+1...
Sub 7kg with Movi M5
- Thread starter henrysj
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+1...
Of course there does have to be a limit but in this instance the criteria on that limit are poorly defined and punitive to electric craft. The world of cars and trucks has had this one sorted out for many years:
Weight-based divisions of UAS should be based on the gross weight of the aircraft - that includes the fuel, whether it is petrol, aviation fuel or batteries. Level playing field, please!
The 7kg choice cannot possibly be based on "likely damage". Physics doesn't work that conveniently. Being hit by a 7kg weather balloon is unlikely to hurt you in any significant way. Being struck by a 70g bullet, on the other hand, is likely to hurt rather more
. No, I believe the division was an arbitrary choice designed to conveniently encompass "small model aircraft" - as Bowley said above: historical, but still arbitrary. And I'm sorry, Ben, but docile acquiescence is never the way to get sensible, fair laws. Somebody has left a gaping hole in the regs and it needs to be fixed.
You're right there does need to be a distinguishing limit, my big beastie taking off and flying about is a very different proposition than my wee beastie and there's nothing wrong with the stuff you achieve at sub 7. Things are moving so fast I dare say sub 7 won't be a problem this time next year, just doesn't suit me and the choices I made earlier this year...that's life.
Pete
Benjamin Kenobi
Easy? You call that easy?
Of course there does have to be a limit but in this instance the criteria on that limit are poorly defined and punitive to electric craft. The world of cars and trucks has had this one sorted out for many years:
Weight-based divisions of UAS should be based on the gross weight of the aircraft - that includes the fuel, whether it is petrol, aviation fuel or batteries. Level playing field, please!
The 7kg choice cannot possibly be based on "likely damage". Physics doesn't work that conveniently. Being hit by a 7kg weather balloon is unlikely to hurt you in any significant way. Being struck by a 70g bullet, on the other hand, is likely to hurt rather more
And I'm sorry, Ben, but docile acquiescence is never the way to get sensible, fair laws. Somebody has left a gaping hole in the regs and it needs to be fixed.
Fair enough.
But in aviation the definition of weight is a bit more complex by the looks of it:
http://en.wikipedia.org/wiki/Aircraft_gross_weight
It seems people still get confused by the 'weight less fuel' comment in the ANO. It has no bearing on electric aircraft as our machines don't decrease in weight during a flight. Health and Safety guidelines are well known for making 'arbitrary' selections of figures for limits, it is very hard to determine how something will affect the human body as there are so many factors to consider. I imagine 7kg from 400ft would hurt, a lot.
I hope the 7kg limit will stay and as it is a good limit. In my mind it makes some sense to have this limit. It will never be increased no matter how much we ask it to be as increasing the weight increases the perceived risk, and what administrator is going to say 'increasing the risk is okay by me.' :nevreness:
And regarding 'acquiescence', I love that word! Reminds me of the 'fountain of life' or some kind of bioluminescence. As far as I can tell there are maybe three or four people in the CAA directly involved in UAVs and they have a lot on their plate. Let's not stress them too much eh?
What a great thread this turned out to be! Lots of passionate contributors who know their stuff. Thanks guys!
Buzz_Roavr
Member
This truly is the best forum with the most informed discussions.
Thanks to that last wiki link and some further reading on the CAA site and elsewhere, I can now see clearly that the CAA has got it's knickers in a twist over this weight issue.
The only "official" term I can find applied by the CAA to UAS is "operating mass". This term is defined by CAP696 as meaning:
The European Aviation Safety Agency (EASA) uses the same terminology in specifying the 150kg threshold:
The CAA's own website is inconsistent in defining the weight bands associated with UAS. For example, in stating the "Basic Principles of Unmanned Aircraft" they (twice) qualify the 20kg threshold for Small Unmanned Aircraft as "operating mass of 20kg or less". But CAP722 defines an SUA as:
The CAA documentation on UAS is peppered with warnings of its own inconsistent use of terminology (an obvious problem in a fast-evolving field). Since their most recently issued documents refer consistently to "mass without fuel" we must take this as an indication of their intent to use this as the defining mass for a UAS. So why have they changed? They state, in their Small Unmanned Aircraft Operations - General initial guidance:
The only "official" term I can find applied by the CAA to UAS is "operating mass". This term is defined by CAP696 as meaning:
where:
and
This meaning of "operating mass" is confirmed in this (very useful) learning document published by a pilot training resource: http://padpilot.eu/wp-content/uploads/2011/10/SampleMB.pdf.
The European Aviation Safety Agency (EASA) uses the same terminology in specifying the 150kg threshold:
The CAA's own website is inconsistent in defining the weight bands associated with UAS. For example, in stating the "Basic Principles of Unmanned Aircraft" they (twice) qualify the 20kg threshold for Small Unmanned Aircraft as "operating mass of 20kg or less". But CAP722 defines an SUA as:
The CAA documentation on UAS is peppered with warnings of its own inconsistent use of terminology (an obvious problem in a fast-evolving field). Since their most recently issued documents refer consistently to "mass without fuel" we must take this as an indication of their intent to use this as the defining mass for a UAS. So why have they changed? They state, in their Small Unmanned Aircraft Operations - General initial guidance:
Furthermore, in their document "UK-CAA POLICY FOR LIGHT UAV SYSTEMS" (from 2004 but still offered as "current") they do indeed (sorry, Ben!) demonstrate assessment of the potential danger represented by a UAS in terms of the kinetic energy of impact:
It is obvious that, in order to stay aligned with their stated priority of safety, the CAA's classification of UAS must be based on the their maximum weight whilst in flight, i.e. their Operating Mass. Their "mass without fuel" is useless for the purposes of calculating/assessing the danger represented by that aircraft since, in the case of liquid-fueled aircraft, they have no apparent interest in the additional weight of fuel carried and therefore, by extension, the actual Operating Mass. That they have now reacted to confusion over this weight definition by confirming that batteries "do not count as fuel" whilst sticking to their "7kg without fuel" criteria means that the weight of electric aircraft is strictly regulated (fair enough) but that of combustion-powered aircraft is not - an untenable situation. This inequality must be corrected now if future regulations are to maintain any valid link to a demonstrable safety case.
Benjamin Kenobi
Easy? You call that easy?
[MENTION=162]jes1111[/MENTION] Brilliant, just brilliant! I see we both went similar ways with this. I spent all morning reading some of those documents but had no idea how to put it into a coherent paragraph, like you so excellently did! :nevreness:
Kinetic energy of impact! That was it! I knew I heard that somewhere in the beginning. Someone suggested I put it in my OPS Manual, but I declined. And there's me dumbing it down to 'likely damage,' gosh I need to get a thesaurus!
Does anyone use a UAV that takes actual fuel for filming and photography? I could see it being of benefit for the agricultural sector and scanning in the non-visible spectrum but for most of us it would be pointless surely? Smoke and cameras don't go together, although smoke and mirrors do, apparently.:02.47-tranquillity:
I have to ask, how long did it take you to write all that? It would have taken me a day with much editing and head scratching along the way. We need to compile some of these 'informed' posts into one super thread that has real info in!
Kinetic energy of impact! That was it! I knew I heard that somewhere in the beginning. Someone suggested I put it in my OPS Manual, but I declined. And there's me dumbing it down to 'likely damage,' gosh I need to get a thesaurus!
Does anyone use a UAV that takes actual fuel for filming and photography? I could see it being of benefit for the agricultural sector and scanning in the non-visible spectrum but for most of us it would be pointless surely? Smoke and cameras don't go together, although smoke and mirrors do, apparently.:02.47-tranquillity:
I have to ask, how long did it take you to write all that? It would have taken me a day with much editing and head scratching along the way. We need to compile some of these 'informed' posts into one super thread that has real info in!
Oh, not long - just the entire afternoon
I'm hoping that someone can pick this up and carry it into a discussion/meeting with the CAA. The obvious best outcome for us would be that the 7kg limit was altered to define batteries as fuel and therefore in addition to the 7kg but, logically, its more likely to be the other way around: that 7kg is acknowledged as the true Operating Mass and, as such, is applicable evenly to both types. But maybe, in making such a change, the CAA could be persuaded to favour the more public-friendly electric craft by moving the weight limit upwards to match the current notion of a 7kg dry-weight plus a full liquid fuel load - say 10kg
I'm hoping that someone can pick this up and carry it into a discussion/meeting with the CAA. The obvious best outcome for us would be that the 7kg limit was altered to define batteries as fuel and therefore in addition to the 7kg but, logically, its more likely to be the other way around: that 7kg is acknowledged as the true Operating Mass and, as such, is applicable evenly to both types. But maybe, in making such a change, the CAA could be persuaded to favour the more public-friendly electric craft by moving the weight limit upwards to match the current notion of a 7kg dry-weight plus a full liquid fuel load - say 10kg
Benjamin Kenobi
Easy? You call that easy?
Where's [MENTION=6460]Carapau[/MENTION] when you need him....
This really is an excellent thread and much needed in my opinion. Thanks to everyone for their input, especially [MENTION=162]jes1111[/MENTION] for the great summary above.
Another incredibly grey area I have difficulty with is the true definition of a congested area. The ANO defines a congested area as being 'any area of a city, town or settlement which is substantially used for residential, industrial or recreational purposes'. Now to me, 'substantially used' is a very subjective term and open to both under and over interpretation. I spoke to the CAA about this last week and the gist of the conversation was that the same location could be considered both a congested area and a non-congested area depending upon the time of day and activity at the location. During the conversation the CAA used an industrial estate as an example stating that on a busy day it would obviously be considered a congested area but during the evening when the place was fairly empty it would be considered non-congested. Could this view therefore not be extrapolated to a town centre....busy during the day but dead at 5 a.m. on a sunday morning and therefore not a congested area? Somewhat of a rhetorical question that last one but it does sum up my confusion.
Another incredibly grey area I have difficulty with is the true definition of a congested area. The ANO defines a congested area as being 'any area of a city, town or settlement which is substantially used for residential, industrial or recreational purposes'. Now to me, 'substantially used' is a very subjective term and open to both under and over interpretation. I spoke to the CAA about this last week and the gist of the conversation was that the same location could be considered both a congested area and a non-congested area depending upon the time of day and activity at the location. During the conversation the CAA used an industrial estate as an example stating that on a busy day it would obviously be considered a congested area but during the evening when the place was fairly empty it would be considered non-congested. Could this view therefore not be extrapolated to a town centre....busy during the day but dead at 5 a.m. on a sunday morning and therefore not a congested area? Somewhat of a rhetorical question that last one but it does sum up my confusion.
Carapau
Tek care, lambs ont road, MRF Moderator
Im on holiday at the moment and so can't really comment on this as I am too busy drinking beer by the pool and spending good time with the kids! Once I am back I will get back to you having looked into things.
One thing to bear in mind, the 7kg limit is indeed based on KE however the operational environment with SUAS is constantly changing thus too is the need to re-address regulation. I think that the fuel v battery thing is probably more historic and that KE limits are based on the lightest the aircraft is likely to be so as to enable more people to fly. An airframe of a certain size can only take a certain amount of fuel before the fuel makes the aircraft unflyable so its not as daft as it necessarily sounds looking on just the surface. This is just my thoughts on it and I have nothing to back this up but I will try and dig a bit more into this. Anyway, beer, pool and kids are beckoning....
One thing to bear in mind, the 7kg limit is indeed based on KE however the operational environment with SUAS is constantly changing thus too is the need to re-address regulation. I think that the fuel v battery thing is probably more historic and that KE limits are based on the lightest the aircraft is likely to be so as to enable more people to fly. An airframe of a certain size can only take a certain amount of fuel before the fuel makes the aircraft unflyable so its not as daft as it necessarily sounds looking on just the surface. This is just my thoughts on it and I have nothing to back this up but I will try and dig a bit more into this. Anyway, beer, pool and kids are beckoning....
Whilst you enjoy your break, I've been doing a bit more digging...
Working on the basis of the lightest that a given aircraft will be during its flight obviously divorces it from any possible safety case since the maximum weight, and therefore the maximum kinetic energy of impact, is unknown and, effectively, unlimited. Taking the case of a single-rotor heli camera carrier, it is not inconceivable that someone would want to build a machine for the longest possible duration of flight. I checked on various RC shop sites and discovered that Dubro make a range of standard tank sizes right up to "100oz." (which translates to a capacity of just a few drops under 3 litres). It would be simple to mount two of these on a 700-size heli, one each side of the fuselage for balance. The density of glo fuel is (apparently) about 1kg per litre, so let's call the weight of the fuel load an even 6kg. The heli would have no problem with the weight and itself could easily be 7kg dry weight. Thus we've almost doubled the mass (13kg) without exceeding the "7kg without fuel" threshold. Since the kinetic energy formula (KE = 0.5 * m * v^2) shows that the relationship between KE and mass is linear, that means the craft's KE is also nearly doubled for any given velocity. Such a craft would not be difficult to build - indeed, any competent modeler with the will could probably go much further down this path, be it for a heli, a fixed-wing or a multirotor.
It's easy to see that if any of the weight bands (150kg, 20kg or 7.5kg) are to be linked meaningfully to a safety case then they must be calculated on the basis of Operating Mass OM (assumed, for an unmanned craft, to be the same as Take-Off Mass TOM) rather than Zero Fuel Mass ZFM.
If the CAA determined "7kg plus fuel" to be a suitable limit then it's likely they made some kind of estimate of the likely "average" weight of fuel that would still represent "approximately" the same risk level. It would therefore be logical to increase the current 7kg figure. This would also be fairer to existing owners of fuel-powered machines since the change would be "inclusive" rather "exclusive", i.e. the "average" fuel-powered machine that currently fits within the existing limit would not be excluded by the change (and, of course, no electric-powered machines would be excluded). My guess at the "average" fuel load would be about 10-15% of the dry weight (somebody jump in if I'm wildly wrong with that). My proposal would therefore be to alter the threshold to "8kg Operating Mass".
The benefit to electric multirotor craft of such a change would be tremendous. As many have already discovered, 7kg is a really awkward figure, being right about the achievable mass of a "medium lift" machine. A revised figure of 8kg OM would more accurately divide "light/medium lifters" from the true "heavy lifters", as I believe was the intention of this new band in the first place.
Working on the basis of the lightest that a given aircraft will be during its flight obviously divorces it from any possible safety case since the maximum weight, and therefore the maximum kinetic energy of impact, is unknown and, effectively, unlimited. Taking the case of a single-rotor heli camera carrier, it is not inconceivable that someone would want to build a machine for the longest possible duration of flight. I checked on various RC shop sites and discovered that Dubro make a range of standard tank sizes right up to "100oz." (which translates to a capacity of just a few drops under 3 litres). It would be simple to mount two of these on a 700-size heli, one each side of the fuselage for balance. The density of glo fuel is (apparently) about 1kg per litre, so let's call the weight of the fuel load an even 6kg. The heli would have no problem with the weight and itself could easily be 7kg dry weight. Thus we've almost doubled the mass (13kg) without exceeding the "7kg without fuel" threshold. Since the kinetic energy formula (KE = 0.5 * m * v^2) shows that the relationship between KE and mass is linear, that means the craft's KE is also nearly doubled for any given velocity. Such a craft would not be difficult to build - indeed, any competent modeler with the will could probably go much further down this path, be it for a heli, a fixed-wing or a multirotor.
It's easy to see that if any of the weight bands (150kg, 20kg or 7.5kg) are to be linked meaningfully to a safety case then they must be calculated on the basis of Operating Mass OM (assumed, for an unmanned craft, to be the same as Take-Off Mass TOM) rather than Zero Fuel Mass ZFM.
If the CAA determined "7kg plus fuel" to be a suitable limit then it's likely they made some kind of estimate of the likely "average" weight of fuel that would still represent "approximately" the same risk level. It would therefore be logical to increase the current 7kg figure. This would also be fairer to existing owners of fuel-powered machines since the change would be "inclusive" rather "exclusive", i.e. the "average" fuel-powered machine that currently fits within the existing limit would not be excluded by the change (and, of course, no electric-powered machines would be excluded). My guess at the "average" fuel load would be about 10-15% of the dry weight (somebody jump in if I'm wildly wrong with that). My proposal would therefore be to alter the threshold to "8kg Operating Mass".
The benefit to electric multirotor craft of such a change would be tremendous. As many have already discovered, 7kg is a really awkward figure, being right about the achievable mass of a "medium lift" machine. A revised figure of 8kg OM would more accurately divide "light/medium lifters" from the true "heavy lifters", as I believe was the intention of this new band in the first place.
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Droider
Drone Enthusiast
[MENTION=906]JES[/MENTION] just love your work.. quality posts.
We have sub7kg 3 axes GH3/4 /PBM machines with a very comfortable 15 min flight time, we saw this coming at the CAA/EuroUSC meet earlier this year. It aint hard to achieve, just expensive.. but not as expensive as being stuck with a >7kg with work you can't do!
@ angus.. when u home? could do with a meet up.. At Elvington this weekend if you are home.
Dave
We have sub7kg 3 axes GH3/4 /PBM machines with a very comfortable 15 min flight time, we saw this coming at the CAA/EuroUSC meet earlier this year. It aint hard to achieve, just expensive.. but not as expensive as being stuck with a >7kg with work you can't do!
@ angus.. when u home? could do with a meet up.. At Elvington this weekend if you are home.
Dave
This is the thing though, I have seen some things that I never thought imaginable that would be acceptable to do as a safety aspect.
IS it OK to hand catch or take off from a box and not use landing gear to get under the 7KG, if it was that simple then it would be easy, but a bit of a safety hazard.
I have seen quite a few videos lately from people who have PFAW in the UK, and I am sitting saying to myself, how on earth can they get permission for that, there is no way that's under control, or not a chance in hell that thats safe!
I want to play by the rules, but the rules are not as clean cut as they should be.
Droider
Drone Enthusiast
Where does it say anything about how you take off and land? define safe?
Its totally feasible to do it safely with out full size landing gear. Its also feasible to do it with retracts and KEEP twin packs and flight times of 15 mins.
Its also possible to fly for 20 mins with out retracts, its then down to piloting and wingman skills that make it perfectly safe. Its never going to be a one man suck it and see operation. This game is all about team work and confidence in your teams ability, knowing the craft, 'its' capability and 'it' and the 'teams' limitations.
D
You are a magician
I am not having a go at you, I applaud what you do, and I love learning from people but I also have it in the back of my mind that an MR could probably take your head off in a split second if something went wrong.
You said it yourself, define safe..and the definition is not printed in black and white.
Droider
Drone Enthusiast
Nope but an engineer with a passion… problem solving! Its safe as houses ;-) It aint a 700 SR! Ive seen that video!
I can't take all the credit…. Eyeball is my inspiration and the best bouncer of ideas going… He is an Artesian of his craft and his craft are awesome!
Dave
Carapau
Tek care, lambs ont road, MRF Moderator
The CAA's views are that as a battery does not change weight during flight, batteries are very much included in the mass of the aircraft. They should be making this very clear on the BNUC and RPQ course. They certainly did when I did the BNUC course
Yep - no argument with that - the issue is in the precedent set by the latest weight band being "7kg without fuel", contrary to all preceding weight bands established by themselves and EASA and representing, as it does, a separation from the core principles of public safety, with substantial scope for abuse.
Carapau
Tek care, lambs ont road, MRF Moderator
There is no change to the with without fuel. It always has been 7 AND 20kg 'without fuel' and batteries have never been considered 'fuel'. Thus the 20 and 7 kg limits have always been inclusive of battery weight. So what is the 'latest band' or am I missing something here?