Damage-tolerant attachment system for an aircraft engine

1. An attachment system to attach a turboengine to a pylon of an aircraft, said turboengine comprising a fan casing, a compressor casing disposed adjacent to the fan casing, and a turbine casing disposed adjacent to the compressor casing, said attachment system comprising:

first attachment device attached to the pylon and the compressor casing of the turboengine;

second attachment device attached to the pylon and the turbine casing of the turboengine; and

a third backup attachment device comprising a first portion fixedly attached to the pylon and a second portion fixedly attached to the fan casing of the turboengine, wherein the first and second portions are configured relative to one another so as not to disrupt a predetermined isostatic attachment of the first and second attachment devices to the pylon,

wherein, in response to the first attachment device disengaging from the compressor casing or the pylon, or the second attachment device disengaging from the pylon and the turbine casing, the first portion and the second portion engage with each other, and

the third backup attachment is separated from the first attachment device and the second attachment device.

2. The attachment system as claimed in claim 1 , wherein said first and second portions of the third backup attachment device are connected to one another with clearance.

3. The attachment system as claimed in claim 2 , wherein said first and second portions of the third backup attachment device are connected to one another by at least one shaft fixedly attached to one of said portions and traversing with clearance an orifice made in the other portion.

4. The attachment system as claimed in claim 3 , wherein:

the at least one shaft comprises a plurality of shafts;

the first portion of said third backup attachment device comprises a cradle fixedly attached to said pylon; and

the second portion of said third backup attachment device comprises at least two lateral yokes fixedly attached to said turboengine, each of said yokes respectively supporting a corresponding one of the plurality of shafts in such a way as to provide clearance between each of the shafts and said cradle.

5. The attachment system as claimed in claim 4 , wherein the shafts of said yokes are parallel with one another and with a longitudinal shaft of said turboengine.

6. An aircraft comprising the attachment system of claim 1 .

7. An aircraft comprising two turboengines mounted at a rear of said aircraft, said turboengines being placed one beside the other having respective longitudinal axes which are parallel with a longitudinal axis of the aircraft, wherein each of said turboengines is attached to said aircraft by the attachment system of claim 1 .