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How do the CILS autopilots determine range to touchdown on most of your aircraft? Timing, altitude above Decision Height, or other? This is for a simple aircraft that doesn't have a big dollar flight management system.
Coupled autopilots flare the aircraft based on radar altitude. The pilot is still responsible for pushing the GA button for a go around. The pilot must also anticipate various failures during the approach and go around. It is the unreliability of these systems that make a pilot a critical part of the safe implementation of this system.
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Maybe I need to clarify my question. The issue is two-fold: a) Minimizing Localizer Overshoots you need to have range to the runway and also, b)setting tracking gains in the autopilot when on course and glide slope requires range to runway. What's the best (safest) method for automatically determining range to runway if you don't have the fancy Jeppesen database integrated into the cockpit/ FMS?
Maybe I need to clarify my question. The issue is two-fold: a) Minimizing Localizer Overshoots you need to have range to the runway and also, b)setting tracking gains in the autopilot when on course and glide slope requires range to runway. What's the best (safest) method for automatically determining range to runway if you don't have the fancy Jeppesen database integrated into the cockpit/ FMS?
Is DME too easy an answer?
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DME is great if you have the station automatically selected based on the ILS frequency pairing, per the Jeppesen database in your Flight Management System. If you don't have one of those databases integrated into the cockpit, you would have to select it manually. Industry spec's. for autopilot design say that the propensity for DME channel selection errors if accomplished manually to set up Coupled ILS is too great to be allowed. (It's okay for manual approaches since the pilot is in the loop.) Also it requires that a DME be located at the localizer ground antenna.
The FMS is not part of the auto land system on the Alaska MD-80s or 737's. I believe all CAT III qualified ILS's have DME associated with them, don't they? Also, autoland has been around much longer than FMS, GPS, or RNP.
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What's the best (safest) method for automatically determining range to runway if you don't have the fancy Jeppesen database integrated into the cockpit/ FMS?
How about the 3 to 1 method. If you are 1000' agl, your approx 3 miles from the end of the runway.
By the way. The Navy has demonstrated autoland capability of an F/A-18 on a carrier with GPS navigation only. I believe the aircraft uses a local GPS transmitter to augment the satellite bases system but sitting there watching your jet aim at a moving target that small means the pilot has to have some pretty serious trust in the system.
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Coupled ILS Approach Autopilot
I believe the aircraft uses a local GPS transmitter to augment the satellite bases system but sitting there watching your jet aim at a moving target that small means the pilot has to have some pretty serious trust in the system.
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