As thousands of planes lay dormant around the world, a senior aircraft technician explains a lot of work goes into taking planes out of action.
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The Covid-19 coronavirus has left the aviation industry in a state of flux, and more than half of Air New Zealand's fleet is being stored at airports around the country.
Shutting a plane down is not like storing a car however, and lifetime aircraft technician Eric Reynolds says it will get more complicated the longer the lockdown lasts.
Reynolds is the maintenance controller at Massey University's flying school and has worked in the aviation industry more than 40 years, including for the Royal New Zealand Air Force.
He said the process for short-term storage and maintenance, while time consuming, was relatively simple.
"Typically if you were only storing it from 14 to 28 days you wouldn't do anything to the aircraft particulalry," he said.
"You would just go out weekly to start the engine, bring it up to temperature, check its parameters and then park it up, shut it down and put blanks and things in like you'd normally do."
Blanks are engine covers that are routinely used on planes when they're not in motion.
For longer periods, there is a tipping point for aircraft that requires engines to be essentially frozen, Reynolds says, right on the four-week mark.
"If it's going to be more than 28 days then it becomes a little bit more extensive. They need to run up the engines, get them warm, then drain the operating oil out of them and put an inhibiting oil into them.
"That inhibiting oil is thicker and heavier and sticks to things better, therefore gravity doesn't drag it to the bottom of the engine over time."
Air New Zealand has grounded 58 planes due to Covid-19 so far.
The airline could not provide anyone to talk about how it looks after grounded planes, but in a statement it said it took 400 hours to put a single jet into storage and initially maintain it.
For turpoprop planes - which are smaller - the initial push is 100 hours.
After that, turboprops take about 20 hours of labour per aircraft, per week to maintain while in storage.
This includes towing the aircraft with a tractor so the wheels don't get flat spots, security and fluid checks, and idling engines to charge batteries.
Reynolds said birds and insects would sometimes build nests in the multi-million dollar machines.
"Or even some of the smaller orifices can get mason bees. I've only ever come across it once and they were building nests in the fuel vent, and that was causing issues with fuel flow."
Air New Zealand could not provide an estimate on how long it would take to bring its planes out of storage, but said it "varies between fleet and is dependent on the length of time each fleet has been grounded for".
Reynolds said it would take as long to get the planes out of storage as it had to put them in, if not longer.
He said that after 28 days of being in lockdown most of his flying school's 14 aircraft would have had their calendar safety inspections expire.
"If we were to go back to work and start flying again after four weeks, we would only have two servicable aeroplanes at eight o'clock on the first day."
He said some aircraft safety certificates were based on hours of flight, but could last between 12 months and 12 years.
Air New Zealand said none of its planes were being broken down for parts, but Reynolds said it would be reasonable to expect.
He spent 20 years in the Royal New Zealand Air Force and remembered when eight of the force's planes were broken up for parts in Woodburn, Blenheim.
He said an airline would first try to sell parts on demand, then parts would get stripped and stored in warehouses.
"They take them with these chainsaw-type metal cutters and cut them up and sell off the aluminium for resmeltering."
Air New Zealand has 23 Airbus A320 planes on the ground. Some of these have an average age of close to 16 years, according to its website. Their working life is 25 years.
"I think you'll only find the breaking down will happen to older aircraft in the fleet," Reynolds said.
In the meantime, airports remain waiting rooms for aircraft with have nowhere to go.
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- The Coronavirus Podcast