Building a Search and Rescue fixed wing platform

[Daniel Baldwin]

New to this forum so - Hello!

I am in the process of building a fixed wing aircraft for a local Search and Rescue group and unfortunately I am a little stuck. Basically I am wondering does anyone have any recommendations for an ESC/Motor/Prop combination? (Just power and sizes will do if you don't have exact product names)

Basically it will have a maximum take off weight of 7kg (This is an utter maximum and I hope to actually have it near to the 5kg mark) and a wingspan of 2-3m. the ESC/Motor/Prop combination needs to be quite efficient as it needs to stay up as long as possible and it also needs to fly quite slow.

I have tried using e-calc to get rough estimations on different setups but now I am completely confused as some results contradict the others.

Any advise would be brilliant, this is my first build from scratch so am starting to feel a little lost!

Thanks!

Dan

[eflightray]

You are asking in the Beginners forum ?, do you have experience of model building, flying RC models, FPV, and possibly UAV ?

The ESC/motor/prop, and 'battery' combination, is only a small part of the overall package.

Is it over land search and rescue ?, what sort of distances, (radio and video link range) ?, size limitations ?, disassemble for transport ?.

There have been a few similar ideas across various RC forums, and rarely heard of again as a complete working system.

There are some commercial models available that could probably do some of the work. A search on FPV models would show you relatively simple FPV models that could be used for aerial viewing. But add poor weather, rain, fog snow etc, and there are limitations.

Not trying too much to put you off, you just need to explain exactly what you want and preferably why.

[Daniel Baldwin]

I asked in the beginners forum because although I have experience flying RC models I don't have any experience building them (I have built a hexcopter but this is my first proper attempt at a fixed wing)

Sorry, I do admit I didn't really put a lot of detail into the initial post, I was only mainly looking for recommendations haha. Here are some more details for you:

- Land only searches

- Maximum of 1km radio and video link range (Although it will be capped to 500m roughly due to UK laws etc)

- In my normal spirit of go big or go home the wingspan is currently at 2.4m and the fuselage is 1.6m so will be a disassemble for transport job (Wings and whole tail remove from the main fuselage for transit)

- Whole thing is made from insulation board and before sanding parts into an aerodynamic shape it weighs in at 2.5kg (Hoping to shave off at least 500g)

- Using an APM board for the autopilot and control

- Basic FPV gear to start with, will also have a digital ground link to the ground station (Cannot remember the link name and currently can't find my list) but it has a tested range of 1.6km

If the system does work and the SAR group give the go ahead to bring it into service I do plan on getting a thermal camera put in with a specialist tracking software (Already sourced and waiting in the wings)

I would go for a RTF model but unfortunately none of them can support the weight of the batteries required and the ones that can start to really bump the project price up. Basically the Search and Rescue group aren't funding this as they really cannot afford to, but at the same time they desperately want to introduce a system like this to aid their searching. So that means I am using my own cash to slowly build the system from the ground up.

I also understand that this is a huge project for a first time RC plane builder but I have the drive to do it and if it doesn't work I will only be a small amount out of pocket rather than spending tonnes on an RTF system...

Thank you for your help, I do have the vast majority of the parts in a list for the rest of the system its just the power plant that I am confused with...

Thanks again!

[Martyn K]

If this is a first design and build, that is a big undertaking. I am not doubting your capability, but I suggest that you consider a kit or plan build of a similar sized model. I imagine that stability is probably of prime importance - have you considered something like a Precedent T240 or similar? This is a well proven design and may be a better fit to your requirement. If you are looking at something that weighs 5-7kg that is serious scope for injury or 3rd party damage if it goes wrong.

Martyn

[Dave Hopkin]

The "standard" yardstick is 100W to the Lb - for a slow floaty airframe you can reduce that down to at least 80W/lb

of course you dont have to use full power

The other question that I would ask, As this is for "search and rescue" its got to have the capability of operating from any sort of terrain - which will mean it probably wont have a nice flat runway to take off from - and 5 to 7kg is a lot of aircraft to hand launch!

It strikes me that there are many multi-rotors that would be ideal for this role and would be more practical up in the hills where winds are going to be highly unpredictable......

[Daniel Baldwin]

I am designing using plans for something like this: http://static1.squarespace.com/static/50d14c75e4b0610fe0ab70db/t/512aa08be4b091ea7fc7e82c/1361748108866/

So I am not going completely blind, as for something going wrong I live in a rural area with tonnes of fields so I plan on testing for a couple of months and getting some flight time in before I take it anywhere near other people/objects. The system will also be running on an autopilot and have fail safe's in place in case the transmitter loses connection/interference/low battery so all of those will be covered.

As for it's size this is a test bed of sorts, I know it will be hard to launch from anything other than flat ground but the idea is to test this size, if I can go smaller then I will reduce the size down more but my fear was to keep scaling up if I went small first. I do agree multi-rotors would be ideal for this role but they are limited by their flight time and the purpose of this is to stay up for roughly an hour or so autonomously scanning while the pilot keeps an eye on it and a spotter watching the screen for targets.

Another way of getting it to take off in a shorter space would be to use a slingshot of sorts and then a parachute to get it to land again after but I haven't had the chance to research this yet.

[Andy Meade]

Any idea what your endurance should be?

Sorry, just saw that you intend to be up for an hour or so. 15lb then, at roughly 100W / lb, gives 1.5kW system.  Have you a target airspeed in mind?  This will narrow down even further the "unknowns", and you can arrive at a prop / motor combo.

Edited By Andy Meade on 06/05/2015 16:48:17

[Daniel Baldwin]

I am hoping to get an hour of flight, again this will be based upon what batteries I need to use based upon a motor/esc/prop setup. roughly 30,000mah total I think, again dependant on how much the motor drains...

[Andy Meade]

6S lipo will give you 22v. Wide open throttle will pull 68 amps then in our 1.5kW system. Up the voltage to give you lower current and extend you 30Ah battery power - 8S for instance will pull 50A.

Don't forget you'll never (intentionally) use all 30Ah from the pack, so aim very conservatively.  Having said that, you'll hopefully never run a full throttle 100% of the time either!

Edited By Andy Meade on 06/05/2015 16:58:30

[Daniel Baldwin]

Just seen your edited post above Andy, I am hoping for as slow as possible really, roughly 15-20mph? Is that do-able in such a large system? Once I know a motor and prop combo I can then work around how much juice it will suck up then tailor what batteries (And how many of them) will be required to meet the hour zone. Thank you for your help so far!

[Dave Hopkin]

I think you need to come at this problem from a different angle - the only parameters we have so far is

Span - 2 to 3 Meters

Weight - Less than 7kg

Desired Stall Speed 15-20 mph

Thats not really enough to work anything out....

Decide on the span and the Chord which will give you wing area and hence wing loading - that is going largely determine your flying speed

Will the airframe restrict the prop diameter? (thinking of a pusher here to keep the FPV camera clear)

When you have a better idea of all up weight then you can decide how much power you need and what voltage you want to operate at - to my thinking you want low voltage to keep current consumption down and endurance up, so start with a 3S set up and see where that takes you?

for me which motor is the last decision I make, the

[Dave Hopkin]

Double post

Edited By Dave Hopkin on 06/05/2015 17:33:31

[Daniel Baldwin]

Once again annual leave brain in gear and not giving the full information... Some more for you:

- Span exactly 2.5m

- Chord Exactly 40cm

- I said weight less than 7kg as I wanted to leave room for more batteries etc, but the realistic weight will be 5kg

So that is roughly 10.66 square ft of wing area (Correct me if that is wrong) so wing loading of 16.54oz per square ft?

 

The prop will be in a pusher format yes, current design limits it up to about 15inches but that can change as needed.

Edited By Daniel Baldwin on 06/05/2015 17:54:23

[Alan Jarvis]

I have one of these which I think will be ideal for your project.

**LINK**

With a couple of 4s batteries I was getting 40 mins flight time. It will carry 2Kg so would easily take more batteries.

Easy to hand launch. I also had an APM in it and FPV but just fly it for fun now.

Look up some of the Youtube videos and FPV sites.

Amazing plane.

[Chris Jones 7]

Surely if you are capping your range at 500-1000m then a multi rotor would be a move appropriate platform? Get something that will carry a huge zoom camera such as the Canon sx50 with its 50x optical zoom, couple that with a remote controller for the camera and you could cover the majority of the area from 400ft (1000ft if you fly FPV). You'd only have to move to see round obstacles.

[Daniel Baldwin]

Chris, The reason I have gone with a fixed wing is the versatility and endurance combined, sometimes it may need to circle one position to guide a ground team into place for half an hour or rapidly remap an area after a flood etc.

Alan, I have looked at the X8 before, but after chucking in a couple of batteries the space inside does start to get cramped doesn't it?

[eflightray]

Consider a twin motor for FPV work, it keeps the props out the camera view, and allows big diameter props.

[Andy Meade]

The problem there Chris is endurance. The wing can at least provide it's own lift but a multi would be very hard pushed to stay up for an hour.

[Dave Hopkin]

Given that wing area (I get 20oz/ft) would give you a stall speed of 24mph

I still think that a multi Rotor that can stop and hover/side slip to look in detail at something would be a far better platform than a fixed wing aircraft that has to keep moving and do a wide U Turn to get back over the suspect area (if you can re-find it that is)

[Andy Meade]

Pretty easy Dave - just put APM into "loiter", and she'll circle straight away. Using a data link and a laptop, you can then just click where the circle needs to be centred.

[Daniel Baldwin]

The main purpose it to quickly scan an area with a thermal camera, it then picks up targets and gives GPS co-ordinates for each to a ground team to check out, while the target is on screen you can then assess if the person is lying down, walking etc or if it is even human. Then once the targets are divided to the ground teams if they require the plane to loiter above to guide them along a correct route the thing will already be in the air waiting to be given somewhere to loiter above. If that makes sense?

[Peter Miller]

I understand that they ran a big competition in Australia for just such a machine, drones etc. Their search range was considerably wider than yours. I thin they said 5 Km

It might pay you to reasearch that competition. I was only told about it by someone who has family out there.

Edited By Peter Miller on 06/05/2015 18:19:08

[Andy Meade]

It's called the Outback Challenge - tis run every year.

Daniel - have you looked at the Lake District SAR people at all? They do this already I think - I was a tester for their software a while back. I don't know what became of it - it was called Aerosee

Edited By Andy Meade on 06/05/2015 18:23:44

[Daniel Baldwin]

The Outback Challenge is where I have been getting the inspiration for this, especially the Canberra team who won it last year.

Just had a look at the Aerosee program and its quite interesting, especially the concept of crowd sourcing the man power to scour the images, Although that isn't ideal out in the field as how you upload video to the internet when in the sticks is going to be difficult.

Don't get me wrong this thing could do a 5km search range but the UK limits you to line of sight (500m) only so 1km area around the pilot basically...

[Don Fry]

Might be thick, but to loiter you need a petrol motor, if you want cheap as well.