THE T'S

You're on a non-precision approach and you arrive at the final approach fix; like as not, you start in on your T's: "Time, turn..."

Somewhere else, a pilot on the ILS passes the outer marker. The litany begins: "Time, throttle, turn..."

The T's are as pervasive as GUMPS: everybody has them–at least everybody that flies IFR. Sometimes grouped as six or seven separate items, occasionally five, the T's are a mantra for progress. Do them thoroughly and you can proceed on the approach, ignore them, as tens of thousands of students have discovered, and troubles are likely to crop up.

I use six: Time, Turn, Throttle, Twist, Tune, Talk. I can already imagine the chorus of disagreement: I have the wrong order, I have the wrong items, I left off items, I included unnecessary items...

Take your pick of the following responses: you're all wrong, I'm right; I'm wrong, you're right; you may be right, I'll get back to you; you’re probably wrong, but I'll look into it. The truth is sufficiently flexible to please even a career politician: everybody is sort of right, and everybody can equally be made to appear wrong. It depends largely on personal preference.

For all the variety you will encounter if you ask everybody for their list of T’s, the one consistency you're likely to find is that everyone will agree some sort of mental checklist is necessary to ensure that everything that needs doing at the final approach fix (FAF) or the outer marker (OM) gets done. For that reason, everyone's list will look basically like everyone else's. The order will be slightly different and the items altered a bit, but the similarities will still far outweigh the differences.

WHERE?
Before settling down to the specifics of what might show up on a list of T's, it is essential to determine the general purpose of the checklist and the places at which it should be performed. On approaches, the primary function is to assure that the actions necessary for a safe final descent phase are complete. For that reason, as indicated at the start of this piece, you should plan on a non-precision approach to do the T's at the FAF, be it a navaid, intersection or waypoint.

On precision approaches, the T's change significantly in character–most of the items normally included are superfluous as long as the glide slope (GS) remains operative. The list, then, is not really a primary aid, but rather a way of stockpiling several actions that might become necessary if something goes wrong as the approach continues. Technically, the T's are not even done at the FAF on precision approaches–that fix is defined as the point at which you intercept the GS, while the T's are standardly done a little later on the approach, at the OM.

OTHER USES
Going beyond instrument approaches, the T's can also be used very effectively at the start of holding patterns and procedure turns. In each case, the significance of the individual actions changes somewhat, but the basic structure remains the same.

PREPARATION
In every case, it needs saying that the T's need to be prepared and reviewed before they actually become necessary. This means you should not simply arrive at the fix where you will be doing the checklist and then rattle off six or seven words starting with "t" as fast as you can say them. The checklist works best if the necessary actions are planned in advance. As an obvious example, if there is a turn to be made at the FAF, it is clear you should have familiarized yourself with the new heading long before the checklist triggers the actual control inputs.

With all that out of the way, it is time to start with the actual checklist items. I will use the list and the order I am most comfortable with, but I don't insist you change yours.

TIME
First on virtually everyone's list, "Time" is a signal to start a stopwatch or otherwise note the exact time in order to later determine position. In most circumstances, it is best to have a simple programmable electronic timer–kitchen models work great–that permits advance inputs from which the timer will subsequently count down when started.

There is an obvious argument for placing "time" at the start of the list of T's: how accurate can timing be if you start it only after first doing four or five other things?

Non Precision Approaches: At the FAF, "time" is used to start a countdown (or count up) for identification of the missed approach point (MAP). The exact increment in minutes and seconds for each approach varies with groundspeed and the distance from FAF to MAP. Helpful timing suggestions can be found on approach plates, along with a statement of the actual distance in nautical miles between the two fixes. As an example, if you plan an approach at an airspeed speed of 110 knots and anticipate a 10 knot headwind, it is suggested you use the timing figure given for 100 knots.

The reality is seldom this straightforward–there are several difficulties inherent in using timing to determine the precise location of the MAP, and DME, when available, works much better. The most obvious problem with timing is the improbability of first guessing, then maintaining a constant groundspeed on the entire approach: reported winds at the surface of the airport seldom have much relevance to conditions throughout the final segment. Even without inadvertent changes caused by shifting winds, it is unlikely you will maintain a constant airspeed all the way to the field: slowing on the final third of the approach is usually necessary to effect a successful landing.

Given the variables, and given that you seriously don't want to blindly overfly the MAP while you wait for your stopwatch to start beeping, it is best to use a conservative (short) timing increment when the reported weather threatens you with the possibility of a missed approach. One way to guarantee a safe result is to use timing for a groundspeed 10 knots faster than you really expect. At an approach speed of 120 knots, this will shift the MAP on a six mile final toward you by about a half mile, ensuring that if anything, you will cut the approach short rather than groping ahead beyond the MAP into unsafe airspace.

Since both Jeppeson and the NOS approach charts give timing increments at 20 knot approach speed intervals, not ten, you may need to do a little math to come up with the right timing figure for your approach. The easiest solution is to roughly interpolate between the figures given when you can't find exactly what you are looking for.

Precision Approaches: As stated above, most of the T's are superfluous on precision approaches. "Time" is a good example: as long as the GS remains operative, the MAP is determined by altitude, not distance, and the timing increment given for the localizer (non-precision) approach is largely irrelevant. Nevertheless, most pilots make the effort of timing the final approach segment on an ILS–doing so holds open the possibility of switching to the localizer approach if the GS fails. If you don't note the time as you cross the OM, there may be no other way to identify the MAP on the non-precision procedure, making an immediate missed approach inevitable after GS failure.

It is worth noting that a running stopwatch also helps with overall situational awareness on the ILS: the time since OM passage provides one more piece of data to keep you oriented as you progress toward the runway.

Holding Patterns and Procedure Turns: Every time you use a parallel or teardrop entry to a holding pattern, timing has to start as you proceed outbound. Similarly, because of the distance restriction built into nearly all procedure turns (usually ten miles), it is also necessary to start timing as you cross the procedure turn fix on your way outbound. Failure to note the time in either of these situations makes it close to impossible to know when to turn around–information you definitely need.

TURN
Next on my personal list of T's is "turn." Again, there is strong logic for placing the item early in sequence: if you need to change course after crossing a fix, you do best to start right away. The longer you wait, the greater the correction needed to become established.

Although some approaches have a turn–a "dogleg"–at the FAF, most do not. As a result, "turn" has its greatest application when the T's are used for entering holding patterns. But even without a course change, "turn" can be a useful reminder on all non-precision approaches to check course alignment at the FAF.

Finally, it should be obvious that "turn" plays no role at all on an ILS. If you aren't already established on the localizer by the time you arrive at the OM, you should be thinking missed approach, not turn.

THE REST OF THE LIST
With "Time" and "Turn" out of the way, we are left, again using my personal arrangement, with another four items to go: Throttle, Twist, Tune and Talk.. Expect them next month.

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