Conventionally, a rotorcraft, and in particular a helicopter, has a fuselage provided with covers that are fastened to an adjacent structure by a locking device, each cover being suitable for being moved to provide an operator with access to internal members of the rotorcraft. In order to be opened, the covers may move in rotation about a fastener axis, or they move in translation. For example, an operator may have access to the engine compartment by causing a cover to slide.
Documents FR 1 591 218, FR 2 475 104, and FR 2 458 656 describe locking devices.
Document FR 2 458 656 discloses in particular a locking device having a latch arranged on the cover for fastening against an adjacent structure.
That latch is provided with a handle that is hinged about a fastener pin. A locking arm having a free end in the form of a rounded hook is connected to the handle by a pivot peg. When the handle and the locking arm are in a closed position, i.e. a flush position, the handle and the locking arm are connected by a tiltable release catch, the release catch being arranged on the handle and co-operating with a catch stud of the locking arm.
The locking device also includes a retaining pin disposed on the adjacent structure to which the cover is to be fastened.
In the closed position, the hook of the locking arm co-operates with a single transverse branch of the retaining pin.
When the operator seeks to open the cover, the operator causes the release catch to tilt, with the handle thus being released from the locking arm. The operator then tilts the handle, causing it to rotate about the fastener pin. This leads to rotary movement of the locking arm hook, which moves directly out from the retaining pin. The locking device is then in the open position and the operator can move the cover.
In a variant, the fastener pin is arranged inside an oblong hole in the handle, and a single compression link connects said fastener pin to the pivot peg.
Thus, if the release catch opens accidentally in flight, the handle turns through a minimum distance and does not lead to the hook separating from the single transverse branch of the retaining pin.
The presence of the oblong hole and of the compression link causes the pivot peg, the fastener pin, and the point of contact between the hook and the sole transverse branch of the retaining pin to be moved out of alignment. This results in jamming that prevents the locking device opening completely.
Reference may be made to the literature to obtain additional information about this safety feature.
Those locking devices are effective and have been in widespread use in the field of aviation for a long time.
Nevertheless, sliding covers often present large dimensions and they need to be fastened sufficiently securely so that they do not open under the effect of the aerodynamic forces to which they are subjected in flight. Under such circumstances, in order to be held in the closed position while in flight, sliding covers include not only latches, but also holding fingers, also known as “centering” fingers, that are arranged around the periphery of the sliding cover.
In a variant, the centering fingers may be secured to adjacent structures to which the cover needs to be fastened in flight, the cover then possessing means for receiving said centering fingers.
Unfortunately, manufacturing tolerances often give rise to high levels of friction between each centering finger and the corresponding reception means.
Under such circumstances, when the locking devices are opened, the operator has great difficulty in causing the cover to slide. Grip means have therefore been provided on covers to enable the operator to take hold thereof and open the cover. In spite of such grip means, it can be difficult to cause the cover to slide along the centering fingers.
It should be observed that the person skilled in the art of cold storage chambers is confronted with a door opening problem, since the door of a cold chamber tends to remain stuck to the door jamb.
To remedy that problem, a handle is known that is connected to the door via a hinge connection and that co-operates via a first end by interfering shapes with a section of the door jamb. In addition, the handle is extended by a pusher.
When the operator moves the handle, the handle turns about the connection zone with said door jamb section until the pusher comes into contact with the wall supporting the door jamb. This gives a considerable lever arm that enables the operator to unstick the door.
The first end is then disengaged from the door jamb and the operator can open the door without difficulty.
Nevertheless, although of interest, it will be understood that the technical field of doors for cold storage chambers is remote from the invention and cannot be easily adapted to covers, and in particular sliding covers. This observation is particularly true for an aircraft cover that requires a latch to be implemented that is flush, i.e. that does not project from the cover, for obvious aerodynamic reasons.