An Update on the X3: A Conversation with Hervé Jammayrac
07/02/2011: During the Paris Air Show, Second Line of Defense talked with Experimental Test Pilot Hervé Jammayrac of Eurocopter. Jammayrac provided an update on the aircraft and the test program. In many ways, the new helicopter was a star at the airshow, bereft of many new flying aircraft.
Photo Credit : SLD
The X Cubed has been designed to be a low cost solution to a high-speed helicopter. Given Eurocopter’s pole position in the oil and gas industry, the new helicopter should clearly be a key player in this marketspace. The reliance on power by hour contracts in this business means as well that a lower cost solution to high speed is important as well. And given a solid base in this industry, Eurocopter can go on to market to security and military services. Another potential might be operating on smaller ships in the future as well, perhaps even including the LCS.
Currently, the test aircraft is using a Dauphin airframe with NH-90 engines in addition to the turboprops. But Jammayrac indicated that Eurocopter might well look to a larger airframe for the production model.Another aspect of the interview was how the test pilots are linked into the development process. As Jammayrac underscored:
That’s a way to get a very deep knowledge of the aircraft because you know precisely how it was built. And from that, you are able — you know the limits very easily, so it makes flying the aircraft a lot more efficient.
SLD: Could you describe how the helicopter basically works? And basically it is a helicopter?
Hervé Jammayrac: This aircraft is a helicopter. And that, I think, is the key point for us. Then we wanted to go faster. How can we go faster? We are limited on a conventional helicopter because you have to tilt the rotor, and you have also the problem of an advancing blade that becomes trans sonic. So to overcome these two problems, the idea is to fly level. Zero incidents, flat pitch so you have a reduced drag, and then the propulsion.
You need to bring the propulsion in another way, so that’s why we have installed these two propellers in order to be able to create this forward thrust. That’s the general principle. In order to accelerate, because of this advancing blade becoming trans sonic we have to reduce the rotor speed. Since we reduce rotor speed, we lose some lift, and then that’s where we have the wings that comes into play and the wings are going to get, let’s say, about 40 percent of the lift at cruise speed; forty percent of the lift at cruise speed is provided by the wings.
Everything is linked together. You have the main gearbox. We have the two engines that are running the main gearbox, and then you have the two propellers that are also connected to the gearbox. Imagine, for example, on a conventional helicopter, you have the tail rotor, you have a shaft connecting to the tail, so we have removed this, and we have put it on the side, and we have both of them. Overall, we are able to do some anti-torque with differential pitch on the propellers, and the same controls are also giving us the thrust in forward flight.
SLD: We have flown the Osprey and a key element of flying the Osprey is the transition from vertical to horizontal operations. How does this bird work?
Hervé Jammayrac: That’s an interesting question because there is a very fundamental difference. It’s a lot simpler because you have no transition. You have always available both controls. In hover, you are hovering like a helicopter. When you want to accelerate, there is a dedicated control, which controls longitudinal acceleration or deceleration. And so you just accelerate, and that’s it. And if you want to decelerate in the flight, you decelerate. And once you need to compensate for the descent, you have the corrective. So you cannot stall. That’s a huge difference. In my opinion, it’s even simpler than flying a conventional helicopter where you have to do constant pitch change.
SLD: What is the top speed, which you have flown so far?
Hervé Jammayrac: We have flown at 232 knots in flight.
SLD: What is your background in flying helos?
Hervé Jammayrac: I’m a test pilot. I’ve been flying, let’s see, I don’t know how many different types of helicopters, probably around 30 types of different helicopters.
SLD: What was the most pleasant surprise from your point of view looking at this? It’s a strange animal.
Hervé Jammayrac: Where we were really surprised was by the capacity of climb and descent, and this capacity also to accelerate and decelerate. This is quite new feeling. And you see that in the flight demonstration at the Air Show, being able to climb at 60 knot and 50 degrees slope and maintain this flight condition as long as we want.
On a commercial aircraft, you would not be climbing at this kind of slope, but the capacity to climb very quite fast from your takeoff altitude to your cruise altitude is interesting in terms of fuel flow setting, because you can be in three minutes at your cruise altitude for example. So that’s interesting. This is totally unique. Even in the cockpit, you feel that as something being different.And this climbing capacity for the military is also very interesting because, for example, imagine you’re picking up some people on the ground, and you want to get out of the area as far as possible.
SLD: Is the technology used on the aircraft in house technology and parts?
Hervé Jammayrac: It is except for the turbo prop propellers. They are made by a well-known German company and are made out of wood. It is a natural composite, and for propellers, it’s one of the best materials that you use.
SLD: What tests are you running next?
Hervé Jammayrac: We have not, I would say, expanded the flight envelope totally. Now we want to check for lateral maneuverability and stuff like that. But from what we’ve seen so far, it’s just a question of gathering the data.