FTFC'18 WWII - Ushakov LPL Flying Submarine by FoamyDM


Building Fool-Flying Noob
While rolling down the Soviet/Russian concept plane rabbit hole, I found this beauty.


Ushakov LPL Flying Sub Statistics:

Crew, man. 3
Takeoff mass, kg 15,000
Flight speed, UZ (km/h) 100 (~200)
Flying range, km 800
Ceiling, m 2 500
Quantity and the type of aircraft engines 3 x AM-34
Power on takeoff conditions, hp 3x1200

Submerged Characteristics

Underwater knots 2-3
Submersion depth, m 45
Action radius under water, miles 5-6
Underwater independence, h 48
Duration of sinking, min 1-5
Duration of immersion, min 1-8

- 18- in torpedo, pieces. 2
- coaxial machine gun, pieces. 2

Speed- 7?(Air)/0(Sub)
Torp 2/1

Model Statistics: (A/F Pack Version)

28" Wingspan
Motors: 2- A Packs + 1-F-Pack.
Estimated Thrust: 360+360+600 =~1320g
Servos: - 6 - 9g Metal Gear (1 for torpedo + 1 for Perscope {and ballast tube}
Battery - 3S 2200mAh
Props - 5" x 4.5 or 5"x3x3
Estimated Weight (without Torpedos): 560g
Wing area: 1.57sf
Wing Loading (without Torpedos) - 19oz./1.57sf or 12oz/sf with is in the glider/trainer portion.

My Goal:
1. Make a model that flies well.
2. Get it to float
3. Make it easy to build
4. Sink it
5. Get it to come back up.
6. Find a way to make the sub part affordable.

I know VERY little about RC Submarines. I have reached out to *the* Bob Martin IE www.RC-SUB.com and on Youtube he's RCSubGuy. This guy has a true passion and talent for submarines. He estimates a larger amount than I have to build this as a submerging vessel. (while I'm still trying to see what I can do to mitigate the Costs.) His sites, encouragement knowledge and thorough videos, should help me know how we can manage this. While a bit discouraged by the cost, I think I could set limitations of the vessel and get away with a less costly setup... but I'm not sure.

While rolling this around in the signup forum thread (linked in blue below), I talked out some feasibility on can a foam plane sink. Some of you might know first hand.

Displacement: 534g
Each foam board displaces 36g of water. My initial design is 4 sheets. (a c-size will take 8 at least)
I will assume the entire plane floods except the cockpit area I would have a watertight container in there.
The size is roughly 6.5x12x5cm or 390 ccm so that means the plane must weigh 534g. (1.2 lbs) for a 3 (4) engine Plane.

Weight: 355 - 560(ish)
5 -9g servos - 45g
4 - 40g motor setups (2205 with 30a ESCs and 5" prop, producing around 1.8kg thrust (for 3 engines)) 120g
8 channel receiver or FC - 10g
4S 1500 - 3500maH battery - 188 - 385g

So I see this as a matter of playing with the WT capsule size VS. Battery or foam load-out. to get things to balance when the plane floods.

Making this plane into a sub can/will include the following challenges:
  • The new skills will include building a waterproofed plane.
  • Learn how to Minwax a Plane (in and out)
  • Learn how to WP Servos.
  • Learning how to make a WTC for Subs.
  • Building a Sub motor system.
  • Learning to Fiberglass, then dissolve the foam inside.
  • Building air bloat bags.
  • Making Torpedoes.
  • Getting a 72-75mHz radio system with 6 channels. (2.4gHz doesn't travel through water)
  • Figure out how to use a FC to work it all.
  • Learning to design and build and print a 3D printed Plane. (to aid neutral buoyancy, by removing foam which makes traditional )

Now it's time to do it:
Made a first stab at plans are here:

Apparently I'm a sucker for a challenge. I hope you enjoy this thread as I try to make this fly, land and water, sink it and fly it back.

10/10/18 edit

Alpha Build plans. base on all the tests, this will Fly. I will make sure to mark the CG distance from Leading edge here when I can measure it.
LPL Flying Sub-Alpha 1 of 4
LPL Flying Sub-Alpha 2 of 4
LPL Flying Sub-Alpha 3 of 4
LPL Flying Sub-Alpha 4 of 4

Note: I had these ready LONG ago based on this first post. I just had NO idea if it would fly. None. (and at the time little confidence.)


  • UshakovLPLFlyingSub ShtA1 of 4.pdf
    30.8 KB · Views: 0
  • UshakovLPLFlyingSub ShtA2 of 4.pdf
    29.6 KB · Views: 0
  • UshakovLPLFlyingSub ShtA3 of 4.pdf
    29.6 KB · Views: 0
  • UshakovLPLFlyingSub ShtA4 of 4.pdf
    18.7 KB · Views: 0
Last edited:


Building Fool-Flying Noob
LPL Flying Submarine History

The History of the Ushakov LPL Flying Submarine

In the USSR on the eve of the Second World War, a project of a flying submarine was proposed-a project never realized. From 1934 to 1938 years. The project of the flying submarine was headed by Boris Ushakov. The flying submarine was a three-engine two float seaplane equipped with a periscope. While still studying at the Higher Marine Engineering Institute named after FE Dzerzhinsky in Leningrad (now the Naval Engineering Institute), from 1934 until his graduation in 1937, student Boris Ushakov worked on a project in which the capabilities of a seaplane were supplemented the capabilities of a submarine. The invention was based on a hydroplane capable of submerging under water.

In 1934, a cadet of the VMIU them. Dzerzhinsky BP Ushakov presented a schematic design of a flying submarine, which was subsequently reworked and presented in several versions to determine the stability and loads on the structural elements of the apparatus.

In April 1936, in the recall of Captain 1 rank Surin pointed out that the idea of Ushakov is interesting and deserves unconditional implementation. A few months later, in July, the half-draft LPL project was considered at the Scientific Research Military Committee (NIVK) and received a generally positive response containing three additional items, one of which read: "... It is desirable to continue the development of the project in order to reveal the reality of its implementation through the production of appropriate calculations and necessary laboratory tests ... "Among the signatories of the document were the head of the NIVK, a military engineer of rank 1 Grigaitis, and the head of the department of tactics of military means, the flagship of the 2nd rank of prof. The Goncharov.

In 1937 the topic was included in the plan of the department "B" of the NIVK, but after its revision, which was very characteristic for that time, it was abandoned. All further development was carried out by the engineer of the department "B" by military technician 1 rank BP Ushakov during off-duty hours.

On January 10, 1938, in the 2nd department of the NIVK-a, the sketches and the main tactical and technical elements of a flying submarine prepared by the author were examined. What was the project like? The flying submarine was intended for the destruction of enemy ships in the open sea and in the water area of sea bases protected by minefields and booms. A low underwater speed and limited cruising range under the water was not an obstacle, since in the absence of targets in a given square (area of action) the boat could itself find the enemy. Having determined from the air its course, it sat over the horizon, which precluded the possibility of its premature detection, and plunged on the line of the ship's path. Prior to the appearance of the target at the point of the volley, the flying submarine remained at a depth in a stabilized position, without expending energy by superfluous moves.
In case of an acceptable deviation of the enemy from the course line, the flying submarine went to approach it, and with a very large deviation of the target, the boat passed it beyond the horizon, then floated up, took off and again prepared for the attack.
The possible repetition of the approach to the target was considered as one of the significant advantages of the underwater torpedo aircraft before the traditional submarines. Particularly effective was the action of flying submarines in the group, because theoretically three such vehicles created an impassable barrier on the enemy's path, up to nine miles wide. A flying submarine could penetrate in the harbor and enemy ports during the dark, dive, and in the daytime observe, direction finding of secret fairways and in case of an opportunity to attack. The design of the flying submarine provided for six autonomous compartments, three of which housed AM-34 aircraft engines with a capacity of 1000 liters each. from. each. They were supplied with superchargers, which allowed forcing on takeoff mode up to 1200 liters. from. The fourth compartment was residential, designed for a team of three people. From it, the ship was steered underwater. In the fifth compartment there was a rechargeable battery, in the sixth - a rowing electric motor with a capacity of 10 liters. from. The robust housing of the flying submarine was a cylindrical riveted structure with a diameter of 1.4 m of duralumin with a thickness of 6 mm. In addition to strong compartments, the boat had a pilot light wet cabin, which was filled with water when immersed, while the flight instruments were filled up in a special mine.

The wings and tail fins were to be made of steel, and floats of duralumin. These elements of the design were not designed for increased external pressure, since during the immersion they were flooded with sea water, which flowed by gravity through the scuppers (holes for water drainage). Fuel (gasoline) and oil were stored in special rubber tanks, located in the center wing. When submerged, the supply and discharge lines of the water cooling system of the aircraft engines overlapped, which eliminated their damage under the influence of sea water pressure. To protect the body from corrosion, paint and varnish coatings were provided. Torpedoes were placed under the wing brackets on special holders. The design payload of the boat was 44.5% of the total flight weight of the vehicle, which was common for heavy vehicles.

The immersion process included four stages: the sealing of engine compartments, the shutting of water in the radiators, the transfer of control to the underwater and the transfer of the crew from the cabin to the living compartment (central control station). "

The motors in the underwater position were covered with metal shields. The flying submarine was to have 6 hermetic compartments in the fuselage and wings. In three compartments immersed during the immersion, the Mikulin AM-34 engines of 1000 liters were installed. from. each (with a turbocharger on take-off mode up to 1200 hp); in a sealed cabin should be located equipment, battery and electric motor. The remaining compartments shall be used as tanks filled with ballast water for immersing a flying submarine. Preparation for the dive should only take a couple of minutes.

The fuselage was to be an all-metal duralumin cylinder with a diameter of 1.4 m with a wall thickness of 6 mm. The cockpit was filled with water when immersed. Therefore, all devices were supposed to be installed in a waterproof compartment. The crew had to go into the diving control compartment, located further in the fuselage. Bearing planes and flaps should be made of steel, and floats of duralumin. These elements were supposed to be filled with water through the valves provided for this purpose in order to equalize the pressure on the wings during immersion. Flexible tanks of fuel and lubricants should be located in the fuselage. For corrosion protection, the entire aircraft was to be covered with special varnishes and paints. Two 18-inch torpedoes were suspended under the fuselage. The planned combat load was to be 44, 5% of the total mass of the aircraft. This is the typical value of heavy aircraft of that time. To fill the tanks with water, the same electric motor was used, which provided movement under water.

In 1938, the Military Scientific Research Committee of the Red Army decided to curtail the work on the project of the Flying Submarine because of its insufficient mobility in the underwater position. The resolution stated that after the discovery of the Flying Submarine, the ship would undoubtedly change its course. That will reduce the combat value of LPL and with a high degree of probability will lead to the failure of the task.

Specifications of the Flying Submarine:

Crew, persons: 3;
Take-off weight, kg: 15000;
The speed of the flight, knots: 100 (~ 185 km / h);
Range of flight, km: 800;
Ceiling, m: 2500;
Aircraft engines: 3xAM-34;
Power on take-off mode, l. with: 3x1200;
Max. excitement when taking off / landing and diving, scores: 4-5;
Underwater speed, knots: 2-3;
Depth of immersion, m: 45;
Power reserve under water, miles: 5-6;
Underwater autonomy, hour: 48;
Power of the rowing motor, l. с .: 10;
Duration of immersion, min: 1,5;
Ascent time, min: 1,8

Article source here (nearly identicle to WIKI too.)
Last edited:


Building Fool-Flying Noob
Reserved - Plans and Build Details

Current Plan Set:
LPL FS - Alpha Plans

Reserved for Build Article:
Last edited:


Old and Bold RC PILOT
It is good to see that you have spent a fair amount of time finding some solutions to the "Foam" buoyancy issue. The next things to consider is the scale required to get the craft to rise and take off in a scale or semi-scale manner.

Personally I would love to see this project fly so please do not take my input as any form of criticism but rather a heads up to outstanding issues.

When re-surfaced the plane will need to sit high enough on the floats to enable taxiing and take off. To facilitate I would assume that a minimum of the top 50% of each float should be above water. Whilst the overall volume Vs displacement was a concern to allow the craft to submerge it is the weight Vs displacement of the floats that is key to take off and taxiing.

Additionally to aid in submerged stability I would suggest that the batteries be mounted in the floats,

The control surfaces can be operated from within the electronics bay, (located centrally), and use pushrods and torque rods to operate the flight controls. Simple rubber boots can be used from the electronics bay and glued and sealed to the metal control/torque rods. This would remove the requirement for individual waterproofing of the servos and the wiring. For submerged depth limit and stability I recommend that the electronics bay be located in the upper portion of the conning tower.

The only real ballast pumping required would be in the floats as the remainder of the structure could be porous or with flood/drain holes.
A possible RC quick solution is to use a system based on how "Air retracts" function but into bladders, instead of retract units.

Underwater propulsion might be simplest if borrowed from a child's toy and modified to suit because low RPM systems are going to be difficult to manufacture from a brushless motor without a reduction gearbox.

Ideally when fully submerged, (completely flooded) the top of the conning tower should still be slightly visible because to fully submerge to neutral bouyancy there is a danger that a slight water leak anywhere could send it to the bottom before you realise that there is a problem.

Like your effort so far! Keep it up!

Have fun!


Toothpick glider kid
Definitely subscribed, I cant wait to see how this turns out. And another thing, if this is going to land, submerge, and take off from water does this mean that they will be adding a water section to Flite Fest? I hope so...


Building Fool-Flying Noob
Going over my foam/ buoyancy calc... 30cmx20cmx0.5cm is 300g not 36g of float... understanding 75% sheet usage factor is about 900g of float + the wtc., Which can be very small if all but the fc or receiver are water proofed. Then we have about 1100-1200g of displacement. :black_eyed:.

All is not lost. Just room for more equipment :p


Skill Collector
This is going to be epic. No matter the final outcome, I applaud you for undertaking the challenge in the way you have - this is going to be one very cool journey to share. :)


Building Fool-Flying Noob
Thanks. I spoke to Bob on the way home. Great guy. It's funny that we independently came to the same conclusion about how to get the submarine action to work. The gist is to waterproof the servos and ESCs, the brushes motors are fine, so that leaves wtc space only for the receiver, small gas pump and a solenoid. We agreed the bloat system for the fuse and wings and pontoons is the way to go. The increased pressure with depth will keep the bags inflating in the proper order like ensure safe vertical breach. Keep it just and use the surfaces to dive. This is a pretty common system setup for Subs. So when signal goes out, or a failure occurs, it will return to the surface. all I need to do is to extend the antenna's to the top periscope with the breathing tube. For bladder inflation, down to the floats.


Well-known member
I hope this means someone is going to install a swimming pool at FF2018? Last year all we needed was an above ground bladder and mother nature would have filled it. :)

I'm genuinely interested in the final outcome, but I still can't believe you'd consider making it sink as well as fly. This is going to be something unlike anything else we've seen.


Building Fool-Flying Noob
It begins!

1.One of the points brought up is to sized the Pontoons to ensure that when full inflated/empty they displace enough water to support the boat high enough in the water to start the engines. clear of water. As of Right now, they are 150 cm^2 x 5.25 cm or 787 ccm totaling 1575g of buoyancy for the floats. This means a craft weighing of 1200g will put the floats ~80% in the water. That's too deep. I will build will need them to be wider. but for now, It's good enough to see if she's airworthy.

Shifted from above post #3

I printed the plans yesterday, readied them for cutting and realized the 34"x 22" plans were printed at 36"x 24". The good news was, it still fits on the DTFB sheets still. I started cutting and got about 2 1/2 of 4 sheets done before realizing I had to quit for the night.
I had a conversation with Bob Martin and it's looking very likely that this craft will be design so with some minor modifications (Like extending your Receiver antenna and waterproofing) all RC enthusiasts can take the radio system they have and build this submersible plane.

Finished the cutouts, and began doing beveling and shaping. Pictures below.


New member
You don't mess around! Great progress already, Matt!

I'll be interested in seeing how much buoyancy that foam board has with a hollow model. And I'm still thinking we'll need to use almost all of the interior volume of the plane as ballast, but we'll have to see what we have to work with once you have the hull completed.

Awesome project and I'm really interested in seeing it through to completion. Hit me up if I can help any more!

Bob Martin
Owner - the Nautilus Drydocks


Building Fool-Flying Noob
Hinges and Stuff

@RCSubGuy - I agree I'm planing on water proofing all the ins and out of the model and dunking it to test the buoyancy.

When I'm inspired... I go to it. It's when I hit unanticipated snags or problems I have to do iterative testing, is where I tend to slow considerably. Knowing this about myself, means i needed to get moving, so when I slow up, there's plenty of time still. Example: I can't get a flying yet sinkable foam model will me diving into fiber glassing/or Carbon Fiber Epoxying. The benefit is if I get this working I have time to play with it, or try another plane. (or design my own Flying Sub!)

Here's the progress I made last night. It doesn't feel like much, but I'm starting to feel like It's a plane. If I'm lucky I'll get it airworthy by Sunday! (if I have enough servos :) ).

8WingBevel and Spar installation.JPG
12SparGlue support.JPG

The Elevator and Rudder are 2 layers of Foam.

The Elevators flaps are done with a Fiberglass reinforced Tape Hinge cut with a 45° bevel on top and bottom I will be embedding a skewer across them and adding a control horn there so they work together.

The Rudders are a skewer post glued into the front half, the receiving hole hollowed out. Glued and setup, then removed the skewer after the glue cooled enough to set, but not to late for it to be stuck, maybe 20-30s. Be sure to clean any glue residue off the hinge post. then reinsert it. To ensure the rudder panel doesn't float off the pin I cut a groove to put the wooden key. the key is only glued to the front. the end result is the panel is free to revolve around the pin, but cannot move vertically. With there is a little grab from the glue from the panel hole it still flops around when the tail is jiggled. a paper collar is an alternate I will try during the rebuild.

Just had a thought... MAC, CG, CoL may not be the SAME as center of Buoyancy. is there such a thing as COB?
While when submerged it shouldn't be a big deal, it will play into how it submerges (not sinks). If the empannage has a higher buoyant density - float force to volume ratio (not sure what that's called) compares to the rest of plane will it alway be lifting the tail submerged, and there by in dive default? it will be interesting to see.


Elite member
Wow, this is a very ambitious project. Hats off to you sir!

It looks like you are off to a great start as well.


Building Fool-Flying Noob
Due to a longer than expected Camping-BSA Training weekend, (and subsequent poor quality sleep) very little was done this weekend.

I did begin networking to find a suitable place to try this as a plane/boat/sub. I think could use the scout camp lake in a pinch. As it's an hour away, I will aim for something closer. the local city lakes are mostly within 5 mi zones of Airports... so a little farm pond is my best bet.

I am about to order some items for my craft here...
I think all I need is a medical-grade mini Air pump and some sort of solenoid to close up the system. Looking at either 12VDC or 5V
I may also need a servo for a hatch... for some reason how it all hooks up is still fuzzy.

Here's my schematic so far:

Hopefully progress picks tonight/tomorrow.

Joe M

If you can get this to work you'll 100% have the coolest plane at any float fly event. I really look forward to seeing this come together.


Old and Bold RC PILOT
I might have missed something so I will ask, sorry if it is already mentioned somewhere but when submerged where do you get the air from to surface the plane? Are you to use a snorkel fitted to the conning tower?

Forget the question! I put my glasses on and found it!

Have fun!
Last edited: