Dead Reckoning Procedure

[Music] To reach enemy objectives, no matter where they are, is a primary function of our air forces. This function calls for skilled navigators familiar with the basic method of aerial navigation, dead reckoning. In flights over land and sea, dead reckoning is used by itself and in conjunction with other methods of navigation. The principles involved are adaptable to any specific situation. This navigator is about to prepare for a typical flight mission that will take a navigation training airplane from Albany, Georgia to Greenville, South Carolina. He starts his pre-flight preparation hours before the takeoff. Daily weather maps and hourly reports give him current conditions aloft and forecast weather conditions to be expected. Checking the winds aloft charts, he finds that his northeast course to Greenville will be favored by a tailwind at 7,500 ft. This he jotss down for future reference. The teletype machine reports clear weather at his destination. With his weather information complete, the navigator now plans his flight using sectional charts covering the route of his proposed course. On his first chart, he selects an easily recognized landmark whose exact location is known, in this case, a dam, as a starting point from which to calculate dead reckoning. He begins his log sheet or reckoning of the flight on which everything will be recorded. First, he fills in the pre-flight entries. These record the point of departure, date, type of aircraft, the mission, destination, and the names of pilot and navigator. Referring now to the sectional charts of the territory over which his course will run, the navigator prepares to plot his course. Using his dividers, he measures the distance from the nearest parallel of latitude shown on the sectional chart to the point of departure. Alby's latitude is 6 and 12 minutes north of the 31° 30 minute parallel, making its position 31° 36 1/2 minutes north. This reading is now logged. Now he measures the distance from the dam to the nearest meridian to get the longitude of his starting point. This is 8 minutes west of the 84° meridian. He records the reading. 84 degrees 8 minutes west, which completes the location readings on his point of departure. Since his destination is on an adjoining chart, he also takes latitude and longitude readings on the point of destination. Having determined the location of his points of departure and destination, the navigator plots these two points on a Mercer chart of the same latitude. Using the straight edge of his plotter, he connects the two points designating his course. He now measures the bearing of his course. Placing the edge of the plotter on the course and sliding it until the protractor center is over a meridian, he takes the course reading which is 25°. This course reading is recorded in the log book on the first line under true course. Now with his dividers, he prepares to measure the distance of the course. Midway of his course, he takes a unit of measurement from the latitude scale. He walks the dividers, the length of the course. He measures the remaining fraction making the total distance 214 nautical miles. This figure 214 is logged under distance to run. Located one quarter of the way between the 2°ree and 3°ree isogonic lines, Alby's magnetic variation is approximately 2 and 1/4° east as indicated on the sectional chart covering the first part of the course. On the chart covering the second half of the course and destination, he checks the variation at Greenville, South Carolina, and finds it to be 1/4 degree west. Taking the 2 and 1/4 degree east variation at Albany and the 1/4 degree west variation at Greenville, he finds that one degree west is the average variation for the entire course. Now to prepare for possible emergencies on route, he locates auxiliary landing fields along his course, finds their exact location, and prepares to plot them on his Mercer chart. Since there may be mountains, local magnetic fields, and other dangerous territory along his course, the navigator now checks his charts for such hazards. The final entry in the log under Mitro while he is still on the ground is for the wind. This is 20 knots from 220°. The word metro indicates the source as being the meteorological office. After completing his pre-flight data and before leaving operations, the navigator packs his briefcase, making certain that he has all necessary sectional charts, his Mercer Merkar chart, and his log book. His instrument kit must be checked to make certain that its equipment is complete. He makes certain that he has his computer. It will save him much time in working his problems on route. And he must be certain to have plenty of sharpened pencils with him. Without these allimportant tools of his trade, a navigator is as useless as a gunner without ammunition. Once in the airplane, the navigator must carefully check the seven instruments he will use in Dead Reckoning. These include the magnetic a periodic compass to indicate the heading of the aircraft, the drift meter which will indicate any wind drift during flight. The remote control gauge to the automatic pilot for frequent heading corrections. And on the navigation instrument panel, the airspeed indicator, the temperature gauge, the clock, and the altter. He sets the altimeter to correspond to the altitude of the field and is ready to work the problem. From the compass deviation card for this particular airplane, he notes that when flying a course of 25°, the deviation correction is minus4°. This deviation must be considered in later calculations. So he enters this minus4° and the time of entry in his log book. Having noted his previous entry regarding initial heading, he sets his periodic compass to agree with it, the navigator now gives the pilot his flight instructions, including a routine compass deviation check before starting the flight from Albany Dam. A constant air speed and altitude will be maintained throughout the flight. The airplane takes off at 8:00. This time of takeoff is entered in the log book. The initial heading at this time is also entered. When the predetermined altitude is reached, the navigator checks his compass by taking drift meter readings along a railway track or highway. If any deviation is noted, a comparison is made with the calibration shown on the compass card. If the card calibration differs as much as 2° from the navigator's computation, a recheck should be made by taking a second series of readings. Shortly the airplane is directly over the dam. The time is 8:20. The pilot engages the automatic pilot so that the navigator can control the direction of the flight by remote control. Otherwise, the navigator would instruct the pilot to make any changes in heading found necessary. After taking a drift reading, the navigator makes entries in his log book on the second line of the position of the time and drift. This correction is minus2° and is caused by a wind from the left. It requires a slight change in the heading of the airplane. This is accomplished by turning the remote control gauge as many degrees to the right or left as is required to set the airplane on its correct heading. Drift readings are taken at 5minute intervals. Frequent compass checks are also necessary. Each of these must be recorded in the log. At 8:35, it is noted that the drift has changed from minus2° to -4°. To correct the heading, the navigator adjusts the remote control gauge by turning it 2° left. The airplane is now on course. The true air speed of the airplane must now be determined so that the navigator can compute its location and ground speed. The indicated air speed is 140 mph. Checking the calibration card, the navigator finds that this gives a calibrated air speed of 125 knots. The air temperature reading is + 10° centigrade and the altitude is 7,000 ft. He adjusts the computer so that the air temperature plus 10° centigrade is aligned with the pressure altitude which is 7,000. The navigator finds the figure 125 on the computer's calibrated airspeed scale and directly above it the figure 141 which is true air speed in knots. To verify the course of flight, he turns to the reverse side and moves the slide until the center dot is on the true air speed 141. The true heading of 21° is now set under the true index arrow. Knowing his last drift was minus4, he finds the fourth line to the right of the center line. directly over this fourth line. He draws a line in this manner. This line now represents the course of flight. The navigator knows that drift to the right may be caused by a wind from the northwest or it may be caused by a southwest wind or any wind from the left. To find the direction and velocity of this wind, the navigator instructs the pilot to make a double drift, which will give the navigator this information. This involves turning the airplane to the right 45° for 2 minutes, then turning 90° left for 2 minutes and then returning on course. Therefore, at 8:40, the pilot relieves the automatic pilot and turns the airplane 45 degrees to the right. He holds this heading for 2 minutes. While on this first leg, the navigator notes that the drift is minus one°, indicating a general west wind. This figure is recorded in the log. to represent the first leg of the double drift on the computer. He turns the top of the card to the left 45° over the first line to the right of center. He now draws a line. This first line to the right represents the minus one degree drift noted while on the first leg of the double drift. The airplane is now turned 90° to the left for 2 minutes. The drift reading on this leg is found to be -6°. This also is recorded in the log book. Turning the computer card right 90° to represent the second leg of the double drift, he draws a line over the minus 6°. This drift of -6° was noted while on the second leg. After 2 minutes of this leg, the pilot turns right 45°, putting the airplane back on course. He then re-engages the automatic pilot. The navigator now must check his compass and make any necessary corrections on the remote control gauge. The data procured by the double drift process is now used on the computer. This results in a small triangle or point and is taken as the average drift reading. When the card is turned left 45° which now corresponds again to the original course, the center of the triangle which represents the end of the wind vector is over line 151. This is ground speed in knots. After turning the card so that the small triangle is directly under the center dot, he reads the distance from dot to triangle. This distance is 15, indicating a wind force of 15 knots. The wind direction found at the top of the indicator shows 253°. This information is recorded in the log. Because a routine report to the home base is required every 30 minutes, the navigator must compute his position ahead of time. While flying the two legs of a triangle in the double drift, one minute of oncourse flying time was lost. Because of the minute lost, computation will be based on 29 minutes instead of 30 minutes. A check on drift indicates that it still remains a minus4°. Now he enters in the log book 29 minutes for the time run on course. A distance of 73 mi. Distance to run 141. Time to run 56 minutes. and an estimated time of arrival at 9:46. He reports this information to the pilot. Now, in preparation for a report back to his base, the navigator measures with his dividers the distance to the point to be reached at the end of 30 minutes of flying, which time will be 8:50. He finds this point will be 32° 46 minutes north. and 83° 29 minutes west. After recording this in the log, the navigator switches his radio to command and contacts his base, reporting his time, position, and course. A check on the drift meter indicates a drift now of minus5°. After logging this, he adjusts his remote control gauge accordingly, correcting the airplane's heading. At 859, the pilot notes that the oil pressure is dropping in one engine. Using the computer, the navigator again checks the airplane's position to prepare for a possible emergency. From his computation, he marks his position and time and notes the locations of the nearest airports for a possible emergency landing. However, a few minutes later, the oil pressure returns to normal and the flight continues on schedule. At 0903, the ground is visible and a drift reading of minus3° is recorded. This requires an adjustment on the remote control gauge to correct the heading. The navigator now directs the pilot to make another double drift so that he can verify the ground speed. After completing the double drift and back on course with all computations made, he makes the necessary entries in the log. At this point, the navigator notices cumulus clouds which tend to make the air rub. This fact too is entered in the log under remarks. An efficient navigator always computes locations ahead. Accurate computations of his ground speed together with other factors of navigation and regular readings of instruments are essential. From these computations, the navigator advises the pilot that the estimated time of arrival will be 9:47. At 9:46, the destination is cited only 1 minute from the estimated time of arrival. The navigator who knows his job is the one who will get his airplane to any destination, including Berlin or Tokyo. [Music]