UAV Propulsion Tech Blog page 3

UAV Propulsion Tech – Post #10 – US Commercial Drone Conferences

Blog #10

US Commercial Drone Conferences:

My UAV experience has mainly been with defense applications but I am trying to also market my products and services into the commercial drone market (agriculture, police, oil/gas, utilities, etc.).  I did a blog post in May on AUVSI which has to be the largest UAV conference in the world.  I attend and exhibit at this event (for the last 10+ years) with the global companies I represent here in the US but it has a stronger defense focus than commercial (although they are getting more commercial exhibitors).  Every other day I am getting emails about new commercial drone conferences in the US.  I thought I would summarize these and provide links if you want to get more info.  I am trying to figure out which one I should exhibit UAV Propulsion Tech at this year to market engines, servo’s, autopilots and parachutes for the commercial market.  I haven’t made a decision yet.

Here is the summary I put together.  Let me know if I missed any:

  • Ohio UAS Conference – Dayton, OH – AUG 25, 26 – Quite a few exhibitors with several defense companies. $2200 for 10’x10′ booth and 2 passes
  • InterDrone – The International Drone Conference & Expo – Las Vegas, NV – SEP 9-11. It says it is the largest commercial drone show in North America but it seems everyone is claiming this. They also only note 80 exhibitors so seems small for the “largest”. $2995 for 10’x10′ exhibit package.
  • UAS Summit & Expo – Grand Forks, ND – SEP 21-23. This one is interesting because there is a UAS test site in Grand Forks so there is a big UAV focus. Also, several defense contractors have or will be setting up offices here. It will have both military and commercial focus (including agriculture). $1,695 for 10’x10′ exhibit package but not many exhibitors.
  • Commercial UAV Expo – Las Vegas, OCT 5-7. This one looks pretty good because there are some UAV companies and some of my competitors. $2150 for 10’x10′ exhibit package.
  • Drone World Expo – San Jose, CA – NOV 17-18. $3,495 for 10’x10′ exhibit package.  Commercial UAV focus (photography and agriculture).
  • UAS TAAC – Santa Anna Pueblo, NM – DEC 7-10. Commercial and defense focused. $1000 for 8×10 booth plus you have to register $700.
  • International Drone Expo – Los Angeles, CA- DEC 11-12. The one also looks good with over 125 exhibitors. This group is also supported by the Tesla Foundation. You can read more about this at: $2100 exhibit package for 10’x10′.
  • Unmanned Systems Institute 2015 Conference – San Diego, CA – DEC 14-15. Appears to be more government and academic focused. Least expensive exhibit package is $4,000 for 10’x10′ with two attendee passes.

 Key UAV News for the Week:

Industry Events for July:

Quote for the week:

“The problem with competition is that it takes away the requirement to set your own path, to invent your own method, to find a new way.” – Seth Godin.

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UAV Propulsion Tech – Post #9 – What’s under the Cowling

Cowling #9

What’s Under the Cowling:

I thought I would do a post on propulsion systems in the public domain that are flying on several UAV’s today.  My focus for this post will be on UAV’s utilizing Hirth engines because all this info has been presented in some manner already in public forums (websites, trade shows, articles, etc.).  There are a couple good UAV resources that also gives details on the propulsion systems for the global UAV market.  These are:

Hirth 2-Stroke engines are designed and produced in Germany just outside of Stuttgart.  The company has been in business over 80 years and produces high end engines that are used in applications where lightweight power solutions are required with high reliability.  The engines are used on several consumer applications (as shown below) and they are also used on high end UAV applications which will be detailed further below in this blog.

Hirth Consumer Products

Figure 1 – Hirth consumer product applications


New Hirth COTS

 Figure 2 – Hirth UAV Engine Family (8hp to 100hp).



Figure 3 – Hirth 4102 8hp EFI gasoline engine – EMT Luna UAV



Figure 4 – Hirth 4102 8hp EFI Gasoline engine  – Drontech UAV AV1 Albatross



Figure 5 – Hirth S1212 15hp EFI gasoline – Northrop Grumman Bat UAV



Figure 6 – Hirth F33 NG 28hp EFI gasoline – Robot Aviation Aerobot



Figure 7 – Hirth 3401 50hp – Ruag Ranger UAV



Figure 8 – Hirth modified F23 50hp EFI engine – IDS’s SD-150 Hero UAV



Figure 9 – Hirth S1215 50hp EFI engine – Denel Seeker 200 UAV



Figure 10 – Hirth 3503 water cooled engine – Saab Skeldar UAV



Figure 11 – 3503 50hp water cooled engine – Indra Pelicano UAV

There are other UAV’s flying Hirth engines but these are not in the public domain so are not shared in this post.  UAV propulsion system requirements are getting more demanding as manufacturers are improving reliability and reducing costs for both defense and commercial applications.  The engine is a key system responsible for the overall UAV reliability and operating cost/hr so engine manufacturers are using advanced technologies that are typically found on automotive engines to improve reliability, performance and running costs.   Those technologies in combination with high end electrical connectors, wire harnesses, starter/generators and advanced measurement/testing allow the propulsion system to meet demanding UAV reliability and performance requirements.

You can find out more about what propulsion systems are powering UAV’s by attending a trade show (like AUVSI) or some of the large defense conferences like IDEX, AUSA, DSEi, EuroNaval, Eurosatory, SOFIC, and the global air shows like Paris, Farnborough, Avalon, Singapore and others.  These shows typically have UAV’s on display and most manufacturers are willing to discuss what is “under the cowling” at least on a general level.

Key UAV News for the Week:

Industry Events for the month of June:

Quote for the week:

 “The ones who are crazy enough to think that they can change the world, are the ones who do.” – Steve Jobs.

UAV Propulsion Tech is unmanned aerial vehicle (UAV) hardware solution provider of propulsion, servo, autopilot, rescue/recovery parachutes, electric turbofans, pneumatic launchers, capacitive liquid level sensors, engine sensors and gyro-stabilized EO/IR gimbal solutions. Click on the HOME link above or go to for more info.


UAV Propulsion Tech – Post #8 – Drones in Agriculture

Blog 8

Drones in Agriculture:

It has been about a month since my last blog post.  I have been very busy supporting the AUVSI conference in Atlanta, visiting customers and even spent a week at our vacation place in Port Austin, MI.  That gave me the idea for this week’s blog post.  Port Austin is located in the tip of the “thumb” in MI and is a small lake town but is located in Huron County which has a large farm industry.  The photo above shows Port Austin on Lake Huron and the surrounding farm area.

My drone experience has mainly been in the defense market so I needed to do some research for this post.  I also spent some time with my brother in MI who became the first person in MI to receive a COA from the FAA for Agriculture.  He is a Pioneer seed dealer in Sanilac County and purchased an AgEagle drone last year to market Ag services.  He still has some boxes to tick with the FAA before he can start offering paid services but he is on his way to provide these valuable services in the “Thumb area” of MI.  You can find out more about his capabilities and business at

So what is the big deal about drones in agriculture?  In the past, farmers would walk their fields to get a better understanding of insects, irrigation, growth, weeds, etc.  They also could use an aircraft to get an aerial view if they have a large farm but this can cost up to $1000/hr.  Several companies now offer small fixed wing electric UAV’s with autopilots and cameras that allow the drone to fly over a field in a fixed pattern and the images can be stitched together using software and then analyzed.  The autopilot uses GPS for positioning and automatically captures images during flight.  There are also other payloads including infrared cameras that provide more analysis capabilities. Some companies that offer these types of systems are shown below:


Figure 1: Ag Eagle (



Figure 2: QuestUAV (www.questuav)



Figure 3: SenseFly (



Figure 4: Event38 (

There are others but I thought I would only note a few.  There are some quadcopters also being used for agriculture but for field mapping, they don’t have the range that a fixed wing has so they are mainly used for photography in specific areas of a farm.  I did see on today there was a Kickstarter campaign for a gas engine powered quadcopter.  This would definitely improve range.  Pretty impressive video if you want to check it out:


Figure 5: Yeair German gasoline engine powered quadcopter – Kickstarter campaign

Depending on the payload of the drone, there are several things you can learn about your crops.  You can do plant counts, check irrigation, capture thermal imaging to understand plant health, diagnose pest issues, and understand nutrient deficiencies.  All this will aid in proper management of the crops for best yield.  I don’t have any relationship with Sensefly but their website for their eBee Ag drone has a good list of available sensors and what they can measure.  Check out  Use of drones in agriculture is making “precision agriculture” possible.

Another use is in seeding and spraying, and Yamaha RMAX helicopter is the expert in this area.  This drone has over 1 million flight hours and was developed to seed and spray rice crops in Japan.  It is offered in the US but is pricey compared to the electric drones noted above for farm management.  I would think if you have a vineyard or some other crop that has critical spray needs, then this may be a good solution for your farm.  It also does precision agriculture management like the fixed wings but their primary purpose is in spraying.  You can find out more about this solution at


Figure 6: Yamaha Rmax helicopter

As noted above there are several solutions for today’s farmers to purchase or to purchase services to optimize their farming operations by using these high tech “precision agriculture” tools.  I am by no means an expert in this area but wanted to relay some solutions I have come across in my research and time working in the drone industry.

Key UAV News for the week:

Industry Events for the week:

Quote for the week:

“For of all gainful professions, nothing is better, nothing more pleasing, nothing more delightful, nothing better becomes a well-bred man than agriculture.”  Marcus Tullius Cicero

UAV Propulsion Tech is unmanned aerial vehicle (UAV) hardware solution provider of propulsion, servo, autopilot, rescue/recovery parachutes, electric turbofans, pneumatic launchers, capacitive liquid level sensors, engine sensors and gyro-stabilized EO/IR gimbal solutions. Click on the HOME link above or go to for more info.


UAV Propulsion Tech Post #7 – Preparing for AUVSI

Blog 7

Preparing for AUVSI:

AUVSI’s Umanned Systems 2015 trade show is next week (MAY 4-7) in Atlanta, GA.  I have been attending this show for the past 10+ years.  They used to alternate between west coast (Southern California) and east coast (DC area) but have been expanding beyond these areas.  Last year it was in Orlando and next year it will be in New Orleans.  Here is AUVSI’s website link to help plan your trip:

I thought I would say a few things about this great unmanned systems international event.  There is a focus on all things unmanned (including ground and water) but my focus has mainly been focused on unmanned aerial vehicles (UAV’s).  The show recently has also been more focused on the commercial side of the UAV market including lower cost multicopter and fixed wing solutions for aerial photography, police, agriculture and new markets that are opening up every week that are taking advantage of these tools.  I market propulsion, servo, autopilot and rescue/recovery parachutes for the UAV market so I support several companies during the week.  These include Orbital (heavy fuel UAV engines), Hirth (COTS/Custom propulsion and starter/generators), Volz (actuators), Skygraphics (rescue/recovery chutes) and MicroPilot (AutoPilots).

I will arrive into the Atlanta area on SUN, support set up of exhibits on MON support the trade show during the week.  The trade show goes from TUE -THUR.  The areas I will be supporting are:

  • Hirth booth #2736
  • Volz booth #2739
  • MicroPilot booth #1513
  • Orbital doesn’t have a booth this year but I will be supporting meetings with their CTO.
  • Skygraphics doesn’t have a booth this year but I will be available to discuss rescue/recovery parachute solutions.

I have noted these on the exhibitor map below.  AUVSI has a great floorplan tool for searching for companies to help prepare for your trip.  Here is the link:

Blog 7 #2

Check out my website: for more info on the UAV solutions I can provide.  If you are working in the unmanned market then this is definitely the trade show for you.  You can network with customers, potential suppliers and get a better understanding of the market.  This is always a busy week for me but is always worthwhile.   I do attend other trade shows to market UAV solutions but this one is definitely the largest and most focused on UAV’s.

I usually attend AUSA (the annual Army Conf in DC) which is focused on everything sold to the US Army.  You will see UAV’s there but mainly the larger prime contractors.  There used to be a conference in Europe hosted by Shephard’s (UV Europe), which was a smaller event but European focused.  At the moment there isn’t a large UAV focused event in Europe.  AUVSI hosts a small event in Brussels so maybe this will get larger and become the “go to” UAV event in Europe.  There are UAV exhibits at the Paris and Farnborough Air Shows but again, not as focused on UAV’s as Unmanned Systems 2015 trade show.  Similar comments about Avalon Air Show in Australia, Eurosatory, EuroNaval, DSei, IDEX and the Singapore Air Show.  All great shows but not as heavily focused on UAV’s.

If you attend the show, look me up.  I would enjoy discussing how I could support your US UAV programs.

Key UAV News for the Week:

Industry Events for the Week:

Quote for the Week:

“A strong America is the world’s best hope for peace and freedom. Yet the cause of freedom rests on more than our ability to defend ourselves and our allies. Freedom is exported every day, as we ship goods and products that improve the lives of millions of people. Free trade brings greater political and personal freedom” George W. Bush

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UAV PropulsionTech Post #6 – COTS Piston Aero Engines for UAV’s

#6 post COTS Piston Aero Engines for UAV’s: A week ago a guy thought it would be a great idea to land a gyrocopter on the Capitol lawn to deliver letters to try to change campaign finance laws.  Pretty crazy idea that highlights some flaws in DC’s security over this type of spectacle.   Luckily he wasn’t there to hurt anyone.  I live in the Tampa area where this guy is from so have seen several articles and stories about this event.   It made me want to focus this week’s topic on the use of COTS piston aircraft engines on UAV’s. Piston engines (both 2-stroke and 4-stroke) have been used in manned aviation for a long time.  2-stroke engines are typically used in sport aviation applications like ultra-lights, paragliders, and experimental aircraft because of their great power to weight ratio.  This engine market is typically served by Rotax, Hirth, MZ and Limbach. 4-stroke engines are used on larger FAA certified aircraft like Cessna, Piper and Cirrus, and this engine market is typically served by Lycoming, Rotax and Continental. Some UAV’s are even trying to use some of these COTS engines for their applications but out of the box, the COTS engines are not the best solution for a UAV.  Even though some of these engines are FAA certified, they have not been optimized for a UAV.  They typically still require some modifications in order to meet the demanding requirements of a UAV.   Typical upgrades include:

  • Generators – Electrical power needs to be increased to meet the power requirements of the UAV.  Most COTS engines have small generators to power the fuel injection system (if available) and some aircraft electronics.  UAV’s require high power density generators that are typically heavily integrated to the engine to minimize weight.  Some also want a start function with the generator for electronic start capability.  Datasheet on Hirth 2kW starter/generator.

generator pic

Figure 1: Hirth Starter/generator integration in HF3503 engine

  • Fuel consumption – Low fuel consumption is a key requirement for UAV’s to improve endurance.  Some 2-strokes use piston porting and carburetors to reduce engine cost which compromises fuel consumption.  UAV’s need to have the lowest fuel consumption at cruise so the engines calibration for best fuel consumption needs to be optimized at this point.  This can be achieved by using direct injection to allow lean stratified operation (low fuel consumption) at cruise and to enable spark ignition operation on heavy fuel









Figure 2: Hirth’s “iPower” direct injection technology

  • Noise/heat signature – The exhaust system needs to be optimized to minimize noise, reduce weight and minimize heat signature (to reduce detection).

S1215 Web

Figure 3: Hirth S1215 UAV engine – Exhaust optimized for weight/noise

  • Electrical noise – The ignition, wiring and engine control unit (ECU) needs to be shielded to minimize electrical noise that can impact payload or communication.  This is achieved thru proper electrical connector selection and harness/ECU/ignition shielding.
  • Diagnostic/communication – The ECU should have a communication method (typically CAN bus) to interface with the flight computer to monitor engine operation.  Electronic fuel injected engines measure several engine parameters to control fuel/air/ignition and these parameters can also indicate engine health and fuel burned.









Figure 4: Hirth ECU with shielded case/connector & CAN or RS485 communication

  • Throttle control – A number of UAV’s are using electronic throttle actuators that are attached directly to the throttle blade.  This provides the best throttle control and doesn’t require the UAV manufacturer to adapt their own servo/linkage system.  Volz is one of the few servo suppliers with engine throttle solutions.

 DA20T clear

Figure 5: Volz engine throttle servo

As noted in this brief summary, COTS aero engines require further optimization to be utilized on a UAV.  This can easily be done and has already been done on some applications flying today.  Hirth’s F23 COTS 50hp air cooled boxer engine is a good example.  The sport aviation engine has been a big success in the sport aviation market because of its power/weight, cost and reliability.  When a UAV customer wanted to use the same engine, Hirth upgraded the engine (now an S1215) to include the items shown in the list above.  This now meets the UAV requirements that weren’t being met with the COTS engine.  This engine will be on display at AUVSI at the Hirth booth #2736 in May.  Stop by and check it out.

Key UAV News for the Week:

Industry Events for the Week:

Quote for the Week: “I believe with all my heart that our first priority must be world peace, and that use of force is always and only a last resort, when everything else has failed, and then only with regard to our national security”.  – Ronald Reagan.

UAV Propulsion Tech is unmanned aerial vehicle (UAV) hardware solution provider of propulsion, servo, autopilot, rescue/recovery parachutes, electric turbofans, pneumatic launchers, capacitive liquid level sensors, engine sensors and gyro-stabilized EO/IR gimbal solutions. Click on the HOME link above or go to for more info.


UAV Propulsion Tech Post #5 – Rescue/Recovery Parachutes


Rescue/Recovery Parachutes:

This weeks post focuses on rescue/recovery parachute solutions for UAV’s.   At the moment, most small UAV’s don’t have a rescue parachute but they are a great idea to protect the air vehicle/payload asset as well as protect any people or property.  Parachute solutions are used on rockets and even Cirrus Aircraft has a ballistic recovery solution if there is a problem with the engine.  Here is a great video where a guy was trying to fly from CA to Hawaii and ran out of gas recently.  This video highlights how these types of systems can work to save people and assets.

Hobby mult-icopters are becoming very popular for aerial photography but most don’t have a parachute system.  At this year’s CES in Vegas, a Chinese manufacturer came out with a new multi-copter that includes a rescue chute. The company is Hubsan and here is a video with more info.  There are companies that are developing “bolt on” parachute solutions for multi-copters but the challenge is always weight and deployment means.  You want to make sure the parachute can deploy successfully at low altitudes (say 20-30m), for these hobby multi-copter solutions.  Some deployment means include: spring, compressed air, or ballistics.

Several UAV manufacturers are seeing the benefits in adding a rescue chute to protect the expensive air vehicle and payloads of defense UAV’s in case of a system failure.  Some are also using the parachute as a recovery method making it runway independent and it produces less stress on the air vehicle compared to net or wire capture methods.  There are several ways to mount these systems on fixed wing UAV’s.  I have shown a typical opening sequence below:

deployment sequence

Figure 1: Graphic showing deployment of rescue/recovery chute on fixed wing UAV

Parachute technology is advancing to provide lightweight solutions for the UAV market.  These systems will become more important as commercial applications are flying over civilian areas.  There are various methods and these systems can be customized to meet the UAV manufacturers requirements for max speed at deployment and max sink rate.  You can find out more about these systems by going to

Key UAV News for the week:

Industry Events for the week:

Quote for the week:

“Do not be embarrassed by your failures, learn from them and start again.” – Richard Branson

UAV Propulsion Tech Post #3 – Improving UAV Reliability

Post #3

This post will focus on ways to improve UAV reliability.  UAV reliability becomes very critical as payload costs increase and more UAV’s are being used for civilian applications flying over populated areas.  The photo in the graphic above is the Ruag Ranger UAV from Switzerland that is one of the few UAV’s certified to fly over civilian air space.   This application uses an engine from Hirth Motors.  This post will have some bias towards the reliability features of the companies products represented by UAV Propulsion Tech.  This will be detailed further below after the UAV news section.

 Key UAV News for the Week:

Improving UAV Reliability:

There have been several advances in UAV technology that provide significant improvements in reliability.  I will try to detail some of these below with a focus on propulsion, servo and autopilot advancements.

Propulsion:  Propulsion systems are one of the key systems impacting UAV reliability.  UAV manufacturers of small air vehicles (<50 lbs) have been using off the shelf RC and industrial engines that were never intended to be used under the extreme operational environments of UAV’s.  Most are carbureted with no altitude compensation capability and no health monitoring capability.  The gasoline engine on your car has more health monitoring capability and is more reliable than most UAV engines on the market today.

To improve propulsion reliability, you can do this two ways.  You can make the engine redundant (two engines are always better than one) or you can utilize advanced engine management systems (EMS) to optimize the combustion process, make EMS and control systems redundant, and monitor engine health with the flight computer.


Figure 1: DroneTech UAV – AV-1 Albatross

One company taking the “two engine” approach is the US company DroneTech UAV.  They are using two engines on their AV-1 Albatross.  The primary purpose is to have two engines for take-off and then shutting one engine down for improved endurance (via reduced fuel consumption) but the UAV could also run continuous with both engines for improved reliability.  Both engines have starter/generators allowing for shutdown/re-start in the air if required.  You can find out more about this UAV at and Hirth engines at









Figure 2: Hirth Engine Control Unit

Hirth’s advanced electronic fuel injection technology provides reliable combustion solutions for aircraft (both port fuel injection and direct injection solutions).  Offering CAN or RS485 communication with the aircraft flight computer to monitor all engine parameters such as CHT, EGT, throttle position, engine speed, fuel consumption, etc.  Also is shielded to protect against EMC/RFI.












Figure 3: Hirth’s 4201 15hp EFI engine with electronic throttle servo.

Servo/Actuator:  Similar to my comment on propulsion systems for small UAV’s, most of these UAV’s are using off the shelf RC servos that don’t have the same reliability as a servo developed for these extreme applications.  Volz servos are used by several high end UAV applications and their experience supplying into this market has evolved the product for improved reliability.  They offer a range of servos for small and large UAV’s.


Figure 4: Volz Servos

Some of the advancements for improving reliability include:

  • Clutch system to protect gears from stripping if control surface is impacted on landing (belly or net).
  • Brushless motors for improved durability.
  • Contactless position sensors for improved durability.
  • Monitoring of internal temp/humidity of larger servos.
  • New redundant servo options for larger servos.


Figure 5: Volz DA26 D redundant servo

The new fully redundant DA26 D is developed for applications that require high reliability.  The servo is a redundant two channel design that allows the servo to operate even if one channel fails.  All major components such as motors, control, communication electronics and power supply are redundant.  The position sensor has a three channel design where two out of three vote on the correct position.  Go to for more info.

Autopilots:  MicroPilot provides autopilot solutions for low end and high end UAV applications.  They also offer a trueHWILmp solution which is a set of hardware and software components that provides environments for the true real-time simulation of flights of MicroPilot autopilots MP2128g2 and MP2x28g2. The simulator allows you to test the MicroPilot autopilot in flight while the autopilot is sitting on the ground. The trueHWILmp provides a safe testing environment for all UAV components and allows adjusting flight parameters and checking the integrity and functioning of on-board equipment and payload.


Figure 6: MicroPilot True Hardware in Loop autopilot simulation tool


Figure 7: MicroPilot triple redundant autopilot.

The other product MicroPilot has is a triple redundant autopilot solution.  Redundancy is a great way to improve reliability in a UAV as noted above in the servo and propulsion sections.  MicroPilot’s MP21283X contains three  MP2128HELI2 autopilots.  This is a great system to protect expensive payloads and protect the UAV when flying over sensitive areas.  It has 11 serial ports, 8 redundant high-current drivers and power supplies, and 16 independently-generated servo signals.  The MP21283X  is the only triple redundant COTS autopilot in the market today.  Go to for more info.

Rescue parachutes: The solutions shown above will improve the reliability of the UAV but systems can still fail and if they do, it is a good idea to have a rescue parachute system.  These are used on manned aircraft applications and Skygraphics out of Germany has a lightweight/compact solution for the UAV market.  This allows you to save valuable air vehicle and payload assets if there is a system failure.  The ProtectUAV system from Skygraphics is 30% lighter/smaller than competing parachute systems on the market.  You can find out more about these solutions at

Protect UAV new

In summary, there are advanced solutions today that can improve the reliability of a UAV to keep it in the air.  As civilian air space opens up for commercial UAV’s, some of these solutions may be required to show system reliability and may also be required by the company’s insurance provider.

Industry Events for the Week:

Quote for the week:

“Simplicity is the prerequisite for reliability.”  – Edsger Dijkstra

UAV Propulsion Tech is unmanned aerial vehicle (UAV) hardware solution provider of propulsion, servo, autopilot, rescue/recovery parachutes, electric turbofans, pneumatic launchers, capacitive liquid level sensors, engine sensors and gyro-stabilized EO/IR gimbal solutions. Click on the HOME link above or go to for more info.


UAV Propulsion Tech – Post #2 – Get more thrust with a propeller reduction drive

reduction drive

This is my second UAV blog post and today I am going to focus on the advantages of a propeller reduction drive system to improve thrust in a UAV.  This will be detailed further after the key UAV news section.

Key UAV News for the week:

Get more Thrust with a Propeller Reduction Drive:

Reduction drive systems have been around a long time in the consumer aircraft industry (since the early 1900’s) but are not that common yet in the UAV industry.  Most systems are direct drive but some UAV companies are seeing the benefits in using a reduction drive to spin a larger propeller slower to increase thrust and reduce fuel consumption.

Commonly called propeller speed reduction units, these are either gear boxes or pulley belt drives that reduce the propeller speed compared to the engine output speed.  This helps optimize the propeller speed for the application.  Piston aircraft engines (both 4-stroke and 2-strokes) typically generate maximum power from 4,500 – 6,500 rpm but the most efficient speed for the propeller is typically 2,500-3000 rpm.  A reduction drive allows the engine to operate at peak power while spinning the propeller at its most efficient speed.

In optimization of the propeller, you do have to keep the propeller tip speed below the speed of sound.  I did find a website with a tip speed calculator. This site notes the optimum speed is between Mach 0.80-0.92.  I found another site that can calculate static thrust based on propeller speed, pitch and diameter.  You can use this to see how a change in speed and diameter can improve thrust.

Reduction drives aren’t typically used on small engines (say <10hp) but can be effective on engines 15hp to 100hp+.  On one application, we used a 1:1.7 belt reduction drive on a 15hp engine and doubled the propeller diameter.  The result was the static thrust was doubled.  A couple things you have to keep in mind is there could be propeller diameter limitations due to the launcher (if there is a launcher), or ground clearance if it is a runway take-off/landing application.

Aero engineers should evaluate this alternative to achieve the desired thrust with the smallest engine possible in order to maximize fuel consumption and flight endurance.  This will also minimize overall propulsion weight.

Industry Events for the Week:

Quote for the week:

“If the facts don’t fit the theory, change the facts.” – Albert Einstein

UAV Propulsion Tech – Post #1 – BSFC Calculation

blog 1 I am starting a weekly blog on the UAV industry and intend to focus my weekly posts on technology, global markets, applications, and industry news.

I am a mechanical engineer and have been working in the UAV business for over 10 years mainly focused on propulsion solutions for defense applications.  I represent several companies providing propulsion, servo/actuators, rescue/recovery parachutes and autopilots into this market.

The format I will start with is to lead with UAV news for the week, then add some technical info on some aspect of UAV’s, list upcoming events and then close with an inspiring quote for the week.  I may adjust this format in the future.

Key UAV News for the week:

Brake Specific Fuel Consumption (BSFC):

BSFC is the measure of fuel efficiency for internal combustion engines.   It is the power specific fuel consumption and is calculated by: fuel consumed (lbs/hr) divided by horsepower.   Typically the fuel consumed is measured in gallons per hour and you can convert this to lbs/hr using the mass of the fuel tested.   UAV’s typically fly on gasoline, jet fuel or diesel fuel.  The mass of these fuels are:

  • Gasoline weighs 6.1 lbs/gal
  • Jet A weighs 6.8 lbs/gal
  • Diesel fuel weighs 7.1 lbs/gal

BSFC is noted in lbs/hp-hr and g/kW-hr.  When an engine is developed for a UAV, the BSFC is typically optimized for the cruise point in order to minimize fuel consumption and maximize endurance.  This is typically 50-75% of WOT depending on the application.  The BSFC calculations at various operating points and information on a typical mission profile can allow the UAV manufacturer to predict fuel burn per mission.

Wikipedia has a good description of BSFC as well as a list comparing various engines.

Optimization of the propulsion system for power, weight, fuel consumption and reliability are key parameters for the UAV developer.

Industry Events this week:

Quote for the week:

“Success is not final, failure is not final: it is the courage to continue that counts” Winston Churchill