Printed headline: Cargo Conundrum
Many types of aircraft can be given a new lease on life when they are converted from passenger jet to freighter, but doing so presents considerable engineering challenges—and relies on a steady supply to the market of older models.
Converting a passenger aircraft to a freighter involves removing anything that is surplus to requirements, such as equipment and furnishings—including seats, galleys, toilets, stowage bins, side and ceiling liners, carpet flooring, oxygen panels, overhead consoles and entertainment systems. It also entails removing and deactivating passenger doors, replacing or reinforcing floor beams to meet cargo loads, installing the main deck cargo door (typically on the left side of the fuselage in front of the wing), installing the hydraulic and electric control and operation system for the cargo door and modifying the cargo compartment with new linings, ceilings, lighting systems, floors and drainage systems. The area behind the flight deck may be modified to accommodate extra crew, and a 1-min. smoke-detection system will also be installed, according to the American Friendship World Air Cargo Corp.
“The most complex section of any conversion is the cargo door and surrounding structure. This is usually where the conversion starts,” says Robert Convey, senior vice president of sales and marketing at Aeronautical Engineers Inc. (AEI), which converts the Boeing 737-300, 737-400, 737-800, MD-80 and Bombardier CRJ200. These aircraft are chosen because they have the same narrowbody cross section as past freighters. Cost is also an issue. “When these programs were launched, they represented the latest technology at the lowest price point,” he explains. Because of the aging nature of the aircraft, Convey says one of the principal challenges of the conversion is dealing with the structure of the older airframe and issues associated with the aircraft’s age, such as corrosion and cracking.
Making sure the aircraft is safe from fire is also critical. Freighters used strictly for cargo must be fitted with what is known as a “Class E” main deck structure for fire protection.
According to Boeing’s design specifications for cargo-carrying aircraft, a Class E cargo deck dictates the inclusion of a separate approved smoke- or fire-detector system to alert the pilot or flight engineer, and the means to shut off the ventilating airflow to or within the cargo compartment. The controls for these must be accessible to the flight crew in the crew compartment, who must also be able to exclude hazardous quantities of smoke, flames or noxious gases from the flight crew compartment. Crew emergency exits also must be accessible under any cargo-loading condition. If an emergency involving a fire does occur, pilots will don oxygen masks, depressurize the cabin and climb to altitude to starve the fire of oxygen, says Convey.
With so much engineering expertise in cargo conversions, some operations that convert aircraft rival the engineering teams boasted by Airbus and Boeing. “We have a specialized engineering team with more than 1,200 engineers. Together, they are more than capable of designing an aircraft from scratch,” says Rafi Matalon, vice president of marketing at Israel Aerospace Industries’ (IAI) Bedek Aviation Group. “This gives us capabilities similar to those of an OEM.” Aircraft that it converts to freighters include the 737-300 BDSF (Bedek Special Freighter) and BDQC (Bedek Quick Change), 737-400BDSF, 737-700BDSF, 767-200BDSF, 747-400BDSF and 767-300BDSF. A 737-800-based freighter is also under development.
Despite converting so many Boeing aircraft types, Bedek does not have access to the OEM’s engineering data. “This means we have to have a lot of expertise in reverse-engineering,” says Matalon. “We have to be able to take parts and components and work backwards to produce engineering data.”
He says one of the biggest challenges in preparing an aircraft to carry freight is reinforcing it sufficiently to cope with a payload that is much heavier than passengers. For example, a converted 737-700 might have a maximum payload of 43,000 lb.; for a 737-800, it might be 55,000 lb.
“We remove all the interior of the aircraft, such as the seats, carpets, galleys and lavatories, and then we start work to improve the structure to cope with the payload, which can involve reinforcing the floor beams,” says Matalon. Because removing interior components involves cutting a major part of the aircraft structure, it is important that this area is reinforced correctly. And when it comes to the all-important process of installing the cargo door and reinforcing the aircraft interior, IAI has proprietary systems that minimize turnaround time. Many complete sets of components are built on the ground and installed via a jig featuring specialist tools for accuracy.
The turnaround times for cargo conversions are short, Matalon says. “For a narrowbody aircraft, we are talking about 90 days,” he notes. For the 767, we are talking about four months; for the 747, it is five months.” Many standard maintenance checks will also be carried out while the aircraft is being converted. “We can save a lot of time and money by not having to ground the aircraft again after two or three years of service,” Matalon says. “We can include not only standard heavy maintenance checks, but upgrades of avionics and communications systems, for example.”
AEI operates on similar timescales and methodologies, explains Convey: “Most of our conversions take roughly 120 days. Additional aircraft maintenance items are often combined with the actual conversion process to take advantage of aircraft downtime.”
In the case of transporting special cargo such as pharmaceuticals or flowers, customized cooling containers may be used on the newly converted freighter. IAI will also make modifications to the aircraft’s air conditioning system to enable goods to be cooled in certain zones. “The main deck of the narrowbody freighter is pressurized and, due to reduced air flow, is colder than a passenger cabin, thus helping to keep goods fresh,” Convey notes.
Demand for freighters is increasing all the time, says Matalon. This is especially true in developing markets with huge potential for growth, such as India and China. But one constraint on the development of the sector is the availability of older aircraft to convert. This means that IAI is looking at beginning to convert Airbus aircraft in addition to its workhorses from Boeing. The Airbus A330 may prove to be a good alternative to Boeing 767 conversions, Matalon explains, while the A321 could be converted for cargo as an alternative to the 757.
“There is a lot of interest from China, India and Russia in the 767, but we are limited by feedstock,” Matalon says. “The Airbus A330, we think, is a good alternative. The 757 is being phased out slowly. There is a lack of feedstock there, too. We are thinking about these two platforms, the A321 and the Airbus A330. Still, the feedstock is expensive. We must bring the product to the market at the right time, which means when the feedstock is very reasonably priced.”
In 2017, IAI converted 18 767s, and its principal customer was Amazon—about three-quarters of Amazon’s 767s were converted by Bedek. For the midsize market, the 767 is likely to continue to play a key role, and there will also be a program to convert the 777 at IAI. The company features seven cargo conversion lines at IAI with another remote site and the possibility of adding another remote conversion line. This capability puts it on par with Boeing’s cargo conversion capacity.
“We are giving these aircraft a new lease on life of 15-20 years,” Matalon says. “We are doing a lot—but we could be doing even more.”