The document proposes a concept for a submersible aircraft that can take off and land on both land and water. It discusses three conceptual designs, considering advantages and disadvantages of each. Key specifications of engines, components, and performance are estimated. Mission profiles involving takeoff from land, cruise, and landing on water are described. Design challenges like drag underwater and on takeoff are analyzed.

1. Submersible Aircraft
Joseph Thomas
0710343E

2. Introduction
A submersible aircraft would combine the key
capabilities of three different platforms:
1) The speed and range of an aircraft
2) The loiter capabilities of a boat
3) The stealth of a submarine

3. Introduction
Things to consider
• The skin thickness needed to resist the external loads.
• The seals for the vents and ports
• Control and stability underwater
• Propulsion and power source underwater
• Take off on the surface
• Submerging from the surface

4. Boat Features
• Flair the angled base of the hull. The shape is
to ensure that the water is swept away from
the main body. The higher the angle the faster
the boat can go.
• Step is a sharp discontinuity just aft of the
COG. Landing on the step breaks the water
and makes for a smooth, long touchdown.

5. Concept 1
Advantages
• Ground effect increases the range that the
aircraft can cover on the water surface.
• The low wing will help in submerging. As the
aircraft partially submerges, the flaps are partially
submerged and can be used to generate down
force in the initial stages of submerging.
• The single engine is positioned high above the
water, with the fuselage partially protecting it
from the spray.
• The elevator will be sensitive with the engine
blowing directly onto it.

6. Concept 1
Disadvantages
• Successful landing is dependent on pilot skill as
there are additional variables to take account of.
• Ground effect can make it difficult to land on
conventional airstrips as the aircraft rides on a
‘cushion of air’.
• The performance of the single engine is critical
importance. There is no alternative on the
occurrence of engine failure.
• There is a high power requirement for the main
engine on water take off for low wing.

7. Concept 2
Advantages
• There is a large amount of power available
for a high rate of climb and sail speed.
• The diversity of landing capabilities makes it
easier for pilots
• The aircraft can sustain flight with one
engine inoperative.
• A higher stall angle will be achieved with the
position of the engine.

8. Concept 2
Disadvantage
• The wing mounted engines will contribute to a
higher parasite drag than concept 1.
• Dual engines will have higher fuel consumption
than a single, more powerful engine.
• There is additional weight associated with an
extra engine.
• The wing loads will be higher and contribute to
higher increase in skin thickness than the tail in
concept 1.

9. Concept 3
Advantages
• Highly streamlined design will operate will
underwater and prove to have a lower true
drag coefficient than what is calculated.
• Ground effect increases the water surface
tactical radius.
• Low wing helps in submerging.
• The width can allow for a longer fuselage
section with a higher number of passengers.

10. Concept 3
Disadvantages
• A low angle of attach must be maintained
during take-off to prevent propeller strike.
This contributes to a high SGA.
• Hull landings can severely damage the
canards.
• The cockpit space will be constricted due to
the ‘structural seat’.
• Novice pilots will struggle with operating the
aircraft to its full potential.

11. Engine
Garrett TPE331-14GR
Power SHP 1120
Length (m) 1.33
Diameter (m) 0.53
SFC (kg/HP/hr) 0.228
Weight (kg) 195.1

12. Secondary Propeller
Shaft Horsepower required 18
Waterline length in feet: 30 feet
Beam at the waterline in feet: 6 feet Pounds per shaft horsepower 1,213
Hull draft in feet (excluding keel): 10 feet required.
Vessel weight in pounds: 11000 lbs Approximate maximum speed 5.3
Engine Horsepower: 24 HP
Shaft HP required for speed 21
Number of engines: 1
Total Engine Horsepower: 24 HP Required prop pitch 20
Engine R.P.M. (max): 1000 RPM
3 blade diameter (inches) 25
Gear Ratio: 1.5:1
Shaft R.P.M. (max): 667 RPM 4 blade diameter (inches) 24
Number of shaft bearings (per
1
shaft): Total horsepower available at the propeller(s): 22.9 HP
Desired speed in Knots: 5 knots Total torque ft/lbs available at the propeller(s): 181 ft/lbs
Estimated speed with existing 24 horsepower: 5.89 Knots
Propeller Size
Number of Diameter
Pitch (inches)
blades (inches)
2 Blade 25.1 X 20.4
3 Blade 23.9 X 20.2
4 Blade 22.5 X 19.8

13. Electric Engine
Power 1.8 KW ≈ 24 HP
Length 0.432 m
Width 0.165
Weight 76.7 kg
Max RPM 1000
Input 144 V
Unit Inverter Battery (one) Battery (11 pack)
Length (m) 0.40 0.120 0.48
Width (m) 0.43 0.190 0.38
Height (m) 0.254 0.130 0.26
Weight (kg) 29.1 4 44
Output 3500 W 540 W-h 5940 W-h

14. Sizing
Wing Loading H Tail V Tail
222
V ht 0.8 0.08
S_ref 20.2
S_ref_ht 2.67 2.07
Cl_cruise 0.353
V_stall AR ass 3.3 3
47.1
AR (assumed) Cr 2.73 1.18
8
b 12.7 Ct 0.82 0.47
Taper (ass) 0.7 b 1.46 2.48
Cr 1.87 MAC 1.94 0.88
Ct 1.31 sweep 0.48 0.22
MAC 1.61
t/c 0.12 0.15
Sweep 20
NACA 0012 0015
t/c 0.12
S_wet 5.21 4.13
NACA 4412

15. Weight Estimation
Mass Nickolai
lb kg
Wing 711.59 322.77
h Tail 121.72 55.21
V Tail 344.35 156.20
Fuselage 1417.65 643.03
Engine 955.02 434.10
Landing Gear 174.91 79.34
Electric Engine 500.00 226.80
Battery 97.00 44.00
Furnishing 554.68 251.60
Air conditioning 18.49 8.39
Miscellaneous 220.46 100.00
Total 2321.43

16. Performance
Component Value
SGR 467.8 m
SGA 396.3m
Stall Speed 49.2 m/s
VMU 47.1 m/s
Top Speed SL 150 kts
Top Speed FL150 160 kts
Top Speed Submerged 5.8 kts
Cdo 0.0196

17. Thrust vs Drag
1600.0 Drag
1400.0 Thrust FL200
1200.0
Thrust SL
1000.0
Drag SL
800.0
600.0
400.0
200.0
0.0
0 20 40 60 80 100 120 140 160 180 200

18. Underwater Drag
10000.0
9000.0 Water drag
engine limit
8000.0
7000.0
6000.0
Drag (kg)
5000.0
4000.0
3000.0
2000.0
1000.0
0.0
0 5 10 Knots 15 20 25

19. Water Take Off
1600 Drag
Drag on take off
1400
Series1
1200 • Wave
Thrust SL • Skin Friction
1000
• Air
800
600
400
200
0
0 50 100 150 200

20. Drag Polar
3.500
Cruise
3.000
Top Speed
Flaps-20 deg
2.500
2.000
Cl
1.500
1.000
0.500
0.000
0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350 0.400
Cd

21. Mission Profile
• Take off from an airfield, and climb to FL150 for cruise, at a speed of
126 m/s.
• Land on the surface of a water body, significantly deeper than 10 m.
The main engines can be run, or the auxiliary power can be used for
this stage, depending on required speed or ambiance.
Before, entering stage three, all ports, vents and hatches must be
sealed. Flood tanks must be filled and the main engine must be
disengaged.
• The secondary power source is used for this stage. The loiter time
depends on the oxygen supply and battery charge, 20 minutes is
recommended.
• Resurfacing, the flood tanks are pumped dry, and seals are opened.
The take off happens under the power of the main engine, as the
secondary propeller is stowed.
• Climb to FL150 for return journey.

22. Fitting
Floor line
Water Tank
Seat with Oxygen tank
Electric engine
Battery
Inverter
Sealed Wall