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Comment by vilhelm_s | Hacker News Reader

This is often talked about in the case of Air Force One (which is supposed to be able to keep flying in case of a nuclear war, so that the president can survive and order the military). The limiting factor is probably engine oil, e.g. this article suggests 2-3 days. https://executiveflyers.com/how-long-can-air-force-one-stay-...

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The new VC-25B aren’t going to have aerial refueling capability as cost saving measure. They do have longer range.

> The new VC-25B aren’t going to have aerial refueling capability as cost saving measure.

Also: the old VC-25A did/does have it, but it was never used in ~30 years of flying.

Thanks for sharing. I never realized engine cycle times were so short on planes!

> It’s generally recommended that aircraft engine oil should be replaced every 50 hours, otherwise the oil would turn to sludge and get contaminated, which would damage the engine.

This sounds like piston engine advice. I’d be surprised if jet airliners are going in for oil changes twice a week.

Jet engines constantly pump oil under pressure between the stator and rotors to provide lubricant for the radial bearings while sealing and cleaning them. It’s a completely different kind of oil to the kind you’d find in a piston engine and operates at a much higher temperature.

Agreed but what’s the service interval on that oil? Does it get changed regularly or just topped off?

It’s a piston plane but my understanding of the DC-3 is that it runs out of fuel around the same time it runs out of oil.

Hybrid-electric propulsion systems can enhance flight endurance by separating propulsion and power generation tasks, individually optimizing each for specific stress levels aligned with mission requirements.

Does the marginal efficiency make up for the added weight? Aircraft engines already operate in a very narrow envelope so they can be optimized for cruise.

Hyllion Karno is a good example for power generation unit required ultra-low maintenance.

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