Calculation Needed.......

[Hendricks]

Considering a brushless electric motor of 440 kV powered with a voltage of 24 volts.
Indicate the maximum speed of rotation of the motor.

A. 24 rpm

B. 1,560 rpm

C. 10,560 rpm

D. 440 rpm

 

[olfart]

Here's an explanation of the "KV" designation on a motor.

Meaning of KV for electric motors

According to my misunderstanding of the definition, the correct answer to your question would be C. 10,560 rpm NO LOAD speed, but it also says an outrunner (which DJI uses on the Phantom series) should never be run without a load.

 

[Hendricks]

Much thanks for your reply....

Believe it or not, this question was on the Transport Canada Advanced Drone Operator's Certificate exam.
One of the 5 or 6 obscure and odd questions that really have no relevance to the safe and responsible flying of your Phantom.

I'm sure these questions are included to restrict the number of people passing the exam.

Even pilots with years of flight experience are finding this exam difficult.

We all should remember this famous quote:

"The only time you fail is the last time you try."

 

[Deleted member 29014]

Much thanks for your reply....

Believe it or not, this question was on the Transport Canada Advanced Drone Operator's Certificate exam.
One of the 5 or 6 obscure and odd questions that really have no relevance to the safe and responsible flying of your Phantom.

I'm sure these questions are included to restrict the number of people passing the exam.

Even pilots with years of flight experience are finding this exam difficult.

We all should remember this famous quote:

"The only time you fail is the last time you try."

What the ( Mod Removed ) is wrong with Transport Canada ?

 

[NM_Quad]

I wrote technical exams years ago. Test questions like that are usually designed to see if you have a ballpark idea of how something works or if you have an appreciation for typical operation or safety ... in this case, do the motors/props spin at 24/440/1,560/ or 10,000 rpm? Note how the answers are about times ten from each other. The calculation has virtually nothing to do with it. Just to see if you understand the props are spinning really fast (10,000 vs 1,000 rpm) and the props could hurt you or someone else. Still, an awkward way to test that tidbit of knowledge. Why not just ask, "What's the average rpm of the props on a typical drone when energized or in flight?" with the same exact anwers given. We're mostly hobby pilots of a consumer drone; few of us are engineers (nor should that be required). Even from an engineering standpoint, the KV vs. rpm ratio is pointless on a motor you have no ability or reason to change. To my Canadian friends ... sorry about that (we're probably next).

 

[Deleted member 29014]

I wrote technical exams years ago. Test questions like that are usually designed to see if you have a ballpark idea of how something works or if you have an appreciation for typical operation or safety ... in this case, do the motors/props spin at 24/440/1,560/ or 10,000 rpm? Note how the answers are about times ten from each other. The calculation has virtually nothing to do with it. Just to see if you understand the props are spinning really fast (10,000 vs 1,000 rpm) and the props could hurt you or someone else. Still, an awkward way to test that tidbit of knowledge. Why not just ask, "What's the average rpm of the props on a typical drone when energized or in flight?" with the same exact anwers given. We're mostly hobby pilots of a consumer drone; few of us are engineers (nor should that be required). Even from an engineering standpoint, the KV vs. rpm ratio is pointless on a motor you have no ability or reason to change. To my Canadian friends ... sorry about that (we're probably next).

Why not ask a million RPM, a billion RPM?The question is irrelevant to safety, assuming that was the intent of the question...
A better question.. Do the spinning props of a falling UAS have the potential to cause injury to unprotected persons? T or F

 

[3rdof5]

All i will say is, when it comes to multiple choice questions, when in doubt (C)harlie out lol.

 

[3rdof5]

This question was clearly included as a test to see how many of us know our craft, to see if we know the actual rpm of our props and clearly there's only one logical answer, and correct one.
They are seeing how many of us actually know enough about our aircraft to properly maintain them safe to fly.

 

[Deleted member 29014]

This question was clearly included as a test to see how many of us know our craft, to see if we know the actual rpm of our props and clearly there's only one logical answer, and correct one.
They are seeing how many of us actually know enough about our aircraft to properly maintain them safe to fly.

Unfortunately, that information is not in any UAS manual I have read, unless I'm going blind. I became curious some time ago and searched user manuals on all Phantoms, Inspires and M600. If anyone has the answer and source, I'd love to see it.

 

[Hendricks]

To all who replied earlier........

Yes! Exactly!

This question joins 3 or 4 others on this exam included to NOT test the applicant's knowledge of safety or responsible drone flying, BUT to restrict the successful number of people writing this exam.
There can be no other explanation.
Believe me, as criticism of this exam mounts, there will be pressure on Transport Canada to revise the exam questions.
NOT to make them easier but how about making them relevant and contribute to the education of those of us who really want to fly our Phantoms safely and responsibly?

 

[Remote Pilots Australia]

Could someone enlighten me whether the "Canada Advanced Drone Operator's Certificate " is a recreational or commercial qualification? Not meaning to be insulting to anyone from Canada but it does sort of seem like the government has lost the plot a little as far as R.P.A. goes with the latest legislation.

Calculating (no load) RPM of a motor given supply voltage and motor rating is a standard question on every Australian RePL (Remote Pilot's Licence) exam and I had no problem with it because I was prepared for it by my training provider and it is an accepted part of the syllabus for a "Commercial Operators Qualification". If you want extra leeway to work outside of the standard operating conditions then you should be able to demonstrate higher levels of knowledge. Mind you an Australian RePL adding the the Aeronautical Radio Operators Certificate as I did is usually the better part of a $2000 training course and not exactly light weight.

I think it's "over the top" for a recreational user to be expected to know and when the Australian recreational RPA registration and general knowledge testing comes in later this year I wouldn't expect it to be included.

As far as I am concerned if a recreational pilot can show a knowledge of the general rules which should include safety issues, how to perform a basic pre and post flight check to make sure it's safe to fly and how to handle LiPo batteries safely then you should be good to go.

Edit, yes it's answer "C". Simply put, multiply the KV rating by the supply voltage = answer

Regards
Ari

 

[Hendricks]

Yes, the correct answer is indeed "C";however, the real correct thing here would be for Transport Canada to have another look at these exam questions and ultimately revise the questions to better reflect what we are all after here.
That being, to educate and produce(through certification) drone pilots who know the rules and have been schooled in the responsibilities attached to the safe operation of your Phantom.

I feel this is Transport Canada's first 'go around' with this and they will be hearing the constructive criticism from people who have been flying drones for years and cannot see the relevance to some of the questions being asked.

And there are 'trick questions' as well.

Example:

'What is the recommended amount of time a pilot should take between donating blood and resuming flying duties?"

A. 24 hours.

B. 12 hours.

C. 48 hours.

D. 72 hours.

The Transport Canada and FAA rule is 24 hours.

There is a recommendation a pilot should take 48 hours between donating blood and resuming flight duties.

So, for this exam, Transport Canada is looking for the 'recommended' time period......
NOT its own stated rule!

 

[Remote Pilots Australia]

however, the real correct thing here would be for Transport Canada to have another look at these exam questions and ultimately revise the questions to better reflect what we are all after here.
That being, to educate and produce(through certification) drone pilots who know the rules and have been schooled in the responsibilities attached to the safe operation of your Phantom.

No argument here

I feel this is Transport Canada's first 'go around' with this and they will be hearing the constructive criticism from people who have been flying drones for years and cannot see the relevance to some of the questions being asked.

That's fair enough as far as it goes but let's be honest here, U.A.V. / R.P.A. legislation is fairly new for most countries as consumer aircraft are an advent of really the last 3 or 4 years. Australia (Nanny state that it is) had laws in before most countries and the next reworked legislation to be released mid year here will be (I think) our fourth revision. I have to say that even the Australian first set of laws was better done than the set you are currently stuck with.

And there are 'trick questions' as well.

Example:

'What is the recommended amount of time a pilot should take between donating blood and resuming flying duties?"

A. 24 hours.

B. 12 hours.

C. 48 hours.

D. 72 hours.

The Transport Canada and FAA rule is 24 hours.

There is a recommendation a pilot should take 48 hours between donating blood and resuming flight duties.

So, for this exam, Transport Canada is looking for the 'recommended' time period......
NOT its own stated rule!

Funnily enough someone else gave this exact example in another thread I responded to and my general answer was this is the same as here. Last year the hard a fast rules around operations near a non controlled aerodrome were just scrapped and R.P.A. pilots have to use their own judgment under the "must not endanger life, property of other aircraft" rule but even though there are no laws anymore there are recommended practices. When you do the RePL here you are expected to answer with the "recommended practices" and that's fair enough in my book because, the RePL is a commercial certification allowing you to operate outside of the standard operating conditions imposed on other pilots with the correct measures in place.

I'm still not sure if the "Canada Advanced Drone Operator's Certificate " is a commercial or hobbyist certificate. If it's commercial then it's a fair enough position to expect you to answer with the recommended procedures as long as you KNOW you are expected to answer that way (which I understand you are not informed at this time).

If it's a hobbyist certification then it's just over the top.

As it stand your legislation is almost punitive rather than educational and if they really want to foster a culture of safe operation and not drive you guys out of the air then you are right, they are going to have to have another look at this I think.

I wish you all the best with it all

Regards
Ari

 

[With The Birds]

The correct answer is none of the available responses are correct.

While KV will get pretty close to giving you the RPM/V for a brushed DC motor it has little relavence, at least in the same context, for an AC or brushless motor. For brushless motors the KV is the voltage that will be measured between any two phases when the motor is driven by an external source. Spin a 400KV motor at 400rpm and you should see 1V on a connected meter (the measured voltage will actually be root2/2 of the DC equivalent). This is because the KV really tells us what the back EMF of the motor is.

So the real answer is the voltage applied to the motor doesn’t determine the RPM. RPM is a function of line frequency and number of poles.

 

[Remote Pilots Australia]

Spin a 400KV motor at 400rpm and you should see 1V on a connected meter (the measured voltage will actually be root2/2 of the DC equivalent). This is because the KV really tells us what the back EMF of the motor is.

So the real answer is the voltage applied to the motor doesn’t determine the RPM. RPM is a function of line frequency and number of poles.

This is technically correct of course and good point, like me you're obviously technically trained.

However here in Australia for the purposes of C.A.S.A. mandated RePL examination and (apparently) for the Canadian examination a nominal value of KV value x volts applied is considered "close enough for country" as they say which is why I said "roughly speaking" or words to that effect in the previous post.

These are bureaucrats ... you don't give them the right answer, you have to give them the answer they expect to see.

I have a number of advanced trade qualifications, also an advanced class amater operators certificate, a maritime operators certificate with the 30wpm CW (morse) qualification (that dates me lol) and have had the honour of serving as a director of the Wireless Institute of Australia.

The number of things in my RePL course and Aeronautical Radio Operators Certificate course that were technically or procedurally plain wrong or misleading was uncomfortably high. I just pointed them out to the instructors so they could give the "real scoop" to future trainees on the side but answered in the tests with the answers taught in the syllabus.

It was too much money to blow by being a smart guy.... but it didn't sit easily with me.

Regards
Ari

 

[Deleted member 29014]

This inquiry was obviously included as a test to perceive what number of us know our specialty, to check whether we know the real rpm of our props and unmistakably there's solitary one intelligent answer, and right one.

They are perceiving what number of us really think enough about our flying machine to appropriately keep up them safe to fly.

Could you explain how knowing my motors spin at 10,500 rpm versus 12,000 rpm or 9,000 makes me a safer pilot?
Do you believe that if this bit of info was important to safe flying it should be included in the manual by the manufacturer?

 

[With The Birds]

Could you explain how knowing my motors spin at 10,500 rpm versus 12,000 rpm or 9,000 makes me a safer pilot?
Do you believe that if this bit of info was important to safe flying it should be included in the manual by the manufacturer?

Good question.... it seems @mina3000 has deleted their post- I’m curious also to understand what they thought the correct answer was.

 

[Remote Pilots Australia]

This question was clearly included as a test to see how many of us know our craft, to see if we know the actual rpm of our props and clearly there's only one logical answer, and correct one.
They are seeing how many of us actually know enough about our aircraft to properly maintain them safe to fly.

That's all fine and understandable .... at a professional or commercial level. Recreational boat owners (here at least) are required to show a level of understanding of the rules governing use of the water and basic operational ability. They're not questioned on "displacement mechanics" however. By extension it's a bit over the top for a recreational R.P.A. pilot to need this level of knowledge IMO.

Regards
Ari

 

[Remote Pilots Australia]

Could you explain how knowing my motors spin at 10,500 rpm versus 12,000 rpm or 9,000 makes me a safer pilot?

As far as I can see as a recreational pilot there it doesn't make you any more safe in any way what so ever and is not required.

Even as a commercial operator unless you had need of these calculations as part of a process to determine lift capacity on custom built R.P.A. or perhaps calculations on engine life under maximum load or something obtuse like that it's pretty well redundant information but perhaps there's something I'm missing.

I knew it from my electronics background, I was taught it again when I did my RePL cert. Ask me again in 5 years if it has ever been a factor or I've used it. I have my doubts. A recreational pilot? Never going to need to know it.

Regards
Ari

 

[3rdof5]

That's all fine and understandable .... at a professional or commercial level. Recreational boat owners (here at least) are required to show a level of understanding of the rules governing use of the water and basic operational ability. They're not questioned on "displacement mechanics" however. By extension it's a bit over the top for a recreational R.P.A. pilot to need this level of knowledge IMO.

Regards
Ari

I completely agree, as I stated, I dont believe the question is relevant to the actual knowledge that is required for hobbyist flying, and nor would answering that question wrong likely cause anyone to fail the test. I believe it's more "survey" based to provide info back about just how much we actually do know above and beyond the minimum. I have no issue at all with that question.