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Airbus 320 pilot here. This is something I've wondered myself for a long time. This same idea of a electric motor on the wheels powered by the APU(auxiliar smal

by omegant 13y ago

Airbus 320 pilot here. This is something I've wondered myself for a long time. This same idea of a electric motor on the wheels powered by the APU(auxiliar small turbine for electricity and air presure, is the loud noise you hear when boarding the plane), is what some other pilots and myself have talked about for a long time. Just taking in to account that it makes you autonomous when pushing back and taxing, the long times you spend waiting for take of at the runway, it makes a lot of sense for this kind of planes that spend a lot of the daily time taxing on congested airports. I don't know exactly the reason why it hasn't been done before, I don't think is a weight or technology reason. It surely has seated on a TODO list for a long time, just take into account that in aviation we are way behind in aplication of the latest technology. For example we are still using single chanel radio for comunications with control( this is terribly frustrating and ineficient, it's pretty common to have comunication jams due to excess of traffics on the same frequency). Airplane computers even in new models are still 90s models (very slow but i suppose that stability is worth the boredom). There are a lot of other vintage technologies in aviation, after all every single release to production must be tested and approved by the FAA and EASA. It's the same for all major changes in systems and procedures. That makes all changes and improvements very slow and expensive.

crazytony 13y ago
Yep. The air transport industry is very very change (read: risk) averse. The current APUs (except for 787) have traditionally supplied power at 28 VDC and 115 VAC due to the worries about high voltage arcs. They would rather have more current over more copper than higher voltage. I suspect they have added significant wiring and electronics to this A320 to get this to work. I haven't been able to find out if this aircraft has even flown with this rigging much less gone through certification. I bet they could slightly improve this system and get rid of reversers as well (active braking). That being said, I'd imagine ATC to be very wary of the current 130hp system: there is no way you could expedite a move across an active runway at almost 80,000kg MTOW.
- o1iver 13y ago
  The video at the bottom of the OP shows that plane taking off and landing.
- omegant 13y ago
  I imagine that the APU generator must be reinforced or redesigned to be able to withstand the charge of the motors. Revereser are quite efective and I don't think you can get rid of them, because when you have slippery runways the braking through the wheels is going to be compromised. It's also another sys to fail on toP of the normal braking system (that already has quite a bit of it's own problem), so it's better to have paralel systems for the same function. If you are going the active braking route you'll need a place to send that electricity and the actual batteries are not big enough for that. You are right that the motor are not very powerful, 20kts max is a bit on the slow side as top speed. Given that in a big airport when you taxi at less than 15 kts you are slowing the rest of traffic (and they get nervous indeed when they are following a turttle!). Also to really be autonomous with this sys I imagine they'll install cameras to see the rear and the engines's nacelle (to be able to see that the engine is starting without issues, witha normal pushback you have ground crew observing). That's another level of systems that need new procedures and testing, not very complex initially but things can become really weird very fast in aviation and all unusual user cases must be taken into account. Edit:phrasing correction
- squidi 13y ago
  I think it's an oversimplification to say the reason for this innovation not happening sooner is because of risk. The Boeing 777 flies on only 2 engines which sounds far riskier but didn't stop it being approved. Also there's a race for building planes from carbon materials. Robert Witwer, vice-president of advanced technology at Honey-well of Morristown, cited some other reasons [1]: - Increased congestion: "Short hauls do a lot of taxiing time, especially in a place like Newark, where you can be 20th in line" - Legislation: “And there are a number of airports in Europe that have tough emission standards that would make the Green Taxiing System appealing. I believe it’s a game-changing technology." - Fuel costs: "The prospect of annual savings of $200,000 per jet from lower fuel use and less ground time has sparked interest from Airbus and airlines such as EasyJet and Alitalia. Airlines face the highest sustained prices ever for jet fuel. United Continental, the world’s biggest carrier, says it burns $25,000 of fuel per minute. Jet fuel delivery in New York averaged $3.12 per gallon in 2012, more than four times as much as a decade ago." - Technological advances: "What’s new in today’s technology is the convergence of airlines’ search for more efficiency and recent advances in miniaturizing electric motors to propel a plane at the 32 kilometres per hour it may need for taxiing." [1] http://www.wingsmagazine.com/index.php?option=com_content&task=view&id=8036&Itemid=146 http://www.wingsmagazine.com/index.php?option=com_content&ta...

by omegant 13y ago

crazytony 13y ago

Yep. The air transport industry is very very change (read: risk) averse. The current APUs (except for 787) have traditionally supplied power at 28 VDC and 115 VAC due to the worries about high voltage arcs. They would rather have more current over more copper than higher voltage. I suspect they have added significant wiring and electronics to this A320 to get this to work. I haven't been able to find out if this aircraft has even flown with this rigging much less gone through certification. I bet they could slightly improve this system and get rid of reversers as well (active braking). That being said, I'd imagine ATC to be very wary of the current 130hp system: there is no way you could expedite a move across an active runway at almost 80,000kg MTOW.

o1iver 13y ago
The video at the bottom of the OP shows that plane taking off and landing.
omegant 13y ago
I imagine that the APU generator must be reinforced or redesigned to be able to withstand the charge of the motors. Revereser are quite efective and I don't think you can get rid of them, because when you have slippery runways the braking through the wheels is going to be compromised. It's also another sys to fail on toP of the normal braking system (that already has quite a bit of it's own problem), so it's better to have paralel systems for the same function. If you are going the active braking route you'll need a place to send that electricity and the actual batteries are not big enough for that. You are right that the motor are not very powerful, 20kts max is a bit on the slow side as top speed. Given that in a big airport when you taxi at less than 15 kts you are slowing the rest of traffic (and they get nervous indeed when they are following a turttle!). Also to really be autonomous with this sys I imagine they'll install cameras to see the rear and the engines's nacelle (to be able to see that the engine is starting without issues, witha normal pushback you have ground crew observing). That's another level of systems that need new procedures and testing, not very complex initially but things can become really weird very fast in aviation and all unusual user cases must be taken into account. Edit:phrasing correction
squidi 13y ago
I think it's an oversimplification to say the reason for this innovation not happening sooner is because of risk. The Boeing 777 flies on only 2 engines which sounds far riskier but didn't stop it being approved. Also there's a race for building planes from carbon materials. Robert Witwer, vice-president of advanced technology at Honey-well of Morristown, cited some other reasons [1]: - Increased congestion: "Short hauls do a lot of taxiing time, especially in a place like Newark, where you can be 20th in line" - Legislation: “And there are a number of airports in Europe that have tough emission standards that would make the Green Taxiing System appealing. I believe it’s a game-changing technology." - Fuel costs: "The prospect of annual savings of $200,000 per jet from lower fuel use and less ground time has sparked interest from Airbus and airlines such as EasyJet and Alitalia. Airlines face the highest sustained prices ever for jet fuel. United Continental, the world’s biggest carrier, says it burns $25,000 of fuel per minute. Jet fuel delivery in New York averaged $3.12 per gallon in 2012, more than four times as much as a decade ago." - Technological advances: "What’s new in today’s technology is the convergence of airlines’ search for more efficiency and recent advances in miniaturizing electric motors to propel a plane at the 32 kilometres per hour it may need for taxiing." [1] http://www.wingsmagazine.com/index.php?option=com_content&task=view&id=8036&Itemid=146 http://www.wingsmagazine.com/index.php?option=com_content&ta...