Powerbox 'Royal' Spectrum in over 20kg models?

[graham stanley]

There appears to remain considerable ambiguity on this topic. In some instances a single point failure that would lead to loosing control is acceptable, in others there seems a desire to tick boxes that mainly have an impact on the wallet.

Whilst we continue to accept one pilot and one Tx, is it not time to decalare "approved" manufactures 2.4 solutions, providing they have a reliable power system. The latter I take to include two power packs, though that is another debate.

As I read Ivan's response, it seems that the working practice is to try and cover MOST single point failures in the aircraft, but not all, that lead to partial or in some cases total loss of control, but at the expense of more complex on board systems with an inherently greater chance of failure. The chance of a hardware failure is closely related to the number of components used, and inparticular the number of interconnects. The chance of a software failure increases as the amount of code increases.

I believe there might be value in discussing a simpler, and therefore less likely to fail solution, that might have less redundancy. Given that in some cases failure is going to lead to a "controled crash" at best, would the overal safety be improved with a "simple" reciever system?

We do not have robust reliability data on the systems we use that allow formal calculations to back up the argument either way. In the absence of this data, the jugement of the LMA technical experts is required based on subjective opinions.

[Phil Clark]

.....................and turning to the very first post. The unit contains ONE master receiver and requires at least one satellite to maintain signal validity. There is only ONE controller handling the data from the "receivers" as it is not possible to fit two without some very sophisicated software which we use in the commercial world, and loss of a few channels. The output stages to each of the matched output servos are individually set so any failure of one will not affect the others. The power supply does have dual systems throughout.

The installation of one of these units in an over 20kg model does NOT meet the technical requirements of the CAA guidelines and Power Box actually recommend the use of their RS system which does meet the requirements and which I can confirm Tonys comments that they have been well and truly tested in UAVs

But I was not asking about the Royal RRS. As previously stated, I was asking about the Royal Spectrum 2.4. Your comments are the complete opposite of what Tony said in his 1st reply.

I'm afraid it's obvious there was complete misunderstanding/lack of knowledge of the 2 systems. To me, this points VERY CLEARLY towards the need to a list of 'approved’ systems from the various manufacturers. Personally, I cannot understand why this has not been adopted in the past. It wouldn't be a 'bash the supplier' list (you can’t use that, it’s no good!!)......simply a list of systems that have been investigated, checked/test and approved as 'complying' with the CAA's requirements. If we have this in place (and add to it as new systems become available) then all of this ambiguity over what we can & can’t use will be avoided.

The sooner this happens, the better.

Phil

[Simon Willey]

In my previous post I said that you must have tested a lot of systems. You must have a list of equipment that you will accept for these models.
If an inspector came to look at a model I am building and I asked him to recommend the way forward in my radio installation then surly he must have something to refer to to recommend it.
With the sort of systems you are talking about then there can't be that many different ways of doing it.
I can't see any reason as Phil has stated that a list of equipment should not be made available that is suitable to use.
Surly its about time that the LMA did this.
There must be a register of all the over 20kg models flying which you have passed so surly that would be a perfect place to start.
Could there not be a section on this site that lists all the equipment fitted to these models.
As more systems or equipment gets passed then it could be added.
This would make it a lot easer for newcomers to the large models to get an understanding of what's needed.
The bit that still seams strange is that an LMA inspector asked a sensible question about a piece of equipment and was given the wrong answer , which could have led to this being fitted to a model. You all need to be singing from the same hymn sheet.
I really hope that something can be sorted out as it would be a great step forward.

Simon

[DAVE JOHNSON]

Firstly--thanks to all the contributors to this interesting thread---The LMA committee have noted all the comments raised and will be discussed at a meeting later this month.Ivan has posted the official line/agreement between the CAA/LMA ,and as he says,its been proven over the years,but we do realise that there are many new devices coming out that "may"comply,we are in contact at the moment with manufacturers and hopefully we will have the relevant info from them to discuss at the meeting.Only then will we inform our inspectors of the findings-----in the meantime ,this thread will be locked --its not helpfull advising what we should and shouldnt be doing,our safety record is paramount.

[Andy Boylett]

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[Andy Boylett]

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[Simon Willey]

This set up seams to be a recently passed over 20kg model , so one would presume the LMA believe it is two separate systems. As you say perhaps more confirmation is needed as was asked for a while ago.

the radio link is via twin Futaba 6014 receivers through a Powerbox RRS and backer set-up,servos are predominantly JR8911 and 8711 items.

Si

[Andy Boylett]

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[Martin Waller]

What happens if your transmitter elevator or aileron potentiometer wiper fails. Your plane will crash. This is not very likely but does happen. Similarly my MC24 processor board failed two years ago at a show transmiter book in. If an elevator servo fails it is likely to go to one end of the track giving full deflection. (one of the push pull amps failing or pot wiper)

The main aim is to double up on the main causes of failure these being power supplies and the radio link. In the Power Box the combining amp is not likely to be affected by radio interference or signal blanking in fact it will be extremly reliable as are good servos like those mentioned. The Power Box approach with two separate receivers plugged into the RRS (receiver redundancy system) is a good approach and batteries, regulators and receivers are all duplicated with FULL REDUNDANCY. If any onefails the plane will still be under FULL control not partial control. With the old cross over system you would loose half the controls for a receiver fault. It is possible to land some planes on one aileron or elevator providing the failed surfaces are at neutral and that is not necessarily going to be the case.Undercarrige would be likely to be hung up or rudder lost unless two servos used then one could be on failsafe neutral with the other fighting against it to move the surface so huge current drain on the good system with only one aileron and elevator. throttle could also be stuck open although failsafe could close it if fault left failsafe OK. Battery failure could result in deflection. All these systems have weaknesses, it is a question of a balanced least risk approach. The transmitter is completely forgotted in all these discussions and is a weak link particulaly the control pots. The Power Box processor (final stage which selects the best signal) is liekly to be at least as reliable as the transmitter electronics.

M J Waller LMA 1237

[tony hooper]

I am sorry that this issue still gets raised because I thought it had been resolved some time ago. Martin Waller has explained the issues extremely well - particularly in his comment about "lessening the risk" rather than trying to claim that there should be no risks at all. Some time ago we resolved with the CAA that the "single point of failure" issue was practically impossible to attain with the cost of our systems and the "minimisation of risk" should be our overarching concern.
When the issue was raised previously we obtained a formal statement from the Powerbox manufacturers and I am now publicising their reply which was circulated to our Inspectors - I hope this will settle the issue . Incidentally the few typos errors are as received because I would not like to be accused of "doctoring" the statement.

"All PowerBox products have redundancy inside. This means the complete powerpath is double inside (also in the small PB Sensor). We have 2 microcontrollers, 2 regulators, 2 electronic switches inside. This 2 pathes are running absolute independent, they are connected together not until the end – at the servo output.
Also the signal pathes are doubled: all channels are running through a 2 way amplifier. The supply for this amplifiers is also doubled.

If you want to have full redundancy also for the receivers we have 2 products: PB Champion and PB Royal. In this 2 PowerBoxes RRS is included. The RRS is also a double system controlled by 2 microcontrollers, switching one receiver signal to the other, if one receiver fails or has no signal. You don´t loose the half plane with this system, as all important channels (up to 7) are switched to the “good” receiver.


This is the main difference to all other manufacturers worldwide. We are the only power supply manufacturer who has complete redundancy. Because of this a lot of civil aviation authority worldwide admitted PowerBox Systems as redundant power supply for large and x-large planes.


Kind regards
Richard Deutsch[/b]

[Simon Willey]

Thanks Tony.
That seams to clarify the LMA's Veiw on this. Its a shame you did not post that post when the thread was unlocked.


Thanks Simon

[tony hooper]

Simon
Thank you
I have only posted this information to try and settle this issue. The information was circulated to Inspectors only as background information because members must accept that the LMA cannot, and never have, approved or not approved a particular brand of radio or ancillary systems.
We have always appointed Inspectors on the basis that they have not only built large models but also flown them , and operated them successfully over a period of years. In doing so they have aquired a great deal of knowledge and experience. In this context all projects that are registered Over 20kg are allocated to an Inspector and we try to ensure that there is a very early liaison between the builder and the Inspector about both the airframe and the proposed radio installation before any expenditure is incurred. Anyone registering an Over 20kg model would follow this procedure which is a one to one system for each individual project.
If you get to the stage where you feel you would like to build an Over 20kg model then you will be able to witness the system first hand.
Obviously we try to provide general advice to Inspectors and they also do a great deal of "behind the scenes" liaison with each other about issues but at the end of the day we trust them to approve a final product which meets the LMA (and perhaps more importantly the CAA) standards.
We have been particularly pleased to note that some 30 Over 20kg aircraft are now operating on 2.4Ghz (some of them changed from 35Mhz) and both the test flying and public show safety record has been excellent - a recent audit carried by the CAA on our procedures has confirmed this.

[Simon Willey]

Tony
Thats good and it gives us Novices a bit more of an idea of what is needed.
As I said above that post answered most of the questions.
I do hope that one day soon I will be asking to register a model on this scheme if next years plans come together.
I also appreciate that trying to recommend a system to use is very model dependant and to some degree what each inspector feels is needed and this can vary between them. Also the LMA do not want to bee seen to be favouring one brand more than another.
The one thing that I wanted to understand , which I was struggling with when using these powerbox items is that there is a single point of failure , but as you have explained the risk of that part of the device is rated now more so than the single point of failure at the other end which is the TX and so is acceptable with the LMA.

Thanks Tony , I really appreciate you clearing that up.

I hope we can have future discussions on the equipment in Larger models with the reasons why , and how they vary from installation to installation to achieve the required standard needed for that model. I would think it would give some of us a much better understanding of the whole thing.

Have a good Xmas Tony

Simon

[Andy Boylett]

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[John Greenfield]

Andy

If you are looking for advice, especially about a specific model or installation, the best place to go it to your inspector. He will have been appointed because of his knowledge of large models and installations. The also has the support of all other LMA inspectors and the LMA safety panel to seek info and resolve any issues.
It is very difficult to give accurate "general" advice as every model and installation can be different and what works for one model may not necessarily be the best for another. There is also in most cases more than one way to achieve the desired outcome in terms of reliable safe installations.
Use your inspector, that is what he is there for and as you know to LMA members it is a free service.

Happy Christmas to one and all.

John

[Dave Parry]

As a relatively new LMA member looking to answer lots of questions I have found it quite difficult to locate information. This forum is execellent for contacts and asking questions. The only problem is that if something has been discussed previously it can be extremely difficult to read back through very long lists of posts.

Regards
Andy

Hi Andy, have you tried the Search in the top right hand corner of the title most people forget it is there.

Merry Christmas to you all

[Andy Boylett]

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[Dave Parry]

I think you are right Andy that needs a new thread, I feel the reason you don’t find the answers you want on here is because as John Greenfield has pointed out most members sort these problems out with their inspectors who are there to help you every step of the way, having said that it doesn’t stop you asking the question to a wider audience, but I am not sure you would be get the right answer, not everybody on this forum is in the LMA.

All the best.

[John Rickett]

Andy,
Spar sizing, as with any other aspect of model design is empirical and as such there very little reliable data recorded. By definition, the designer builds on the experience of what has worked or not worked in the past. This is why when designing a new model, its best to take incremental steps. One of the challenges in large models, and the fun, is the (hopefully) eventual satisfaction in proving that a certain design lives up to expectations. We are not constrained by design codes, as a proclaimed engineer you may find that frustrating but for most modellers its a freedom they enjoy.
I would advise you to get in touch with previous builders of similar models to your own project, and most importantly, draw on the experience of the inspector and discuss your ideas with him- the whole purpose of the inspection scheme is to uncover weaknesses before its too late.
As a confirmed cynic, I'l say that if you want to build an aeroplane bound up by rules, regulations, codes and standards, then build a microlight - but if you prefer to do you own thing (within reason) build a large model!

[Nigel Wagstaff]

I know it has been some time since this thread was serviced with a comment.

I am currently building a +20Kg model and would like to know with a simple "Yes" or "No" as to if the Powerbox "Royal" Spektrum unit is approved for such models.

https://www.powerbox-systems.com/produkte/powerbox-systeme/powerbox-royal-spektrum.html

If this unit is NOT approved, can I be given a list of configurations that can be used to enable full control of the model should there be a failure in part of the equipment.

While I understand we can have 2 receivers with twin batteries set up on alternate control surfaces I believe something better (safer) must be possible these days.

Nigel