4
$\begingroup$

According to AIM 5.4.21(b):

When an early missed approach is executed [...] fly the IAP as specified on the approach plate to the MAP at or above the MDA or DH before executing a turning maneuver.

Hence if a pilot decides on a missed approach, he needs to wait until over the MAP to execute any turns on that procedure. One can only assume that is meant to prevent a climbing turn into a nearby protected airspace.

The following scenario puzzles me.

A pilot executes a LOC approach with a missed approach consisting of "Climb to 1000' then left climbing turn to 5000' direct to..." Sometime after the FAF the cockpit timer breaks. The MAP can no longer be identified by time. The pilot immediately starts climbing to 1000'. But when to start the left climbing turn to 5000'?

  1. The aircraft does not have other equipment that would positively identify the MAP, when is that pilot required to begin that turn?

  2. What if the aircraft has a DME? Is the pilot allowed to identify the MAP by distance rather than by time?

$\endgroup$
0

6 Answers 6

3
$\begingroup$

Well, I’m not an FAA guy so I can’t find the relevant FAR quote, but going more general:

ICAO Doc 8161 Vol 1 - Aircraft Operations I-4-6-1

6.1.4 Note 2

In the case of a missed approach with a turn at an altitude/height, when an operational need exists, an additional protection is provided for the safeguarding of early turns. When it is not possible, a note is published on the profile view of the approach chart to specify that turns must not commence before the MAPt (or before an equivalent point in the case of a precision approach).

There is a nuance difference between AIM’s “you are not supposed to turn” and the ICAO’s “if the turn area is not protected there must be a warning label”. The first is just procedural, the second ensures you will not hit a mountain.

  • If the missed approach only specifies ‘Climb 1000’ then climbing left turn to..’ then the airspace is protected even for early turns (between IAF and MAPt) and you can start turning as soon as reaching 1000’. It might get you in trouble with ATC (ie. they were not expecting you to do it), but it will not get you into a mountain side. If you can call ATC and explain that you are turning early because of a navigation/timing fault, you will be allright.

  • If there is also a ‘do not turn before [...]’ then you shouldn’t turn before, regardless if that fix is the MAPt or not. How to determine that fix or MAPt then becomes a navigation issue:can you use alternative methods? Gps? Dme? Vor radials? are you under radar contact? How about using the VSI climb rate to estimate 1 minute (climbing 700’ at 700 fpm). If neither, then you might be in an emergency situation.

$\endgroup$
3
  • $\begingroup$ Thanks. Ok if it makes my question easier to understand you could interepret the same question with an added missed approach plate instruction that "turns must not commence before the MAP". I'm pretty sure that instruction does not need to be explicitly on the approach plate. You are not supposed to turn until you are over the MAP, AIM 5.4.21 (b). You cannot start turning upon reaching 1000' if you haven't reached the MAP, that is incorrect. Indeed it appears like my question yields => you are in an emergency situation. Several answers suggest so. $\endgroup$
    – mipnw
    Jan 11, 2019 at 10:33
  • $\begingroup$ And just as a side-note, I'm putting this into a comment: I cannot find any equivalent in EASA regulations for this , which means at least in EASA airspace, you are not expected to continue to MAPt $\endgroup$
    – Radu094
    Jan 12, 2019 at 17:25
  • $\begingroup$ In the U.S., FAR 91.175 (a) mandates that when an IAP is necessary it must be completed in accordance with FAR Part 97 (Standard Instrument Procedures - meaning as designed and published). For obstacle clearance protection (or ATC airspace procedural requirements) you must fly the IAP as "published." Turns prior to the MAP are not permitted (or guaranteed safe). If you can't identify the MAP because of equipment failure, you would be in an emergency situation and would have to use your best estimation of the MAP prior to starting the turn...it's all about safety. $\endgroup$
    – user22445
    Sep 17, 2020 at 4:56
1
$\begingroup$

On Question 2: If there is a functioning DME on the airplane, and there was a DME signal that could be used, that is, a DME at the localizer or a DME at a VOR that is aligned with the approach path, yes you could use that, but it almost certainly the approach itself would be a VOR/DME approach and you would be using DME as primary anyway, with timing as a backup if the DME craps out.

If LOC only, your next best option would be to use a crossing radial from a nearby VOR as your primary MAP indication, and if there is one available it's usually depicted on the plate (then there's GPS of course).

You should always have a backup source for the MAP, so if it was LOC only with no nearby VORs and no GPS, so that timing is the only option, I would be using two stopwatches, or a stopwatch and my own watch as a backup.

Which gets us to Question 1: I was (theoretically) foolishly relying on single source timing and that is now gone, with no other source. Well, what else can you do but use common sense to do the best you can? Start counting down verbally from the seconds remaining when the stopwatch failed, and may add a few seconds extra just for kicks.

If you are well above MDA, you have lots of obstacle clearance margin for the missed approach procedure so it's not such a big deal to overshoot the MAP a little bit before you start turning (you could be executing a missed while in the middle of a circling maneuver at MDA on the other side of the airport, so overshooting the MAP a littl bit on final before climbing, even at MDA, is really not a big deal from that standpoint), so I would err on the overshoot side when implementing my best guess countdown. I'd be confident I wasn't going to run into anything.

$\endgroup$
2
  • $\begingroup$ Your comment about the missed during circling is not correct. The clearance slope for the circling missed starts at the MAP and assumes 200ft/nm climb, you need to circle back to the MAP or climb in a circle over the airport within the protected area to a suitable altitude before going missed. Generally about 500 feet above MDA for cat A or B at the far side of the circling area.(one mile runway+1.5mile protected area/ 32:1 climb slope) $\endgroup$
    – Max Power
    Sep 14, 2020 at 22:44
  • $\begingroup$ I should add that I live in mountainous area and the missed obstacle clearance surface often determines the MDA or DA. $\endgroup$
    – Max Power
    Sep 14, 2020 at 22:47
1
$\begingroup$

When there is a turn at the missed approach point, the protected area looks something like this (from the TERPS standards):

enter image description here

There are different diagrams for different situations, but except for missed approaches involving a 180 degree turn or close to it, they all have an unprotected area that you will cross if you turn too early. The diagram for a missed approach with a straight portion followed by a turn (below) is more complicated, but it still has the same feature that no obstacle clearance is guaranteed if you turn too early.

enter image description here

So you need to identify the MAP as best you can, and not turn until you are both past it and above 1000 feet. If you can't identify the MAP then this is an emergency situation, and you should use any and all measures at your disposal to identify it as best you can:

  • If you DME, VOR, RNAV, etc., and you can identify the fix that way, do so
  • If you are in radar contact with ATC, you can declare an emergency and ask them to identify the fix for you
  • If you know about how far you are from the fix, you can try your best to figure the time yourself. You can use the VSI and the altimeter for a fairly good estimate of the time elapsed. You'll need to convert the time you are away from the MAP for your new groundspeed if it changes significantly

Keep in mind that, since you started the climb early, you have a fairly large buffer to turn. If the MDA is 400 feet and it asks you to climb to 1000 feet, then the "Section 1" in the above diagram is about 3 nautical miles long. You can turn anywhere from 1 nautical mile before the MAP (more in some cases) to 3 nautical miles after the MAP and still have guaranteed obstacle clearance.

$\endgroup$
0
$\begingroup$

Generally speaking the 1000feet would be the critical part and assumes no more than 200ft/nm climb unless a specific minimum climb grade is stated on the plate. If the following turn requires some obstacle avoidance they will give a heading to intercept a particular radial. Simply "direct to" implies that there is plenty of lateral clearance once above 1000ft(in this example).

If the approach VOR (or LOC) is on the airport, you can watch for station passage. If you know you are only 2 minutes into a 6 minute approach then count off 4 minutes while also climbing on course. Look at the MSA on the plate, once you get above that you can turn when you want. The approach plate will also give the controlling obstacle elevations.

Don't fly with a single cheap clock as your only source of distance navigation. The odds of this situation are extremely low even with a poor quality watch, but at some point the odds of a situation become so long that you can't justify another contingency plan.

$\endgroup$
0
$\begingroup$

First, we know that the correct time to begin the turn in this case is when both conditions of having reached the MAP and climbed through 1000 have been met. We can climb as soon as we execute the missed. We can turn once we have climbed above the requisite altitude from the missed approach procedure and have laterally reached the MAP. We can reference Instrument Flying Handbook 10-21 under the section that explains how to fly a missed approach procedure, specifically as it relates to beginning the missed approach procedure and its requisite turns.

If the aircraft was equipped such that the timer was the only way to identify the MAP, look for available options outside your aircraft. If ATC has radar coverage, report the failure and ask for assistance identifying the MAP. If there is no radar coverage, notify ATC and do your best to estimate arrival at the MAP. When able, begin configuring the equipment you do have to follow the missed approach procedure which is left out of the hypothetical scenario. There is no official guidance on how to handle this exact equipment failure and situation. Much of it is subjective. The navigation that will be used in the missed would be helpful to the scenario, because as soon as you were able to navigate onto a radial, for example, you would no longer be in the dark about your position from the failed timer.

If the aircraft is equipped with DME, then the failure of the timer is only a loss of redundancy and you can still identify the MAP. DME is more accurate than timing the approach and should be the primary means of identifying the MAP if available.

$\endgroup$
-1
$\begingroup$

No, you can go missed anytime you feel you cannot complete the approach you are currently flying successfully. This includes anytime you are flying the final approach segment before reaching the VDP, if there is one, and all the way to the MAP at MDA.

If, at any time you can no longer identify where you are on an instrument approach because of an equipment malfunction, that’s an emergency situation.

I will also point out that the cockpit timer is not required equipment aboard an airplane for IFR operations. The only thing you’re required to have is a clock with a second hand in order to time the approach (§91.205 (d)(6)).

A failure of a required piece of equipment needed to fly the approach properly would be a mandatory reason to execute a missed approach immediately. If you don’t know where you are, you are swimming in very dangerous waters and your first step is going to be getting away from the ground ASAP. Now if stepdown fixes can be identified by multiple means, then there is some redundancy, unless a piece of equipment eg DME, etc is specifically listed on the plate as required for the approach.

$\endgroup$
5
  • 2
    $\begingroup$ AIM 5.4.21 specifically mentions the requirement not to fully execute a missed approach on a final approach segment until the MAP is reached. Climbs seem permitted, but turns are not. $\endgroup$
    – mipnw
    Jan 10, 2019 at 21:27
  • 1
    $\begingroup$ It would depend on what cause the need initiate the missed approach. In addition, unless comms are lost or some other reason, you usually will not fly the full missed approach procedure but will be handed over to approach controllers who will assign vectors. $\endgroup$ Jan 11, 2019 at 1:30
  • 1
    $\begingroup$ Assuming you have radar service. That's probably worse than being fully dependent on the magenta line. $\endgroup$
    – Max Power
    Sep 14, 2020 at 22:57
  • $\begingroup$ This doesn't answer the question. $\endgroup$
    – ryan1618
    Jun 30, 2023 at 15:44
  • $\begingroup$ Yes it does answer his question. $\endgroup$ Jun 30, 2023 at 19:34

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .