PRAENUNTIUS FUTURI "I"
By J.V. Ferrero, LT, USN
Jim Ferrero was the Engineer on Albacore at the time of writing this piece. This article was published in a submarine "Combat Readiness" publication and in a SubLant Information Bulletin in the 1956-57 time frame. What is interesting is that the Virginia class SSN's have Pilot and Co-Pilot stations.
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(Note: Words in italics are the editor's.)
The art of flying a submarine has at last become a reality. As one steps aboard the Albacore, he becomes aware of a whole new concept in submarining. Terms here-to-fore foreign to submariners resulted from many months of experimentation by Albacore and her crew. These terms were developed to adequately and precisely describe what happened to the ship, her control surfaces and to her relative position in the sea's depths.
It was indeed a problem to explain a maneuver in which a submarine descends from a depth of 100 feet to 600 feet and in doing so performs a "Diving-S-Turn" or "Figure 8" evasive or counter-attack maneuver! "Aerobatic Flying" is our answer. Such similar terms as "level flight", "roll her over", "less bank" and so forth have been accepted by us and are used freely to describe the desired behavior of the submarine.
The Albacore today is to the conventional submarine as the jet fighter was to the propeller-driven aircraft. Hydrodynamically, the new terms of submarining are basically sound and accurate. Whereas the older surface vessel was able to submerge and thereafter acted more or less as a free balloon that was capable of being moderately directed and driven through the water and was satisfactorily controlled with "plane angles", "bubbles", "blow negative to the mark" and so forth, the Albacore necessitates changed thinking and reaction.
This vessel was basically designed as a true submersible. She was meant to spend months underwater. Because of the limitation imposed by a conventionally designed power system, this is not possible. Albacore is truly "flown" through the water as either a heavier-than-aircraft or a lighter-than-air-craft. Hydrodynamically less dependent on neutral buoyancy than one imagines, she is as much in her element, water, as a blimp is in its element, air.
The analogy between blimps and Albacore is very similar. The blimp is restricted to a certain altitude as the Albacore is restricted to a collapse depth. The speeds of both units are closely akin, the blimp slightly higher. Both share the problem of ballast, trim, buoyancy and bank. As a matter of fact, as one looks at the Albacore, he can easily visualize a blimp upside down!
The designer of the Type 21 German submarine is reputed to have said: "The future of sea warfare belongs to that which can maneuver in three dimensions - the airplane and the submarine". At long last, we feel that our navy has developed and built the submarine that will fulfill the undersea portion of this saying.
Perhaps as we continue to investigate the problems of high speed submarining, we will turn more and more to the aeronautical field for the results and techniques which they obtained years ago in the wind tunnel and in the air.
One of the many problems to be faced with such a vehicle is the development of a different concept in control necessities and terms. Appreciation of the safe and reliable maneuvering of this "male whale" at speeds of more than 25 knots requires greater controllability than was necessary for the 9 knot "fleet boat" of yesteryear. We can no longer speak in terms of bubbles, depths, plane angles and rate control systems. We must speak in terms of predictions, errors, and position-control systems in order to use to the fullest the capabilities of the Albacore-type hull.
The following abbreviated glossary of terms is listed in order to promote an understanding and discussion of the instrumentation deemed essential in this vessel.
DEI - Depth Error Indicator
DGI - Digital Gyro Indicator
RDI - Rate of Dive Indicator
AS - Automatic Steering
AH - Artificial Horizon
ADC - Automatic Depth Control
BPI - Bow Plane Indicator
SPI - Stern Plane Indicator
The DEI is a linear gauge that represents, by sliding pointer, the difference between actual depth and the desired depth. It is a differential type instrument, the desired depth being an input manually set by the Pilot. It is graduated from 50 feet above depth, through 0 error, to 50 feet below the depth.
The RDI presents the absolute rate of rise or of dive in feet per second. It is dependant, or is the result of the speed of the vessel through the water and the pitch angle of the ship. A range pf 30 ft/sec in either direction will suffice.
The AH is the same type of instrument used by airmen to maintain level flight. From it, the Pilot may read the submarine attitude of up or down angle and bank.
The DGI is used for steering and presents the course when read vertically from top down on three display wheels.
The BPI and SPI display the number of degrees the planes have displaced from their neutral or "0" position.
The AS and ADC are equipment systems used as "Iron Mikes" or "auto pilots" to maintain the ship in level flight over extended periods of time while in transit or on patrol station.
These "sensing" instruments show the Pilot what he wants to do. Let us momentarily look at what he has in the way of hull appendages and controls thereof. The Albacore has the usual bow planes, stern planes and rudder planes, a single propeller and a separate dorsal rudder at the trailing edge of the sail fairwater. Her controls consist of "position" type sticks, wherein the Pilot turns his helm wheel a given arc or amount and the rudder follows up until it reaches this ordered signal and then moves no further. Similarly, by pushing or pulling a given displacement on the bow and/or stern plane sticks, the planes follow until they have reached the ordered position and remain there until a new position is ordered.
Before proceeding into the use of the operational controls of a high speed submersible, the necessary accurate, compact and minimum number of indicators must be arranged so that the pilot has easily available, within a small field of vision, only those instruments he needs.
The following sketch of such a panel is proposed as a simplification and rearrangement of instruments presently installed. Such a panel is being built by a commercial company and will be soon evaluated on board this vessel.
Now that the basic terms and a desirable control panel have been discussed, we will go into their use. The two basic stations will be located in the Control Room. Each station will be identical as to instruments and controls and will be capable of controlling all appendages or of selected parts of them. The Diving Officer will be the Pilot in one seat and a well-trained enlisted man will be in the Co-Pilot seat. This idea has been investigated by Albacore and the results have been very encouraging. The Diving Officer, after sounding the diving alarm, takes over the Pilots chair, which may be called the Stern Plane Station for these are the controlling diving appendages. The handling of routine reports, opening the vents and items involving destroying positive buoyancy, are handled very efficiently by the Chief of the Watch, who might well be called the Flight Engineer, with a complete absence of spoken words if conditions are normal. The Diving Officer orders the remainder of the diving evolutions by setting rate of dive desired and by setting the desired depth. The Co-Pilot, using single stick control, rolls the ship over until he obtains the desired rate of dive.
The Flight Engineer shuts and cycles the vents, blows Negative and turns "on" or "off" the hydraulic plants as the ship passes stated depths.
Notice that the actual position of the planes, the speed of the boat, or angle of the boat does not matter to the Co-Pilot. He is solely interested in the effect of his planes to obtain the rate of dive. This again is similar to the method used by airmen to control a blimp.
A new "stick" is being investigated that will give the Pilot a greater sense of feel for his planes. In this manner, he will be able to tell by the amount of force necessary to displace the stick, increasing as the distance from neutral is increased, the approximate position of his appendages without having to look down at the relative movement out of the zero position or at plane angle indicators. From experience, the Co-Pilot will soon learn about how much planing is required, at a given speed, to initially obtain the an angle such that the ordered rate of dive may be reached quickly and the planes then eased to hold the rate of dive. The RDI is the only instrument the Co-Pilot has looked at thus far. He now shifts his gaze to the DEI which is pegged at 50 feet above ordered depth. When the pointer begins to move, the Co-Pilot pulls back on his stick to level the ship and to settle down at the ordered depth. Both RDI and DEI will now read "0". Any displacement denotes the need for corrective action.
While the Co-Pilot holds the depth, the Pilot notes on the AH the attitude of the ship and orders the changes in trim and speed such that the ship may settle down to an ordered speed with minimum use of the planes.
At such a point, the ADC would be turned on. Similarly, the course would be set and the AS started. Such would be the normal procedure.
Note that, with high speed submarines, an angle over twenty degrees need never be used in attacking, evading or in large depth changes for the increased speeds at the smaller angles easily accomplish the large rates of rise or dive. As a matter of fact, the Albacore changes depth very rapidly even with zero angles on the boat and full bow plane action. This tactical feature may have value in the fire control and weapons launching program.
The major reason for two stations is that the Diving Officer can instantly take over the control of the vessel by turning one selector switch and can save a considerable number of seconds that would be wasted had he needed to order his ideas to the human amplifier, who would then react to do what he thought the Diving Officer wanted done, in coping with a casualty, attack or evasion. Normally, the Co-Pilot would fly the ship; the Pilot would rest in his seat constantly observing what was going on. The Flight Engineer would observe those gages, lights, indicators and manifolds that tell the story of the performance of the ship, but which the pilots need not have in their normal field of vision to successfully fly the submarine in its controlled movement through the depths.
Without actually riding the Albacore and experiencing the great strides that have been made in submarine design, controllability and reaction time, some of the ideas expressed may seem radical and difficult to believe. Perhaps by listing some of the tactical characteristics and performance data, the reader may more readily accept the necessity for new words and controls. Appreciate, if you will, that all of the facts stated herein have been checked and proven by exhaustive controlled tests and were used recently by the vessel in ASW operations at Key West, Florida against the best equipped and manned ASW surface ships.
Albacore can turn at a rate of 5 degrees per second (a jet plane has a standard rate turn of 3 degrees per second). In diving, a rate of descent of 25 feet per second is possible. Acceleration from 2 knots to 27 knots is accomplished in 2 minutes 40 seconds (a destroyer takes almost 7 minutes to do this). The Albacore may be slowed from maximum speed to 7 knots in a matter of about half a minute. The Albacore can turn in a tactical diameter of 165 yards (DD's require some 1,100 yards at the same speed). The Albacore's eleven foot, slow speed propeller is located in the uniform flow wake and therefore can be run at a speed 50% greater than a conventional guppy before cavitating.
It is readily seen, we believe, that there is little comparison between Albacore and the best of the conventional submarines. The one obviously limiting factor in the Albacore's performance is the endurance of a battery-propelled submarine. However, this will not long remain a problem, for with the marriage of the Albacore hull and the nuclear power plant, the endurance problem will be resolved and continuous speeds in the range of 35-45 knots will result.
The purpose of this article has been to acquaint as many submariners as possible with the latest trends in our chosen profession and to aid all to better anticipate the changes and philosophies that will be forthcoming in our submarine force. Whole new concepts of words, tactics, communications and weapons are necessary to utilize the vehicle that is at hand. We on the Albacore are proud of our motto "PRAENUNTIUS FUTURI" which means literally "portent of the future" or "forerunner".