Why does the FAA Part 107 test require learning apparently unnecessary knowledge?

[Dangerly]

Angle of attack also applies to propeller blades, which are essentially rotating wings and thus are equally susceptible to stalling under conditions of excessive angle of attack.

That said, our RPAS tests here in Canada also include some questions which are ridiculously inapplicable to drone flying, like the one about scuba diving.

Okay, you got me wondering. What in the name of Neptune do you need to know about scuba diving to pass your RPAS?

 

[pentatony]

Angle of attack also applies to propeller blades, which are essentially rotating wings and thus are equally susceptible to stalling under conditions of excessive angle of attack.

That said, our RPAS tests here in Canada also include some questions which are ridiculously inapplicable to drone flying, like the one about scuba diving.

DON'T YOU ALL GET IT? STALLING ONLY OCCURES IN LIQUID FUELED AIRCRAFT. Last time I checked drones are all electric. THEY DON'T STALL. The pilots of uav's have to purposely make them stall with special emergency off stick maneuvers. Why do we have special emergency shut doen procedures, because they won't turn off unless we force them too. Otherwise they don't. At least not in the way fixed air or helicopters do.

 

[Robert Prior]

What in the name of Neptune do you need to know about scuba diving to pass your RPAS?

He may be referring to a question about anoxia, which was included on the sRPAS exam I wrote in 2019. Probably came in from the regular pilots exam, because only a very few sRPAS pilots will need to worry about it. (There aren't many mountains in Canada where you need oxygen at the summit. Maybe none.)

 

[Robert Prior]

STALLING ONLY OCCURES IN LIQUID FUELED AIRCRAFT.

This is a joke, right?

Engine stall vs. dynamic stall?

Stall (fluid dynamics) - Wikipedia

en.wikipedia.org

 

[Robert Prior]

What I should have done was an emergency CSC power shut off and lost the drone in the water.

You should check to see if the power-shutoff position of the joysticks will actually shut off the power in flight. The bahaviour can be changed in the settings — I think to hover-in-place. Can't remember whether the default behaviour is to shut off the motors or hover the aircraft.

 

[Zbip57]

Okay, you got me wondering. What in the name of Neptune do you need to know about scuba diving to pass your RPAS?

It was another example of an RPAS exam question pulled straight from the general aviation knowledge base, but really not at all applicable to drone flight.

If you've just finished scuba diving, then step into your airplane and climb to high altitudes, you might suffer "the bends" from nitrogen gas in your bloodstream. Scuba divers need to go through a sufficient decompression interval before flying.

I think Transport Canada faced some ridicule for including that question on their drone tests. If you're standing on the beach after scuba diving, it really doesn't matter how high you choose to fly your drone, does it?

 

[Zbip57]

If your flying a dragon fish, it will immediately revert to quad mode if a stall occured, even if that possible with a drogon fish. It's an electric motor, it won't stall.

DON'T YOU ALL GET IT? STALLING ONLY OCCURES IN LIQUID FUELED AIRCRAFT. Last time I checked drones are all electric. THEY DON'T STALL.

That, right there, is sufficient justification for the FAA's insistence that drone pilots require at least some knowledge of how aerodynamics work.

 

[Dangerly]

You should check to see if the power-shutoff position of the joysticks will actually shut off the power in flight. The bahaviour can be changed in the settings — I think to hover-in-place. Can't remember whether the default behaviour is to shut off the motors or hover the aircraft.

I believe the default is off, iirc. Yes, it's important to test it once. I tested it over my bed.

 

[MS Coast]

DON'T YOU ALL GET IT? STALLING ONLY OCCURES IN LIQUID FUELED AIRCRAFT. Last time I checked drones are all electric. THEY DON'T STALL. The pilots of uav's have to purposely make them stall with special emergency off stick maneuvers. Why do we have special emergency shut doen procedures, because they won't turn off unless we force them too. Otherwise they don't. At least not in the way fixed air or helicopters do.

Whoa, now.

With respect to aircraft, a stall occurs when the airflow over the wing is slowed or disrupted and the lift is no longer able to support the aircraft. It has nothing to do with the source of the power. Stalls can happen with piston aircraft, jet aircraft, gliders, and aircraft with electrically driven propellers.

You're thinking of stalling a motor, as in letting the clutch out too quickly without apply enough accelerator.

 

[Cymruflyer]

Angle of attack also applies to propeller blades, which are essentially rotating wings and thus are equally susceptible to stalling under conditions of excessive angle of attack.

That said, our RPAS tests here in Canada also include some questions which are ridiculously inapplicable to drone flying, like the one about scuba diving.

Although your analogy of a prop is like a wing, is for the most part, correct, you can change the angle of attack of your wing, to the point of a stall and if low to the ground, a possible crash, but you can't change your drone's prop pitch.

With a drone propellor, you cannot change its angle of pitch (equivalent of a wing's angle of attack) though they do make props for fixed wing aircraft that are variable pitch types, but that is a very different thing. Due to that, your analogy is a bit pointless, because you are never going to take the drone prop's pitch to a critical angle of attack, like you can a wing. It is never going to happen, but I understand what you were trying to say.

 

[Cymruflyer]

DON'T YOU ALL GET IT? STALLING ONLY OCCURES IN LIQUID FUELED AIRCRAFT.

Now that is one of the dumbest statement I have ever read here on the forum. For those who may not know or are new to flying, that statement is totally wrong and should be disregarded by all who read it. Of course, piston engines and jets are liquid fueled, because jets use a basis of kerosene as fuel. However, even electric powered aircraft, if not a drone, can and do stall. I'm assuming you are speaking of a wing type aerodynamic stall and not an engine stall, which are two different things, of course.

 

[Starz]

looking at the Part 107

Just curious. What is your goal in this?

 

[rickmurray1989]

I took my 107 for grits and shins and was amazed at how much confidence I gained just from the experience. Definitely made me a better pilot.

I agree. I am proud to be a 107 commercial UAS pilot, and the more that I can learn about and understand general aviation, the better I like it.

 

[MavicAir2Marc]

If your flying a dragon fish, it will immediately revert to quad mode if a stall occured, even if that possible with a drogon fish. It's an electric motor, it won't stall. Regardless, if you talk fixed wing, then let the fixed wing flyers take the 107. Quad pilot's need and should have a different exam.

It's an Autel drone, what it's supposed to do and what it actually does are 2 different things.

 

[Grandpa]

I would rephrase that to be it makes you a more aware recreational pilot. I got my 107 for exactly that reason and do not intend to do commercial work.

I would argue that having more knowledge makes me a better pilot, simply by definition. Just knowing how to react to unexpected situations, no matter if it is weather related or air traffic related, makes me a better pilot than just passing the TRUST.

 

[Ty Pilot]

I started looking at the Part 107 practice tests, and I was struck by how much "useless" knowledge seems to be required. A good example would be learning that the wrong angle of attack causes a stall for a fixed wing aircraft. Can someone explain to me how this specific knowledge about angle of attack would ever help a drone pilot?

I would agree that there are some parts of 107, that have very little - to nothing, to do with UAs operations. This is underscored by the fact that recurrent 107 tests have basically dropped an entire area of study that is on the initial.

I started flying fixed -wing UAs a very long time ago (1978), and flew right up to a few years ago. Over that period, I gained a lot of experience the good ole' fashioned way - crash and loss. Looking back to studying for my initial 107, at first I too had similar thoughts as to 'why' some of the categories in the 107 even mattered. But as I studied, it became clear that a lot of thought and analysis had gone into that test.

It was as if they had managed to put into words the very things that are not intuitive but will play a major role in ones aviation career. In particular I am talking about all the thought processes, good and bad, that a pilot should and should not have. Things like risk management, hazardous attitudes, airspace knowledge and decision making.

Earlier you asked someone how the 107 made them a better pilot. Since there is little to no skill needed in flying a GPS drone, it is the mental preparedness and overall understanding of a drone pilot's responsibilities that make a drone pilot better.

 

[Dangerly]

Just curious. What is your goal in this?

I have two main goals: Fly safer, and avoid getting fined by the FAA because I generated good will from a drone photo. It's this situation in particular I worry about:

Me: "Hey, can I take a photo with my drone over your property?"
Other person: "Sure, as long as I get a copy I can use."

My understanding is that this arrangement may be perceived as generating good will for me and would land me a big fine.

 

[Zbip57]

[...] your analogy is a bit pointless, because you are never going to take the drone prop's pitch to a critical angle of attack, like you can a wing. It is never going to happen [...]

A non-variable pitch propeller blade has a constant pitch angle relative to the motor shaft, similar to how a fixed-wing aircraft wing has a constant angle of pitch in relation to the aircraft's fuselage. In both cases though, the airfoil's critical angle of attack depends on the direction/speed/density of the airflow relative to the pitch angle of the airfoil.

Sure, it's not common to see propeller stall in multirotor drones, but there certainly are conditions that will result in this condition. Simple example, if you add too heavy a payload, no matter how much power you apply to the motors without also adding larger propellers, there is a limit to how much lift can be produced. Those prop blades will stall.

Or, even without additional payload, reducing power to below some critical level will cause the blades to stall and the drone will fall out of the sky.

Propeller blades can be forced to stall during certain flight manoeuvres, no matter how much power is applied to the motors. It has nothing to do with variable pitch propeller blades. It's all about the speed and angle at which the airflow is introduced into the propeller blades.

Do a search on "Vortex Ring State", or check how many people have reported crashing their DJI Avata due to "Yaw Washout".

 

[Jeff A]

I started looking at the Part 107 practice tests, and I was struck by how much "useless" knowledge seems to be required. A good example would be learning that the wrong angle of attack causes a stall for a fixed wing aircraft. Can someone explain to me how this specific knowledge about angle of attack would ever help a drone pilot?

Of course there is "useless knowledge in the Part 107 test. It's an FAA Exam, HELLO! I have been taking FAA exams most of my adult life. On the other hand, issues like angle-of-attack are important to learn. How about Airfoil icing? Well your basic Quad has 4 sets of airfoils in which ange-of-attack are important, and I have seen video where forum members here have subjected themselves to prop icing, which adversely effects angle-of-attack. Have fun studying.

 

[Dangerly]

A non-variable pitch propeller blade has a constant pitch angle relative to the motor shaft, similar to how a fixed-wing aircraft wing has a constant angle of pitch in relation to the aircraft's fuselage. In both cases though, the airfoil's critical angle of attack depends on the direction/speed/density of the airflow relative to the pitch angle of the airfoil.

Sure, it's not common to see propeller stall in multirotor drones, but there certainly are conditions that will result in this condition. Simple example, if you add too heavy a payload, no matter how much power you apply to the motors without also adding larger propellers, there is a limit to how much lift can be produced. Those prop blades will stall.

Or, even without additional payload, reducing power to below some critical level will cause the blades to stall and the drone will fall out of the sky.

Propeller blades can be forced to stall during certain flight manoeuvres, no matter how much power is applied to the motors. It has nothing to do with variable pitch propeller blades. It's all about the speed and angle at which the airflow is introduced into the propeller blades.

Do a search on "Vortex Ring State", or check how many people have reported crashing their DJI Avata due to "Yaw Washout".

Of course there is "useless knowledge in the Part 107 test. It's an FAA Exam, HELLO! I have been taking FAA exams most of my adult life. On the other hand, issues like angle-of-attack are important to learn. How about Airfoil icing? Well your basic Quad has 4 sets of airfoils in which ange-of-attack are important, and I have seen video where forum members here have subjected themselves to prop icing, which adversely effects angle-of-attack. Have fun studying.

Now you have me wondering what a Part 61 gets you and why you're got that? Never heard of that before.

What the FAA should do is talk about much more practical stuff that we need to know. They should explain how and why prop icing is an issue. They should talk about emergency power shut offs (like a CRC). They should talk about ADS-B and how to use that (so very useful). They should mention B4YouFly and other useful apps. They should give you the scenario I actually faced in real life (I described above) where a Coast Guard helicopter is flying straight at your drone with no warning - what should you do? In short, they are missing some really important information, and including some not-as-useful information.