How do you transport a turbofan engine that consists of 40,000 parts, weighs as much as two adult bull elephants, is sensitive to shocks, and costs millions of dollars (without damaging it)?
The short answer is: With care and difficulty. The slightly less short answer is: Only with specialist equipment, expert freight carriers, and some innovative thinking.
Curious about the details? This article explains all.
What is a turbofan engine?
Turbofan engines (the modern variation of a basic gas turbine engines) are the most common type of turbojet engines on the market today. If you’ve ever flown on a Boeing 747 or 767 or an Airbus A330, it was thanks to these technological wonders.
Turbofans are popular because of their high thrust and good fuel efficiency. In amazingly simple terms, the core engine is surrounded by a fan in the front and an additional turbine at the rear. This combination creates enough thrust to move an airplane but in a very fuel efficient manner.
They’re extremely expensive to develop and buy, which is why they account for around 92% of total market value, despite representing only 46% of all units produced. It’s hard to say how much a turbofan engine costs because it’s included in the overall cost of a plane, but (depending on type and thrust) it’s roughly between 12 and 35 million dollars.
Regardless of the hefty price tag, the latest turbofan engines have helped stimulate the development and production of a bunch of advanced-design aircraft. These bring benefits such as increased maintainability and reliability, higher passenger capabilities, greater range, and enhanced safety features.
If turbofans are getting better, why are they getting bigger?
With each breakthrough in technology, the bigger these impressive engines become. That’s curious when you consider everything else that’s built around technology gets smaller over time (think computers, mobile phones, hard drives, portable speakers, video cameras, and TVs).
It all boils down to science. Bigger engines are simply more efficient, up to a point. If you’re into physics, it’s about drag and kinetic energy vs. momentum change (thrust). Basically, if you want to get something off the ground like the twinjet B777, which weighs in at 347,800 kg (766,800 lb), you’ll be needing thrust. And a lot of it.
This short, fun video by Minute Physics explains why turbojet engines are getting bigger:
Why transport a turbofan engine from one country to another?
It’s ironic that an engine that powers almost all of today's commercial jet airliners and most military transport aircraft has to be sent from country A to country B as a piece of cargo. But why ship it the first place?
There are three main reasons for shipping an aircraft engine as cargo:
- To transport it from a manufacturing plant to an aircraft Original Equipment Manufacturer (OEM)
Take as an example the Trent XWB, which is the turbofan jet engine made in Derby, England, by Rolls-Royce. As soon as an engine is ready for operation, it's transported to the OEM to be installed in the Airbus A350 XWB. The destination is usually Toulouse, France, where Airbus has its headquarters.
- To transport it from an OEM or operator to a Maintenance, Repair and Overhaul (MRO) facility
Some airlines use third-party MRO facilities, rather than doing maintenance inhouse, to reduce costs and remain competitive. MROs provide spare parts, preventive maintenance, and repair and overhaul. An operator will send an engine to an MRO for repair and overhaul to extend its life and put value back into it.
- To transport it from an MRO facility to an aircraft grounded due to engine trouble
When an aircraft is grounded because of a technical malfunction—known as an Aircraft On Ground (AOG)—the operator may prefer to replace the malfunctioning engine with the reserve engine rather than repair it on site. This gets the plane back in the sky as soon as possible. Not unreasonable when you consider an AOG can cost an airline up to US$150,000 an hour.
Why is it so difficult to transport turbofan engines?
As long as ridiculously large aircraft engines such as the Rolls-Royce Trent 1000, Trent 7000 or the General Electric GE 9X are used to power aircraft, they’re a cinch to move around. It’s when they’re flown as a piece of cargo that they become a major headache for all concerned. It’s no surprise. Turbofan engines are huge, incredibly heavy, and very fragile. A look at the stats tells you all you need to know:
- Weight: The dry weight of a T1000 is over 6,000 kg. Then you need to add another 6,000 kg for the engine stand that protects the engine and keeps it in place.
- Size and dimension: The Trent 7000 series has a length of 4.8m (188”) and the fan has a diameter of 2.8m (112”). Of course, they have a very irregular shape too, so you can’t fit them in a standard shipping container.
- Fragility: Aircraft engines may produce thousands of pounds of thrust and endure temperature extremes, but they are actually delicate machinery.
And if things do go wrong with the transportation? The repair price is staggering. If an engine is even suspected of being damaged, the owner has to stump up at least $150,000 for diagnostics and inspection, which of course excludes the price of any subsequent repairs.
What are the options for transporting a turbofan engine?
Rail transportation is generally unsuitable for shipping jet engines. Uneven track surfaces and the jarring impact of rail cars when they connect make the risk of damage too high. Sea freight is also disqualified as an option because it takes too long (remember, an aircraft that’s not flying costs the operator a ton of money). That leaves trucks and planes.
Specially designed trucks are a safe and cost effective way to transport aircraft engines over shorter distances. They can be dispatched quickly, and their full-air suspension system protects the sensitive calibrations of the turbofan engine. Over longer distances, however, aircraft are the superior option. Just as with road transportation, specialist equipment is required. In this case, a pallet that is strong enough to hold both the engine and its stand yet is thin enough to allow the engine to fit in the plane’s hold.
The answer to shipping jet engines by air: the PZE engine stand pallet
Any ordinary pallet would buckle easily under the weight of a turbofan engine. However, the PZE engine stand pallet solution that is produced by VRR is used exclusively to transport jet engines on the main deck of wide-bodied aircraft such as the B747 or the B777. This innovative pallet, which combines a specially designed pallet and engine stand, is:
- Thin enough to allow the engine to fit into the plane’s hold
The maximum height of the Cargo Loading System of a B747 is 118”. Since the turbofan’s dimension is 112”, there’s just 6” of wriggle room for the engine stand and pallet. At its thinnest, the PZE is just 3/8” thick.
- Lightweight enough to ensure total cargo weight does not exceed limits
There’s a limit to how much cargo an aircraft can carry. A B747 can hold up to 29,000 lb (13,154 kg) gross. Since a turbofan engine and its stand can weigh almost 12,000 kg, the pallet itself can’t be too heavy.
- Strong enough to bear a turbofan’s weight
Despite its insubstantial weight, the PZE can withstand loads up to 13 tonnes, which is 2 times the weight of a bull African bush elephant.
- Rigid enough to protect the engine’s components from any damage
It has a sandwich construction and reinforced edges to make the pallet stiff and as robust as possible.
Like the turbofan engine, the PZE engine stand pallet is truly an engineering feat. Just not priced for tens of millions of dollars.