Winglets were first identified in 1952 to achieve better fuel burn. But they were not adopted until much later. It took Airbus a long time to follow Boeing’s lead on deploying them, as you can see. There may be good reasons for this slow acceptance by OEMs, like cheap fuel, but it was not a smart move looking back. Embracing savings of any sort is a key focus at every airline today.
There is another technology about to be deployed (in under two years) that offers airlines the same sort of savings in financial terms and the “green” impacts are amazing. We are talking here about WheelTug. The device has been tested and proven to work. Despite one airline’s poor reaction to a successful test and an OEM’s reluctance to admit it – the solution works as advertised. Not only that, but the concept of electric driven wheels has been considered by Airbus and apparently a related development is taking place at SAFRAN/Honeywell. It is an idea whose time may have come.
What you see here is a system that essentially lives in the hubs of the nose gear. The gear shown is for the 737NG, and an A320 version is in the works. Inside each wheel is an electric motor powered by the airplane’s APU. What does this do? It does a lot. Having this device installed on a nose gear means an airplane does not need a tug for a start. (Yes it can easily be uninstalled) That in turn means all sorts of other benefits.
Here’s a list of issues that WheelTug suggests airlines might want to consider.
- Fuel burn – an airplane can drive itself off the ramp and down to the runway using the device. Since it is an electric drive the airplane’s APU is all that is needed. Main engine start can occur at the runway. This means saving 3g of fuel per minute by not having main engines running. Similarly, upon landing, the airplane drives up to the gate using WheelTug. Fuel burn at $3.50/g with a 19 minute taxi (out and back) means savings of ~$160 per cycle, with four takeoffs per day that means ~$630 per day or $4,400 per week. That’s for one plane – a fleet of 100 could save over $22m per year. Of course you can add lower wear and tear on the engines too.
- Airport Ops – No tug means a saving of ~$50 with each push back. Four times per day that adds up to ~$260,000 per year. And there are soft issues not easy to price – like what is it worth to have the first flight actually takeoff at 6:30am rather than only taxi to the runway at that time? A WheelTug plane needs no special ground handling, it trundles down the ramp on its own power and quietly gets in line. If you doubt this, consider your last 6:30am departure and what time the pushback actually happened. WheelTug planes don’t wait for tugs.
- Engine Ops – by not running main engines on the ground until you are at the runway means much less FOD impact. Research shows 85% of FOD damages happen on or near a ramp. Even in the case of “power by the hour”, airlines pay for the idling engines. The engine owner gets paid for flight hours. But a damaged engine costs the airline both times. And FOD is insidious – small dents in the fan blades decrease efficiency way out of proportion to the size of the ding. FOD is bad and costs money. While it is difficult to quantify the cost, engine repairs run into tens of thousands of dollars. WheelTug means no ramp FOD damage because the engines aren’t running when they on or near the ramp.
- Brakes – here’s a data point most people don’t know about. Carbon brakes are superb at stopping planes when they are landing. But the “tap-tap” on taxiways wears them out fast. With WheelTug there is no use for brakes until pilots want to stop. The motor drive can be slowed or accelerated.
In a visit with WheelTug we saw the detailed breakdown of the numbers. They are impressive and their list is longer. Their conservative estimates are savings of ~$610,000 per airplane per year. They use a 737NG in their assumptions. We cannot quantify the obvious benefits like much less airport noise. With so much less engine noise there is also less air pollution. WheelTug estimates a fuel burn reduction of 600,000lbs of fuel per year per plane. That also means 1.9m lbs less CO2 emissions. If you’re an eco-sympathizer you’ll love WheelTug.
Then consider the no running engine situation on the ramp – everything at the gate goes faster because there is no waiting for spool up or spool down. Airlines can use both front and back doors to speed turnaround. LCCs should love WheelTug.
So who loses? Tug drivers. But do a Google search on airport tug accident images. That should suffice. Ground handler accidents also go down because there is no more pin setting or pulling. Add lots of little things and you start to see significant savings.
So what’s the deal? WheelTug’s business model essentially boils down to this – they lease their system. Their charge is 50% of what they believe an airline will save. So an airline could get a free month use of the system before they actually get to pay for it. An airline gets to see the savings immediately. What other cash saving technology can be deployed by the airlines with a deal like that? Winglets certainly don’t, and once they are installed, the airline is committed.