votingprawn

Tabs are a way to reduce the amount of stick force (i.e. force applied by the pilot) required to deflect a control surface in a mechanically linked system. In most modern aircraft hydraulic or electric systems fill the same purpose

To give a simplified explanation, a small tab located at the trailing edge of the surface is deflected by the control linkage. The deflection of the tab generates an aerodynamic force which then creates a moment around the control surface hinge, moving the entire surface.

So if you deflect the tab upwards, that air flow over the tab generates a downwards force that acts to move the control surface down.

I built a system a few years ago as part of my undergraduate degree that could localise aircraft using microphone arrays and acoustic beam forming. My primary sources for information were books on SONAR.

The system worked in real time but also stored all the raw data so it could be processed again later if you wanted. I also had some fun trying to identify the aircraft based on frequency content and details on engine speeds / blade counts from Type Certificates.

Some types of SONAR send out sound, other types (e.g. [0]) passively listen for sounds and use beamforming to localise the source of the noise.

[0] https://en.wikipedia.org/wiki/Towed_array_sonar

Yes it is. Despite all the other replies asserting SONAR is active, passive SONAR systems are very much a thing.

For my undergraduate project years ago I built a microphone array that could be used to locate noisy objects. I demonstrated it by tracking aircraft taking off at a local airport.

Whilst I didn't make 'acoustic photos' with it, I did plot the flight track of the aircraft in real time, and could have a decent crack at identifying it based on frequency content.

Years ago I started coding qbasic with a photocopy of a book given to me by a friend of the family.

I progressed from there to medicore competency in PHP, rails, and c++. Then I went to university to study comp Sci...but almost immediately switched to aerospace engineering, and my coding skills plateaued.

By that I mean I can write basic stuff in all sorts of languages, but I'm miles away from writing a compete program or anything user friendly. Most of my code these days revolves around automating various things in the most sensible language. Where sensible often means something the next non-coding engineer to come along can understand.

I guess I stopped because I knew enough to do what I currently need to do. I'm content that, given time, I could learn to be a better coder. But at the same time I avoid jobs in my industry that are suited to decent coders because I know there are more suitable people for the role.

Every so often try to pick up some "hobby coding" but find that I don't really enjoy it like I did as a teenager.

> In reality, Tesla is doing you a favor by making their body panels so expensive because that means it's easier for your car to get declared a total write off in an accident and you can get a new car

I think the chance of getting new value for your totalled car is pretty slim, unless it was written off in the first year or you're paying extra for GAP insurance.

My car got written off by an insurance company last year after someone drove into me. I ended up taking a settlement and getting the car fixed myself, there was no way their write off settlement would by me anything like the car I was about to lose. I also hate "throwing away" something mechanically sound over a few body panels, some panel beating, and some paint. And it is certainly not the 'green' choice either!

> Does that matter?

No, but when someone alludes to something without saying what it is, curiosity is aroused in people.

Oddly enough accelerating like that isn't always "legal". Where I'm from it could be classed as dangerous driving, and I believe in the USA it could fall under "Exhibition of Speed".

By and large it is more efficient to accelerate at full power, assuming your goal is to reach a certain top speed regardless, so if you were _really_ concerned about conserving petrol then you should be going full blast off the line. That said I expect the fuel usage such a situation to be negligible anyway, especially to someone who can afford/justify a car that does it in 4 seconds.

My car isn't that fast, or particularly economical, but I know I've never thought "I'd love to accelerate at full power here to show how fast my car is, but I just can't justify the pennies it will cost me"! Outside of hyper-milers I wonder how many people do actually think about it.

Do you accelerate at 100% each time though? I dont think I ever floor my car "off the line", I think I only use maximum power to go from 60-80 on the motorway.

The effectiveness of a UV lamp decreases with age, so they can stop being effective long before they actually burn out. There should be a manufacturer rating on the lamp, which will depend on its composition and other things.

As an example the lamps I use have a rating of ~8000hrs, about a year, but to the outside observer they'll still look functional until they blow after 2-3 years.

Admittedly my last interaction with the NHS was three years ago, but the GP had to go away and research what to do. I have no problem with that, they can't be expected to know everything offhand! The human mind is a complex thing.

My own hangups make it difficult as I find the whole thing hard to talk about. I have no reason to complain in the grand scheme of things, "Some people have real problems!"

> Get checked and officially diagnosed.

That can be a surprisingly difficult process.

For example the NHS isn't entirely sure how to diagnose ADHD in adults. My GP didn't even know it was possible, and had to go and make phone calls to find out where the nearest specialist was. Unfortunately if your answer to "Did you get bad grades at school?" is "Not really" then hard luck, as they want evidence of underachievement as a kid to confirm the diagnosis. And there really is no way to complain your above average grades were underachievement without sounding like a dick.

It wasn't until I was in the final stage of my degree that somebody noticed that I had problems, and luckily the University helped me get a private diagnosis for some of my issues.

Are you talking Cloud Cap style turret gimbals? If so I'd be interesting in hearing more, as we're always on the hunt for more payloads for our larger (20kg) fixed wing aircraft.

> or directly contacting the surface with an instrument

This is more challenging than you might initially think, as conventional multirotors can't easily generate the forces you need to place a tool/sensor against a vertical structure.

> At 10000ft, pressure is around 30kpa.

Do you mind if I ask where you are getting that pressure value from?

The ICAO Standard Atmosphere gives a value of 70kPa for 10,000ft.

One of my colleagues has done some investigations into the effect of density on multirotor performance before.

I don't have time to run the model for this specific case, but from a similar case with a lower air density of 0.71kg/m^2 (40c at 4km altitude) a simple quad uses ~20% more power in a stationary hover than at sea level.

Interestingly at high flight speeds (15-20m/s) you could actually start to see power savings at this altitude, as the parasitic drag of the vehicle body is reduced.

Well I gave a payload (gopro, 350-400grams with gimbal) and a duration (10 minutes), I'm not sure what else to say! The aircraft was completely controllable with no memorable handling differences apart from a very slightly reduced response to high thrust demands, but as we fly our platforms for stability rather than speed it wasn't something that we really noticed.

> 10,000 ft has to be above or near the "service ceiling" of what a quad copter is even capable of. As altitude increases, air density decreases.

Its "only" a 25% reduction in density, you can still get a fair amount of flying done at that altitude. My colleagues have been to Ecuador twice for field work and had no issues flying quads in Quito (9,300ft), no need to change control gains or anything like that. So I know its perfectly possible.

Apologies, your phrasing "make it to that altitude" made me think otherwise!

Multi-rotors using BLDC motors cannot really be compared to small general aviation aircraft with infernal combustion engines.

"Reasonable duration" is a nebulous phrase. Some of the airframe configurations we use here couldn't manage more than about 10 minutes at 100ft, whereas others could quite happily carry a gopro at 10,000ft for 10 minutes (assuming it didn't have to climb from sea level!)

The Falcon Heavy can take 21 tons to GTO, but for $90 million you can only take 6.4 tons.

I.e. 21 tons is the max payload, and the guide price they're giving is just for 6.5 tons.

There is some confusion in this particular case stemming from the difference between altitude above sea level and above ground level.

The UAV in question was spotted at ~10,000ft above sea level, but it was only about 800-900ft above the local ground level at the time.

And also numerous rivers with sinuosity < 1, i.e. the river is shorter than the straight line distance between the source and mouth.

If most motorway/a-road network have "average speed cameras liberally placed" along them as you and maccard claim, then presumably us driving different roads on different days would make no difference? Of course we might just have very different definitions of liberally!

> In my experience driving in the U.K, most of the major roads (motorways/dual carriageways)have average speed cameras liberally placed on the road.

Most major roads definitely do _not_ have average speed cameras placed liberally along them. The only average speed cameras I can recall encountering are at roadworks sites (a move I 100% support) and along a couple of more scenic A-roads that are particularly enjoyable to drive along at high speed.

There are plans to introduce more average speed cameras on the new managed motorways, but I feel it is incorrect to claim they are liberally placed along most major roads.

> because far more efficient electrical heaters

How are you defining efficiency here?

Efficiency is usually defined as (useful power out)/(power in), and basically all the power that goes into a computer comes out again as heat, which in this case is considered useful. Not really convinced you could buy a heater that was measurably more efficient.

ETA: heat pump would do it, didn't spring to mind when I read heater though!

> Probably not, as it will refuse to work at both the altitude and speed of an airplane ;-)

Well sub in the garmin with one of the other low cost consumer units that work at those altitude and speeds then!

>The media and authorities' reactions do not make this action irresponsible.

It is irresponsible because they are flying a dangerous vehicle in an area where if they lost control they could cause harm to members of the public. And they are doing so under conditions that make harder to maintain clear line of sight to the vehicle, increasing the chance of them losing control.

> This isn't a highly populated area. There is little chance that if this drone fell at any time it would hit someone or land in a street.

Only if you consider the only failure mode to be a descent straight down. These 'consumer' multirotors do have a nasty habit of buggering off in random directions when they feel like it: https://www.youtube.com/results?search_query=dji+flyaway

> And what's wrong with night time?

Maintaining line of sight with the vehicle becomes very difficult when its dark. In some jurisdictions the law actually makes no reference to it being daytime or night-time, only that you able to maintain direct unaided line of sight with the vehicle.

When you're in control of what is essentially a 1-2kg flying blender, it is your responsibility to err on the side of caution. Just like when you operate any other device which could significantly harm another.

> You could make many of these bogus arguments about a variety of new technologies ... maybe cars should only be driven during the day?

You'll probably find laws and rules already exist to protect the public from other new technologies. Take cars for example:

- You must be qualified by a government body to use them. - The car must be certified as safe to use on the road, and routinely checked. - You may only use them in specific segregated areas. - You must be able to maintain control over the car at all times. - At night your car must be well lit and must provide you with enough light to see what you are doing. - If you do something stupid/dangerous with your car you are punished.

Yep, although as I understand it they've worked so hard on it since the Kickstarter I'm not sure how much is still recognisable as the core ETH code. At the very least their software is rooted firmly in the PX4/Lorenz design ethos. One of the guys behind the project is also the author of some very nice PX4 and MAVLink tools which you may well have used: https://github.com/DrTon

[we have a nightmare at work trying to distinguish between original PX4FMU running PX4, Pixhawks running PX4, and Pixhawks running APM codebase in conversations]

Unless they've had a massive and sudden change of heart, Airdog is based on the PX4/NuttX stack, not on the APM:Copter.