BVM F-16N

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BVM F-16 Turbine Conversion
by
Gordon Dickens

I converted my BVM F-16 to turbine power prior to BVM’s introduction of their F-16 turbine conversion kit. The BVM conversion is designed around the RAM-500 turbine while my conversion included a fully bypassed JetCat P-80 installation. The scale subject for this model was a Navy Aggressor F-16N. The project was covered in the April/May, 2002 issue of Radio Control Jet International magazine complete with many photos of the scale subject.. I will post some additional photos of the scale subject at a later date.

The following overview should give you a pretty good idea of what is involved in converting the BVM F-16 model to turbine power.

The model is a 1/8 scale replica of the subject aircraft and was built from a BVM F-16C kit. The F-16 “N” is identical in outline to the F-16 “C” as can be denoted by comparing General Dynamics’ F-16N 3-views and F-16C 3-views. Statistics on the model are as follows:

Power: JetCat P-80 turbine at 17.5 pounds of thrust (117K RPM).

Turbine Bypass/tail pipe: Tom Robertson conversion kit.

Speed sensor: JetCat pitot tube mounted on the vertical fin. The speed sensor is set to a max airspeed of 170MPH.

Fuel Storage: 74 ounces plus a 4 oz BVM UAT. The "wet" centerline tank holds 24 ounces and 50 ounces are held in the fuselage.

Dry Weight: 17 pounds.


	The model is highly customized since it was constructed prior to the availability of BVM’s turbine conversion kit for the F-16. The model's internal fuel cells include two custom 22 ounce Kevlar saddle tanks that fit immediately over the inlet plus a six ounce header tank feeding into a BVM four ounce UAT.

The model includes an operational "wet" centerline tank which is a common F-16 fuel store. While the aggressor aircraft seldom fly with external fuel stores during aggressor training exercises, the external stores are used when the airplanes are flown nonstop over large distances. The model therefore was built to include the centerline tank which was painted consistently with the Marine camouflage scheme of the subject. The model’s centerline tank is attached at three hard points; Two control surface horns and one Vortac mechanism secure the tank to the fuselage. The “wet” center line tank was constructed from a standard BVM center line tank which was first first cut along its rear panel line, Then, one side of the cut was extended on its inner side with poly ply and reattached to the other side with panel screws. Note the carbon fiber cord used to stiffen the tank at both sides of the cut. A 24 ounce dubro fuel tank was installed within the centerline tank as depicted above.


	The aft six inches of the original BVM inlet was cut out and replaced with an inlet adapter. The inlet adapter can be seen at the rear of the inlet in the above left photo. The aft end of the inlet adapter was designed to match the front end of the bypass as is depicted in the above right photo which also shows the JetCat P-80 turbine within the bypass with the bypass lid removed.

The bypass is depicted in the above photographs with the turbine removed. The rear of the bypass was covered with BVM Heat Shield insulating paint. The cool operating temperature of the P-80 is apparent in these photographs which were taken after eight flights. As can be seen, there has not been any heat related discoloration or blistering in the bypass. The two plastic cowls that are shown within the bypass in the above left photo accommodate the landing gear arms when the gear is in the retracted position.



		The factory stock rear former in the main hatch area forms a semicircle under the bypass and it was reinforced with a custom ply/CF former that extends over the inlet to form a complete circle of reinforcement. The custom former is depicted above after having been removed from the airplane.
	The factory stock engine hatch is attached to the fuselage with a single BVM hatch latch located at the rear of the hatch. While wing flexing should be reduced with the added ply/CF former, a more rigid engine hatch attachment is needed to both reinforce the fuselage and ensure that the hatch does not come loose in flight. Therefore, the hatch is secured with 2-56 hex bolts and blind nuts in addition to the factory stock hatch latch. The blind nuts are mounted on plywood strips under the hatch flange and the hex bolts are shown mounted in the engine hatch in the photo at right.




		The custom former is shown installed over the bypass in the above photo.


	The model includes a functional pitot tube speed sensor that is mounted in the leading edge of the vertical fin as depicted in the photo at left. This is a very accurate reproduction of the probe that is mounted on the scale subject’s vertical fin. The model’s fin is removable and the mechanical rudder linkage and the air line connectors are shown in the above right photo.

The model’s tail pipe nozzle is depicted at right. The nozzle is attached to the fuselage with 12 poly ply screws. The inside of the nozzle as well as the entire aft end of the fuselage was painted with BVM Heat Shield insulating paint. A stainless steel ejector tube the exact shape of the nozzle is attached to the inside of the nozzle. A single wall tail pipe is attached to the rear of the bypass which extends to exactly 3/8 inches short of the aft end of the nozzle. Cloth insulation was laminated with heavy duty aluminum foil and attached to the top half of the entire length of the fuselage aft of the engine hatch for heat shielding.

BVM released an F-16 turbine conversion kit after I was finished with my conversion. The BVM conversion kit recommends cutting out a section of each stab and reinforcing the area with a carbon fiber plate that is bolted to the stab’s steel tube pivot axles. I purchased the CF parts and bolts from BVM and implemented the reinforcements to my stabs after the plane had been initially painted. The CF plates were reinforced with an epoxy/milled fiber/microballoon glue slurry that fills and stabilizes the area around the plates within the stab. The surface of the stabs were then finished with automotive finishing putty, primed and painted.

The picture to the right was taken from the BVM F-16 conversion instructions and depicts the CF plate installation. BVM now installs this modification during the manufacturing process at the factory. Therefore, this modification is only needed for kits that were manufactured prior to February, 2001


		The bottom of the right stab is shown below prior to the final primer coat.


	Flying


	This was an easy modification to implement. The right stab is depicted below following the modification, repainting and reinstallation.

The model definitely flies better than the ducted fan BVM F16 that I once owned especially on takeoff where the added thrust enables the model to accelerate to flying speed much more quickly than the ducted fan version.

I installed gyros on the rudder and ailerons and which are active only when the landing gear is deployed. I had never before installed a gyro on ailerons, however, in cross wind conditions my old ducted fan F-16 always wanted to tip over onto its wing tips (actually, onto its missiles and rails) during takeoff and especially on rollout after landing. I therefore decided to see if an aileron gyro would cure this tendency. This airplane is much less prone to being blown over onto its missiles than my older F-16 so the aileron gyro does help quite a bit.

The turbine powered model weighs about 1.5 pounds more than my older ducted fan model. The added weight over the ducted fan version is not very noticeable even on landing. Once in the air at moderate airspeeds, the model feels just like my old ducted fan F-16, however, my ducted fan F-16 never had the vertical performance or acceleration that my new turbine powered F-16 has displayed. This airplane is truly a performance aircraft and it is a pleasure to fly.

Gordon
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