2. Aerodrome Operating Minima Head-Up Displays Enhanced Vision Systems
NPA-OPS 41

3. Presenters Mr Bo Eckerbert (LFV Sweden)
Chairman, AWOSG
SFO Tim Price (AEA / British Airways)
Secretary, AWOSG

4. Contents Background: Head Up Display Enhanced Vision Systems
Contents of NPA 41
NPA OPS 20 to NPA OPS 41
Stabilised Instrument Approach
Continuous Descent Final Approach
Head Up Display
Enhanced Vision Systems
Detailed Rule and ACJ Changes
Regulatory Impact Assessment

5. NPA-OPS 41 The proposal contains draft texts for:
Aerodrome Operating Minima (1.430)
Comments received post NPA 20
JAA / FAA AWOHWG work (ongoing)
Requirements for Cat III Operations (1.440)
JAA / FAA AWOHWG work
Introduction of HUD & HUDLS
Introduction of EVS
Training and qualification requirements for all of the above (1.450)

6. NPA 20 to NPA 41 OST endorsed NPA 20 in March 2004
Including:
Rule material
Explanatory Note
RIA
OST also endorsed HUD / HUDLS Rule material
Today’s presentation highlights the differences between NPA 20 and NPA 41

7. Comments from NPA 20 NPA 20 produced 290 comments
Mostly concerning Rule
Some about ACJ
Comments Response Document thoroughly reviewed over 4 meetings of AWOSG
NPA re-issued
The comments were, to a large extent, in favour of creating requirements for stabilised approaches, to avoid having to fly Non Precision Approaches using the “drive and dive” technique. There was, however, concern that the stabilised approach (SAp) concept was not sufficiently well described and also a feeling that the definition of what constituted a SAp was unclear compared with the CDFA (Continuous Descent Final Approach) concept. Furthermore, concern was raised about the conditions under which it was possible to apply an upper cut-off to the RVR requirements. It was also felt by some operators that many instrument approach procedures to aerodromes used in regional operations would fall outside the CDFA conditions, in particular those approaches where the maximum off-set angle of five degrees was exceeded, and which would thus have significantly higher minima. All of these factors meant that revision work was necessary.

8. Stabilised Instrument Approach - Background
CFIT & ALARP programmes encouraged authorities to prescribe stabilised instrument approaches: ‘SAp’
SAp: an approach which is flown in a controlled and appropriate manner in terms of configuration, energy and control of the flight path, from a pre-determined point or altitude/height, without any segment of level flight at MDA(H)
Considered to be much safer than a Non-Precision Approach (NPA) flown as ‘dive & drive’
Approach and Landing Accident Reduction Programme (ALARP)

9. Stabilised Instrument Approach and CDFA
NPA 20 / 41 defines a new variant of the Stabilised Approach: the Continuous Descent Final Approach (CDFA)
An approach with a predetermined approach slope which enables a continuous descent to DA(H)
CDFA includes precision approaches, non-precision approaches and approaches with vertical guidance (APV)

10. CDFA - Benefits
The CDFA concept aims to increase the safety of Non-Precision Approaches by eliminating level flight at MDA, ie close to the ground
Pilot workload is reduced as a/c attitude, power and energy are stabilised
One decision point for the pilot
The intention is that all approaches should be flown as CDFA (if possible)

11. CDFA v ‘Traditional’ NPADH
CDFA
MDH
NPA
ICAO
THR

12. Head Up Displays and HUD Landing Systems

13. HUD Background: Cat I RVRs can be reduced
Currently no rules in Sub Part E
But ... HUDs becoming more commonplace
Pilot-training is key
Cat I RVRs can be reduced
Cat II can be allowed without TDZ lights or centreline lights
Current approvals based on TGL 20 with formal exemptions from Sub Part E
(Similar operational credit for use of autoland)
HUDLS chosen as preferred term
The most important reason for installing a HUD is the enhancement to safety which this system offers through the improved guidance and situational information which it presents to the pilot, combined with the ability to make a much more efficient transition from inside to outside references during the critical flight-phase from approaching the DA/MDA, through landing and, in the most advanced applications, to roll-out as well.
Based on simulator trials, it is proposed that the RVR for Cat I operations can be reduced without any significant increase in the go-around rate and while maintaining, or even improving, the landing touchdown-point dispersion, or “foot print”, compared with no-HUD operations using the current aerodrome operating minima. In the same way, it is proposed that Cat II operations can be allowed without the need for touch-down zone lights or centre line lights.
 Today there are several operators which have approval to use HUDs, in particular for Cat II and III A operations. These approvals are often based on JAA TGL 20 combined with the current Subpart E, which often will result in formal deviations from existing JAR-OPS since it does not currently permit manually-flown Cat II or IIIA approaches. For this reason, and also in order to take full advantage of the capabilities of HUDs and HUDLS, there is a need to update JAR-OPS, Subpart E.
It has also been recognized that what can be achieved through the use of a HUD can also be achieved by the use of auto-land systems which offer improved precision in the tracking of the lateral and vertical paths compared with manual flight. There is also a reduction of crew workload, which improves the capacity to monitor the progress of the flight and to make use of the external references. For these reasons it is reasonable to allow the same operational credits to auto-land systems.
 To avoid the use of any acronym which may be propriety protected, the term, HUDLS (Head-up Display Landing System) has been chosen, which is also used in the certification requirements.

14. HUD - Proposal Manually-flown Cat II approaches
Manually-flown Cat IIIA approaches
‘Lower than standard Cat I’
DH of 200ft but min RVR of 400m on current Cat I runways
‘Other than standard Cat II’
DH of 100ft, min RVR of 350m on Cat II runways which lack TDZL and CLL
Equipment and airframe requirements
Training requirements
Credits for autoland ops of the same values as HUDLS

15. HUD - Safety Safety levels not reduced with reduced RVR minima:
Compensation by improved guidance (HUD or autoland)
Adequate visual reference still required
Simulator trials:
Go-around rate not significantly increased
Landing footprint is equal or better
Suitable ILS performance still required
·    The reduction of the minimum RVR and the removal of the requirement for touch-down zone and centre-line lights are considered to be fully compensated for by the improved guidance offered by the HUDLS or by the reduced workload and improved precision delivered by the auto-land system.
·    The reduced RVR requirements only allow the possibility of continuing the approach beyond the outer marker (or equivalent). The necessity of having adequate visual references (as specified in JAR-OPS 1) to be allowed to continue the approach below DA is maintained.
·    Simulator trials have shown that the go-around rate should not be significantly increased.
·     Simulator trials have also shown that the landing foot-print (ie the dispersion of actual touch-down points within the landing area) is equal to or better than that for conventional operations with current RVR values.
Consideration has been given to the need for suitable ILS performance in order to ensure that the ILS signals will support these operations.

16. HUD - Harmonisation Other than standard Cat II in line with FAA
Lower than standard Cat I deviates from ICAO, but...
ILS requirements specified
Difficulty with label vs aerodrome requirements
Current categorisation under debate in AWOHWG and OPSP
Current categorisation hinders operators from installing equipment
The Cat II operations without touch-down zone and centre line lights are in line with FAA Order A, except that the FAA will require centre-line lights for RVR values of 450 m or less. However, the FAA are working on a new version of the order, B, in which the requirement for centre-line lights will be removed, which in fact means going back to the original set of requirements as laid down in order The Cat I operations with RVRs less than 550m will be subject to further discussions as part of the harmonization process.
The lower than standard Category I operation is in line with ICAO definitions regarding the minimum DH (200 ft); however, by permitting minimum RVR values of less than 550m, it deviates from the ICAO Cat I definition. This deviation is identified in the naming of the operation. The only way to avoid deviating from existing ICAO definitions would be to label the operation as Cat II. It should be noted that, for lower than standard Cat I operations, the ILS is required to be a facility without known deficiencies able to provide guidance all the way to the threshold. For RVR values less than 450 m, the ILS is required to comply with Cat II standards and there is a requirement for touch-down zone and/or centre-line lights. The main argument against putting a Cat II label on the operation is the risk that aerodrome operators may be uncertain as to whether to allow this, so called “Cat II operation” on their aerodrome.
The labelling will not affect safety standards and there is a need to start to give credit for the capability of on-board equipment. The current categorization is under debate both in the FAA/JAA AWOHWG and in ICAO OPSP. The current categorization is an obstacle to development and a hindrance to encouraging operators to install equipment which will increase the safety as well as the efficiency of their operations.

17. Enhanced Vision Systems

18. EVS
Popular with the AWOSG!
EVS Sensor window

19. EVS - Background New technology – currently IR sensor-based
Rule material required
Members of the AWOSG flew EVS-equipped aircraft to obtain experience of system in use
Approaches flown in variety of conditions
Fog, mist, snow
Night, mountainous terrain
Benefits of the system can vary depending on met conditions (certain IR wavelengths absorbed by water drops in atmosphere)
The current systems use an infrared sensor and image processing to produce a real-time image of the outside world displayed to the pilot on either a HUD or a head-down display.
There is no specific regulation within JAR-OPS to address the use of EVS. Without a regulation, operators cannot obtain any operational benefit from voluntarily fitting EVS equipment to their aircraft. Without regulation and guidance, there may be inappropriate use of the systems, which could reduce safety. There is therefore a need to develop a rule within JAR-OPS which covers the use of EVS. Originally, a request was made by the manufacturers that the JAA should develop a rule covering the use of EVS during approach operations, which is, clearly, an area where risks need to be closely examined and controlled.
During the evaluations, approaches were flown in a variety of conditions of low visibility including advection fog, radiation fog, mist and snow showers, as well as at night in mountainous terrain. EVS provided additional situational awareness during taxiing at night, in low visibility and during approaches in VMC at night. Experience showed that, while EVS was capable of providing benefit by allowing earlier acquisition of required visual references on approach (compared with un-augmented aeroplanes), such benefits could be limited, or even non-existent, on some occasions, and significant on others depending on the meteorological conditions prevailing at the time the approach was flown

20. EVS – Rule Accommodate variety of performance
HUD believed to be essential element of total EV System
Two Decision Gates
Enhanced view of visual references allowed at normal DH
‘Natural’ (ie unaugmented) view required by 100ft ARTE
Controlling RVR reduced to give credit for EVS
No ICAO rule at present – OPSP may draw on JAA and FAA work
It was concluded that a rule which tried to cover all the variations would be too complex. However, a rule which broadly covered the average EVS performance, but which was constructed to be self-limiting, was desirable. A HUD is considered to be an essential element of any EVS for which some form of operational credit is sought.
In order to gain a benefit whilst using EVS during an instrument approach, some form of allowance is required to use the enhanced visual references (ie those provided solely by the EVS) instead of the natural view of the visual references. However, at some point prior to the landing, when using the currently-existing EVS, a natural view of the visual references is required. It was concluded that the required visual references must be visible by 100 feet Above Runway Threshold Elevation (ARTE), at the latest, to give sufficient time for the pilot to adjust to the visual scene before commencing the landing flare. This represents a harmonised position with the FAA. With the proposed rule, a pilot using EVS may continue an approach below the normal DA(H) using the EVS view of the required visual references but must have a natural view of those references by 100 feet.
 EVS allows earlier acquisition of the visual references in many conditions. If an approach is flown at the normal RVR limit then there is little benefit in using EVS, because the likelihood is that the natural view of the visual references will be acquired prior to MDA(H) / DA(H). The controlling RVR for the approach must therefore be reduced in order to gain benefit from the EVS. Therefore, it was decided to take a conservative approach in developing the new rule and set an RVR which would give some benefit for the majority of situations, rather than trying to accommodate the best-case scenarios. This average approach is consistent with the principle of setting RVRs for normal (ie non-EVS) approaches which lead to an acceptably low missed-approach rate.

21. Detailed Rule, Appendix and ACJ Changes

22. Rule Changes 1.430 Aerodrome Operating Minima – General
(a) Note deleted
(b)(9) Refers to flight technique = CDFA
(d)(1) Mandates use of CDFA (inc SAp)
(d)(2) Prescribes RVR add-on if approach not flown as CDFA
(d)(3) Allows Authority to exempt operator from add-on prescribed in (d)(2)
(d)(4) Limits use of exemptions
1.430 Aerodrome Operating Minima – General
JAR-OPS (a). The note was deleted since the in-flight calculation of minima for a non-planned alternate is already covered in the requirements for Operations Manuals but was subsequently reinstated as a result of the NPA OPS 20 in the form a new sub-para (a)(2) in order to avoid using notes in the rule.
JAR-OPS (d)(4) limits the exemptions to cases where CDFA is impracticable for the time being. The purpose is to allow on-going operations, with an adequate safety level, to continue, where compensating factors (such as crew training and experience) apply. The intention is not to preclude a new operator from engaging in such operations but the exemptions are not intended to be used for ad-hoc flights.

23. Rule Changes 1.430 Aerodrome Operating Minima – General
(e)(1) Prescribes use of either Appendix 1 (Old) or (New) until end of transition period
(e)(2) and (e)(3) similar exemptions to (d)(3) and (d)(4) but related to use of upper cut-off values [Tables 5 and 6 in Appendix]

24. Rule Changes 1.435 – Terminology 1.440, 1.450, 1.455, 1.460
Clarify relationship between SAp and CDFA
Introduce and/or clarify definitions relating to HUD & EVS
1.440, 1.450, 1.455, 1.460
Introduces:
‘Lower than Standard Category I’
‘Other than Standard Category II’
(NB: these definitions previously endorsed by OST)

25. Appendix 1 to 1.430 Philosophy:
Two versions of the Appendix (Old & New) active in parallel for 3 years
Operators who cannot comply with CDFA concept immediately can use existing criteria
App 1 (Old) will be withdrawn after 3 years

26. Appendix 1 to 1.430 Table 2 ‘Assumed engine failure height’ reinstated
(b)(1) ICAO terminology for GNSS introduced
(b)(2) Use of MDA(H) as DA(H)
(b)(3) APV defined; ‘OCL’ deleted
(b)(4) ‘Cat I Precision’ deleted; DH is not exclusive to precision approaches
(b)(5) Reference to procedure minimum in AFM added
(b)(6) ‘Non Precision’ deleted
Para (b)(2). The use of the MDH as a DH is a consequence of the method of not allowing level flight at MDH (or multiple step-downs during non-precision approaches). This method is widely used among major European, commercial operators and more than half of those operators do not apply an add-on to the DH. It was however felt to be prudent to remind the recipients of this NPA that the application of MDH as a DH is a matter which needs to be evaluated and which may need to be discussed between the operator and the Authority. This matter is currently being reviewed by the ICAO OCP and OPSP. It is the firm opinion of the AWOSG that, when flying an approach as an SAp and CDFA, the procedure’s minimum altitude (height) should be referred to as a DA(H), irrespective of the type of approach being flown. This terminology is entirely appropriate when it is realised that there can be, by definition, no level-flight segment at the procedure’s minimum altitude (height). Therefore, a pilot flying such an approach will reach the DA(H) and decide whether to land or go-around; hence, it is a decision altitude (height).
Para (b)(3). The definition of APV (Approaches which utilise lateral and vertical guidance) has been included since the forthcoming amendment to Pans-Ops contains this type of instrument approach and the RNAV/LNAV minima in table 3 may be used for such approaches.
Para (b)(3)(ii). The term OCL was deleted from Pans-Ops long ago and has become obsolete. It is proposed to delete the term from JAR-OPS 1 as well. In the few cases where it is still used, it is considered that the operators are sufficiently aware of the situation to cope with it. .

27. Appendix 1 to 1.430 Table 3 system minima revised considerably:
RNAV (VNAV) deleted
NDB minimum raised
NDB/DME added
VDF raised
(c)(1) Outlines criteria which approaches must fulfil to use Tables 5 & 6
Max approach slope (Cat C & D a/c) limited to 3.77 degrees (=400ft per nm)
Table 3. The system minima have been revised considerably. RNAV (LNAV and VNAV) were introduced to open up for the use of GNSS-based approaches. While RNAV/LNAV is retained RNAV/VNAV has been removed since it is felt that the only current application of RNAV/BaroVNAV is covered by the APV criteria. The minimum for NDB has been raised and it could be argued that these two changes together constitute a reason for including this version of the table in Appendix 1 (old) as well as Appendix 1 (New). The reason for raising the NDB value is that this type of approach involves a considerable degree of imprecision and pilot work load. If the NDB is combined with a DME, the control of the vertical flight path is improved and, for that reason, the minima can be lower. The same rationale was used for raising the VDF minimum.
Para (c)(1). The paragraph outlines in detail the criteria which individual approaches must fulfil in order that the RVR/Converted Met Visibility (CMV) listed in Tables 5 and 6 can be used.. One important change is that the maximum limit for an approach slope is changed to 3.77 degrees for Cat C/D aeroplanes. The change is made following proposals from the FAA; 3.77 degrees, equalling 400 ft per nautical mile, is the upper limit for the approach slope for straight-in approaches in the USA. The whole issue of steep approaches is on the agenda for the AWOHWG, but still remains to be discussed.

28. Appendix 1 to 1.430
(d)(2) Note 2. Explanation of how RVR values calculated (methodology moved to ACJ)
(d)(5) Conditions for using RVR <750m for Cat I
(d)(6) Credits for HUDLS and autoland
Table 4. Changes made following comments from FAA
Table 5. New minima
Developed during harmonisation work with FAA
Logical and consistent; rounding values changed
Formula used:
Required RVR/Visibility (m) = Minimum height (ft x / tan) - length of approach lights [ = approach angle]
But... should the formula be in the ACJ?
(d)(2): explanation on next slide
(d)(5): proposals a direct result of harmonisation work with the FAA.
Table 5 – Bo may care to comment?

29. Appendix 1 to 1.430 – Table 5 (part)
DA(H) or MDA(H)
FALS
IALS
BALS
NALS
See para (d)(5) and (d)(6) about RVR < 750 m Ft
Metres 
200 -
210
550
750
1000
1200
211
220
800
221
230
231
240
241
250
1300
251
260
600
1100
261
280
900
281
300
650
1400
301
320
700
321
340
1500
The starting point is an angle of 3.00 degrees, which is normal for Cat I approaches. The default value for the calculation angle is increased in increments of 0.10 degrees with each “height band” in the Table until the upper value of 3.77 degrees (equals 400 ft/NM) is reached (in the line ‘301 – 320 ft’). Thereafter 3.77 degrees is used as the angle value in the formula for all remaining height bands, which reflects the probability of having higher approach angles with higher MDA(H)/DA(H) values.

30. Appendix 1 to 1.430
Calculation of visual segment
Bo to explain?

31. Appendix 1 to 1.430 Table 6: Upper and lower cut-off RVR values Upper?
Type of approach and CDFA
Lower?
Aircraft Category and approach type
ILS facility requirements greatly standardised
Table 6 contains the upper and lower cut-off values to the RVR. The lower cut-off is controlled by the category of aircraft and takes the type of navigation facility on which the approach procedure is based into account. Whether or not an upper cut-off can be applied depends on the quality of the approach procedure. Well designed and well equipped approaches can apply an upper cut-off. If an upper cut-off can be applied, it means that approaches with high MDA(H) values do not have to use very large RVR values.
Following comments, the ILS facility requirements have been greatly standardised and described either as ‘restricted’ or promulgated as at least Class I/T/1. This will reduce the burden on the operators significantly, because, if no notice to the opposite is promulgated in the AIP, an ILS may be assumed to be unrestricted, and the classification is gradually being implemented. The application of the LVP protection of the ILS is independently regulated in Subpart E as before. It is emphasised that, for manual landings, the use of the ILS below DH is supplementary to the use of visual cues as the primary references, and those visual references constitute the sole cues (except in the case of the EVS) on which to decide to whether to continue the approach. The use of the ILS is intended to improve the safety of an approach by providing additional guidance and reduction of the pilot work load.

32. Appendix 1 to 1.430 – Table 6 Facility/ Conditions Aeroplane category
RVR
(m)
Aeroplane category A B C D
ILS, MLS, GLS, PAR and APV
Min
According to table 5
Max
1500
2400
NDB, NDB/DME, VOR, VOR/DME, LLZ, LLZ/DME, VDF, SRE, ,RNAV(LNAV) with a procedure which fulfils the criteria in paragraph (c)(2)(ii):
750
For NDB, NDB/DME, VOR, VOR/DME, LLZ, LLZ/DME, VDF, SRE, RNAV(LNAV):
- not fulfilling the criteria in paragraph (c)(2)(ii) above, or
- with a DA(H) or MDA(H)  1200 ft
1000
1200
According to table 5 if flown as a CDFA, otherwise an add-on of 200/400 m applies but not to a higher value than the upper limit of the table.

33. Appendix 1 to 1.430 – Para (c)(2)(ii)
CDFAs with a nominal vertical profile, up to and including 4.5 for Category A and B aeroplanes, or 3.77 for Category C and D aeroplanes, unless other approach angles are approved by the Authority where the facilities are NDB, NDB/DME, VOR, VOR/DME, LLZ, LLZ/DME, VDF, SRA or RNAV(LNAV), with a final-approach segment of at least 3NM, which also fulfil the following criteria:
(A) Final approach track is off-set  5 degrees, except that, for Category A and B aeroplanes, the upper cut-off value (RVR 1500 m) applies if the final approach track is off-set  15 degrees; and
(B) The FAF or another appropriate fix where descent is initiated is available, or distance to THR is available by FMS/RNAV or DME; and
(C) If the MAPt is determined by timing, the distance from FAF to THR is  8 NM.

34. Appendix 1 to 1.430 (d) [Several places]:
Minimum autopilot disengage height:
80% of DH, but not less than 150ft ARTE
Note 4 to Table 8 deleted; AWOSG believes should be part of Sub Part F
(e) & (f) Introduction of HUDLS (and some EVS) material:
‘Lower than standard Cat I’
‘Other than standard Cat II’
Note 4 is: If operations without autobrake and/or anti-skid system are acceptable to the Authority in accordance with the MMEL and reflected in the approved MEL and the list of equipment required for Cat II/III operations, the operator shall make appropriate additions to the landing distance required and prescribe appropriate limitations as to the braking action. Where available, this information must be based upon the AFM.

35. Appendix 1 to 1.430 (h) Introduction of EVS-specific material
2 decision gates as outlined earlier
Steep approaches still to be discussed in AWOHWG
(j) [formerly (g)] Circling:
One set of minima presented
ACJ being developed to clarify circling in more detail
(l) Conversion of Met Vis to RVR no longer permitted below 800m
In what was formerly Para (g) now Para (j), circling minima, the relation between the minima for the instrument part of the approach and the circling part was explained, such that the higher of the two minima values for either the instrument part or the circling part was controlling for the approach. Following comments this connection has been abandoned. It is not considered logical to tie the two phases of the circling approach in this way since the operational needs are different. A separate ACJ will soon be presented which clarifies the conditions for circling approaches in more detail.

36. Other Appendices
1.440:
Clarification of requirements needed to qualify for Cat III
1.450:
‘HGS’ abandoned, now HUDLS
HUD and EVS will create additional training requirements
1.455:
References to HUD and EVS added

37. ACJs 1.430 [edited]: Appendix 1 New [new]: 1.430 (h) [new]:
Explains SAp and CDFA concepts
Edited in response to comments (53, of which 43 accepted)
Appendix 1 New [new]:
Explain derivation of new minima
Cat I operations <750m RVR
Single-pilot ops
1.430 (h) [new]:
Describe EVS and concept of operations

38. Regulatory Impact Assessment

39. RIA Scope: Relevant ICAO / JAA decisions: Discussed already SAp / CDFA
HUD (JAA TGL)
HUD minima: conflict with Annex 14 (RVR not DH)
NPA may well be used by ICAO OPSP
Operations <550m RVR: definition (Cat I or Cat II?)

40. RIA Objectives: Who will be affected? Enhance safety – especially CDFA
HUDLS / autoland
EVS
Who will be affected?
All JAR-OPS operators, and probably most GA
Training

41. RIA Options Do nothing Introduce Rule, but no reduction in RVR
Introduce Rule and reduce required RVR
Mandate CDFA / SAp, but no change in AOM
Mandate CDFA / SAp and change in AOM

42. RIA Impacts identified: Safety Economic Harmonisation Environmental
Social (nil)
Other Aviation Requirements (nil)

43. RIA Consultation: Summary & Final Assessment Industry Flight-crew FAA
Comments Response Document
Summary & Final Assessment

44. Questions?? Bo Eckerbert (bo.eckerbert@luftfartsstyrelsen.se)
Tim Price