eVTOL ejection seats: testing times
September 25, 2024
Flight test campaigns are undoubtably an exciting element of an upcoming aircraft’s journey towards type certification. With test flights typically performed to verify, quantify and explore an aircraft’s flight characteristics and handling qualities, this airborne element offers opportunities unmatched by modelling or simulated substitutes. However, although all flight test campaigns are always approached with a firm focus on safety, perhaps nowhere is this so pronounced as in the testing of an entirely new category of aircraft – such as the myriad eVTOL designs currently undergoing development.
Adding an ejection seat
Vertical Aerospace’s second full-scale prototype (unveiled in July 2024) incorporated a notable list of upgraded and evolved elements as compared to its predecessor: featuring around 60% of elements from strategic partner suppliers (up from a previous 10%) and Vertical’s new proprietary propellers. It also features an ejection seat, presumably something the minor redesign of the cockpit roof – a transparent square-shaped canopy extension directly above the pilot’s head – will facilitate the deployment of if required.
“Safety is our top priority as we progress through our piloted flight test programme with our latest VX4 prototype,” confirmed a spokesperson for Vertical Aerospace. “The ejection seat is only being installed in our prototypes, not our certification aircraft, and was purchased from a specialist equipment company”.
Configurational considerations
Collins Aerospace, one of two major Western ejection seat manufacturers worldwide, clarified: “Depending on the seat manufacture and variant, and inclusive of the rails, propellant catapult and actuator, any ejection seat will typically weigh in the hundreds of pounds”.
Rival British company Martin-Baker did not comment on average weight of their currently available ejection seats – which, with the exception of separate crashworthy products, have been fitted exclusively in military applications to date. Vertical has not publicly stated which original manufacturer’s model it is integrating into its test aircraft, which also does not yet appear to include the red triangle on the fuselage denoting a ‘live’ seat.
Nevertheless, the not inconsiderable additional weight an ejection seat and its surrounding structural elements represents is of crucial consideration to any eVTOL developer, with any option to lighten the load beneficial to the inherently power-intensive VTOL phase of flight. Given the new seat, the test campaign of Vertical’s latest-generation aircraft will certainly benefit from the aircraft’s 20% increase in power-to-weight ratio.
So why the need for it?
Flight testing is undeniably an area inherent with risk; something which must be assessed and mitigated wherever possible. Admittedly, unforeseen situations inevitably occur, such as the loss of Vertical’s first full-scale prototype in a ground impact (following a propeller blade release) in August 2023.
As eVTOL companies progress through their flight test campaigns – from initial tethered hover to free, forward flight – their aircraft are typically covering greater distances, operating at greater altitudes, and heightened speeds. As such, the integration of an ejection seat for emergency pilot egress may well be a sensible suggestion.
Balancing weight with functionality, the hypothetical suggestion of something like a Martin-Baker Mk8 seat – described by its manufacturer a “a simplified, lightweight version” of the “highly successful Mk10 rocket-assisted ejection seat” – might well fit the bill, explained an industry source. Introduced for primary trainer aircraft such as the Embraer and Shorts Tucano, “the most significant design simplification was the removal of the rocket motor to save weight,” continues its manufacturers’ website. However, with the Mk8 seat providing “runway level escape at speeds down to 70 knots,” it does not offer the ‘zero-zero’ (able to deploy with no altitude and no speed) functionality the Mk10 offers.
It’s important to remember the above remains speculative, and no eVTOL developer has yet specified seat variants either proposed or implemented for its test campaign.
Is there a precedent for it?
Admittedly, it’s an unusual move for a rotorcraft to include ejection seats. The Russian helicopter company Kamov designed the Ka-50 and Ka-52 with a live seat, with the helicopters’ rotors jettisoned by explosive bolts before the seats fired upwards. (However, whether multicopter or lift-and-cruise configuration, eVTOLs don’t face the same logistical conundrum.)
Famously, the Tu-144 Soviet supersonic passenger airliner also adopted ejection seats for its test pilots, although these were not included for the type’s commercial service.
However, it’s also not unprecedented for aircraft operators to approach specialist suppliers, with a handful of UK-based vintage jets currently regulated by the UK Civil Aviation Authority pursuing these options to secure ongoing operational support. When asked about potential eVTOL applications, “this is a live application and as such we can’t comment at this point,” stated a CAA safety spokesperson.
The idea of retrofitting an aircraft to incorporate an ejection seat for which it was not initially designed comes with its own challenges too, although with eVTOLs still in the development phase (rather than the modification coming post-certification), this does present additional flexibility.
For example, the de Havilland Vampire T.11 twin-seat trainer was retrofitted with ejection seats after entering service, while the rear cockpit of the Martin-Baker Meteor T7-and-a-half (used to this day as a company testbed for trial seat firings) features additional reinforced plating integrated far later in the aircraft’s life.
Suitability for eVTOL operations
Moving towards aircraft certification, there are a number of reasons why an ejection seat (let alone its integration into an eVTOL) is eminently unsuitable for commercial passenger applications. “Collins Aerospace has not been approached by an eVTOL developer to discuss ejection seats,” clarified the company, although added that Collins Aerospace (along with RTX company Pratt & Whitney) are “actively involved in many other aspects of the eVTOL market”.
“Given the myriad designs of eVTOL vehicles and the nascency of the market, we would need the eVTOLs to help us better understand the specific requirements and performance characteristics before commenting on ejection seat needs,” concluded Collins Aerospace.
Perhaps it’s just as well, that when the ‘flying taxi’ concept takes off, it’s only James Bond – well-known for fictitious ejection seats fitted to his road-going vehicles – likely to be going out with a bang. Until then, with safety first and foremost on both manufacturers and regulators’ minds, let’s hope Vertical’s test pilots are sitting comfortably.
