I was just commenting on the need to more clearly define the expected outcome and define the plan around that... also that i forgot this was a design you had to "sell" to the JDF AW.. thought it might sound critical so i deleted the post
Well I like critical statements, thats how I enhance my plans.
How do you think the BTR 88 would perform at 1000ft? Any mission at that altittude would be the prelude to a police/military raid or simple anti narcotic scouting missions... So it should be able to spot the movement of men, not clearly defined but clearly enough for the operator to identify humans from non human things. Cars and boats should also be clear from this altitude, another question is whether or not an individual carrying a firearm or anything appearing to be a firearm(assault rifle size not handguns) would be clearly visible from that altitude.
Sounds like an interesting project. Some quick numbers:
Your stall speed expectations might be a little optimistic for the type of airframe you have drawn. By my calcs, with a 7m/23ft wingspan, you'll need and AR of around 9 or less to get your C_L at stall to be anything realistic. At 9 the C_L is 1.26 at at 25km/h sea level stall. Possible, but you'll have to work your aerofoil sections well to get it without compromising top speed. That's a MAC of around 0..8m, by the way.
My gut feel is that you might struggle to get such a large wing area down to the weight you need (25lb empty) and still make it robust enough for mainstream use. Certainly a challenge for you.
Also I calculate a 100km operational radius with 2hr loiter and reserves will be about 7-8L of fuel, depending on your engine and other assumptions.
Anyway, it's an interesting project. Good luck with it and I'd be happy to do some more modelling for you if the project gets legs.
Thanks for your input Andrew. We will eventually revise the stats we have as well go along... I am hoping to get the cad available so that you guys can have a look at it.
What would a live video from a 720p hd camera at 500ft travelling at 30kph look like?
Any idea of how legible it may be when it comes to making out humans?
I have seen several videos but none with information on altitude etc to get a clear idea of what it may be like.
Flaps on the leading edge??? Wings don't work that way. (Unless you want to land really, really fast) The ailerons would be a lot more efficient further outboard.
An 8HP engine weighing only 5-pounds? (Electric or gas?) Leaves only 20-pounds for the air frame, propeller and fuel (gas or battery). An air frame that can carry your payload and withstand the aerodynamic pressures at 100 kph (knots - kph, or kilometers - kmph?) is going to weigh more than 25 pounds. A 100 km range is going to need a lot of fuel. Batteries (or gas) sufficient for 100 km alone will weigh more than 25 pounds.
And transmitting a video signal 100 km is going to require a satellite or cellphone link.
12,000 ft ceiling? You do realize that the air is pretty thin at 12,000 ft.? A fixed-pitch prop that works efficiently at low altitudes will barely produce thrust at 12,000 ft.
And transmitting a video signal 100 km is going to require a satellite or cellphone link.
I suspect that you need to rethink your design specifications.
The flaps are for quick landing incase an improvised runway is needed which in this case would be a road and Jamaica roads arent usually straight for great distances.
The engine is gas http://www.hobbyking.com/hobbyking/store/__22755__DJ_80cc_Gas_engin...
he made a mistake there with the weight it should be 1790g and not 1790kg, the youtube video here http://www.youtube.com/watch?v=ZGH-AE4frI0
engine is 8.2hp and weighs 4.2 pounds.
Thanks for your note both about the weight and the ceiling. The aircraft should be atleast several hundred feet higher than the blue mountain peak where people tend to get lost from time to time. As I said however the specs will continue to change as we gather more information, those however are our preliminary targets with the range and the endurance being the most important targets to reach, thus everything will be developed around them as the craft develops.
Video transmitting at that distance will indeed require the island's celular network, I was speaking to one of the managers of the largest telecom company here(digicel) two years ago about this. Because of how this project will develop getting the required access will not be a problem.
Your gas engine will need an electronic fuel injection system to allow operation at the altitude you're proposing. I'd also suggest that such a large single-cylinder engine will give you vibration problems which will always be a headache. I'd suggest looking at a similar power multi-cylinder engine. While slightly heavier, a boxer twin will at least give you some significant advantages on vibration minimization.
Regarding your data link, real time HD will be unlikely over conventional civilian data links.
As far as designing your airframe, I'd leave that till later. The optimal airframe will become more obvious when you have nailed your specification requirements in terms of range, payload, speeds, operational infrastructure etc.
Thanks again for your analysis.
I managed to track down the engine I first came across a month back, could not find the name but this morning I managed to find the PDF on my PC.
this is a 10.72hp variant, dual cylinders and weigh 6.72 pounds
I have actually made alot of revisions because of the suggestion of you guys. The datalink will have to be worked out over time with the requisite personnel here in Jamaica.
A few thoughts- If you are able to do a control station or two on the mountain tops, you will have better LOS for control, as when the bird goes down to 500ft, LOS links can get dicey. There are also fresnel effects for radio point to point links, so while it make look like it'll be okay, you may get some unpleasant surprises in practice, Particularly with the terrain you've got (had no idea that it was so mountainous there!). Having cellular links should help a lot, depending on your network saturation, and available backhaul speed.
While surveillance footage can be cellular linked, if you plan to do any FPV at all, you'll need a direct link back to your control point due to potential lag issues. Even a fraction of a second (which easily can build up with a digital data stream of video over a cell network, then to whatever handoff you're using to look at it) will render the system basically unflyable by hand. (I happen to be both a pilot and an network engineer, so I spend too much time thinking about these things). Even if it works most of the time, it's too non-deterministic to count on, particularly if there's a serious emergency.
On the plus side, an independent link doesn't have to be HD for FPV control, reducing the cost and increasing functional range on the long p2p link. (you would have two cameras, SD forward facing for FPV and HD gimbaled below for SAR.)
If you are comfortable being 100% reliant on your AP, then it's possibly a non-issue, but given the size of the bird, well, I'd want the option of doing FPV, and at least monitor it, particularly while tuning your waypoints for terrain.
Since Blue mountain peak is about 7200ft, I might optimize for a 8000Ft cruise altitude, as that gets you most of what you want from cruise and your higher elevation SAR missions, any more than that and you have to start making a lot of compromises (and you've already got plenty on your plate). Your max ceiling will be higher, but it's basically useless to go any higher than around 8000-8500ft practically speaking. The additional speed is a minor gain, and by lowering your ceiling you can gain performance in other areas while maintaining simplicity. Also keep in mind that your ground speed will be much higher at 8000ft, which will make it more difficult for camera work.
EFI for the engine is a good idea, but it's not required. An altitude carb (i.e. bing) can do the job, but if it were me, I'd go EFI. Fuel is expensive, and EFI is better (once tuned) at minimizing burn rates with varying altitude. I also second the two cylinder minimum for an aircraft engine, vibration is the enemy, and you will save weight on the motor mount with more frequent power pulses than one big one. And there's the camera shake issues as well.
Another consideration is going electric, as batteries get better and better. Huge advantage with less vibration, and it's a bit less altitude sensitive (although prop selection is still a careful choice, the same motor power is available at all altitudes).
The question is if you can get the range and duration you want with it, particularly with your payload requirements. Depending on your time scale you may want to keep an eye on battery power density, as it's steadily increasing to the point where it is a good alternative, even for a bird of this size.
Really look forward to see how this progresses.
And maybe the wife and I need to go to Jamaica... Hmm...
Thanks for your input Jay Bryon. I prefer going with a gas engine because of the size of the craft I am looking at. As I said though range and loiter time as well as stall speed are the most crucial variables now, the others can all change(those are the criterias the JDF Cheif had set).
Your visit here is always welcomed :)
I will get a modified design taking into consideration all the advice i recieved here by weekend.
So look out for that
Given this project scope you'd be far better going for an existing commerical UAV solution and adapting to your operational needs (which almost all suppliers would work with you to do). Your requirements meet (most of) the capabilities of the Aerosonde. I'm not sure what pricing on a new Mk4.7 is (older versions were around 25-35k US).
Having worked in UAV development I can say that you want to avoid, at all costs, the task of developing your own application specific craft (at this scope). While off-the-shelf technology has come a long way in the past 20 years, developing a fully functional, robust and reliable system is still not something you can do without a lot of in-house expertise and experience in this field. Hobby-scale systems and experience just wont cut if for what you want to do.
Thanks for your input Tim.
Buying a drone will defeat one of the key points however: indigenous development. Local producing the system would be aignificant boost to our local science community but would also afford us a window into the technology into the future as well as give us bragging rights among the carribean. All of our equipments whether civil or military is purchased; the V150 commando car for example is an old dustbin but we still purchase them, why not purchase the rights(its so old I guess the patents have mostly or wholely expired) and manufacture it here? it would not only be cost effective but will create jobs and give us a little knowledge in manufacturing vehicles like that. We already have a car manufacturer here who builds 4x4 vehicles locally, however the company hardly gets any local support even though the vehicles are of high quality and there are overseas buyers anxious to get their hands on them... add to that the company cannot manufacture them fast enough to satisfy demand.
We have scientists here who are working on improving a sonar type system for search and rescue, working on designing better wind turbines etc. So we do have the tech base to take on a project like this, the challenges will be there but those challenges are what is going to put us on path for better systems in the future.
Add to that the fact that purchasing an external drone will be difficult to pass here locally because of budget cuts. A locally produced type grabs the eyes of the persons in government simply because it can be ceased upon and used to build national pride and confidence in their governance, plus the scientific knowledge that would be gained is priceless.