Aeronautics and astronautics – Aircraft – heavier-than-air – Airplane and helicopter sustained
Reexamination Certificate
2003-02-27
2004-02-24
Barefoot, Galen L. (Department: 3644)
Aeronautics and astronautics
Aircraft, heavier-than-air
Airplane and helicopter sustained
C244S017110, C416S142000
Reexamination Certificate
active
06695253
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method and apparatus for folding/unfolding the blades of a rotary-wing aircraft rotor, such as a helicopter main rotor. More particularly but not exclusively, the invention relates to a method and apparatus which may be advantageously used to assist in manually folding the blades of a helicopter main rotor towards the rear, substantially along the fuselage and tail boom of the helicopter, in order to reduce the space required, during periods when it is out of service and/or in order to make it easier to stow in a hangar, especially on a ship, or to load and stow in the hold of a transport aircraft.
BACKGROUND TO THE INVENTION
In the flight configuration, rotary wing aircraft blades are connected to the rotor hub by connecting means which lock the blades in this unfolded position, in which their freedom of movement in a plane substantially perpendicular to the axis of rotation of the rotor, or the plane of the rotor disc, is very limited due to the stiffness of the means retaining the blades and hinging them to the hub being added to the stiffness of the blade drag dampers, in the case of hinged rotors, or due to the stiffness of the flexible torsion arms of the hub to which the blades are connected on rotors of the semi-rigid type.
To fold a blade, it is therefore necessary firstly to unlock it in order to allow it to have large-amplitude swing-type movement, generally towards the rear, and then to lock it in the folded position to avoid unwanted unfolding or deployment movements. To unfold or deploy a blade, i.e. to return it to the flight configuration, the sequence of operations mentioned above is carried out in reverse order, i.e. the blade in the folded position is unlocked to allow it to have large-amplitude swing-type movement, generally towards the front, and is then locked in the unfolded position or flight configuration.
These operations must be carried out in compliance with strict procedures, in order that the folding/unfolding of the blades is carried out without damaging the blades or other parts of the helicopter, and without danger to any personnel who may be present, such as operators assisting in the folding/unfolding manoeuvres.
Rotary-wing aircraft with folding/unfolding rotor blades and in particular such main rotors of helicopters, typically have at least two blades, each of which is connected to the rotor hub and locked in the unfolded position in the flight configuration by means connecting the blade to the hub comprising, as is generally the case on state-of-the-art rotors, a connecting device forming a pivot axis and at least one other device the movement of which causes the blade to be unlocked, allowing it to be folded by pivoting about said pivot axis, preferably towards the rear, substantially along the fuselage and the tail boom of the rotary-wing aircraft.
To fold the blades, two main types of folding procedures and devices are currently employed, namely manual folding, involving one or more operators, and automatic folding.
As illustrated in
FIG. 2
, which shows the folding of a blade of the four-bladed main rotor
2
of the helicopter
1
in
FIGS. 1
,
3
and
4
, by pivoting this blade relative to the hub
3
of the rotor
2
, it is frequently the case that the means connecting the blade to the hub comprise two pins such as
9
substantially parallel with each other, and symmetrical either side of a longitudinal axis X—X of the blade, to retain the blade root
8
in an outer radial yoke
11
of a substantially radial connecting device
10
, relative to the axis of rotation of the rotor, and generally termed a cuff, itself connected to the hub
3
of the rotor
2
by retaining and hinging means (not described or shown, as they do not form part of the invention). One of the two pins
9
is removable (it is shown withdrawn in
FIG. 2
) to allow the blade to fold by pivoting its root
8
about the other pin
9
which thus constitutes the pivot or folding axis, as also shown in
FIGS. 2 and 5
of U.S. Pat. No. 4,268,222 for respectively three-bladed and four-bladed rotors with star-shaped hubs with flexible arms.
Conventionally, manual folding takes place after preparation of the helicopter and its main rotor, this preparation consisting in chocking the helicopter by means of chocks and/or a parking brake, lining up the rotor to position the blades favourably, half of them being on the left and the other half on the right of the helicopter, substantially symmetrically relative to the longitudinal axis of the helicopter running from the rear forwards, (a blade being substantially aligned with the tail boom of the helicopter when the number of blades of the rotor is odd), locking the rotor in this position by means of a rotor brake or any other equivalent means, positioning the angle of attack of the blades at a fixed pitch value or within a certain pitch range and, where appropriate, locking the blades in pitch, so that the blades can be moved by pivoting without interference with each other or with other elements of the helicopter, then folding in succession all the blades of the rotor other than the one, if any, aligned with the tail boom, beginning on each side by folding the rearmost blade (when folding is towards the rear), and continuing on each side by folding the remaining blade, in the case of a rotor with four or five blades, or the rearmost of the remaining blades in the case of a rotor with at least six blades.
As is known and shown in
FIGS. 1
to
5
, for each of the blades
4
to
7
, and where the means connecting each blade
4
to
7
to the hub
3
comprise, as described above and shown in
FIG. 2
, two blade pins
9
, one of which is removable, the folding procedure consists, where folding is towards the rear, in
20
withdrawing the removable pin
9
situated furthest forward in order to unlock the blade
4
to
7
in its flight configuration, and in such a way that the blade
4
to
7
can pivot towards the rear about the one of the two pins
9
which is situated furthest to the rear, moving the blade
4
to
7
in rotation by means of a folding pole
12
equipped at its upper end with a hinged hook
13
to grip the blade close to its tip, and which is held and raised at its lower end by one or more operators
14
, in order to support the blade
4
to
7
, and counteract bending of the blade under the effect of its own weight, which tends to prevent the insertion or extraction of the removable pin
9
and, after rotation about the pivot pin
9
and when the blade has reached its folded position (as have the front left blade
4
and rear left blade
5
in
FIG. 1
) along the tail boom
15
of the helicopter
1
, securing it to the rear structure of the fuselage
16
or the tail boom
15
, and locking it in the folded position by means of this same folding pole
12
which is hooked on by the operator or operators
14
to supports
17
integrated in said structure (
16
-
15
), the folding pole
12
being held by straps
18
fastened to said structure (
16
-
15
).
Where appropriate, as described for example in U.S. Pat. No. 4,268,222, other tools to assist in folding may be used in addition to the folding poles, pole supports and straps, for example a support secured removably to the central parts of the hub, this support supporting the inner radial ends of rigid arms, the outer radial ends of which are connected removably to the upper end of the pivot pin of each blade or a service tool pin replacing said pivot pin, in order to limit the bending of the flexible arms of the star-shaped hub.
To facilitate the extraction and insertion of the removable blade pins, in order to facilitate the folding and unfolding of such blades, it is also known practice to use, as means of connecting the blade to the hub, expanding blade pins such as described in particular in patent U.S. Pat. No. 3,192,820, which are pins which in service run through bushes permanently installed in the blade roots and in the locked position have a diameter greater than their diameter in the unlocked position, due t
Cayol Marcel
Romani Michel
Barefoot Galen L.
Eurocopter
Sturm & Fix LLP
LandOfFree
Method and apparatus for folding/unfolding the blades of a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for folding/unfolding the blades of a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for folding/unfolding the blades of a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3335143