Yep, delivery drones and larger industrial drones would really benefit from these.
Ice on leading edges of propellers?
- Thread starter VibeFixer
- Start date
Your statement is not quite correct. Ice does not simply form in clouds. Clouds are often at different temps and different amounts of total moisture. Ice only forms when the dew point and the ambient temp are close or exactly the same. That is why ice can form at other times of the year, not, as most people think, only in the winter.
I have an open cockpit aircraft and over the years have flown through or skirted many different clouds during a flight. Just a few seconds through an edge of a cloud has produced icing on my goggles, to nothing at all, to total saturation that makes it feel like I slept outside all night and the morning dew soaked me.
In an open cockpit, you can actually feel what the cloud is made up of and it is surprising to see how wet, dry or icy a cloud can be. As for it always being colder up there, than where you stand, as you put it, that is also incorrect. You can often have temperature inversions in the sky. Many times in summer as the evening encroaches, it can be a nice moist warmth up there and as you start your descent, you suddenly feel the different colder layers of air as you approach the ground.
I have been flying in Colorado in winter where the runway altitude was 8,200ft and it was icy cold and about 800-1,200ft or so up, the air became so warm that I could take of my gloves within that band of trapped warm air. It is amazing what you can feel when flying in an open cockpit aircraft, you experience far more of what nature offers than you would never know about if you were in an enclosed cockpit like a Cessna 172, for example.
Far too complicated for that type of drone use. Ice is not a constant worry, just because the air is cold. If it wasn't for heated carb intakes, you would have far more aircraft suffering from engine failure, due to carb icing, than you would have wings and props icing over, each year.
For those that aren't aware, icing conditions only appear at certain altitudes, it is not a case of if icing conditions prevail, that the entire sky will be in icing conditions. When you fly, for example in a manned aircraft, and encounter icing conditions, a simple altitude change, either higher or lower will generally get you out of those icing conditions. The drier the air, the less likely you will encounter icing conditions.
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Well, icing can occur at any altitude. If that altitude is near 400' or lower it's not like a drone pilot can climb to 6,000' to get out of it. The OP was in clouds, so there was plenty of moisture.
Sure icing conditions are usually in blocks from 1 to 3,000' and a manned AC pilot can escape that, but a drone pilot can't.
Oh, I have no doubt that such a thing is being researched, it's just that such an application for our little drones is not in the immediate future. I'm sure that one day we might see this available for us to purchase, though it will compromise performance and battery life per flight. With that said, we don't have to fly, therefore, if conditions on the day are looking like icing may occur, simply keep your drone home and wait for another day to fly.
I was not suggesting that a drone pilot could climb to altitude to avoid it, I was educating readers who may think the entire sky will be in an icing condition when people speak of icing. Icing can occur anywhere, in theory, though it is rarely encounter at high altitude.
Our 400ft window will have icing conditions from time to time, however, such conditions are far less likely to be encountered than non-icing conditions, throughout a year's flying. Therefore, it is not something that we should all be deeply concerned about.
But be aware of... & know when it can occur & what the signs of the condition looks like. Furthermore the condition is in some sense photogenic, so it can make flyers go airborne in a higher degree.
That's true. Our drone props are small in diameter. I was referring to larger industrial drones that have larger props since larger props are more susceptible to icing.
Prop material (carbon fiber, e.g.) is important as well and we will probably see more industrial drones go that direction to avoid icing. I'm a retired engineer so excuse my nerdiness please.
AMann
Well-Known Member
I wonder as the pressure drops on the top of a spinning blade if it can cause the same situation by slightly cooling the air - notice in some photos of it how ice forms on the leading edge and over the top of the blade? As the air is compressed under the blade, it may be warmer and less likely to ice up (unless the ambient temp is very low).
Um, no. Close, but not exactly.
Yes, exactly!
We talked about precisely this last week in another thread:
mavicpilots.com/threads/is-anyone-else-nervous-about-flying-in-very-high-humidity.134234/
The critical factor is the % relative humidity. People seem to think that cold air is drier than warm wet tropical air, and they're correct, sort of. That's because warm air can hold a greater quantity of moisture than cold. But that's not what matters. The only thing that matters is the % relative humidity, and how that changes with pressure/temperature.
That is a measure of how much moisture can be absorbed into the air at that particular temperature/pressure. You can have 99% relative humidity in either arctic cold or tropic heat. But if it reaches 100% (dew point) in either case, condensation will form. If it's above freezing that's fog. Below freezing it's ice.
There are a few ways the relative humidity can be tipped from 99% to 100%.
- too much moisture is absorbed into the air from a body of water, or
- the air temperature is decreased, or
- the air pressure is decreased.
If you run an engine with the throttle plate partially open, there is a huge pressure drop from ambient pressure to manifold vacuum across the throttle plate opening. A sudden pressure drop results in a sudden temperature drop. Even if the ambient temperature is well above freezing, the throttle body temps may see well below freezing. The outside ambient % relative humidity may be well below dew point, but the pressure/temp drop across the throttle plate may drive the relative humidity above 100% dewpoint humidity within the throttle body. If the drop in temperature is significant enough, you get throttle icing.
The same thing can happen on the low pressure upper surface of the leading edges of aircraft wings and propeller blades. The ambient air temp/pressure/% relative humidity conditions may not even be near freezing or near dew point. But, if the temp/pressure drop over the low pressure surfaces of the aircraft is big enough, it may create local conditions exceeding the 100% relative humidity dew point.
And, if that temp/pressure drop is significant enough, it can cause the resultant moisture deposits to freeze.
That's why, when conditions are right, you'll see ice forming first on the upper leading edge of propeller blades. Long before the extra weight or any potential imbalance is ever noticed, the biggest danger is that the ice buildup disturbs the laminar airflow over the prop's surface. That causes the blade to stall, losing lift.
Just in on one of our other forums.
yuneecpilots.com
yuneec typhoon q500 control board
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yuneecpilots.com
Can a quadcopter really stall due to exceeding the angle of attack during a manoeuvre? I've never heard of an aerodynamic stall in a rotorcraft _ but stand to be corrected if others know of this.
Kilrah
Well-Known Member
It happens when the props get fed turbulent/already disturbed air but that's about it (in normal conditions, excluding icing).
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There are limits built into the firmware for the flight controller that prevent that situation, but with enough icing on the props the loss of lift at those built in limits can cause a stall.
Unlike a helicopter a quad cannot autorotate to a landing.
What @DoomMeister said.
Also keep in mind that those spinning blades are wings, so yes they can stall.
Also keep in mind that those spinning blades are wings, so yes they can stall.
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