HELP!?! LOZ VOR Approach question!!

[tgrayson]

As another instructor told me this morning, just do whatever ATC says and you're good to go!

No, that is a terrible recommendation, unless ATC is actively vectoring you.

 

[nosehair]

The AIM can't possibly consider every contingency, so a little common sense is in order. The holding pattern is a one minute maneuver, by definition. ATC isn't going to expect you to carry it past that and may be basing traffic separation on that understanding. You need to tell them if you're going to do something unexpected.

OK. I thought that was your logic, which I think is a common mis-conception. I think. Not saying I'm right, but my understanding of the system is that:

A holding pattern is a seperate entity from a procedure turn. When you are holding, you have established holding airspace. When you begin the approach from holding, you have established approach airspace.

I'm not talking about the bold holding shape type PT shown on some charts - that is a PT restricted to holding airspace. I'm talking about a normal PT, which can be flown in the shape of a holding pattern if the pilot desires. If you are holding over a fix with a normal approach PT, when ATC says "cleared for approach" (with no other restrictions) the approach airspace has been opened for you and you can extend your PT which has a holding shape, but it is not holding, so you may make the PT any way you want as long as it is on the PT side and remaining within 10 NM and complying with approach altitudes.

Am I missing something?

I agree that common sense rules, and if you think advising ATC of your intentions to extend, better safe than sorry, but I don't think it is an intended requirement.

I also know from experience that you will get different opinions from ATC people in different locations.

 

[FriendlySkies]

I wouldn't feel comfortable descending at 1700 ft per min. on the inbound leg of a hold to reach my min. alt. of 2300. Especially if flying a multi-engine. This tactic throws out the whole stabalized approach method. Fly the entire approach unless receiving vectors from approach or center.

 

[tgrayson]

If you are holding over a fix with a normal approach PT, when ATC says "cleared for approach" (with no other restrictions) the approach airspace has been opened for you

I think your assumption is invalid that the entire PT airspace has been granted to you. ATC has given you an approach clearance based on what they *think* you are going to do, and your doing something different could result in a loss of separation.

Note the AIM recommendation regarding the timed approach from a holding pattern. Although that isn't the procedure necessarily being implemented when executing an approach from a hold after a missed approach, the situation is fundamentally the same.

(I seem to recall more explicit AIM guidance on this particular issue; either it's no longer there or I misremember it.)

 

[oktex88]

How close to the centerline of the inbound course must you be in order to be considered "established" so you can start your descent? Is there any reason that you must wait until you are wings level on the centerline before starting down? If you decide that you can actually start your descent as you are finishing up your turn onto the final, how much time does this give you to get down to altitude at the VOR? What descent rate would be required? What if you flew the outbound leg for one minute at 120 knots and then slowed to 90 knots when starting to turn inbound - how much time/what descent rate will you need then? What happens if you are still a couple hundred feet high at the VOR? Can you still make a stabilized descent from that point and safely make the runway (assuming you break out by minimums)? If you cross the VOR at 2500, are flying at 90 knots, what descent rate will you need to hit 2.1 DME at 1620? Is this acceptable and safe?

Wanna show us the math on this? lol I hate doing mental math in the cockpit, I should buy a little calculator and put it on my kneeboard.

 

[tgrayson]

What if you had made arrangements with ATC prior to entering a hold for extended leg lengths (longer than your standard 1 minute)? Thinking of holding while waiting for conditions to improve here...

One thing you have to be careful about is getting ATC permission to violate TERPS-mandated limitations. ATC is quite likely to grant you permission to extend the leg lengths of a TERPed holding pattern, but they aren't necessarily guaranteeing you obstacle clearance, because they don't have any knowledge of such. They're saying "no traffic conflict, go for it."

In the present case, it would be safe, but what if the PT were on the other side of the course from the HP? A pilot asking for and receiving permission to extend the leg lengths might be thinking that he received an implicit assurance from ATC that his actions were safe when ATC had no such intention.

 

[tgrayson]

How close to the centerline of the inbound course must you be in order to be considered "established" so you can start your descent?

To be arguably established, you need less than full scale deflection. In some situations, though, even a half-scale deflection can put you outside the protected area for the segment of the approach you're on. Not in this situation, however, since you're so close to the VOR.

Prudent technique is to wait until the needle is pretty much centered. Cutting corners suggests that you're behind the airplane and that increases the likelihood of making mistakes.

 

[SteveC]

How close to the centerline of the inbound course must you be in order to be considered "established" so you can start your descent? Is there any reason that you must wait until you are wings level on the centerline before starting down? If you decide that you can actually start your descent as you are finishing up your turn onto the final, how much time does this give you to get down to altitude at the VOR? What descent rate would be required? What if you flew the outbound leg for one minute at 120 knots and then slowed to 90 knots when starting to turn inbound - how much time/what descent rate will you need then? What happens if you are still a couple hundred feet high at the VOR? Can you still make a stabilized descent from that point and safely make the runway (assuming you break out by minimums)? If you cross the VOR at 2500, are flying at 90 knots, what descent rate will you need to hit 2.1 DME at 1620? Is this acceptable and safe?

Wanna show us the math on this? lol I hate doing mental math in the cockpit, I should buy a little calculator and put it on my kneeboard.

I always round stuff off if I'm going to do math in my head. That's why I used 90 knots and 120 knots in my example. 90 knots = 1.5 miles per minute, 120 knots = 2 miles per minute. Much easier numbers to work with in your head.

Here's a couple of examples:

How fast do you have to descend to make 2300 feet at the VOR? Assuming you're doing one minute legs in the hold, you will roll out on the final approach course with about one minute to the VOR (assuming no wind - real life would probably have a headwind which will give you MORE time, otherwise you'd be using a different runway/approach) you will need to lose 1600 feet (3900-2300) in one minute = 1600 FPM.

What about my example of slowing from 120 knots outbound to 90 knots inbound in the hold? 90 knots is 3/4 of 120 knots, so you are going 3/4 as fast to cover the same distance. If I needed 1600 FPM before, now that I'm going 3/4 as fast I can descend at 3/4 of the rate, so let's call it 1200 FPM.

Let's look at the segment from the VOR to 2.1 DME (good place to be at minimums to allow for a nice stabilized landing, even though the missed is another 1.1 miles away at the threshold). For mental math we'll call it 2 NM. Starting at 2300 feet at the VOR and descending down to 1600 feet at minimums (rounded for mental math purposes) gives 700 feet to lose. If we were doing 120 knots (2 nm per minute) we'd have about 1 minute from the VOR and need 700 FPM; at 60 knots (1 nm per minute) we'd have about 2 minutes and need 350 FPM; so if we're doing 90 knots we'd have about half way between those numbers so we'll call it 1.5 minutes and 500+FPM.

Let's do the numbers again if we cross the VOR at 2600' because we didn't like the higher descent rate (or failed to establish a high enough rate) on our way down to the VOR. Total height to lose = 2600 - 1600 = 1000 feet. At 2 miles per minute we'd need 1000 FPM, at 1 mile per minute we'd need 500 FPM, so at 90 knots (1.5NM per minute) we'd need 750 FPM. Each individual has to decide if they are comfortable with those rates, and understand that the rates will have to be adjusted slightly if continuing to land when the runway comes in sight.

Now we know what kind of descent rates we are talking about in quite a few different possible situations and can make some intelligent decisions about the approach. We can decide if we want to ask for a two minute leg instead of a one minute. If we think that we're going to be tight on making it down to 2300 feet at the VOR we can decide how high we can be and still make a safe descent to the final altitude and even make decisions about what altitude would be too high to continue attempting the approach. We have an idea of the descent rates needed in each segment of the approach to make things work out.

 

[SteveC]

To be arguably established, you need less than full scale deflection. In some situations, though, even a half-scale deflection can put you outside the protected area for the segment of the approach you're on. Not in this situation, however, since you're so close to the VOR.

Prudent technique is to wait until the needle is pretty much centered. Cutting corners suggests that you're behind the airplane and that increases the likelihood of making mistakes.

Agreed!

I'd like to add a note that this is another good example of a time when I fully agree that the general guideline is the best advice to follow for most situations, but that it can be completely safe in certain circumstances to do something differently. As long as the pilot understands what and why he is doing so, it may actually be safer to begin the descent when the needle comes off from full-scale rather than wait for it to be centered. This can be another tool to use in the appropriate situation.

 

[dasleben]

Wait, why is it absolutely incorrect to exit the hold and execute the procedure turn? The hold is part of the missed approach procedure in this case; this isn't a hold in lieu of a procedure turn. I don't necessarily see anything wrong with descending from the hold onto the inbound course as long as you've got positive course guidance and you're stabilized, but you're going to be hard pressed to do the latter if you're in anything faster than a C172. You can certainly ask ATC for longer legs, but if you're going to do that, you might as well simply do the published procedure turn. You can tell ATC if you want, but into an airport such as this (one in, one out), the controller isn't going to simply guess what you're doing; they'll wait for your cancellation of IFR before clearing another aircraft onto the approach. In other words, go nuts.

 

[SteveC]

...but you're going to be hard pressed to do the latter if you're in anything faster than a C172.

Why would aircraft speed make any difference?

 

[dasleben]

Why would aircraft speed make any difference?

If we're holding at 4000' and are trying to make an inbound turn from the hold and be stabilized at 2300' at LOZ (descending once positive course guidance is attained), aircraft speed makes a huge difference. Perhaps we're thinking of two different scenarios here?

 

[SteveC]

It shouldn't make any difference if the hold is based on time. One minute leg will need 1700 FPM regardless of the speed of the aircraft.

It will make a difference if the legs are distance based rather than time.

 

[dasleben]

It shouldn't make any difference if the hold is based on time. One minute leg will need 1700 FPM regardless of the speed of the aircraft.

It will make a difference if the legs are distance based rather than time.

Ah, good point. Still, I'm not a big fan of the 1700fpm. I fly an unpressurized 400-series Cessna with pax so I try to keep the descent rates down to a dull roar. Naturally you have to do what you have to do on an instrument approach, but 1700fpm is a bit much for most of the folks in the back. The procedure turn would be a better bet to keep things smooth and comfortable.

EDIT: Also, rates of descent greater than 1500fpm are prohibited by my company's FOM. Not saying your suggestion is at all wrong, but in my operation I'd need the procedure turn.

 

[SteveC]

Why not just extend the racetrack pattern and use it as the procedure turn? You're allowed to do a procedure turn in a number of different ways, including the depicted 45/180/45, an 80/260, a teardrop, or even a racetrack. That's what I'm advocating. It makes a lot more sense to me to just continue the racetrack pattern that you're already in, rather than do this:

1. Cross the VOR inbound at 4000' and turn right 225 degrees.
2. Intercept the final approach course outbound, turning left 45 degrees.
3. Time for two minutes? (Two minutes from the VOR or from when we intercepted outbound???)
4. Turn left 45 degrees.
5. Time for one minute.
5. Turn right 180 degrees.
6. Time for 45 seconds.
7. Turn right 45 degrees, adjusting to intercept the final approach course.
8. Descend to 2300 feet (guessing at the required descent rate because we aren't sure how far we are from the VOR in minutes).

Wouldn't it be better to:

1. Cross the VOR inbound at 4000' and turn right 180 degrees (adjust for wind as needed, which hopefully we've already figured out from the previous turns).
2. Travel outbound for 2 minutes.
3. Turn right 180 degrees (or as previously figured to intercept the final course).
4. Descend at 850 FPM to reach the VOR at 2300 feet.

Maybe we're missing each other on the terminology. Maybe it would be better if I called my techique a "racetrack pattern procedure turn" rather than a "holding pattern"? Maybe I'm wrong in assuming that what you're talking about when you say "procedure turn" is the eight item procedure I listed above?

Anyway, I understand what you're talking about with needing more time for the descent, since I've got around 1000 hours in C401s and C310s myself. I'm still thinking it's simpler, especially for single pilot ops, to just do a longer leg racetrack pattern to get the time you want for the descent.

Good discussion.

 

[fish314]

To be arguably established, you need less than full scale deflection. In some situations, though, even a half-scale deflection can put you outside the protected area for the segment of the approach you're on. Not in this situation, however, since you're so close to the VOR.

Prudent technique is to wait until the needle is pretty much centered. Cutting corners suggests that you're behind the airplane and that increases the likelihood of making mistakes.

As I recall, the FAA doesn't define "established" for a VOR, but I'm pretty sure the ICAO does. So overseas, "established" is +/- 5 degrees. About 3-4 years ago, the AF adopted this definition also. I assume the thinking was something along the lines of "teach 5 degrees, and the guys will be legal no matter where they fly".

 

[tgrayson]

As I recall, the FAA doesn't define "established" for a VOR, but I'm pretty sure the ICAO does.

All true, which is why I said "arguably". But even the ICAO definition is made without regard to the capabilities of the navigation system in use, particuarly when you throw in the ±6 degrees of allowable error in our VOR receivers. Operationally, I would argue for less than 1/4 scale deflection.

 

[fish314]

All true, which is why I said "arguably". But even the ICAO definition is made without regard to the capabilities of the navigation system in use, particuarly when you throw in the ±6 degrees of allowable error in our VOR receivers. Operationally, I would argue for less than 1/4 scale deflection.

Ahah. Is your line of thinking that "established" should keep me within terps'ed airspace at the maximum allowable error? In other words, if I'm established, then my system could be off by the +/- 6 degrees, plus whatever the VOR transmitter itself is allowed to be off, and I'm still within protected area.

Because that's just about crazy enough to make sense!

 

[tgrayson]

Ahah. Is your line of thinking that "established" should keep me within terps'ed airspace at the maximum allowable error?

Assuming your goal is not to hit anything, rather than just being legal.

Even ignoring your VOR receiver errors, 1/2 scale deflection becomes pretty marginal on some approach types. The Instrument Procedures Handbook has a table at the back with what they view the tolerances ought to be, based on approach type. They suggest a higher standard than the Instrument PTS, which is 3/4 scale deflection on final approach, and just less than full scale prior to that.

 

[TFaudree_ERAU]

Let me preface this comment by saying that I am not as well versed in the TERPS as some others in this thread. However:

I'm the kind of pilot that likes to stay on the thick black lines of an approach. Also, if I'm not mistaken, the dashed lines that depict the holding pattern are part of the missed approach procedure; same as the climbing left turn back toward the VOR. To me, that means that you can't just improvise by extending the outbound leg of the holding pattern and call it an outbound leg to the procedure turn. The holding pattern is there so that you can have a safe place to hang out until ATC can sequence you back on to a segment of the approach. By extending the outbound leg of the holding pattern, you'd be combining two different components of the approach, and I'd say wrongfully so.

My answer is that I'd cross the VOR on the inbound leg of the hold, make a right 225* turn to join the R-205 outbound. Start the time abeam the VOR. If the sharp turn makes you uncomfortable, I'd make a request to fly the outbound radial to either ESONE or JARAM and join the arc.