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Bending the Map

Updated: Aug 29, 2022

In 2004, Cessna Aircraft Corporation announced the integration of the G1000 glass cockpit in their C172 single-engine airplanes. The good news was that this new avionics and navigation package provided pilots with a host of tools including: integrated weather, enroute charts, airport diagrams, Sirius satellite radio, and a moving map display. And, they allowed the pilot to choose how they'd like their maps displayed: north-up, or track-up. The goal of this integrated solution was to provide the pilot with a greater awareness of their position. But good tools do not make a good pilot.

Normal presentation (PFD and MFD)

Here's a typical presentation. The primary flight display on the left (PFD) shows the altitude, heading, speed, rate of climb/descent, barometric pressure, attitude (straight and level, or in a turn), frequencies for communication and navigation, and an insert on the left for traffic in the area.

The multifunction display on the right (MFD) shows the current engine performance: RPM, fuel flow, oil pressure and temperature, engine gas temperature, fuel quantity, vacuum system performance, and electrical system performance. Unfortunately, most new pilots focus less on those items than they do on the big green blob in the center of the display: the map.

An airplane is just a piece of equipment, however, and sometimes systems fail. Here's an example of what the primary flight display looks like when the AHRS (attitude and heading reference system) fails. Nobody wants to see big red hash marks across their screen, but is this an emergency? Not necessarily. The communication and navigation radios are still working and if you refer to the MFD, the engine instruments (plus the noise outside the cockpit) assure you that the engine is still spinning. And you have secondary references for attitude, altitude, and airspeed. Although I wouldn't consider this an emergency I'd probably still want to find an airport, land, and get a cup of coffee while the maintenance techs figure out what went south.

The point here is that you fly with your head, not your hands. Situational awareness is key to survival.

AHRS Failure

Prior to GPS navigation, aircraft were equipped with radios that received signals from ground-based transmitters. The onboard radios transmitted a signal to an instrument on the cockpit that pointed to the transmitter or, in the case of satellite-based transmitters, an imaginary point in space. Coupled with this information, the pilot consulted maps and verified that they were on course. Then, using a basic time*speed=distance equation, determined if they'd make it to their destination in time for dinner. This method of navigation, referred to as "dead reckoning" was a favorite of the Lewis and Clark team. Rather than ground-based instrumentation, they logged the position of the sun, moon or stars and used a chronometer to measure time.

The second most popular means of navigation was by reference to landmarks, known as "pilotage." What both forms of navigation have in common is the map. I've often wondered how the settlers survived long trips, not just in terms of food, shelter, and the rigors of travel, but the loneliness and fear that comes with being lost. The truth is, sometimes they didn't. We know that adults form mental models of their environment: a mental picture of the way things "should" be. When their environment presents a different picture, sometimes we rationalize that the information we're receiving is wrong; the compass is broken, our watch has stopped, or our charts are mistaken: we "bend the map" to fit our mental model. Imagine Lewis and Clark standing on a mountain spinning their maps until they agreed on the appropriate orientation. A friend of mine used the acronym "TLAR" in one of our instrument ground schools as a good reminder to balance good tools with good judgement. TLAR stand for "that looks about right." I recently read "Deep Survival" by Laurence Gonzales; a fantastic read and good insight into characteristics shared by survivors. I thought I'd paraphrase some of his remarks as they're a good reminder of the skills our ancestors relied upon as they trekked to the New World and their new homes:

  • "Perceive, believe: even in the initial crisis, survivors immediately recognize, acknowledge and accept the reality of their situation...they believe they will succeed.

  • Stay calm: in the initial crisis, they make use of fear...which turns into anger, and that motivates them makes them even sharper.

  • Think/analyze/plan: they organize, set up routines and institute discipline and disregard thoughts that their situation is hopeless.

  • Take correct, decisive action: they deal with what is within their power from moment to moment, hour to hour, day to day. And they leave the rest behind.

  • Celebrate your successes: survivors take great joy from even their smallest doing so, they create an ongoing feeling of motivation and prevent the descent into hopelessness.

  • Count your blessings: they become rescuers instead of victims...there is always someone else they're helping more than themselves, even if that someone is not present.

  • Play: movement becomes survivor who had to walk a long way counted his steps, one hundred at a time, and dedicated each hundred to another person he loved.

  • Do what is necessary/never give up."

Early day three of the Apollo 13 mission, an explosion and subsequent CO(2) leak necessitated the flight and ground crew to come up with an alternate plan to return the astronauts safely home. Procedures called for the crew to use their onboard sextant to find a suitable star and then use the onboard computer to verify the guidance platform's alignment. The debris from the ruptured service module blocked all visible stars... so they used the sun. At 73:46 hours the air-to-ground transcript describes the event:

Lovell: O.K. We got it. I think we got it. What diameter was it? Haise: Yes. It's coming back in. Just a second. Lovell: Yes, yaw's coming back in. Just about it. Haise: Yaw is in... And I imagine Jim Lovell turning to look out the porthole of the Lunar Module at his beacon home and saying..."that looks about right."

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1 Comment

Much of the technical is beyond me, but the important stuff comes through loud and strong! Well said!

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