FIELD OF THE INVENTION
[0001] The present invention relates to a security locking device for assuring a correct
closure of the fan cowl doors of an aircraft power unit nacelle.
BACKGROUND OF THE INVENTION
[0002] An aircraft having a power unit supported in the airframe mounted configuration comprises
an engine and a nacelle structure housing said engine. The nacelle structure comprises
two displaceable parts called fan cowl doors or cowlings which can be opened on the
ground during maintenance operations to access the various items of the power unit,
the cowlings or fan cowl doors being closed and properly latched during operational
conditions of the aircraft, therefore providing aerodynamic continuity for the power
unit in flight.
[0003] The nacelle usually comprises fan cowl locking means fixing and latching the fan
cowl doors during operation of the aircraft.
[0004] The indication of fan cowl doors not being properly latched is not usually a signal
that is sent to the cockpit to avoid false open-door signals. For this reason, a visual
inspection of the nacelle is necessary to detect if fan cowl doors are not properly
latched.
[0005] Therefore, it is necessary to provide a warning signal with high visibility when
the fan cowl doors of an aircraft are not properly latched or locked. For this reason,
apart from the fan cowl locking means that fix and latch the fan cowl doors, an indication
device is also provided for indicating if these fan cowl locking means are not properly
latched. This indication device comprises a panel fixed by rotating means on one of
the two fan cowlings, the panel being closed on that one fan cowling by means of several
primary locking means by rotating on said rotating means, therefore covering at least
partially the fan cowl locking means of the fan cowl doors, such that all the fan
cowl locking means have to be properly latched for the panel being closed. If the
device is not closed, therefore being the fan cowl locking means not properly latched,
the panel hangs vertically from the fan cowl door, providing a high visibility warning
signal of the aircraft fan cowl doors not being properly latched or locked. This system
is known from document
EP 09784126.6, filed on 9 July, 2009.
[0006] However, sometimes the indication device (panel) is not properly latched by its primary
locking means along its length, due to pollution (paint or stickers) on the primary
locking means, therefore preventing a correct closure of said primary locking means,
or because the maintenance personnel operating these latches (primary locking means)
are not familiar with them, as these means are not easy to manipulate. Due to these
reasons, the indication device (panel) hangs vertically during flight, therefore being
blown or torn away in many occasions, as it is not properly latched. It is therefore
desirable to prevent the indication device from being lost.
[0007] It is known from document
US 4,531,769 a latch for securing together a pair of hinged cowlings of an aircraft engine, this
latch comprising a hook, a hook keeper and a safety lock, such that the safety lock
engages the hook in the hook keeper when the latch is in a closed position, engaging
the cowlings, and such that the safety lock engages the hook when the latch is in
an open position, the cowlings being disengaged. The problem of this known solution
is that it is difficult to manipulate and that, for the system to work properly, it
is necessary to have an equilibrated and balanced position of the hook keeper and
hook, occurring that sometimes, as the vibrations in these parts of the aircraft are
very high, it may occur that a misalignment happens with the consequent default in
the engaging of the latch, so the cowlings are not properly closed.
[0008] It is known from document
US 5,620,212 a hook latch mechanism for joining two members of an engine cowl, comprising a hook
latch mechanism on of the members to be joined and a keeper together with a mounting
bolt, carried in the second member engaged. This system has the problem of possible
misalignment between the bolt and the hook, therefore causing that the latch mechanism
is not properly secured. Besides, this mechanism can sometimes be not properly latched
due to pollution in the mechanism or due to the maintenance personnel not being familiar
with the operation of these systems.
[0009] The present invention is oriented to the solution of the above-mentioned drawbacks.
SUMMARY OF THE INVENTION
[0010] The present invention relates to a security locking device for assuring a correct
closure of the fan cowl doors of an aircraft power unit nacelle.
[0011] The fan cowl doors of the nacelle structure of an aircraft housing an engine are
closed when the aircraft is in flight by means of fan cowl locking means. Besides,
in order to have a visual indication of these fan cowl doors being properly latched,
an indication device, rotating over rotating means located in one of the two fan cowl
doors, is provided, such that this indication device comprises a panel fixed on one
of the two fan cowl doors by means of a primary locking device, such that, by rotating
the panel on the rotating means the panel is latched over the fan cowl doors, covering
at least partially the fan cowl locking means. According to the invention, a security
locking device is provided, providing security alternative latching for the cited
indication device.
[0012] The security locking device of the invention comprises security locking means providing
the security alternative latch of the indication device, as these security locking
means close automatically over the fan cowl locking means, without the need of further
operation on the part of the maintenance personnel. Therefore, the indication device
can be fixed by the primary locking device and also by security locking means such
that, even if the primary locking device does not properly latch the indication device
over the fan cowl doors, the security locking means assure that the indication device
is latched over the fan cowl doors, as the security locking means are latched without
the need of being operated.
[0013] The primary locking device fixes the panel of the indication device on one of the
fan cowl doors by rotating on the mentioned rotating means, such that the panel, once
it is closed, covers at least partially the fan cowl locking means of the fan cowl
doors. This primary locking device is designed having an equilibrated and aligned
engaged status, also being of easy and friendly manipulation for the maintenance personnel.
The security locking means give a further security latch for the indication device,
preventing the detachment of the panel in the indication device in the case in which
the primary locking device is not actuating properly, that is, in the case in which
the primary locking device is not properly latched on the fan cowl door.
[0014] Other features and advantages of the present invention will be disclosed in the following
detailed description of an illustrative embodiment of its object in relation to the
attached figures.
DESCRIPTION OF THE DRAWINGS
[0015]
Figures 1 a and 1b show the location of the fan cowl doors in a typical aircraft nacelle
configuration.
Figures 2a and 2b show schematically the location of the fan cowl locking means according
to the prior art in the fan cowl configuration of an aircraft.
Figure 3 shows an indication device, according to the known prior art, being latched
over the fan cowl doors by a primary locking device.
Figure 4 shows a perspective view from the inside of the fan cowl doors of the part
of the primary locking device located on the panel of the indication device, according
to the known prior art.
Figure 5 shows a perspective view from the inside of the fan cowl doors of the primary
locking device and the security locking means when the indication device is in a closed
position in an aircraft power unit nacelle according to the invention.
Figures 6a and 6b show perspective views of the inside of the fan cowl doors of the
part of the security locking means located on the panel of the indication device and
located on the fan cowl doors, respectively.
Figures 7a, 7b and 7c show different views of the part of the security locking means
located in the indication device, for the fan cowl doors of an aircraft power unit
nacelle according to the present invention.
Figures 8a and 8b show different views of the part of the security locking means located
in the fan cowl doors, for the fan cowl doors of an aircraft power unit nacelle according
to the present invention.
Figure 9 shows a plan view of the panel of an indication device according to the known
prior art.
Figure 10 shows a plan view of the panel of the indication device on which the security
locking device of the present invention is located, this panel being thicker than
the panel used in the prior art, as a primary locking device and a security locking
device are comprised in it..
Figure 11 shows a plan view of the fan cowl door over which a panel with an indication
device according to the known prior is engaged.
Figure 12 shows a plan view of the fan cowl door over which a panel with a security
locking device according to the invention is engaged.
Figures 13 shows a schematic view of the indication device comprising a primary locking
device and security locking means according to the invention, subjected to an air
flow in flight.
Figure 14a shows a schematic view of the indication device according to the prior
art closed by its primary locking device, in its nominal closed position.
Figure 14b shows a schematic view of the indication device according to the prior
art closed by a security locking device according to the present invention, in the
position in which the panel load is supported by said security locking device according
to the present invention.
Figure 14c shows a schematic view of the indication device according to the present
invention closed by the security locking device according to the present invention,
in the position in which the panel load is supported by said security locking device
according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0016] The present invention relates to a security locking device 100 for assuring a correct
closure of the fan cowl doors 10, 20 of an aircraft power unit nacelle.
[0017] According to the known prior art, as it can be seen in Figures 1a, 1b, 2a 2b and
3, the fan cowl doors 10, 20 are closed by means of fan cowl locking means 30. Besides,
in order to have a visual indication of these fan cowl doors 10, 20 being properly
latched, an indication device 40 is provided, such that this indication device 40
comprises a panel 41 fixed by rotating means 42 on one of the two fan cowl doors 10
or 20. According to the known art, the panel 41 is fixed on one of the fan cowl doors
10 or 20 by a primary locking device 101.
[0018] According to the invention, a security locking device 100 is provided, providing
security alternative latching for the correct latch of the cited indication device
40.The security locking device 100 of the invention comprises security locking means
102. The primary locking device 101 engages the panel 41 of the indication device
40 on one of the fan cowl doors 10 or 20 by rotating on the mentioned rotating means
42, such that the panel 41, once it is engaged by the primary locking device 101,
covers at least partially the fan cowl locking means 30. The primary locking device
101 is designed having an equilibrated and aligned engaged status, also being of easy
and friendly manipulation for the maintenance personnel. The security locking means
102 of the invention give a further security latch, preventing the detachment of the
panel 41 in the indication device 40 in the case in which primary locking device 101
is not properly latched on the fan cowl door 10 or 20.
[0019] The security locking means 102 of the invention act as a safety device, providing
a positive lock or latch of the panel 41 over the fan cowl door 10 or 20, at the tip
of the panel 41, when this panel 41 is slammed without any further operation or actuation.
Therefore, the security locking device 100of the invention avoids possible failures
in cases where the fan cowl locking means 30 or the primary locking device 101 are
not properly latched, as the security locking means 102 are latched automatically
as the panel 41 in the indication device 40 is closed, without the need of further
operation on the part of the maintenance personnel. The security locking means 102
comprise engaging means 50 located in the panel 41 engaging with receiving means 60
located in the fan cowl doors, 10 or 20 (see Figures 6a and 6b).
[0020] The primary locking device 101 will preferably have a design based on a pressure
relief latch design, comprising an opening 6, typically a slot, than can be operated
by means of a screwdriver, and adjusting means 7, typically a bolt, for setting the
grip of the panel 41, preferably varying from 7 mm up to 12 mm. The kinematics of
the primary locking device 101 is such that it ensures no contact in neither the opening
nor in the closing sequences of operation of the panel 41 in the worst case of tolerances.
[0021] In a embodiment of the invention, the engaging means 50 in the security locking means
102 comprise a hook 51 rotating around a pin 52 by support bushings 53 and a spring
55, located on a support 54 installed in the panel 41 (see Figures 7a, 7b and 7c).
This configuration allows a maximum mechanical rotation of the hook 51 that is calculated
so that it is limited in such a way that an extra rotation from the operation personnel
would not damage the engaging means 50. Typically, the maximum mechanical rotation
of the hook 51 is of about 30°. The value of the elastic constant K of the spring
55 and the hook 51 inertia are selected such that the resonance frequency has a different
value than the oscillation frequency of the engine, therefore avoiding coupling in
frequencies with the engine. Preferably, the value of the elastic constant K of the
spring 55 and the value of the hook 51 inertia are selected such that they avoid resonance
frequencies under about 60 Hz.
[0022] The receiving means 60 located in the fan cowl doors, 10 or 20, comprise a catching
element 61, preferably an axis or mounting bolt, over which the hook 51 engages, this
catching element 61 being fixed to a bracket 63 by bushings 62 (see Figures 8a and
8b).
[0023] According to the invention, the cut-out of the fan cowl door 10 or 20 over which
the panel 41 is engaged by means of the security locking device100, has to be increased
circumferentially in order to accommodate both the primary locking device 101 and
the security locking means 102 (see Figures 11 and 12), the surrounding parts in the
fan cowl being modified accordingly, and the attaching points for the lightning protection
being also consequently relocated.
[0024] As it can be seen in Figure 10, the panel 41 comprises a new cut-out 205 for accommodating
the security locking means 102. Furthermore, a new strip 200 is preferably provided,
apart from the strip parts 201 and 202 in the known prior art being redesigned consequently,
in such a way that the thickness of the panel 41 is locally increased, around the
area where the security locking device 100 is located, avoiding possible gaps between
the panel 41 and the fan cowl doors 10, 20, therefore avoiding that air enters through
these gaps, tearing off the panel 41.
[0025] The security locking device 100 in the indication device 40 according to the invention
is located next to the primary locking device 101 on the side of the panel 41 facing
incoming airflow 90 during flight of the aircraft. The reason for this is that this
security locking device 100 operates when the primary locking device 101 is not working
properly (that is, when the primary locking device 101 is not properly latched), so
that the security locking device 100 has to ensure that the airflow 90 which enters
the region between the fan cowl doors 10, 20 and the panel 41 of the indication device
40 is minimized. This is achieved by ensuring that there is no space between the panel
41 in its closed position and the fan cowl doors 10, 20 on the side facing the incoming
airflow 90.
[0026] Figure 14a, represents an indication device 40 with a panel 41 according to the known
prior art, the panel 41 being closed by a primary locking device 101: this Figure
shows the primary locking device 101 in its nominal closed position over the fan cowl
doors 10, 20. There is no space, as it can be seen in this Figure, between the panel
41 and the fan cowl doors 10, 20 on the side facing the airflow 90.
[0027] The security locking device 100 of the invention is therefore designed so that it
only supports the load of the panel 41 when the primary locking device 101 is not
properly latching the panel 41, so the panel 41 is either supported by the primary
locking device 101 or by the security locking means 102. As the security locking means
102 are a security measure, they are located in such a way that the hook 51 and the
catching element 61 only enter into contact when the panel 41 falls from its nominal
position (where it is latched to the fan cowl doors 10, 20 by the primary locking
device 101) to the position where it is supported by the secondary locking means 102.
This means that the closed position of the panel 41 of the indication device 40, when
this panel 41 is supported by the security locking means 102, juts out from the aerodynamic
surface of the fan cowl doors 10, 20 slightly, as represented in Figure 14b. To avoid
any flow of air from the airflow 90 from entering the space between the fan cowl doors
10, 20 and the panel 41, the panel 41 is thickened locally, around the area where
the security locking device 100 is located, as it is clearly represented in Figure
14c.
[0028] The security locking means 102 are preferably located, together with the primary
locking device 101, close to the edge of the indication device 40 (panel 41) facing
the airflow 90.The reason is that the incorrect closure of the primary locking device
101 is what causes the existence of a gap between the panel 41 and the fan cowl doors
10, 20 through which air from the airflow 90 makes the panel 41 and the indication
device 40 lift up and get lost in flight.
[0029] Modifications comprised within the scope defined by the following claims can be introduced
in the preferred embodiments which have just been described.
1. Security locking device(100) for an indication device (40), the indication device
(40) providing a warning signal when the fan cowl doors (10, 20) on an aircraft power
unit nacelle are not properly latched, the indication device (40) being latched to
the fan cowl doors by a primary locking device (101), characterized in that the security locking device (100)comprises security locking means (102) providing
a security alternative latch of the indication device (40) over the fan cowl doors
(10, 20), such that the security locking means (102) are latched only by closing the
indication device (40) over the fan cowl doors (10, 20), without the need of any further
operation.
2. Security locking device (100) according to claim 1, located close to the edge of the
indication device (40) facing an airflow (90).
3. Security locking device (100) according to any of claims 1-2, wherein the security
locking means (102) comprise engaging means (50) and receiving means (60), the engaging
means (50) being located in the indication device (40) and engaging with the receiving
means (60) located in the fan cowl doors (10, 20).
4. Security locking device (100) according to claim 3, wherein the engaging means (50)
comprise a hook (51) and a spring (55), such that the value of the elastic constant
(K) of the spring (55) and the value of the hook (51) inertia are selected such that
they avoid the resonance frequencies of the aircraft engine.
5. Security locking device (100) according to claim 4, wherein the value of the elastic
constant (K) of the spring (55) and the value of the hook (51) inertia are selected
such that they avoid resonance frequencies under 60 Hz.
6. Security locking device (100) according to any of claims 4-5, wherein the maximum
mechanical rotation of the hook (51) is calculated so that it is limited in such a
way that an extra rotation from the operation personnel would not damage the engaging
means (50).
7. Security locking device (100) according to claim 6, wherein the maximum rotation of
the hook (51) is of 30°.
8. Security locking device (100) according to any of the preceding claims, wherein the
indication device (40) comprises a panel (41) having increased thickness locally,
around the area where the security locking device (100) is located.
9. Security locking device (100) according to any of claims 3-8, wherein the receiving
means (60) comprise a catching element (61), over which the hook (51) engages, the
catching element (61) being an axis or a mounting bolt.
10. Security locking device (100) according to any of the preceding claims, designed in
such a way that it only supports the load of the indication device (40) in the case
in which the primary locking device (101) is not properly latching the indication
device (40).
11. Fan cowl doors for an aircraft power unit comprising a security locking device (100)
according to any of claims 1-10.
12. Aircraft comprising an indication device (40) providing a warning signal when the
fan cowl doors (10, 20) on the aircraft power unit nacelle are not properly latched,
such that it also comprises a security locking device (100) according to any of claims
1-10.
13. Aircraft according to claim 12, wherein the security locking device (100) comprises
a hook (51) and a spring (55), the elastic constant (K) of the spring (55) and the
inertia of the hook (51) being selected such that they avoid the resonance frequencies
of the aircraft engine.