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Comment by kamarg | Hacker News Reader

> This seems incredibly inefficient. Is there a future for hybrid aircraft, which would feature both traditional turbofans and large batteries for energy storage?

I would assume the extra weight would make it not really worth the added cost and complexity.

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Honestly it sounds like the "right" way to do it would be electric ground vehicles pulling the planes into position, as with tugboats in water. Plane never need carry batteries into the sky and saves a literal ton of fuel.

IIRC towing to and from the runway has two major issues:

- standard towing tractors are really slow when towing, nowhere near taxiing speed, so you need a fleet of heavier duty "fast tow", possibly dedicated (depending on price)

- more traffic around the runway, which creates more airport complexity

Taxibot does exist tho, and is certified, and used in a few airports. Though I think it's only hybrid not electric.

Bigger issue is that the engines need to be idled for a while anyway to get up to proper temps, etc. you don’t want to start the engines and jam them into full takeoff thrust 5 seconds later.

The software in modern engines wouldn’t let you do that anyway. The engine startup process can be quite long - several minutes in a 737 MAX - while the engine’s ECU brings things to proper temperatures etc.

But with e-taxi, the startup cycle could be performed while taxiing, potentially saving airlines time on pushback as well as fuel/maintenance cost savings.

True, the engines need to be warmed up and the hydraulics need to be pressurised, but given e.g. airbus recommends single engine taxi without APU (SETWA) warming up the engines probably doesn't take that long in the grand scheme of things. Definitely not the 15~25mn of taxi. From the sources I can find, "normal" warmup takes 2~5mn depending how long ago the engine was shut down, unless outside temps are exceptionally low, and you can do that while reaching the end of your taxi.

> but given e.g. airbus recommends single engine taxi without APU

This is wrong, unless you have a source for it

Because jet engines are notoriously simple devices to begin with.

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