While you don’t necessarily hear much about it, converting passenger aircraft into freighters is big business. Boeing expects demand for 2,600 new or converted freighters over the next 20 years valued at over USD$300 billion.
About two-thirds of that number will be aircraft conversions. These conversions are a core business at Boeing, who commands around 90% of the freighter market.
This article is about the conversion process. Note that every aircraft and every aircraft type is unique so this is a generalist article rather than specific to certain aircraft types. I’ve tried to keep it straightforward but any conversion is complex and can take several months.
There are some basic steps that are reasonably universal amongst aircraft conversions.
Prepare to convert
When a passenger aircraft comes into the factory to be converted into a freighter, the cabin is partially stripped out and the previous owner’s livery removed.
The aircraft may be jacked up into a neutral stress point for any modification of the airframe. This takes about four weeks.
Windows get plugged
Next, the passenger windows get plugged. Not only are passenger windows pointless on a freighter, but getting rid of them saves on maintenance and increases safety.
Full strip out of the cabin
Galleys, seats, overhead lockers, in-flight bars – none of these items are needed on a freighter so they get stripped out
The aircraft gets a new door
Usually, a new door large enough for cargo is installed at the front-end of the fuselage. This is slightly tricker than unbolting seats and is done in stages.
To begin with, a new upper frame shell section is fitted and riveted to the fuselage. Then the lower frame shell section is removed. A new lower frame shell is lowered into the prepared cut-out position, replacing the old lower frame shell, and is secured to the airframe.
The frames forward and aft of the cut-out are replaced by new, reinforced frames.
Then the door and its structural components are installed.
A new, high strength cabin floor is installed
When this is done, attention turns back to the cabin, now a bare space. The cabin floor is replaced by a higher strength floor complete with cargo pre-requisites such as ball mats and roller tracks. Floorspace needs to be maximized in order to carry as much cargo as possible. The cabin floor also needs to be strong enough to bear the load.
A final check and good to go
Finally, everything needs to be checked. There is a schedule of tests that need to be performed. The plane is inspected, test flights are carried out and documentation is prepared.
A handy way to extend the working life of aircraft
As Jay Singh noted in Simple Flying last year, converting passenger aircraft into freighters is a useful way for airlines to extend the working life of their aircraft and extract further revenue.
While complex, it is cheaper to convert existing aircraft than to buy new ones. As airlines have new aircraft come into their fleet, they often select their oldest aircraft for conversion.
For this reason, we still see some classics like the Boeing 727 at airports and can expect to see the Boeing 747 around for years to come – just carrying pallets rather than passengers.