A cold soak is the future owner's first opportunity to see if the aircraft flies as advertised and everything is working as expected and as spec'd. It's in this flight that any problems can be highlighted back to the OEM before the balance of the purchase price - and ownership -- is transferred.
Man with a Mission
I approach the cold soak as a mission. It's a mission that you want to accomplish, and you want it done successfully. It needs to managed the same way you would if you were taking the new owner up in the air for the very first time. It needs to be right.
I am hands-on with the cold soak, and that begins at the start of the morning briefing on the day of the cold soak. Present in that briefing are all the leads from all the trades -- installs, avionics, mechanics and inspections -- together with the OEM's pilots, your pilots (if they've made the journey for the cold soak flight,) and the Delivery Guy (that's me). The trades people give a brief history of what kinds of issues they saw during their flights, the status of those snags and what they've recently worked on regarding this particular aircraft.
When I say "hands-on", what I mean is I want to be the one to make the decisions on what gets powered on when. I will tell them when I want the power on, when to start the APU, when to put the cabin power on, and when to start the Cabin Management System (CMS). I also set the rules. If we power on and find we have to reset anything, we will not take it up in the air.
Doors are checked while we're on the ground to ensure they are sealing properly. They will be checked once again once we are in flight.
In the event that we are reset free, off we go, up into the sky, on a flight that will depart, and land, at the same place.
The Flight Itself
The cold soak flight lasts between 6 and 10 hours, depending upon the contract that has been signed with the OEM. There are usually 6 or 7 people on that cold soak flight: the owner's pilot, the OEM's pilot, an avionics lead, the CAM or CPM, a flight attendant, and me, the Delivery Guy ;-). Sometimes the OEM wants more people along on the cold soak flight but I try to limit the number of people who get to go so I have more room to make my inspections.
Because it's the first time I'm able to inspect a cabin with full daylight, I take advantage of this and usually the route we fly is North first, South second - but this depends on the time of day. As the sun illuminates the cabin, scratches, smears, nicks and misses are much easier to see than when the aircraft is in a stationery position under fluorescent lighting in a hangar. Esthetics are important, but so are the practical. Is there water? Does the hot water get hot? Is there enough hot water for an extended period of time? Is the plumbing working as expected? If the system capacity is four phone conversations taking place at the same time, you need to test to make sure you have all four conversations actually going on at the same time.
Time to Go Dark
I also conduct a cabin darkness test. We shut all the internal doors and shades and make sure lights from the closed-off sections of the aircraft don't filter through to inconvenience any future passengers where ever they may be sitting, or sleeping.
Putting an aircraft through a cold soak is more complicated today than it was just 10 years ago, because of the advancement of the CMS. Today, there are individual controls for nearly every seat and its immediate environment, like lights, shades, cabin temperature as well as entertainment. These all need to be put through their paces and tested.
The avionics lead is there to answer any questions about any of the systems - both from the pilots and from me, or the flight attendant. The avionics lead usually lends a hand to check plug-ins and switches to make sure they are working, as a 6-hour flight is sometimes very tight to get everything checked, especially on a larger aircraft.
The flight attendant will concentrate on the galley and make sure everything is working properly - not just whether coffee can be made but if there are appropriate cups to serve it in. Getting familiarized with the CMS is also critical: these days. Knowing something can be managed through the CMS means it can be easily found if you just know where to look.
Snags and Their Impact on Delivery
When we've completed the cold soak flight, the OEM is presented with the list of snags found during the flight. The quantity and severity of the snags vary: the largest number of snags I've ever recorded on a cold soak was 350. High-numbered snag lists are common when the aircraft hasn't been followed throughout the build. With a large list of snags, many of them will not be easy fixes, like differences in the color of the wood, problems with stitching on the seats, mismatching of fabric, leather - and even the carpet. The more snags found are a direct correlation on when the aircraft will be delivered. In many circumstances, the OEM will try to push the correction of some snags to a future date, post-delivery, which may take place at a service center in a different location. This isn't always the best solution and sometimes the purchaser must decide between getting the aircraft sooner with the faults that have been found, or getting it later, with everything fixed.
Imagine what it is like for the owner, who may be putting down $50 million dollars or more for an aircraft. Whenever anyone has something new, there's always the tendency to show it off - to your friends and/or colleagues. They certainly don't want to show them an aircraft with a mismatched interior, with discolouration, scratches and dents. It's much better to have everything fixed before delivery.
When an aircraft has been followed throughout the build, that list may be in the 100's, but those snags are mostly quick fixes, like paint missing from screws, scratches that will be removed with some elbow grease, etc.
A cold soak is the key ingredient for the happiness of the future owner. When all problems are found and resolved before possession takes place, it's a win-win for everyone involved: the OEM, the new owner, and me.