TTTTT on a GPS approach with PT

W

Walboy

Line Up and Wait
Joined
Feb 11, 2014
Messages
503
Display Name
Display name:
Walboy
.
 
Last edited:
The Five Ts may no longer apply in your case.

But even for a GPS or LOC approach, I always twist to the course to keep the habit pattern for that dreaded VOR approach.

Plus it's a ready heading reference.
 
I don't use the "Five Ts" but if you're asking what the OBS setting on the NAV head should be for a GPS approach, it should normally be set to the desired course for the current leg of the approach, same as during the enroute phase. At least, that is what I've always done, and what my GPS commands my HSI course pointer to be set to (via auto-slew).
 
Just let the GPS work its magic, don't ask questions!
 
For certain autopilots tracking the GPS via the needle (i.e., no GPSS roll steering interface), it will not track properly unless the course is dialed in on the course pointer for an HSI or the heading bug for a regular HI. In addition, failing to set the course on the CDI OBS or the HSI course pointer when the CDI button on the GPS is set to GPS generates a message that does not go away until you set it properly. So there's still some twisting to do on a GPS approach. Also, I teach my trainees to time it anyway, both to maintain the habit and as a backup in case you lose the satellites during the approach (it can happen, and has happened to me once or twice in 15 years of flying GPS approaches).
 
Normally the CDI on GPS mode will automatically choose the correct course between the two waypoints. So you wouldn't have to 'twist' it in this case. If you are hand-flying then you just fly the CDI like normal. You can mentally verify that your heading is generally on-course, taking wind into account.
 
Ron Levy said:
For certain autopilots tracking the GPS via the needle (i.e., no GPSS roll steering interface), it will not track properly unless the course is dialed in on the course pointer for an HSI or the heading bug for a regular HI. In addition, failing to set the course on the CDI OBS or the HSI course pointer when the CDI button on the GPS is set to GPS generates a message that does not go away until you set it properly. So there's still some twisting to do on a GPS approach. Also, I teach my trainees to time it anyway, both to maintain the habit and as a backup in case you lose the satellites during the approach (it can happen, and has happened to me once or twice in 15 years of flying GPS approaches).
Click to expand...

Since they don't show time on these approaches any more do you have the trainee bust out a whiz wheel and figure it out ?
 
BillTIZ said:
The Five Ts may no longer apply in your case.

But even for a GPS or LOC approach, I always twist to the course to keep the habit pattern for that dreaded VOR approach.

Plus it's a ready heading reference.
Click to expand...

I have a (old school) HSI. I've got to twist the course arrow even on LOC and GPS approaches. Obviously "time" and "turn" is right out the window though.
Even on the old VOR navigation, there are times when you don't have to do one or more of the T's.
 
If you're hand flying a GPS approach, just follow the direct track to the waypoint. The plate will tell you directions from point-to-point. There is no need for timing because the GPS knows where you are at all times and reports that to you. The only reason you time on an ILS is because should you lose your FAF cross radial (if you even have one to begin with) you would need to know how far along you are. Even on a VOR or ILS approach, when you're using GPS overlay, that is a better cross-reference than using the stopwatch... but I would still use both.

I was never trained with the 5 T's specifically, but was trained using steps that would include those. I found (and still do) find 5 T concept confusing.
 
If you are using the Ts, they are just a prompt for you to be aware that there are a series of tasks that must be considered every time you cross a fix. They are not items that must be done in a certain order, nor are they items that must be done crossing every fix on every approach. They are just things to think about in preparation for reaching the next fix. If you found them helpful to begin with, they are just as helpful with GPS approaches.

There is a lot to be said for consistent operating procedures. Far better to take a nanosecond to think to yourself "no timing when I reach the next fix" on your GPS approach than to forget timing altogether on that occasion when circumstances require you to fly a timed VOR approach.
 
The PIC guy who did my rating gave some stickers that PIC produced with the 5-Ts on it but I can't remember a whole lot of emphasis on them in the training. Far more useful was the little chart of power settings/airspeeds/rate of descent for the various aspects of IFR flight. Very handy. I've pretty much committed them to memory now, but back then it was handy and if I switched planes, I'd fill out a new chart.
 
Walboy said:
Let me start by first saying I have never flown a GPS approach. I am studying as much as I can before I meet with a CFII for instruction and an IPC after having installed a gps in my airplane.

Using the GPS RWY 5 approach to KCGZ linked below and assuming a parallel entry to the hold, when crossing the IAF and running through the five Ts, what is the correct procedure for the "twist" part? I know turning the OBS knob has no effect on the needle for a GPS approach, but the flight supplement manual says I must use the external CDI for course guidance, not the magenta line or the CDI built into the GTN.

http://155.178.201.160/d-tpp/1504/06656G5.PDF

I think I know the answer, but would like to hear from someone with experience.
Click to expand...

That is a really old IAP. IAF/FAFs were "outlawed" in design criteria some 15 years ago. I thought they were all gone by now.
 
Walboy said:
It's clear I have done an awful job asking my question.

Let me try again.

Let's pretend the approach I presented is a VOR approach that requires a parallel entry to a hold in lieu of a procedure turn. I have no moving maps or any other device for course guidance other than my trusty CDI. Upon arrival to the IAF, I was taught to "twist" the OBS knob to 198 with a FM indication. Course corrections could be read off the CDI by flying to the needle just like any outbound radial tracking. The desired course is read at the top of the CDI. At the end of the prescribed time, I turn inbound and "twist" to 018 with a TO indication and again fly to the needle. No autopilot, just simple hand flying.

Now, change the course guidance from a VOR to GPS. Everything else is the same. No moving maps or magenta line to look at. Only the trusty CDI. What is the correct procedure to use to keep the needle centered? How do you know which direction to turn for course correction?
Click to expand...
I gotcha. The VOR allows you to choose orientation - To or From - inbound course or outbound course. GPS courses are pretty much "To" only. But if you load and activate the approach, you are going to receive course guidance from the GPS itself. IOW, if you have loaded and activated the approach, the system will (depending) ask you if you are going to do the PT and if so, give you direct course guidance to fly 198, do a standard barbed PT, and bring you back to intercept the 018 inbound. You will twist the CDI accordingly.

But it sounds like you are not loading and activating the approach, which brings be back to my "depending." If you are not, does it mean you are not using an approach-certified GPS so it doesn't have the capability of loading the approach in full?

What unit are you using?
 
With my gps, a GX50, depending on my angle of intercept of the IAF, I would have to punch the OBS hold button, or it would light for me. in any event, I then twist in the inbound course and enter it into the gps, the pointer would point to the station, and, having an hsi, the little airplane would show me where I was in relation to the entered course. If I had a cdi, the needle would be reverse sensing,as I am flying away from the waypoint with the arrow pointing to. Once established inbound, the needle senses normally, I would release the OBS hold and the gps sequences to the next waypoint once the faf is crossed, and the appch active lights go on.
So it's pretty much like flying a vor approach.
 
Last edited:
Art VanDelay said:
Since they don't show time on these approaches any more do you have the trainee bust out a whiz wheel and figure it out ?
Click to expand...
Pretty much all my trainees can divide distance by 2 (for 120 knots) or 1.5 (for 90 knots) in their heads. And since it's just an emergency backup, "close" is good enough for deciding when to start the missed approach turn.
 
midlifeflyer said:
If you are using the Ts, they are just a prompt for you to be aware that there are a series of tasks that must be considered every time you cross a fix. They are not items that must be done in a certain order,
Click to expand...
We've found that when folks do them out of order, they either forget something or start calling the tower to report the FAF before they start the clock timing the approach or mess up the turn (in either heading or altitude) because they're playing with the CDI when they should be making a level standard-rate turn. So, we are pretty firm about saying all the T's every time in order.

Of course, YMMV, but this is what we at PIC have learned in 35 years of specializing in instrument training.
 
The DTK (desired track) field on your GPS (if you're using Garmin) tells you what track your course guidance is based on. Set your OBS to this.

This is pretty helpful if you're flying an HSI, so you don't get an effect similar to reverse sensing.
 
Ron Levy said:
We've found that when folks do them out of order, they either forget something or start calling the tower to report the FAF before they start the clock timing the approach or mess up the turn (in either heading or altitude) because they're playing with the CDI when they should be making a level standard-rate turn. So, we are pretty firm about saying all the T's every time in order.

Of course, YMMV, but this is what we at PIC have learned in 35 years of specializing in instrument training.
Click to expand...

I'm a big fan of the 5 T's as well.

It's a checklist, like GUMPS or anything else. It's there to make sure you don't miss anything. It's not that hard, even for someone with experience, to miss one of the many things you have to remember to do when flying instruments.
 
Walboy said:
Let's pretend the approach I presented is a VOR approach that requires a parallel entry to a hold in lieu of a procedure turn. I have no moving maps or any other device for course guidance other than my trusty CDI. Upon arrival to the IAF, I was taught to "twist" the OBS knob to 198 with a FM indication. Course corrections could be read off the CDI by flying to the needle just like any outbound radial tracking. The desired course is read at the top of the CDI. At the end of the prescribed time, I turn inbound and "twist" to 018 with a TO indication and again fly to the needle. No autopilot, just simple hand flying.
Click to expand...
That's contrary to what we at PIC teach. We teach people to fly the outbound leg of any holding pattern entry (direct, parallel or teardrop) as a heading, not a course to be tracked, and once rolled out on the outbound heading to twist the CDI to the inbound course. We do that to avoid twisting while turning (which often results in wandering off altitude or bank angle or even flying through the intercept heading) and to ensure that the inbound course is dialed in correctly while making the inbound turn so the intercept is easier.

Now, change the course guidance from a VOR to GPS. Everything else is the same. No moving maps or magenta line to look at. Only the trusty CDI. What is the correct procedure to use to keep the needle centered? How do you know which direction to turn for course correction?
Click to expand...
When performing a holding pattern in lieu of procedure turn, the GPS automatically cycles to the inbound course as soon as you cross the holding fix. As a result, the CDI will show your deflection off the inbound course, not the holding pattern entry course/heading. For that reason, it's probably best to ignore the CDI needle during the outbound leg of the holding pattern entry. Note that for parallel entries, there is no requirement to track the inbound course outbound -- it's OK to be off that course line (usually on the nonholding side) during the outbound parallel leg.

The reason I ask this, I was "experimenting" on my own before meeting with a CFII. I used the technique described above. When flying outbound, turning toward the needle increased the needle deflection.
Click to expand...
Yup -- because the needle deflection is based on the inbound course, not the holding pattern entry heading. Essentially, you're in the same situation you'd be trying to fly a localizer backwards.

So it seems to me that in a hold in lieu of a procedure turn the CDI indication in the GPS mode is relative to the course to the next fix.
Click to expand...
No, just the inbound course back to the holding fix.

In other words, it seems like this is similar to a BC on a localizer (reverse sensing).
Click to expand...
Technically, it's not really "reverse sensing", but you have the general concept.

I figured there must be some sort of standard technique to use in this case.
Click to expand...
There is -- on a holding pattern entry outbound leg, ignore the needle and just fly heading (or track, if you have a GPS).
 
OverTQ said:
The DTK (desired track) field on your GPS (if you're using Garmin) tells you what track your course guidance is based on. Set your OBS to this.
Click to expand...
And for a GTN750, when you depart the holding fix outbound for the entry, that will be the inbound course for the holding pattern.

This is pretty helpful if you're flying an HSI, so you don't get an effect similar to reverse sensing.
Click to expand...
Still doesn't matter if you just fly heading on the outbound leg of a holding pattern entry. They've put plenty of space around the holding pattern to allow for like 90% worst-case wind and the highest IAS allowed.
 
Ron Levy said:
Still doesn't matter if you just fly heading on the outbound leg of a holding pattern entry. They've put plenty of space around the holding pattern to allow for like 90% worst-case wind and the highest IAS allowed.
Click to expand...

Understood, headings not courses on the outbound portions of the hold/hold entry.

I'm just speaking in general; it's good practice, I believe, to monitor the DTK and keep your OBS set to it.

One thing I'm not quite sure of is why DTK will often differ from the published course on an IAP by a few degrees. Seems to happen even on GPS approaches, where something like VOR twist wouldn't be a contributing factor.
 
BillTIZ said:
The Five Ts may no longer apply in your case.

But even for a GPS or LOC approach, I always twist to the course to keep the habit pattern for that dreaded VOR approach.

Plus it's a ready heading reference.
Click to expand...

That's why I do it.
 
OverTQ said:
Understood, headings not courses on the outbound portions of the hold/hold entry.
Click to expand...
:thumbsup:

I'm just speaking in general; it's good practice, I believe, to monitor the DTK and keep your OBS set to it.
Click to expand...
Agreed, with the only exception being when tracking a localizer backwards (either inbound on the back course or outbound on the front course). In that case, leave the OBS (or HSI course pointer) set to the forward direction.

One thing I'm not quite sure of is why DTK will often differ from the published course on an IAP by a few degrees. Seems to happen even on GPS approaches, where something like VOR twist wouldn't be a contributing factor.
Click to expand...
If we're talking anything VOR-based or localizer-based, it's usually because the declination of the navaid doesn't keeps up with the continuing changes in variation. For a GPS-based procedure, :dunno:, but it's not worth worrying about -- just set the OBS or course pointer to the DTK and press on.
 
Walboy said:
Here is how I'm going to handle it in the future. Once I cross the fix outbound, I will dial in the inbound course on the CDI. Since the OBS flag shows a TO indication and we're flying away FROM the fix, the heading would be obtained by looking at the possible courses on the two lower quadrants of the CDI and flying to the needle. Pretty simple.
Click to expand...
That is the exact technique I teach for tracking a localizer backwards with a CDI. And when you do it this way, you realize that there is no "reverse sensing" -- the CDI needle is still giving you the correct heading to fly, although you have to look at your heading indicator to decide which way to turn to get to that heading.
 
Ron Levy said:
That is the exact technique I teach for tracking a localizer backwards with a CDI. And when you do it this way, you realize that there is no "reverse sensing" -- the CDI needle is still giving you the correct heading to fly, although you have to look at your heading indicator to decide which way to turn to get to that heading.
Click to expand...

A little tip on that, you turn up to the left, and down to the right. It also helps flying a whiskey compass or old flat disk type AN DG.
 
Ron Levy said:
We've found that when folks do them out of order, they either forget something or start calling the tower to report the FAF before they start the clock timing the approach or mess up the turn (in either heading or altitude) because they're playing with the CDI when they should be making a level standard-rate turn. So, we are pretty firm about saying all the T's every time in order.

Of course, YMMV, but this is what we at PIC have learned in 35 years of specializing in instrument training.
Click to expand...
I don't disagree with the result you describe. Once an order is settled on, the order should be maintained as a way of developing an SOP ingraining a habit that is not likely to be broken. A pilot who uses any mantra as a mental checklist is going to make mistakes if he or she keeps switching the order around.

What I am talking about is the initial decision. Yes, of course there is logic to an order that generally prioritizes "aviate" over" navigate" over "communicate," as with just about anything we do in aviation (which I notice Time before Throttle violates ;)). But when I see discussions and religious arguments about whether Turn is properly before Time or when Twist must be done before or after hitting the Timer or all hell will break loose, I just have to shake my head in wonderment.
 
midlifeflyer said:
I don't disagree with the result you describe. Once an order is settled on, the order should be maintained as a way of developing an SOP ingraining a habit that is not likely to be broken. A pilot who uses any mantra as a mental checklist is going to make mistakes if he or she keeps switching the order around.

What I am talking about is the initial decision. Yes, of course there is logic to an order that generally prioritizes "aviate" over" navigate" over "communicate," as with just about anything we do in aviation (which I notice Time before Throttle violates ;)). But when I see discussions and religious arguments about whether Turn is properly before Time or when Twist must be done before or after hitting the Timer or all hell will break loose, I just have to shake my head in wonderment.
Click to expand...

I realize that to do so is heretical, but I agree with you that the sequence is not that critical and that this whole thread is much ado about very little.

Bob Gardner
 
bobmrg said:
I realize that to do so is heretical, but I agree with you that the sequence is not that critical and that this whole thread is much ado about very little.

Bob Gardner
Click to expand...
Not so much the thread itself. The OP asked a very good question about his transition from VORs to GPS. And Ron's answer about flying headings for a PT (barbed or HILO) and leaving/placing the nav unit/CDI (whatever it is) on the inbound course for the eventual inbound intercept was spot on.

And, hey, at least we didn't hear about the bastardization of one of the very, very few mnemonics that are actually useful into into 6 or 7 or 8 Ts.
 
midlifeflyer said:
I don't disagree with the result you describe. Once an order is settled on, the order should be maintained as a way of developing an SOP ingraining a habit that is not likely to be broken. A pilot who uses any mantra as a mental checklist is going to make mistakes if he or she keeps switching the order around.

What I am talking about is the initial decision. Yes, of course there is logic to an order that generally prioritizes "aviate" over" navigate" over "communicate," as with just about anything we do in aviation (which I notice Time before Throttle violates ;)). But when I see discussions and religious arguments about whether Turn is properly before Time or when Twist must be done before or after hitting the Timer or all hell will break loose, I just have to shake my head in wonderment.
Click to expand...
I see your point. However, from PIC's perspective:

  1. PIC wants all its instructors teaching the same way so if you start with one and finish with another (or come back for refresher training a year later), you'll be singing out of the same hymnal throughout the service (or when you come back to church next Sunday).
  2. It's hard for instructors to change the procedures they teach for each different trainee (not impossible, but not easy, either)
  3. PIC's can't alter its printed training materials for each different trainee/instructor.
So, we PIC'ers all do it as Peter Dogan wrote it 35 years ago when he started the company, which is "Turn-Time-Twist-Throttle-Talk" (just like the printed sticker we put on the panel on Day 1). One might find that some other order is no worse, but I can't see any other order being better.
 
Last edited:
Ron Levy said:
I see your point. However, from PIC's perspective:

  1. PIC wants all its instructors teaching the same way so if you start with one and finish with another (or come back for refresher training a year later), you'll be singing out of the same hymnal throughout the service (or when you come back to church next Sunday).
  2. It's hard for instructors to change the procedures they teach for each different trainee (not impossible, but not easy, either)
  3. PIC's can't alter its printed training materials for each different trainee/instructor.
Click to expand...
And if you read what I wrote, you know I agree that makes perfect sense.

With one possible exception - if someone came to you who had already learned and was using a slightly different order and your first flights showed it worked, would you force the pilot to switch?
 
midlifeflyer said:
And if you read what I wrote, you know I agree that makes perfect sense.
Click to expand...
:yes: I was just trying to explain why PIC instructors are supposed to always teach that one particular version of the 5T's.

With one possible exception - if someone came to you who had already learned and was using a slightly different order and your first flights showed it worked, would you force the pilot to switch?
Click to expand...
No. On a finish-up course, we start by evaluating their skill and proficiency, and if what they're doing is working, we don't try to change it. However, if they come to us with no system at all (which almost always means it's not working), we will get them organized using our standard 5T's.

And on those finish-up courses, the two things I see most often for those who are struggling are lack of organization (i.e., no 5T's or anything like it for getting things done) and not slowing down before starting the approach (e.g., approaching the FAF at cruise speed/configuration). Get them slowed down and organized, and everything falls into place.
 
Last edited:
Ron Levy said:
No. On a finish-up course, we start by evaluating their skill and proficiency, and if what they're doing is working, we don't try to change it.
Click to expand...
Figured that would be the case. I sometimes (semi-)joke about people having religious views about flying in a certain way but I do believe in one Cardinal Sin for flight instructors - changing something that works just because it's different from what they teach (I was the recipient of that a long time ago when I was a fledgling pilots and I never forgot how difficult it was to recover from it)

However, if they come to us with no system at all (which almost always means it's not working), we will get them organized using our standard 5T's.
Click to expand...
Makes sense. I may be sort of known for my dislike of mnemonics but the 5Ts is the exception. It was an integral part of my own training and my re-introduction to real IFR flight. And, btw, I do teach the Dogan order (since it's the one I learned) . I didn't do PIC but I did use his terrific instruction book.

And on those finish-up courses, the two things I see most often for those who are struggling are lack of organization (i.e., no 5T's or anything like it for getting things done) and not slowing down before starting the approach (e.g., approaching the FAF at cruise speed/configuration). Get them slowed down and organized, and everything falls into place.
Click to expand...
We not only agree, but I see the exact same two things often enough on an IPC or just some recurrent instrument dual.
 
Walboy said:
Now...anyone want to suggest a better way to brief an approach rather than using AMICEATM? That is the way I learned, but I'm open to suggestions for something that flows a little better.
Click to expand...

Long before you hit the IAP, brief it top to bottom, left to right. Setting the aircraft up (frequencies and such) as you go along. Brief everything on the plate that pertains to you (which is pretty much everything besides the minimums for other categories).

If you get interrupted, stop, and come back to the same place on the plate that you left off and continue.
 
Walboy said:
Now...anyone want to suggest a better way to brief an approach rather than using AMICEATM? That is the way I learned, but I'm open to suggestions for something that flows a little better.
Click to expand...
Yes. I don't use or teach any mnemonic so will automatically say "anyhting is better than AMICEATM (whatever the heck that is) except another mnemonic." I'm absolutely convinced a briefing mnemonic is not only useless but potentially harmful since is it is always better to SMALS.

The briefing strip on both FAA and Jepp charts was the result of much study in the way pilots brief approaches. So use it.

My own methodology is to select the approach and confirm the right one (surprise! You can't do that without listing to ATIS or AWOS or checking the weather in some way). And then go to the plan view to select an appropriate IAP for my direction of travel.

Then it's simply a matter of following the briefing strip to set up what has not already been set up, and then reviewing the anticipated course of flight and altitudes from approaching the approach through the missed.

If you think about it for 10 seconds, that will cover everything you need and, better yet, it will be because you understand the approach rather than fill the spaces for some mnemonic.

And no, that doesn't take a second longer than following a mnemonic. Much faster, in fact.
 
Walboy said:
Thanks Ron for chiming in on this thread. I'm glad you pointed out the PIC way of doing things.
Click to expand...
Happy to help -- and remember us next time you need some refresher training. :wink2:

I went out and flew two practice approaches today both with holds in lieu of PT, one using a VOR and the other using GPS. I used the technique Ron suggested which is dial "twist" in the inbound course when crossing the fix outbound so that there is no "twisting" whilst turning inbound. I like this technique a lot better and it provides consistency no matter what the navigation source is.

The 5 T's work great for me and I always recite them in the same order, everytime.
Click to expand...
Those familiar with the Aviation Instructors Handbook will recognize the Law of Exercise at work here -- do something the same way all the time, and you get real good at it.

Now...anyone want to suggest a better way to brief an approach rather than using AMICEATM? That is the way I learned, but I'm open to suggestions for something that flows a little better.
Click to expand...
I have no idea what "AMICEATM" means, but, like OverTQ, I brief it off the chart - top to bottom, left to right. Works every time, and I don't have to think about what all those letters mean.
 
You must log in or register to reply here.
Back
Top