US2357304A - Antispin attachment for link trainers - Google Patents

Description

- septf 5, 1944.

M. c. BALSAMO ANTISPIN ATTACHMENT FOR LINK TRAINERS Filed Aug. 5, 1943 2 Sheets-Sheet vl N .mi

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Sept. 5, 1944. l vVM. c.v BALSAMC? ANTISPIN ATTAGHMENTAEEINK TRAINERS Y Filed Aug. 5, 1945 1N VEN TOR M/CH/qeL C. 544

A TTORNE YS Patented Sept. 5, 1944 om'rso STATES Param* ortica ANTISPIN ATTACHMENT FOR LINK TRAINERSV Michael C. Balsamo, Dayton, Ohio Application August 5, 1943,y serial No. 497,537 6 claims. (C1. :i5- 12) (Granted under the act of March s, 1883,v as amende'dApril 30, 1928; 370 O. G. 757) kof vacuum to the stall valve bellows is necessaryfor normal operation; consequently the trainer begins to spin immediately upon turning on the turbine which provides a vacuum source for all the diiierent bellows and vacuum lines of the trainer. Heretofore, it has been necessary for the instructor prior to turning o-n the turbine to remove a side panel from the ktrainer fuselage and reach in and take hold of the inverted pendulum, which is a part of the stall valve assembly, so that the student could climb into the trainer and be seated and'assume full control without being subjected to the spin. The general object of the invention is to provide a mechanism which will automatically prevent the trainer from spinning when the turbine is rst turned on, while permitting all parts of the trainer to function normally at all other times. The invention thus saves the time of the instructor and also that of the student, since the latter need no longer direct his attention to recovering fromV a spin before proceeding with the assigned problem. The preferred mechanism is a very simple time-delay device which prevents the stall valve pendulum from moving to itsY operative position for a predetermined time after the trainer is started. Further objects are to provide a device for the purpose stated whose cost is negligible and which is easily installed and requires little or no maintenance.

Reference should be made to Link Patent No. 2,099,857, dated November 23, 1937, for a fuller understanding of the Link trainer.

In the accompanying drawings,

Fig. l is a perspective view of the stall valve assembly of a Link trainer with a stop device attached thereto, in accordance with the invention;

Fig. 2 is a sectional elevation of the stop device per Se;

Fig. 3 is a detail view in elevation; Fig. 4' is a perspective view of the mechanism for causing the trainer to spin, together with the rudder-controllingv pedals, certain associated parts; and

Fig. 5 is a perspective of the spin valve assembly, which deter-mines the direction of spin.

Fig. 6 is a side elevation of a Link trainer fuselage, minus the wing, showing the location of the stall valve assembly of Fig. l.

Referring particularly to the drawings, the stall valve assembly of Fig. l (corresponding in function to the stall valve of Figs. 14, 22 and 23 of said Link patent) comprises a stall valve bellows I0, one end of which is secured to and carried by a bracket II which may be an extension of one arm of a V-shaped upright frame I2. Integral with V-frame I2- and extending at right angles is a horizontal base plate I3 which may be screwed to the floor of the trainer cockpit (not shown). The stall valve body I4 is fixed on base plate i3 and has a vacuum line I5 to the trainers climb-k dive Ytank (not shown) controlled through a needle valve (hidden by valve body I4) and also has-an atmospheric inlet I6 and an air lter I1 at the upper end of the inlet I6. A valve stem I8 projects from one end of the valve body to a point between the arms of the V-frame, and an'inverted pendulum I9 is secured at its lower end to said valve stem to turnthe same o-n its longitudinal axis thereby to open and close theneedle valve by means of a left-handed screwv thread not shown. The inverted pendulum I9 oscillates in a vertical arc and has a weight. |l at-its upper vend and a longitudinal slot |91) for receiving a stud 2l which is tightened at any point along the -slot by a nut, 22. Stud 2| transmits movement of the inverted pendulum to or receives movement from a slotted bar 23 (slidably mounted on the upper ends of the two armsof the V-irame) by contact Witheither of two vertical ngers 24, 25, adjustable along the respective slots of bar 23. Clamping screws 26 secure iinger's 24, 25, at the desired points. A stop screw 21 is screwed through one of the arms of the V-frame near its upper end and is so 1ocated that one end may be engaged by the inverted pendulum to limit its arc of movement in one direction.

When the speed of an airplane drops below a certain minimum, the airplane stalls and sometimes starts to spin. This characteristic is built into the Link trainer. The bellows I0 is connected by tubing 28 to the vacuum line extending from the -air speed regulating bellows to the air' speed transmitter (not shown), so that the same Vacuum is applied to the stall valve bellows as to the air speed transmitter. At normal air `42, 44, i-s always under speed, this suction is strong enough to keep the bellows i6 collapsed, overcoming the'tension of spring 29. One end of spring 29 is anchored to the rear wall of the cockpit or other convenient upright fixed member 29a, while the other end is secured to bellows I!) (Fig. 3) in such a manner as to oppose the collapsing of the bellows by vacu-um suction. In this position, the bar 23, one end of which is pivotally attached to the movable part of the bello-ws, holds the inverted pendulum (by engagement of finger 25 with stud 2|) in its forward position against the stop screw 21. The atmosphere is then entering atmospheric vent 30 in a three-way jet assembly 3| and between the line from the main vacuum supply and the line 32 to the spin-trip bellows 43 (to be described). See Fig. 4. A corresponding atmospheric vent is v not found in said Link patent. Due to a restriction built in to the vacuum side of this connection, the atmosphere entering vent 30 is sufficient to reduce the vacuum to the spin-trip bellows line 32 so that the spin-trip bellows remains open; As the simulated air speed is decreased, the suction on the stall bellows is correspondingly reduced, and when the suction is suihciently reduced, the tension of spring 2B overpowers the suction. and opens the stall bellows. As the stall bellows opens, bar 23 by means of iinger 24 pulls the pendulum back toward the other arm of the V-frame. This opens the stall valve and closes vent 30 (by a seal 33 on the pendulum, to which there is no corresponding part in said Link patent) to permit full suction to be applied to the spin-trip bellows causing the trainer to spin.

Before describing the attachment, the action of the mechanism for effecting automatic spin of the trainer should lbe made clear. Referring to Fig. 4, the bank-turn shaft 4U is solid and supports a hollow shaft 4|, which is sometimes free to turn and, at other times, is locked to the bankturn shaft. Three bellows 42, 43, 44, are mounted on the hollow shaft 4|, together with a latch 45; the spinbellows 42 and 44 at the top and bottom actuating the rudder valve in opposite directions when the trainer is spinning and intermediate bellows 43 (the spin-trip bellows) working the latch 45, as will be described. Compare Fig. l2 of the Link patent, which shows a somewhat similar arrangement. One of the spin bellows vacuum, hence collapsed, while the other is expanded under the action of a V-shaped spring 46, there being one of said springs for each of the three bellows. An arm 41 is secured at one end to the solid inner shaft 46, and has a notch 41a for receiving latch 45. Another arm 48, which carries the latch, is anchored at its opposite end to the hollow shaft 4|. Latch 45i-sv pivoted as at 45a upon an arm 45b fixed to the spin-trip bellows, and as long as it engages arm 41, the two shafts 40, 4|, are locked together and the assembly functions only to provide an automatic turn with banking. When the simulated air speed falls below the predetermined stalling speed, the pendul-um I9 closes vent 30, causing increased vacuum line 32 to the spin-trip bellows 43. This increased vacuum closes this bellows which moves latch 45 out of notch 41a in arm 41. The hollow shaft 4| is still held rigid by an arm f49 (which is connected to banking rod 50 extendingA down through the floor of the fuselage to the trainer octagon 85), but arm 41 and the inner shaft 46 are free to turn. Assuming that vacuum is being applied to the top bellows 42, with the to be applied to the.

latch released, as described, the top bellOWs Closes, 75

pushing arm 41 down by means of rod 5|, link 52 and pin 53, and rotating the inner shaft 46. This swings a bell crank 54, which moves walking beam 55, pulling the rudder valve 56 wide open by means of a rod 51, causing the trainer to spin. Figs. 8, 9 and 12 of said Link patent show a corresponding rudder Valve. The rudder valve is connected through a tube S6 with the motordriven vacuum turbine (not shown) which is the source of vacuum for all vacuum-operated parts of the trainer. Tubes 9|, 92 connect the rudder valve with the turning motor (not shown).

Selection of the particular spin bellows 42, 44 which shall be under vacuum is the function of the spin valve 60 (Fig. 5). Compare Figs. 12, 24 and 25 ofthe Link patent, parts 236 to 244 inclusive. This valve is a two-way valve connected on one side to the vacuum supply through line a and on the other to both spin bellows through lines 60h, 60C. It has an inverted pendulum 6|, whose position determines the bellows to which vacuum shall be applied. Pendulum 6| normally falls toward the lower side of the fuselage but can be thrown to the opposite side by use of pivotally mounted rudder pedals 62, 63, through a fork 64, which extends back from the rudder bar 65. Rudder bar 65 is swung by foot pressure on the rudder pedals, which is transmitted through wire cables 65a, 65h to the ends of the rudder bar. Pedals 62, 63 are normally balanced or held in upright position by tension coil springs 62a, 63a, respectively, which keep the cables 65a, 65D under tension. Said coil springs are anchored at their opposite ends to the cockpit footboard 62h or other stationary part of the fuselage. Rudder bar 65 has rods 65e attached to each end thereof (only one, however, being shown in Fig. 4) and connected to the rudder 83 (Fig, 6) of the trainer soas to turn the rudder when the pedals 62, 63 are depressed. Stops 66, 61 for pendulum 6| are provided by the ends of a stationary frame 68, which mounts the spin valve 66. As long as the air speed remains below stalling speed, spintrip bellows 43 will remain collapsed and the latch 45 will remain raised where it cannot engage notch 41a in arm 41. During this time, full application of the opposite rudder will throw the spin Valve pendulum 6| over and apply vacuum to the other spin bellows. As this bellows collapses, it will swing arm 41 past latch 45 and will move the rudder valve around to fully open position inthe opposite direction. This will reverse the direction of the spin, but normal rudder control cannot be regained until normal air speed is attained. To recover from a spin in the Link trainer, it is necessary to nose down to regain normal air speed, and also to apply the rudder for a full turn in the direction opposite to that of the spin. When normal air speed is attained, the stall valve pendulum I9 moves away from vent 3|), allowing the atmosphere to enter, which decreases the vacuum to the spin-trip bellows, whereupon the latter expands responsive to its spring 4S. This returns latch 45 to its locking position. The application of full rudder, already mentioned, throws the spin valve pendulum 6| over, whereupon the other spin valve bellows starts to collapse, attempting to swing arm 41 past the latch. But the latch, now in normal position, engages notch 41a and thus locks shaft 40, restoring normal rudder control.

Mounted on the stall inder valve bellows l!! is a cyl- 10 secured by screws 1| passing through a bracket 12, Within the cylinder is a conical coml pression spring 'I3r (Fig.2), one end of which abuts the end wall of the cylinder, while thek other end presses against a piston 'Mhaving a rod 'I5 extending out-side the cylinder. The piston rod constitutes a retractible stop which Vis engaged by the pend-ulum I9, whenever the latter moves toward the vent 30, provided the piston rod 'I5`is extended bythe spring as illustrated in Fig. 1. Thus the seal 33 cannot close the vent 30, and the trainer will not spin, so long as the retractible stop is in the path of the pendulum. A vacuum line 'I6 from the manifold (not shown), which is connected with the vacuum side of the turbine, leads to the upper end of the cylinder, but due to a bleed-hole I'I in the cylinder this vacuum is not immediately eiective in drawing the piston up to the top of the cylinder against the compression of the spring. Bleed hole 'I'I lets atmospheric air in the cylinder, when suction is applied thereto, and reduces the vacuum, hence increases the time delay of the device, which may be about six seconds. Another small hole 18, in the lower end of the cylinder, facilitates movement of the piston toward the bottom of the cylinder.

The operation is as follows:I When the turbine is rst turned on, pendulum I9 moves toward stop 21 before the retractible stop 'I5 is retracted within the cylinder. Thereafter, the stall valve a-ssembly will function normally, and the trainer will start to spin if the student permits the indicated speed to fall below the stalling speed. This is as it should be. When the turbine is turned off, the conical spring overcomes the reduced vacuum in the cylinder, pushing stop 'I5 to its extended position (Fig. 1) before pendulum I9 moves toward vent 30. Therefore, the pendulum can never seal said vent when the trainer is out of operation, and the undesired initial spin e already described can never take place.

The usual location of the stall valve assembly, as indicated in Fig. 6, is below the removable seat on which the `student sits while in the cockpit. Access to the cockpit is through a door 80 hinged to a side wall of the trainer fuselage 8l. A hood 82 may be lifted or lowered at will, and when lowered will completely shut off the students Vision, -forcing him to fly on instruments. A rudder 83 and horizontal stabilizer 84 are also shown. The trainer Octagon 85, which revolves with the fuselage, is indicated. The wing, which would normally appear below and to the left of door 80, has been omitted for clearness, and, of course, many details are omitted because of the small scale of the figure,

Bracket 12, which secures the cylinder to the bellows I0, is adjustable (not shown), hence the device may be mounted on all the different models of Link trainers. As the attachment is very simple, its manufacturing cost is quite low, and installation and maintenance costs are negligible. The described arrangement permits the altimeter of the trainer quickly to attain its lowest reading when the turbine -is shut off, which is a distinct advantage.

Obviously, other known forms of time-delay'devices may be used to perform the same function as the device described above. Furthermore, as will be clear to those skilled in the art, it is unnecessary to mount the attachment on the stall valve assembly, as there are other point-s on the Link trainer where a time-delay device may be used to prevent the initial spin mentioned above. Some of the parts of the Link trainer shown in the drawings but not claimed herein may be covered by` claims in pendingapplications owned by or'licensed to' Link AAviation Devices, Inc.

Having described my invention, what I claim as new'and desire to secure by Letters'Patent is:

1. For use in an aviation ground trainer of the character wherein av fuselage forming a cockpit enclosure is provided with student-operated 'control means operativev to control power means for causing tilting ori vrotational movement of the 4fuselage about a base and having a valve means for causing rotation -of the trainer fuselage to simulate an airplane spin condition upon decrease in indicated air speed to a predetermined value; that improvement which consists, in combination with said valve means, of a time delay means associated with said valve means and operative upon energizing of said trainer power means to render said valve means inoperative for a predetermined period of time.

2. In combination with the spin-trip bellows and the stall valve assembly of a Link trainer, said stall valve assembly having an inverted pendulum, a seal on the pendulum, a vacuum line leading to the spin-trip bellows to operate the same, said vacuum line having a vent to the atmosphere, and the seal being adapted to close said vent to render the vacuum line operative; a stop device having a part which automatically moves into the path of said inverted pendulum to prevent said pendulum from sealing said vent; said automatic movement taking place invariably when the turbine which actuates the trainer is out off; said stop device being constructed and arranged so that it automatically moves out of the path of the pendulum after a time delay when the turbine is started.

3. The invention according to claim 2, wherein said stop device comprises a cylinder, a springpressed piston in the cylinder, and a piston rod; the piston rod extending outside the cylinder, when the spring is effective, to act as a stop for the pendulum; and a vacuum line connected with source of vacuum of the trainer and also to the cylinder to draw the piston rod up in the cylinder against the resistance of the spring.

4. An attachment for the stall valve assembly of a Link trainer comprising, in combination, a bracket adapted to be mounted on the stall valve bellows; a cylinder secured by said bracket; a piston reciprocable in said cylinder; a piston rod extending outside said cylinder and adapted to act as a stop for the inverted pendulum of said assembly when suiciently extended; a vacuum line connected to the cylinder; a spring in the cylinder acting against the piston in opposition to the suction ofthe vacuum line; and a bleed hole in the side of the cylinder to retard movement of the piston responsive to the vacuum suction.

5. in combination with the stall valve assembly of a Link trainer, a time delay device having a part which always tends to project into the path of the inverted pendulum of that assembly as said pendulum moves toward the vent which leads to the spin-trip bellows; and means actuated by .and upon turning on the trainer to cause said part to move out of said path after a predetermined time delay, so that the stall valve assembly is restored to its normal operating condition.

6. For use in an aviation ground trainer of the in combination with said spin-trip bellows, of mechanism attached lto the trainer to automatically prevent the application of su'cient Vacuum to operate the spin-trip bellows when the trainer is rst turned on, said mechanism 'having a time delay action to permit normal operation of the spin-trip bellows a short time after the trainer is turned on.

MICHAEL C. BALSAMO.

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