What is an Iron Bird?

Boom’s first Overture aircraft will never actually fly, purposefully.

Instead, it will be an iron bird, a full-scale model that will be used to test and integrate Overture’s flight components and systems, software, and hardware-in-the-loop (i.e. physical components that will actually move). The Iron Bird building also maximizes safety, as it represents an opportunity to test and validate all critical systems before aircraft production launch in 2024 at the Overture Superfactory in Greensboro, North Carolina.

Overture’s iron bird will be approximately 200 feet long and 100 feet wide. It’ll be a steel skeleton structure, which will identically represent the most critical dimensions of the airplane for the hydraulic systems and electrical wiring.

Boom announced at the Farnborough International Airshow that it will construct its first full-scale model of Overture in Centennial, a suburb of Denver, Colorado. Overture is capable of carrying 65–80 passengers at twice the speed of today’s airliners and running on 100% sustainable aviation fuel (SAF). It will fly Mach 1.7 over water with a range of 4,250 nautical miles.  

Overture’s iron bird will be located at Boom’s new 70,000-square foot facility — called The Iron Bird — that will house the systems integration labs (SIL), which includes the iron bird test model and fully functional flight deck simulators.

The building will be completed with an Overture cabin mockup and a virtual visualization room that uses a unique combination of virtual and augmented reality programs to aid in remote design of production aircraft assembled at the Overture Superfactory.  

Eli Oleksiak, who leads Boom’s Avionics & Electrical Systems Engineering team, and Nate Hepler, Group Head of Test Engineering, explained why this is such an important milestone for new aircraft development.

Ok, so what is an iron bird?

Eli Oleksiak: We treat the iron bird as our first aircraft.

An iron bird is a structural model representation of the aircraft. The intent of the iron bird is to test the integration of each of the aircraft systems — software and hardware-in-the-loop, flight controls, hydraulics, actuators, load systems, avionics, wiring, and landing gear — to make sure they function properly together.

Nate Hepler: It’ll be a full scale size of the aircraft, but won’t be built exactly the same — though it will have a similar structure. Given the iron bird doesn’t have to fly, it won’t have pressurization, be able to carry the loads, or have skin, like the actual planes will.

When we say iron bird, it will really just be the system’s components.

Why build an iron bird and not just test on a real plane?

EO: There are several reasons to build an iron bird before flying an actual Overture aircraft: a couple of reasons are for risk and schedule reduction. Any bugs or issues we want to work out, we can do so safely on the iron bird before we initiate ground and flight testing.

NH: The iron bird allows Boom to test failure conditions and verify that the redundant flight-critical hardware and software will properly protect the airplane and crew. In this scenario, because we will have an iron bird, we can intentionally fail something to see how all systems continue to function, from the safety of the ground.

With the iron bird, pilots will still be sitting in a flight deck and flying a plane to evaluate human factors while looking at the data. For many test conditions, it’s more cost-effective to conduct tests in an iron bird. And in the case of the most critical failure conditions that would never be flown intentionally — but for which the airplane must be capable of continued safe flight — it’s the only way to conduct the test.

These simulators will be on platforms in front of the iron bird. In addition to pilots during testing, we’ll also have control stations all around so engineers can sit and look at all the data the person in the cockpit is generating. The engineers will be able to evaluate it against key test criteria in real-time.

Why will it be in Denver and not North Carolina?

EO: The iron bird is an engineering and development asset and is intended mostly for systems integration testing, not as much of a manufacturing asset, which makes Colorado a better place to build it since our engineering team is here. But with that said, there are things we will learn from the iron bird that we will use to aid in the production of Overture in North Carolina.

NH: Our iron bird will be functioning throughout development and well into service with our customers. Having the iron bird will make it easier to change something on the aircraft even during flight tests or the manufacturing process.

What teams will work on the iron bird?

EO: The test engineering team will be the group configuring the iron bird, getting it built, designing the building, and working with systems teams. Eventually, this team will help plan out the actual tests done on the iron bird.

The Avionics & Electrical Systems team which is responsible for the Integrated Modular Avionics (IMA), electrical systems, flight deck development, and Electrical Wiring Interconnect Systems (EWIS) will be completing a lot of integration and regression testing throughout development.

Electro-Mechanical systems will also be utilizing the iron bird a lot since they own the flight controls, hydraulics, and landing gear. And the avionics team will also play a large role since everything interfaces through Integrated Modular Avionics (IMA), which is basically the brains of the aircraft.

But, you also can’t forget the pilots and human factors who will be working in the flight deck on the iron bird. We’ll have two flight decks at our Iron Bird facility — one on the iron bird and another next to it, where we’ll be doing avionics & human factors testing, along with first flights and simulation.

NH: It’s on the second flight deck simulator where we will look at pilot movements, pilot actions, and pilot workload. The pilots will make sure all the lights and colors make sense in the flight deck. In this case, one person can be in the first simulator using only software and simulation, and the other can be in the second simulator using hardware, physically moving components on the iron bird.

What we are doing that most aircraft manufacturers don’t do is we’ll be able to control the iron bird with either one of the flight decks.

How long have iron birds been a part of the new aircraft development process?

EO: Over the last 40 years, iron birds have changed significantly and become more technologically advanced. They used to just be mechanical and now we’ve added new technologies and the front end of the aircraft, where we have software and hardware-in-the-loop. We now have full integration of aircraft systems.  

NH: The Society of Automotive Engineers (SAE) has an Aerospace Information Report (AIR) out there about industry standards (SAE AIR 5992), which documents decades of iron bird usage. It is not mandatory to build iron birds before creating a new aircraft. Often, if you’re building a smaller aircraft, you’d test each system separately, so an iron bird wouldn’t be necessary. The larger the aircraft is and the more highly integrated it is, the more you want to do this.

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In 2024, Boom will begin production on commercial aircraft at the Overture Superfactory. The first Overture aircraft is slated to roll out in 2025, fly in 2026, and carry its first passengers by 2029.

To browse open positions at Boom headquarters, The Iron Bird, and the Overture Superfactory, please visit the Boom careers center: /careers