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Putting it a ll together, Port II In my article in Ihe March issue we reviewed pilot actions when Hying on approach using a GNS480, a DAC GDC3l GPSS and a KFC200 autopilot all working together. Now let's look at other differences in avionics and approach types. Difference between a DA and an MDA The DA is a decision altitl/de, Momentum may cause the aircraft to continue to descend below the DA for a brief time whi le you make your decision and start the aircraft back up for a mi ssed approach, (Note: An approach with a published DA is designed wi th obstacle clearance to permit this,) This is not true with a minimum descelll aitilllde (MDA). You have to level off at or above the MDA without descending below it until you have the runway in sight and are in a normal position to descend, If you descend below the MDA without the runway in sight, even briefl y, you have violated the regulations. More importantl y, you have put yourself and your passengers at risk, If you use the advisory vertical guidance and start a missed approach just before you reach the MDA, you will likely only complete approaches when the visibility and the cloud base are well above minimums. On the other hand, if you level off at the MDA and continue to the MAP, you will be able to safely complete approaches when the conditions are closer to minimums. ILS differences For an LLS, everything is similar except you must have tuned and identified the LLS frequency and selected the localizer as the navigation source for your HSI. The GNS480 and GNS530W can automatically switch the HSI navigation source to the localizer for an LLS approac h. There is an exception to the auto-switch capability when the autopilot is a KFC225 or a KAP 140 and the GPS is a 530W. In this instance, the GNS530W cannot be configured to auto-switch. GPSS differences and issues Certain installations of GPSS units can affect when roll steering is available to the autopilot. In an effort by the FAA to protect you from yourself on an ILS approach, they require that the GPSS be disabled when an lLS (localizer) frequency is chosen as the navigation source for the HSI. This means that if you try to get ahead of the situation when nearing your destination and select LLS as the source for the HSI, it will prevent the GPSS from providing steering to the autopilot. The switch will occur automatically when the navigation is auto-switched by the GPS . Supposedly this won't be a problem because, according to the Pilot Guide for the GNS480 and the GNS530W, the auto-switch does not occur until within 1.2 nm of the final-approach course and aligned within 45 degrees. The problem is that I have seen my GNS530W auto-switch while going outbound, In my opinion this adds confusion at a critical time and is not a good idea. It is similar to the bogus idea that forced the prior generation of GPS annunciator control units (ACUs) to automatically switch the HSI to the nav radio anytime an [LS frequency was tuned in. I remember customers complaining that the ACU was broken, and that they could not select the GPS for navigation, Both the Icarus SAM I and the S-Tec 90 1 GPSS units can be disabled by the GPS, and installation manuals indicate that the disable is to be wired to the GPS. J have recommended that this interconnect not be done and several individuals have obtained a field approval for the change. The Century A K I 081 and the DAC GDC-31 don 't have a disable capability, so it is not an issue for them. GPS differences The G S480 will provide roll-steering information throughout the entire procedure and automatically initiate the missed-approach guidance. This is true on an lLS final approach leg as well. Unfortunately, the GNS530W stops sending roll-steering commands to the GPSS at the FAF all the way to the MAP. For those with a legacy autopilot that has vertical guidance, this should not be an issue because GPSS and vertical gu idance are mutually exclusive. But if you are using an autopilot that does not have vertical guidance and prefer to use the GPSS for lateral guidance on an ILS approach, you are forced to switch the autopilot to the approach mode of tracking, which is not as precise or as smooth as roll steeri ng, Some will argue that it's not legal to fl y the final segment coupled through roll steering, In my opi nion, this is not strictly true. The requirement is that the HSl must use the localizer and GS as the source for displaying the ILS , The pilot must monitor the HSJ and is responsible for making any corrections to the flight path. The tools the pilot uses to accomplish this task are up to the pilot. Some pilots hand fly, some use a wing leveler, some use the heading bug with an autopilot, some use the localizer coupled to the autopilot, some use GPSS for the lateral autopilot control. Regardless, if the course or GS needs correction, as indicated on the HSI, the pilot is responsible for causing that correction. Autopilot differences Several of the S-Tec autopilots use the NAY key for approach mode instead of an APPR key, The Century Ul uses the LOC NORM key for the same purpose, The S-Tee 55X has GPSS roll steering built in and the pilot switches between nav
tracking and GPSS tracking by repeated pressing of the AV key. The 55X also has an APPR key to activate approach mode. The KFC 225 and KAP 140 autopi lots have roll steering built in. There are no autopilot keys for GPSS ; it is automatic if connected. Anytime the HSI nav source is GPS, the autopilot will follow roll steering. The autopilot does not support a GS when GPS is the nav source. So for the GNS530W, Garmin had to fake out the autopi lot to get it to capture a GS on GPS approaches. This is accomplished by a pseudo-signal that indicates to the autopilot that a localizer is the nav source when tracking a GPS approach with vertical guidance. Special software is used to prompt the pilot to activate the autopilot outputs and instruct the pilot to press the APPR button on the autopi lot. This same logic is not available on the GNS480, so the built-in KFC225 GPSS is not supported. To obtain GPSS with a KFC225, one approach is to add an Icarus SAM I connected through the heading-bug input. The DAC GDC31 GPSS unit would probably work, but the KFC225 is not included on the STC. John Collins, Charlotte, North Carolina. owns a 1968 V3SA. He is a commercial pilot with more than 4,(XX) hours. has a BS in electrical engineering and has YoIOrked as an engineer and software d~ oper for IBM and for his own technical business. John owned on FBO with an avionics shop that he operated for six years. QUESTIONS FROM MEMBERS ROLL STEERING Bill and Pam Smead Greenvi lle. Tennessee Q: We read wilh interest your November 2007 article and olher ABS articles on roll sleering. We fly a 1999 Baron with KfC225 AP/flighl direclor. 11 come from the factory wilh a KLN90B but we recently installed a Gormin 480. I have read several times Ihe flight manual supplemenl for the 225 and the aircraft pilot manual. We gel excellent course guidance and autopilot function in bolh NAV and APR modes for inbound and outbound GPS courses. but get no course guidance during the procedure turn or when ffying the holding poftern. The GNS480 does annunciate the correct turns. but this does not result in autopilot response unless we change to heading mode. If there's something we are missing on sefting up the units. we would appreciate your advice. If not. are there installation options that have not been hooked up that would odd these features? A: The KfC225 has a built-in roll steering via the ARiNC 429 intertoce that is capable of flyi ng holds. procedure turns. DME arcs and all of the flight plan turns. When the KfC225 internal ARINC 429 roll steering is connected to a GPS. it is automatically activated any time the GPS CDI buffon has GPS selected and outputs the GPS annunciator. The problem is that there is no support in the KfC225 for verticol guidance when ARINC 429 roll steering is selected. So you can have GPS roll steering or GPS GS copture, but not both. The GNS480 intertoce to the KfC225 uses only the lofter. UPGRADING TO WAAS Steve Self. Dallas, Texas Q: I recently upgraded my Gormin 530 to WAAS and after reinstalling in my V35B, experienced a complete loss of sotellites after dialing in VOR frequencies upon returning to Dallas from Mississippi. We removed the box, placed it on the test bench and discovered the rodio portion hod foiled. It was returned to Gormin for repoirs. After the first WAAS upgrade, we experienced interior panel light failure on the boffom rheastats.After turning them on to light the circuit breaker ponel, electncol burning smells were present so they were turned off and we are now inspecting that system. Is anyone else experiencing similar problems offer Ihe WAAS upgrade? A: for the most port, the upgrades I am aware of went well. I know of two situations where there were problems. One was on a 430 upgrade to a 430W. Shortly after it was reinstalled, within a few days, the screen backlight foiled. Even though the component involved was not covered by the WAAS upgrade warranty, Garmin accepted it bock as a warranty repair since it foiled so close to the upgrade. They confirmed the fault and replaced the power converter boord, but they also complete- Iy replaced the front bezel, screen cover and buffons with new for solely cosmetic reasons. The other situation I heard of indirectly, in a post on rec.aviation.ifr news server, occurred after installation of a WAAS version 3.0 software upgrade. I copied the report and am repeating it here: 'I hod the upgrade installed a liffle while ago and it seems to have impacted my screen. After the rodio has been running a while, I notice that when I change pages, the previous page seems to have 'burned in' to the screen for a few seconds and gradually fades away. I also found that on startup, especially if the radio has been used in the previous hour or so, the screen was nearly impossible to read until I manually set the display seffings contrast. "I contacted Garmin tech support and they said they'd seen something like this with the upgrade. They hod me set the contrast as "auto" and set the contrast to a number around 095. They said it's best to leove the contrast as auto, since apparently it needs to be constantly tweaked as the screen heats up, but that the new software sometimes fouls up the reference poinl, setting it too high. "I set the contrast to 095/auto, and now it works at startup. But I notice that after the unit has run a while, the "burn in' is still there, although it fades after a few seconds. I suspect that either the new software makes the unit run hofter, or it has a problem adjusting contrast as the radio heats up.' @
Page 1 and 2: THE OFFICIAL PUBLICATION FOR BONANZ
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