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Showing papers on "Blade pitch published in 1975"


W. Johnson1
01 Jul 1975
TL;DR: In this paper, a model for predicting the tilting proprotor aircraft dynamics is presented, where the influence of coupled flap/lag bending modes and rotor blade torsion degrees of freedom on proprotors is investigated.
Abstract: Proprotor and cantilever wing aeroelastic behavior is applied to a gimballed rotor and a hingeless rotor to develop an analytical model for prediction of tilting proprotor aircraft dynamics. Particular attention is given to: the influence of coupled flap/lag bending modes; the influence of rotor blade torsion degrees of freedom on proprotor dynamics; and, to a constant coefficient approximation representing the dynamics in nonaxial flow through the rotor. The following are also examined: the number of blade bending and torsion modes required; the influence of the rotor aerodynamic model; the influence of the blade trim bending deflection; the importance of the rotor rotational speed degree of freedom; and the effect of the wing aerodynamic forces. The origin of the significant influence of the blade pitch motion on the proprotor dynamics is discussed.

55 citations


Patent
31 Dec 1975
TL;DR: In this paper, a multiblade, wind-driven, variable pitch propeller is supported on a tower for rotation by wind forces and is connected through gears to drive an electrical generator or the like to produce electrical energy.
Abstract: A multiblade, wind-driven, variable pitch propeller is supported on a tower for rotation by wind forces and is connected through gears to drive an electrical generator or the like to produce electrical energy. The gears include a ring and pinion arranged in a gear case so that wind forces acting on the propeller and torque forces produced in the gears are balanced, thus avoiding swinging movement of the propeller about the tower axis due to unbalanced forces and thereby keeping the propeller axis pointed into the wind. The pinion gear is engaged with the ring gear at a location spaced near the top of the ring gear and a pinion shaft sleeve is disposed around the pinion shaft and sealed to a bottom portion of the gear case to effect a gear lubricant seal therewith, thus eliminating the requirement for an oil seal between the pinion shaft and gear case, with concomitant elimination of the oil seal drag, and also eliminating friction drag of the gear lubricant itself on the pinion shaft. Further, the danger of damage to the components in the event of loss of gear lubricant from the gear case is avoided by provision of the pinion shaft sleeve.

45 citations


Patent
01 Jul 1975
TL;DR: A controllable pitch marine propeller has blades carried by a hub and a hydraulic actuator coupled to the blades for altering the pitch angle of the blades in both directions, astern and ahead, and also beyond the ahead position to a feathered position as mentioned in this paper.
Abstract: A controllable pitch marine propeller has blades carried by a hub and a hydraulic actuator housed in the hub and coupled to the blades for altering the pitch angle of the blades in both directions, astern and ahead, and also beyond the ahead position to a feathered position. A servo-control system controls the actuator to adjust the blade pitch angle, the control system having a blade position feedback loop by which the system operates with positional feedback over the range of pitch angle between astern and full ahead pitch angles. However, the demand signal for blade feathering renders the feedback loop inoperative, and the hydraulic actuator then moves the blades into the feathering position without feedback action.

31 citations


Patent
13 Nov 1975
TL;DR: In this article, a control for a helicopter having dual, coaxial, counterrotating rigid rotors which varies the cyclic control phase angle of each rotor in flight as a function of vehicle forward speed is presented.
Abstract: A control for a helicopter having dual, coaxial, counterrotating rigid rotors which varies the cyclic control phase angle of each rotor in flight as a function of vehicle forward speed to thereby control the coupling of lateral cyclic pitch with longitudinal cyclic pitch so as to introduce differential cyclic pitch inputs which automatically produce aerodynamic moments in each rotor to minimize maneuver generated gyroscopic precession moments, which also produce optimum lateral lift vector displacement for all flight speeds.

28 citations


Patent
04 Sep 1975
TL;DR: In this article, the pitch-adjustment of a rotor blade is performed by an actuator urgeable by biassing means in one direction for adjusting pitch in one sense and subjectable to fluid pressure for movement in the opposite direction, against the action of the biassing-means in the other sense.
Abstract: Control means, for effecting the pitch-adjustment of a rotor blade, includes an actuator urgeable by biassing means in one direction for adjusting pitch in one sense and being subjectable to fluid pressure for movement in the opposite direction, against the action of the biassing means, for adjusting pitch in the other sense. Stop means is provided which is also subjectable to said fluid pressure, being maintained in an inoperative position when the pressure is above a predetermined value and being movable into an operative position when the pressure falls below that predetermined value. Abutment means is engageable by the stop means, when in its operative position, to arrest movement of the actuator at a predetermined position when moving in said one direction.

27 citations


Patent
17 Nov 1975
TL;DR: In this article, a mechanism for stopping or feathering the tail rotor when driving the propulsion propeller or for stopping the propeller when the rotor is in operation is presented. But the mechanism is not suitable for the case of a single rotor and a small wing.
Abstract: Compound helicopters, those having a rotor blade and a small wing, possess rear propulsion propeller adjacent to the tail rotor. The tail gearbox is driven through a drive train coupled to the main rotor drive shaft. In such aircraft the tail rotor is in operation when the propulsion propeller is turning, and vice versa. A mechanism is provided herein for stopping or feathering the tail rotor when driving the propulsion propeller, or for stopping the propulsion propeller when the tail rotor is in operation.

24 citations


Patent
29 May 1975
TL;DR: In this paper, a variable pitch blade and blade mount was proposed for composite fan blades and blade mounting arrangements where the blades are permitted to pivot relative to a turbine hub about an axis generally parallel to the centerline of the engine upon impact of a large foreign object, such as a bird.
Abstract: A variable pitch blade and blade mount which is suitable for propellers, fans and the like and which has improved impact resistance. The invention is particularly directed to composite fan blades and blade mounting arrangements wherein the blades are permitted to pivot relative to a turbine hub about an axis generally parallel to the centerline of the engine upon impact of a large foreign object, such as a bird. By thus providing for the pivoting of the blades upon impact, centrifugal force recovery becomes the principal energy absorbing mechanism and a blade having improved impact strength is obtained.

22 citations


Patent
Bodlaj Viktor Dr1
03 Oct 1975
TL;DR: In this paper, a method and apparatus for measuring the height of a blade of a turbine rotor as the rotor is being rotated characterized by deflecting a laser beam at a given deflection frequency across the path of the moving blade, sensing the reflected portion to produce a reflected signal, synchronizing the speed of rotation of the rotor with the frequency of deflection so that the end of the blade and the deflected beam reach the same point simultaneously and applying the reflected laser signal and a reference signal from the laser beam to an electronic analysis system to determine the individual blade.
Abstract: A method and apparatus for measuring the height of a blade of a turbine rotor as the rotor is being rotated characterized by deflecting a laser beam at a given deflection frequency across the path of the moving blade so that a portion of the deflected beam will be reflected by the end of the blade, sensing the reflected portion to produce a reflected signal, synchronizing the speed of rotation of the rotor with the frequency of deflection so that the end of the blade and the deflected beam reach the same point simultaneously and applying the reflected laser signal and a reference signal from the laser beam to an electronic analysis system to determine the height of the individual blade. Preferably, the synchronizing is accomplished by sensing the blade frequency, converting it to a converted blade frequency, comparing the converted blade frequency with the frequency of deflection to obtain an error signal and using the error signal to control the speed of rotation of the rotor. By including a counter circuit in the electronic analysis circuit and by sensing a mark on the rotor during each rotation of the rotor, adjustments can be made to either determine the height of each blade in a stage of blades during one revolution or to determine the height of a single individual blade of the stage.

20 citations


Patent
15 Jan 1975
TL;DR: In this paper, a windmill blade that has a rigid leading edge, a rigid root portion and a movable blade tip is used to reduce wind drags upon the blade.
Abstract: A windmill blade that has a rigid leading edge, a rigid root portion and a movable blade tip. Control of the geometric twist of the windmill blade is accomplished through proper selection of the axis of rotation for the movable blade tip and by controlling the position of the windmill blade tip with a servo motor or by controlling the position of the windmill blade tip with a spring and a weight. The ability to vary the geometric twist of the blade enables the frequency of rotation of the blade to be controlled to reduce wind drags upon the blade. This improved windmill blade eliminates the need for current complicated and expensive rotor hubs which are used to vary the blade pitch angle at the root end of the blade to reduce wind drag upon the blade. Processes related to the windmill blade are also presented.

19 citations


Patent
10 Jan 1975
TL;DR: In this paper, a fully articulated helicopter rotor has an elastomeric type main bearing which is reactive of all blade motions about the intersecting blade pitch change, lead-lag, and coning axes, including blade droop supporting and limiting members for static and dynamic operating conditions.
Abstract: A fully articulated helicopter rotor having an elastomeric type main bearing which is reactive of all blade motions about the intersecting blade pitch change, lead-lag, and coning axes, including blade droop supporting and limiting members for static and dynamic operating conditions wherein coupling influences between the separate blade motions are precluded. In reacting these blade weight loadings and dynamic thrust forces, the droop members specifically provide full area contact bearing surfaces to distribute the large forces from the blades into the rotor hub proper while avoiding scuffing or rolling contact between the parts, and the high bearing stresses which would result from either point or line contact only.

18 citations


Patent
04 Nov 1975
TL;DR: A self-adjusting propeller for sailing-boats comprises a propeller body mounted on a drivable rotary shaft and propeller blades rotatably mounted on the propeller bodies as mentioned in this paper.
Abstract: A self-adjusting propeller for sailing-boats comprises a propeller body mounted on a drivable rotary shaft and propeller blades rotatably mounted on the propeller body. These propeller blades are arranged, on movement of the boat in the water when the propeller is stationary, to assume a neutral position, while when the shaft is driven, they assume positions of rotation determined by stopping abutments for driving with the propeller. Each propeller blade is in this case so designed that the position line for the center of pressure along the propeller blade forms an arc from the shaft, the arc cutting the axis of rotation of the propeller blade a distance from the tip of the blade such that when the shaft is driven, the outer portion of the propeller blade provides a moment which counteracts the directed moment when the propeller is stationary.

Patent
04 Aug 1975
TL;DR: In this article, a trim system is selectively actuatable to provide an input to the auxiliary valve which tends to maintain the collective pitch control in a selected position, in a direction tending to drive the control to lower collective pitch (lower blade loading).
Abstract: In a helicopter, a pilot-actuated lever controls, through linkage mechanisms, a servo valve to drive a hydraulic piston; the piston moves a swash plate which in turn controls movement of rotor blade pitch positioning mechanisms against the force of blade loading, caused by aerodynamic forces. Blade loading, heretofore monitored visually by the pilot on a cruise guide indicator instrument, is used herein to control a secondary input to the servo valve, thereby to alter the position linkage mechanism which causes the force of a spring attached thereto to impose a force on the collective pitch control for blade loadings in excess of one-third of maximum allowable blade loads, in a direction tending to drive the control to lower collective pitch (lower blade loading). This provides "feel" to the pilot in proportion to blade loading when at critical magnitudes. A trim system is selectively actuatable to provide an input to the auxiliary valve which tends to maintain the collective pitch control in a selected position.

Patent
31 Jul 1975
TL;DR: In this article, a small drivable propeller is mounted for swivelling in a horizontal plane and is preferably positioned in fore-and-aft alignment with at least one main propeller and slightly above same.
Abstract: Propeller arrangement for marine vessels. A small supplemental and independently drivable propeller is mounted for swivelling in a horizontal plane and is preferably positioned in fore-and-aft alignment with at least one main propeller and slightly above same. Preferably the supplemental propeller is positioned ahead of such main propeller a distance equal to at least three-quarters of the diameter of the blade tip circle of the supplemental propeller. The blade tip circle of the supplemental propeller, when projected onto a common transverse plane may lie wholly within the correspondingly projected blade tip circle of the main propeller or it may extend partially out therefrom. The arrangement is adaptable to a variety of specific propeller arrangements including offsetting or angularly positioning the thrust line of the main propeller to counteract the turning moment of propeller torque and is further adaptable for use with single or multiple screw vessels. The supplemental propeller is adaptable primarily for harbor maneuvering and is of design appropriate to low speed operation as distinguished from the higher speed operation of the main propeller. In addition the supplemental propeller can increase the mean operation speed.

Patent
28 Jul 1975
TL;DR: In this paper, a rotor hub for a rotary wing aircraft in which elastomeric bearing means are utilized to transmit centrifugal loads and blade pitch, pitch, flap and lead lag movements, and in which the blades are foldable about a pivot located outboard of the bearing means between extended and folded positions.
Abstract: This invention provides a rotor hub for a rotary wing aircraft in which elastomeric bearing means are utilized to transmit centrifugal loads and blade pitch, flap and lead lag movements, and in which the blades are foldable about a pivot located outboard of the elastomeric bearing means between extended and folded positions. Locking means are provided to ensure that no deflection of the elastomeric bearing means occurs during the folding operation.

01 Oct 1975
TL;DR: In this paper, a modified form of the Prandtl wing theory with a realistic representation of the propeller slipstream distribution is presented for calculating the spanwise lift distribution on straight-wing/propeller combinations.
Abstract: A method is presented for calculating the spanwise lift distribution on straight-wing/propeller combinations. The method combines a modified form of the Prandtl wing theory with a realistic representation of the propeller slipstream distribution. The slipstream analysis permits calculations of the nonuniform axial and rotational slipstream velocity field of propeller/nacelle combinations. This nonuniform field was then used to calculate the wing lift distribution by means of the modified Prandtl wing theory. The theory was developed for any number of nonoverlapping propellers, on a wing with partial or full-span flaps, and is applicable throughout an aspect ratio range from 2.0 and higher. A computer program was used to calculate slipstream characteristics and wing span load distributions for a number of configurations for which experimental data are available, and favorable comparisons are demonstrated between the theoretical predictions and the existing data.

Patent
25 Nov 1975
TL;DR: In this article, a vee bottom boat with one or two inboard engines with the drive shafts thereof extending through the hull to position a propeller in a position such that when the boat is planing at cruising speed the propeller will be surface running or operating in half-submerged condition.
Abstract: A vee bottom boat having one or two inboard engines with the drive shafts thereof extending through the hull to position a propeller in a position such that when the boat is planing at cruising speed the propeller will be surface-running or operating in half-submerged condition. A rudder is located directly in rear of the propeller. A partly cylindrical splash guard is provided over the propeller and prevents "rooster-tailing." In addition, a water supply duct having a radius approximating that of the propeller is provided extending forwardly a short distance from the propeller. A transmission connecting the engine to a propeller shaft includes a chain which permits advantageous location of the propeller shaft relative to the engine and its output shaft.

Patent
13 Nov 1975
TL;DR: An analog mixer for a helicopter rotor control system mounted for tilting motion about a variable tilt axis and connected to the rotor control swashplate to cause synchronous tilting and including means to impart tilt generating control inputs to the analog mixer was presented in this paper.
Abstract: An analog mixer for a helicopter rotor control system mounted for tilting motion about a variable tilt axis and connected to the rotor control swashplate to cause synchronous tilting and including means to impart tilt generating control inputs to the analog mixer, and means to vary the position of the analog mixer tilt axis as a function of helicopter speed to thereby vary the phase angle of the helicopter rotor without imparting control inputs to the rotor control swashplate.

Patent
27 Aug 1975
TL;DR: In this paper, a variable pitch impeller is mounted around a pivot axis and a small control surface attached to the blade provides a turning moment around the pivot axis to oppose a similar moment provided by the lift component of the blade.
Abstract: A system is provided to adjust the operating angle of attack of a variable pitch impeller blade in response to different conditions. The impeller blade is pivotally mounted around a pivot axis and a small control surface attached to the blade provides a turning moment around the pivot axis to oppose a similar moment provided by the lift component of the blade. The operating angle of attack of the blade is determined by the angle at which the moment from the control surface tapers off as it approaches stall range, thus equalizing the moment from the impeller blade.

Patent
10 Jun 1975
TL;DR: In this paper, a helicopter rotor control mechanism is provided in which cyclic and collive rotor control functions are performed by a single control wheel having three degrees of freedom and operable by either or both hands of the pilot as desired.
Abstract: A helicopter rotor control mechanism is provided in which cyclic and collive rotor control functions are performed by a single control wheel having three degrees of freedom and operable by either or both hands of the pilot as desired. The control wheel is rotatable and translatable on one axis and tiltable about another to perform lateral, collective and pitch controls, respectively, through non-interacting linkages driving conventional collective control, lateral control and pitch control push rods connected to a conventional rotor control head of the swash plate type.

Journal ArticleDOI
TL;DR: In this paper, it is proposed to describe a cavitating ship propeller as a source of sound in terms of the source strength of a monopole which is situated near the position of a propeller blade tip.
Abstract: The paper considers the problem of propeller noise aboard ships. It is proposed to describe a cavitating ship propeller as a source of sound in terms of the source strength of a monopole which is situated near the position of a propeller blade tip. A new method for the measurement of this source strength is presented. The method is based on the application of the reciprocity principle. The source description and the measurement method can also be applied in relation to the problem of propeller induced vibrations. The first experiences with the method are very promising.

01 Aug 1975
TL;DR: In this paper, the first known highly skewed propeller installed on a U.S. merchant ship is presented, which is the culmination of a research program sponsored by the United States Maritime Administration.
Abstract: The design procedure, design decisions, final geometric configuration, model experimental results, and full-scale trial results of the first known highly skewed propeller installed on a U.S. Merchant Ship are presented. This paper is the culmination of a research program sponsored by the U.S. Maritime Administration to evaluate the feasibility of highly skewed propellers as a means to minimize ship vibration problems on high-powered merchant ships. The ships selected for this investigation were the two San Clemente Ore/Bulk/Oil Carriers built by National Steel and Shipbuilding Company for the Aries Marine Shipping Company. One ship was equipped with a conventional propeller and the second ship was fitted with the highly skewed propeller. Both propellers were designed specifically for these ships. Comparative performance evaluations of the conventional and highly skewed propeller are documented and analyzed. The primary advantages demonstrated by the highly skewed propeller are a reduction in unsteady propeller thrust by a factor of 2.6, a reduction in unsteady pressure forces by a factor of 4, and a reduction in vibration levels by a factor of from 1 to 4. These advantages are shown to be achieved without an adverse effect on the ahead and backing performance. The main conclusion is that highly skewed propellers are both technically and economically feasible from the standpoint of available design capability and assurance in realizing the advantages, and should be considered for future ship designs.

01 Jan 1975
TL;DR: In this article, a method for obtaining and analyzing the instantaneous velocities of helicopter rotor flow fields through use of a laser velocimeter capable of simultaneously sensing two components of velocity is described.
Abstract: A method for obtaining and analyzing the instantaneous velocities of helicopter rotor flow fields through use of a laser velocimeter capable of simultaneously sensing two components of velocity is described. Rotor blade aerodynamic loads may be computed from the velocity distributions near the blades. The experiment was conducted with a 2.13 m (7 ft) diameter model helicopter rotor operating in a wind tunnel. Velocity distributions are presented which document the flow field near the advancing blade. Circulation is calculated from the velocity measurements, and the radial distribution of circulation is discussed. The influence of the tip vortex from the preceding blade is apparent in this distribution. Tip vortex rollup on the advancing blade was documented by making a series of measurements at various distances behind the blade. Effects of blade drag are evident in the velocities behind the blade trailing edge.

Patent
10 Feb 1975
TL;DR: In this article, a rotor pitch control mechanism for use with bearingless helicopter rotors is presented. But the pitch-flap coupling and blade flap restraint are not included in this paper.
Abstract: A rotor pitch control mechanism for use with bearingless helicopter rotors is disclosed. The disclosed mechanism eliminates the requirement for vertical motion of the pitch link, thus alleviates the bearingless rotor problem of flapwise motion of the rotor blade in response to pitch control actuator forces. Stabilizing pitch-flap coupling and blade flap restraint is provided.

Patent
30 Oct 1975
TL;DR: The rotational speed of a screw propeller mounted on a propeller shaft of a ship is correctively increased or decreased by locally heating the back or face side of each blade of the propeller along a plurality of paths substantially parallel to and inward from the trailing edge of the blade in a region from a radial position about of 0.5 R to the blade tip, where R is the tip radius as discussed by the authors.
Abstract: The rotational speed of a screw propeller mounted on a propeller shaft of a ship is correctively increased or decreased by locally heating the back or face side of each blade of the propeller along a plurality of paths substantially parallel to and inward from the trailing edge of the blade in a region from a radial position about of 0.5 R to the blade tip, where R is the tip radius, particularly from 0.6 to 0.7 R, and cooling the parts thus locally heated thereby to form wash-back in each blade between the trailing edge and the heating paths thereof as a result of angular deformation accompanying plastic deformation due to the heating and cooling and thereby to decrease or increase the effective pitch of the propeller.

Patent
07 Aug 1975
TL;DR: In this paper, an electric motor drive for a propeller whose blade pitch is adjusted in dependence on the magnitude of the driving torque is described; the blades are positively connected to a bevel gear; these gears are rotatably mounted on both sides between 2 larger bevel gears, whose ability to rotate is mutually limited.
Abstract: Drive for a toy aeroplane has an electric motor drive for a propeller whose blade pitch is adjusted in dependence on the magnitude of the driving torque Preferably the blades are positively connected to a bevel gear; these gears are rotatably mounted on both sides between 2 larger bevel gears, whose ability to rotate is mutually limited, and are brought by spring elements into an end position in which the spring elements act in opposition to the direction of the driving force A freewheel coupling is connected between the propeller system and the drive shaft Best use is made of the available energy from a given engine wt; less noise is produced than by an internal combustion engine

Journal ArticleDOI
TL;DR: In this article, the hydrodynamic design of the Guided Missile Frigate (FFG) propeller involved "trade-offs" between full-power and design- endurance speed and considerations of blade strength, vibration, cavitation characteristics, and propeller blade spindle torque.
Abstract: The restrictions imposed on a propeller design by the controllable-pitch feature can be severe. In the case of the Guided Missile Frigate (FFG), the constraints were a controllable-pitch propeller absorbing 40,000 shaft horsepower (SHP), with distinct mission performance requirements related to propeller efficiency and cavitation performance. The hydrodynamic design of the FFG propeller involved "trade-offs" between full-power and design- endurance speed and considerations of blade strength, vibration, cavitation characteristics, and propeller blade spindle torque. Model experiments confirmed that considering the constraints imposed on the design, use of the best available design procedures and analytical techniques has resulted in a propeller for the FFG which has good overall performance.

Journal ArticleDOI
TL;DR: In this paper, the effect of thickness on the vibratory velocity field around the propeller is studied by means of the thin body approach, where the blade section is represented by a source-sind distribution of strength proportional to the slope of the blade thickness distribution.
Abstract: The effect of thickness on the vibratory velocity field around the propeller is studied by means of the "thin body" approach, where the blade section is represented by a source-sind distribution of strength proportional to the slope of the blade thickness distribution. A numerical procedure is devised and adapted to the CDC-6600 high-speed digital computer for the evaluation of the thickness effect on the velocity field. The total propeller-induced velocity field is then obtained by adding the computed velocity computed velocity components due to thickness, with proper phase, to the results due to propeller loading calculated by means of the lifting surface theory. Set of calculations performed a 3-blade propeller operating in a 3-cycle screen-generated wake and for a 5-blade propeller operating in a realistic hull wake reveal that the effect of thickness in forming the components of the resultant velocity varies from moderate to large depending on the magnitude of the thickness distribution, on the location of the field point and on the intensity of the nonuniformity of the inflow field.

Patent
03 Apr 1975
TL;DR: In this article, a rotatable central section and fixed sections on the same centre line on either side thereof are used to vary the pitch of the blades relative to a plane at right angles to the centre line.
Abstract: The lateral tunnel (12) is provided in the ship's bow section (10) below the waterline and has drive and reversing means. The tunnel has a rotatable central section and fixed sections on the same centre line on either side thereof. The central section is rotatable about its centre line and means are provided to vary the pitch of the blades relative to a plane at right angles to the centre line. The pitch varying means may comprise a ring around the central tunnel section and means connecting each of the blades with this ring such that rotation of the ring varies the blade pitch.


01 Jan 1975
TL;DR: In this article, the effect of pitch and camber on hull cavitation was investigated in a restricted draft tanker with a displacement of 475,000 DWt and measured in the Depressurized Towing Tank of the NSMB.
Abstract: In the past the trend of most ship designs turned towards higher speeds and larger displacements. Many modern cargoliners have cruising speeds close to, or in excess of 30 knots, and tankers with a displacement exceeding 250,000 dwt are in service on many trade routes. A consequence of this trend is the ever increasing power absorbed per propeller shaft. It is not surprising therefore that the propulsion aspects of these ships often pose severe problems. In particular, problems associated with propeller cavitation have become matters of great concern and also attention has to be paid to the propeller-induced forces on the shafting. The investigation presented in this paper comprises: (1) calculation and observation of cavitation behaviour; (2) calculation of dynamic propeller shaft forces; and (3) measurement of propeller-induced pressure fluctuations on the hull, of a restricted draft tanker of 475,000 tdw. The measurements were carried out in the Depressurized Towing Tank of the NSMB. The aim of this study was to determine the effect of camber and pitch of screw propellers in connection with propeller-hull interaction phenomena. From the results presented it is clear that the trade-off between pitch and camber in propeller design is important for the occurrence of cavitation and subsequent hull excitation considerations. It is demonstrated that whereas a relatively high pitch will always lead to sheet cavitation on the suction side, due to relatively high angles of attack of the flow, the subsequent influence on hull excitation is nevertheless more constant. The tendency is that the peak-to-peak values in such a case are smaller than the respective values for a design in which the camber is relatively high and the pitch is relatively small. In the latter case the occurrence of cavitation is less, but when it occurs the cavity is very large and unstable due to the relatively low pressure distribution along the whole blade section.