Here is the result of a previous run. Probably this one came to the same fate? Turbulence or atmospheric conditions leading to mid air disintegration. When ZULU82 was lost, it was operating at a lower than usual altitude.
"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 gliders.
> 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 vibrating to a resonant frequency, in which case they need to change something, and also spiraling down towards the earth: not because the plane would not recover eventually, but because it might experience high forces that destroy them before recovery can happen.
Few planes are inherently un-stable: meaning they cannot keep flying without constant input, only examples I know of are fly-by-wire modern fighter jets (4th generation onward) and planes with weird shapes like the B2 bomber.
I don't think there is too much control put into these gliders for second to second operations, they are probably just letting it fly forward, with the control being: point it in a very general direction and don't lose contact with it.
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.
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 stable ballistic arc the plane wants to travel on.
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.
For what it's worth I found your whole comment easy to understand because it was well constructed and very logical, so much so that I didn't even notice the typo because your intent was so clear that I subconsciously auto-corrected it.
Fighter jets and the B2 are by no means inherently stable, in fact they're inherently extremely unstable relative or to earlier designs. It's just that the fly by wire systems make them fly stable.
It was two typos in a row. Mysteriously missing "un"s, "il"s, "im"s, "in"s, "ir"s, "non"s and "not"s change the intended meaning to its opposite unintentionally. Happens to me all the time. Touchscreen kb?
I 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".
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 towels and water for shaving and bathing.
Midair refueling is the realm of air forces and these guys did it with a hook on a winch.
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 spill valve to prevent a disconnection from spilling fuel, the forerunner to the modern aerial refueling system.
The trickiest thing to me about what the Keys did was oil changes, which they needed to do every three days. They rigged up a metal catwalk around their engine, so that Fred could walk out and change the oil from the outside while the plane was still flying (they had two oil systems, each of which could lubricate the entire plane, so every three days they turned off the oil system on one side, Fred climbed out, drained the oil out on the ground- it's the 1930's, no one needs environmental impact statements!) closed the valve and refilled the oil tank, then they turned on that side and turned off the other side and did it again a few hours later when that oil had cooled.
Both Fred and Al joined the USAAF during World War Two and flew bomber missions over Germany. Al stayed in the Air Force after the war and ended up as a Colonel.
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.
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)
And that's largely why this mission came to an end at this particular duration - the engine had degraded too much from the continuous use, it was barely delivering enough power to stay airborne.
That’s surprising! Do you mean the entire life of the engine, or just one run? If the former, doesn’t that get expensive? I imagine that’s not very sustainable.
Entire life of the engine. After 1800 hours total operation, the engine should be overhauled: taken apart, cleaned, each part examined and replaced if necessary. Note that per FAA regulations in the USA, only actual flight time counts toward this limit, not time spent taxiing on the ground.
It'll take a normal private pilot a few years to reach 1800h of operation, so it's more economical if you're not flying the plane continuously for weeks at a time.
But yeah, it's expensive. Owning a plane is expensive. It depends on if it's worth it to you to operate the plane. Small single-engine planes like the Cessna 172 are commonly used for recreation or training. So if you use it often, such frequent overhauls will pay for themselves in terms of safety and reliability.
Maybe when all-electric recreational aircraft become common they won't have to be maintained quite so much...
Electric airplanes are already used in training in Europe. They are less expensive to operate on an hourly basis just because of fuel/energy cost. But they are probably also cheaper to overhaul; the Emrax motors in Pipistrels are relatively simple, and it would probably cost less to buy two and swap one out (sending the other one back to Emrax for a new bearings) than to do one thermal engine overhaul. And almost no downtime!
(I work on another electric airplane which will take flight in 2023.)
I've flown an electric plane. Granted it was only about 60 cm long from nose to tail (and I flew it from the ground) but I can speak to its simplicity, low cost, and ready availability of replacement parts compared to ICE-based planes of similar size. :)
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.
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.
I think they are under more of a load a cruising speed than you'd expect. At speed both the car and plane are primarily overcoming wind resistance, which is more about speed and elevation than anything. If I'm understanding right the plane would be going more than highway speed within a few thousand feet of the ground for most of it's (flying) life so it's probably putting more stress on the engine than a car on the highway would.
More importantly: if your car engine dies you gradually slow down and pull over. If your plane engine dies calmly pulling over isn't an option. It's much easier to justify spending the money ensuring a plane's engine is reliable.
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.
Overhauling an aircraft engine is a very serious undertaking involving removing the engine from the plane, shipping it away for complete disassembly and replacement of many parts.
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.
> When asked by a reporter if he would ever replicate the stunt, Cook replied: “Next time I feel in the mood to fly endurance, I’m going to lock myself in a garbage can with the vacuum cleaner running, and have Bob serve me T-bone steaks chopped up in a thermos bottle. That is, until my psychiatrist opens for business in the morning.”
The part that made me chuckle outlaid was about hygiene...
> The danger of in-flight bathing
> In his diary, John Cook wrote, “We got a quart of bath water, a large towel and soap every other day.”
> On January 12, 1959, after refueling chores, Timm removed his clothes and stepped out onto the platform for a refreshing sponge bath. He started by brushing his teeth. Just then Cook realized that the airplane wasn’t going to clear an upcoming ridge if the platform wasn’t pulled in. Cook yelled at Timm to pull in the platform and later told of seeing his partner struggling to complete that task—buck naked, and weighing 240 pounds, with a toothbrush sticking out of one side of his mouth and toothpaste streaming out of the other. They cleared the ridge but learned to delay hygienic activities until they were over flatter terrain.
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!
The aircraft is hanging from the ceiling at the Las Vegas airport along with displays of artifacts from the flight. One of those things people just walk past and don’t pay attention to, but worth a look if you’re there!
> Before he passed away in 1978, Timm reminisced about his flying days and told his sons that he longed to locate 72B. His father’s wish eventually prompted Timm’s second son, Steve, to launch a focused effort to find and return N9172B to Las Vegas. He found it on a farm in Carrot River, Saskatchewan, Canada. He brought it back to Las Vegas in 1988. In 1992 the McCarran Aviation Heritage Museum (now the Howard W. Cannon Aviation Museum) obtained 72B for a permanent exhibit. It’s been restored to its pre-flight condition.
> Today, N9172B is back in Las Vegas. The 1958 Cessna 172 that holds the world endurance flight record hangs from the ceiling of the baggage claim area at McCarran International Airport. Next time you fly in to Las Vegas, take a minute to look up at one of the most prosaic record-setting airplanes in the world. And imagine what it must have been like to spend more than two months living in a Cessna 172.
I was expecting to read that this was only the longest manned flight, but it seems that the record for unmanned/unrefueled flight via a solar-powered plane is a bit less. That flight took place earlier this year and the drone vanished over the Arizona desert just hours before the record: https://simpleflying.com/airbus-zephyr-flight-ends/ . Clearly the government of Nevada contracted the aliens at Area 51 to ensure the integrity of their airport's tourist attraction.
For me, it's crazy they were able to stay that long time with the engine noise. Also, there's no that much space to stretch and doing some exercise. As the article says, most likely there aren't more people who want to try to beat it.
> When asked by a reporter if he would ever replicate the stunt, Cook replied: “Next time I feel in the mood to fly endurance, I’m going to lock myself in a garbage can with the vacuum cleaner running, and have Bob serve me T-bone steaks chopped up in a thermos bottle. That is, until my psychiatrist opens for business in the morning.”
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.
B52 seems a little overpriced. I'd think you'd want something like a C-47/DC-3 - enough room to walk around in, shower, cook, etc, but hopefully not too crazy expensive to operate.
Oil changes for a Stratofortress in flight would be a real trick. You could do what the Keys Brothers did and build a catwalk for wingwalking out to the engines- not recommended!- or you could do more like what the Hacienda did and run oil lines from each engine into the crew compartment so you can change it from inside, but that's a LOT of extra oil to pump. Going from the #1 engine all the way to the fuselage would be a long way to pump.
> One might think the B-52H Stratofortress, sixty years old and counting, would be the most expensive bomber to fly, but the GAO states it only costs $88,354 an hour.
You remove the back seats and replace them with auxiliary fuel tanks. Typically this is done by couriers delivering aircraft for sale - the seats are then shipped separately as freight.
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"!
A friend of mine did this for a living in his early 30's, he said those flights are probably the most dangerous things he's done in his life. He'd fly commercial to Canada, scout around for a good plane, arrange the sale and the various bits and pieces of paperwork, strip it down as much as possible, install extra fuel tanks and some other gear, then go to Halifax, check the plane over once more and then start puddle jumping hop by hop until reaching continental Europe. You could not pay me enough to try a stunt like that, let alone several times.
If he was flying Halifax-Newfoundland-Greenland-Europe the planes must not have been too small, because the Newfoundland to the next hop distance is quite large. The absolute shortest single leg distances involve going through Iqaluit and then Greenland.
Interesting, I don't know what planes he was ferrying, and we lost contact years ago (I moved to Canada myself, he moved somewhere else in NL) so I can't ask. Possibly he did what you suggested, it would make good sense. Quite possibly Halifax was mentioned as the last stop before the end of civilization in terms of repairs and spare part availability, but I'm very sure he came through there.
It is an interesting thing though, the same planes that go fairly cheap in Canada are worth a fortune here in Europe so there definitely is money to be made.
The 152 is the second version of the 150. It's based on the same design and is they're both rated for +4.4/-1.76g. The biggest difference between them is the Lycoming O-235 engine replacing the Continental O-200.
Both airplanes came in a number of variants. The Aerobat variant of each was rated to +6/-3g due to structural improvements. It had other aerobatic features like a quick release door, four point harness and skylights. You might be able to identify them by their checkerboard paint job. Less than 4% of 150/152s were Aerobats.
"Aerobat" is a brand name specific to Cessna. You can do some amount of aerobatics in any trainer, like steep turns or a lazy eight. The FAA defines "acrobatic", which specifically excludes those maneuvers and a few more. There's an associated Aerobatic Category of aircraft.
And I thought a four-hour flight I once took in a 172 was far too long!
Good little airplanes, they are.
I suppose they chose their engine airspeed to achieve the lowest fuel consumption rate https://www.se.edu/aviation/wp-content/uploads/sites/4/2020/... See pdf page 132, book page 5-18. It looks like they could use as little as ~6 gallons/hour at 1900 rpm. You can save a lot of fuel by flying more slowly; handy to know if you need (heaven forbid) to stretch that 45-minute reserve when your destination is socked in.
Reminds me of a video I recently watched of a crew of 4 women rowing across the Atlantic in a tiny little boat, taking continual 4 hour shifts for 3,000 miles:
I remember reading about this flight when I was a kid - it's truly impressive that they were able to overcome the challenges they faced and complete the flight successfully. The fact that their record still stands today is a testament to their determination and hard work. Great stuff!
I wonder whilst seem silly anyone fly 64 days of Microsoft flight simulator of a Cessna 172. (You may say it is easy, just trim … you do not know how unstable the thing it is and especially if you use real weather and not sure any affect of air traffic … or real people air traffic).
Just 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
Honorable mention goes to the Swedes with the Saab Viggen who managed to get missile lock on the SR-71 as it cruised through a narrow corridor past their airspace. The Viggen wasn't fast enough on its own, but much like modern cannonball runs, careful planning and coordination made it possible.
It’s 82 feet long but only 166 pounds, and solar refuels it’s batteries. Hardly the same class, but interesting nonetheless.
https://www.overtdefense.com/2022/08/20/airbus-zephyr-crashe...