EC175 Main Gearbox Features New Run-dry Design
The EC175’s main gearbox has no backup lubrication system
[Updated 7/22/14 to clarify some points.]
Unlike its sister ship the EC225, the EC175’s main gearbox has no backup lubrication system, which could present a problem should it experience a total loss of oil. To compensate for this, its components have been designed to withstand the absence of lubricant for a limited period of time. Airbus Helicopters so far has certified a 15-minute dry-run capability (which involved a 30-minute demonstration). Further tests are scheduled for 2015 in a bid to increase the certified duration to at least 30 minutes.
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On the EC175, Airbus Helicopters engineers have designed the main gearbox so that its components can withstand the effects of complete loss of lubricant without an emergency lubrication system. The manufacturer said it has demonstrated dry-run capability of 30 minutes so far, in line with airworthiness requirements.
Under a newly introduced rule, a safety factor between the run time actually demonstrated in bench testing and the time limit shown in the aircraft flight manual has been applied, an EASA expert told AIN. A 30-minute demonstration on a test bench has therefore earned the following wording in the flight manual: “Land as soon as possible. Maximum flight time: 15 minutes. Note: Main gearbox loss of oil capabilities have been demonstrated on a bench test (AEO condition, IAS = Vy) for 30 minutes.”
Airbus plans to conduct more tests next year to extend the flight-manual run-dry time limitation.