But at the altitude you would want to fly this most of the time even a BRS may not open in time. A cirrus is a at least most likely gliding or has some lift at deployment if an engine failure, not generally dropping like a homesick rock. How many chutes will operate in the 100-300 agl range? Add in the delay to respond you've just cut it in half to 50 - 150 ft agl by the time the chute starts to deploy as you fall vertically.

If you have no airspeed (hover), the chute will be sucked back into the rotors and make chop suey of the lines. Visualize the air flow patterns in hover and you quickly see this will be a major problem.

If you shutoff the motors, they take a while to spin down and you are in free fall. Then the motors will spin up again backwards (if you are still upright).

You also have to account for a motor that is erroneously making too much power. A control system failure can easily flip you over.

So, chute doesn't work in hover, or in forward speed. Now what?

Either make the system very reliable, or provide an ejection seat. Anything else?

Example showing the sophistication achieved with UAV multicopters:

https://www.youtube.com/watch?v=w2itwFJCgFQ

Mike C.

That may be "sophisticated" but I'd be willing to bet there's zero redundancy or any real fail-safe aspects to the design. We could easily make an airplane autopilot which was "sophisticated" enough to allow anyone who can drive a car able to "fly" the plane including takeoff and landing for very little more than the cost of a STec-55. But in the event of virtually any significant malfunction the airplane would be toast if the pilot wasn't competent to take over manually. And to some extent I'd expect that it would actually be easier to handle a power loss with automation in an airplane vs a multicopter.

The state of the art FMSs in modern air transport designs could easily be taken one step further to the point where the pilot never touches a button after starting the engines with the flight plan plus any re-routes delivered digitally from ATC. But it's pretty darn difficult to design a control system to handle unforeseen problems.

Do as the Russians do: blow the blades first, then pull the handle and fire the BRS. Better yet, let George take care of them both.
Robin

For quads, you are right. If you have 6 or more rotors, then they can be redundant. The control system is naturally correcting for imbalances in thrust. There are videos online of people abusing their drones and they fly fine down some number of motors.

This machine had 18 rotors, so it could lose quite a few before not flying. The loss of motor/battery isn't the critical thing, the control system is. So, like a FBW airplane or FADEC engine control, it would need multiple redundant channels of control.


This form of flying doesn't allow manual control to any reasonable extent. All the RC drones you see have sophisticated stability augmentation systems using inertial sensors. A human can't fly the motors directly, the thing would be upside down in seconds.

The only two options are to make it so reliable it doesn't fail, or to provide an emergency escape mechanism like chute or ejection seat if it does. This is the same choices a FBW airplane has, and they went with the "make it so reliable" approach there.


Very much so.


The human is the best analytical computer capable of handling exceptions.

Mike C.

If George is working, then the thing is flying fine. George can handle 1 or more motors failing.

The problem is if George fails. That's when you need an escape plan or more than one George.

Mike C.

30 minutes If I lose the engine on my Bell 47, I'm probably going to be on the ground in 30 seconds.

Glenn

FWIW, I've flown both R/C helicopters and quadcopters with no stability augmentation and I can attest that it is indeed possible but I agree it's a lot harder than flying a fixed wing and I wouldn't want my life to depend on that skill.