GPS Approaches

GPS approaches are the newest type of instrument approach procedure they have steadily grown into the most common type of approach since their inception back in 1994 airports especially smaller ones are turning to these types of approaches because they don't require expensive ground-based equipment like vor Zoar ILS s instead they use already established GPS satellite network to create an approach path for a specified runway using waypoints with each point defined by its latitude and longitude GPS belongs to the umbrella navigation method our nav or area navigation our nav allows for an aircraft to fly any course within a network of beacons as opposed to navigating directly to and from beacons like you would with a vor other forms of navigation that belonged to our nav include IRS ans and RNP under the hierarchy of GPS instrument procedures exists four types of approaches lateral navigation or L nav localizer performance or LP lateral navigation / vertical navigation or L nav / V nav and finally localizer performance with vertical guidance or LP v each of these types differ in sensitivity and the one you can expect to use varies depending on your onboard equipment and the GPS signal availability at a minimum you must have enough satellites for rain and you must have an up-to-date navigation database the GPS receiver in the aircraft will always automatically select the most precise approach available LP and LP v approaches require support of the wide area augmentation system or wasps l nav / v nav requires wasps or barrow aided GPS receivers and l nav only requires a standard GPS signal with rain LP v & LS nav / v nav provide the course guidance on both the CDI and glide path indicators the pilot should follow the glide path to the decision altitude LP and LM only provide lateral guidance and utilize an MDA the labels da or MDA will be displayed next to each type of the minimums in the approach chart to specify their classification however even though some of these types have vertical guidance as far as the FAA is concerned all GPS approaches are classified as non-precision approaches this is important to keep in mind for cross-country flights and Airport selection for alternates let's briefly go over the different types of GPS approaches the L nav approach is the most basic GPS approach it only provides lateral navigation and does not offer increasing sensitivity as you approach the runway this means that the CDI sensitivity will remain at zero point three nautical miles for full scale deflection all the way from the final approach fix to the missed approach point however some of the newest GPS receivers may provide lateral scaling which does in fact increase the sensitivity of the CDI as you approach the runway since this approach does not provide any vertical navigation the pilot should determine the proper descent rate needed to maintain the glide path angle and identify the proper missed approach point use the climb descent table in the terminal procedures publication as well as additional information on the approach chart to get the appropriate rate of descent for your ground speed an LP or localizer performance approach is similar to an L nav approach except its sensitivity increases from the final approach fix to the missed approach point as its name suggests the approach course mimics a localizer in a future lesson we'll be covering localizers which are typically a part of an ILS but for now just know that the course with will gradually narrow as you approach the runway providing you increasingly precise guidance unlike real localizers LP approaches all use the same convergence angle offering a more consistent experience to the pilot at the final approach fix the precision for full scale deflection is the same 0.3 nautical mile distance that was used in L Neff this will gradually scale down to only 350 feet for a full scale deflection at the runway threshold an LP approach will be published when this angular scaling eliminates obstacles in the L nav approach course thereby creating a lower MDA for pilots who are flying wasps equipped aircraft remember this angular scaling is made possible because of wasps which you've learned previously increases the accuracy of your GPS position laterally and vertically again no vertical guidance is offered so you'll need to find the appropriate descent rate to use as previously discussed l Mayo /v nav approaches were the first type of GPS approach with vertical guidance they were designed to be used with Barrow aided GPS receivers however they also work with wasp receivers the GPS receiver uses altitude from the barrel aiding altimeter or the wasps derived altitude to determine if the aircraft is on glide path the same sensitivities offered as L nav that being zero point three nautical miles for full scale deflection vertical scaling is also consistent through the descent but the precision varies between manufacturers some of the newest GPS receivers may provide scaling for both lateral and vertical guidance but this is only an aide to the pilot and never lowers the published minimums the lpv approach which stands for localizer performance with vertical guidance is the most precise GPS approach option the lateral guidance is the same as the LP approach there is also scaling for the vertical guidance resulting in a final precision of plus or minus 49 feet at the missed approach point unlike the L nav /v nav this approach is only available with a wast receiver this eliminates some of the errors with bare weighting such as hot and cold temperature effects incorrect altimeter settings or absence of an altimeter source the extreme accuracy of the wha system provides lateral and vertical guidance down to a decision altitude that can be as low as 200 feet AGL remember though it is not considered a precision approach instead the FAA categorizes it as an AP V or an approach with vertical guidance in some cases the FAA has not yet developed an LPD approach and the only minimums available will be l nav if you're flying an aircraft with a wasp receiver the approach mode may show as L nav plus V or L P plus V this is called an advisory vertical guidance this vertical guidance is derived from your GPS receiver and will not be depicted on the approach chart even though this provides vertical guidance it is only advisory meaning you must still use the L nav or LP published minimum descent altitude be aware that the glide path could potentially take you below step-down fixed altitudes but all said and done it is nice to have an advisory glide path to help with situation awareness on a non-precision approach when planning to use a GPS to conduct approaches make sure that you check the GPS status prior to departure you should be familiar with checking the GPS on the before taxi and the before takeoff checklist but let's review some of the specific considerations the GPS status page provides information about the satellites in your reception in the top left corner is a satellite constellation diagram which shows the relative position of the satellites that are currently in view in the upper middle box we've got the satellite status which shows the accuracy of the aircraft's GPS fix below the separator is the current calculated GPS position time altitude ground speed and track for the aircraft in the top right corner is the GPS receiver status first is the active receiver this can either be GPS one or GPS two since there are two receivers second is the solution type this can be acquiring 2d nav 2d DIF nav 3d nav or a 3d diff Neff when the receiver is in the process of acquiring satellite signals acquiring is indicated until a sufficient number of satellites has been acquired once the receiver is fully acquired the GPS solution should be 3d DIF nav and s bas satellite-based augmentation system will indicate active if you have something else as your GPS solution ensure that loss is enabled by pressing the S bas soft key and verifying the checkbox for wasps is selected Agnes is the wasps equivalent for Europe and M SAS is the wasps equivalent for Japan and Australia the bottom portion of the page is devoted to the satellite signal strength bars as the GPS receiver locks on to satellites a signal strength bar is displayed for each satellite in view with the appropriate satellite number below each bar the progress of satellite acquisition is shown in three stages as indicated by signal bar appearance no bar indicates the receiver is looking for the indicated satellite a holo bar indicates the receiver has found the satellite and is collecting data a light blue bar indicates that the receiver has collected the necessary data and the satellite signal can be used a green bar indicates a satellite is being used for the GPS solution a checkered bar would be shown if the receiver has excluded the satellite from being used for example a fault exclusion ad indication denotes the satellite is being used as part of the differential computations with watts each satellite is identified by a PRN or pseudo-random noise number essentially a satellite identification number hua satellites begin with the number 1 while regular GPS satellites start with a zero each satellite must transmit data to the receiver for 30 seconds before the satellite may be used for navigation for this reason we verify the GPS status as part of the before takeoff checklist under GPS availability since the GPS receivers may not be fully acquired on the ramp that's it for the GPS status page now let's actually load an approach to select an approach you press the procedures button on the right side of the display you'll then want to choose the select approach menu option it works best if you already have the destination Airport set in but if you don't the system will ask you for the airport that the approach belongs to you'll then be shown a pop up menu of all the approaches available to you scroll to the approach you want being careful to select the right one sometimes there are multiple approaches of the same type to a runway to distinguish between them the names of the approaches will contain a letter suffix starting with Z and continuing backwards with the correct approach selected choose where you'd like to begin the approach from your options are vectors to final or any of the published initial approach fixes for that approach if you don't know if you'll be receiving vectors or not it's a good idea to choose one of the initial approach fixes instead there's a convenient activate vector to final menu option that you can use instead of having to reload the whole approach if you selected the wrong starting point if the initial approach fix you selected includes a published course reversal the g1000 may ask you if you want to fly it generally if you're not sure yet it's safer to select yes instead of no because you can always skip it later if you don't need it but if you did need it you wouldn't have to reload the approach again you then have the option of inputting the approach minimums into the system to receive an altitude bug on your altimeter you can input value increments of 10 feet when necessary round up to the next highest option finally you'll be given the option to load or activate the approach loading we'll simply append the approach to your GPS flight path to fly the approach you'll need to activate it however based on your situation you may want to hold off on doing so activating the approach will direct you towards the initial approach fix skipping over any other intermediate fixes that you might have in your flight plan if you load the approach you can easily activate it later on by pushing the procedures button and selecting activate approach with the approach activated simply follow the cd-i through your approach route remember the GPS receiver in the aircraft will always automatically select the most precise approach available once an approach is loaded the CDI will display which approach minimum should be used for an approach that offers vertical guidance the glide path is shown adjacent to the altimeter with a purple diamond serving as your indicator like with the CDI apply corrections towards the diamond now that you have some background with the various types of GPS approaches let's fly an example using the Arnav gps three six right lpv into Tulsa Oklahoma many GPS approaches follow a basic T design containing two initial approach fixes perpendicular to the final approach course creating a t-shape the waypoint at the intersection can be used as either an intermediate fix or a third initial approach fix and will have a four nautical mile holding pattern published at it now let's say you're approaching Tulsa from over Zuck ski flying east towards Jaffe which is where you will immediately join the final approach course of 360 degrees no procedure turn will be necessary as denoted by the term no PT along the path looking at the profile view you should remain at 3,500 feet or above until passing jab feet then you can descend down to 2500 feet until the final approach fix denoted by the lightning bolt arrow from here follow the glide path on your PFD to the LP V decision altitude of 850 feet MSL this is where you make your decision to continue the approach to land or perform a missed approach flying an approach without vertical guidance offers a challenge that isn't present in an LP V approach as stated before it is up to you the pilot to determine the necessary rate of descent to maintain the depicted glide path this time let's take a look at the RNAV GPS Zulu 9 LP approach into Telluride Colorado with mountain peaks above 14,000 feet east of the field it's easily one of the trickiest airports to fly into so let's break it down word you're approaching Telluride from the Northeast tracking direct to one of the initial approach fixes cones the cones fix contains a halt in this case as the hold is part of the approach procedure it's known as they hold in lieu of a procedure turn which is now called a racetrack procedure and serves the same purpose as a procedure turn the holding pattern is a maneuver completed when the aircraft is established on the inbound course after executing the appropriate entry if cleared for the approach prior to returning to the holding fix and at the prescribed altitude no additional circuits of the holding pattern are to be performed if pilots elect to make additional circuits to lose excessive altitude or to become better established on course it is their responsibility to advise ATC upon receipt of their approach clearance the g1000 will by default continue on to the next Waypoint after entering the hold to keep it from cycling to the next Waypoint turn on suspend mode remember aside from a few exceptions procedure turns are required to be performed when depicted on a chart if the term no procedure turn or no PT is depicted on the initial approach segment the procedure turn should not be flown if ATC vectors you onto the final approach course after an initial approach fix then no procedure turn should be flown finally if ATC tells you cleared straight in no procedure turn should be flow if you're uncertain whether your ATC clearance intends for a procedure turn to be conducted or instead allows for a straighten approach you should immediately request clarification from ATC since we're arriving from the Northeast we'll need to fly a parallel holding pattern entry in other situations you need to determine which entry to use based on position in relation to cones when flying the course reversal determine the descent rate necessary for a three point five nine degree glide path by estimating what your ground speed will be on the inbound course then using the client ascent table and the terminal procedure supplement find the needed rate of descent and interpolate when necessary when intercepting the initial approach course of 102 degrees toward cones you should be at or above 13,000 feet since you were approaching from the Northeast you might have been higher since you needed to navigate above or around some pretty high terrain if you have a lot of altitude that still needs to be lost consider flying additional circuits around the hold of course remember to get clearance for that from ATC first and enable suspend mode on the g1000 after passing cones descend a twelve thousand nine hundred feet and maintain that altitude until at set ma the final approach fix as denoted by the maltese cross once reaching set MA begin your descent at predetermined descent rate as well as your turn left to your final approach course of zero nine six degrees continue descending down to the MDA of ten thousand six hundred and forty feet once reached you will level off assuming you do not already have the runway in sight on this approach arriving at the MDA is not your missed approach point instead the missed approach point is a fix called RW zero nine which is the threshold of the runway depicted on the approach plate you will fly the MDA all the way until this point before executing the missed approach the g1000 does not automatically sequence past the mist approach point when the aircraft reaches that point we normally plan for a missed approach so it might seem odd that the g1000 is set to assume you're going to land but outside a flight training aircraft don't go missed that often the missed approach segment is flown with a standard precision of full scale deflection at 0.3 nautical miles by not sequencing to the missed approach point the CDI sensitivity remains in the respective approach mode so that the pilot can have more precise guidance as they descend to the runway if you do go missed you need to activate the missed approach segment by turning off suspend mode this means that part of your missed approach procedure must be to press the suspend button to sequence the g1000 to the next Waypoint remember if ATC gives you alternate missed approach instructions you need to comply with those instructions over the procedure given by the g1000 earlier we discussed the level of approach minimum we received depends on your aircraft's equipment type and GPS signal if your aircraft is equipped with wasps it is an able and active the g1000 will alert you if you lose any GPS reliability while flying a gps approach there is no active monitoring of the GPS signal required by the pilot if there is a loss Oh reduced quality of GPS signal the g1000 will alert the pilot by displaying messages in the advisory window or on the CDI depending on the type of GPS issue or signal error that's occurring it is important to review the latest version of the g1000 manual to become familiar with the different types of advisories and know if they require an immediate missed approach or if the pilot can continue the approach but use higher minimums flying a GPS approach is similar to other types of approaches but it does have some differences from the typical ground based approach systems with more RNAV GPS approaches being published pilots will have more options when flying into some of the smallest and remote airports on the planet allowing an increase in safety and convenience

Channel: ERAU SpecialVFR

Views: 71,637

Rating: 4.956912 out of 5

Keywords: flying, flight, instrument rating, IFR, IMC

Id: PNoGghQDMX4

Length: 19min 35sec (1175 seconds)

Published: Thu May 28 2020