10 Patents 2,843,288 and 3,142,458. Such systems are not as efficient as desired and are not readily adaptable to a wide range of aircraft weights and landing speeds . An object of this invention is, therefore, to provide a pro¬ grammed control system which efficiently arrests a wide • _j c range of aircraft weights and speeds. Another object is to provide a simple, economical and dependable type of such a system.

A programmed aircraft arresting control system for a variable K factor energy absorber having a movable control s lement which is movable into a number of positions, each causing the energy absorber to operate at a different K factor, utilizes a programming means establishing a predetermined speed parameter for an arrested aircraft. The speed parameter has different phases of arrestment, for example, an initial and a final phase. A speed-sensing means, for example, a pump driven from the arresting tape reel, determines the instantaneous speed of the arrested aircraft. A comparison means, for example, a linkage driven by the pump, compares* the in¬ stantaneous speed with the corresponding portion of the speed parameter of the program (for example cam and follower.) whereby aircraft speeds in excess of the para¬ meter are detected. An actuating means including, for

_. • example a switch between the linkage and cam follower and associated solenoid valves and electrical circuitry, causes the control shrotid to move to a predetermined higher K position if the speed parameter is exceeded in a correspond¬ ing phase of arrestment. In other words, the cam has a contour which defines an initial arresting phase and a final arresting phase. The switch on the cam follower and additional follower switches, solenoid valves and cir- cuitry are constructed and arranged to actuate the drive means to set the control element in the low K position at the beginning of the initial phase, in an intermediate position if the speed parameter is exceeded during the initial phase, and in a high K position if the speed parameter is exceeded during the final phase. The control element is moved to the high K position at the end of the final phase if it is not already there. The actuating means also includes, for example, a limit switch which defines the intermediate position and a disabling switch connected to the limit switch, which may be actuated dur¬ ing the final phase. The drive system has a slower and faster >rates of movement with the slower rate only pro¬ vided during the final phase of arrestment. The drive

means also, for example, may include a movable cylinder shell and a fixed piston. A rewind control causes the control element to be set in its low K position to vacilitate rewind.

Brief Description of the Drawings

Novel features and advantages of the present invention will become apparent to one skilled in the art from a reading of the following description in conjunction with the accompanying drawings wherein similar reference characters refer to similar parts and in which:

Fig. 1 is a schematic diagram of a programmed aircraft arresting system, which is one embodiment of this invention in conjunction with the variable K energy ab¬ sorber; and

Fig. 2 is a chart of rpm vs. payout for three different aircraft relative to a trigger rpm curve utilized on the cam shown in Fig. 1.

Description of the Preferred Embodiment

The control device shown in Fig. 1 may for example, be positioned in a housing (not shown) installed on top of the energy .absorber 40 and may be anchored to its foundation by means of an unillustrated pipe bracket which also functions as a conduit for electric connectors between the control device and shroud control cylinder 15.

As shown in Fig. 1, connected to the shaft 42 of energy absorber 40 by belt transmission 44 is hydraulic pump 1 with its inlet port via filter 14 connected to -. ^* reservoir 2 and with its outlet port connected to spring- returned cylinder 3. The inlet port and the outlet port of the pump 1 are connected via a fixed restriction 4 and a pressure relief valve.

Piston rod 6 is attached to lever 7 which pivots in fixed bracket 8. Cam follower 9 carrying micro- switch 10 is pivoted around fixed bracket 11 and held against cam 12 by spring 13.

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Dual cams 12 and 12A are rotated by shaft 42 of energy absorber 40 via a gear and timing belt trans¬ mission 30 so that cam 12 rotates less than 360° for abou 80 revolutions of absorber shaf 42. 7Two* more follower switches 24. and: . 28 are installed in contact with a smaller cam 12A.

Energy absorber 40 is, for example, of the type described in U.S. Patent Re. 28,736. The shroud mechanism disposed inside the housing of energy absorber 40 includes shroud 32 with three positioning rods 33 operated by cam ring 17. Cam ring 17 is rotated by cylinder 15. Cylinder rod 16 is fixed to the absorber housing at each end of cylinder shell 15' which is con¬ nected to cam ring 17 via bracket 22.

The two ports of cylinder 15 are solenoid valve 18 and solenoid valve 19, connected to pressure line 20 and reservoir 21. Another solenoid valve 23 is connected to one of the ports via restrictor 25 and a restrictor 26.

The position of lever 7 is a function of. shaft rpm as a consequence of the flow-dependent pressure drop across orifice 4. The positions of cam follower 9 and switch 10 are a function of the purchase tape payout (number of revolutions of absorber shaft 42) for a given cam 12 profile. The orifice 4 size and cams 12 and 12A profiles are matched so that switch 10 is activated when shaft rpm exceeds the trigger curve in Fig. 2 for a given payout.

The status of switch 24 is a function of the purchase tape payout (number of revolutions of the absorbe shaft 42) .

During stand by the positions of the solenoid valves are as follows :

Valve No. 18 - Position 1 - No Flow

Valve No. 19 - Position 1 - No Flow

Valve No. 23 - Position 1 - High Flow Ra

Cylinder 15 is in its right-hand or "A" position which provides an almost closed "A" position of shroud 32 re¬ sulting in the lowest of three K-positions.

When engaging a light low-speed aircraft (Alpha-Jet) , the rpm vs. payout curve as shown in Fig. 2 results in no status change of shroud 32 until a pay¬ out of 735 ft. is reached. Solenoid valve 23 will, as a result of cam 12A actuating switch 24, shift to low flow rate position 2 at 250 ft. payout and back .agian to high flow rate position 1 at 735 ft. payout. However, as a result of the position of valve 18 (no flow) , this has no effect on cylinder 15 before 735 ft. payout.

When reaching 735 ft. payout, cam 12 actuates solenoid valve 18 via switch 10 causing a flow through liquid orifice 25 to the left-hand* chamber of cylinder 15 moving shell 15' to the left, fully opening shroud 32 to the "C" (maximum K) position. Switch 28 is actuated by cam 12A overriding switch 29, which already has been actuated by shell 15' . This allows shroud 32 to open com¬ pletely resulting in the maximum K-factor at the end of the runout.

Restrictions 25 and 26 provide different cylinder 15 velocities and cam 12A is designed to activate solenoid 23 via switch 24 at 250 ft. payout and deactivate solenoid 23 at 735 ft. payout.

When engaging a medium weight high speed air¬ craft (F-104) , the rpm vs. payout curve shown in Fig. 2 results in an early (before 250 ft. payout) crossover of the trigger rpm curve. Solenoid valve 23 is consequently ^' in position 1 when switch 10 shifts solenoid valve 18 to flow. This results in a high rate K-increase (through restrictor 25) . When the intermediate K-factor is reached, switch 29 is activated to shift valve 18 back to "no flow" and stop cylinder shell 15'.

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When a payout of 735 ft. is reached, switch ^' 28 through cam 12A overrides switch 29 to shift a valve 18 to flow, thus moving cylinder shell 15' and shroud 32 to their "C" positions and increasing the K-factor to its highest value.

When engaging with a heavy weight high speed aircraft (F-4) the rpm vs . payout curve shown in Fig. 2, results in an early crossover (before 250 ft. payout) followed by a late (after 250 ft. payout) crossover of th trigger rpm curve.

Before 250 ft. payout, solenoid valve 23 is in position 1 when switch 10 shifts solenoid valve 18- to flow. This results in a fast K-increase (through re¬ strictor 25) . When the intermediate K-factor is reached, switch 29 is activated to shift valve 18 back to "no flow" and stop cylinder shell .15' . ^* hen a payout of 735 ft. is reached, switch 28 through cam 12A overrides switch 29 to shift valve 18 to flow, thus moving cylinder shell 15' and shroud 32 to their "C" positions and increasing the K-factor to its highest value.

When engaging with a heavy weight high speed aircraft (F-4) the rpm vs. payout curve shown in Fig. 2, results in an early crossover (before 250 ft. payout) followed by a late (after 250 ft. payout) crossover of th trigger rpm curve.

Before 250 ft. payout, solenoid valve 23 is in position 1 when switch 10 shifts solenoid valve 18 to flow. This results in a fast K-increase (through re- strictor 25) .

When the intermediate K-factor or "B" position is reached, switch 29 is activated, by contact with projection 29a on cylinder 16, shifting valve 18 back to no flow to stop cylinder shell 15' in the "B" position. Reaching a payout of 250 ft. cam 12A actuates switch 24 shifting valve 23 to position 2 resulting in a lower rate of K-increase (through orifice 26) when switch 10 at the second crossover overrides, switch 29 changing valve 18 to flow causing shell 15' and shroud 32 to move their "C" positions. The K-factor increases to its maximum value and consequently no reaction occurs at the third crossover (after 735 ft. payout) except that switch 24 shifts valve 23 back to position 1.

During rewinding after an arrest, a switch in rewind control handle 35 actuates valves 18 and 19 to positions 2 resulting in a closing of shroud 32 to the "A" (low K) position. After completing rewinding and pre- tensioning, all valves are automatically reset to their standby position. Fig. 2 shows four curves. Peaked trigger rpm curve 50 represents the contours of dual cams 12 and 12A. It accordingly establishes speed limits for the arrested aircraft through payout expressed in rpm of the tape reel. The maximum speed of approximately 1100 rpm is established at 250 ft. of payout. The contours of curve 50 are developed to accommodate an engagement made at the velocity of 170 knots with a constant deceleration of 1.5 G maximum with no dynamic peaks for the heaviest air¬ craft and a landing speed of 138 knots of 1.0 G decelera- tion maximum for the lightest aircraft.. Decelerations are maintained below 1.5 G for all other aircraft.

The landing speed of the lightest aircraft is represented in Fig. 2 by a curve 52 which represents the landing speed of an Alpha et weighing- 13,400 lbs. and landing at approximately 115 knots . It crosses over trigger curve 50 only at the end of the payout when shroud 32 is shifted into the "C" or high K position.

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Curve 54 represents the landing speed of an intermediate weight F 104 weighing 17,500 lbs. landing at 180 knots . This curve crosses over trigger curve 50 at about 10 feet of payout when cylinder shell 15' and shroud 32 are moved into their intermediate "B" positions to pro¬ vide an intermediate K factor for the energy absorber throughout the remainder of payout when the final cross¬ over provides the high K position.

Curve 56 on Fig. 2 represents a heavy weight F-4 aircraft weighing 59,000 lbs. and landing at 160 knots. It crosses over trigger curve 50 at about 20 feet of pay¬ out to shift shroud 32 into the "B" intermediate K positio It again crosses over trigger curve 50 at about 320 ft. to cause cylinder shell 15' shroud 32 and energy absorber 40 to move into the extreme high K position throughout the remainder of the arrestment.

The G forces applied to light, intermediate and heavy aircraft are thus maintained approximately between 1.0 and 1.5 G throughout their arrestment utiliz¬ ing a single program or cam contour"

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