Contrast stretching and speeding up reveals how Ingenuity kicks up dust on lift off and particularly on the return trip where she descends through her own dust cloud and disturbs it during landing.

[O]n the fourth flight, we actually scouted for a landing zone over 100 meters (328 feet) away. The digital elevation maps put together by the Ingenuity team gave us confidence that our new airfield is flat as a pancake – a good thing when you have to land on it.
***
Our helicopter is even more robust than we had hoped. The power system that we fretted over for years is providing more than enough energy to keep our heaters going at night and to fly during the day. The off-the-shelf components for our guidance and navigation systems are also doing great, as is our rotor system. You name it, and it’s doing just fine or better.

Helicopters do not scale up well.

Beyond the obvious thrust challenge in the thin Martian atmosphere (i.e. classic momentum theory, and the Mach/Reynolds aerodynamic issues common to all aeronautics), there are some other rotorcraft-specific issues that actually are rather challenging for Ingenuity that one only confronts when one gets into the real details of design and test.

First is heat transfer. The thin atmosphere gives almost no cooling. The Ingenuity motors have parts made of beryllium to act as a heatsink, but even then I think overheating is actually the limiting factor on flight duration, not battery energy.

Second is aeroelasticity. There's a similarity parameter called the Lock Number (that I hadn't heard of until I started working with rotor people on Dragonfly) that is important in assessing the structural damping of blade flexing. Again, the thin atmosphere is the problem, it provides no damping so blade oscillations can build up.

Both of these issues get worse as you scale up. So at the NIAC / Powerpoint / student-final-year-project level, yes you can mock out neat-looking hexacopters and stuff in the 10-20 kg range and they look like they should fly, but once you really start poking into the thermal and mechanical design, I bet even those would not work out.

Details of flight 5 announced LINK

Incidentally, does anyone know the eponym of Lock's Number (also called Lock's Constant)? I've traced the following citation, Lock, C., “Application of Goldstein’s Airscrew Theory to Design,” Aeronautical Research Committee, RM 1377, Nov. 1930, but haven't found any biographical information for "C. Lock."

Thursday 13 March 1924, page 17: forthcoming marriages: MR. C. N. H. LOCK AND MISS GILLMAN. The marriage of Christopher Lock, Fellow of Gonville and Caius College, Cambridge, son of the late Rev. J. B. Lock, Fellow of Gonville and Caius College, and Mrs. Lock, with Lilian, daughter of Mr. A. W. Gillman, O.B.E., and Mrs. Gillman, of Streatham, will take place at the end of April.

Tuesday 29 March 1949, page 1: deaths: LOCK.—On March 27, 1949, suddenly, at 49, Park Road, Hampton Hill, Middlesex, CHRISTOPHER NOEL HUNTER LOCK, M.A., of the National Physical Laboratory, Teddington, aged 54.

Microphone on SuperCam worked!
https://www.youtube.com/watch?v=y5niGi4k9vQ

A right MZC frame sequence of the final phase of flight 5 became available. It shows approach, ascent, hover, descent and landing. It is almost a complete sequence but for about 2.5s missing from hovering between 12:34:47 and 12:34:49.

Here is a timestamped, cropped, reduced and white-balanced gif:




click for larger mp4.

And the original frames as lossless webp:

http://bit.ly/Flight5Lossless

Andreas, thank you for your movie. I see a dust devil near the end of the sequence, on the extreme left of the frame, going to the right beyond landing ingenuity !

The complete sequence of MCZ-R pictures of Ingenuity 5th flight has arrived: it shows a beautiful dust devil moving before Ingenuity arrives in the FOV.
Here is a video with speed x4 and contrast increased. We can sometimes see the rotation of the dust devil mentioned before!

I hope the 6th flight goes well--possibly today.

Flights seem to have horizontal traverses at a fixed height of 5 or 10 m. I assume this this keeps the navigation images at a similar scale so it can find landmarks easily. For a future recognizance flight, and to see a significantly larger area, it would be great if Ingenuity went up to 30 m or even 100 m. Would the hight change in image scale confuse the navigation software? Are there other reasons that would preclude pushing the envelope as far as height (other than length of flight for motor heating issues)? Wind? I hope before the end of August Ingenuity hits 200 m vertically with a 360 panorama!!!

Would the hight change in image scale confuse the navigation software?

Approximately 54 seconds into the flight, a glitch occurred in the pipeline of images being delivered by the navigation camera. This glitch caused a single image to be lost, but more importantly, it resulted in all later navigation images being delivered with inaccurate timestamps. From this point on, each time the navigation algorithm performed a correction based on a navigation image, it was operating on the basis of incorrect information about when the image was taken. The resulting inconsistencies significantly degraded the information used to fly the helicopter, leading to estimates being constantly “corrected” to account for phantom errors. Large oscillations ensued.

Despite encountering this anomaly, Ingenuity was able to maintain flight and land safely on the surface within approximately 16 feet (5 meters) of the intended landing location. One reason it was able to do so is the considerable effort that has gone into ensuring that the helicopter’s flight control system has ample “stability margin”: We designed Ingenuity to tolerate significant errors without becoming unstable, including errors in timing. This built-in margin was not fully needed in Ingenuity’s previous flights, because the vehicle’s behavior was in-family with our expectations, but this margin came to the rescue in Flight Six.

I'm a little confused about the 47x47 deg values - assuming it's a typo and that refers to the narrower side, since the images aren't square.