Plane malfunction illusion: Rolling shutter effect

Chris wanted to take a photo while on an airplane flight. The aircraft was a Bombardier Q400. Chris didn't have a camera with him, only his Apple iPhone 3GS. The scanning order of his iPhone sensor combined with the light refracted from the airplane window caused a distinctive "detaching blades" phenomenon in the photo. Rotating the camera warps the blades in different directions.

Edit: Unfortunately for me, Chris is no longer sharing his photos online, but I have found others. Keep reading!

Bombardier Q400 digression

Q400 passenger airplane by The Cranky Flier on Flickr

There have been some serious safety concerns with the Bombardier Dash Q400 Turboprop. Persistent problems with faulty landing gear received plenty of media coverage. Also, landing gear failure is highly noticeable to passengers! Some of the worry is depicted by The Cranky Flyer in the little drawing.

Although there have been no passenger injuries, thanks to pilot skill, multiple instances of left or right wheels failing to extend fully (or at all!) upon landing have occurred in Canada, the United States, and France. Those are the markets for Bombardier's small-to-medium sized commercial and business aircraft.

Engine stalls in very cold weather, due to ice, is another issue with the Q400. Both the U.S. Federal Aviation Administration (FAA) and Canadian air safety regulators launched formal inquiries.

Despite the appearance of Jason's photo below, there have never been any problems with Q400 propellers blades detaching and falling off while in flight!

Blades by Jason Mullins on Flickr

Jason observed the same effect as Chris. He took his photos with an iPhone 4 rather than an iPhone 3GS, but as he explains, that doesn't make a difference:

Wanted to try this - flying to Guernsey UK and back today. It's an iPhone 4, and the scanning typically goes from top left to bottom right, so moving objects lean to the left. Essentially any electronic shutter camera (i.e. not an SLR-like mechanical shutter) will give these effects. Wikipedia has some good articles on rolling shutters.

For those who want to try this out, just point your simple electronic shutter camera at an object moving parallel to you, preferably fast, and take the photo. The faster the relative speed between you, the more the distortion. Rotating objects go really weird!"

Wikimedia Commons Category: Rolling shutter has the best explanation I've found yet:

Rolling shutter is a method of image acquisition in which each frame is recorded, not from a snapshot of a single point in time, but rather by scanning across the frame either vertically or horizontally. In other words, not all parts of the image are recorded at exactly the same time, even though the whole frame is displayed at the same time during playback.

Wikimedia Commons is the repository for most of the photos and other image files used as illustrations for Wikipedia articles. I found this image on Commons.

de Havilland Canada Dash 8 propellor with rolling-shutter
artifact; Pixel 3 camera via Wikimedia

One of the most striking examples I found of rolling blades, or more accurately, rolling shutter, is from an airplane that was on the ground rather than in flight. Although stationary, the propellor was powered on and rotating.

Yak-TD Soviet 2-seater plane
with engine on but not in flight

The explanation given by the photographer confused me. I'll quote the most relevant parts, and link to the image source webpage which goes into more detail.

If you watch the prop through the camera, the blades spun down and came off the prop at the 6 o'clock position, then looked like they bounced off the ramp and reattached at 9 o'clock. Very weird. Aircraft was a Yak TD with a M-14 engine idling at 1000 RPM. Yes, we had someone in the seat and brakes were set... As for Photoshop, if I had those skills I would not be working on communist iron.

Observed on blimps too!

I noticed that the same 'detaching blades' aka rolling shutter effect can be captured on other aircraft types, as long as they have propellers not jet engines.

I've become fond of the official Despicable Me blimp, or rather, the DespicaBlimp. Yes, it is from that animated motion picture with the minions! The effect is visible in these two tweets with photos.

Home of the #steelers from the #despicablimp by AJ pic.twitter.com/cBW8vKFJD9

— #Despicablimp (@Despicablimp) September 26, 2013

It is more centered here.

#Florida from the #despicablimp by AJ pic.twitter.com/AcAywr9rxM

— #Despicablimp (@Despicablimp) April 18, 2013