RNAV Approaches

Use of RNAV (GNSS) for Non Precision Approach.

Paul Willis, Managing Partner, Cyrrus Associates,

Dr. E. Matsoukis, Assoc. Prof., University of Patras, and

S. Poulimenakos, Air Traffic Controller.

1 Introduction.The use of RNAV (GNSS) as an alternative to traditional ground based radio navigationalguidance is an exciting development within the aviation and airline industry. The use RNAVrepresents a significant development towards the use of GNSS technologies as a replacementto traditional ILS / MLS precision approaches. Although the use of GNSS for precisionapproach has still to be accepted by the International community for many reasons, the likelydate being not until the year 2015. However, the use of RNAV for non-precision approachesstill represents an important milestone in the transition from traditional navigational techniquesto satellite based technology. The use of RNAV for non-precision approaches has significantbenefits as it provides a cost effective navigation solution to runways that have no traditionalnavigational infrastructure.

2 What is RNAV GNSS.RNAV GNSS non-precision approach techniques make use of Global Positioning Satellites(GPS) to determine the aircrafts position on the final approach to an airport. RNAV / GNSSprocedures are predicted on continuous descent approach (CDA) rather than stepped descent.This offers environmental advantages in addition to reduced pilot workload together with astabilised approach with associated safety benefits.

3 Operational Considerations.A non - precision approach traditionally uses a ground based navigation facility providing theaircraft with a bearing and distance to a fixed point, usually on the airport. The aircraft usesthis guidance information along with a published procedure (national AIP and / or Jeppeson) tofly to an altitude on the approach to the airport, this will normally be to a minimum decisionheight (MDH) of between 300ft 400ft. This is however dependent on the surrounding terrain.This type of approach is reliant on ground base infrastructure being available and to anacceptable signal quality to provide aircraft guidance within a declared tolerance.

The use of RNAV for non-precision approach requires an aircraft to be fitted with a GNSSairborne receiver that is certified to FAA TSO C129a Class A1 (standalone) standards orB1/B3 for Flight Management System (FMS) integrated equipment. RNAV (GNSS) approachmode can only be selected when using a certified (ie Jeppeson) database. It is not possible touse manually inputted waypoints, except for flight inspection.

The tolerances applied to an aircraft making a NPA are an alarm limit of 550m, with 10seconds to alarm at the declared MDH. GNSS position fixing will achieve a horizontal positionaccuracy of 100m of 0.05NM with a 95% probability. Compare this with a Non DirectionalBeacon that has a bearing uncertainty of 5 degrees, this equates to a horizontal error of +/-0.5NM at a range of 6NM. It should be noted that the position error of GNSS is uniform wherea ground based navigational facility achieves greater accuracy as the aircraft approaches thebeacon.

4 Considerations.In order for RNAV GNSS non-precision approaches to be Internationally acceptably to theaviation industry more investigation and analysis is still required by manufactures, airlines,national regulators and technical institutions. One of the main problems is that RNAVequipment contains proprietary algorithms and therefore there is insufficient data available atpresent to validate target levels of safety. Furthermore database integrity is a further problemthat has not been sufficiently addressed to the satisfaction of many national regulatoryauthorities. In addition RNAV/GNSS NPA does not form part of a pilots instrument ratingtraining and testing in most (if any) countries. Training and testing is the responsibility of theoperator. This will probably change as GNSS NPA becomes more widely accepted. Most pilotshave heard of it, but very few have done it.

5 Future Activities.Cyrrus Associates Limited with Flight Precision Limited has recently developed a RNAV NPAprocedure for a UK Civil Airport. This procedure will be published within the UK AIP and hasbeen subject to rigorous review by the UK CAA Safety Regulation Group. Having publishedthe procedure, Cyrrus Associates Limited along with their partner Flight Precision Limited willconduct regular flight tests and gather flight data to evaluate the published procedure. This willenable further analysis and investigation to be carried out with the goal to develop additionalIFR procedures using GNSS in the future.

Cyr rus Assoc i a te sL im i ted

RNAV (GNSS) for

Non Precision Approach

By Paul Willis Cyrrus Associates

&

Sarandis Poulimenakos University of Patra


Overview

C o s t benefits & advantages

What is BRAV

Operational Considerations

C o n s traints

Next Steps


A rea Navigation

Traditional Area Navigation is based on.

V O R / DME o r NDB g round based rad io beacons .

T h e V O R /D M E a n d / or NDB provides the aircraft witha guidance s ignal that a l lows navigat ion by means offlying a bearing or radial to f ixed point. This isnormal ly to the overhead of the ground radio beacon.These beacons are pos i t ioned so that an a i rcraft canfly declared routes within the national airspace.

5

5

10

SCALE 1:650'0000

0

NM

KM

SAT VOR / DME 109.6 SAT 3755'00.48" N 02354'51.84" E

KEA VOR / DME 115.0 KEA* 3733'26.13" N 02417'55.99" E

KORINTHOS NDB 392 KOR* 3755'56.14" N 02255'57.82" E

DIDIMON VOR/ DME 117.2 DDM* 3728'40.08" N 02313'01.77" E

ATHINAI VOR / DME 114.4 ATH* 3754'03.15" N 02325'25.81" E

VELOP BADEL

3810'10" N02433'20" E

PIKAD 3803'47" N02241'57" E

ASTOV 3725'03" N02232'06" E

NEMES 3742'05" N02234'43" E

3810'10" N02344'08" E

277

R 292 DDM

9000 FT

R 261 DDM

R 165

KEA

R 359

ATH

R 266 KRO

NEVR

A 1J

11

R 027

KRO

R 013

KRO

13

33

NEMES 1J

28SOREV 1J

KVR

SUN

15 20

10

16ABLON

1J

303

14

RILIN 1J

PIKAD 1J

SPA

R 048 S

AT

5DM

EK R

O

5000 FT 6000 FTSOREV

1J

6000 FT

20R

168 DDM

ASTOV 1J33

EGN

NEME

S 1J

35

VELO

P 1JASTO

V 1J

R 221

ATH

RILIN 1J

35PIKAD 1J

R 271 ATH

VELOP

1J

4 0 0 0 FT

NOTES:

1. THE RESTRICTION IN CLIMB TO A MAXIMUM ALTITUDE( E.G. 6000 ft ) IS APPLIED IN CASE OF RADAR FAILURE AND IF NOT OTHERWISE INSTRUCTED BY ATC.

2. RADAR ANTENNA TOWER AT 745 FT ( 227 M ) LOCATED 1400 M TO THE EAST OF 21 L THRESHOLD.

745

6000 FT

6000

FT6000 FT

1100 FT

NOTE 2

An example of th is is the Standard InstrumentDeparture for 03R S p a ta A irport.


A rea Navigation

What is RNAV?

B R N A V i s B asic A rea Navigation.

Makes use of Global Position Satellites(G P S ) to determine the aircrafts position in3 dimensions (x,y,z). If way points gavebeen predetermined then an aircraft trackcan be established enabling the aircraft tonavigate between any 2 fixed points.


A rea Navigation

Way Point 1

Way Point 2

Intermediate Fix

Intermediate Fix

RNAV aircraft posit ion f ixing,showing an aircraft navigatingbetween two Way Points


Operational C o n s traints

A irborne GNSS Receiver.

Aircraft R e c e iver has to be cert i f ied to FAAT S O C 1 2 9 a C l a s s A 1 ( s tanda lone) o r B1/B 3for Fl ight M a n a g e m e n t S y s t e m ( F M S )integrated equipment.

R N A V (G N S S ) approach mode can on ly bese lected when us ing a cert i f ied (J eppe son )da tabase .


A rea Navigation

Traditional Area Navigation is based on.

V O R / D M E o r NDB ground based radio beacons.

The VOR/DME and / or NDB provides the aircraftwith a guidance signal that allows navigation bymeans of flying a bearing or radial to fixed point.This is normally to the overhead of the groundradio beacon. These beacons are positioned sothat an aircraft can fly declared routes within thenational airspace.


P o s ition Accuracy (Radio Beacon)

Accuracy Requirements (NDB).

N D B B e a c o n

Assuming the NDB has abearing error of +/- 5 degrees.A t 6nm this equals a horizontalerror of 0.5NM.

0.5

nm

Range 6 nm


P o s ition Accuracy RNAV

Accuracy Requirements (RNAV).

100m

A ircraft track

Posit ion Error Boundary 95% Probabil i ty

Posit ion accuracy factor of 10 t imesbetter than NDB at 6NM.


C o s t Benefits & Advantages

RNAV is not reliant on any ground infrastructure,this is of particular benefit to those airports thatoperate without any navigational facilities on oneor both runways.

Given the challenging terrain and number ofairports in Greece RNAV Non PrecisionApproach can offer real benefits to the airlineoperator, approach minima of 300-400 ft.

In the future both Standard InstrumentDepartures and Arrivals can be based on RNAVmaking better use of airspace.

Design missed approaches using RNAV, shorterroutings, therefore greater fuel savings.


C o s t Benefits & Advantages

RNAV Non Precision Approach Procedures aredesigned on a continuous decent approach(C D A ) rather than a traditional stepped descent. This has Environmental benefits

(less noise).

Reduced Pilot workload during finalapproach.

S tabilised approach & Safetybenefits.

ATHINAIGP/DME 111.10I-ATRCH 480X 3755'40.08" N02356'56.40" E

LLZ 111.10 KRO

SAT

KEA VOR/DME 115.0 KEA * 3733'26.13" N 02417'55.99" E

R 197

KEA

MNM

ALT500

0 FT

KMNM

0

0

SCALE 1:500'000

2 4

2 4 6 8 10

1 3 5

1 3 5 7 9

293

PERES30 DME ATH 3724'13.36" N02339'10.74" E

BEARINGS ARE MAGNETICALTITUDE AND ELEVATIONSARE IN FEETDISTANCES ARE IN NMLATITUDE AND LONGITUDEIN WGS 84

03L

03R

KVR

SUN

088

ILS RDH54.1 FT

TRANSITION ALTITUDE9000 FT

3 DMEI - ATR

100 NM 5

SPAVOR / DME

515 102030 2535 15

118

12 NM EGN

R 062 DDM

25 NM

R 185

ATH

15 NM

R 331 KEA

26 NM IF 19 DME I - ATR 3740'19.00" N02342'21.70" E

034

034

R 220

SPA

FAF 9 DME I - ATR 3748'20.30" N02349'54.75" E

5 DMEI - ATR

FAF 9 DME I - ATR

IF 19 DME I - ATR13 DME DDM

5000 FT

4000 FT 4000 FT

3200 FT

DDMVOR/DME

PERESEGN NDB 1917 FT

034

GP 3

MISSED APPROACH:Climb straight ahead. At 3DME (passed the station)I - ATR turn right. InterceptR 331 KEA, proceed toKEA VOR/DME and hold.Climb to 5000 FT, climbgradient 3 % until passing1200 FT. (SEE NOTE)

Nautical Miles from THR (THR RWY 03 R) ELEV 271 FT (THR RWY 03 R)

10 NM

SPAVOR/DME 117.5SPA 3755'04.80" N02356'16.80" E

ATHINAI VOR/DME 114.4 ATH* 3754'03.15" N 02343'42.76" E

MNM SECT ALT293 - 088 SPA VOR

6000 - 25 NM


3500 - 25 NM


4500 - 25 NM

AIGINA NDB 382 EGN* 3745'51.06" N 02325'25.81" E

DIDIMON VOR/DME 117.20 DDM* 3728'40.08" N 02313'01.77" E

Firstly lets look at a traditional IL SIns trument Approach

Now for a RNAV approach.

D408 / 2.5O C N L / 5.6

D409 / 3.4L E E M I N G C M A T Z

127.750

001 40'W 001 30'W 001 20'W 001 10'W

001 40'W 001 30'W 001 20'W 001 10'W

1

0

0

NM

KM 432

21 43

5 6 7 8 9

5

10

SCALE 1:350'000

N V E 1 1 5437'58.44" N00111'49.89" W

1 0 N M5440'N

5430'N

5420'N

5430'N

5420'N

IA W P 1 N V N 1 1 5440'50.00" N00119'09.03" W

0 52 M A X IAS2 1 0 K T

M N M A L T2500 FT

400

400

7 00

1000

1 3 0 0

400

400

IA W P 2 N V E 1 3 5439'19.09" N00109'17.97" W

IA W P 3 N V E 1 2 5433'28.05" N00107'33.99" W

IW P N V N 0 8 5436'02.69" N00115'27.46" W

F A W P N V E 0 4 5433'20.30" N00120'32.52" W

M A W P N V E 0 1 5431'18.67" N00124'21.34" W

N V W 0 4 5431'13.19" N00132'41.68" W

N V W 0 6 5426'17.68" N00133'43.43" W

5440'N

232

232

3 0 4

161

232


Constraints

All survey data, terrain, runways, reference datumsand obstac le data must be surveyed to theInternat ional standard WGS-84. This has not yetbeen completed in G reece .

R N A V G N N S R e c e ivers contain proprietary software& algorithms. G reater analys is by manufactures andtechnical institutions is sti l l required to ensure thatTarget Levels of Safety are achieved (better than1x10 -7)

R N A V is rel iant on the aircraft s certif ied data base,proving the integrity of the database to the nationalregulator maybe difficult.

R N A V N P A d o e s n o t form part of a pilotsinstrument rat ing in many countr ies.


Next S teps

Cyrrus Associates along with their strategic partnerF light P recis ion Limited has designed the f i rstpub l i shed RNAV Non Prec i s ion Approach in theUn i ted K ingdom.

F light P recis ion Limited, being the UK l icensed f l ightinspector wil l undertake pi lot training and extensivefl ight inspection of the promulgated procedure togather more data for future analysis & val idation.

W ith the UK regulator develop procedures andmethods to enable addit ional IFR procedures todeve loped us ing RNAV pr inc ipa l s .

Part ic ipate with industry and technicalinst itut ions to develop robust safety analysis andvalidation of aircraft equipment.

Documents

RNAV Approaches