Well, part of the reason you start them at the gate is also to test them and warm them up before you get to the most critical part of the flight where you absolutely need to be sure they're going to run: takeoff and initial climb. You don't want to be doing that procedure on the runway for operational reasons.
And some airplanes are already capable of pushing back under their own power. The reason we don't do that is not the plane -- it's the airport. The blast can damage the airport, ground equipment, and endanger people.
In context, a jet engine uses a significant percentage of cruise fuel consumption just idling on the ground. Many airports aircraft can taxi for well over 30 minutes just to reach the runway.
Some record setting flights have been conducted where the aircraft was brimmed on the runway and the manufacturers set minimum times for stabilising the engines before takeoff, circa 30s if I remember correctly.
Issues of blast damage go away if it's propelled by electric power. My understanding is one of the main reasons it isn't often used is that there is a real danger of tipping the aircraft over backwards if the wheel brakes are applied while reversing.
If you want to hybridise an aircraft then starting with electrifying the time spent on the ground is the low hanging fruit.
There's no ingestion risk if it's propelled by electric power, but there's still FOD risk. As I understand, gates in the US have to be specifically designated for powerbacks because of this risk. No matter the method of creating the thrust, if you can move a plane with it, you can blow some object into a person or the airport windows.
It certainly could be done but it would require changes to airports to accommodate it.
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Well, part of the reason you start them at the gate is also to test them and warm them up before you get to the most critical part of the flight where you absolutely need to be sure they're going to run: takeoff and initial climb. You don't want to be doing that procedure on the runway for operational reasons.
And some airplanes are already capable of pushing back under their own power. The reason we don't do that is not the plane -- it's the airport. The blast can damage the airport, ground equipment, and endanger people.
In context, a jet engine uses a significant percentage of cruise fuel consumption just idling on the ground. Many airports aircraft can taxi for well over 30 minutes just to reach the runway.
Some record setting flights have been conducted where the aircraft was brimmed on the runway and the manufacturers set minimum times for stabilising the engines before takeoff, circa 30s if I remember correctly.
Issues of blast damage go away if it's propelled by electric power. My understanding is one of the main reasons it isn't often used is that there is a real danger of tipping the aircraft over backwards if the wheel brakes are applied while reversing.
If you want to hybridise an aircraft then starting with electrifying the time spent on the ground is the low hanging fruit.
There's no ingestion risk if it's propelled by electric power, but there's still FOD risk. As I understand, gates in the US have to be specifically designated for powerbacks because of this risk. No matter the method of creating the thrust, if you can move a plane with it, you can blow some object into a person or the airport windows.
It certainly could be done but it would require changes to airports to accommodate it.
Sorry, it might not have been obvious, I meant by mechanically driving a wheel rather than projecting any kind of thrust.
Oh that makes sense. I was thinking in terms of the prop-driven flight discussed above.