A worker checking the 18m high tail of Air NZ’s Boeing 777. Photo / Dean Purcell
Two years after the grounding of ZK-OKO, there are only a few weeks left before resuming its flight.
Much like four Boeing 777-300ERs that Air New Zealand parked in the California desert, the big jet idled
in Auckland is brought back to life to meet the torrent of travel demand.
While engineers working on planes in the Mojave Desert Graveyard face the threat of rattlesnakes and scorpions, those working in Auckland have encountered much friendlier wildlife. They found nesting birds atop the plane’s 18m high tail.
But all aircraft must go through a similar process of “preservation” and “depreservation” or “resuscitation” by following a detailed checklist set out in Chapter 10 of Boeing’s 777 Maintenance Manual.
The Auckland plane was one of three 777-300s kept in the city rather than flying to Victorville Cemetery, where Air New Zealand and other airlines have stored hundreds of planes during the pandemic in an environment with very low humidity.
The airline’s eight 777-200s were also parked in Auckland before being flown to Roswell, New Mexico. These planes are older and smaller than the 300 and will not be returning to the fleet.
Since its last flight from Los Angeles on August 24, 2020, ZK-OKO has been in long-term storage in Auckland. This will be the last of the three stored here to return to service.
The plane was a flying billboard for the Hobbit films in 2013 and carried up to 342 passengers to destinations such as London and Los Angeles for years until Covid-19 hit.
The main reason the three 777s were kept in Auckland rather than flown to California was because they underwent extensive undercarriage work, scheduled every 10 years in a hangar and requiring hundreds of hours of work.
Planes in Auckland were first put into active storage – an intense six-month maintenance schedule – but then, as it became clear the pandemic would impact air travel for longer than expected, it became a long term storage. Air New Zealand has made some changes to the manual to match that country’s unique weather and certain operational requirements.
After consultation with Boeing, instead of emptying the fuel tanks dry, 30 tons of fuel were left there. Even though the planes weigh nearly 160 tons empty, the extra weight of fuel has prevented them from flying away.
And unlike others in the desert, the plane ran its auxiliary power unit (APU) once every four days to run certain systems, including its air conditioning to keep its cabin at the required humidity level. – less than 70% – to avoid damage to the seats and other parts of the passenger compartment.
But outside Auckland, humidity caused corrosion in four GE90 engines in the planes and earlier this year the airline said it would need repairs overseas. They were sent to MTU Aero Engines in Munich for work and the last one is being installed on the left side of ZK-OKO this week.
When the pandemic hit, aircraft preservation work was rampant.
Working on Boeing’s preservation checklist for 777-300s takes about 400 to 500 man hours.
The windows were sealed with tape and the pitot tubes used to measure airflow were sealed (as they are for shorter periods when planes are on the ground). Static ports on the tail were also sealed, used to measure aircraft yaw. The wheels and motors were shrouded and a green anti-corrosion coating applied to the wing leading edge metal surfaces to protect them.
The APU was not only used for an air conditioning blast in Auckland, but also to make power available to the cockpit to restart systems. In the desert, planes slept more soundly with equipment such as circuit breakers removed from the cockpit.
Engineer Gary Bennett is an Air New Zealand production planner and team leader who carried out the work in Auckland and said that once in storage the planes were checked at regular intervals ranging from once a week to once a year.
Every 30 days the planes were moved to equalize the pressure on the tires and every 90 days the planes were brought into the hangar where the lubricants were refreshed and certain parts of the plane serviced.
Fine metal parts such as lightning rods required special attention due to the effects of the weather, but otherwise engineers found the planes in Auckland to be in very good condition.
In addition to major work on the undercarriage, there was a reconfiguration in the cabin. Although the number of seats remains the same, some will have more legroom, others will not. The emergency slides also underwent scheduled maintenance.
Panasonic’s technical staff have been working on in-flight entertainment systems that will be loaded with new content. The ground planes also provided an ideal environment for new cabin crew members or those who had undergone 777 refresher training.
In total, the planes in Auckland had around 4,000 to 5,000 man hours on them to resuscitate and do the scheduled heavy lifting and get the cabins ready. Those planes at Victorville will be resuscitated for flight as required by regulators and Boeing, but the additional work will be done in Auckland.
For ZK-OKO, August 19 is a key date. This is when the pilots will complete four to five hours of checks – performing a virtual flight on the ground.
Four days later, they will perform the short check flight required after both engines have been shut down and the plane has been inactive for so long.
Everything is going well, it will then resume service with passenger flights.