Eurocopter is promoting a new performance class, “PC2 defined limited exposure” (PC2 DLE), for twin-engine helicopter takeoffs and landings at oil platforms and other elevated helipads, to minimize the risk in case of failure of one engine while overcoming the drawbacks of existing performance classes.
One focus of improving on the widely used PC2 Enhanced (PC2e) class is its 30-foot requirement, according to Gilles Bruniaux, Eurocopter’s v-p for fleet safety. Under PC2e, the helicopter is supposed to climb to 30 feet (above the helipad), the practical rotation point height at takeoff, before it flies away. In the event of an engine failure before it reaches that height, the helicopter will lose altitude and the surviving engine will not have developed enough extra power to prevent a hard landing and airframe damage. However, the passengers will be safe. If an engine fails above the 30-foot height, the helicopter will be able to escape without the tail striking the helipad’s edge.
PC2e was itself supposed to be an improvement over another performance class, PC1, which has a 20-foot-high rotation but an exposure time of nine seconds. Regulatory authorities accept that if one engine fails during this period of time, there is a risk of crash or strike.
However, a rotation point of 30 feet versus 20 feet “increases the risk of losing situational awareness,” Bruniaux contends, and raises the risk of obstacle strike on the platform. In fact, obstacles, platform movement and night can combine to make the probability of obstacle strike higher than that of engine failure. Eurocopter flight-test pilots say that the difference of 10 feet has a safety impact.
The PC2e class was supposed to improve upon the PC1 class by addressing the fact that after engine failure on a twin the surviving engine does not provide its emergency power instantaneously. PC2e aims to ensure that, if one engine fails, the helicopter will not land hard or strike the helipad’s edge.
With PC2e, however, some other safety margins are reduced. For example, compared with PC1, PC2e allows a shorter distance between the tail and the helipad’s edge when the helicopter flies away.
PC1 might be more attractive than PC2e were it not for the fact that the helicopter must remain lightly loaded to conform with PC1, thus limiting payload.
With these drawbacks in mind, Eurocopter has conceived PC2 DLE after establishing a working group to develop a takeoff and landing procedure that takes into account “all external and material factors.”
The airframer developed the PC2 DLE procedure in collaboration with “oil companies, regulatory authorities and major oil-and-gas operators such as Bond, Bristow and CHC.” It determines the period of exposure during takeoff (from zero to nine seconds) depending on platform height, aircraft weight, outside air temperature, wind and so on.
The operator can choose to keep the 30-foot requirement or it may adopt a “climb to 15 feet and fly away” procedure. It can choose its exposure-time-versus-payload compromise. Bruniaux said exposure time will most often be close to zero.
“This is consistent with the philosophy of safety management systems: giving responsibilities to the operator,” Bruniaux said. He also emphasized that the exposure times should be seen as maximums. “The remaining engine often provides more power than the guaranteed minimum,” he explained. And the power loss in an engine failure is not instantaneous.
The PC2 DLE is expected to comply with the in-the-works EASA OPS 3 regulation in Europe.
It is now offered to operators in the form of an appendix to the flight manual, already available for the EC155 and the EC225. An operator may use it if its national aviation authority agrees. The OGP oil industry is working with Eurocopter and other manufacturers to agree on extending the new performance class to makes other than Eurocopter.