CS AWO.B.CATIII.115 Performance demonstration

ED Decision 2022/007/R

(See AMC AWO.B.CATIII.115)

(a) Flight path and speed control shall comply with CS AWO.B.CATII.113 and CS AWO.B.CATII.116. (See AMC AWO.B.CATII.113)

(b) Touchdown performance of landing systems shall comply with CS AWO.A.ALS.106, CS AWO.A.ALS.107, and CS AWO.A.ALS.109. For operation with no DH, compliance with the lateral touchdown performance criteria shall be demonstrated at main-wheel and nose-wheel touchdown.

(c) The automatic throttle/thrust system shall comply with CS AWO.A.ALS.105.

(d) Compliance with CS AWO.B.CATIII.116 and CS AWO.B.CATIII.117(a) shall be demonstrated primarily by flight test. Compliance with paragraphs (a) and (b) of this paragraph and with CS AWO.B.CATIII.117(b) shall be demonstrated by analysis and simulator tests supported by flight tests. Flight testing and any associated analysis shall include a sufficient number of approaches and landings conducted in conditions which are reasonably representative of actual operating conditions and shall cover the range of parameters affecting the behaviour of the aeroplane.

(e) In showing compliance with paragraphs (a) and (b), when a HUDLS is used for primary guidance (HUD manual landing), the following additional variables shall be included in the performance demonstration (see AMC AWO.A.HUD.107):

(1) ambient lighting conditions, and approach and runway lighting;

(2) variations of the reported RVR; and

(3) individual flight crew performance.

[Issue: CS-AWO/2]

AMC AWO.B.CATIII.115 Performance demonstrations

ED Decision 2022/007/R

1 Approach

The supporting flight tests to show compliance with CS AWO.B.CATIII.115(a) in respect of approach performance may be a programme of flight demonstrations carried out in accordance with AMC AWO.B.CATII.113.

2 Touchdown

For compliance with CS AWO.B.CATIII.115(b) in respect of touchdown performance, a programme of flight demonstrations will be required to support the simulation and analysis. (See AMC AWO.A.ALS.106)

3 Ground roll

3.1 A programme of landings should be carried out to ensure that there is a confidence level of 90 % that the criterion of CS AWO.B.CATIII.117(a) is complied with. This programme and the analysis of the results should be in accordance with the procedures established for approach performance. (See AMC AWO.B.CATII.113 paragraph 2)

3.2 When operation is based on fail-operational ground roll, a programme of flight demonstration landings is necessary to support the simulation and the analysis programme which are required to demonstrate compliance with CS AWO.B.CATIII.117(b). (See AMC AWO.A.ALS.106)

4 Considerations for GLS

4.1 Compatibility with rare undetected non-aircraft system error conditions
(See Appendix 1 to AMC to Subpart A)

The criteria below establish the compatibility of the ICAO standardised ground monitoring performance for satellite faults and single ground-reference receiver faults with the aircraft performance including satellite geometry screening. The criteria ensure that undetected faults or rare normal errors in non-aircraft GBASs, when combined with all other nominal factors that affect landing performance, do not result in an unacceptably high probability of landing outside the limits that define a safe landing.

Note: Appendix 1 to AMC AWO.B.CATIII.115 GBAS performance model for approach and landing simulation contains a list of references that have been used to derive the signal model. These references describe undetected non-aircraft system error conditions, rare normal performance and faults as well as the ICAO standardised ground system monitoring requirements. The aircraft requirements in this Section are intended to address non-aircraft system errors that are below the ground monitoring thresholds. The existence of such errors is not considered a malfunction of the non-aircraft system.

For any value of GLS NSE, including the effects of undetected satellite faults and undetected faulted conditions at a single ground-reference receiver, it must be shown that the touchdown performance will be such that the exceedance of any of the limits prescribed in CS AWO.A.ALS.106(c) will be less than those prescribed in AMC AWO.A.ALS.106 paragraph 1.4 for the limit condition.

Other non-GLS variables that effect performance shall vary according to their expected distributions when assessing this compatibility. Credit for the prior probability of the fault cannot be taken when evaluating the required landing probabilities; however, credit may be taken for the ground subsystem’s probability of detection for satellite faults and the aircraft’s probability of detection for single-reference receiver faults.

Note: It is assumed that operations will be approved with knowledge of the runwayspecific glide path and threshold crossing height values and the aircraft’s capability. Therefore, it is not necessary to determine compliance with this Section using the glide path and threshold crossing height values set to the limit allowed for the aircraft.

4.2 Compatibility with worst-case undetected guidance errors

Rare ionosphere events and undetected satellite or ground station failures could result in significant vertical (and lateral) position errors. Under certain conditions, such errors may go undetected by the system and could result in erroneous guidance if not mitigated. The effect of such errors may not be observable by the flight crew.

All undetected errors that are not extremely improbable shall not prevent a safe landing and/or go-around when all other variables that effect the performance are at their nominal values. The effect of worst-case undetected errors on landing system performance shall be assessed via simulation using the GLS noise model provided in Appendix 1 to AMC to Subpart A. The worst-case undetected errors shall be simulated by using the maximum range domain error given in Table 5 of Appendix 1 to AMC to Subpart A in conjunction with the appropriate geometry screening factors used by the aircraft. The certification plan must specify how the demonstration will be conducted, including the number of cases and variables with pass–fail criteria. The aeroplane performance shall be assessed in the presence of the full range of bias and ramp type failures produced by the fault mode generator described in Appendix 1 to AMC to Subpart A.

[Issue: CS-AWO/2]

APPENDIX 1 TO AMC AWO.B.CATIII.115 Performance demonstrations

ED Decision 2022/007/R

1 Limit case analysis

Demonstration of compliance with paragraph 4.1 of AMC AWO.B.CATIII.115 may be done by analysis to show that for all possible sizes of navigation error, the joint probability that the error is not detected and that the error results in the aeroplane landing outside the safe landing box as defined in CS AWO.A.ALS.106 is less than 1 × 10–5. The analysis uses the nominal touchdown distributions (lateral and longitudinal) along with the geometry factors (Svert and Slat), and the maximum allowable Pmd performance of the monitors for satellite ranging source failures and for the reference receiver fault monitor (RRFM). The nominal touchdown distribution is used to compute the probability of an unsuccessful landing given a particular size of error. This probability is then multiplied by the probability of an error not being detected as a function of E, Pmd(E). The probability of an unsuccessful landing given in error is the joint probability that the fault that causes an error, E, is not detected and the landing will be unsuccessful given an error, E:

  [1]

To form the conditional unsuccessful landing probability, a conditional touchdown distribution should be used that would result from a constant bias error in addition to the fault-free NSE and flight technical error distributions. This should be done for the full range of relevant error sizes to form the total conditional probability of an unsuccessful landing as a function of the error. The conditional unsuccessful landing probability is expressed as follows for the land-short and land-long cases:

Land short   [2]

Land long   [3]

Land with wheels less than 5 ft from the edge of the runway:

   [4]

where:

LSC is the land-short criteria (i.e. 200 ft);

LLC is the land-long criteria (i.e. 3 000 ft);

RWE is the lateral landing criteria (i.e. 70 ft);

GW is the lateral distance between the main landing gear;

is the probability density function for the longitudinal touchdown given a bias of magnitude E; and

is the probability density function for the lateral touchdown given a bias of magnitude E.

Note: Care should be taken to ensure consistency of units when making these calculations.

1.1 Computing Pmd for ranging source errors

A bound on the probability of missed detection for the ranging source error, , is defined by the performance constraint region given in ICAO Annex 10 Appendix B Section 3.6.7.3.3.2. The Pmd performance should lie below the curve defined by Table B‑76A in the SARPs, repeated here for convenience.

Probability of missed detection

Pseudo-range error (metres)

Pmd_limit ≤ 1

0 ≤ |Er| < 0.75

Pmd_limit 10(– 2.56 ×|Er| + 1.92)

0.75 ≤ |Er| < 2.7

Pmd_limit 10–5

2.7 ≤ |Er| <

Table B-76 A: Pmd_limit parameters

For example, in the case of the longitudinal touchdown requirement, the vertical position error has the largest effect on the touchdown location. The worst-case projection of a range error into vertical error, , may be used to determine the resulting limit on by substituting .

Figure 1 illustrates the relationship between Pmd_limit and the for = 5.

Figure 1: Example of the satellite ranging source Pmd in the range domain and position domain

1.2 Computing Pmd for reference receiver fault monitoring

The Pmd for the RRFM is given by:

  [5]

where:

is the maximum threshold for the RRFM monitor given by:

    Metres [6]

where:

VAL is the vertical alert limit that is used by airborne equipment to screen geometry expressed in metres.

And pBmd(x,EV) is the probability density function (pdf) of |Bj,vert(EV)| in the faulted circumstance given by:

  [7]

where dnorm(x,,) is the Gaussian pdf

  [8]

For a derivation of these expressions, see reference [22 ICAO Standards and Recommended Practices (SARPs) for the Global Navigation Satellite System (GNSS). Annex 10 to the Chicago Convention, Vol 1.] of Appendix 1 to AMC to Subpart A.

1.3 Example assessments

Figure 2 illustrates a landing-short assessment for a hypothetical aeroplane with a nominal longitudinal touchdown point of 1 500 ft from the threshold and a dispersion that can be bounded by a Gaussian distribution with σ = 220 ft. Also, a of 5, VAL of 10 metres and GPA of 3 degrees is used. Rearranging equation [1]:

  [9]

Hence, by dividing 10–5 by the Pmd curves for satellite ranging sources and RRFM, the grey ‘keep‑out regions’ shown in Figure 2 can be obtained. The assessment is then simple. If the curve for does not enter the keep-out regions, then the requirement that is met for all values of E.

An alternative approach to the analysis is illustrated in Figure 3 where the probability of an unsuccessful landing is explicitly calculated for both monitor types (ranging sources and RRFM).

Extension of these examples to the land-long and lateral cases is straightforward.

Figure 2: Example assessment of landing-short performance

Figure 3: Explicit calculation of PUL for the land-short example above

[Issue: CS-AWO/2]

CS AWO.B.CATIII.116 Head-up display fail-operational hybrid landing system

ED Decision 2022/007/R

Where a HUDLS is fitted as part of a hybrid system, its performance need not meet the same criteria as the primary system provided that it:

(a) meets the overall performance requirements, taking into account the probability that it will be used; and

(b) is sufficiently compatible with the primary system so as to retain pilot confidence.

[Issue: CS-AWO/2]

CS AWO.B.CATIII.117 Automatic ground-roll control

ED Decision 2022/007/R

(See AMC AWO.B.CATIII.115)

(a) When automatic ground-roll control or head-up ground-roll guidance is being used, the probability that the point on the aeroplane centre line between the main wheels will deviate more than 8.2 m (27 ft) from the runway centre line on any one landing shall be less than 5 %.

(b) Additionally, when the operation is predicated on the provision of fail-operational ground-roll control, the probability that the outboard landing gear will deviate to a point more than 21 m (70 ft) from the runway centre line while the speed is greater than 74 km/h (40 kt) shall be less than 10-6.

[Issue: CS-AWO/2]

CS AWO.B.CATIII.118 Landing distance

ED Decision 2022/007/R

If there is any feature of the system or the associated procedures which would result in an increase in the landing distance, the appropriate increment shall be established and scheduled in the AFM.

[Issue: CS-AWO/2]

AMC AWO.B.CATIII.118 Landing distance

ED Decision 2022/007/R

This AMC applies when using HUDs in manual CAT III operations. A relevant feature of the HUD system to consider would be flare guidance.

Relevant procedural elements associated with using the HUD would be any specific aeroplane configuration, approach speed increment, thrust management or automatic throttle / thrust speed target.

The increment of the landing distance referred to in CS AWO.B.CATIII.118 when using a HUD may be derived as follows:

(a) The configuration, procedure and speed should be those recommended in the associated procedures.

(b) The distance from the runway threshold to the touchdown point should be the distance from the runway threshold to the glideslope origin (SO) plus the mean distance from the glideslope origin to touchdown (STD) plus three times the standard deviation of the distance from the glideslope origin to touchdown (σSTD).

(c) The gross distance from touchdown to come to a complete stop should be determined in accordance with CS 25.125(b)(1) through (5), assuming a touchdown speed equal to the main touchdown speed plus three standard deviations of the touchdown speed.

Note: The main values and standard deviations considered in paragraphs (b) and (c) should be based on random variations as determined by AMC AWO.A.HUD.107. The systematic variation of parameters should cover the normal range of AFM conditions.

(d) The landing distance should be taken as the distance from the runway threshold to the touchdown point, as defined in (b), i.e. SO + STD + 3σ(STD), plus the ground-roll distance defined in (c).

(e) The landing distance should include corrections for variations in glideslope angle and variations in glideslope height at the threshold. Alternatively, these effects may be included by the use of conservative assumptions in the basic presentation of data, with the applicable ranges stated in the AFM.

[Issue: CS-AWO/2]