Features Procedures Safety & Training
The Versatile NH90

What do you do when your nearly 11 tonnes of helicopter is fully
inverted at a 45-degree up-angle? If it's the NH90 and you're Denis
Trivier, the flight test engineer, you trust that test pilot Philippe
Boutry knows what he's doing. Trivier was in the back of one of five
NHIndustries (NHI) prototypes, PT2, as Boutry, with fellow test pilot
Jean-Claude Rabany in the other front seat, dazzled the crowds at the
2003 Paris Air Show.

Although
not quite a loop, the manouevre, which demonstrates the NH90's
responsiveness, begins with a 45- degree dive, a gradual pull up into
the opposite up-angle and then a graceful 180- degree roll to
starboard. That leaves the aircraft standing briefly – but dramatically
– on its titanium main rotor hub and four composite blades before
Boutry, a former French navy pilot, brings the nose up (down in this
case). That returns the NH90 to a more normal attitude, ready for the
manouevre to be repeated in the other direction.

Trivier has
reason to trust Boutry in that they and Rabany know the twinengined
NH90 inside out. They have worked closely with the aircraft ever since
the first 40-minute flight of PT1, in December 1995, at the Eurocopter
plant in sun-drenched Marignane in the south of France. In essence,
they reflect the confidence NHI has in the ability of its new flyby-
wire helicopter to prevail in the competition to replace Canada's fleet
of Sikorsky CH-124A Sea King shipborne helicopters.

"It is very
agile," Trivier said in an interview shortly after the aircraft had
been shown off to French President Jacques Chirac. "These types of
manoeuvres are not normally done during flight tests – only for air
shows, to demonstrate the agility." As for the near-loop, it translates
as a "reverse 45-degree figure" and Trivier was careful to explain that
while it is clearly within the NH90's capabilities, "we cannot
authorize everybody to perform this." Evidence of the aircraft's brute
power is that during initial testing in Marignane, it was able to hover
out of ground effect on one engine at an all-up weight of more than 10
tonnes with absolutely no loss of height.

Throughout
demonstration flights, all stresses on the highly-instrumented PT2 are
measured continuously. "We never exceed the stresses in the blades or
in the hub and so on," Trivier said. "It's also a question of the
pilot's ability to perform this manouevre. Not all are used to flying
on their back."