FRAGMENT CONTAINMENT
This AMC supplements FAA AC 29.903 with regard to the credit that can be taken from engine manufacturer data substantiating the capability of the engine to contain fragments.
(a) Blade containment
Single blade radial containment is a CS-E / CS-APU requirement. Full credit is given to engine certification for blade containment, and no specific certification activity is required at helicopter level for blade failure. This approach is supported by the in-service experience.
(b) Small debris containment at engine level
Some engine designs feature the capability to retain radially small debris, featuring, for instance, a reinforced casing or blade shedding capability.
The engine uncontained model features a small debris over a ±15° spread angle. Small fragments can be a collateral effect of either large or intermediate fragment release, but are released over larger spread angles, typically ±15°. Therefore, from a CS 29.903(d) point of view, no credit can be given to engine radial containment for small debris, which might however have other safety benefits.
(c) Rotor containment at engine or APU level
CS-APU has provisions to demonstrate rotor containment. For engines, while not required by CS-E, engine manufacturers might decide to design their engines featuring rotor containment systems, for all or specific rotating stages.
— For engines, the containment capability is not required by CS-E and the corresponding data is not covered by the engine type certificate; the helicopter manufacturer should propose a mechanism to ensure that the data is valid, under their DOA or by validation through the engine type certificate whereas for an APU, CS-ETSO requirements are in place, and it can be expected that the data is covered by the ETSO issuance.
— In-service experience has shown that such containment features successfully perform their intended purpose of retaining the biggest debris (large fragments). However, small debris can defeat the containment system, either by missing it or by exiting through damages caused by the large fragments. Rotor containment systems, as explained in paragraph f.(1) of AC 29.903C, still require some activity at helicopter level to ensure that the risks associated with uncontained engine or APU uncontained failure are adequately mitigated.
Note: For APUs, AMC 20.128A defines an acceptable model based upon debris exiting the containment system with a 1 % residual energy.
[Amdt No: 29/11]
EASA AMC1 29.903(d)(1) explains engine fragment containment credits: full credit for blade containment, no credit for small debris, and helicopter-level actions for rotor containment systems.
* Summary by Aviation.Bot - Always consult the original document for the most accurate information.
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