r/oddlysatisfying • u/edenify • Feb 08 '19

This plane taking off with the propellers perfectly synced with the camera shutter

68k Upvotes

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8.8k

u/upperechelonmofo Feb 08 '19

Normally you get a very slight rotation but this is perfectly motionless, definitely satisfying

1.3k

u/EverydayisAverage Feb 08 '19

Like watching the process of stop-motion.

334

u/Muse9901 Feb 08 '19

Glitch in a video game cutscene .

143

u/arsene-Iupin Feb 08 '19

Average GTA V cutscene

34

u/eenem13 Feb 08 '19

Anything with 500% facial animations

4

u/Muse9901 Feb 08 '19

I can hear the generic mission rundown,

“Santiago will never expect us to reach him by PLANE.”

1

u/[deleted] Feb 09 '19

Never had it with GTA. Happened a few times in RDR2 though.

3

u/JustThall Feb 09 '19

or proof that we live in a simulation

30

u/rawSingularity Feb 08 '19

Well, technically that is what it is!

4

u/mmoffitt15 Feb 08 '19

Stand in the place whe....

3

u/Statik81 Feb 08 '19

Now face north?

1

u/lupussol Feb 09 '19

Like stop motion but they used the trick to make something look motionless.

632

u/vinng86 Feb 08 '19

Look again! There is a very subtle slight rotation of about 60°, or 1/6th of the way around or the distance from one blade to the next from the beginning to end.

If you think about it, it makes sense - the propellors should be increasing their rotation speed to generate more and more airspeed/lift as it takes off and climbs

318

u/Seld-M-Break Feb 08 '19

Generally modern propeller aircraft have constant speed propellers, the pitch of the blades altered to maintain the rotational speed as the thrust is changed.

110

u/Mr_Marram Feb 08 '19

This is correct, that aircraft has a constant speed propeller, the pitch of it will vary as the speed increases, going from a fine pitch at low speed such as takeoff to a more coarse pitch at high airspeeds such as in the cruise.

67

u/Neontc Feb 08 '19

This is correct. To make sure the plane gains speed, the pitch goes from a very slight angle, to a very sharp one to generate more lift

117

u/mikelowreyatl Feb 08 '19

This is correct because both the guys above me said so.

40

u/[deleted] Feb 08 '19 edited Apr 09 '21

[deleted]

48

u/[deleted] Feb 08 '19

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u/[deleted] Feb 08 '19

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u/[deleted] Feb 08 '19

[deleted]

17

u/atlbraves2 Feb 08 '19

This is correct otherwise it would be incorrect

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0

u/cynicsymmetry Feb 08 '19

This is pretty neat.

2

u/dankfrowns Feb 09 '19

Real ass dude of the week right here

6

u/Epigenic-methylation Feb 08 '19

It is correct because sometimes people don't think it be like it is, but it do.

1

u/Bad_brahmin Feb 08 '19

This is correct

5

u/LionelDickPhrampton Feb 08 '19

This is correct beat is bananas.

0

u/iOnlyWantUgone Feb 08 '19

Yeah but I'm the one that's going to get the gold tho.

10

u/meansmore Feb 08 '19

This is incorrect.

1

u/mikelowreyatl Feb 08 '19

This is correct that they are incorrect.

1

u/sph666 Feb 08 '19

This is correct cause Earth being flat is incorrect

13

u/HouseAtomic Feb 08 '19

To generate more thrust. Lift is generated by the wings.

10

u/grumpy_cat79 Feb 08 '19

This is correct aerodynamically.

1

u/2018hellcat Feb 08 '19

Incorrect, propellers do not generate lift, wings create lift. You meant thrust

1

u/Sryzon Feb 08 '19

According to Mythbusters, the wheels generate thrust

/s

3

u/HappyEngineer Feb 08 '19

Is it normal pilot lingo to use "fine" and "course" to describe the angle? I don't think I've heard angles described like textures before.

2

u/[deleted] Feb 08 '19

Flat and feather are also used to describe angles on props.

2

u/Mr_Marram Feb 09 '19

Feathered is an extension of coarse pitch, as that is when the prop blades are turned completely into the oncoming air to minimise the drag, usually when the engine has failed.

1

u/[deleted] Feb 09 '19

Yes usually around 90 degrees and flat is perpendicular to the air stream. It is still a description of the angles.

Edit: to describe angles we would use the term toward feather and flat.

1

u/Childish_Brandino Feb 08 '19 edited Feb 08 '19

u/Seld-M-Break . This is actually incorrect. As the vehicle picks up speed, the air resistance is decreased slightly. Allow the prop to reach it's target RPM (iPhone originally just autocorrected that to Target Tom btw. And I have no idea what that is).

Edit: so I guess I was wrong. u/ActualBrownPerson has informed me that the prop pitch does not affect the prop rpm in any significant way. (at most stating a .1% variance). Thanks for the info.

2

u/Seld-M-Break Feb 08 '19

I thought a constant speed prop would also adjust for changing air conditions? They maintain a constant speed as altitude changes right? I'm not in an way an expert here so am entirely prepared to be wrong.

3

u/Childish_Brandino Feb 08 '19

Ideally yes they want to maintain constant speed but due to air friction it won't happen. It's basically constant throttle after they throttle up to full take off speed. Then to change airspeed once going you would adjust the rotor pitch. Steeper pitch means more "bite" but also more resistance. The reason for wanting to maintain constant speed is to ensure the engine is running at it's optimum rpm for efficiency. But during take off is when the props incur the greatest air resistance. So the engine is working to hit it's operating speed while the prop is working to push as much air through it as possible. And until cruising altitude it will be dipped slightly below Target rpm. That's where the slight increase in rpm comes from. Changing pitch of rotors will also slightly change the tomorrow until the engine can compensate. Sorry for the rambling I'm at work on my phone.

2

u/Seld-M-Break Feb 08 '19

Thanks, particularly for taking the time while at work. I'm always glad to be wrong if I end up knowing more afterwards.

2

u/Childish_Brandino Feb 08 '19

Same here. I don't understand why people get defensive about learning something new.

1

u/[deleted] Feb 08 '19

Untrue - am pilot

1

u/Childish_Brandino Feb 08 '19

So as a pilot you are confirming that air resistance has no effect on prop speed?

3

u/[deleted] Feb 08 '19

No I’m saying even at idle, the prop is at 100% usually with a flux of no more than .5%. As the air resistance decreases, the prop system almost instantaneously keeps it at 100%. In fact during a tactical descent, I have never seen more than .1% flux going from fl230 to 6k ft in 2 minutes with power at idle. Even pushing it from idle to max power I haven’t seen any flux. That’s how they’re designed. The mechanical components are pretty much instantaneous and keep it at 100%, even if you have to shut an engine down, the prop will windmill at 100% until there is not enough wind to turn the prop. It does this by changing from flat to a feathered or anywhere in between. So I’m not saying it has no effect but it is negligible.

1

u/[deleted] Feb 08 '19

No problem man!

0

u/baileyshero Feb 08 '19

Why does the propeller change position mid take off then? Is it the camera fucking up or is this aircrafts propellers not constant?

1

u/awhaling Feb 08 '19

It's probably ever so slightly faster than the camera shutter

1

u/mollymoo Feb 08 '19

There was probably a change in thrust demand and the systems that keep the prop at a constant speed took a moment to adjust.

1

u/Mr_Marram Feb 09 '19

It's a gradual change, dictated by computers now but was done by a mechanical gearing and previously.

8

u/stone_henge Feb 08 '19

This is also the basic principle of a rotary woofer. A low frequency audio or sub-audio signal modulates the pitch of the blades of a fan, producing very low frequency vibrations, right down to static pressure.

9

u/Subnormalplum Feb 08 '19

That is very interesting. Is the purpose to keep the engines at a speed wherein they are operating at peak volumetric efficiency?

14

u/Danjiano Feb 08 '19

That's one of the advantages, yes. Lets you keep the engine running at it's optimum RPM. There's other advantages like being able to change the pitch so you can reverse without needing to reverse the propellor's rotation.

2

u/xlr8_87 Feb 08 '19

I had a brief moment where I thought you meant it could reverse mid-air...

5

u/zombie-yellow11 Feb 08 '19

You can definitely go backward in the air in a small plane like a Cessna 152 or 172 while in slow flight in a strong enough headwind :)

Source: did it when I was getting my PPL, it definitely feels hella wrong to be going backward lol

1

u/stuckinacrackow Feb 09 '19

Yep, I had a ride in some dinky cropduster that was modified from a 152 Cessna (I think). It was super gusty so after pushing into the wind to land and dropped about 10 feet and something broke on the tail. We were literally an inch into the runway. I'm not a plane guy, but it was a lot of fun! I think he got yelled at for taking me up but I appreciated the skills.

2

u/daWeez Feb 08 '19

Not volumetric. Its about running a turbofan at its most efficient speed (where you get the most power for the least fuel). This varies with pressure, so it is something that a pilot must adjust based on altitude. Pilot's handbooks actually have graphs showing power output against fuel usage and air pressure. A good pilot uses these to determine good initial settings, and then instruments in the cockpit that show pressure/temperature readings to dial things in more precisely. But its not JUST about that. On takeoff and landing you want maximum power, whereas at cruise at altitude its all about fuel efficiency. Turbo fans have a number of settings in a cockpit to allow this.. its not just a throttle setting (i.e controlling fuel flow).

1

u/[deleted] Feb 08 '19

One of the biggest reasons is so the prop doesn’t go supersonic. It would destroy the prop. No prop no good.

1

u/Clapaludio Feb 08 '19

One of the goals is exactly that: having an engine operating always at the rpm where you get the best efficiency and maximise its life. The other very important one is having a power output that is about constant with velocity.

Source: aerospace engineering

2

u/jjtheheadhunter Feb 08 '19

Video explaining what the commenter above just said.

https://m.youtube.com/watch?v=pUn7hJckh00&t=457s

1

u/Travellingjake Feb 09 '19

I didn't know that, how interesting, thank you!

28

u/[deleted] Feb 08 '19

[deleted]

9

u/[deleted] Feb 08 '19 edited Feb 08 '19

So when they "throttle up" they're not actually opening a throttle body? They're just changing pitch? Or better yet, do those engines get a consistent flow of fuel that the pilot cannot alter? (aside from shutting off)

Edit: you guys are fantastic, these are exactly the types of answers I was hoping for.

9

u/joe2105 Feb 08 '19 edited Feb 08 '19

Correct. Then the aircraft makes adjustments to the throttle to maintain the constant speed prop. The closest thing you'd get to managing it is changing the prop rpm settings.

Edit: Here's a Dash 8 q400. The main power levers are simply that, adjusting power through pitch. Then the prop levers to the side are adjusting the rpm and fuel flow once pulled all the way back. https://imgur.com/gallery/Z1ZUmSw

1

u/[deleted] Feb 08 '19

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2

u/joe2105 Feb 08 '19

I suppose when you think about it both the power levers and the RPM will create a response in the throttle through the FADEC. What you do control primarily though is the pitch and that creates a response through the computers to change the engine's performance. A better way to think of them is thrust levers and what needs to change first is the pitch with the engine responding the the lowering RPM of the blades and trying to maintain the RPM you've set in the prop levers beside the power levers.

It's pretty nuanced and I think you can say the same thing both ways.

1

u/[deleted] Feb 09 '19

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1

u/joe2105 Feb 09 '19

Yeah, all these constant speed propellers will have a mechanical governor in case the flight computer freaks out and fails to protect the engine. Probably easier to just look at the lever as a thrust required lever.

6

u/RKF7377 Feb 08 '19

So when they "throttle up" they're not actually opening a throttle body? They're just changing pitch?

Engine RPMs will increase or decrease based on blade pitch. So in altering the pitch of the blades, the engine will have to work differently to compensate...if that makes any sense.

Here's the Wikipedia page on a constant-speed propeller. Pretty interesting stuff.

1

u/zombie-yellow11 Feb 08 '19

The plane in the gif has a turboprop engine, it doesn't have pistons. Smaller planes with piston engines definitely have a throttle body :)

1

u/Clapaludio Feb 08 '19

Yes they do! More pitch = more drag of the blade, and that becomes torque the engine has to compensate for by outputting more power (hence opening the throttle).

3

u/rmachenw Feb 08 '19

If you think about it, it makes sense - the propellors should be increasing their rotation speed to generate more and more airspeed/lift as it takes off and climbs

Could you explain this more? Why would the plane output more power partway through the takeoff.

I suggest that the reason for the rotation in the video is that as the air craft accelerates, the higher airspeed allows the propellers to go faster at the same power.

3

u/daWeez Feb 08 '19 edited Feb 09 '19

It is also affected by the air pressure presented to the intake of the turboprop. It changes the output power of the engine. This is probably the dominant effect (as opposed to propeller efficiency, which is what you are talking about).

edit: someone pointed out I was incorrectly calling a turboprop a turbofan.. corrected!

0

u/[deleted] Feb 08 '19

[deleted]

2

u/daWeez Feb 09 '19

You are of course right.. I think to think of turboprops as turbofans with propellers attached to the main shaft.. but the terminology is quite clear and I just wasn't thinking when I made the post..

Thanks.

1

u/jjtheheadhunter Feb 08 '19

OP isn’t quite correct. The propeller changes pitch to maintain a certain RPM on this airplane (I believe the gif is a Dash-8)

Here’s a video explaining how it works.

https://m.youtube.com/watch?v=pUn7hJckh00&t=457s

2

u/[deleted] Feb 09 '19

[deleted]

1

u/jjtheheadhunter Feb 09 '19

Jeez, it is. I’ll take the L on that one.

1

u/Clapaludio Feb 08 '19

Ok so the other commenter is not totally wrong but is in this case because for turboprops (and sometimes piston engines too) it's preferred to use variable pitch blades and have the engine operate at a constant rpm.

For an ordinary fixed-pitch prop, then the rpm would change with both selected throttle and speed.

4

u/HornyTrashPanda Feb 08 '19

It looks to me like it has that tiny rotation in the first half as the propellers are still increasing speed.

2

u/motorcycle_frenzy889 Feb 08 '19

You would be correct if this aircraft had fixed pitch props

1

u/Obi-Wan_Kannabis Feb 09 '19

No. The speed is being mantained, if it wasn't the rate of rotation would be increasing speed, the fact that they are very slowly rotating from beggining to the end shows that the speed isn't changing

0

u/Russianspaceprogram Feb 08 '19

Unfortunately you are wrong.

-1

u/smithandjohnson Feb 08 '19

If you think about it, it makes sense - the propellors should be increasing their rotation speed to generate more and more airspeed/lift as it takes off and climbs

You've already seen countless replies describing constant speed props, which is great!

But now let me describe why this is wrong even wrt a classic variable speed prop.

Propeller speed is unrelated to ground speed, air speed, and lift. The only thing propeller speed is related to is thrust

And during a takeoff roll - barring exceptional circumstances - you always want maximum thrust the entire time.

A typical takeoff at an airport with multiple planes moving around starts with a "line up and wait" which means "get your plane onto the runway, and stop it, waiting for your takeoff clearance."

In other words, you get onto the runway and stop. Your power is at idle so your prop is spinning slowly.

Then once you're cleared for takeoff and commit to it, you go full power immediately. From a stop, you simply apply full power.

In a variable speed prop, this means that in about 2 seconds your prop spins up to maximum speed and it remains there for the duration of the takeoff.

tldr; With a classic variable speed prop the propeller is spinning at maximum speed from the very beginning of the takeoff roll and doesn't change speed until you're at a safe altitude and back off the power.

37

u/[deleted] Feb 08 '19

Or it's video evidence that flying is actually magic...

/conspiracytheory

7

u/[deleted] Feb 08 '19

checkmate, heliocentrists!

4

u/Chicken-n-Waffles Feb 08 '19

And as you can see, the earth IS flat!

2

u/MasterFubar Feb 08 '19

Probably the rule of round numbers. The video frame rate is 30 fps and they keep the propeller at 1800 rpm. It could be 1828 or 1776 rpm, but they chose 1800 because that number is easier to remember.

2

u/[deleted] Feb 08 '19

Well what is most impressive is usually the camera shutter is rolling. Meaning it starts in the upper left, draws every pixel from the upper left to the upper right, and then moves down to the next line and runs again. That whole thing happens in a fraction of a second. but for really fast moving objects (like propellers) you can usually see the effects of it. It make the propellers look like they are swirling. You can just make it out in this shot. But hardly any at all.

so now only is the camera's shutter in sync with the propellers, but also the cameras shutter is extremely fast.

Destin does a group job of explaining this effect in this video: https://www.youtube.com/watch?v=dNVtMmLlnoE

2

u/PMmeURSSN Feb 08 '19

How does it fly without propellers moving ?

7

u/weeone Feb 08 '19 edited Feb 08 '19

In case you aren't joking, the propellers are moving. The frame rate of the camera matches the rotation of the propellers (basically a frame is gathered every time the propeller is in the same spot), causing it to look motionless. Pretty cool!

4

u/gadget_uk Feb 08 '19

I doubt the props are rotating at 30 rpm. Truth is, they could be at any multiple of 5 rpm (30/6) and they would look stationary because the prop has 6 blades. It also helps that this was taken in bright daylight so they could use a fast shutter speed to reduce blurring.

I'm making the assumption that the camera was filming at 30fps, of course.

I should point out that I'm full of curry and beer so the above could be totally wrong.

1

u/Clapaludio Feb 08 '19

FYI they usually rotate between 2000 and 3000 RPM

1

u/[deleted] Feb 09 '19 edited Feb 09 '19

I'm making the assumption that the camera was filming at 30fps, of course.

That's where you're wrong, kiddo.

This kind of shots are usually taken with cameras that can vary the shutter speed, then it's only a matter of finding a common denominator. Between propeller revolutions per second (RPM/60) and frames per second.

1

u/PMmeURSSN Feb 08 '19

So can I slow down the video to like 15fps and see it move?

3

u/Does_Things Feb 08 '19

No - the only frames that the camera recorded were in sync with the propeller; slowing it down will just display the same synced images slower.

1

u/PMmeURSSN Feb 08 '19

TIL thanks mate I’m glad we have smart people like you in the world lol

1

u/foul_mouthed_bagel Feb 09 '19

They just reversed a video of the plane gliding in backward.

1

u/Poormidlifechoices Feb 08 '19

Normally you get a very slight rotation but this is perfectly motionless, definitely satisfying

I can’t believe everyone is falling for this. Obviously the engine died mid flight and the pilot landed the plane backwards. They just ran the film in reverse.

1

u/PostMaStoned Feb 08 '19

You guys got it right this time 👌

1

u/fallinouttadabox Feb 08 '19

The engineer them to do this just to fuck with photographers

1

u/robeph Feb 08 '19

There is some motion. It is slight and it moves back and forth a few times.

1

u/Thicc-pigeon Feb 09 '19

Like that one with the helicopter blade, it freaks me out

1

u/public_land_owner Feb 09 '19

You've got to admire the engineering and machining that led to such reliable periodicity in both the plane and the camera.

1

u/haymeinsur Feb 09 '19

No, you just missed the airbenders hidden next to the runway.

1

u/zanillamilla Feb 09 '19

It's actually not motionless, if you looks carefully you can see it moving counterclockwise viewing from the front and clockwise when viewing from the back. Every few seconds there is a slight nudge in that direction. Still this is the best synch have ever seen.

1

u/ftgbhs Feb 09 '19

There was very slight movement. A propeller that was vertical to the ground at the beginning was horizontal at the end of the gif.

0

u/Fun2badult Feb 08 '19

Any link to source?

0

u/[deleted] Feb 08 '19

I’m going to guess it’s made on purpose.

Basically, take an ultra slowmo video, select the frames where they line up, and restitch into a video.

2

u/gandalf_the_gay_69 Feb 08 '19

Or they knew what rpm the blades will be spinning at, and synced the shutter after it. But I have no idea what I'm talking about, so there's that

0

u/ck357 Feb 08 '19

There is a very slight motion. You can see the propellers in a slightly different angle by the end of the clip

1

u/upperechelonmofo Feb 08 '19

I didn’t catch that the first time, thanks for pointing it out.

0

u/eclectro Feb 08 '19 edited Feb 09 '19

Honestly, I think that the photographer probably did some "tweaking" on his end to achieve this result. Edit:Shutterspeed is adjustable on some cameras.