By Dominic Perry, FlightGlobal
Texas-based Otto Aviation is confident that by early 2027 it will have begun flight tests of its Phantom 3500 – an envisioned super-midsize business jet that harnesses an ultra-low-drag, lightweight design to enable flights of up to 3,700nm (6,850km) while burning 50% less fuel than rivals.
Chief executive Paul Touw says initial wind-tunnel testing has already delivered strong validation of the jet’s full laminar flow characteristics, which he believes will provide “breakthrough performance”, cutting drag by 35%.
Those tests, carried out in 2024, “surprised even us”, says Touw. “We didn’t think we would be able to take that much energy out of a flight.”
Designed partly with AI-supported technology, the ultra-sleek jet even dispenses with passenger windows to optimise the laminar flow along the fuselage.
Otto claims the jet’s ultra-low-drag characteristics will allow it to match the range and performance – including passenger capacity – of competing aircraft like the Bombardier Challenger 3500 and Embraer Praetor 500, but at almost one-half the maximum take-off weight (MTOW).
At its estimated 8,618kg (19,000lb) MTOW, the Phantom 3500 sits at the top of the US Federal Aviation Administration (FAA) Part 23 category, rather than the more-stringent Part 25 category occupied by other super-midsize types.
As well as offering a simpler route to certification, the lighter design also means smaller and lighter engines that are cheaper to maintain can be used, adds Touw.
While the Phantom 3500 is to be powered by a pair of Williams International FJ44s – each rated at 3,600lb thrust (16kN) – the competing Bombardier and Embraer aircraft use variants of Honeywell’s HTF7000 family in the 6,500-7,300lb thrust range.
Otto is presently working with its supply base to perform a preliminary design review (PDR) for the Phantom, a milestone that should be concluded in October this year.
Long-lead items for the jet – including complex forgings and castings, plus the engines and avionics – have been ordered ahead of final assembly of the initial flight-test aircraft next year, says Touw. He forecasts a maiden sortie in early 2027, or “around 20 months from now”.
That aircraft – and three siblings – will all be in a production-conforming configuration, potentially cutting the time to reach certification, a process for which the company has allocated three years of testing. “But if the FAA likes what they see then it could be two-and-a-half,” he adds.
Although there is inherent schedule risk in dispensing with a prototype aircraft, Touw says the move is supported by Otto’s strategy of seeking mature aerospace suppliers and in-production components, like the Williams engines.
“The FAA doesn’t care about the aerodynamics,” says Touw. “They want to know it can perform the appropriate tests.
“Outside of the outer mould line, [the Phantom] is just another aircraft programme – one with a lot of pre-existing parts on it.”
Other suppliers lined up for the programme include Leonardo, which is to build the all-composite fuselage at its plant in Grottaglie in southern Italy, and Mecaer Aviation, which is to provide landing gear.
Yet to be determined is who will build the wing. Here, there is “still a little bit of a bake-off” between potential suppliers, says Touw. In addition, although the avionics provider has been chosen, Otto has yet to disclose their identity.
Despite the intention to certify the Phantom 3500 as a Part 23 jet, Otto will incorporate some requirements from Part 25, opening the potential to hop up to the higher weight class in the future, adding additional fuel capacity to take range out to as much as 4,300nm.
“Then we have got an intercontinental aircraft,” he says.
On top of which, Otto sees the “super laminar flow” concept as applicable to a future regional jet with around 75 seats that offers the economy of a larger narrowbody.
Touw is confident that over the coming decades cash flow from the business “will be more than enough to tackle a regional jet”.
In the meantime, however, Otto is in the middle of a Series B funding round that is seeking “hundreds of millions of dollars,” he says, an activity that “should be complete by the end of this year”.
Touw describes the Phantom as a “one-billion-dollar programme” – although only around one-half of the total is directly for aircraft development. The remainder – to be sourced through debt or leasing – would be focussed on setting up a final assembly line.
He forsees little difficulty accessing funding required, citing the appeal of the jet’s environmental credentials, calling it a “sustainability afterburner”.
In addition to reduced fuel burn, the design also promises a reduction in contrail formation through its cruise altitude of 50,000ft, which as well as contributing to the overall drag reduction, is well above the atmospheric regions in which the artificial clouds form.