FYI: that's 85% of the design life of the Continental O-300 engine in that aircraft (1,800 hours time-before-overhaul).
is there such a thing as in-flight re-engine-eering?
The longest ever flight was 64 days in a Cessna 172 (2021)
91–100 of 104 posts
Re: The longest ever flight was 64 days in a Cessna 172 (2021)
#92Earlier 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…
Almost all gliders are fairly strongly spiral unstable. Because of the long wings the outer wing in a turn is moving significantly faster than the inner wing. As a result the outer wing generates more life than the inner and the bank will increase until the glider is in a spiral dive. It is normal during a steep bank in a glider to have to apply a significant roll input to prevent the bank from increasing. So not only will a glider not spontaneously recover from a spiral dive, it will put itself into one by itself.
That is why recovery from a spiral dive is something that a glider pilot usually has to do as part of a demonstration of proficiency. I get to do one every year as part of my seasonal check flights.
These high altitude, long duration UAVs have really long wings. So the control system would have to work to overcome the tendency to overbank. At some point the tendency to overbank might overcome the authority of the controls.
Re: The longest ever flight was 64 days in a Cessna 172 (2021)
#93I asked my dad what they did on a long (8+ hours) bombing mission in WW2 when nature calls (a subject never covered by documentaries). He said "we used empty ammo boxes". I asked what they then did with the ammo boxes. He said "extra bombs".
My great uncle threw chaff out of a bomber during WWII and constantly got airsick, so he threw that out too.
Re: The longest ever flight was 64 days in a Cessna 172 (2021)
#94This 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…
Two decades earlier, a previous record holder, the Curtis Robin Ole Miss, stayed in the air for 27 days using real aerial refueling: https://airandspace.si.edu/collection-objects/curtiss-robin-... Fred and Al Key, brothers who owned an airfield together, flew the record plane, two other men (James Keeton and William Ward) flew the refueling plane. In order to make the refueling safe, the Keys had designed a breakaway…
I've actually thought about this and if I had Elon Musk money I'd use it to try and break this record instead of doing whatever he's doing now. Mostly so I could make a comment about how weird it feels to walk on the ground after living in a airplane for so long. It would be far more luxurious than this.
Re: The longest ever flight was 64 days in a Cessna 172 (2021)
#95Earlier quoted context omitted.
Interesting, thanks for the context. TIL!
Piston engines like you get in a Cessna 172 are also about the worst-case for overhaul times, since there's so much mechanical complexity and because they're often run at/near maximum rated power for long periods. Turboprop engines (effectively these are jet engines with propellers attached) like the ubiquitous P&W PT6A have TBOs up to 4,500 or even 6,000 hours.
Interesting, I thought everything in Cessna 172 is simple and reasonably forgiving.
Re: The longest ever flight was 64 days in a Cessna 172 (2021)
#96Earlier quoted context omitted.
Piston engines like you get in a Cessna 172 are also about the worst-case for overhaul times, since there's so much mechanical complexity and because they're often run at/near maximum rated power for long periods. Turboprop engines (effectively these are jet engines with propellers attached) like the ubiquitous P&W PT6A have TBOs up to 4,500 or even 6,000 hours.
Interesting, I thought everything in Cessna 172 is simple and reasonably forgiving.
It is. It only gets more complex and expensive from there.
Re: The longest ever flight was 64 days in a Cessna 172 (2021)
#97Earlier quoted context omitted.
https://www.planeandpilotmag.com/news/the-latest/2022/08/30/...
That's absolutely incredible. Thank you for sharing this! He was able to get 2500 miles of range by going from ~50 gallons to ~200 gallons. Talk about "hacker mentality"!
That's only around 12.5mpg, which is surprisingly low fuel efficiency.
Re: The longest ever flight was 64 days in a Cessna 172 (2021)
#98Earlier quoted context omitted.
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.
For conventional layout aircraft, with a suitably sized tail, stable mostly means nose-heavy. Which implies constant negative lift on the tail, and corresponding excess positive lift on the wings. Which means additional induced drag. All of which adds up to an efficiency and performance penalty. And if the tail controls aren't suitably sized, then the pilots won't have enough control authority to move of of the very…
I guess what I was trying to say is that a conventional aircraft has multiple stable lift-generating modes. Aside from going forward at the front side of the power curve there's also the spin. Both of these are implied by the design. One is desirable and the other is not.
Re: The longest ever flight was 64 days in a Cessna 172 (2021)
#99Earlier quoted context omitted.
It really likely is one of those "never will be beaten" records because anyone sane would do it in a B-52 bomber and have some room to stretch out - but everyone would immediately know it wasn't quite as "real" as being stuck in a plane the size of a Volkswagen bug for 2 months.
According to [1] Fédération Aéronautique Internationale stopped recognizing piloted endurance records altogether in 2015 due to safety concerns. So I'd say this record is very unlikely to be beaten! [1] https://www.damninteresting.com/the-unceasing-cessna-haciend...
Indeed! No more crazy records to avoid accidents
Re: The longest ever flight was 64 days in a Cessna 172 (2021)
#100Just wondering if that would be possible to achieve by using a battery-powered electric plane with solar charge support and some charging tech normally used for rapid charging electric cars... but maybe battery weight will be too high