Rolling out

This month, Australian Aviation revisits Jetstar to discover how its RNP/AR rollout has progressed in the last two years, and to examine whether promised efficiencies have been delivered.

RNP/AR

Performance Based Navigation (PBN), and RNP/AR represent a shift away from reliance on ground based navigational aids such as beacons and other short range radio navigation systems, allowing RNP capable aircraft greater precision in approaches and departures.

The International Civil Aviation Organization (ICAO) defines RNP as “a global set of area navigation standards, based on performance requirements for aircraft navigating on departure, arrival, approach or en route. These performance requirements are expressed as navigation specifications in terms of accuracy, integrity, continuity, availability and functionality required for a particular airspace or airport.”

This navigation performance accuracy is expressed as an RNP type. By way of example, if an aircraft is qualified to operate on an RNP 0.3 airway if it has demonstrated that the capability and performance of the aircraft’s navigation system will result, at least 95 per cent of its flight, in it being within 0.3nm of the indicated position on the navigation system (or runway centerline).

Jetstar, like its parent company Qantas, has opted to use RNP/AR procedures in order to increase schedule reliability, improve fuel economy, reduce aircraft noise footprints and reduce emissions.

The RNP/AR system adopted the airline was developed by Naverus, a company that pioneered NPR in the mid 1990s for use in difficult Alaskan airports.

In late 2009, Naverus was acquired by GE Aviation, which saw RNP technology as “fundamental to the transition from existing ground-based, voice-controlled air traffic management to time- and space-based digital systems. This transition represents the future of air traffic management.” As its website states, the company runs the full gamut of the RNP implementation process, from assisting regulatory agencies with the establishment of standards, aircraft manufacturers with equipment certification and operators with the implementation and maintenance of network-wide RNP programs.

The company claims its “tailored procedures extract maximum performance from modern aircraft through the use of shorter paths, tighter turn gradients, and optimum profile descents.” In devising an RNP procedures, the company must take into account contingencies such as missed approaches, instrument approaches and approaches with engines shut down.

For a bottom line conscious carrier such as Jetstar, these are powerful incentives to embrace digital era air navigation, unburdened as it is by a dependence on legacy navigational infrastructure like similar low cost carriers in the US and Europe.

Rnp Trial

Jetstar has been using RNP/AR since CASA permitted it to undertake a trial of the system in December 2007. Civil Aviation Order CAO 20.7.IB laid out strict conditions for the trial, stipulating that RNP-AR approaches or departures could only be conducted “(a) by an approved pilot flying in a manner consistent with his or her level of training for the approach or departure being undertaken; and (b) in a Jetstar Airbus A320-232 aircraft that is an RNP-AR capable aeroplane for that approach or departure as identified in the AFM (aircraft flight manual).”

Pilots in command of trial aircraft were required to have both Global Navigation Satellite System (GNSS) receivers operational, to have updating of the aircraft’s flight management system by VOR/DME inhibited and were to ensure that the RNP type for approach or departure was loaded from the (then) current approved navigation database.

CASA also had responsibility for overseeing Jetstar’s trial of RNP/AR in Queenstown, performing this on behalf of New Zealand’s CAA as per the Civil Aviation Legislation Amendment Act of 2006.

In order to make its A320 trial aircraft capable of RNP/AR Jetstar performed a small software modification that allowed the required navigation performance to be displayed to the crew on the aircraft’s primary flight display (PFD), and represented as a Lateral Deviation Scale. Monitored by the flight crew, this prevents the aircraft from departing (or deviating from) its pre-determined track and ensures it stays within its ‘tunnel’, towards the runway.

Gold Coast and Queenstown, New Zealand were chosen by Jetstar for its trials of RNP/AR in the first half of 2010.

Queenstown in particular posed the twin challenges of high terrain and changeable weather that, for Jetstar, resulted in a discomfortingly high number of diversions.

With previous, non precision RNAV approaches, minimum ceiling was 2700ft, which has been reduced dramatically using RNP.

Captain Nick Findlay is Jetstar’s Project Pilot for RNP/AR Implementation. “With RNP, we can have multiple curved legs that avoid high terrain and essentially, they line the aircraft up so when you break visual at 400ft at Queenstown, you’re presented with the runway immediately in front of you and in line with your runway direction. With VOR approach at Queenstown, you still have to circle and land on whatever nominated runway is active at the time, but the approach takes you to a navigation aid which wasn’t immediately at the airfield and you still have to navigate yourself visually to the runway centerline.”

It’s very similar to any normal approach, a lot of CRM is about respecting duties, communication flow, sop all built around ideally a successful approach.

Strict adherence to standard operating procedures is very important at Queenstown with its high terrain and challenging weather conditions.
He points out that demands placed on cockpit resource management (CRM) by an RNP approach are very similar to any normal approaches. As Capt Findlay notes, successful landings are the result of good communication flow on the flightdeck, flightcrew respecting each other’s duties and adherence to standard operating procedure.

And despite RNP approaches to Queenstown now standard, Capt Findlay points out that

“Strict adherence to SOPs is very important at Queenstown with its high terrain and challenging weather conditions.”

Jetstar is now ensuring all flight crew are proficient in RNP/AR procedures, and is very keen to see more airports around Australia gain CASA approval for RNP/AR procedures.

Capt Findlay outlined the RNP qualification process for pilots. “The basic RNP course is half day ground school and sim session for two pilots.

Captains are required to do one approach in VNC (VFR Navigation Chart) approach, which is the minimum for Australian operations.

“Queenstown requires all that, plus, another four hours in the sim in Queenstown itself, flying onto its simulated runway, going through normal and non normal procedures, engine failures on approach/departure, nav systems failures. We can also set the cloud base to the minimum, so that, by the end, the pilot is quite proficient at handling procedures.”

Once done in the simulator, pilots then undergo a classroom briefing of three hours, before undertaking three line training flights in and out of Queenstown, which is then followed by a proficiency assessment.

According to Jetstar’s CIO of Information Systems, Stephen Tame, training is one of the three components of RNP/AR.

“There is the aircraft component, which is the GPS positioning, there is the training and procedures component which has to be demonstrated to the regulator, and it’s got to be done within a known, mapped geography. And then the regulator has to certify you for various levels of RNP.”

Thanks to RNP/AR, Jetstar is no longer having to leave seats unsold on Queenstown bound flights, a precaution it would take to allow greater safety margins in the event of a diversion.

Current plans exist for all the airline’s A320s to be brought up to spec, with existing aircraft being retrofitted, and Jetstar’s newly acquired A320s being RNP/AR capable, as they leave the factory, as will the airline’s Boeing 787 when delivered next year. The airline has RNP procedures suitable for Brisbane, but increased concerns about noise levels caused by the convergence of several aircraft flying simultaneous RNP approaches into Sydney Airport have resulted in a delay in implementing RNP at Australia’s busiest airport. Nonetheless, Capt Nick Findlay is confident that an ever increasing number of airports will be able to be serviced by Jetstar’s RNP/AR capable fleet.

“Airports that don’t have an ILS approach are certainly high on our priority list because we want that coded, vertical path to the runway’s end.”