Missed approach procedure is baesd on what performance?

[BlackandWhite2000]

Hi guys, just a simple question but maybe difficult to answer.

Let's say we are flying an instrument approach, VOR or ILS....doesnt matter.
So, is the missed approach procedure based on "one engine inop" performance?
I try to look it up in ICAO DOC-8168:Part 1-Section 4-Ch 6, but I can not find anything there.

Can anyone help me to clear this out? And please, if you can, show me where it is written in the ICAO document.

Thank you so much.

[nick14]

It is based on a climb gradient standard of 2.5%. Anything other than the standard is printed on the chart with a lower minima usually or just a blanket requirement of the higher gradient (Granada that I can think of off the top of my head). Most aircraft performance charts show missed approach climb gradient charts with one engine inop. Not sure where the rules would be written.

[Microburst2002]

They are based on a specific gradient. If you can't make it, then you need to devise an alternative procedure where you clear obstacles, or else you need to reduce weight.

EOMAPs are an operator responsibility.

[vilas]

　EU-OPS 1.510 Landing – Destination and Alternate Aerodromes(b) For instrument approach with a missed approach greater than 2.5%, an operator shall verify that the expected landing mass (…) missed approach equal or greated than the applicable missed approach gradient (…) in the one-engine inoperative missed approach configuration and speed (…)


(c) For instrument approaches with decision heights below 200 ft, an operator must verify that the expected landing mass allows a missed approach gradient of climb, with the critical engine failed and with the speed and configuration used for go-around of at least 2.5%, or the published gradient (…)

[Speedwinner]

Its curios : the certification single engine is 2,1% right? So actually the missed approach is calculated with 2.5. Doesn't make any sense for me. Any thoughts on that?

[Skyjob]

Both scenarios need be considered:
engine failure and approach climb
each has different limitations and configurations for calculations
most limiting case is usually engine failure on approach (e.g. 1' prior minimums)

2.5% is standard procedure design, unless a higher gradient is published.
operator is responsible to verify missed approach gradient can be flown prior to commencement of approach, or alternatively higher minimums can sometimes be used to offset this capability

[cosmo kramer]

Doc 8168 Vol 1:

http://s3.postimg.org/pjj8upkxv/image.jpg

In other words, everything posted above is not correct.

[Skyjob]

Cosmo, before dismissing other people's knowledge, maybe a further read of manuals may be prudent.
CS-25.119 and CS-25.121 refer:

CS 25.119 Landing climb: all-engines- operating
In the landing configuration, the steady gradient of climb may not be less than 3·2%, with –
(a) The engines at the power or thrust that is available 8 seconds after initiation of movement of the power or thrust controls from the minimum flight idle to the go-around power or thrust setting (see AMC 25.119(a)); and
(b) A climb speed which is – (1) Not less than –
(i) 1·08 VSR for aeroplanes with four engines on which the application of power results in a significant reduction in stall speed; or
(ii) 1·13 VSR for all other aeroplanes;
(2) Not less than VMCL; and
(3) Not greater than VREF.

CS 25.121 Climb: one-engine- inoperative
(See AMC 25.121)
(a) Take-off; landing gear extended. (See AMC 25.121(a).) In the critical take-off configuration existing along the flight path (between the points at which the aeroplane reaches VLOF and at which the landing gear is fully retracted) and in the configuration used in CS 25.111 but without ground effect, the steady gradient of climb must be positive for two-engined aeroplanes, and not less than 0·3% for three-engined aeroplanes or 0·5% for four- engined aeroplanes, at VLOF and with –
(1) The critical engine inoperative and the remaining engines at the power or thrust available when retraction of the landing gear is begun in accordance with CS 25.111 unless there is a more critical power operating condition existing later along the flight path but before the point at which the landing gear is fully retracted (see AMC 25.121(a)(1)); and
(2) The weight equal to the weight existing when retraction of the landing gear is begun determined under CS 25.111.
(b) Take-off; landing gear retracted. In the take-off configuration existing at the point of the flight path at which the landing gear is fully retracted, and in the configuration used in CS25.111 but without ground effect, the steady gradient of climb may not be less than 2·4% for two-engined aeroplanes, 2·7% for three-engined aeroplanes and 3·0% for four-engined aeroplanes, at V2 and with –
(1) The critical engine inoperative, the remaining engines at the take-off power or thrust available at the time the landing gear is fully retracted, determined under CS 25.111, unless there is a more critical power operating condition existing later along the flight path but before the point where the aeroplane reaches a height of 122 m (400 ft) above the take-off surface (see AMC 25.121(b)(1)) ; and
(2) The weight equal to the weight existing when the aeroplane’s landing gear is fully retracted, determined under CS 25.111.
(c) Final take-off. In the en-route configuration at the end of the take-off path determined in accordance with CS 25.111, the steady gradient of climb may not be less than 1·2% for two-engined aeroplanes, 1·5% for three-engined aeroplanes, and 1·7% for four-engined aeroplanes, at VFTO and with –
(1) The critical engine inoperative and the remaining engines at the available maximum continuous power or thrust; and
(2) The weight equal to the weight existing at the end of the take-off path, determined under CS 25.111.
(d) Approach. In a configuration corresponding to the normal all-engines-operating procedure in which VSR for this configuration does not exceed 110% of the VSR for the related all-engines-operating landing configuration, the steady gradient of climb may not be less than 2·1% for two-engined aeroplanes, 2·4% for three-engined aeroplanes and 2·7% for four-engined aeroplanes, with –
(1) The critical engine inoperative, the remaining engines at the go-around power or thrust setting;
(2) The maximum landing weight;
(3) A climb speed established in connection with normal landing procedures, but not more than 1·4 VSR; and
(4) Landing gear retracted.


Chapter 6 in 8168 Vol. II for instance refers:

6.1.1 Requirements
6.1.1.1 A missed approach procedure shall be established for each instrument approach and shall specify a point where the procedure begins and a point where it ends. The missed approach procedure is initiated:
a) at the decision altitude height (DA/H) in precision approach procedures or approach with vertical guidance (APV); or
b) at the missed approach point (MAPt) in non-precision approach procedures.
6.1.1.2 The missed approach procedure shall terminate at an altitude/height sufficient to permit:
a) initiation of another approach; or
b) return to a designated holding pattern; or
c) resumption of en-route flight.
Only one missed approach procedure shall be established for each approach procedure.
Note.— This chapter contains general criteria which apply to all types of instrument landing procedures, as well as criteria specific to non-precision procedures. For the details regarding precision approaches and approaches with vertical guidance, see the applicable chapters.
6.1.2 Phases of missed approach segment
In principle the missed approach segment starts at the MAPt and includes the following three phases (see Figure I-4-6-4):
a) initial phase — begins at the earliest MAPt, and extends until the Start of Climb (SOC);
b) intermediate phase — extends from the SOC to the point where 50 m (164 ft) (Cat H, 40 m (132 ft)) obstacle clearance is first obtained and can be maintained; and
c) final phase — extends to the point at which a new approach, holding or return to en-route flight is initiated. Turns may be carried out during this phase.
6.1.3 Types of missed approach
There are two types of missed approach:
a) straight missed approach (includes turns less than or equal to 15 degrees); and
b) turning missed approach.
6.1.4 Missed approach area
The area considered for the missed approach shall start at the earliest MAPt tolerance, with a width equal to that of the final approach segment at that point. The subsequent size and shape of the area depends on the missed approach procedure, including the point at which a turn is initiated, if applicable, and the extent of the turn.
6.2 CLIMB GRADIENT AND MOC
6.2.1 Initial phase
6.2.1.1 The initial phase begins at the earliest missed approach point (MAPt) and ends at the start of climb point (SOC). The manoeuvre during this phase requires the concentrated attention of the pilot, especially when establishing the climb and the changes in configuration, and it is assumed that guidance equipment is not utilized during these manoeuvres. No turns may be specified during this phase.
6.2.1.2 Climb gradient in the initial phase. In the initial phase the flight track is horizontal.
6.2.1.3 Obstacle clearance in the initial phase. In the initial missed approach area, the minimum obstacle clearance shall be the same as for the last part of the final approach area except where the extension of the intermediate missed approach surface backwards towards the missed approach point requires less clearance. (See Figures I-4-6-4 and I-4-6-5.)
6.2.2 Intermediate phase
6.2.2.1 The intermediate phase begins at the SOC. The climb is continued at stabilized speeds up to the first point where 50 m (164 ft) (Cat H, 40 m (132 ft)) obstacle clearance is obtained and can be maintained. In the construction of this phase it is assumed that advantage may be taken of available navigation guidance. During the intermediate phase, the missed approach track may be changed from that of the initial phase by a maximum of 15°.
6.2.2.2 Climb gradient in the intermediate phase. The nominal climb gradient (tan Z) of the missed approach surface is 2.5 per cent. A gradient of 2 per cent may be used if the necessary survey and safeguarding can be provided. Additional climb gradients of 3, 4 or 5 per cent may also be specified. These may be used by aircraft whose climb performance permits the operational advantage of the lower OCA/H associated with these gradients, with the approval of the competent authority.
Note.— In case of non-precision approach, any intermediate values (e.g. 3.4 per cent) between 2 and 5 per cent may be considered.
6.2.2.3 Obstacle clearance in the intermediate phase
6.2.2.3.1 In the intermediate missed approach phase, the minimum obstacle clearance shall be 30 m (98 ft) in the primary area, and in the secondary area the minimum obstacle clearance shall be 30 m (98 ft) at the inner edge, reducing linearly to zero at the outer edge. See Section 2, Chapter 1, 1.3, “Obstacle clearance”.
6.2.2.3.2 The OCA/H for the nominal 2.5 per cent must always be published on the instrument approach chart. If additional gradients are specified in the construction of the missed approach procedure, they and their associated OCA/H values must be published as alternative options.
Note.— MOC may be obtained by increasing the OCA/H or by a longitudinal adjustment of the MAPt or both.
6.2.3 Final phase
The final phase begins at the point where 50 m (164 ft) (Cat H, 40 m (132 ft)) obstacle clearance is first obtained and can be maintained. It ends at the point at which a new approach, holding or return to en-route flight is initiated. Turns may be carried out during this phase.
6.2.3.1 Climb gradient in the final phase. The criteria of the intermediate phase apply. 6.2.3.2 Obstacle clearance in the final phase
6.2.3.2.1 In the final missed approach phase of a straight missed approach the minimum obstacle clearance shall be 50 m (164 ft) (Cat H, 40 m (132 ft)) in the primary area, reducing linearly to zero at the outer edge of the secondary area. See Figure I-4-6-4.
6.2.3.2.2 Turning missed approaches have specific criteria for MOC and for the arrangement and extent of secondary areas (see 6.4, “Turning missed approach”).
Note.— MOC may be obtained by increasing the OCA/H or by a longitudinal adjustment of the MAPt or both. In addition, obstacles may be excluded from consideration by defining a turn.

In ALL cases the performance criteria must be achieved.


Approach Segment is one engine out and take-off thrust. Gear is up. Flaps are retracted a bit to increase stall speed by 10% above the stall speed with landing flap deflection. With this flap setting the airplane is flown at V = 1.5 Vs at the landing weight.

Landing Segment is the only case with all engines operating. Gear is extended, flaps in landing position, V = 1.3 Vs and thrust that is available 8 secs. after the throttle is moved from idle to take-off thrust position.


EASA CAT.POL.A.225 refers

AMC2 CAT.POL.A.225 Landing – destination and alternate aerodromes
MISSED APPROACH
(a) For instrument approaches with a missed approach climb gradient greater than 2.5 %, the operator should verify that the expected landing mass of the aeroplane allows for a missed approach with a climb gradient equal to or greater than the applicable missed approach gradient in the OEI missed approach configuration and at the associated speed.
(b) For instrument approaches with DH below 200 ft, the operator should verify that the expected landing mass of the aeroplane allows a missed approach gradient of climb, with the critical engine failed and with the speed and configuration used for a missed approach of at least 2.5 %, or the published gradient, whichever is greater.
MISSED APPROACH GRADIENT
(a) Where an aeroplane cannot achieve the missed approach gradient specified in AMC2 CAT.POL.A.225, when operating at or near maximum certificated landing mass and in engine-out conditions, the operator has the opportunity to propose an alternative means of compliance to the competent authority demonstrating that a missed approach can be executed safely taking into account appropriate mitigating measures.

[Lantirn]

Missed app gradient is 2.5 and is all engines as many said above.

However for single engine ops you can always fly the EO procedure but advise ATC.

[BlackandWhite2000]

Thanks guys.

I know that the standard missed approach gradient is 2.5%.
So, does it means:
1.In case of one engine inop, as long as I can still have a climb gradient > 2.5% during missed approach, I can just follow the published missed approach procedure?
2.In case of one engine inop, and I can not have a climb gradient > 2.5% during missed approach, I need to follow the special engine out procedure instead of the missed approach procedure?
3.In case of one engine inop, and I can not have a climb gradient > 2.5% during missed approach, and there is no special engine out procedure, then I either maintain runway heading and climb to MSA and request radar vector, or I follow a SID which is appropriate?

[Microburst2002]

We must not confuse approach climb gradient requirements with obstacle clearance for the missed approach procedure!

Approach climb gradient is based on one engine failed, it is similar to the climb requirement at take-off, only with approach configuration.

this requirement is, i believe, independent of what kind of approach you make. Even in a visual you have to meet this requirement. It is not an IFR thing, to my knowledge.

The missed approaches designed as per PANS OPS have a gradient for obstacle clearance (with a minimum gradient even if there is no obstacles). If you can make it with one engine out, you can fly it one engine out. If you cannot fly it with one engine out, then don't fly the approach or reduce weight, or design your own EOMAP.

[Speedwinner]

As I said I don't get it. Why didn't they design the map gradient with 2.1 % ? So everybody would be sure that the approach climb gradient would fit the missed approach if there was no other required gradient by the procedure. I mean what is the advantage of the difference between climb gradient in approach and the single engine climb gradient or am I mixing stuff ?

[despegue]

A very serious word of caution here, and one I do hope we all are aware of:

NEVER EVER just assume your EO escape menoeuvre is also valid when going around.
An EO escape manoeuvre for departures are calculated for an engine failure at V1, and based on performance from that point onwards and on the ground.

If you go-around from an approach, your initial point of N-1 is located in a very different location, rendering the procedure completely incorrect.

An example.

EO escape route says: " climb to 1800 ft. agl. Then, turn right inbound ROS VOR"

if following this procedure from the approach phase, and from already an airborne altitude, your turn will obviously MUCH earlier, taking you potentially into terrain or other conflict zones that the procedure is specifially avoiding.

[zlin77]

In the olden days, missed approach climb gradient of 2.5% assumed, one engine inoperative, landing gear retracted and an intermediate flap setting, speed not above 1.5 Vs.......I believe a certification requirement that manufacturers would meet to ensure compliance, Landing Climb was all engines operating, gear down, landing flap and speed not below 1.3 Vs....I will standby to be corrected..:uhoh:

[Anvaldra]

The following concerns to Airbus




3.3. Go-Around Performance Requirements
A minimum climb gradient must be observed, in case of a go-around. The
minimum air climb gradients depend on the aircraft type.

3.3.1. Approach Climb
JAR 25.121 Subpart B
FAR 25.121 Subpart B
This corresponds to an aircraft’s climb capability, assuming that one engine is
inoperative. The “approach climb” wording comes from the fact that go-around
performance is based on approach configuration, rather than landing configuration.
For Airbus fly-by-wire aircraft, the available approach configurations are CONF 2 and
3.
3.3.1.1. Aircraft Configuration
•
One engine inoperative
•
TOGA thrust
•
Gear retracted
•
Slats and flaps in approach configuration (CONF 2 or 3 in most cases)
•
1.23 VS1g ≤V ≤1.41 VS1g and check that V ≥ VMCL
3.3.1.2. Requirements
The minimum gradients to be demonstrated:
Approach Climb
Minimum
climb gradient
one engine out
Twin 2.1%
Quad 2.7%

An approach configuration can be selected, as long as the stall speed VS1g of this configuration does not exceed 110% of VS1g of the related “all-engines-operating“ landing configuration.


3.3.2. Landing Climb
JAR 25.119 Subpart B
FAR 25.119 Subpart B
The objective of this constraint is to ensure aircraft climb capability in case of a
missed approach with all engines operating. The “Landing climb” wording comes from
the fact that go-around performance is based on landing configuration. For Airbus
FBW, the available landing configurations are CONF 3 and FULL.

3.3.2.1. Configuration
•
N engines
•
Thrust available 8 seconds after initiation of thrust control movement from
minimum flight idle to TOGA thrust
•
Gear extended
•
Slats and flaps in landing configuration (CONF 3 or FULL)
•
1.13 VS1g ≤ V ≤ 1.23 VS1g and check that V ≥ VMCL
.
3.3.2.2. Requirements
The minimum gradient to be demonstrated is 3.2% for all aircraft types.
N engines
TOGA thrust
gear extended
landing configuration
minimum
gradient: 3.2%


For all Airbus aircraft, this constraint is covered by the approach climb
requirement. In its operational documentation (FCOM), Airbus publishes the
maximum weight limited by the approach climb gradient only. Landing climb
performance is found in the AFM

[Speedwinner]

Thanks alvandra perfect answer

[Lantirn]

We must not confuse approach climb gradient requirements with obstacle clearance for the missed approach procedure!

Spot on!

If you go-around from an approach, your initial point of N-1 is located in a very different location, rendering the procedure completely incorrect.

An example.

EO escape route says: " climb to 1800 ft. agl. Then, turn right inbound ROS VOR"

if following this procedure from the approach phase, and from already an airborne altitude, your turn will obviously MUCH earlier, taking you potentially into terrain or other conflict zones that the procedure is specifially avoiding.

That's why EO procedures should be geometric in terms of distance. At least in my company they are indeed like this

[arxipov]

One more question on A320, if you don't mind.

At one of airfields our company flies to, published minimum MACG is 5%. No mountains there, I don't know why exactly is it so high.
Let's assume that approach climb gradient, calculated by performance app in the EFB, or extracted from AFM tables is exactly 5%.

Now in case we go around one day and one engine fails, at what altitude should we accelerate and retract flaps?

Missed approach procedure tells us to climb to 3000 ft AAL, MSA is 2000 ft AAL there. But everyone leaves ENG OUT ACC height at 1500 ft. Doesn't seem right to me.

[Lantirn]

Arxipov,

You are right. No level off segment is allowed in the missed app procedure except when in the missed approach altitude.

2 options. Fly the missap if the single engine performance is satisfactory of fly the company EO procedure if obst clearance is not guaranteed otherwise

For the Airbus, you could readjust accordingly the EO acc alt to the missed app procedure altitude but, have in mind that this function is only a reminder, and nothing will change systemswise.

[Speedwinner]

Ok to make it simple:

When you fly to an area with a lot of critical terrain you have to check that you will fulfill the approach climb gradient with your landing weight at destination. In a cat 1 scenario it would be 2.1%. If you can't you have to do something to get the bird legal to destination. If the go around climb gradient is higher than what you can fly you have to fly you can fly the eosid.

Stop I don't get it. So in Zurich you need about 5%. You have to check the se ga climb gradient before you fly there? Is the approach climb gradient just a certification thing? Confusing guys

[wondering]

At one of airfields our company flies to, published minimum MACG is 5%. No mountains there, I don't know why exactly is it so high.
Let's assume that approach climb gradient, calculated by performance app in the EFB, or extracted from AFM tables is exactly 5%.

ATC or airspace requirements? Some SID charts which have higher than standard climb requirements often have a statement to that effect e.g. Nice. I reckon the same is true for some approaches.

[cosmo kramer]

@Skyjob, nice quotes. But CS-25 deal with certification specifications for lange airplanes. :ugh:

If your aircraft doesn't meet the requirements in CS-25, it wouldn't fly at all, as it would not have been certified.

Try again....

[cosmo kramer]

Thanks guys.

I know that the standard missed approach gradient is 2.5%.
So, does it means:
1.In case of one engine inop, as long as I can still have a climb gradient > 2.5% during missed approach, I can just follow the published missed approach procedure?
2.In case of one engine inop, and I can not have a climb gradient > 2.5% during missed approach, I need to follow the special engine out procedure instead of the missed approach procedure?
3.In case of one engine inop, and I can not have a climb gradient > 2.5% during missed approach, and there is no special engine out procedure, then I either maintain runway heading and climb to MSA and request radar vector, or I follow a SID which is appropriate?

BlackandWhite2000, in principle, you only ever fly the standard missed approach with all engines operating. Because this is what the procedures are designed for. First freaking paragraph in ICAO Doc 8168!!!

I don't know why people have so much trouble getting their heads around this. It is generally accepted not to fly a SID with an engine out. But most people seem to believe you have to be able to fly a G/A single engine. Some even believe you have to leave passengers or luggage behind, if not able.

Fact is, that you only have to meet the gradient with all engines operating.

So what do you do if an engine fails:
You ask your operator! Just like ICAO wrote:

Note.- Development of contingency procedures is the responsibility of the operator.
If your operator doesn't have an answer for you, the you report them to the authorities, refuse to fly and start looking for work at a serious company.

My operator specified engine out G/A procedures for every runway we fly to. Mostly they are identical to the takeoff engine out contingency procedure. Or they may be identical with the published G/A. In both cases the company from where we get our performance data, has calculated that it is possible to fly the procedure with one engine out.

In no case do you start to make calculations yourself (unless you want to make yourself a criminal). 2.5% may be a no-brainer. But what if the published missed approach has a gradient of e.g. 6% to 7000 feet, and the procedure contains several turns?
You have no chance of make a reasonable calculation yourself. Even from charts in the performance manual. Remember you gradient diminishes in a banked turn. So even if you are able to calculate an average, you still don't know if the mountain peek is just at the place, where your gradient is lower than the required average, because you are in a bank.

[cosmo kramer]

Microburst2002
We must not confuse approach climb gradient requirements with obstacle clearance for the missed approach procedure!
:D
Exactly.

Allow me to elaborate:

Regarding approach and landing climb for certification, these are just ways for the authorities to ensure, that the aircraft being certified, is able to climb somewhat at all. They (FAA originally) deviced these manoeuvres and set the requirements, that needs to be demonstrated, to a level that they decided was to be considered safe.

It has nothing to do with obstacle clearance. They demonstrate that the aircraft has a certain climb performance, nothing more, nothing less!


A complete different authority (ICAO), set a limit for minimum obstacle clearance during (all engines operating/normal/standard/day-to-day) go arounds. Their assessment of what is safe resulted in a minimum required gradient of 2.5%. For our modern high-performance aircrafts with gradients in the 15%+ range, this is not a problem (remember these requirements were set in the 60'ies and applies to propeller/general aviation aircrafts as well).

[arxipov]

Thanks, cosmo kramer. Makes sense now)

[john_tullamarine]

Folks,

The confusion is common and has been so for aeons. If I may be permitted to add to cosmo kramer's observations, above ..

The Certification Standards (eg FAR25) are concerned with providing a vehicle which is reasonable to fly and repeatably so. Indeed, one could say that one FAR25 Type is much the same as another for aircraft in recent decades and that is the intent of the Standards and certification processes.

This is addressed without any particular concern about runways and rocky bits.

What you do with the vehicle once you get your hands on it is a whole different ball game.

Then, for obstacle considerations, it becomes an ops engineering concern.

At the end of the day the Certification Standards (eg approach and landing climb WAT limits) conspire to constrain the MTOW and MLW without any consideration being given to the runway and airport environs.

If the runway or obstacle situation dictates, then the AFM limiting weight must be reduced further to accommodate whatever ends up being the critical case for the particular operation.

[Microburst2002]

Regarding the issue of when to accelerate after an actual engine failure in a go around, the notion that I have is that if your company does not have a special EOMAP designed for that runway (because it never does such thing for any runway) then you should fly the published missed approach procedure and accelerate at the missed approach altitude, and not earlier (because the procedure is not designed for level segments, and even if the overall average gradient is better than the gradient required, it might not cover a level off part of it)

In companies which do provide EOMAPs, but in a runway that does not require one, it is supposed that you can accelerate like in the failure case after take-off, with an intermediate level off acceleration segment. The EOMAP is only required if you cannot make it like that. Or maybe it depends on the provider and in other cases, in those runways that don't require an EOMAP you have to accelerate only at MAP altitude, just in case.

[7478ti]

The above thread is why both FAA's AC120-29A issued on Aug 12, 2002, as well as ALL [real] RNP based procedures, ...now specify providing protection for air carriers for safe obstacle clearance for the balked landing from the TDZ, while still accommodating the first engine failure, as well as the first NAV failure. That way, loss of visual reference is protected all the way to the runway, as well as for any go-around, irrespective of above or below DA(H), whether initiated OEI, or having an engine subsequently fail at any time after a balked landing (even near the TDZ) has been initiated. Both TERPS and PANS-Ops, as well as other some other states' operations and SIAPS used by air carriers do not necessarily address this issue, ....for assuring a safe go-around missed approach path, for any G/A initiated either before or after descending below DA(H), ... such as in the event of an unsafe (blocked) runway, low mu report or observation, excessive wind component, windshear, or loss of visual reference. This safe go-around protection has always been intended for US air carriers since the jet age, but was only explicit for Cat II and Cat III ops, until it was formalized on July 13, 1999 in AC120-28D, and in 2002 with the publication of AC120-29A (para 4.3.1.8).