Scenerio: No RAIM on an ILS approach and instructed to hold at the outer marker.
According to the STEC 55 manual, pressing NAV a second time will prevent arming of the GS allowing you to fly a hold with autopilot using NAV and ALT. But according to the SR20 POH STEC 55X supplement (I can’f find the STEC 55X manual online) pressing NAV a second will put the autopilot in GPSS mode. So how do I do the above described hold?
Art,
I believe you are going to have to do it the ‘old fashioned way’ and use the VLOC mode on the GNS 430 (which you should be in anyway), your CDI, and the heading bug to make your turns while the A/P is in HDG mode. You could switch to NAV mode on the A/P on your inbound leg if the hold pattern is aligned with the localizer provided you are lined up fairly well. If not, the intercept the A/P will attempt will probably not allow you to fly an appropriate inbound leg. After tracking inbound in NAV mode on the localizer, you would have to switch to HDG mode, make your 180 outbound and start your stopwatch. Since everything you are doing is not assisted or overlayed with GPS info, you are not going to be able to get holding pattern course guidance. In fact, the GNS430 does not output course guidance to the A/P for holding patterns or procedure turns even when is GPS mode, but it does depict them on the moving map when an approach is loaded. I understand holding patterns and procedure turns will be added to the outputs of many GPS navigators soon, but I don’t know if this includes the GNS430.
My question was specifically about how to stop GS arming. I did send this same question to the STEC support this morning and I got an answer this afternoon. See the following:
When holding at the outer marker with a System 55X, automatic glide slope arming can be disabled by pressing the APR button once while in the NAV/APR Mode. The GS annunicator will flash continuously and ALT will remain
annunicated on the programmer indicating glide slope is disarmed. On the optional remote annunicator if so equipped, the GS annunicator will also flash continuously, and the ALT and DSBL annunicators will illuminate, indicating the GS Mode is disabled. When you are ready to leave the holding pattern and continue with the ILS all you have to do to arm glide slope again is push the ALT button once and ALT/GS will illuminate simultaneously indicating glide slope is now armed.
“On the optional remote annunicator if so equipped”
Does the Cirrus 22 with the 55 come equipped with the remote GS annunciator?
Well, Art, the answer you received from S-TEC is not complete in its response to the manner in which you phrased your question. They did not tell you that you cannot fly the holding pattern in NAV mode. In fact, they lead you to believe you can fly the hold in NAV mode. The GNS430 does not provide this course guidance in GPS or VLOC mode to the A/P.
The answer you got from S-TEC was a generic answer not specific to the installation in the SR20/22. Half of the challenge of getting the information you need is in asking the right question. Your question in your first post was, specifically, “So how do I do the above described hold?” I thought I provided a complete answer. You could have left out all of the references to RAIM, GPSS, etc. because anything related to GPS is completely irrelevant to your question. Those references, along with the statement that you could fly a hold with NAV and ALT, implied a misunderstanding of how the GNS430 & the S-TEC 55X operate together. I simply tried to shed some light on the subject for you.
Finally, S-TEC went to great pains to let you know what would be displayed on the remote annunciator that you will not be getting in your new Cirrus. They also misspelled it, five times.
Greg
No. I am not sure what a “remote GS annunciator” is. The remote annunciator that STec is talking about is a small panel with a lcd screen that annunciates autopilot modes.
They did not tell you that you cannot fly the holding pattern in NAV mode. In fact, they lead you to believe you can fly the hold in NAV mode. The GNS430 does not provide this course guidance in GPS or VLOC mode to the A/P.
Unless I am missing something, it sounds like I can fly the hold without the GPS while in ALT mode, just by tuning the ILS, pressing APR once to track the localizer inbound, and a second time disable GS arming. When I cross the outer marker I press HDG and set the HDG bug to the outbound leg. At the end of 1 minute, I can just press APR 2 times and I will automatically fly the inbound leg. The key is to press APR 2 times. without the 2nd press the GS would arm and I would begin descending after I intercept the glide slop.
This is a slightly different technique than I described above in my original post and would work just fine. However, the idea of a holding pattern is to modify the outbound leg to achieve a 1 minute leg inbound before crossing the fix. Doing the pattern the way you have described will command the A/P to fly a 45 degree intercept to the inbound course leg. This could affect the timing of your inbound leg by making it more of a guess as to when to start your timing. Also, if the wind is from the other side of the final approach course and you are flying the holding pattern slowly (like you normally would be doing), the 45 degree intercept course could lay across the inbound leg (localizer course) at or past the fix unless you nailed the wind correction angle on your outbound leg. The A/P would be better employed in the heading mode in this scenario.
Greg
Doing the pattern the way you have described will command the A/P to fly a 45 degree intercept to the inbound course leg.
But if I selected my outbound course properly by the time the inbound turn reaches the heading for the 45 degree intercept I will be close enough to the inbound course for the AP to just keep turning.
Do it the way you want.
Greg