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The longest ever flight was 64 days in a Cessna 172 (2021)

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Re: The longest ever flight was 64 days in a Cessna 172 (2021)

#61

Post by _s »

stefan_ wrote: post #48
evandijk70 wrote: post #22

Earlier quoted context omitted.

In a car running at 100 kph, that would be 180000 km (roughly 110 miles). Most cars would need at least some parts replaced by that time as well..

Yet only 54000 km at the more typical average speed of 30 km/h. Are aircraft engines typically under high load at cruising speeds? It would seem they are generally overbuilt to overcome the high demands of takeoff.

They're generally outputting up to around 75% of their rated horsepower at cruise.

I'd say that's closer to going 110km/h or 65mph in 2nd or 3rd gear for most cars.

Re: The longest ever flight was 64 days in a Cessna 172 (2021)

#62

Post by NovemberWhiskey »

stefan_ wrote: post #48
evandijk70 wrote: post #22

Earlier quoted context omitted.

In a car running at 100 kph, that would be 180000 km (roughly 110 miles). Most cars would need at least some parts replaced by that time as well..

Yet only 54000 km at the more typical average speed of 30 km/h. Are aircraft engines typically under high load at cruising speeds? It would seem they are generally overbuilt to overcome the high demands of takeoff.

For example, a typical performance cruise power setting in a Cessna 172SP might be 70% rated power (180 BHP at sea level), which is way, way, way more than you'd ever use for a sustained period in your car.

Highway cruising might take 20-40 HP depending on your vehicle, which is probably more like 10% of rated power. 70% of rated power in a typical American car is probably like 120 MPH.

Re: The longest ever flight was 64 days in a Cessna 172 (2021)

#63

Post by rlpb »

akiselev wrote: post #54

This is by far the most interesting part of the story: > Refuelling was handled by lowering a hook via a winch down to a fuel truck that would trail the plane on a straight stretch of road, usually twice a day. The winch would then pull up a fuel hose from the truck, which would be used to fill the belly tank in around three minutes. The same system was used to regularly pull up food, oil and other supplies like towe…

The point of Air Force midair refueling is for when there isn't a convenient long, straight road that they can get a tanker to. Otherwise they would just land :-)

(also jet engines are really inefficient at low altitudes and it takes a lot of fuel to climb, so the other point is so that fighters don't expend the fuel getting back to altitude again)

Re: The longest ever flight was 64 days in a Cessna 172 (2021)

#64

Post by idlewords »

NovemberWhiskey wrote: post #62
stefan_ wrote: post #48

Earlier quoted context omitted.

Yet only 54000 km at the more typical average speed of 30 km/h. Are aircraft engines typically under high load at cruising speeds? It would seem they are generally overbuilt to overcome the high demands of takeoff.

For example, a typical performance cruise power setting in a Cessna 172SP might be 70% rated power (180 BHP at sea level), which is way, way, way more than you'd ever use for a sustained period in your car. Highway cruising might take 20-40 HP depending on your vehicle, which is probably more like 10% of rated power. 70% of rated power in a typical American car is probably like 120 MPH.

Also worth mentioning is that they didn't spend all their time on cruise, but had to dip down to refuel from a truck twice a day, putting more work on the engine.

Re: The longest ever flight was 64 days in a Cessna 172 (2021)

#68

Post by kqr »

flavius29663 wrote: post #33
mmastrac wrote: post #27

Earlier quoted context omitted.

That was wild: "While climbing through 8,000 ft above mean sea level, the UAV experienced a series of uncommanded turns. The UAV self-recovered from the first two uncommanded turns however, the third upset resulted in the aircraft entering an uncontrolled spiral descent. Despite attempts to return to controlled flight, the UAV sustained an in-flight break-up." I can only imagine the control systems that go into these…

> I can only imagine the control systems that go into these gliders. Fun fact, most planes are inherently stable, just like paper planes. If there is a disturbance, they will self correct most of the time. For example, glider pilots, if they do something stupid, are instructed to just let go of the controls, and the glider recovers on its own very quickly. Few ways this can go wrong: the wings start to "flap" by vibr…

As you said, stable is not necessarily good. A fully developed spin is incredibly stable to the point where you might not recover from it even if you try, but it also reliably takes you into the ground with too much vertical speed.

Re: The longest ever flight was 64 days in a Cessna 172 (2021)

#69

Post by kqr »

prottog wrote: post #6

That's amazing. I get in-air refueling, but the fact that the two pilots managed to live in this tiny space, performing tasks that I'm sure very quickly became repetitive and monotonous, listening to the engine, peeing in a bottle, etc. for two months is truly outrageous.

Not only that, but they had already tried a few times before, at least one 17 days long!

> After the first three flights, the plane had never stayed aloft longer than 17 days.

Imagine going up there a third time, spending a day, then two, then a week, then two weeks, and then a few days later being forced to land... only to get up there again aiming for two months!

Re: The longest ever flight was 64 days in a Cessna 172 (2021)

#70

Post by sokoloff »

stefan_ wrote: post #48
evandijk70 wrote: post #22

Earlier quoted context omitted.

In a car running at 100 kph, that would be 180000 km (roughly 110 miles). Most cars would need at least some parts replaced by that time as well..

Yet only 54000 km at the more typical average speed of 30 km/h. Are aircraft engines typically under high load at cruising speeds? It would seem they are generally overbuilt to overcome the high demands of takeoff.

To put the power-over-overhaul-run into a more comparable perspective, I think it's helpful to compare the gallons of fuel consumed [as a proxy for the amount of energy/work output]. A small aircraft engine like in a 172 might be 10 gallons per hour, or 18K gallons of flight time over an engine run.

18K gallons will take a typical road car around 500K miles, so an airplane engine getting "only 1800 hours" of flight time likely outperforms the typical auto engine.

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