From Software to Supersonic: Explore the World of Flight Simulation

Boom engineers answer questions about flight simulators

Most pilots don’t practice engine failures in a real airplane — and for good reason.

But thanks to flight simulation software, they can experience many types of risky scenarios and learn how to manage them safely on the ground, and even from the comfort of home.

The Boom team explored all things flight simulation during its monthly Ask An Engineer Twitter chat. Boom has many in-house authorities on flight simulation, including Jeff Bozarth (Lead Avionics Engineer), Ed Hopkins (Avionics Engineer) and Phil Coyle (Aerospace Engineer), and enthusiasm for simulators runs deep throughout the organization.

Bozarth, who began his career as a flight simulator engineer with Delta Air Lines, is responsible for the avionics system for XB-1, Boom’s supersonic demonstrator. Hopkins is a member of the team that built Boom’s XB-1 simulator and recently earned his private pilot’s license. Coyle, who is on the Overture aerodynamics team, runs the Flight Simulation Association in his spare time and is also a pilot. All three are avid “simmers” — aka flight simulator enthusiasts.

Here’s a snapshot of the chat.

What’s the difference between a physical simulator and a software program?

Ed Hopkins: Both are based on a physical model. The same type of software that powers physical simulators also powers desktop simulators. However, physical simulators also endeavor to be an accurate representation of an aircraft cockpit, including everything from the pilot’s seat to the controls.

Boom’s XB-1 simulator has a cockpit that’s very similar to the physical aircraft. The team used it to test avionics and controls such as the stick, rudder and throttle, and to train Boom test pilots.
How much control can a pilot have in a simulator? Do systems override your actions?

Phil Coyle: Most modern Part 25 certified aircraft (larger transport aircraft weighing more than 12,500 pounds) use a variety of control systems to augment the pilot’s input and ensure the aircraft doesn’t operate outside of a predefined flight envelope — beyond the operational limits of the aircraft.

This concept is generally referred to as “fly by wire.” These carefully architected systems, designed in consultation with pilots, ensure a healthy balance between pilot input and computer augmentation. Most flight simulators mirror these control systems.

On an airliner, these systems would make maneuvers like a stall extremely difficult for the pilot to do inadvertently. The systems provide several forms of awareness that the aircraft is getting near an unsafe condition, and work to limit the aircraft’s attitude to prevent an actual stall from occurring. When you’re flying a simulator, the same systems will prevent you from making these maneuvers.

The Boom team simulates aircraft behavior using a variety of computer scripts that run automatically in the XB-1 simulator.
How long is an average simulation test for supersonic flight at Boom?

Phil Coyle and Jeff Bozarth: The length of each simulation depends on what we’re testing. Sometimes, we need pilot feedback on a particular aspect of the aircraft’s flying qualities, which requires more time. In those scenarios, we’ll use the piloted XB-1 simulator to run through the aspect we’re interested in. We don’t necessarily simulate a full flight from takeoff to landing. We typically repeat the scenario multiple times with different pilots to get different points of feedback.

We also simulate aircraft behavior using computer scripts that run automatically. For example, we can simulate thousands of landings to explore an aircraft’s sensitivity to different wind scenarios. Such a test could take weeks with a pilot in the simulator, but a computer can run those simulations faster than real-time. We get results in a matter of hours.

Does desktop flight simulation replicate real-world flight?

Phil Coyle: Home flight simulators aren’t meant to fully replicate the “stick and rudder feel” of the aircraft. When it comes to real-world training, don’t expect to use them for tasks like learning how to land in a crosswind. I commonly hear from airline pilots that even the multi-million dollar Level-D simulators they train on don’t fully recreate the feeling of flying the aircraft.

Instead, the value of desktop flight simulation is as a procedural trainer. It’s ideal for tasks like practicing checklist discipline, learning how to program a GPS or complicated “glass cockpit” avionics, and becoming more proficient with air traffic control communications.

Can desktop flight simulators help you prepare for flight lessons?

Phil Coyle: Imagine you’re going on a flight training lesson this weekend and your instructor has told you the airports you’ll visit and the approaches you’ll fly. A home simulator is the perfect venue to pre-fly that lesson plan: actually go through the flight on your simulator. When you’re doing it in real-life, you’ll already be familiar with the flight and get things right on the first try.

Bear in mind that flight lessons are pricey. I routinely speak with flight instructors who are amazed at how much money students save when they properly use a home simulator to augment flight training.

Does home flight simulation help pilots in the real world?

Phil Coyle: Definitely. Aside from its value as a procedural trainer, the power of home flight simulation is multiplied when you’re not using it alone. You can connect your home flight simulator to a variety of online networks (VATSIM and PilotEdge, for example) so you’re flying and talking with others who have their simulator connected to the network.

You become part of an aviation ecosystem that lives and breathes just like the real air traffic system. Real people are unpredictable. They make mistakes and pose new challenges. Thus, flying online creates a more dynamic and engaging environment compared to flying in “single player” mode.

When using a simulator to pre-fly a lesson plan, flying online while connected to a network means you’re no longer practicing that flight in isolation. Instead, you’re flying along with other virtual pilots and speaking with a virtual air traffic controller, all of whom are real people practicing from home. The simulator now allows you to practice things like real-world air traffic control communications and negotiating your way into the traffic pattern of an uncontrolled airport.

If you’re using your simulator for fun, flying online allows you to do things you might never get the opportunity to do in real life, like practicing military formation flying or joining a “virtual airline” and replicating the real-world procedures of your favorite operator.

What can you do in a simulator that you wouldn’t try in the real world?

Ed Hopkins: You can learn so much from simulators and gain experience with issues such as engine or instrument failures that are too dangerous to attempt in actual flight.

For example, when you practice engine outs in a Cessna 172, you don’t turn off the engine because of the possibility that it might not start again. Instead, you bring it down to idle. But, you can experience actual “engine out” scenarios on a flight simulator.

Many simulators also have the ability to specify weather conditions, either built-in or with extra plug-ins. For example, you can practice landing in extreme crosswinds — a feat that would be dangerous in reality.

Can simulation help a pilot to gain skills?

Ed Hopkins: Yes, but there are limitations with desktop simulation software. Landing is probably the most difficult skill to learn as a pilot. Simulators are good, but don’t perfectly model the ground effect as you near the runway, especially with higher speed aircraft.

With simulation, you don’t get force feedback — what you would physically sense in an actual aircraft. You aren’t being pulled or pushed by the winds in a way that your brain’s internal gyros (eustachian tubes in your inner ear) can sense; the experience is purely visual. This is critical in Instrument Flight Rules (IFR) flight conditions when you enter a cloud and have no idea what is up or down, and your brain is confused due to the fluctuations in your inner ear.

Along with increased cockpit fidelity, key features of the XB-1 simulator include the addition of virtual hydraulic actuators, a wind gust model and flight-like mechanical systems.
Are there many flight simulator programs for home use?

Phil Coyle: The three primary home flight simulators used by the majority of the civilian flight simulation community are:

  • X-Plane by Laminar Research
  • Microsoft Flight Simulator 2020
  • Prepar3D by Lockheed Martin

Each of these simulators has its own strengths. Many “simmers” will choose to use more than one.

  • X-Plane brands itself as the most “realistic feeling” flight simulator, especially for flying general aviation aircraft. Most users agree it offers the best balance of flight dynamics, aircraft functionality, and visuals. It’s also the simulator that has the highest percentage of licensed pilot users on the platform.
  • Microsoft Flight Simulator is the newest addition to the civilian flight simulator lineup and represents the cutting edge of game development in terms of graphics. The simulator is still going through active development and has not yet reached the same level of realism and fidelity as other long-standing platforms.
  • Prepar3D (pronounced “prepared”) has a strong development legacy that dates back to 2006, and is known for being a stable simulation platform with a wide variety of realistic, study-level add-ons. As such, the simulator remains popular with enthusiasts who enjoy flying commercial aircraft to simulate real-world airline operations.

Beyond these three, DCS World is a popular choice within the military flight simulation community. There are even simulators such as Infinite Flight that are available on mobile devices.

Where can you fly a desktop simulator?

Phil Coyle: The best place to fly a simulator is your own home. If you’re interested in flight simulation, the best piece of advice I can give is to simply give it a try.

The process is straightforward: purchase a simulator (several are available as a $60 digital download), buy a basic yoke or joystick, and go for a “first flight” using a computer you already own.

Once you have a better idea of how you want to use the simulator — whether that’s real-world training, replicating airliner operations, or flying military formations with friends — you can begin to customize your experience further.

There are also resources such as the Flight Simulation Association that are geared toward helping people get started in flight simulation. Also consider attending one of the various flight simulation trade shows that take place annually, like FlightSimExpo. You’ll get the “try before you buy” experience when it comes to flight simulation hardware. Many aviation museums also have flight simulators you can try to give you a taste of the real thing.

Is the XB-1 simulator lifelike?

Ed Hopkins: The XB-1 simulator is as realistic as we can model with both software and hardware. But, there are things that can’t be modeled to truly mirror the real world. For example, it’s impossible to predict conditions at any given time due to the unpredictability of winds and weather.

However, Boom engineers can test their control algorithms aggressively with actual pilot input thanks to Boom’s resident test pilots who have similar experiences flying F-18s and F-22s. That means we can simulate flight issues at higher speeds and altitudes with immediate feedback from our pilots who have experienced the same issues in the real world.

Do all Boom employees learn to fly the XB-1 simulator?

Ed Hopkins: Every new Boom employee is invited to attempt to fly the simulator, sometimes on their first day. But it’s OK if you don’t land it the first time; you still keep your job.

Learning how to manage the unexpected is just one of the benefits of flying simulators. In addition to having fun, simulation can help people learn to fly and better understand airport and airline operations. Click here to learn more about Boom’s XB-1 simulator.


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