C-5 gear swing test

Nifty video showing a C-5 undergoing a gear cycle test - those motors probably have more power than some Cessna’s I’ve flown…


Those are hydraulic pumps :joy:

They still have a power rating… :slight_smile:

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It’s more the term motor that is weirdly used in this context.

I dunno. Many of the planes I’ve flown have a hydraulically operated gear that are driven by an electric motor. Unless the C-5 has actuators that are operated by bleed air, then there is very likely a motor that is providing the power to the hydraulic system…unless it is just hydraulics that are part of the engines themselves. Then you really do have a motor powering them. :smiley:


But my understanding (weak understanding) of hydraulics is that you only need a small motor to provide a lot of power via hydraulics - is that correct?

The term motor is not really correct, you use a pump to build pressure in your pressure lines, then you can control the flow through these lines and regulate the pressure in your cylinders by using valve’s. These valve have all sorts of funny ways top operate.

My point is, saying it’s driven by a motor is like saying the aircraft banks because the engines are running. Whilst in reality the aircraft turns on the hydraulic power supplied by the systems that get their pressure from the accessory gearbox hydraulic pumps.

Ah…well, I’m just going off what I learned early in my career with 172s and stuff…they use an electric power pack (motor) that drives a hydraulic pump. The hydraulic pressure does the word, the pump supplies the pressure, and the motor runs the pump.

You’re confusing power with force. It’s sort of similar to levers. The diameter ratio between the pump and the working cylinder will determine the ratio of throw and force. Long story short, if you use a small pump cylinder diameter compared to the working cylinder you get more force but less throw, and vice versa.

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LOL detail derail!

Regardless of the terminology, the number of Joules per second (watts, horsepower, etc.) required to move that mass around is impressive. I’d imagine that gear assembly at least approaches the mass (weight, heaviness, heft, oomphtydoo, etc.) of a light general aircraft, so the power involved is going to be impressive compared to the 75 kJ/s, (75kW, 100 horsepower, etc.) engine in a Cessna 150 trainer (one-fiddy, one filthy, cess pit, tin gnat, etc.).

Yeah…I knew the energy wasn’t “free” by any means…but yeah, you put into words what I was thinking…a small motor working at high RPM can move a big thing slowly.

Winona knows the answer…

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I’m just thinking of putting something that big on jacks… I know their not going very high but, dang it’s still impressive!

They probably use hydraulics powered by electric motors…


The jacks are really impressive! Feels a little scary though the first few times.