RNAV GNSS Approaches - Legality & Min Eqpmt

[Zenj]

Hi

I have seen approaches in Nairobi and Dar-Es-Salaam (HKJK and HTDA) which are RNAV (GNSS) approaches, which do not depend on any equipment on ground.

What is the minimum equipment on board to do these approaches ?

It seems some aircrafts with GPS and with NAVCARD from Jeppesen which has these approaches in it are doing the approaches even at night or in bad weather.

I think there must be a standard or minimum equipment installed for these type of approaches.

[Dan Winterland]

For a start, your airline has to be cleared to do the approaches (as mine is) and then almost certainly the crews have to have some training in GPS approaches.

Then, for the approach this is what we require (Airbus):

Two operable FMGCs
GPS Primary displayed on both MCDUs.
GPS 1 and 2 in NAV mode (Checked on theGPS Monitor Page)
RNP 0.3 (0.37 prior to the IF)

WRTo Failures after the IF:

With GPS Primary lost on one side - Use the other AP/FD.
GPS Primary lost on both sides - Go around.
FM/GPS POS DISAGREE message - Go around.

[Zenj]

Dan,

Thanks for the input.

Anyone from Boeing perspective ?

So that means with our normal GPS on a B737-200 its prohibited !

Somewhere written ? Annex or ICAO DOC please ?

[reynoldsno1]

The receiver must be IFR certificated - FAA TSO C129 or equivalent - I think its TSO C143 for WAAS capable receivers, I could be wrong...

[discountinvestigator]

For GPS approaches:
What is the RNP certification status for the aircraft? If you have no RNP value then forget it. Do you know what it means? If not, NO.

What are your procedures for RAIM monitoring, if you do not understand it, you are not qualified!

What is your MEL for a set RNP value? What are your flight deck procedures for a change in RNP during flight.

A clue very few 737-200s are equipped for this type of approach, if any.

[Dan Winterland]

Zenj, discount aviator has some good points. My aircraft type is the A320 which lends itself to the GPS apprach technique. I wouldn't like to do it in anything other, and that includes the glass Boeing type I used to fly. I would say a proper FMS system such as the Airbus FMGS with an associated instrument system iis essential. For those who don't know the Airbus, you can press the approach button on the flight control panel as if you were flying an ILS, and this puts the aircraft into FINAL APP mode which allows you to fly a non precision approach with guidance as if it was an ILS.

You mention a normal GPS. What is a normal GPS - do you mean a Garmin 250 type of unit?

[OzExpat]

What a load of old cods. There is a SIGNIFICANT difference between RNP approaches and the standard GNSS approaches. For a start, RNP doesn't have any real significance down to a value of 0.3 as this is the final approach tolerance for a standard GNSS non-precision approach. Below 0.3, RNP has a very definite significance and requires aircraft to be specially certiificated by type.

Some people might be interested to know that there are TWO very well known RNP approaches in different parts of the world. One in Alaska and the other in New Zealand. Both are suitable for B738 that are operated by specific airlines and are not available to other airlines who cannot meet the required certification standards.

For those who "push a button" to fly an RNAV (GNSS) approach with a pseudo glideslope, I hope that your system does not bust the MDA. There is a difference is you're flying an RNAV (RNP) approach, but you'll only know about that if your airline is certified for it - and if they've certified YOU for it.

[Lower Hangar]

RNP Approach-A320

Just finished putting RNP on an A320 sim in TLS. Conditions for enabling are:
a. Non precision approach programmed in the FMGC ie DEST RWY is not ILS.
b. APPROACH mode on MCDU has been activated.
c. LS not selected on FCU
d. RNP selected on MIP.
e. GPS Primary available
Guidance is provided by LAT and VERT DEV scales on the PFD .A 'box' guidance symbol is centred on a LAT scale of +/- 0.2nm and +/- 200' for VERT dev.

[Dan Winterland]

Zenjs' original question was reagarding RNAV approaches. I think you answered his question when mentioning the certification requirements. And I don't know of many automatic systems which prevent you busting minima. It's up to the crew - as with any approach.

[BBeeckmans]

Rnp Apch Mel

Gents,

are you familiar with

• FAA AC90-105 or EASA AMC20-27 for RNP APCH and
• FAA AC90-101 or EASA AMC20-26 for RNP AR APCH also SAAAR

you can find these on FAA: Home or EUROCONTROL Navigation Domain - Document Library

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