How Collins is adapting its actuators for eVTOL aircraft

Avatar for Elan HeadBy Elan Head | May 4, 2021

Estimated reading time 10 minutes, 31 seconds.

Collins Aerospace, a unit of Raytheon Technologies Corp., has more than 50 years of experience in designing, certifying, and manufacturing actuation equipment for a wide range of commercial and military airplanes and helicopters. Collins actuators open and close the weapon bay doors on the Lockheed Martin F-35 stealth fighter, for example, and the company was recently selected for the U.K.’s Tempest next generation combat air system project. Collins will also be supplying actuation systems for the Aerion AS2 supersonic business jet.

Now, the company is applying its expertise to the eVTOL industry, developing compact, lightweight electromechanical actuators to meet the needs of a new generation of electric aircraft. We caught up with David Chard, business development director for Collins’ actuation systems business, and Keith Bloxham, engineering manager, research and technology, actuation systems, to learn more about the considerations for actuators in eVTOL aircraft.

Collins helicopter actuators
Collins actuators are used in many traditional aviation applications, including rotorcraft. Collins Aerospace Image What are some of the key requirements for actuators in eVTOL aircraft, and what are some of the challenges in achieving these objectives?

David Chard: [One thing] we see in this market space are nonconventional power supplies. Typically, in a fixed-wing application, it has a generator that comes off from the engine and provides a fixed or variable frequency AC supply. Now we’re going to have to use a supply that comes from batteries with the challenges associated with that.

There are also key requirements for redundancy. Electric actuation has a tendency to fail fixed, so the way [vehicle designers] are overcoming that is with multiple rotors, multiple surfaces. And they need actuators that can fit in smaller envelopes. I suppose [another] thing to point out is more integrated structures, so now they’re coming to us and saying, “We want an element of the structure that can move as well, not just the actuation system.”

Keith Bloxham: Like David said, we typically deal with some major airframers — Boeing, Airbus, Gulfstream, those types of customers — and they have very regulated power supplies, conditioned power supplies and they expect from us as well that we don’t add any disruption to their power supply that powers multiple systems. So we’re heavily constrained in traditional aircraft in how we interface with their systems. This is slightly different with batteries; the voltage will fluctuate. So you have to design your systems based on specific minimum requirements for that particular battery condition at any point in the regime and then also you have to have your equipment capable of operating at different voltage levels, so that’s also a challenge.

The other side David mentioned is the redundancy. Typically, on traditional aircraft, we would have multiple actuators per flight control surface; we have redundancy at a flight surface level. These new electric smaller vehicle concepts have multiple flight control surfaces — significantly more than a traditional aircraft. So now you’re moving away from your traditional ailerons, rudders, elevators and going towards a multifunction type surface, typically with a propulsion system attached to that surface as well. So that’s an interesting challenge, but it also opens up opportunities for more electric actuation because now those failure modes are less critical, because you can sustain a loss of a surface or a hard-over of a surface by counteracting with the other surfaces.

Collins electromechanical actuator
A typical Collins electromechanical actuator that could be used in an eVTOL aircraft. Collins Aerospace Photo Given some of these challenges and also the diversity of eVTOL designs, to what extent are you able to leverage your existing actuators and actuator technology, and to what extent are you starting from scratch to address some of these issues?

Keith Bloxham: A lot of the technology that we’re applying to these vehicles are things that we’ve been working on for a number of years now. So we’ve been progressing through from our traditional hydraulic fly-by-wire actuators, through to electro-hydrostatic type actuators that provide the functionality of an electric actuator, and now moving towards electromechanical actuation.

As we progress through, we’re presented with a number of challenges. One of the main ones on a traditional aircraft is jam tolerance; you can have a flight critical surface that jams and you can’t do anything about it. So we have to look at methods of handling those issues, and failure modes, and that’s all being wrapped up into these actuators now that we’re presenting. We’ve developed the functionality for all these issues through more traditional airplanes, and now we’re applying it to [eVTOL aircraft]. Weight is a big concern for eVTOL aircraft. Are you finding particular challenges in designing very lightweight systems?

Keith Bloxham: Weight is always a challenge on aircraft for obvious reasons, so we’re always being driven to reduce weight on the aircraft. In the traditional aircraft world, there’s a lot of interest in the move towards thinner, high aspect ratio wings; they’re looking to improve the efficiency of aircraft and trying to get components within the smaller space envelope. So that’s a challenge that we’re addressing anyway.

We’ve got some approaches that we’ve been looking at to reduce the weight of these actuators, and part of it is wrapped up in new requirements for these types of actuators. So we can’t come from looking at a traditional actuator and try and make something that fits these applications; we have to basically go back to the drawing board and look at what do we actually need, what’s suitable for these type of applications, and how can we modify our approach to designing and building actuators so that we can reduce the weight, reduce the volume, and make it viable. A lot of eVTOL developers are targeting very high-volume operations. In terms of scaling up manufacturing, do you anticipate any challenges in mass producing these actuators, possibly at a scale that hasn’t been seen in aviation before?

David Chard: [The eVTOL industry] is currently in the concept phase, moving into the new and novel phase before it transitions into full-volume production, so we’re probably quite a long way off from that, at the moment. We do relatively high volume at some of our facilities. Our [Wolverhampton] U.K. facility, for example, does [actuators for] the A320 aircraft, which is the highest production aircraft in the world at the moment. We’ve got the Banbury [U.K.] facility that currently does composite manufacturing, and that is high-volume as well. So I don’t see it ultimately as a problem. I think for us, we’ll look at bringing in more automation as we go to these bigger volumes. We look at the experiences that we have in the likes of Banbury, automating the production line, and taking the experience from automotive and applying it there. What types of eVTOL customers are you looking to work with?

David Chard: For us, we’re trying to focus on solutions that solve critical challenges in that particular market. We’re looking at applications that would bring our expertise in terms of development, certification, and manufacturing. We’re looking at things that leverage the innovation and the investment they’re already making across Collins Aerospace, and we’re looking at partners that have a focus on safety and a longer-term plan to develop the ecosystem as a whole.

This interview has been edited and condensed.

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