Hi the idea here is to come up with a new UAV specific airframe design for the DIY community. Seeing that the AP's are rapidly improving and are cost effective for DIY we have no Airframe to match. We need something with Ailerons to start with, its the only way to fly properly and prevent nasties. A Pod design may be the most flexible as they can be interchanged, also if positioned at the CG it will help to keep the airframe light and reduce CG problems with differing Pods/Payloads.

We need some new standards for form factor for the AP and Payload to ease the pain of design and prevent the issues with adapting other designs. To start the ball rolling a few ideas below:

UAV specific design, long term platform
Cost effective, not cheap
Airframe with Rx, AP, Batt
Pod for payload/AP (Interchangeable for different missions/payloads) with own power
Pod design to form factor & Volume (maybe different Pod designs for same Airframe)
New AP form factor (standardization) for mounting and space utilization

Max Payload
Max weight to conform to legislation, also max speed
Duration, batt size & motor
Airframe weight (lower means more payload)
Pod vibration isolation
Sensor vibration isolation
Sensor mounting points on airframe with wire pathways to ease installation & attachment
Pod electrical connector or means to electrically connect to Airframe
Pitot tube and/or AoA sensor build in, baro sensor position
Wheeled or not
Land and stall speed
Gimball for camera and other sensors


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Different countries have rules with different impact on the design of the DIY UAV (Airframe impact only):

Max speed 87 knots, 44.8m/s, 161kmh
All sUAS operated under this regulation must be colored with a high-contrast scheme
capability to descend 50 feet within five seconds
If operating greater than 400’ AGL all sUAS weighing over 4.4 lbs (2 kilograms (kgs)) must have the capability to display position and altitude information to the PIC
Cat I < 4.4 lbs (2 kgs) Must not be capable of exceeding more than 30 knots calibrated airspeed at full
power in level flight. Constructed in a frangible manner.

Cat II < 4.4 lbs (2 kgs) Gross take-off weight equal to or less than 4.4 lbs (2 kgs) including fuel, batteries,
and payload. Capable of less than 60 knots calibrated airspeed at full power in level flight. Cruise speed of less than 40 knots in level flight.

Cat III < 19.8 lbs (9 kgs) Gross take-off weight equal to or less than 19.8 lbs (9 kgs) including fuel, batteries, and payload. The sUAS must be capable of providing position and altitude data to the PIC. Aviation Band Radio: If operating within 5 NM of a non-towered airport, a qualified visual observer involved with the operation must monitor UNICOM or CTAF and announce sUAS activity on the frequency of the closest airport consistent with applicable procedures.
All Group III sUAS operating beneath
the floor of the lateral limits of Class C or B airspace, or within the Mode C veil, must be equipped and operate an electronic positioning reporting system consistent with 14 CFR 91.215 or acceptable to the Administrator.

Cat IV < 55 lbs (25 kgs) Group IV sUAS are the largest sUAS permitted to operate under this regulation. Because of
their large size, their operation is restricted to extremely remote areas that pose minimal
perceived risk to those on the surface. The PIC must obtain a Letter of Authorization (LOA) from the FAA verifying that
the planned area of operation can be considered uninhabited and extremely remote.

Light UAS with maximum take-off mass of less than 150 kg
Max 70 knots, 36m/s, 130 kmh
Has an impact kinetic energy that does not exceed 95 kJ when assessed against both a high speed and free-fall impact scenario, and which is calculated as follows - i. Kinetic energy = 0.5*Max. Operating Mass*(1.4 * Max. Level Speed) and Kinetic energy resulting at impact from a free fall from a height of 400 ft.

Any EU info available please post here.
Any other countries with information regarding Airframe restrictions, kindly add it to this. We need to come up with two designs it seems, a small one (2kg, 4.4lbs) and a bigger one ??kg.
Just some thoughts to start off with:

So logically we need to start not with the airframe but with the mission. As we know we cannot fly outside LOS so distance is not an issue, maybe a number of laps (loiter) may make up distance. On the small airframe battry capacity and energy consumption will be the limit. On a larger airframe there is more space for "fuel", also a larger payload of say 2-3kg for a range of say 50Km.

Stability of the airframe is important, maybe slow flying as well. How to fly such a small wing slow? What is the practical limit in still air for slow flying?

Hi Mark,

Thank you for responding on this. Most of this community is focused on DIY UAV's. Getting beyond Cat II will be stretching it for most of us. For the rest you are right, Cat III will do nicely. The budgets is always out of own pocket, hence Chris and teams target of getting an AP system below $ 100.

Me thinks that we need 2 airframes, the more popular one is the Cat 2 version as most RC flyers can afford this. The airframe will have to compete with things like the adapted EasyStar and other, price and performance wise as well as being a compellingly better airframe for our needs.

The bigger craft can be different a it may well be for a different market and requirements. What are your requirments for an airframe?

Another thing to consider is the transportability of the airframe, for most of us we need to haul this stuff in a car, some may have a van or pickup, so easy breakdown and quick assembly is really important.

The missions will also vary, some may want to use it to win future DIYDrones competitions with it ;) and other people that may not be part of this community may also want to use it for even more different missions.

Used the calculator here: http://www.barnardmicrosystems.com/UAV_analysis_V1.htm to get a rough estimate. Its only averages but gives an acceptable answer to some vital performance criteria:

Plugged in the following for Small UAV:

Range 5km
Take off Weight 2kg
Fuel (Batt) 0
Endurance speed: 80kmh
Wingspan 1.358m
length 0.765m
airframe 1.111kg
Payload 0.712kg

Plugged in the following for Large UAV:

Range 50km
Take off Weight 9kg
Fuel (Batt) 0
Endurance speed: 80kmh
Wingspan 2.415m
length 1.361m
airframe 4.671kg
Payload 3.614kg
I think sub 7kg is what is going to get the green light easiest just about everywhere, the materials the aircraft are made of are important.

SPAD designs from estate agent sign boards get my vote.

Your absolutely right though Sarel, there should be a group airframe to go with the group autopilot.

I wonder what the most available motor and battery combo is around the world as well.

If the Ardu was up to it I would vote flying wing, in fact I would ask Jaron if his design could be the defacto standard, its very pretty.

Have to give the more standard airframe a little more thought.

Hi Sarel

I would also like to see a standard Airframe be developed. Something like the ScanEagle.

Just a remark on your calculations from above. The calculator above's speed input is knots... Not Km.. So the 60 you entered is actually 111km/h and 80knots = 148 km/h.

I do believe that is a little bit to fast for DIY needs (More like semi Pilon racing) I'm in the works of finishing my cnc-foam cutter so will be pumping out UAV molds soon after. : )

Kind Regards
Hi Gerrit,

Did do a double check on that calculator, its all metric, so the speed is indeed kph. And both of them was at 80 kph.

Everybody seems to have a pet airframe :) and that's good. What we should be doing is not hit each other over the head with the airframes but agree on some criteria and then solve with that for an airframe design or two.

Lets get the dimensions, weights, speeds, standards and other engineering stuff done first for a universal open airframe. Each individual can then decide what materials to use where.

We need the basics like Pod internal volume and dimensions pinned down, type of equipment and weight most likely to be used, power budget to calculate duration to keep the Pod alive and propulsion requirement as well as duration for the aircraft.

It is kind of getting the cart in front of the horses to select an open source airframe and trying to adapt it to one persons requirements, this is what we have been doing all along until now. The other way round surely is what we should be doing to create an open standard suitable to a community.

Hope this serves to state the intention more clearly.

I really like your idea about an open source UAV/airframe Sarel. In my view, such an airframe would preferably be of a modular consept - allowing for various adoptations. I also think it is a good idea to start with the requirements - and secondly select the airframe which fits best.

As a matter of fact, I started a similar thread at RCGroups earlier this year:

This project came to a temporary hold (due to various wife-initiated activities, rebuilding of kitchen etc), but I was planning to commence on the project this winter.

Looking forward to follow your project.

Hi Jorn,

Thank you, had a read and some nice ideas there. The idea here is to design the airframe from scratch, make it as easy to build/reproduce as an EasyStar of some such. Foam or a SPAD type construction seems to be the easiest. The Pod however will have to be made with a frame and covering me thinks, that will give the least weight and best volume/strength.

Any ideas on the possible missions we need to do?

Maybe the most important task at this stage will be to decide on how to organize, structure and coordinate the work. How to describe the project, design-tools etc. Besides that, some of the steps might be to:
- decide on a set of basic requirements,
- decide on a "type" of airframe,
- roughly outline the ideas, make some simple sketches,
- split work in sub-tasks, ...


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