The EC725: Air-to-Air Refueling

Hot on the heels of the technical qualification(1) issued by Eurocopter, the French air force conducted a campaign in Italy last summer to test the air-to-air refueling capability of the EC725.

 Courtesy of Italian Army
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As the helicopter flies in the wake of one of the tanker’s wings and engines, the main difficulty is flying through the turbulence created.

The campaign had two goals: To evaluate the air-to-air refueling capability of the aircraft and to define the training required to qualify pilots. Until now, air-to-air refueling for helicopters has only been performed by a relatively small circle of countries, including the United States and Israel, and an exclusive group of aircraft: The AS332 L2 Super Puma and a few U.S. tactical helicopters. Air-to-air refueling for helicopters is still a fairly innovative procedure therefore: It was certainly a ‘first’ for the French air force. Rotor Journal met up with Major Norbert Idelon, instructor and head of 02.331 squadron. Major Idelon is one of the first two pilots to be qualified by the Flight Test Center (FTC), which carried out the evaluation. The FTC is also responsible for the future training of pilots.

Why did the French air force introduce air-to-air refueling for the EC725?
Major Norbert Idelon:
Air-to-air refueling is essential because it greatly enhances the operational capability of the aircraft, and hence the air force. It considerably increases the aircraft’s range and endurance and removes the need for refueling stops on the ground with all the technical risks and logistical organization that entails. It makes far-away deployments, sea crossings and longer missions possible. We can even refuel over enemy territory, because the refueling can be performed out of the range of fire. In fact, air-to-air refueling is just one part of the huge leap forwards we have taken with the EC725.

Why was the test campaign conducted in Italy?
N. I.:
In France, we only have tankers for fighter planes, not helicopters, so an international protocol was signed to share the refueling capabilities of the air forces covered by the agreement, and Italy is one of the countries that signed the protocol. The tanker used in Italy—the most up-to-date Hercules C130J—is also the only one with a refueling capability that can fly at speeds of 105 to 130 knots with its flaps 70% extended.

What did you cover during the test campaign?
N. I.:
We were able to completely verify the EC725’s refueling capability: 120 contacts were made with the tanker, although not all of them involved an actual transfer of fuel. We notched up 25 flight hours, over 12 flights, flying at different speeds (110 to 130 knots) and altitudes (500 to 10,000 feet). We were able to refuel with the aircraft at its maximum weight, but the EC725 was not always given a full tank of fuel. One of the aim’s of the campaign was to measure the aircraft’s refueling capability when it was carrying a full operational load so we therefore simulated, for example, the presence of 15 commandos on board.

Talk us through the main difficulties of air-to-air refueling?
N. I.:
As the helicopter flies in the wake of one of the tanker’s wings and its engines, the main difficulty is flying through the turbulence created by the tanker. You need sufficient reserve power to do this. Next, we have to factor in the parallax error caused by the position of the probe, which is on the right-hand side of the aircraft. All this requires a high level of technical skill from the helicopter pilot, just as it does in an airplane. The pilot also has to be very careful bringing the moving drogue and probe into contact.

How do you rate the flight qualities of the EC725?
N. I.:
First up, the aircraft has sufficient power to provide extra safety when flying in low altitude turbulence. And, in terms of aerodynamics and flight qualities, the aircraft is just perfect for refueling. The autopilot and the user-friendliness of the instrument panel also help the pilot greatly. What’s next? N. I. t We are going to conduct a qualification campaign for our crews and a night flight test campaign. Four conversion flights are recommended for the pilots to be able to refuel on both sides of the helicopter, firstly sitting in the right-hand seat, then the lefthand seat (the tanker has a refueling pod under each wing). The helicopter is also equipped with night vision goggles, which will make refueling at night much easier.

(1) See Rotor Journal No. 75



 Courtesy of Italian Army
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During this test campaign, 120 contacts were made over 25 flight hours (not all involved an actual fuel transfer).

WITH ITS FIVE- BLADED SPHERIFLEX ROTOR and its twin Makila 2A engines, the EC225/ EC725 combines the agility of a smaller aircraft with considerably more power.

ITS FOUR-AXIS AUTOPILOT 4 AXES provides exceptional hover capture and control.

ITS MAIN GEARBOX can run for 30 minutes without oil.