Advanced Pilot Training: TM 1-205 Air Navigation - Section X Navigation Flights

89. Relation of pilotage and elementary dead reckoning."Air pilotage is the method of conducting an aircraft from one point to another by observation of landmarks either previously known or recognized from a map. Although this sounds very simple, there are many chances for careless errors to cause the inexperienced pilot to get lost or to waste much time during a comparatively easy cross-country flight. The poor method of merely taking off and heading in the general direction of the destination, relying ,entirely upon excellent visibility and numerous landmarks is not good pilotage, although it will frequently give fair results. Pilotage .,and dead reckoning are closely related in actual practice, and usually on a flight made mainly with pilotage methods there are many .,chances to use dead reckoning methods to good advantage for short periods of time.

b. Theoretically, on a pilotage flight, it is not necessary to have a magnetic compass. Most experienced pilots, however, would not attempt to make a cross-country flight without a reliable compass. Even on a flight where there is a main river or shore line to follow, there is some chance of having to leave the easily followed course due to weather or some other cause. In such a case, especially if the visibility is poor, the magnetic compass is indispensable.

c. As the cross-country experience of a pilot is increased, some of the steps which follow may be eliminated. The beginner should remernber that he develops his ability during flights made in good weather and on easily followed courses. Then later on if he is faced with a difficult and possibly unexpected situation he will have the correct background and the habit of using the proper methods. This will enable him to know his exact position at all times and to reach his destination even under adverse conditions.

90. Preparation of maps.-Many maps used by Air Corps personnel have already been prepared for the most used flight paths, When this has been done the map will show, as straight lines, the i courses between the various turning points. These lines will be marked off at 20-mile intervals for an easily used distance scale. The magnetic course will be indicated by its numerical value for each direction along the course lines.

a. Marking for cross-country use.-If it is necessary to use a map which has not been marked for cross-country use, prepare it as follows:

(1) Draw a straight line between the starting point and the destination. (If desired to fly from A to D by way of B and C then draw AB, BC, and DC.) Examine the paths shown by these course lines. From knowledge of the terrain or from information shown on the map, decide whether or not it would be best to follow these straight courses. If, on any leg, a slightly longer distance would enable the pilot to avoid flying over large bodies of water, mountains, or other hazardous terrain, then divide this leg into two or more sections so that the path outlined will be safer to use.

(2) When the course lines are completed, measure each leg for distance and then mark off 10- or 20-mile intervals on the course line. Write in, on the map, each 50- and 100-mile numerical value.

(3) Then on those legs which extend over only 3° or 4° of longitude, or less, measure the course line with a protractor. Use the meridian which is nearest the middle of the leg. Correct the protractor reading for variation and print the value for the magnetic course on the map. On a longer leg of 6° or 8° of longitude, first divide the leg in half and then obtain the magnetic course for each half by using the variation nearest the middle of each section.

b. Folding aeronautical charts.- (1) For laying out routes before taking off, for all detailed studies of a region, and for all general use, a flat chart, free from folds and wrinkles, is very desirable. During actual flight, even in the larger transport planes, lack of space usually prevents the use of an unfolded chart. As a result, many methods of folding the charts have been devised, while those flying regular routes have made up strip charts or books from the published charts. In order to avoid the handling of numerous charts on all navigational flights, even short ones, both sectional and regional charts have been designed to cover fairly large areas. Nevertheless charts of both series will be found very convenient for use in the air when properly folded. It is recommended that the charts be folded once, back to back, along the line AB (fig. 50), then in four or six "accordion folds" in the other direction, along the vertical broken lines indicated in the figure. In this way the entire chart may be consulted merely by turning over the accordion folds.

(2) Strip charts are very convenient for those flying frequently over the same route; however, as already suggested, they cannot fully satisfy the need even for this type of flying. A pilot may be compelled to leave the charted airway because of adverse weather conditions or other reasons and will find himself over unfamiliar territory with no chart of the ground below. If a strip chart or book is prepared showing only the region immediately adjacent to the route, complete sectional charts showing a wider area, folded for most convenient reference in case of need, should also be carried.

(3) Some very ingenious folds and route books have been devised, by means of which the entire route, or even whole charts, can be followed from point to point by the flip of a page; however, if such folds are made by pasting portions of the chart together, they cannot be considered satisfactory for all purposes, since the chart cannot be spread flat again for the plotting of new courses, etc. Folds of this sort should by all means be supplemented by a flat chart or one so folded that it may again be opened out flat.

(4) If a strip chart is desired, the chart can be folded as a strip without destroying or cutting away any part of it. For example, if it is desired to make a strip chart covering the route CD (flg. 51), fold the chart so as to leave the route in the center of a strip 10 or 12 inches wide; then fold the strip in the accordion fold illustrated in figure 50. By this method the folded-back portions of the chart are still available if they should be needed.

91. Other preflight preparation.-a. Although the Form 1 always has a pencil attached, it is far more convenient to use a separate pencil, with eraser, which may be carried in a holder or a pocket. A writing pad consisting of a pad placed on a small piece of plywood (hold to the leg, above the knee, by rubber bands) has been successfully used and endorsed by pilots of small airplanes. Some pilots prefer to use paper clips to attach their extra paper directly to the map.

1). After the necessary cross-country request has been approved, and the maps prepared, the equipment, such as flares for night flying, cross-country tool kit, stakes and covers, smoke candles, etc., should be placed in the airplane.

c. Master charts in the operations office should be checked to insure that all pertinent data are also on the charts to be used on the flight.

d. The Pilots' Information File and Notices to Pilots should be checked for recent additions.

92. Simple log sheet.-It is a good Policy for the pilot to study his map before he goes into the air for a navigation flight. One excellent method is to make a list of all possible check points along the route, with the distance from the starting point and the distance between consecutive points listed against them, somewhat in the manner of road logs for automobile touring. The time should be computed to each check point, using the average air speed. The time should be listed as take-off time plus the number of minutes computed. This time can then be checked against the actual time in flight to determine whether the wind is hindering or helping on the flight. During the flight the pilot can refer to this list and check the points off as he goes along. An example of such a simple log is shown

in figure 52. Assume that easily recognized check points are located as listed above and distances from the starting point are as shown. The planned air speed is to be 140 m. p. h. Using the D-3 computer (par. 55), the E. T. A. (estimated time of arrival) of the first three or four check points is recorded. (All may be computed, if desired.) This simple log may be carried (as stated in par. 91) clipped along the edge of the map or on a separate pad of some sort.

93. Flight plan, clearance, weather.-Before take-off, the pilot must procure a clearance from the operations office. This clearance includes a flight plan for the trip and certain other pertinent data. It also includes a space for the weather report, and this part is retained by the pilot for use during the flight.

94. Handbooks and XC envelope.-Before take-off, the pilot must insure that the airplane carries the two Technical Orders-Radio Facility Charts and Radio Data and Aids to Airways Flying-and also a cross-country envelope. These Technical Orders were discussed in paragraph 87. The cross-country envelope contains a number of blank forms and certain regulations and orders. These are listed, together with a description of the use of the envelope, in A. C. Cir. 15-9.

95. Radio check on ground.-Before the actual take-off, the pilot (of radio equipped airplanes) will call the control tower and complete a radio check-in. He will receive the correct time, data relative to altimeter setting, wind velocity, and take-off instructions, during the check-in.

96. Initial procedure.-a. The pilot gains the altitude which he is to use, before starting on the desired course. He then passes directly over his starting point or some definite check point nearby (listed as "Start" on his log) and notes the exact time he passes over it, writing this time on the log. If it is undesirable to climb to the cruising altitude, before starting, it may be gained on the way. Note that this will mean a slower ground speed during the period of climbing. In any event he writes down on the log sheet the exact time of departure.

b. The pilot figures out his desired compass course as soon as he sees the compass correction card. If wind data are not available he estimates the drift correction. (Usually the correction by the inexperienced pilot will be too large.) This correction, applied by heading the airplane into the wind the required number of degrees, is applied to the compass course and thus the original compass heading is obtained. He uses this heading and watches for the first check point, meanwhile holding the map so that it is properly oriented in relation to the ground. As he looks at the chart, the course line he intends to follow is held parallel to the longitudinal axis of the airplane, and his desired course as shown on the chart is along this line from bottom to top as he looks at it. Held in this position all of the printed matter may be upside down, but it is the correct position for the map.

c. The method of steering a range (par. 59) may be used at this time in conjunction with others.

d. During the first few minutes the pilot checks the map against the ground repeatedly. He also glances frequently at the compass to see that a constant heading is maintained. He may use the directional gyro set to zero, and this is usually easier to keep centered than the magnetic compass.

e. Knowing the E. T. A. of the first real check point, the pilot starts looking for it a little ahead of time. When he passes over it, he has a check on his ground speed and also on his estimate of the drift. If he passes very far to the right or left of the check point, he should make a correction in his heading. This correction is difficult to judge at first but becomes easy after a few flights. One easily remembered relationship is that a change of 1° of heading will make about I mile difference to right or left, in 60 miles of travel, or 2° will make a mile of difference in 30 miles, and 4° will change 1 mile to the side in 15 miles forward.

f. If the course is such that a radio range may be used, the proper station is tuned in and the compass heading checked against the radio signals.

g. Usually railroads and highways are excellent check objects to use at the start of and throughout the trip. Rivers, lakes, quarries, water towers, race tracks, adjacent towns, etc., are all very useful in aiding the pilot to maintain the, proper position and direction.

h. It cannot be overemphasized that the time to start checking the heading, and also the map with the objects on the ground, is immediately after the start. If they both indicate that the desired course is being made good, there is hardly a chance of starting in the wrong direction even without the use of radio.

97. Written record vs. memory~One of the most serious of the mistakes an inexperienced pilot may make is that of trying to remember some of the things he should write. The rule is: write, do not try to remember. Even if the course seems so easy that a log seems unnecessary, write the time of passing each check point opposite the position of the place on the map. It is well to have an eraser handy, in case the map is already marked with the check times of another pilot.

98. Altitude; traffic rules.-The cross-country pilot will keep in mind that there is a specified altitude to use, depending on the course; that there are certain traffic rules and safety precautions to be observed; that certain radio reports may be required; and that the original flight plan must be followed out unless the change is immediately reported. These are but a few of the things he must keep in mind, in addition to his duty as pilot-navigator.

99. Time and ground speed.-a. Method.-With the use of the simple log, already described, the pilot may easily keep track of his time and ground speed at all check points. As each check point is passed and identified, the time will be written down and the estimate of the ground speed revised. The use of the D-3 computer makes the figuring of ground speed the work of but a moment. A good check on ground speed enables the pilot to know his position at all times and serves to differentiate between two check points which may have points in common. Knowing his ground speed and the distance, he will know which check point it is. The ground speed may change considerably if the airplane passes through a wind shift.

b. Position for noting time.-The pilot waits until the check point is directly underneath the airplane or directly abeam before noting the time. For accuracy, each of his observations is done in the same way, and the results are then uniform.

c. Three things to check.-By constantly checking the following three items the pilot will insure his flight against errors involving uncertainty as to position. Knowing position and direction of travel he cannot become lost. He checks

(1) The compass heading to see that the airplane is kept on the correct and straight course.

(2) The time and distance flown, from which he estimates his ground speed.

(3) His position, by means of check points on the ground, ground speed, elapsed time, and radio. The time and ground speed will help identify check points having similar features.

100. Use of radio.-The use of the radio is not emphasized in this section as the pilot may have to navigate at times without its use. He will be able to do so by following the methods outlined. The use of radio greatly simplifies air navigation in the United States, but there is always a chance that it may fail. By training himself to navigate without depending too much on the radio, the pilot insures himself against becoming confused if it ceases to operate. By using proper methods in good weather and not depending on one method alone, he develops his technique to the point where the failure of one or more instruments or the radio will not cause him to become lost.

101. Dead reckoning between check points,-After the pilot determines the compass beading which keeps him on course, he may fly for periods across terrain which offers no good reference points and still arrive very close to his next check point. Frequently a case will come up when he may insure his arrival by going a slightly longer distance. In the following examples, assume that the visibility has been cut down by the presence of dust.

a. Example 1.-A pilot, en route from A to C (fig. 53) -navigates easily from A to B and then comes to a stretch from B to C which offers no check points. He -notes that a railroad passes through D, C, and E. Knowing the compass heading which he followed from A to B, the pilot swings several degrees to the left and follows the course BF. When he comes to the railroad he turns to the right and quickly arrives at C. He also uses the time and ground speed for the distance BF as an additional check. This method enables the pilot to know for sure which way to turn when he reaches the railroad. In conditions of poor visibility he might otherwise have to guess, if he did not arrive within sight of C.

b. Example 2-Figure 54 illustrates another example, where the railroad (or river, etc.) is approximately at right angles to the course. In this case the pilot swings to either side (right, shown) and then knows which way to turn to reach the point C.

102. If position becomes uncertain~A pilot who is flying over a strange course may, during periods of dead reckoning, become uncertain as to his exact position. There is a definite distinction between being uncertain as to position and being lost.

a. Example.- (1) If the pilot knows his exact place and time of departure and, after checking several check points, finds that the next point fails to come in view at the proper time, his position is uncertain, but he is not lost. He has definite information on all the work that he has done thus far and can establish an approximate position. On the other hand, if he does not know his time of departure and has not checked his ground speed against the check points, he will be lost when his check point fails to come in view. This is true because he will have no data to use in establishing an approximate position. With no written record to use, his memory will soon make him doubt some of his previous check points.

(2) To avoid remaining uncertain as to position, the pilot knows exactly what he has done up to the point where his position becomes uncertain. Assuming that he has written the data as to startingtime, kept an accurate compass heading, and checked both direction and ground speed by means of check points, he has a record of his flight up to the last recognized check point. Knowing that the flight had progressed satisfactorily up to that time, the first question for him to consider is the missing check point itself. Is it a feature that he could easily miss, or is it possible that the map is in error? A careful check of the time and the ground speed will tell him whether he has gone the proper distance from the last check point. It may be that he has passed the point without seeing it, due to poor visibility. His progress up to that time will give an idea as to which side he may have passed it on.

(3) The best plan to follow is for the pilot to look ahead on the map and see what possible check points lie ahead, both on the course and to either side of the course. The time needed to reach these points should be computed from the last recognized check point, and the airplane should be held on the proper compass heading. It is seldom that this procedure will not apply. When he reaches and identifies the new object, it is important that he identify his exact location, particularly when it is a railroad. He should not go on unless he is sure of his location. If there is no other way, he may try to identify the name of the nearest town from a sign on a water tank or on the roof of a building and then take a new departure from that point. It is not unusual for him to fly as much as half an hour without a definite check point, but this should cause no trouble if the flight has been started properly and the compass heading flown accurately.

b. Each flight different.- (1) Each navigation flight is an individual problem. The country passed over and the weather cause variations in procedure. For example, in good weather the pilot may be able to check on a series of towns along a railroad 5 or 10 miles to the side, but when the visibility is poor he cannot see them and will have to depend upon points he passes over or close to. When the visibility is poor the available check points are reduced in number, and it is very important that those which are seen are used to the utmost. For this reason the pilot should practice close adherence to the principles stated so that he will be familiar with the procedure when the visibility is limited. It is quite easy to fly a navigation problem when the visibility is good, but the pilot does not get the benefit from the practice if he does not check accurately as he goes along. Then, when bad weather arrives, the points he can see are limited and he does not have confidence in his ability to navigate with them. This is particularly true of night flights as there are fewer check points that can be used unless the lighted airways are followed.

(2) Repeating some of the above points, if the pilot has not kept a close check on the time and ground speed and has not flown an accurate compass heading he is lost when a check point fails to appear. He does not know exactly how far he has gone, and he does not know the direction closely enough to establish a position. The best that he can do is to proceed with the same compass heading that he has been flying and as soon as he comes to a railroad, town, or other object locate himself before he leaves it. The essential point is that he should know what he has done previously. If he has flown an accurate compass heading and has properly checked the time, he is able to determine quite closely where he should be. On the other hand, if he has wandered over the country, using several different compass headings, and has failed to keep track of the time and ground speed, he has nothing on which to base an estimate of position.

c. Lost.-In the event the pilot becomes lost and is unable, using all available methods, to identify any check point, he will proceed as follows:

(1) General.-From an examination of his map, he will try to decide what area he is in. He will search the map f or some important river, railroad, highway, or other prominent feature which may be reached and followed. If sufficient gasoline and daylight are available and the weather is suitable, he will choose the compass heading which will be most likely to allow him to reach such a feature. He will start on this heading and maintain it unless, for reasons of safety or the discovery of a check point, he decides to change. When he arrives at a "position line" he will follow it until he can identify his position, turning in the direction most likely to bring him to an airport.

(2) Important rules when lost.-As a rule, a person becomes lost only through extreme carelessness. Having made mistakes in getting lost, the pilot may still redeem himself by using good judgment afterward. His actions should be governed by the word "safety" as applied to available f uel supply, daylight time remaining, conditions of weather, terrain beneath airplane, terrain to be flown over if he takes the best compass heading available, and so on. For such a pilot, some things to do and some things to avoid are listed below:

(a) With good weather, plenty of gasoline, and plenty of daylight left, follow instructions in (1) above. The only exception to this rule might be when a large smooth, hard, field is found; so good that there is no doubt about being able to make a safe landing, and located near a habitation, or to persons who will be able to tell the pilot his location.

(b) If the gasoline supply is low, it is imperative that the best field available be located immediately and that a landing be made in it while there is sufficient gasoline to "go around again" if necessary. Nothing may be said here which will determine for the pilot when the "best available field" is still not good enough. Needless to say, if there is no place to land, the remaining fuel will be used to obtain or maintain an altitude safe for parachute use, while the search continues for a suitable field.

(c) The approach of darkness may make a landing necessary. The pilot will have to decide this, but he must not wait until it is too dark if he does decide to land. The type of airplane, its equipment, the amount of experience of the pilot, and the availability of a landing area are all factors affecting this decision.

(d) The weather may influence the choice of whether to land or to continue on the best compass heading. The availability of a suitable landing area is also an important item in this decision.

(e) The terrain beneath the airplane is one of the most important things to consider when choosing the best method of insuring the safety of personnel and equipment. All possible conditions cannot be visualized in advance, and so no set rule can be given. If the pilot is sure that he can make a safe landing and is very doubtful about some of the other factors, he may be better off if he lands. On the other hand, there is no advantage gained in attempting a landing in an unknown field if a flight can easily be made to an established airport.

When flying along the regular airways, using the radio ranges, there is no danger of the pilot becoming lost. On flights off the airways, reception of the nearest radio ranges can usually be obtained. Every attempt should be made to utilize the radio for maintaining proper orientation as outlined in section VIII. The method used for quadrant identification (fig. 44) is often valuable for use even when the pilot is not following the airways.

d. Forced landing.-(1) In the event that the pilot makes a forced landing due to impending darkness, lack of fuel, bad weather, or for any other unforeseen reason, he will send the appropriate messages to his station of departure and the station departed for. Information concerning these messages is included in the material in the flight envelope.

(2) After a forced landing has been made, no attempt will be made to fly the airplane from the field landed in until after a thorough examination of the proposed take-off strip is made, assuming the airplane to have been undamaged in the landing. This will determine that the space for take-off is suitable from the standpoint of

(a) Length of run.-Consider airplane load, altitude, hardness of surface, etc.

(b) Condition of field.-Consider presence of ditches, holes, soft spots, crops or growth, etc.

(c) Obstructions.-Consider how high and how near obstructions are in relation to known performance of airplane.

(d) Fuel obtained.-If fuel has been added, consider whether it has an octane rating sufficiently high to enable full power to be used for the take-off.

(3) If a doubt arises as to the advisability of attempting to take off again after a forced landing, send in a request asking that a more experienced pilot be sent out to take charge of the situation.

103. Cloud shadows and smoke columns.-Any aid for the pilot which helps him judge the wind velocity is helpful. At times the surface wind may be judged from the appearance of smoke columns, or from windmills, or other objects on the ground. However, the wind velocity at the surface may be quite different from that at the altitude of the airplane. During flights when there are broken clouds at an altitude near that of the airplane, it is sometimes possible to see the shadows of the clouds on the ground and to judge the direction and speed of the wind in this manner. Such estimates of the wind indicate more accurately the actual wind affecting the airplane than do observations of the effect of surface winds.

104. Return trip.-After a successful flight to his destination, the inexperienced pilot may have trouble following the opposite course on the return trip.

a. The flight back should be considered a separate problem, and the procedure should be the same as when he left the home airdrome. The magnetic course back will be 180° different from that flown out since no allowance is made in the course angle for the wind. The drift angle will be the same number of degrees but of opposite sign as the drift angle out unless the wind has changed. The drift angle is always applied into the wind and can be allowed for at the start unless it is obvious that the wind has changed. Since the drift is laid off into the wind in each case, it is obvious that the heading out and the heading back will not differ by 1801, when an allowance must be made for the wind.

b. A factor which often causes trouble on the return trip is the appearance of check points. The flight back is usually made with the sun in a different position than during the flight out. This changes the aspect of the check points as seen from a distance because the shadows are different. This should cause no difficulty if the pilot waits until the check points are directly to one side or underneath before he checks on them. It sometimes makes the country appear to be different as he approaches it, so that he may think that he is off his track when in reality he is not. Always depend upon points in the immediate vicinity for accurate checks.