GB2346593A - Airship bow thruster apparatus - Google Patents

Abstract

Airship bow thruster apparatus comprising means 9 for generating a large mass flow of air or exhaust gases and movable deflection means 17-20 at the bow of an airship positionable in the flow path of the air or exhaust gases. The position of the deflection means 17-20 is controlled by control means for controlling the direction that the air or exhaust gases is or are ejected at the bow of the airship. The invention also relates to an airship provided with such bow thruster apparatus. The airflow generating means 9, may comprise two fans (12,13 fig. 3), arranged one above the other, and driven by a.c. motors, or a gas turbine engine.

Description

Airship Bow Thruster Apparatus This invention relates to bow thruster apparatus for an airship and to an airship provided with such bow thruster apparatus.

It has always been accepted that a major aspect of airship operation which has prevented airships from being recognised as a useful and practical air vehicle is that of control at low airspeeds ; in particular during take-off and landing manoeuvres. The problem arises because there is a threshold below which the aerodynamic forces provided by fins and control surfaces of the airship are inadequate to provide control against the disturbing forces generated by atmospheric turbulence, particularly in low wind speeds. An airship can land much like a conventional aircraft, but as it slows to a halt, with its nose into the wind, it is at the mercy of any side gust or shift of wind direction.

Because of its essential aerodynamic shape, an airship hull of conventional form is always unstable in yaw at speeds below that at which the stabilising fins and controls are effective. In this condition, any side gust forces the nose of the airship out of alignment with the wind, presenting a large lateral surface area and causing the airship to "broach"and then be blown away downwind.

Historically the problem of controlling an airship during take-off and landing phases has been dealt with by providing handling lines, i. e so-called"bow lines, to enable ground handling parties to hold the nose into the wind during the critical phases. With large airships, e. g. the 244 m (800 foot) long R101, up to 500 men were used on the bow lines. During World War Two, the US Navy's extensive use of airships resulted in the development of tractors (mules) with winches to replace men on the bow lines. However a team of nine men was still involved and inadequate winch control still caused major problems.

Ground handling still remained the major cause of all airship accidents. The situation remained static until Roger Munk became involved in airship design in the late 1970s. His successful design for vectoring the thrust line of the propulsion engines eliminated accidents in the initial take-off and final landing phases. However up until the 1980s the mooring and unmooring phases still used manual bow line parties ; the expense of providing these remaining a threat to commercial viability.

Subsequent development work has suggested the use of a stern thruster (see GB-A-2,197,276) for controlling airships at low airspeeds. However stern thrusters have not proved to be successful in the airship mooring phase.

It has also been proposed in theory to provide an airship with a bow thruster, i. e. apparatus at the front of the airship able to generate thrust forces for controlling the airship during take-off and landing. However up until the present time no practical bow thruster system has been developed.

Bow thrusters are known in other vehicle applications. For example bow thrusters have been used on surface ships and in heavier-than-air vertical take-off and landing (VTOL) aircraft which use so-called"puffer jets", with air supplied from the lift engines, for short term yaw and lift correction. However the practical use of bow thrusters for augmenting control of airships at low airspeeds is not known.

It is an aim of the present invention to provide airship bow thruster apparatus for applying control forces at the exreme nose of an airship for use when the airship is operating below the threshold of effectiveness of its normal aerodynamics controls.

A further aim of the present invention is to eliminate the need for large ground handling parties hitherto essential in mooring and unmooring airships.

A still further aim of the present invention is to improve the low airspeed manoeuvrability of an airship allowing, for example, markedly increased hover accuracy.

According to one aspect of the present invention there is provided airship bow thruster apparatus comprising means for generating a large mass flow of air or exhaust gases, movable deflection means at the bow of an airship positionable in the flow path of said air or exhaust gases, and control means for controlling the position of thedeflection means for controlling the direction that the air or exhaust gases is or are ejected at the bow of the airship.

With such bow thruster apparatus the direction of the reactive force vector can be controlled allowing a pilot to apply corrective forces to steer the airship as required to counter atmospheric disturbances. In use the bow thruster should be capable of the very rapid application of lateral or braking forces at the nose of the hull.

Conveniently the gas mass flow generating means may comprise : a small gas turbine engine mounted in a structure adapted to be fixed to the nose of the airship hull ; electric fans mounted at the front of the airship ; or fans or other gas generators mounted elsewhere in the airship, with the gases ducted to the nose.

Suitably the movable deflection means comprises a socalled vane-box containing one or more vanes movable to deflect the ejected gases in the desired direction.

Typically the vane-box has sets of conventional cascade vanes, each set of vanes being pivotable or otherwise movable so as to deflect the gas stream in the desired direction. The gas stream is arranged to enter at the rear of the vane box in a forward direction along a path parallel to the longitudinal axis of the airship. Suitably, the vane sets can then be actuated to apply the following forces: NEUTRAL, i. e. no nett thrust with the engine fully spooled up for instantaneous efflux deflection.

-LATERAL, i. e. thrust applied by efflux deflection to the left or right.

-REVERSE, i. e. efflux directed forward to provide braking action.

Preferably the control means is operable to effect changes in the positions of the deflection means, i. e. to change between the fully operational state of any of thesemodes, in less than one second, preferably in no more than half a second.

According to another aspect of the present invention, there is provided an airship provided with a bow thruster apparatus according to said one aspect of the present invention.

Conveniently, the airship includes a pilot control unit to enable a pilot of the airship to remotely control operation of the bow thruster apparatus. The pilot control unit may comprise any of the conventional control means, such as switches, levers, control wheels etc. Since it is self evident that the most significant virtue of a bow thruster is in effecting yaw control, control operation is conveniently effected by foot operated pedals, as commonly found in heavier-than-air aircraft.

An embodiment of the invention will now be described, by way of example only, with particular reference to the accompanying drawings, in which : Figure 1 is a side elevation of an airship provided with bow thruster apparatus according to the present invention ; Figure 2 is a detail, on an enlarged scale, of the bow end of the airship illustrating the bow thruster apparatus; Figure 3 is a cut away view, on an enlarged scale, of the bow thruster apparatus shown in Figures 1 and 2; Figure 4 is a front view of the bow thruster apparatus shown in Figure 3; and Figure 5 is a schematic view illustrating the vane box of the bow thruster apparatus.

Figure 1 shows a non-rigid airship generally- designated 1 having an inflated gas-containing envelope 2 defining the hull 3 of the airship, a gondola 4 beneath the hull, control fins 5 at the stern of the airship, and a mooring adapter 30 with mooring rope 6 at the bow of the airship. A bow thruster assembly, generally designated 7, is also positioned at the bow of the airship and is shown in more detail in Figures 2 to 5.

The bow thruster assembly 7 comprises a mounting structure 8 for mounting the assembly to the front end of the hull 3, a gas mass flow generating means, generally designated 9, a vane box assembly 10, and control means for actuating the vane box assembly.

The gas flow generating means 9 comprises two fans 12 and 13 arranged one above the other and driven by a. c. motors 14 and 15, respectively, for ejecting air at high speed forwardly to the vane box assembly 10.

The vane box assembly 10 comprises two vane box units 10a and 10b positioned one above the other for receiving air ejected from the fans 12 and 13, respectively. The valve box unit 10a and its principle of operation will only be described in detail herein although it will be appreciated that the vane box 10b is constructed and operates in a similar manner. The vane box unit 10a is shown more clearly in Figure 5 and is mounted directly in front of the fan 12 which has shaped side walls 12a and 12b and a central deflector 12c defining air flow passages 15 and 16. The vane box unit 10a has two movably mounted vanes 17 and 18 on the left side of the unit and two similarly mounted vanes 19 and 20 on the right side of the unit. These vanes 17-20 are depicted schematically in Figure 5. Each of the vanes 17 and 19 is pivotally movable between first, second and third positions. In Figure 5, vane 19 is in its third position and vane 17 is shown in its first position (in dashed lines) and its second position (in full lines). Vanes 18 and 20 are each movable between first and second positions, with vane 18 being shown in its first position and vane 20 beingshown in its second position.

The positions of the vanes 17-20 are controlled by control means operated by the pilot. The control means includes pneumatic actuating means for moving the vanes 1720 into and out of their various control positions and transmission means for transmitting pilot command signals from the pilot cabin to the actuating means. The transmission means must, for safety reasons, be protected against disruption caused by internal and external electromagnetic radiation fields. In this respect it will be appreciated that the hull envelope 2 is suitably transparent to radiated energy (e. g. radar or radio transmissions) and to radiated energy from natural phenomena, such as a lightning strike etc. The transmission means may comprise electric wires and cables. However wires and cables have to be meticuously shielded ; a problem exacerbated by the fact that the conductors and the shielding themselves provide targets for a lightning strike. Other possible transmission means comprise fluid amplifiers, electro optic (infra-red) means and telemetry means. However these transmission means are subject to disruption in certain circumstances. The transmission means may also be mechanical, e. g. manually operated cables and levers. The presently preferred control means, which offers good protection against disruption, uses fibre optics as signal transmission means and pneumatically operated actuating means for the vanes.

Fibre-optic signal transmission, colloquially known as"fly-by-light", is implemented as follows. Control signals from the pilot are initially transformed to electrical signals by potentiometer type circuits, switches, levers, pedals or the like which can be effectively shielded from EMI effects by enclosures within the control cabin of the airship. Within these same enclosures the electrical signals are encoded intolight pulse signals and passed, conveniently in multiplexed format, to the bow thruster assembly by fibre-optic cables (not shown). In a similarlyshielded enclosure withinthe bow thruster assembly 7, the light pulses are decoded and transformed into electrical signals at an interface unit 29 and these electrical signals operate electro-pneumatic selectors 11 which apply pneumatic force to their specific actuators. Pneumatic power is transmitted to the vanes 17-20 of the vane box assembly via non-metallic tubing, thus achieving the required immunity to EMI effects.

The provision of two fans 12, 13 and two vane box units 10,10b is for duplication purposes in case of malfunctioning. The fans are intended to operate together but, in the event of failure of one fan or vane box unit, the other fan or vane box is able to operate effectively by itself.

Since usual airships practice is for the pilot to operate the aerodynamic control input devices by hand controls only, rudder foot pedals are convenient for controlling the bow thruster apparatus and have the advantage of instinctivesense for operating and controlling the bow thruster assembly. A switch is provided at the pilot position for each of the duplicated gas mass flow generating means, with indicator lamps to indicate correct function of each unit.

In use, the bow thruster assembly 7 can be operated as follows: (1) To provide a"NEUTRAL"position where zero nett force is applied to the airship. In this case the vanes (or vane sets) of the vertically disposed vane box units 10a, 10b are actuated so as to divide the gas stream and deflect it to exit the vane box assembly to the right and left in equal mass flow quantities.

In particular, for each vane box unit, the vanes 17 and 19 are set to their second positions and vanes 18 and 20 are set to their secoind positions.

(2) To provide a"BRARING"position for use in checking forward motion of the airship as it approaches a mooring mast. In this case the vanes of both vertical vane box units are actuated so as to retract them out of the gas stream, which is then allowed to exit in a forward direction, so providing a sternwards reactive force. The vanes 17 and 19 are set to their third positions and the vanes 18 and 20 are set to their second positions.

(3) To provide"left"or"right"steering forces, both vane boxes are actuated as follows. To provide a left steering force, for each vane box unit the vane 19 is set to move forward into its first position and to contact the retracted vane 17 in its third position. Vane 18 is in its 2nd position and vane 20 is in its first position. With the vanes 17-20 so set, the whole gas stream is deflected so that it can only exit toward the right. The shaping of the vanes 17-20 is arranged so that a reactive force to the left is produced, at a right angle to the airship longitudinal axis. For a right steering force the reverse position of the vertical vane sets is assumed.

(4) In (1), (2) and (3) above only horizontal steering force vectors are generated. When deemed that an airship requires corrective steering actions to deflect the nose in a vertical sense, such as may occur with a single main wheel airship, supplementary vane sets are placed external to the vane box units to deflect the gas effluxes in the vertical plane in all the modes described above.

In normal use, with the required gas flow then available, the system with no pilot input is biased to the "NEUTRAL"position by spring type devices (not shown) which centralise the rudder pedals.

Left or right steering inputs are made by the pilot by longitudinal deflection of the left or right pedals. The deflection operates an electrical potentiometer and thus generates the command signal.

Reverse thrust or"Braking"pilot commands are input by depressing the toe section of the foot pedals ; the action operates a switch which generates the command signal. This method is familiar to most aircraft pilots.

In use the bow thruster assembly gives an airship effective control in flight at airspeeds below the aerodynamic control threshold. The pilot is able to land, taxi and moor the airship entirely without manual external intervention, although, for safety reasons, a safety controller may be needed. Thus the airship has parity with a commercial airliner docking at its terminal.

The bow thruster described allows the airship pilot direct control of the airship, so that he can, without recourse to external assistance, complete a landing, taxi to the vicinity of a mooring mast (not shown) and engage the airship's mooring adapter 30 (see Figures 1 and 2) into a mooring receptacle on the mooring mast.

Virtually all airships are moored to their mooring mast by means of a the mooring adapter 30 at the extreme nose of the ship. This structure distributes mooring loads into the airships hull and has a strong extension at its centre known as the"nose probe"31. The nose probe 31 is designed to engage into a socket type receptacle on a swivelling head of the mooring mast, where it is locked automatically by spring pawls. Engagement of the nose probe in its socket calls for highly accurate control of the airship's nose, which is out of sight of the pilot. In order to provide the pilot with a visual close-up display to enable probe engagement, a miniature video camera is mounted closely adjacent to, but slightly offset from, the noseprobe 30. A target board is mounted at the mooring mast head, with the target centre offset by an equivalent distance to the probe/camera offset. The video picture is displayed to the pilot, who then controls the bow thruster forces to align the probe with its socket.

Claims (10)

1. Airship bow thruster apparatus comprising means for generating a large mass flow of air or exhaust gases, movable deflection means at the bow of an airship positionable in the flow path of said air or exhaust gases, and control means for controlling the position of the deflection means for controlling the direction that the air or exhaust gases is or are ejected at the bow of theairship.

2. Airship bow thruster apparatus according to claim 1, in which the gas mass flow generating means comprises a gas turbine engine mounted in a structure adapted to be fixed to the nose of the airship hull.

3. Airship bow thruster apparatus according to claim 1, in which the gas mass flow generating means comprises electric fans arranged to be mounted at the front of the airship.

4. Airship bow thruster apparatus according to claim 1, in which the gas mass flow generating means comprises fans or other gas generators for mounting at a position spaced from the front of the airship and ducting means for ducting gases generated by said fans or other gas generators to the nose of the airship.

5. Airship bow thruster apparatus according to any one of the preceding claims, in which the movable deflection means comprises a vane-box containing one or more vanes movable to deflect the ejected gases in the desired direction.

6. Airship bow thruster apparatus according to claim 5, in which the vane-box has sets of cascade vanes, each set of vanes being pivotable or otherwise movable so as to deflect the gas stream in the desired direction.

7. Airship bow thruster apparatus constructed and arranged substantially as herein described with reference to, and as illustrated in, the accompanying drawings.

8. An airship provided with a bow thruster apparatus as claimed in any one of the preceding claims.

9. An airship according to claim 8, including a pilot control unit to enable a pilot of the airship to remotely control operation of the bow thruster apparatus.

10. An airship according to claim 9, in which the pilot control unit includes control devices, such as switches, levers, control wheels or the like.