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general question on endurance

Old 01-29-2016, 01:02 AM
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racereed
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Default general question on endurance

I've been reading about and watching videos on the Scan Eagle. Nothing really super fancy, weights 48 lbs and has an endurance of 22 hours. My question is: It appears that the Scan Eagle as a rc type gas engine with a 3 blade pusher prop. 22 hours just seemed almost impossible for something roughly the size of a 1/4 extra 300 that weights almost 50 pounds. Also the Scan Eagle has no tail, horizontal stabilizer or ruder or elevator. Just a central fuselage with swept wings. Can you achieve similar results with a 30cc gas engine in regards to 22 hours endurance? How much fuel would you need?
Old 01-29-2016, 09:40 AM
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I am no drone expert but do know my way around model engines. There is no great difficulty in getting that sort of endurance from that kind of clean airframe and fuel efficient engine. Think Honda 50 not Bulgarian 2st strimmer. At a rough guess 15 to 20 lbs fuel.

As for the slightly unconventional layout it is a big Zagi .I can confirm that they fly extremely well upright inverted in combat or just being thermalled.
Old 01-30-2016, 09:08 AM
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Your post intrigued me to Google this UAV. It does look interesting, and seemingly is under development all the time. I too can easily see how this aircraft/drone could stay aloft for 24hrs if conditions and equipment would allow it. A quick Wiki search came up with some specs on it, and it apparently will cruise at 69mph, with a top-speed of 92mph.

My thought says that when they get this plane up in the jet stream, they can do all kinds of things, like conserve fuel and energy while the plane uses the atmosphere/winds/sun (if there's any solar technology on it, which there might be by now) to get optimize its performance for whatever mission they're using it for.

This is all pure speculation on my part, but that machine/drone looks to be very sophisticated and very interesting. Oh... they do call out the engine as a "2-stroke 3W piston engine".... Here's a link to the Wiki page:

https://en.wikipedia.org/wiki/Boeing_Insitu_ScanEagle#Specifications
Old 01-30-2016, 02:02 PM
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Originally Posted by DGrant
Your post intrigued me to Google this UAV. It does look interesting, and seemingly is under development all the time. I too can easily see how this aircraft/drone could stay aloft for 24hrs if conditions and equipment would allow it. A quick Wiki search came up with some specs on it, and it apparently will cruise at 69mph, with a top-speed of 92mph.

My thought says that when they get this plane up in the jet stream, they can do all kinds of things, like conserve fuel and energy while the plane uses the atmosphere/winds/sun (if there's any solar technology on it, which there might be by now) to get optimize its performance for whatever mission they're using it for.

This is all pure speculation on my part, but that machine/drone looks to be very sophisticated and very interesting. Oh... they do call out the engine as a "2-stroke 3W piston engine".... Here's a link to the Wiki page:

https://en.wikipedia.org/wiki/Boeing_Insitu_ScanEagle#Specifications
As an IC engined drone it is likely to be used at fairly low altitudes nothing more than 700 m above ground where it will be virtually invisible but still capable of sending back useful video telemetry.

Stuff that flies in the jet stream will be turbine powered. For some time now military drone manufacturers have been major customers with model turbine makers like AMT.
Old 01-31-2016, 04:37 PM
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I was flying a swept wing tailless drone (electric) surveying crops two years ago. We were getting flight times of 60 to 65 minutes. I don't know exactly how big the battery was as it was sealed in a "pod" but from the amps put back in I would say about 5000 milliamps battery. I can see an IC engine getting good duration with proper throttle management and the right wing design optimized for duration.
Old 01-31-2016, 10:54 PM
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Notice the service ceiling of 19,000+ft. The higher you go you have less air to run the engine. Less air means you need less fuel. The carb has to have some way to lean out. Once it gets to altitude it can sip on fuel at minimum airspeed. Maynard Hill has plenty of world records and all I believe were powered by an OS .60 4 stroke converted to gas and because of the world record rules cant weigh more than 11 lbs. At least in the US those records will not be broken because of the drone rules.
Old 02-01-2016, 07:46 AM
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I believe Maynard Hill's early records were all set using 2 st engines Fox 59 to begin with then ST 60s.

His transatlantic model TAM 5 AKA The Spirit of Butt's Farm was powered by 4 st OS but modified to use a tiny carb. The flight took 38 hours, 52 minutes, 19 seconds This was a fantastic achievement as they had to stick to the 11 lb max weight demanded by the FAI rules.

Last edited by j.duncker; 02-01-2016 at 07:48 AM.
Old 02-01-2016, 08:22 AM
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He was in the business of breaking records. My first learning of him was in the late 70s which by then I think the OS became his standard. Anything Fox 59 predates me by a good bit. I think he used a OS .10 carb modified.

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