A helicopter with 2 fuel cell stacks where the rear seats used to be flew a full airport circuit over Quebec and landed with its battery still above 80 percent, while its hydrogen tank hangs outside the cabin on purpose

A wet apron at a regional airport in southern Quebec, low cloud, a small white helicopter warming up.

Behind the pilot, where two passengers would normally sit, there is a gray box instead.

Under the tailboom hangs a cylinder that does not belong on this airframe.

That software is the least visible and possibly the hardest, because it decides moment by moment how much current comes from chemistry and how much from the battery.

The machine lifts, climbs, flies a rectangle around the field, turns onto final and lands.

Nothing came out of it but water vapor.

The flight lasted one circuit.

Why a rotor is harder to feed than a propeller

A fuel cell produces electricity by combining hydrogen with oxygen from the air, and its output is steady by nature.

That suits a cruising airplane, which asks for roughly the same power minute after minute.

A rotor does not behave that way. Hovering demands enormous power, and it arrives and disappears in seconds as the pilot works the controls.

A stack cannot follow those swings, because the chemistry inside it needs time to respond to a step change in load.

So the conversion pairs two stacks with a battery that absorbs the transients, handing out current faster than the chemistry can and taking it back when demand falls.

The stacks supply the average. The battery supplies the surprise.

What is bolted into this airframe

Two proton exchange membrane stacks sit in parallel in the cabin, filling the space a rear bench occupied.

An electric motor drives the rotor where a piston engine once sat, and radiators handle the heat the stacks throw off.

The tank rides outside, clamped beneath the tailboom, holding compressed gas at 10,000 pounds per square inch.

Keeping it outboard is a deliberate early flight precaution, and it carries only a few pounds of hydrogen, which is why endurance is short.

A cryogenic tank holding about 1,500 gallons is going into the site to supply a liquid hydrogen version later this year.

Compressed gas is the test article. Liquid is the plan.

The number that settles the obvious objection

Any reader of a story like this asks the same question. Did the fuel cell fly the aircraft, or did the battery?

The answer is in one reading taken after the wheels stopped. The battery came back with a state of charge well above 80 percent.

That figure is the whole argument. A battery that ends a flight nearly full was buffering, not propelling.

Had the stacks been underperforming, the battery would have drained to cover the shortfall and landed low.

The team has not published a duration for the circuit, so endurance stays the open number and the reserve does not.

The circuit was flown in April, and a second one followed in May, which matters because a repeatable result is worth more than a first.

One flight is a demonstration. Two is a procedure.

Where this sits against everything else flying on hydrogen

Fixed wing hydrogen aircraft have been flying for years, and one flew in April carrying far more weight than this.

That machine was uncrewed, reached about 984 feet, covered 22 miles and burned liquid hydrogen in a turbine rather than running a fuel cell.

What has not been done before is a piloted rotorcraft completing an entire traffic pattern on fuel cells, and that is the claim here.

Rotorcraft matter to this argument because the vertical flight duty cycle is the hardest case, so solving it settles the easier ones.

The operator is an unlikely one as well, a Canadian arm of a biotech firm that wants clean aircraft to move manufactured organs between hospitals.

Making the fuel is the other half, which is why sites keep pairing turbines directly with an electrolyzer rather than buying delivered gas.

The tank pressure, the stack arrangement and the battery reading are described by an aviation title.

A hover is a hop. A circuit is an aircraft.

What certification actually demands from here

The aircraft flies under an experimental permit, which allows a test pilot aboard and nobody else.

Four things need approval separately before that changes. The stacks, the tank, the motor and the software that blends them.

That software is the least visible and possibly the hardest, because it decides moment by moment how much current comes from chemistry and how much from the battery.

Regulators on both sides of the border are being engaged in parallel, and the pathway for this class of propulsion is still being written.

Conversion work began with ground runs in late 2023, so roughly 28 months of incremental testing sit behind a single lap of an airfield.

Permitting is the slow half of every hydrogen build, as a German site found while waiting on a plant permit.

The flight date, the pilot and the program partners are set out by an industry body.

The rotorcraft works, and what stands between it and a passenger is four approvals and a lot of paper.