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NHS Drone delivery's


EssexBOF

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55 minutes ago, Steve J said:

@oipigfaceA quadcopter with one motor u/s would not have yaw control.

I’m no expert on quadcopters. Is this still true if the opposed rotor can be reversed?

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16 hours ago, oipigface said:

Supposing all the legs are the same weight, taking the leg away from one corner moves the CG towards the opposite leg. The bottom ends of the three remaining legs are sufficient to define a plane and a triangle on it. The projection of the CG onto that plane lies within the triangle (as long as the floor is close enough to horizontal). Therefore the table is stable. It’s true that if you put a pint on the legless corner (or anything heavier than the leg that’s been removed) the table falls over, but the pint falls too. The table on its own won’t.

Yes but it is not stable under all conditions that a table would be used for. Moving the leg into a position of halfway across the side, nearer to the missing leg would stabilize it under all conditions. Anyway enough of that little to do with the drone scenario IMHO

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As long as the remaining supports create points of a triangle which has the CG within them, then the stability is maintained.

The point I was (badly) making, when referencing a table, was that the CG is going to be outside of the triangle of remaining support, if either of the front rotors is damaged. The first time in the flight that the operator might get to know about the damage, will be at the point the machine starts to descend and roll control is lost, when forward speed drops below that at which the wings can control it. 

It is my fear that this may not be over an area of uninhabited countryside, but over the mainly inhabited areas surrounding Basildon, and Southend Hospitals. Broomfield Hospital (a couple of miles North of the City of Chelmsford) is bounded by schools and fields. 

 

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Well, Jef, I agree that six rotors would offer more redundancy, and would increase the safety margin. I’ll make one further point though. The operators presumably have read this thread and understand your point. They could make sure they do not begin a vertical descent until they are immediately (and not at a great height) over the target landing pad. 

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What airspeed do you think a 25kg craft of this diminutive size requires to maintain straight and level flight then?

If it can easily scrub that speed in a short distance to the point at which the controlled vertical descent can then begin, it must be a case of flaring the nose up, and starting the rotors to give an element of reverse thrust and mushing to the point of very little forward speed, so the loss of a rotor will be apparent in that phase, and at that height. I imagine that descent is not allowed below 250ft without the rotors being deployed, from the aspect of noise complaints from the neighbours.

When forward speed has reduced sufficiently for the wings to no longer be able to maintain roll control against the imbalanced rotor configuration, the pilot has to decide whether to try and recover, or to dart the landing zone. If the recover option is taken, a pre-planned alternative sterile ditching site is needed. Recovering might also prove a little awkward when the nose is pointing down and the craft has started a roll (away from the designated landing zone and towards car parking areas, residential areas, or hospital buildings, oxygen storage facilities etc.).

38 minutes ago, oipigface said:

... The operators presumably have read this thread and understand your point. .... 


I hope you are right regarding this thread being read by others with control to do something about the problems, if these matters have not already been mitigated. 

 

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Is that black blob on the inside of the fin a rudder servo?

There are two under the tailplane too. At least there is some redundancy there! 

 

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5 hours ago, Jef Ott said:

When forward speed has reduced sufficiently for the wings to no longer be able to maintain roll control against the imbalanced rotor configuration, the pilot has to decide whether to try and recover, or to dart the landing zone. If the recover option is taken, a pre-planned alternative sterile ditching site is needed. Recovering might also prove a little awkward when the nose is pointing down and the craft has started a roll (away from the designated landing zone and towards car parking areas, residential areas, or hospital buildings, oxygen storage facilities etc.).

In the original use for the design, these drones were built to fill a need to get supplies to offshore wind farms. Although not financially perfect, the option to ditch in a sterile area, is far more accessible there. This makes me wonder if the NHS has not done its own risk assessment and method statements for the use of these particular machines, as they are perfect for their designed use. 

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1 hour ago, pete beadle said:

Are we finished with all this off-subject chair stability rubbish yet? I sincerely hope so

Not quite.  If I lose one of the four 'quad rotors', could I shut down the opposite one and still have enough control to do a semi-rotor-borne 'slow landing' - Harrier style (nozzles 65-75 deg. ish)?

Edited by mikef
'born' corrected to '-borne'
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4 hours ago, mikef said:

Not quite.  If I lose one of the four 'quad rotors', could I shut down the opposite one and still have enough control to do a semi-rotor-borne 'slow landing' - Harrier style (nozzles 65-75 deg. ish)?

If you look at the rotors, they are too close to the boom / nose for thrust vectoring.

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33 minutes ago, Jef Ott said:

If you look at the rotors, they are too close to the boom / nose for thrust vectoring

My proposal doesn't vector any rotors.  Two diagonally opposite 'rotors' are run flat out while the ‘propellor' provides a forward component.  The resultant total thrust is pointing down and aft, keeping us moving forward fast enough to give some lift and maintain control with the moving surfaces.  I can see a rolling component from the 'one forward and one aft rotor running' situation modifying wing flow but it might be manageable.  All speculation, just wondering how a controlled descent might be possible....

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35 minutes ago, pete beadle said:

I've passed the test to be a drone pilot.....

Peter,  So as not to cause confusion, is it the test covering unmanned aircraft you have passed or is there a separate 'drone test'?

This is the one that applies to most RC glider flyers.....

https://rcc.bmfa.uk/rcc

Is that what you are talking about?

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Tone-the-glider
On 22/10/2020 at 09:47, EssexBOF said:

It will be interesting to see if they publish the corridors that these drones will be flying along, as their paths might cross existing model flying sites.

https://www.bbc.co.uk/news/uk-england-essex-54582888

Interesting, I see they a designed to fly at 300 feet above ground level, within our CAA permitted height. Also I would like £1.3 million to develop  this idea.

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