An assembly for a gas turbine engine, the assembly comprising: a spinner or nosecone comprising a threaded rear portion, an engine structure comprising a threaded front portion, the spinner or nosecone being threadingly connected to the engine structure, wherein rotation of the spinner or nosecone about the engine structure in a first direction secures the spinner or nosecone to the engine structure and rotation of the spinner or nosecone about the engine structure in a second direction releases the spinner or nosecone from the engine structure; and a lock ring slidingly connected to the engine structure to slide between: a forward position to engage the spinner or nosecone and block rotation of the spinner or nosecone in the second direction, and a rearward position, where the lock ring is spaced from the spinner or nosecone; wherein the rear portion of the spinner or nosecone includes a boss protruding rearwardly, and the lock ring includes a groove, and when the lock ring is in the forward position the groove receives the boss and blockingly engages the boss to prevent rotation of the spinner or nosecone in the second direction; wherein a biasing member biases the lock ring to the forward position to engage the spinner or nosecone; wherein the lock ring is slidable from the forward position towards the rearward position to disengage from the spinner or nosecone; and wherein the biasing member is a spring disposed between a rear portion of the lock ring and a second boss extending outwardly from the front portion of the engine structure, and a rearwardly extending portion of the lock ring, which is part of an outwardly facing surface of the lock ring, is configured to slide over the second boss of the fan hub to provide an aerodynamic seal. a spinner or nosecone comprising a threaded rear portion, an engine structure comprising a threaded front portion, the spinner or nosecone being threadingly connected to the engine structure, wherein rotation of the spinner or nosecone about the engine structure in a first direction secures the spinner or nosecone to the engine structure and rotation of the spinner or nosecone about the engine structure in a second direction releases the spinner or nosecone from the engine structure; and a lock ring slidingly connected to the engine structure to slide between: a forward position to engage the spinner or nosecone and block rotation of the spinner or nosecone in the second direction, and a rearward position, where the lock ring is spaced from the spinner or nosecone; wherein the rear portion of the spinner or nosecone includes a boss protruding rearwardly, and the lock ring includes a groove, and when the lock ring is in the forward position the groove receives the boss and blockingly engages the boss to prevent rotation of the spinner or nosecone in the second direction; wherein a biasing member biases the lock ring to the forward position to engage the spinner or nosecone; wherein the lock ring is slidable from the forward position towards the rearward position to disengage from the spinner or nosecone; and wherein the biasing member is a spring disposed between a rear portion of the lock ring and a second boss extending outwardly from the front portion of the engine structure, and a rearwardly extending portion of the lock ring, which is part of an outwardly facing surface of the lock ring, is configured to slide over the second boss of the fan hub to provide an aerodynamic seal. a forward position to engage the spinner or nosecone and block rotation of the spinner or nosecone in the second direction, and a rearward position, where the lock ring is spaced from the spinner or nosecone; wherein the rear portion of the spinner or nosecone includes a boss protruding rearwardly, and the lock ring includes a groove, and when the lock ring is in the forward position the groove receives the boss and blockingly engages the boss to prevent rotation of the spinner or nosecone in the second direction; wherein a biasing member biases the lock ring to the forward position to engage the spinner or nosecone; wherein the lock ring is slidable from the forward position towards the rearward position to disengage from the spinner or nosecone; and wherein the biasing member is a spring disposed between a rear portion of the lock ring and a second boss extending outwardly from the front portion of the engine structure, and a rearwardly extending portion of the lock ring, which is part of an outwardly facing surface of the lock ring, is configured to slide over the second boss of the fan hub to provide an aerodynamic seal.