Flying Engine Testbeds: Everything You Need To Know

As aviation works towards reducing its carbon footprint, engine manufacturers are looking to make their products as efficient as possible. Before these can be deployed on commercial aircraft, they must undergo testing. While some of this takes place on the ground, the engines must also be tested inflight. This is where flying engine testbeds come into play.

Rolls-Royce Engine Testbed
Rolls-Royce uses Boeing 747s as testbeds for its new engines. Photo: Alan Wilson via Flickr

In use for decades

The emphasis on producing more sustainable engines has been a particular phenomenon in recent years. However, engine manufacturers have always strived to produce the best powerplants for their military, commercial, and private customers. Looking back in history, we can see that the use of testbed aircraft dates back at least as far as the 1940s.

Indeed, in the aftermath of the Second World War, former Avro Lancastrian bombers were put to use by UK engine manufacturer Rolls-Royce for such a purpose. These planes had four piston engines, and Rolls-Royce replaced two of these with its new RB.41 ‘Nene’ turbojet engines for test flights. If they failed, the plane could still fly on the two piston engines.

Rolls-Royce began making such test flights in August 1946, resulting in the first all-jet passenger flight from London to Paris in November that year. Later in the decade and moving into the 1950s, companies like de Havilland and Armstrong Siddeley also began using the Lancastrian as a flying testbed. In this sense, it helped to kickstart the jet age in the UK.

Avro Lancastrian Testbed Getty
The Avro Lancastrian fueled a postwar boom in engine testing. Photo: Getty Images

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What changes have to be made?

Using an aircraft as a flying testbed isn’t simply a case of removing one or more of its engines and replacing them with the powerplants that a manufacturer wants to test. The nature of the work means that such planes will typically be subjected to several other modifications. These ensure that whatever testing takes place can be carried out in a safe manner.

Work on the aircraft’s wiring typically forms a key part of this process. This ensures not only that the engine can run safely on the plane in question, but also that companies can collect necessary data from the tests. Structural modifications can also play a role, such as the removal of winglets on General Electric’s Boeing 747, according to ATDB.aero.

General Electric Boeing 747 Testbed
General Electric removed the winglets on its Boeing 747 testbed. Photo: JBabinski380 via Flickr

General Electric’s 747 testbed

As alluded to earlier regarding the Avro Lancastrian, four-engine aircraft are well-suited as testbeds as they offer greater contingency in the event of a failure. As such, it is unsurprising to see that several major engine manufacturers use the Boeing 747 to perform aerial tests on their new turbofan designs. One such manufacturer is Ohio-based General Electric.

This US engine maker flies N747GF as its aerial testbed. A 27-year-old Boeing 747-400, it formerly flew for Japan Airlines. It has been with the company since 2010, and tests engines like the GE9X. This turbofan is the only kind that will be used on the Boeing 777X. Data from RadarBox.com shows that GE bases N747GF in Victorville and San Antonio.

General Electric Test Flight
This December 2020 flight involving N747GF lasted more than seven hours. Image: RadarBox.com

Rolls-Royce’s two jumbo testbeds

There are also several engine manufacturers who have more than one aircraft that they use for aerial testing of new engines. For example, Rolls-Royce flies two different variants of the 747 for this purpose. The older of these is a 41-year-old 747-200, registered as N787RR.

As the registration suggests, it has been used to test Boeing 787 engines. Recently, this work saw the ex-Cathay Pacific jumbo used to test a Rolls-Royce Trent 1000 that ran entirely on sustainable aviation fuel. The flight in question lasted nearly four hours.

While Rolls-Royce has operated N787RR since 2005, its second 747 testbed arrived much more recently. Registered as N747RR, this 21-year-old 747-400 joined the company from Qantas in December 2019. Its testbed conversion is taking place in Moses Lake, Washington.

Rolls Royce, Trent 1000, Sustainable Aviation Fuel
Rolls-Royce flew a Trent 1000 engine on a blend of 100% SAF in October. Photo: Rolls-Royce

Pratt & Whitney Canada’s diverse fleet

Pratt & Whitney Canada does things slightly differently when it comes to its testbed aircraft. While, like Rolls-Royce, it operates a paint of 747s for this purpose, the aircraft in question are examples of the short-fuselage 747SP. Interestingly, it also uses a Dornier Do328‑300 JET and a de Havilland Dash 8-100 turboprop for such testing purposes.

The company bases its testbed aircraft at Canada’s Montréal-Mirabel International Airport (YMX). Data from RadarBox shows that its two 747SPs have both operated flights from there this month, despite each being at least 40 years old. C-GTFF entered service with Korean Air in March 1981, while C-GPAW did so a year earlier with CAAC in China.

Air China Boeing 747SP
This Air China 747SP has gone on to serve as a testbed for Pratt & Whitney. Photo: Aero Icarus via Flickr

Well-loved by engine manufacturers

Manufacturers worldwide are grateful for the opportunity to give retired passenger aircraft new leases of life to test their new products. Regarding the company’s ex-Qantas 747, Rolls-Royce’s Director of Development and Experimental Engineering, Gareth Hedicker, stated

The Queen of the skies will become the jewel in the crown of our global test programs. This is a significant investment that will expand our world-leading test capabilities even further, and will allow us to obtain more flight test data than ever before. (…) We’re excited to power it into the future.”

Pratt & Whitney Boeing 747 Testbed
Pratt & Whitney’s 747SP testbed, as seen in 2015. Photo: Gilbert Hechema via Wikimedia Commons

General Electric also relishes the chance to put new engines to the test on these aircraft. Its original testbed was a Boeing 747-100, which it retired aged 49 in 2018. Praising its versatility, General Electric’s Chief Test Pilot Gary Possert stated that:

We found the airplane was very adaptable to any engine that we came up with at GE, big and small.”

Overall, testbed aircraft represent an enterprise that benefits aircraft both old and new. It keeps aging passenger aircraft active for longer than might otherwise have been possible, while also expediting the development of modern and efficient engines for new planes.

Have you ever seen a testbed aircraft on your travels? If so, which company did it belong to? Let us know your thoughts and experiences in the comments.

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