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Instrument Approach Auto-pilot buttonology?

Joe Larussa

By Joe Larussa
in General Mooney Talk

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alextstone Mentor

alextstone

Posted
Posted

Let me preface this by stating that do not have the same equipment you do, nor am I a CFII...however I am willing to pretend I know what I am talking about from the comfort of my living room in relative anonymity some distance away from you.  In other words, try this at your own risk....

Five phases of the approach:

1.  Briefing the approach and pre-loading frequencies, etc.

  • Current weather is above published AND personal minimums
  • Tower is open (approach is NA if not)
  • Brief NOTAMS
  • Review the Missed Procedure (notice that there are two possible missed approach holding patterns - each with the same fix but different cross references as to DME)  
  • Set up the Equipment:
    • STEC - HDG Mode, GPSS OFF
    • 530 GPS - Load ILS approach with "Vectors to Final", VLOC mode
    • HSI - Heading Bug set to current flight path.  CDI set to needle head pointing to 221 degrees (inbound ILS course)
    • NAV 2 - Here's where you will get differing opinions... I prefer to have the VOR for the missed set up and to use it initially, thus taking the GPS out of the missed equation until I am comfortably stabilized.  So, I would set NAV 2 to 115.2 SAC with the compass rose on the CDI set to 58 degrees (the outbound radial toward the fix)  During the Missed, you will have more to do than just fly that radial, but at least you have a starting point (this of course is a backup to the GPS, more on that later)

2.   Vectors.

Your autopilot appears to have "Dual Mode" which means that you can Press both HDG and NAV together within 45 degrees of the final approach course while leaving the AP in HDG mode, thus arming NAV while still staying in HDG mode (from the STEC 60-2 manual):

4.2.1.6 Dual Mode Intercept NOTE: During operations with an HSI, simultaneous activation of both the HDG and NAV modes will provide selected angle intercepts. In flying a radial or localizer intercept, the autopilot will follow the heading bug until the aircraft reaches the proper on course turn point. It will then switch from HDG to NAV mode automatically. Selected angle intercepts may be used during VOR, localizer front course and back course (REV) operations. Localizer intercept angles greater than 45º usually result in some course overshoot, depending on the distance from the station and speed of the aircraft. Therefore, angles greater than 45º are not recommended.

  • STEC - HDG AND NAV pressed

2.  Intercepting the Localizer and glideslope

  • STEC - monitor to verify a switch to NAV then APR upon intercept of the localizer.  Also, realize that for the GS to couple automatically you MUST be below the GS centerline as per the manual:

4.2.2.3 Intercepting and Coupling the Glideslope To arm the automatic glideslope (GS) capture function, the following conditions must be met: 1. NAV receiver must be tuned to the appropriate frequency. 2. The glideslope signal must be valid; no flag. 3. The autopilot must be in NAV/APR/ ALT modes. 4. The aircraft must be 60% or more below the GS centerline during the approach to the intercept point, and within 50% needle deviation of the localizer centerline at the point of intercept, usually the outer marker. 4-22 2nd Ed: Nov 01, 01 SYS 60-2 POH NOTE: GS arming will occur when the above conditions have existed for 10 seconds. Illumination of the GS annunciator will occur, indicating arming has been accomplished. The ALT annunciator remains on. GS capture is indicated by extinguishing of the ALT annunciation at GS intercept.

Therefore, you should also monitor the capture of the glideslope and be ready to manually activate the GS on the autopilot using the following:

4.2.2.4 Manual Arm/Automatic Capture If approach vectoring locates the aircraft above or too near the GS centerline at the intercept point, usually the outer marker, it becomes necessary to execute a manual arming of the GS. This is done by: 1. Pressing the ALT switch once if operating in the altitude hold mode. 2. Pressing the ALT switch twice if operating in the VS mode. Once capture is achieved, the GS annunciation will illuminate, and the ALT annunciation will extinguish. NOTE: If it becomes necessary to establish a holding pattern at the outer marker, automatic glideslope arming can be disabled by pressing the NAV switch a second time while in the NAV/APR mode. The GS annunciator will flash, and the Disable (DSBL) annunciator will illuminate, to indicate that the GS mode is disabled. To reestablish GS arming, press the NAV mode switch again. The DSBL condition annunciator will extinguish, the GS annunciator will cease to flash.

3.  Stabilized on the glideslope

  • STEC  -  finger on the AP disconnect
  • HSI - monitor the approach
  • GPS - activate the approach so that you may switch GPS directed missed procedure if necessary 

4.  Missed approach procedure.

  • STEC - HDG Mode, turn to 90 degrees
  • NAV 2 - watch for the needle to center, then track it outbound on 58 degrees by turning the heading bug.
  • GPS - stay in suspended mode until you have climbed to 3000 feet and you are within 20 degrees of the outbound of 58 degrees.  This should keep your GPS from flaking out.  At this point, unsuspend the GPS, verify that the correct leg and fix are active (COSKA), AND that you have good situational awareness, then do the following:
    • verify that the GPS reverted to GPS mode in the unsuspend process.
    • activate GPSS and fly the missed with the GPS 
    • set NAV 2 if necessary to fly the approach with it as a backup (I would set up both VOR's and flip flop the frequency to determine my fix so that I could leave NAV 1 st up for the ILS assuming that I planned to try the approach again)

My goodness, that's a lot and I am certain I missed some detail.  Moreover, as I mentioned, I have never used your setup AND I am not a CFII....Grab a safety pilot on a VMC day and try it for yourself.

 

Alex

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Joe Larussa Experienced

Joe Larussa

Posted
  • Author
Posted
38 minutes ago, alextstone said:

Let me preface this by stating that do not have the same equipment you do, nor am I a CFII...however I am willing to pretend I know what I am talking about from the comfort of my living room in relative anonymity some distance away from you.  In other words, try this at your own risk....

Five phases of the approach:

1.  Briefing the approach and pre-loading frequencies, etc.

  • Current weather is above published AND personal minimums
  • Tower is open (approach is NA if not)
  • Brief NOTAMS
  • Review the Missed Procedure (notice that there are two possible missed approach holding patterns - each with the same fix but different cross references as to DME)  
  • Set up the Equipment:
    • STEC - HDG Mode, GPSS OFF
    • 530 GPS - Load ILS approach with "Vectors to Final", VLOC mode
    • HSI - Heading Bug set to current flight path.  CDI set to needle head pointing to 221 degrees (inbound ILS course)
    • NAV 2 - Here's where you will get differing opinions... I prefer to have the VOR for the missed set up and to use it initially, thus taking the GPS out of the missed equation until I am comfortably stabilized.  So, I would set NAV 2 to 115.2 SAC with the compass rose on the CDI set to 58 degrees (the outbound radial toward the fix)  During the Missed, you will have more to do than just fly that radial, but at least you have a starting point (this of course is a backup to the GPS, more on that later)

2.   Vectors.

Your autopilot appears to have "Dual Mode" which means that you can Press both HDG and NAV together within 45 degrees of the final approach course while leaving the AP in HDG mode, thus arming NAV while still staying in HDG mode (from the STEC 60-2 manual):

4.2.1.6 Dual Mode Intercept NOTE: During operations with an HSI, simultaneous activation of both the HDG and NAV modes will provide selected angle intercepts. In flying a radial or localizer intercept, the autopilot will follow the heading bug until the aircraft reaches the proper on course turn point. It will then switch from HDG to NAV mode automatically. Selected angle intercepts may be used during VOR, localizer front course and back course (REV) operations. Localizer intercept angles greater than 45º usually result in some course overshoot, depending on the distance from the station and speed of the aircraft. Therefore, angles greater than 45º are not recommended.

  • STEC - HDG AND NAV pressed

2.  Intercepting the Localizer and glideslope

  • STEC - monitor to verify a switch to NAV then APR upon intercept of the localizer.  Also, realize that for the GS to couple automatically you MUST be below the GS centerline as per the manual:

4.2.2.3 Intercepting and Coupling the Glideslope To arm the automatic glideslope (GS) capture function, the following conditions must be met: 1. NAV receiver must be tuned to the appropriate frequency. 2. The glideslope signal must be valid; no flag. 3. The autopilot must be in NAV/APR/ ALT modes. 4. The aircraft must be 60% or more below the GS centerline during the approach to the intercept point, and within 50% needle deviation of the localizer centerline at the point of intercept, usually the outer marker. 4-22 2nd Ed: Nov 01, 01 SYS 60-2 POH NOTE: GS arming will occur when the above conditions have existed for 10 seconds. Illumination of the GS annunciator will occur, indicating arming has been accomplished. The ALT annunciator remains on. GS capture is indicated by extinguishing of the ALT annunciation at GS intercept.

Therefore, you should also monitor the capture of the glideslope and be ready to manually activate the GS on the autopilot using the following:

4.2.2.4 Manual Arm/Automatic Capture If approach vectoring locates the aircraft above or too near the GS centerline at the intercept point, usually the outer marker, it becomes necessary to execute a manual arming of the GS. This is done by: 1. Pressing the ALT switch once if operating in the altitude hold mode. 2. Pressing the ALT switch twice if operating in the VS mode. Once capture is achieved, the GS annunciation will illuminate, and the ALT annunciation will extinguish. NOTE: If it becomes necessary to establish a holding pattern at the outer marker, automatic glideslope arming can be disabled by pressing the NAV switch a second time while in the NAV/APR mode. The GS annunciator will flash, and the Disable (DSBL) annunciator will illuminate, to indicate that the GS mode is disabled. To reestablish GS arming, press the NAV mode switch again. The DSBL condition annunciator will extinguish, the GS annunciator will cease to flash.

3.  Stabilized on the glideslope

  • STEC  -  finger on the AP disconnect
  • HSI - monitor the approach
  • GPS - activate the approach so that you may switch GPS directed missed procedure if necessary 

4.  Missed approach procedure.

  • STEC - HDG Mode, turn to 90 degrees
  • NAV 2 - watch for the needle to center, then track it outbound on 58 degrees by turning the heading bug.
  • GPS - stay in suspended mode until you have climbed to 3000 feet and you are within 20 degrees of the outbound of 58 degrees.  This should keep your GPS from flaking out.  At this point, unsuspend the GPS, verify that the correct leg and fix are active (COSKA), AND that you have good situational awareness, then do the following:
    • verify that the GPS reverted to GPS mode in the unsuspend process.
    • activate GPSS and fly the missed with the GPS 
    • set NAV 2 if necessary to fly the approach with it as a backup (I would set up both VOR's and flip flop the frequency to determine my fix so that I could leave NAV 1 st up for the ILS assuming that I planned to try the approach again)

My goodness, that's a lot and I am certain I missed some detail.  Moreover, as I mentioned, I have never used your setup AND I am not a CFII....Grab a safety pilot on a VMC day and try it for yourself. I guess you can’t arm heading/nav to intercept the gps part of the missed to the hold?

 

Alex

Man! You did some work here, I owe you a cheeseburger! My brain freeze on this approach seems to be when to switch to gpss. I like your use of the second vor to get to COSKA. Your right, a very busy time. If you set the hsi to 058 and unsuspend and hit gpss while on your way to the 058 radial on the 90 heading, would it track to the hold? Can you hit heading/nav to intercept and track the inbound to the hold? I’ve been wanting to try this the last two times out and NorCal couldn’t accommodate.

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M20F-1968 Veteran

M20F-1968

Posted
Posted
36 minutes ago, alextstone said:

Let me preface this by stating that do not have the same equipment you do, nor am I a CFII...however I am willing to pretend I know what I am talking about from the comfort of my living room in relative anonymity some distance away from you.  In other words, try this at your own risk....

Five phases of the approach:

1.  Briefing the approach and pre-loading frequencies, etc.

  • Current weather is above published AND personal minimums
  • Tower is open (approach is NA if not)
  • Brief NOTAMS
  • Review the Missed Procedure (notice that there are two possible missed approach holding patterns - each with the same fix but different cross references as to DME)  
  • Set up the Equipment:
    • STEC - HDG Mode, GPSS OFF
    • 530 GPS - Load ILS approach with "Vectors to Final", VLOC mode
    • HSI - Heading Bug set to current flight path.  CDI set to needle head pointing to 221 degrees (inbound ILS course)
    • NAV 2 - Here's where you will get differing opinions... I prefer to have the VOR for the missed set up and to use it initially, thus taking the GPS out of the missed equation until I am comfortably stabilized.  So, I would set NAV 2 to 115.2 SAC with the compass rose on the CDI set to 58 degrees (the outbound radial toward the fix)  During the Missed, you will have more to do than just fly that radial, but at least you have a starting point (this of course is a backup to the GPS, more on that later)

2.   Vectors.

Your autopilot appears to have "Dual Mode" which means that you can Press both HDG and NAV together within 45 degrees of the final approach course while leaving the AP in HDG mode, thus arming NAV while still staying in HDG mode (from the STEC 60-2 manual):

4.2.1.6 Dual Mode Intercept NOTE: During operations with an HSI, simultaneous activation of both the HDG and NAV modes will provide selected angle intercepts. In flying a radial or localizer intercept, the autopilot will follow the heading bug until the aircraft reaches the proper on course turn point. It will then switch from HDG to NAV mode automatically. Selected angle intercepts may be used during VOR, localizer front course and back course (REV) operations. Localizer intercept angles greater than 45º usually result in some course overshoot, depending on the distance from the station and speed of the aircraft. Therefore, angles greater than 45º are not recommended.

  • STEC - HDG AND NAV pressed

2.  Intercepting the Localizer and glideslope

  • STEC - monitor to verify a switch to NAV then APR upon intercept of the localizer.  Also, realize that for the GS to couple automatically you MUST be below the GS centerline as per the manual:

4.2.2.3 Intercepting and Coupling the Glideslope To arm the automatic glideslope (GS) capture function, the following conditions must be met: 1. NAV receiver must be tuned to the appropriate frequency. 2. The glideslope signal must be valid; no flag. 3. The autopilot must be in NAV/APR/ ALT modes. 4. The aircraft must be 60% or more below the GS centerline during the approach to the intercept point, and within 50% needle deviation of the localizer centerline at the point of intercept, usually the outer marker. 4-22 2nd Ed: Nov 01, 01 SYS 60-2 POH NOTE: GS arming will occur when the above conditions have existed for 10 seconds. Illumination of the GS annunciator will occur, indicating arming has been accomplished. The ALT annunciator remains on. GS capture is indicated by extinguishing of the ALT annunciation at GS intercept.

Therefore, you should also monitor the capture of the glideslope and be ready to manually activate the GS on the autopilot using the following:

4.2.2.4 Manual Arm/Automatic Capture If approach vectoring locates the aircraft above or too near the GS centerline at the intercept point, usually the outer marker, it becomes necessary to execute a manual arming of the GS. This is done by: 1. Pressing the ALT switch once if operating in the altitude hold mode. 2. Pressing the ALT switch twice if operating in the VS mode. Once capture is achieved, the GS annunciation will illuminate, and the ALT annunciation will extinguish. NOTE: If it becomes necessary to establish a holding pattern at the outer marker, automatic glideslope arming can be disabled by pressing the NAV switch a second time while in the NAV/APR mode. The GS annunciator will flash, and the Disable (DSBL) annunciator will illuminate, to indicate that the GS mode is disabled. To reestablish GS arming, press the NAV mode switch again. The DSBL condition annunciator will extinguish, the GS annunciator will cease to flash.

3.  Stabilized on the glideslope

  • STEC  -  finger on the AP disconnect
  • HSI - monitor the approach
  • GPS - activate the approach so that you may switch GPS directed missed procedure if necessary 

4.  Missed approach procedure.

  • STEC - HDG Mode, turn to 90 degrees
  • NAV 2 - watch for the needle to center, then track it outbound on 58 degrees by turning the heading bug.
  • GPS - stay in suspended mode until you have climbed to 3000 feet and you are within 20 degrees of the outbound of 58 degrees.  This should keep your GPS from flaking out.  At this point, unsuspend the GPS, verify that the correct leg and fix are active (COSKA), AND that you have good situational awareness, then do the following:
    • verify that the GPS reverted to GPS mode in the unsuspend process.
    • activate GPSS and fly the missed with the GPS 
    • set NAV 2 if necessary to fly the approach with it as a backup (I would set up both VOR's and flip flop the frequency to determine my fix so that I could leave NAV 1 st up for the ILS assuming that I planned to try the approach again)

My goodness, that's a lot and I am certain I missed some detail.  Moreover, as I mentioned, I have never used your setup AND I am not a CFII....Grab a safety pilot on a VMC day and try it for yourself.

 

Alex

This is essentially correct, but let me add a few things that caught me up while I was learning this system:

1) When flying an ILS front course, or for that matter an ILS back course, the inbound course direction must be set on the course selector.  Your equipment may do this automatically (but check that it does otherwise you will need to set it manually).  

2) The NAV mode is used for tracking inbound on the front course and outbound on the Back course.  The REV button is used for tracking inbound on the back course and outbound on the front course.

3) Once you load or load and activate the ILS approach, you will need to switch the ILS NAV frequency from standby to the active NAV frequency.

4) Verify that you equipment switches to VLOC.  If it does not do this, you will need to do it manually.

5) You can intercept the ILS in one of 2 ways:  1) Use HDG and ALT with your heading bug, and or hand fly the plane to intercept.  When you are 60% below the glideslope and within 50% deviation of the Localizer, just hit NAV.  The autopilot wit=ll look for the Localizer and glide slope.  When established on the Localizer and glideslope, ALT will be off and GS will be illuminated - or  2) you can press HDG and NAV together, then ALT.  For all S-TEC autopilots, you have to establish a roll command first before it will accept a pitch command.  When the Localizer is found, HDG will be off and only NAV will be lit as the roll command.  ALT will extinguish and GS will illuminate when the GS is coupled.

6) If you come in too high (even though you are below the glideslope but just too close to it) the autopilot may try to couple to the secondary glideslope above the real one.  Watch out for this as the autopilot may just keep raising the nose and put the airplane into a stall.  It is important that you watch your HSI when you expect the GS to couple and you are sure that the autopilot is following it down.

7) Recognize that the ALT button is used to manually arm the GS if it does not arm when you intercept, BUT, the NAV button is used to disengage the GS and pressing the NAV button again re-engages the GS.  When NAV is pressed to disengage the GS, DISABLE will illuminate and GS will flash.  When NAV is pressed again, DISABLE will go out and GS will stop flashing.

8) On missed approach, when you press activate missed, the missed approach leg should be seen on your map.  If you press HDG on the autopilot and GPSS on the GPSS/HDG switch, you will activate the GPS steering which should follow the magenta line to your missed approach.  You can hand fly the vertical speed or put the autopilot in VS.  At this point, I usually hand fly the vertical speed as there are enough transitions you want to be sure you are climbing and on the Missed magenta line.

John Breda  

 

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M20F-1968 Veteran

M20F-1968

Posted
Posted

I should add that I have GTN-750 and GTN-650 with a G600.  On missed, the unit sees the missed approach course as a GPS track in GPSS steering.

It took me awhile to recognize that the GPSS/VLOC(HDG) button only work with the STEC 60-2 in NAV mode.  So, when you go missed, you press NAV on the autopilot 

and GPSS on the GPS/NAV button.  This puts you in GPSS mode.  If you press HDG on the autopilot and VLOC(HDG) on the GPSS switch, you are in HDG mode only and following the HDG bug.  

In order to intercept the VOR inbound for the hold using other than GPSS guidance, you will need to put in the VOR frequency and radial in your second Nav/Com when you set-up the approach and switch over tho that.  I have my second NAV/COM wired so it can drive the G600 and NAV-2, or it can drive (as it is hard-wired to) a Garmin 106 Glideslope/VOR indicator which is always there as a back-up.

John Breda

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carusoam Grand Master

carusoam

Posted
Posted

Thank you gents for taking the time to help an MSer out... :)

Now I have to see if I remember all the buttons on my set-up...

Best regards,

-a-

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tmo Veteran

tmo

Posted
Posted

Lots and lots of "thank you"s to all of you for this aviation gem in these challenging times.

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