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Old 12-18-2011, 05:01 AM   #1
awrightbrother
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Default Scale A10 from Wowplanes - Big Bird

I have always been particularly fascinated with the A10 Thunderbolt aka The Warthog. Around 4 years ago I had designed and kitted a 62" span model. That was before I got infected with the scale virus, so that was more of a fun scale design. It turned out to be an amazingly easy plane to fly, very manueverable and stable, and easy to land. Ever since then I have been wanting to do a scale version, and so here we are.

While at it, I thought it would be nice to scale up to an IMAA legal Big Bird size. For a jet, IMAA rules require that the sum of the wingspan and the length be at least 140". A wingspan of 74", yields a fuselage length of 67", which adds up to the magical 140+1". So that's where we are headed. At 74" span it is a 10.5% scale.

I could have made it bigger, but decided to stay with 74", a size that can easily be transported in most cars and yet be eligible to participate in Big Bird events. The other consideration was cost.

HISTORY
The A-10 Thunderbolt II is an American single-seat, twin-engine, straight-wing jet aircraft developed by Fairchild-Republic in the early 1970s. The A-10 was designed for a United States Air Force requirement to provide close air support (CAS) for ground forces by attacking tanks, armored vehicles, and other ground targets with a limited air interdiction capability. It is the first U.S. Air Force aircraft designed exclusively for close air support.
The A-10's official name comes from the Republic P-47 Thunderbolt of World War II, a fighter that was particularly effective at close air support. The A-10 is more commonly known by its nickname "Warthog" or simply "Hog". As a secondary mission, it provides airborne forward air control, guiding other aircraft against ground targets. The A-10 is expected to be replaced in 2028 or later.

DESIGN
The A-10 has superior maneuverability at low speeds and altitude, due to large wing area, high wing aspect ratio, and large ailerons. The large high aspect ratio wing also allows for short takeoffs and landings, permitting operations from primitive forward airfields near front lines. It typically flies at a relatively slow speed of 300 knots (560 km/h; 350 mph), which makes it a much better platform for the ground-attack role than fast fighter-bombers, which often have difficulty targeting small and slow-moving targets.

The ailerons are at the far ends of the wings to gain greater rolling moment, as with many aircraft, but there are two distinguishing features. First, the ailerons are larger than is typical, almost 50% of the chord, providing improved control even at slow speeds. The aileron is also split, making it a deceleron.

The sturdy landing gear, low-pressure tires and large, straight wings allow operation from short rough strips even with a heavy ordnance load, allowing the aircraft to operate from damaged airbases. If runways are damaged in an attack, the A-10 can operate from taxiways, or straight roadway sections, such as Germany's autobahn.

DURABILITY
The A-10 is exceptionally tough. The aircraft is designed to fly with one engine, one tail, one elevator and half a wing torn off.

The A-10's main landing gear is designed so that the wheels semi-protrude from their nacelles when the gear is retracted so as to make gear-up landings (belly landing) easier to control and less damaging to the aircraft's underside. A belly landing would be required in the case of a landing gear failure. Additionally, the landing gear are all hinged toward the rear of the aircraft, so if hydraulic power is lost the pilot can drop the gear and a combination of gravity and wind resistance will open and lock the gear in place.

There are several reasons for the unusual location of the A-10's General Electric TF34-GE-100 turbofan engines. First, the A-10 was expected to fly from forward air bases, often with semi-prepared substandard runways that presented a high risk of foreign object damage to the engines. The height of the engines lowers the chance that sand or stones will enter the inlet.

I will attempt to model the aircraft and color scheme shown in the picture below.


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Old 12-18-2011, 07:11 PM   #2
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There is one thing you missed, this aircraft is designed around a gun as large as a VW Beetle. If you hear the gun, then it is too late.

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Old 12-18-2011, 10:46 PM   #3
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Originally Posted by tarheal63 View Post
There is one thing you missed, this aircraft is designed around a gun as large as a VW Beetle. If you hear the gun, then it is too late.
You are absolutely correct. The main reason for building the A10 was to find a vehicle for this famous gun.

Following is some background on this famous gun.

The General Electric GAU-8/A Avenger is a 30 mm, hydraulically-driven seven-barrel Gatling-type rotary cannon that is mounted on the A-10 Thunderbolt II. It is among the largest, heaviest and most powerful aircraft cannons in the United States military. Designed specifically for the anti-tank role, the Avenger delivers very powerful rounds at a high rate of fire.

The gun is placed slightly off center in the nose of the plane with the front landing gear positioned to the right of the center line.

A very important innovation in the design of the GAU-8/A shells is the use of aluminum alloy cases in place of the traditional steel or brass. This alone adds 30% to ammunition capacity for a given weight. The shells also have plastic driving bands to improve barrel life. They are imposing to examine and handle, measuring 11.4 inches (290 mm) in length and
weighing 1.53 pounds (0.69 kg) or more.

The Avenger's rate of fire was originally selectable, 2,100 rounds per minute (rpm) in the low setting, or 4,200 rpm in the high setting. Later this was changed to a fixed rate of 3,900 rpm. In practice, the cannon is limited to one and two-second bursts to avoid overheating and conserve ammunition; barrel life is also a factor, since the USAF has specified a minimum life of at least 20,000 rounds for each set of barrels. There is no technical limitation on the duration the gun may be continuously fired, and a pilot could potentially expend the entire ammunition load in a single burst with no damage or ill effects to the weapons system itself. However, this constant rate of fire would shorten the barrel life considerably and
require added barrel inspections and result in shorter intervals between replacement.

The A-10 engines were initially susceptible to flameout when subjected to gases generated in the firing of the gun. When the GAU-8 is being fired, the smoke from the gun can make the engines stop, and this did occur during initial flight testing. Gun exhaust is essentially oxygen-free, and is certainly capable of causing flame-outs of gas turbines. The A-10 engines have a self sustaining combustion section. When the gun is fired the igniters come on to ensure no flame out occurs.

The recoil force of the GAU-8/A[14] is 10,000 pounds-force (45 kN), which is slightly more than the output of one of the A-10's two TF34 engines (9,065 lbf / 40.3 kN each). While this recoil force is significant, in practice cannon fire only slows the aircraft a few miles per hour.


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Old 12-19-2011, 12:11 AM   #4
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I too have been fascinated with the Warthog. I have been searching for plans or a decent kit that doesn't weigh as much as a car. I saw a foamy ~64" one at the field on Saturday and it looked awesome in the air but the gear were weak and broke just cause it rolled into the short grass.

I just cant get behind flying packing material around the sky but beyond that this one was a little heavy at obviously didn't represent the durability of the scale planes gear.

I would like to find something that is light. However, the actual weight is not so important but the wing loading is. The model should be durable like the full scale plane and able to handle a grass or dirt runway.

Are you going to publish your plans?

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Old 12-19-2011, 01:31 AM   #5
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saw this fly at an ocala flyin.. hate to be a downer.. it wasn't as i would expect. he did have lights in it but in the world of newer EDF is took off like an older IDF fan.

the other kicker wad the fans etheir weren't scale OR it was streched to make that lenght. and for the price of the kits i decided to eventually build the george miller plans i own.

which i actually then saw one converet to electric at the 2011 fits. powered by two 96mm fans and a 6cell lipo on each side.. and it was taking off from grass.

A am a big A-10 fan , and glad youe building one.. they never disappoint. but if it isn't scale and i was going to be putting in A lot of time , i wanted the kit to be right.

pics from ocala bigbird that year

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Old 12-19-2011, 03:00 AM   #6
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Although the A10 is a jet, it is the slowest jet and is not meant to be flown fast. Its typical speed is 350 mph about the same as a P51. It was built to fly slow for ground attack where fast jets are useless.

This video is an example of how an A10 should be flown especially if one is a scale buff.

The challenge before us is to build something that not only looks scale, but also performs scale.

(Sorry, the forum rules do not allow me to post links until I have at least 3 posts, so please look for the link in my next post.)
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Old 12-19-2011, 03:01 AM   #7
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OK here is the link now.

http://www.youtube.com/watch?v=hIFyjVf1-vs&feature=related
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Old 12-19-2011, 03:07 AM   #8
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Here is how the one I am building will look and fly.

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Old 12-19-2011, 03:16 AM   #9
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It won the Florida Jets Trophy in 2011.

I am not smart enough to argue with the scale experts, but this is what they think.


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Old 12-20-2011, 12:27 AM   #10
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Dave
This one does fly off grass. My club is a grass field so all my designs have to fly off grass.

Here is the grass video.

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