Navigation: Pilotage, Dead Reckoning, VOR, GPS

Pilotage is navigation by landmarks that the pilot sees and compares against the chart. Dead reckoning is navigation by computed heading, speed, and time from a known starting point. The Pilot's Handbook names the methods: "pilotage—navigating by reference to visible landmarks, dead reckoning—computations of direction and distance from a known position, and radio navigation—by use of radio aids" 1.

The two methods together

On a VFR cross-country, the pilot predicts position by dead reckoning and confirms it by pilotage. The handbook: "Dead reckoning is navigation solely by means of computations based on time, airspeed, distance, and direction. The products derived from these variables, when adjusted by wind speed and velocity, are heading and GS. The predicted heading takes the aircraft along the intended path and the GS establishes the time to arrive at each checkpoint and the destination" 2. The handbook adds the correction: "The heading and GS, as calculated, is constantly monitored and corrected by pilotage as observed from checkpoints" 2.

Neither method alone is a plan. An airplane flown on a computed heading with no checkpoints drifts with any wind that the forecast did not predict. A pilot who flies by landmarks with no computed heading only searches for the next familiar landmark.

The required foundation

The regulation requires training in charts, pilotage, and dead reckoning. A student training for cross-country flight must log "Use of aeronautical charts for VFR navigation using pilotage and dead reckoning with the aid of a magnetic compass" 3. The rule names no receiver. Electronic navigation adds to that foundation and does not replace it. When the receiver fails, the pilot has only that foundation. The pilot of N9515A had no paper chart and no working receiver.

The pilot measures true course with a plotter against a meridian. The handbook: "Because meridians converge toward the poles, course measurement should be taken at a meridian near the midpoint of the course rather than at the point of departure. The course measured on the chart is known as the true course (TC)" 4. The plotter's protractor rests on the meridian, with its straight edge on the course line. The pilot reads the angle from true north.

Variation

Variation is the angle between true north and magnetic north at the airplane's location. The handbook: "Variation is the angle between TN and magnetic north (MN). It is expressed as east variation or west variation depending upon whether MN is to the east or west of TN" 5. The chart shows it as "broken magenta lines called isogonic lines that connect points of equal magnetic variation" 5. On the west coast the compass points east of true north, so the variation is east.

The mnemonic is "East is least, west is best." To convert true to magnetic, subtract easterly variation and add westerly variation. The handbook's worked example shows the arithmetic: a variation of "6.30° E (rounded to 7° E), which means it should be subtracted from the TH, giving an MH of 21°" 6. The handbook's 6.30 is 6 degrees and 30 minutes, which rounds to 7.

The heading chain

The chain from the chart to the compass has three corrections. The handbook's method: "after the TC is measured, and wind correction applied resulting in a TH, the sequence TH ± variation (V) = magnetic heading (MH) ± deviation (D) = compass heading (CH) is followed to arrive at compass heading" 6. The three steps are:

• true course, plus or minus the wind correction angle, gives true heading
• true heading, plus or minus variation, gives magnetic heading
• magnetic heading, plus or minus deviation from the compass card, gives compass heading.

The handbook's example runs the chain in four steps:

• a true course of 31 degrees
• a wind correction of 3 degrees left, for a true heading of 28
• a variation of 7 degrees east, for a magnetic heading of 21
• a deviation of plus 2, for a compass heading of 23 6.

The wind correction angle

The pilot points the nose into the wind by the wind correction angle to hold the track on the course line. The handbook: "if the wind is from the left, the correction is made by pointing the aircraft to the left a certain number of degrees, therefore correcting for wind drift. This is the wind correction angle (WCA) and is expressed in terms of degrees right or left of the TC" 6. The angle is a prediction from the forecast wind. The pilot tests the prediction at each checkpoint.

Contour lines and shaded relief show the terrain. The Chart Users' Guide: "Contour lines join points of equal elevation. On Sectionals, basic contours are spaced at 500' intervals." The guide adds: "Widely spaced contours represent gentle slopes, while closely spaced contours represent steep slopes" 7. The relief is shaded "as if light is coming from the northwest" 7.

Closely spaced contours show a steep slope, such as a ridge. A ridge is a checkpoint from the side and an obstacle from ahead.

A good checkpoint

A good checkpoint has three qualities:

• it is unique
• it is visible from cruise altitude
• it is on or near the course line.

The handbook: "These should be easy-to-locate points, such as large towns, large lakes and rivers, or combinations of recognizable points, such as towns with an airport, towns with a network of highways, and railroads entering and departing" 8. A small circle on the chart "may turn out to be only a half-dozen houses" 8. A lake among lakes is not unique. A tower in flat country is unique and visible from far off.

Line features: gates and brackets

Line features have two uses. A river, highway, or railroad that crosses the course is a timing gate. The airplane crosses it at a planned time, and the actual time shows whether the groundspeed is as planned. A line feature parallel to the course confirms the track and bounds the drift.

The handbook: "select features that make useful boundaries or brackets on each side of the course, such as highways, rivers, railroads, and mountains. A pilot can keep from drifting too far off course by referring to and not crossing the selected brackets" 9. A course drawn between a highway and a river ten miles apart has a drift limit on each side.

Spacing

The pilot spaces checkpoints so that groundspeed checks come at a regular interval. In the Warrior, checkpoints ten to fifteen miles apart give a check each six to nine minutes. That interval is frequent enough to detect a wind change. It is also long enough to leave time to fly the airplane. The handbook: "Never place complete reliance on any single checkpoint. Choose ample checkpoints. If one is missed, look for the next one while maintaining the heading" 9.

The first checkpoint

The first checkpoint belongs after the top of climb. A groundspeed check from the runway to a point ten miles out measures the climb. The climb is slower over the ground and at a different airspeed. A groundspeed check between the first two cruise checkpoints measures cruise. That number is the basis for the rest of the nav log. The handbook's caution: "ground speed during climb is less than during cruise flight at the same airspeed" 10.

True airspeed is calibrated airspeed corrected for density altitude. The Pilot's Handbook gives an approximation: "Simply add 2 percent to the CAS for each 1,000 feet of altitude. The TAS is the speed that is used for flight planning and is used when filing a flight plan" 11. At 5,000 feet, 100 knots calibrated is about 110 true. The flight computer computes it exactly from pressure altitude and temperature.

The manual's cruise table

Planning true airspeed comes from the manual. The Warrior's cruise chart plots true airspeed against density altitude for 55, 65, and 75 percent power, leaned, at gross weight. A note on the chart says to "SUBTRACT 2 MPH IF WHEEL FAIRINGS ARE NOT INSTALLED" 12. The range chart beside it gives the fuel: "75% POWER 9.2 GPH. 65% POWER 8.0 GPH. 55% POWER 6.7 GPH" 13.

The power choice is a trade between speed and fuel. Seventy-five percent is faster and burns 9.2 gallons an hour. Fifty-five percent is slower and burns 6.7. The planner picks a row, reads the true airspeed and the burn, and writes both on the nav log.

The wind side of the computer

The wind side of the flight computer solves the wind triangle. The handbook: "If there is no wind, the aircraft's ground track is the same as the heading and the GS is the same as the true airspeed. This condition rarely exists. A wind triangle, the pilot's version of vector analysis, is the basis of dead reckoning" 14. The inputs are the forecast wind, the true airspeed, and the true course. The outputs are the wind correction angle and the groundspeed. The handbook's example: "Using a wind of 360° at 10 knots, it is determined the WCA is 3° left" 14.

True winds and magnetic winds

The winds aloft forecast is in degrees true. So is the written METAR. The Aviation Weather Handbook: "Forecast winds aloft will be provided in knots and tens of degrees and referenced to true north" 15. Voice broadcasts differ: "Wind direction is reported relative to magnetic north in ATIS as well as ASOS and AWOS radio (voice) broadcasts. Otherwise reported relative to true north" 15.

The computer solves the true wind against the true course and gives a true heading. The pilot then converts the true heading through the chain. A magnetic wind from the tower is for the runway. The runway heading is magnetic too.

Actual groundspeed is the distance between two checkpoints divided by the time between them. Twelve miles in eight minutes is 90 knots. The handbook's relation: "Estimated time en route (ETE)—total distance divided by GS" 16. The same relation inverted gives the groundspeed the airplane has: the distance divided by the measured time. The nav log has a column for the estimate and a column for the actual, and the pilot fills the second at each checkpoint.

Slower than planned: fuel first

After a groundspeed slower than planned, the pilot recomputes destination fuel first and the schedule second. Ninety knots on a leg planned at 100 is 11 percent more time and 11 percent more fuel on each remaining leg. The handbook: "You should always plan to be on the surface before any of the following occur: Your flight time exceeds the amount of flight time you calculated for the consumption of your preflight fuel amount; Your fuel gauge indicates low fuel level" 10. The schedule can change. The fuel limit cannot.

Unplanned consumption, from a headwind, a rich mixture, or a deviation around weather, appears in the checkpoint fuel log. The response is the fuel decision point from Module 2-1.

Off course: re-intercept, then a new heading

The pilot corrects an off-course airplane in two steps. The first step is a visual re-intercept. The pilot turns toward the course line and flies back to it. A checkpoint or a bracket shows when the airplane reaches the line. The second step is a revised heading that holds the track.

The handbook's VOR advice uses the same method: "If the aircraft drifts, fly a heading to re-intercept the course then apply a correction to compensate for wind drift" 17. A pilot who re-intercepts and returns to the old heading re-intercepts again ten minutes later.

The wind is not as forecast

A persistent disagreement between the planned heading and the heading that holds the track means the wind is not as forecast. The correction is to update the wind correction angle, not to re-intercept again and again. Five degrees of extra crab that holds the track for two checkpoints is the new plan. The groundspeed measured over those checkpoints is the new groundspeed. The handbook's warning about the needle applies to the course line too: "Just turning toward the needle will cause overshooting the radial and flying an S turn to the left and right of course" 17.

A VOR broadcasts 360 radials, referenced to magnetic north. The handbook: "The course or radials projected from the station are referenced to MN. Therefore, a radial is defined as a line of magnetic bearing extending outward from the VOR station. Radials are identified by numbers beginning with 001, which is 1° east of MN and progress in sequence through all the degrees of a circle until reaching 360" 18. A radial always extends from the station. The 090 radial extends east from the VOR. An airplane on that radial that flies toward the station flies a course of 270.

Identify it first

The pilot identifies a VOR by its Morse code before use. The AIM: "The only positive method of identifying a VOR is by its Morse Code identification or by the recorded automatic voice identification which is always indicated by use of the word 'VOR' following the range's name" 19. A missing identifier means the station is unusable. The handbook: "If the VOR is out of service for maintenance, the coded identification is removed and not transmitted. This serves to alert pilots that this station should not be used for navigation" 20. A needle that centers on an unidentified frequency does not confirm which station the receiver has.

The OBS, the needle, and the flag

With a course set in the OBS, the needle shows displacement from that course. The flag shows whether the course leads to or from the station. The handbook: "By centering the needle, the course selector indicates either the course 'FROM' the station or the course 'TO' the station. If the flag displays a 'TO,' the course shown on the course selector must be flown to the station. If 'FROM' is displayed and the course shown is followed, the aircraft is flown away from the station" 21. Each dot of the CDI is about 2 degrees of course displacement, from the handbook's figure label "Approximately 2 degrees in the VOR mode" 21. Full scale is 10 degrees off the course.

Reverse sensing

The needle senses correctly only when the selected course roughly matches the direction of flight. The handbook: "When flying 'TO' a station, always fly the selected course with a 'TO' indication. When flying 'FROM' a station, always fly the selected course with a 'FROM' indication. If this is not done, the action of the course deviation needle is reversed" 17. When the airplane flies the reciprocal of the selected course, the needle points away from the course. A pilot who turns toward the needle flies farther off course. The correction is to set the course that matches the heading.

One VOR: the radial

To fix position with one VOR, center the needle with a FROM indication. The course window then reads the radial the airplane is on. The handbook: "The course selector is an azimuth dial that can be rotated to select a desired radial or to determine the radial over which the aircraft is flying" 21. One radial is a line, not a point. The handbook: "A VOR radial alone merely gives line of position information" 22.

Two VORs: the cross-fix

Radials from two VORs cross at one place. Two lines of position give a point, without any landmark. The handbook's lost procedure: "If the aircraft has a navigational radio, such as a VOR or ADF receiver, it can be possible to determine position by plotting an azimuth from two or more navigational facilities" 23. The With one receiver, the pilot takes the two radials in sequence:

• tune and identify the first station
• center the needle with FROM and draw the line
• repeat both steps for the second station.

The airplane is where the lines cross.

Line of sight

VOR reception is line of sight. The handbook: "Because the equipment is VHF, the signals transmitted are subject to line-of-sight restrictions. Therefore, its range varies in direct proportion to the altitude of receiving equipment. Generally, the reception range of the signals at an altitude of 1,000 feet above ground level (AGL) is about 40 to 45 miles. This distance increases with altitude" 18. Terrain blocks the signal at low altitude. A flag in a valley does not mean a broken receiver. It means a hill between the airplane and the station.

VOR accuracy checks are an IFR rule, not a VFR one. Section 91.171 requires, for IFR, a check within 30 days with a test signal where "the maximum permissible indicated bearing error is plus or minus 4 degrees" 24. The handbook: "VOR accuracy checks are not a regulatory requirement for VFR flight. However, to assure accuracy of the equipment, these checks should be accomplished quite frequently" 25.

The VOT check is free. The AIM: "tune in the VOT frequency on your VOR receiver. With the Course Deviation Indicator (CDI) centered, the omni-bearing selector should read 0 degrees with the to/from indication showing 'from' or the omni-bearing selector should read 180 degrees with the to/from indication showing 'to'" 26. A receiver that reads 8 degrees off on the VOT reads 8 degrees off on the cross-fix. The VOT check shows the pilot that error before flight.

Slant range

DME distance is slant range, the straight line from the airplane to the station. The handbook: "Slant range distance is the direct distance between the aircraft and the VORTAC and is therefore affected by aircraft altitude. (Station passage directly over a VORTAC from an altitude of 6,076 feet AGL would show approximately 1.0 NM on the DME.)" 22. Over the station, the readout shows the altitude in miles, not zero.

The network is shrinking

The FAA removes selected VORs from service to reach a minimum operational network. The AIM: "As flight procedures and route structure based on VORs are gradually being replaced with Performance-Based Navigation (PBN) procedures, the FAA is removing selected VORs from service" 27. A charted VOR is not proof of a working VOR. NOTAMs list the stations out of service. The planner checks them before the nav log depends on a station 28.

GPS position comes from satellite ranging. The AIM: "A minimum of four satellites is necessary for receivers to establish an accurate three-dimensional position" 29. The receiver measures its distance from each satellite and solves for its position.

RAIM

RAIM is the receiver's integrity self-check. The AIM: "RAIM is the capability of a GPS receiver to perform integrity monitoring on itself by ensuring available satellite signals meet the integrity requirements for a given phase of flight. Without RAIM, the pilot has no assurance of the GPS position integrity" 30. The check needs spare satellites: "RAIM requires a minimum of 5 satellites, or 4 satellites and barometric altimeter input (baro-aiding), to detect an integrity anomaly," and to exclude the bad one, receivers with fault detection and exclusion "require 6 satellites or 5 satellites with baro-aiding" 30. The count is:

• four satellites for a three-dimensional fix
• a fifth to detect that one signal is wrong
• a sixth to isolate and exclude it
• the barometric altimeter can replace one of them.

The RAIM annunciation

A RAIM-loss or integrity annunciation in flight means the position is unverified. The AIM gives two messages: "The first type of message indicates that there are not enough satellites available to provide RAIM integrity monitoring. The GPS navigation solution may be acceptable, but the integrity of the solution cannot be determined. The second type indicates that the RAIM integrity monitor has detected a potential error" 30. Either message has one answer: cross-check the position against the chart, a VOR, or the checkpoints, or revert to pilotage and dead reckoning. The receiver reports that it cannot verify its position. The pilot must verify the position by other means.

Know before takeoff

IFR GPS operations require an integrity prediction before flight. The AIM has pilots use "a manufacturer-supplied RAIM prediction tool, or using the Service Availability Prediction Tool (SAPT) on the FAA en route and terminal RAIM prediction website," and adds that "RAIM availability should always be checked" 31. The VFR pilot can make the same check. Before takeoff, the pilot checks three things:

• the GPS NOTAMs
• the receiver's status page
• the database date.

The database

No regulation requires a current GPS database for VFR. The AIM: "there is no requirement for databases to be updated for VFR navigation. It is not recommended to use a moving map with an outdated database in and around critical airspace" 32. The handbook describes the hazard: "Numerous pilots have ventured into airspace they were trying to avoid by using an outdated database. If there is not a current database in the receiver, disregard the moving map display when making critical navigation decisions" 33. The pilot cross-checks an old database against the chart, or does not use it for airspace at all.

Handheld and tablet GPS

A handheld or a tablet is a situational awareness aid. It is not certified and not primary navigation. The AIM: "VFR GPS panel mount receivers and hand-held units have no RAIM alerting capability" 32, and the handbook adds that hand-held units "could present erroneous position and navigation information with no warning to the pilot" 33. Their failure modes are:

• the battery
• the signal through a window antenna
• the heat that shuts a tablet down 34.

The pilot of N9515A carried both a phone and a handheld, and both failed when he needed them.

Interference and jamming

GPS interference and jamming occur. The AIM: "Recognizing that GPS interference and test events resulting in the loss of GPS services have become more common, the FAA requires operators conducting IFR operations" under the air carrier rules "to retain a non-GPS navigation capability" 31. The FAA publishes the test events as GPS NOTAMs, with the area and the hours. A sudden unexplained GPS anomaly, a position that jumps or a track that bends, means a cross-check against ground references at once. The Warrior's non-GPS capability is the chart, the compass, and the VOR.

WAAS

WAAS augments GPS. The AIM: "The FAA developed the WAAS to improve the accuracy, integrity and availability of GPS signals" 35. Ground stations measure the satellite errors and broadcast corrections, with integrity monitoring, through geostationary satellites. A WAAS receiver has better accuracy and availability than an unaugmented one. It still has a battery and a database.

VFR flight following gives traffic advisories and safety alerts, workload permitting. The request goes to approach control or center with the call sign, type, position, altitude, and destination: "Norcal Approach, Warrior one two three four five, ten miles south of Salinas, three thousand five hundred, VFR to Paso Robles, request flight following." The AIM: "Traffic information may be provided to flights not operating on IFR flight plans when requested by pilots of such flights," and controllers "possess complete discretion for determining whether they are able to provide or continue to provide this service" 36.

Clock positions from the ground track

Traffic advisories come as clock positions from the airplane's ground track, not its heading. The AIM's traffic call gives:

• "Azimuth from the aircraft in terms of the 12 hour clock,"
• the distance in miles
• the direction the target is moving
• the type and altitude if known 37.

The AIM's figure: "traffic information would be issued to the pilot of aircraft 'A' as 12 o'clock. The actual position of the traffic as seen by the pilot of aircraft 'A' would be 2 o'clock" 37. An airplane crabbing 30 degrees right for the wind looks for 12 o'clock traffic at 11 o'clock, one hour left of the nose. The search sector shifts with the wind correction.

Radar service terminated

"Radar service terminated, squawk VFR" ends the service. The glossary: the phrase is "Used by ATC to inform a pilot that he/she will no longer be provided any of the services that could be received while in radar contact" 38. The AIM: "Except in programs where radar service is automatically terminated, the controller will advise the aircraft when radar is terminated" 37. After the call, navigation, terrain, and traffic are the pilot's responsibility, with no handoff coming. They were the pilot's responsibility before the call too.

A transponder answers radar interrogations. Mode A sends the four-digit code. Mode C adds pressure altitude. Mode S adds selective interrogation and a data link. The regulation describes the equipment as "Mode A 4096 code capability" with "automatic pressure altitude reporting equipment having a Mode C capability that automatically replies to Mode C interrogations by transmitting pressure altitude information in 100-foot increments," or "a Mode S capability" 39. The AIM: "Civil Mode A is identical to military Mode 3" 40, which is why the phrase is Mode 3/A.

The codes

The AIM: "Unless otherwise instructed by an ATC facility, adjust transponder/ADS-B to reply on Mode 3/A Code 1200 regardless of altitude" 40. The special codes are:

• 1200, VFR
• 7500, hijack
• 7600, lost communications
• 7700, emergency.

The pilot does not turn the knobs through those codes. The AIM: "when switching from Code 2700 to Code 7200, switch first to 2200 then to 7200, NOT to 7700 and then 7200" 41. A momentary 7700 triggers alarms on the ground.

Mode C is pressure altitude

Mode C reports pressure altitude, and ATC's computer applies the correction. The AIM's note: "Altitude encoders are preset at standard atmospheric pressure. Local altimeter correction is applied by the surveillance facility before the altitude information is presented to ATC" 41. The pilot never adjusts the transponder for the altimeter setting. A controller who reads a different altitude asks the pilot to check the altimeter setting, not the transponder.

ADS-B Out and In

ADS-B Out broadcasts the airplane's own position. The AIM: "Onboard avionics determine the position of the aircraft by using the GNSS and transmit its position along with additional information about the aircraft to ground stations for use by ATC and other ADS-B services. This information is transmitted at a rate of approximately once per second" 42. ADS-B Out is how ATC and equipped airplanes see the Warrior.

ADS-B In is optional and receives TIS-B traffic and FIS-B weather. TIS-B does not show all airplanes. The AIM: "Only transponder-equipped targets (i.e., Mode A/C or Mode S transponders) are transmitted through the ATC ground system architecture. Current radar siting may result in limited radar surveillance coverage at lower altitudes near some airports, with subsequently limited TIS-B service volume coverage. If there is no radar coverage in a given area, then there will be no TIS-B coverage in that area" 43. The display supplements the scan. A Cub with no transponder is not on it.

The transponder runs

An installed, operable transponder runs whenever the airplane is airborne in controlled airspace, with altitude reporting. Section 91.215(c): "each person operating an aircraft equipped with an operable ATC transponder maintained in accordance with § 91.413 shall operate the transponder, including Mode C equipment if installed, and shall reply on the appropriate code or as assigned by ATC" 44. The AIM adds that the airplane "SHOULD operate with the transponder enabled in uncontrolled airspace" too, when practicable 40.

The flight of N9515A

On March 9, 2021, a Cessna 170A took off from Shawnee, Oklahoma, about 9 in the morning, for Poplar Bluff, Missouri. The pilot was a 74-year-old commercial pilot and flight instructor with 1,750 hours. Near Poplar Bluff his phone powered off, his handheld GPS did not power on, and he could not find the airport. He landed in a field with about 10 minutes of fuel, and the airplane nosed over. He was not hurt.

The airplane "was equipped with a communication radio, but it was not equipped with very high frequency omni-directional range (VOR) equipment or a transponder" 45. He had a handheld Garmin GPS aboard and did not use it. He "navigated via dead-reckoning and following roads" and "occasionally referenced a mobile phone application to verify the airplane's position on a digitized visual flight rules (VFR) sectional chart" 45. He had no paper chart.

Fifteen to twenty minutes from Poplar Bluff, "the pilot's mobile phone powered off after its battery became depleted. The pilot stated that he then inserted the Garmin adapter into the airplane's cigarette-lighter socket, but the GPS device did not power on" 45. He held his heading, which took him over the city of Poplar Bluff. The airport is east of the city. He did not see it. He flew a couple of miles south, reversed course, and flew back over the city northbound.

Several miles north of the city, the left tank read empty and he estimated 10 minutes of fuel in the right. He turned into the wind and landed in a field. The airplane rolled 200 to 300 feet, and the main gear dug into soft ground. It nosed over, with substantial damage to the vertical stabilizer and the engine mounts. He was not hurt 45.

The NTSB tested the electrical system and found nothing wrong with the alternator, the regulator, the battery, or the socket. The investigator had the pilot plug the Garmin into his car: "The GPS device automatically powered-on when connected to the power source, with and without the device's battery installed." Its last position "was from a flight completed two days before the accident" 45. The probable cause: "The pilot's decision to make a precautionary landing in a field that contained soft terrain, which resulted in the airplane nosing over. Contributing to the accident was the pilot's decision to fly without a printed VFR sectional chart to identify the location of the destination airport" 45.

Where the pilot could have prevented the accident

A 1,750-hour instructor got lost over the town he searched for. Each decision below is marked with the PAVE category that applied to it.

The pilot programs the navigator before reaching the runway. The handbook: "Plan flights carefully before taking off. If navigating to user-defined waypoints, enter them prior to flight, not on the fly. Verify the planned flight against a current source, such as a current sectional chart" 46. A pilot who flies a mis-set flight plan exactly gets lost. The GPS draws a straight magenta line to the wrong waypoint exactly as it does to the right one. The handbook records the case of a pilot who "used waypoints created by another pilot that were not where the pilot flying was expecting" 46.

Head-down time is scheduled

In-flight programming takes attention from flying. Aviate first, then navigate. The handbook: "Minimize head-down time in the aircraft and maintain a sharp lookout for traffic, terrain, and obstacles" 46. The pilot enters a reroute in flight in pieces, with the eyes outside between pieces. The airplane is trimmed and on heading before the first keystroke. The pilot schedules head-down time.

Name the limitation

Whatever the pilot navigates by today has a limitation, and the pilot names it before flight. Each receiver has its own:

• the VOR is line of sight
• the GPS has integrity only with RAIM
• the tablet has a battery and a temperature limit.

The handbook: "The limitations of each type of receiver installation or use must be understood by the pilot to avoid misusing navigation information" 47. A limitation named on the ground becomes part of the plan. The pilot of N9515A discovered his limitation in the air, when he plugged in a GPS that did not turn on.

On any signal loss

On any navigation signal loss, a flag, an integrity warning, or a frozen screen, the sequence is:

• say it aloud, so that the loss is stated as a fact
• hold the last cross-checked heading
• rebuild the position from pilotage and dead reckoning, from the last fix and the time since.

The handbook's summary: "only the pilot can navigate the aircraft, and GPS is just one of the pilot's tools to do the job" 46.

The lost procedure has five steps, the five Cs: climb, communicate, confess, comply, conserve. The five Cs put the Pilot's Handbook's procedure in order. The handbook: "If a pilot becomes lost, there are some good common sense procedures to follow. If a town or city cannot be seen, the first thing to do is climb, being mindful of traffic and weather conditions. An increase in altitude increases radio and navigation reception range and also increases radar coverage" 23. Climbing improves the view, the radio, the VOR, and the radar all at once.

Rebuild the position

The pilot rebuilds the position from the last known fix. The time flown since that fix, multiplied by the groundspeed, is the radius of the circle the airplane must be in, along the heading held. At 90 knots, for example, 15 minutes is 22 miles. Inside that circle, the pilot matches large features to the chart: a river, a highway, a town with a water tower. The handbook: "If flying near a town or city, it may be possible to read the name of the town on a water tower" 23.

Logged actual times over checkpoints are the input for this step. A current nav log holds the last fix with its time.

Ground to chart

When lost, the pilot reads from the ground to the chart. The pilot picks the landmark first, a river bend or a highway crossing, then finds it on the chart. Chart-to-ground reading leads to a forced match. A pilot who wants the lake on the chart to be the lake below sees a match that is not there. The handbook's pilotage rule applies here: "If confused, hold the heading. If a turn is made away from the heading, it is easy to become lost" 9. The heading is the one thing the pilot still knows.

The radios resolve it

A VOR cross-fix or the GPS nearest page resolves position without any visual match. The handbook: "If GPS is installed, or a pilot has a portable aviation GPS on board, it can be used to determine the position and the location of the nearest airport" 23. Two radials give the point. One radial and a highway give it too.

Ask early

Any ATC radar facility can locate the airplane and vector it. The AIM: "Radar equipped ATC facilities can provide radar assistance and navigation service (vectors) to VFR aircraft in difficulty when the pilot can talk with the controller, and the aircraft is within radar coverage" 48. The handbook: "If the situation becomes threatening, transmit the situation on the emergency frequency 121.5 MHz and set the transponder to 7700. Most facilities, and even airliners, monitor the emergency frequency" 23. Asking early is airmanship. The AIM: "An aircraft is in at least an urgency condition the moment the pilot becomes doubtful about position, fuel endurance, weather, or any other condition that could adversely affect flight safety. This is the time to ask for help, not after the situation has developed into a distress condition" 49.

The escalation triggers

The triggers are specific. Any one of them means ask for help now, or declare:

• fuel below the plan
• darkness coming
• weather lowering.

The AIM: "Delay has caused accidents and cost lives. Safety is not a luxury! Take action!" 49. The pilot of N9515A had ten minutes of fuel and a working radio, and landed in a field.

A lost airplane still needs flying

Set a safe altitude and a cruise power first, and keep the eyes out. Circling a landmark head-down over a chart risks a collision and burns fuel. The handbook's climb comes with "being mindful of traffic and weather conditions" 23, and its GPS advice is to "maintain a sharp lookout for traffic, terrain, and obstacles" 46. Trim, lean, look outside, then work the chart in pieces.