April 6, 2020. Well it has been an interesting couple of months. It seems any of us can be infected and not know it, and we risk spreading whatever it is we may or may not know we have to others. Many have decided not to fly at all until this blows over. Us? We've equipped ourselves with masks and fly at least once a week. We do have N95 masks, but The Lovely Mrs. made one for me so that is what I wore on this particular flight . . .
But what if your operation decides you need to sit the airplane down for a few weeks? What should you do? Some of the older Gulfstreams have what is know as "LUMP," or the Low-Utilization Maintenance Program. We in the G500 don't have one of those, but we do have Chapter 10 of the Maintenance Manual, but nothing in there explicitly tells you what to do and it is filled with errors. The "Flight Ready Storage - Preservation" procedure (10-30-01), for example, says the airplane will be ready in 24 hours but has you preserve the engines and disconnect oxygen bottles. I am presenting the "Short Term Storage - Preservation" procedure as a good place to start.
Some Gulfstreams had you run the APU every five or seven days and if you couldn't do that, there were extra steps to take. In the G500, the "APU on Aircraft - Preservation" procedure (10-18-01) can be done up to 2 months after the last APU operation, so no worries there for short term storage.
You might look to our "older brother," the GVI, for guidance. Their maintenance manual requires the APU and engines be run every 7 days and that all electrical equipment be run for an hour. As with many things in the GVII, our requirements are much simpler.
Our manual says we can go two months without running the APU. The P&WC Engine Manual (PW800-72-00-00-00A-A) says the engine should be run at least once every 14 days.
I think if you are going to sit the airplane down for a week inside a secure hangar, the only thing you really need to do is disconnect the batteries in the aft equipment compartment and pull the eBatt circuit breakers. You might also consider purging the water system so it doesn't get stagnant. Beyond a week, you might consider going through the Short Term Storage - Preservation procedure, though I would be leery about disconnecting the oxygen bottles.
Everything here is from the references shown below, with a few comments in an alternate color.
When not operating the airplane for five or more sequential days, perform this procedure to prevent battery voltage from depleting to below an acceptable level via ‘trickle’ losses. These actions are especially important when operating from a facility without adequate electrical ground power support.
Wait two minutes after securing Main Batteries before pulling the following circuit breakers.
[GVII-G500 Maintenance Manual, §10-30-02]
Short term storage is defined as the condition of the aircraft not intended to be flown for a period up to 6 months. An aircraft in this condition is not necessarily considered to be flight ready. It is necessary to know where the aircraft will be parked, moored or hangared before this procedure starts. If the aircraft is to be kept on jacks, store it in a hangar. Make a checklist of tasks to be done to make the aircraft airworthy when put back into service.
It is recommended, but not necessary, that the aircraft follow the applicable storage and inspection interval requirements when maintenance inspections or the aircraft outfitting (completion) procedure is done.
Note that what follows comes directly from the maintenance manual but is offered only to provide you with a flavor of what is needed when sitting the airplane down for a while. If you plan on parking the airplane for an extended period, please consult the maintenance manual directly. You might want to skip a lot of these items if you are only talking about a few weeks, but notice that there are 5-day items related to the batteries, starting at step 25.
DO NOT SET THE PARKING BRAKES DURING STORAGE. THE BRAKES CAN BECOME LOCKED AND NOT RELEASE EASILY.
IF THE AIRCRAFT IS NOT MOORED AND DANGEROUS WEATHER IS NEAR (WINDS MORE THAN 30 KN), THE AIRCRAFT MUST BE MOVED TO A SAFE LOCATION.
When the main batteries are disconnected and the circuit breakers are pulled on the Forward Emergency Battery, the eMED will not operate. It will be necessary to connect the main batteries to operate the door.
[P&WC Engine Maintenance Manual, Engine Preservation, ¶7]
Between 15 and 90 days the inlet and exhaust covers must be installed and logged in the engine logbook. Beyond 90 days, there are specific preservation procedures in the manual.
The GVII doesn't have a procedure for what to do every seven days so what follows are my techniques. I've used the "Flight Ready Storage" procedure in the G650 Maintenance Manual (10-10-00) as a model, assuming we have less to do based on the clues given in our maintenance manual. We can assume, for example, we don't have to run the APU and engines every 5 days based on the fact our maintenance manual says we can go 2 months without operating the APU with no issues. I am reaching out to Pratt for something more definitive on the engines.
Gulfstream GVII-G500 Aircraft Maintenance Manual, Revision 4, June 28/19
Pratt & Whitney Canada Engine Maintenance Manual, PW800-A-72-00-00A-810A-1, Issue 50 -02/DEC/19, 33B1390, Engine Preservation
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