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Airpath compass correction instructions.

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  • Airpath compass correction instructions.

    COMPENSATING INSTRUCTIONS FOR AIRPATH COMPASSES, taken from: https://www.airpathcompass.com/J30/i...n-instructions

    Before attempting to compensate compass, every effort should be made to place the aircraft in simulated flight conditions. Check to see that doors are closed, flaps are in retracted position, throttles set at cruise position, engine(s) operating, and aircraft in a level attitude. All electrical switches, generators, radios, etc., should be in the position they will normally be for navigation flight.



    COMPENSATION
    • 1. Set adjustment screws of compensator on zero. Zero position of adjustment screw is obtained by lining up the dot on the screw with the dot on the compensator frame.
    • 2. Head aircraft on magnetic North heading. Adjust N-S adjustment screw until compass reads exactly North.
    • 3. Head aircraft on magnetic East heading. Adjust E-W adjustment screw until compass reads exactly East.
    • 4. Head aircraft on magnetic South heading. Note the resulting South error. Adjust the N-S adjusting screw until one-half of this error is removed.
    • 5. Head aircraft on magnetic West heading. Note the resulting West error. Adjust the E-W adjusting screw until one-half of this error is removed.
    • 6. Head aircraft in successive magnetic 30-degree headings and record all errors on the deviation card furnished with the compass.



    For satisfactory results, all extraneous magnetism causing over 30-35 degree compass errors should be removed from the aircraft, or the compass should be relocated to a position where uncompensated error does not exceed 30-35 degrees. Use a brass or other non-ferrous material screwdriver when making compensator adjustments.

    Best results can be obtained in actual flight compensation by following the procedure outlined below:
    • A. Set directional gyro from a sectional line or runway. (Allow for magnetic variation to ensure gyro corresponds to magnetic heading)
    • B. Follow procedures 1 through 6 above.
    • C. Re-check directional gyro occasionally for possible precession, and allow for such precession error in recording results on magnetic compass deviation card.



    NOTE: If aircraft is equipped, GPS can be used (allow for deviation) to establish reference headings for compass compensation. This technique will eliminate possible errors caused by gyro precession.

    For any questions please contact Airpath Instrument Company at the address or phone numbers listed above.



    COMMON COMPENSATION PROBLEMS

    Any time there is a maintenance or repair to your aircraft, it is recommended that the compass be compensated. This is particularly true if there is work associated with the removal of old and/or installation of new equipment in the instrument panel. New radios and relocation of speakers or intercoms could affect the compensation required. New hardware (i.e. screws, nuts, etc.) installed during maintenance can sometimes be the cause of excessive errors if the hardware is steel or magnetic.

    Loose electrical grounds, lighting, or extended periods of parking in North-South alignment on the ramp can lead to the magnetization of the airframe itself. This is often evidenced by excessive uncompensated compass error (more than 30-35 degrees). Engine mounts on single engine aircraft and center windshield posts becoming magnetized can lead to compensation problems. demagnetizing (degaussing) the airframe component or relocating the compass will solve this problem.

    Remember that every aircraft is different. Following the set-up procedures outlined above prior to compensation is important. As stated, in-flight compensation will achieve the best results. Landing gear position can sometimes affect deviation. Other factors to consider are: yoke position, cruise configuration, pilot heat, and de-icing equipment (particularly windshield anti-ice).

    Operators should consider removing any jewelry while compensating compasses. Such things as watches, rings, and eyeglasses can affect the amount of compensation required. If above method does not give satisfactory results, determine the amount of uncompensated error by aligning the reference dots on the compensator adjustment screws and frame or by removing the compensator assembly from the compass. If the uncompensated error is in excess of 30-35 degrees, troubleshoot for magnetization of aircraft components or excessive electrical interference.
    N29787
    '41 BC12-65

  • #2
    Diaphram Shelf Life

    There are many inquiries about the shelf life for commercial diaphragms. Our manufacturer, of the original material, states that the shelf life is indefinite as long as the material is kept clean and at a constant, stable temperature. Once the diaphragm is installed in the compass, under harsh weather conditions, exposed to compass fluid and UV light, we warranty them for two years. On average, the compass will not leak for 5-10 years dependent upon the conditions. All of that said, we have placed a 2-year shelf life from the date the material arrives at our customer's dock. Please be advised that we strongly recommend that these diaphragms be installed by FAA licensed overhaul/repair stations only.



    N29787
    '41 BC12-65

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    • #3
      Thanks for posting those instructions for Compass correction settings, I have often wanted to make corrections to my compass but often just fall back to the GPS . Which is not a primary flight instrument !

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      • #4
        Recently NOAA scientist have said that the magnetic north pole has moved more than 30 mile to the west, typically the pole will move some over one year but it has made a rapid movement over the last year and has caused some problems for navigation for aircraft and the military. They are not certain what may happen in the future.

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        • #5
          Must be cow farts!

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          • #6
            Must Be !

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            • #7
              Originally posted by waltermrich View Post
              Recently NOAA scientist have said that the magnetic north pole has moved more than 30 mile to the west, typically the pole will move some over one year but it has made a rapid movement over the last year and has caused some problems for navigation for aircraft and the military. They are not certain what may happen in the future.
              What way is west, when every way from the north pole is SOUTH?
              N29787
              '41 BC12-65

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              • #8
                Who looks at a compass these days?

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                • #9
                  Anyone taking a flight review. Never had an instructor cover everything up and hand you a sectional and say, "find your way home"?

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                  • #10
                    My flight training was similar , I had a flight instructor , older man with some 25000 hours of flight who used always to say, keep your head out the window, seems like that would be more where you gain situational awareness, not depending so much on electronics that seems to be the trend.

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                    • #11
                      I've flown over terrain for 45 years in Alaska. Mostly VFR but some IFR as well. The compass or it's direction transferred to a gyro was part of the flight following procedure used to verify that the ground features nearby matched the charts. Terrain makes it easy to locate and follow a route. The two times I flew in the Lower 48 as soon as I got over flat land it bothered me and the compass plus navaids became my friends. So yes I still use one.

                      Now....riding with the current grads of the glass panel class I wonder what they'll do when the GPS constellation or onboard gadgets fail to guide? Three GPS units in one friends plane all supported by electronic situation displays. Another took an instrument rating recently and remarked how hard it must have been to fly a non-RNAV approach without vertical guidance. They learn to follow the GPS' display and keep the little plane in the box.

                      So here's the dilemma....while VFR eyes in the cockpit on the glass panel, sometimes glance out to check the weather and scan for traffic, but do they really know where they are? Especially if flying nap of the earth in low weather for the first time?

                      I hope the electrons keep holding hands for them. A compass is always there if needed.

                      Gary
                      N36007 1941 BF12-65 STC'd as BC12D-4-85

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                      • #12
                        Originally posted by Hank Jarrett View Post
                        Anyone taking a flight review. Never had an instructor cover everything up and hand you a sectional and say, "find your way home"?
                        Yes I have, but never the compass. Any instructor conducting a review that did that to me would be invited to step outside. I've had tacho, ASI, Altimeter covered up.

                        How on earth would you get home with just a sectional if you don't know the direction you are travelling? That's just silly, Hank.

                        Rob

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                        • #13
                          No compass no problem. Day VFR helps. Night makes it more complicated. Where did you start the flight? What direction have you been heading prior to loss of compass and for how long = time and distance or distance made good. Where's the Sun relative to you in your hemisphere? Even on a cloudy day there may be shadows but granted rain and low clouds can obscure solar input. Public transportation corridors form shapes and angles that can be revealing. Terrain and natural features like waterways have shapes and relative locations. I could go on but if you once grasp an idea as to where you are then the chart will indicate what it should like in the direction you choose to travel. Head towards that or keep that off my left wing, etc.

                          I flew to 71* north and up there on Alaska's north coast the compass was a poor guide. Terrain and natural features were all I had for location. Snow cover and low light or whiteout conditions in winter made that more difficult. Once out of VOR reception there were a few NDB's that could be used to home or track outbound on a course of get a two station cross bearing. So yes it's best done over familiar territory but any flight review would have started at a known location unless the pilot was first kidnapped and blindfolded for a bit.

                          Gary
                          N36007 1941 BF12-65 STC'd as BC12D-4-85

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                          • #14
                            Originally posted by PA1195 View Post
                            So yes it's best done over familiar territory but any flight review would have started at a known location unless the pilot was first kidnapped and blindfolded for a bit.

                            Gary
                            I think I may have to start doing this when I give a flight review.

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                            • #15
                              My comment wasn't meant to incite a riot but perhaps a periodic question to the applicant might be in order: "Now that your glass panel and navaids are disabled (by fuse or switch) due the lightning hit where are we and how do we get to the nearest airport?" That might make for a meaningful discussion of alternative methods of determining position and orientation to a desired track.

                              Basic nav techniques remain an important skill: How far have we gone based upon our observed groundspeed and in what direction(s)? (Make them write it down periodically). How soon can we expect to see a landmark on the chart given our groundspeed and in what direction should we see that or them? (To temporarily replace the compass by physical orientation). Mark a planned route on a chart with periodic check points to confirm the path and groundspeed. (Have a pencil handy?) And yes only with a chart-terrain visually confirmed and then the compass. Assume the airspeed and static ports are frozen via covers, and the tach cable broke so learn a throttle position via manifold pressure gauge or throttle control position. Make it a learning experience not another tour de jour.

                              I've had instructors put me under the hood to practice IFR then remove it and force VFR without all the gadgets. It can happen in real flying so why not prepare?

                              Gary
                              N36007 1941 BF12-65 STC'd as BC12D-4-85

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