my mother worked in an Adult Education Centre – her job was to train and teach adults, usually women who had been living as house wives for most of their lives, how to re-integrate into the workforce. The Adult Education Centre was a stone’s throw from my elementary school at the time, so my sister and I would walk over there and spend the afternoon with my mom after school most days. Sure, getting to spend the afternoon with my mom and sister was always great… but the real reason I went there was my love affair with the single taciturn and sensible IBM PC XT with a monochrome monitor that sat on a table along the wall: It had a game that let me fly a plane.
In this article I explore the different qualities the word “simulation” has, and argue for a more experiential approach to flight. A note to readers: I’d love to hear about your experience with all kinds of flight simulators, because I have intentionally pared it down to just a few here.
Flight Simulation in its Infancy: MSFS 1.0
Microsoft Flight Simulator 1.0 was, to my best knowledge, my first computer gaming experience. One of the teachers – when he wasn’t busy – would sit down with us, and patiently point out the controls: left hand on F2 for power, and right hand on the numeric keypad for direction. My sister would hold down F2, and I’d feebly try to point the “plane” down the runway.
I write “plane” pejoratively. The problem with MSFS 1.0 was that the experience of flight was an afterthought – the aircraft never appears on-screen, the field and runway are low-res projections, engine sound is limited to a variable buzz from the PC speaker, and the instruments are the only real indication that something important is happening.
Inevitably, we would careen down the runway and the plane would edge upwards for a second, stall, and land back on the tarmac. Twenty frustrated minutes later, my sister and I would give up and wander over to the Xerox machine and make copies of our hands.
From a gamer’s perspective, I am being unfair: MSFS1.0 was one of the earliest flight sims, and SubLogic’s programming efforts were leaps and bounds ahead of their competitors. But, I think, when you see past the crude graphics and choppy frame rate, you see less a “game” than a spreadsheet.
So the question is: what is being simulated? Should a flight simulator try to simulate the experience of flight, or simulate the mathematics of instrumentation?
Ask anyone that’s flown in the front seats of a smaller aircraft like a Cessna 172 or Piper Cherokee: the aircraft is very responsive. A feather touch on the control column pitches down the nose a few degrees, and the tail snaps upright in a single motion… your gut climbs up into your throat, and your head swims for a brief second. The sound of the little engine thrums in the cabin, and penetrates past the David Clark headset that is vacuum-sealed around your ears. As a passenger, I can stare at the instruments and appreciate that there are a dozen things happening simultaneously, but I really don’t know (or care) what they mean. I’m focused on the feeling of flight itself.
A Step Closer: Aces of the Pacific
Fast forward about seven years. Sitting in my uncle and aunt’s office, with a much heftier and sexier machine: an AST Advantage! 386 with a 256-color VGA card. They owned Aces of the Pacific and a CH Products Flightstick Pro. Afternoons were spent gunning down Japanese Zero’s from the cabin of my P-38 Lightning.
The flight model in Aces of the Pacific is pretty responsive. As you’ll see in the video, climbing off of the runway is effortless… the engines rev up to max within a couple seconds, getting up to takeoff speed within five seconds, and once in the air the aircraft snaps left and right as if it were a dragonfly. A real P-38 flies nothing like this. But, I spent months dogfighting and bombing, running missions for both sides of the second World War just to scrape up another hour of time in the cockpit. It was fun.
But when you strip away the art, there wasn’t very much difference between Aces of the Pacific and Wing Commander II. The “simulation” of flight in these flight combat games was so heavily tuned for combat that any semblance of simulation was tossed out the window. Training my 37mm cannon on a Japanese Zero at 8,000 feet wasn’t much different than training up my Broadsword’s Mass Drivers on a Kilrathi Dralthi at Nav 1. Something was lost in the experience of flight in Aces of the Pacific, and it wasn’t until 1995 that Looking Glass Technologies finally got it right. And, to my knowledge, no flight simulator has gotten the experience of flight right since.
What it Really Feels like to Fly: Flight Unlimited
Sitting in my uncle and aunt’s office in 1995, this time with an even beefier Gateway 2000 Pentium 90 that my uncle called “The Ol’ Stove” because the processor alone could heat up a room. But that kind of horsepower was necessary, because Flight Unlimited demanded some pretty serious computing resources.
I sit down in the Pitts Special S2-B and harness up. The view out the front is limited by a handful of gauges, and the wing that tapers across the nose of my little aerobatics plane. Revving up the single engine is a pleasure in itself – it was obviously recorded from a real Pitts Special, and the engine noise changes in pitch and loudness according to its RPMs. The plane lurches forward on the runway, and as I get up to stall speed I notice it start to shimmy back and forth slightly … the wheels are grabbing at the tarmac at different rates, just as I’ve felt in a Cessna 172 as we lift off. A few feet above the runway I experience the “ground effect” – the Pitts floats as if on a cushion due to the increased lift caused by the air pressure being so high close to the tarmac. When I hit climb speed, I pull back hard on the control stick, and the Pitts climbs up into the atmosphere with a metallic groan.
I climb up to 5000 feet for a little fun: the in-game flight instructor is teaching me down to do a “spin” – a forced stall that causes a plane to pitch downward into a corkscrew path. I point the nose up at the sun, cut the engines and hit the left rudder. What happens? My Pitts Special turns to the left and begins to dive, corkscrewing around the left wing. My speed is increasing, and begins to redline the airspeed indictor. I’m “overspeeding” the airframe, and the wind rushing past the wings gives off an eery metallic whine. I don’t want to crash, so I follow the virtual flight instructor’s advice: cut the throttle, apply full rudder in the opposite direction of the spin (in my case, right rudder), and gradually pull back to zero-out my angle of attack. Unbelievably, I recover from the spin, and resume level flight like a pro. And damn, that was fun!
A few minutes later, I do the same spin maneuver and intentionally overspeed the aircraft, and as I careen towards the terrain below, I snap back on the control stick and watch as the forces applied to the fuselage and wings snap the little plane apart. They smash into the ground in a pile of parts that the FAA/NTSB crash investigations teams would have a hard time deciphering. My flight instructor wryly adds a note to the logbook: “Solo flight. Wrecked the plane. We’ll fly in your plane from now on.”
A Pitts Special exploding in the air as the airframe collapses under extreme G-forces
The whole experience, from takeoff to aerobatic techniques to engine noise (or in the case of the engineless sailplane – the whoosh of air around the cabin), is responsive and enveloping. Anyone who has flown in a small aircraft can attest to how different Flight Unlimited is, say, compared to Microsoft Flight Simulator X.
Computational Fluid Dynamics for Dummies
Flight Unlimited was, and is, the first and only flight simulation game to use a completely different flight physics model. An interview with Seamus Blackley (published in CGW Issue #133, August 1995 - I honestly suggest reading the entire article, it is excellent) – the programmer and designer behind the game – reveals the unique values and skills that went into developing an accurate simulation of flight:
When Blackley set out to design this flight simulation, he wanted the armchair pilot to get that “yummy, visceral, fluid feeling that you get when flying a real airplane.” To do that, Blackley and the Flight Unlimited team had to dive head-first into the Navier-Stokes equations, which, according to Blackley, are “horrible, complicated partial differential equations” that model the way a fluid behaves when it moves around a solid object.
Instead of relying upon a Newtonian system of drag coefficients and vector geometry – where an object remains in motion until it meets an equal and opposite force, or a brute-force approach that models flight on huge tables of data generated in wind turbine lab experiments - Flight Unlimited was built on a physics model derived from Computational Fluid Dynamics.
Blackley, a pilot himself and an ex-graduate student in particle physics at the time, turned to computational fluid dynamics because they could model the feeling of flight moreso than the mathematics of movement. And with computers featuring built-in floating-point processors (like the Pentium) and tons of calculation cycles available, it became possible to use CFDs for the first time in a computer game.
So how does Flight Unlimited actually work? First off, the complex sets of Navier-Stokes partial differential equations would allow the game to simulate the effects of air pressure on a fixed wing: when the air pressure above the wing is less than the air pressure below the wing, the air (a fluid) makes the wing buoyant and pushes the airplane up into the air.
That process is complicated enough, but add to it the infinitely complex changes in air pressure over the entire plane:
… the propeller creates turbulence and a torque imbalance; the air eddies and curls as it comes off the back of the wing; the air “sticks” to the surface of the airplane, causing drag; and bumps in the plane’s shape, such as the pilot’s canopy, cause turbulence in the moving air. All of this adds up to one hell of a mathematical nightmare, but all of those little blips in turbulence and pressure are calculated by the Navier-Stokes equations…
…the program must compute the air pressures over the entire surface of the airplane, and convert those pressures into a series of force distributions, which are then used to calculate where and how the plane is moving.
In short, the plane flies through the air because Blackley has simulated an atmosphere in the world that applies air pressure changes to the entire aircraft, and the “control surfaces” of the plane – the rudder, the ailerons, the elevator – all create turbulence and disturbances in the atmosphere that pitch, roll, and lift the plane. A plane feels like a plane because it displaces, and is displaced by, air. As Blackley puts it, “You get everything for free once you get the air’s fluid dynamics right.”
Final Words for Developers
Make no mistake – I’m not arguing for pin-point accurate physics simulation as the key for more immersive and more enjoyable flight simulators (or any other kind of game). In fact, I’ve argued before that we probably should rely a lot less upon “realism” as a central value in most games. The point is that games like Flight Unlimited manage to deliver an enjoyable and visceral flight experience because the developers make the experience, and not the mathematics the core value of the simulator. Developers need to learn to leave the mathematical aspects of games “under the hood” and make them completely subsidiary to the player’s experience. After all, the only thing we have as players is our experience of the game.