Jay Carter, Founder & CEO - Electric VTOL...

©2015 CARTER AVIATION TECHNOLOGIES, LLC 1

CARTER AVIATION TECHNOLOGIES An Aerospace Research & Development Company

Jay Carter, Founder & CEO CAFE Electric Aircraft Symposium July 23rd, 2017

SR/C is a trademark of Carter Aviation Technologies, LLC

www.CarterCopters.com Wichita Falls, Texas


A History of Innovation

Built first gyros while still in college with father’s guidance

Led to job with Bell Research & Development

Steam car built by Jay and his father

First car to meet original 1977 emission standards

Could make a cold startup & then drive away in less than 30 seconds

Founded Carter Wind Energy in 1976

Installed wind turbines from Hawaii to United Kingdom to 300 miles north of the Arctic Circle

One of only two U.S. manufacturers to survive the mid ‘80s industry decline


SR/C™ Technology Progression

1994 - 1997 Analysis &

Component Testing

1998 1st Gen

First flight

2005 1st Gen L/D of 7.0

2009 License Agreement with AAI, Multiple Military Concepts

2011 2nd Gen First Flight

Later Demonstrated L/D of 12+

22 years, 22 patents + 5 pending 11 key technical challenges overcome Proven technology with real flight test

1994 Company founded

2013-2014 DARPA TERN

Won contract over 5 majors

2017 Find a Manufacturing

Partner and Begin Commercial Development

http://www.suasnews.com/wp-content/uploads/2011/03/cartercopter.jpg


SR/C™ Technology Progression

Quiet Jump Takeoff & Flyover at 600 ft agl

Video also available on YouTube: https://www.youtube.com/watch?v=_VxOC7xtfRM

https://www.youtube.com/watch?v=_VxOC7xtfRM

https://www.youtube.com/watch?v=_VxOC7xtfRM


SR/C vs. Fixed Wing

• SR/C rotor very low drag by being slowed

• SR/C wing very small because rotor supports aircraft at low speeds – wing can be sized for cruise

• Fixed-wing wing must be sized for low speed/landing

• SR/C slowed rotor & small wing equivalent to fixed-wing’s larger wing

0

100

200

300

400

500

600

0 100 200 300 400

Pro

file

HP

Rotor RPM

Profile HP vs. Rotor RPM, PAV Rotor @ 250 kts @ SL

HPo - Full

HPo - Rot Only

299

155 54

5.7

Drag per WADC TR 55-410:

550

6.418 0

230

RAC

HPbD

O


SR/C Electric Air Taxi Ø34’

36’ 54” Cabin Width


SR/C Electric Air Taxi– Features 10’ diameter scimitar

tail prop rotates to provide counter torque for hover or thrust for

forward flight

Slowed rotor enables high speed forward

flight, low drag, low tip speed/noise, no

retreating blade stall

High aspect ratio wing with area optimized for

cruise efficiency

Simple, light, structurally efficient

wing with no need for high lift devices

Extreme energy absorbing fail safe landing gear up to 30 ft/s improves

landing safety

High inertia, low disc loaded rotor acts as

built-in parachute, but safer because it works

at any altitude / speed, and provides directional control

Lightweight, low profile, streamlined tilting hub greatly reduces drag. No spindle, spindle

housing, bearings or lead-lag hinges

Tall, soft mast isolates airframe from rotor

vibration for fixed-wing smoothness

Mechanical flight control linkages to

optional pilot in parallel with actuators for true

redundancy

Battery pack in nose to balance tail weight

Tilting mast controls aircraft pitch at low

speeds & rotor rpm for high cruise efficiency

at high speeds


0

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200

0 200 400 600 800 1000

Ran

ge, m

iles

Payload, lbs

Range at 175 mph vs. Payload for Various Hover Tip Speeds

600 ft/s

550 ft/s

500 ft/s

450 ft/s

1950

2000

2050

2100

2150

2200

2250

400 450 500 550 600 650 700

Emp

ty W

eig

ht,

lbs

Rotor Hover Tip Speed, ft/s

Empty Wt (w/o batteries) vs. Rotor Hover Tip Speed

Performance Parameters

Drag coefficients based on actual achieved data, not expected improvements 3200 lb empty weight with batteries 4000 lb max gross weight (800 lb max payload) 300 W-hr/kg battery energy density Assumed margin for 0.5 Empty Weight Fraction at 600 ft/s tip speed Mission: 30 sec HOGE for takeoff, Climb at Vy to 5k ft, Cruise at 175 mph,

Descend at Vy, 2 min HOGE at landing (no reserve)

Figure 1 Figure 2

D=46 miles 159 miles

113 miles D=213 lbs

2213 lbs

2000 lbs

Note: 150 mph cruise will extend range by ~10% at 800 lb payload


Air Taxi Concept Comparison

• Compared three different configurations • SR/C • Hex Tilt Rotor • ‘T’ Tilt Rotor

• Used common assumptions and methods for all three concepts

• Based drag coefficients and parameters on measured flight data from PAV

SR/C

Hex Tilt Rotor

‘T’ Tilt Rotor

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4

6

8

10

12

14

0 50 100 150 200 250

L/D

IAS, mph

Carter PAV L/D vs. IAS

Meas'd

Model

Actual Measured Flight Data Note: Data scatter mostly attributable to gathering data when developing rotor rpm / mast control algorithms and varying rotor rpm considerably


Analysis Methods & Assumptions

Parameter Assumptions

Gross Weight 4000 lbs

Pilot/Pax Weight 200 lbs per person

4 people max

Empty Weight Calc’d with same method for all – modified Raymer

Battery & Drive Efficiency 0.92

Useable Battery Capacity 80%

(top 10% unuseable with rapid charge, bottom 10% unuseable to avoid current spike)

Motor + Inverter Weight Scaled Linearly with Max Continuous Power

0.4 lb/HP Assumed motor could be overloaded 1.87x for 30 sec for OEI

Wiring Weight Limited current to 40 amp per wire, running multiple wires per

leg to reach full current required. Per N.E.C., used AWG-10 with Class C Insulator

Drag Coefficients Used same coefficients on all concepts & appropriately scaled misc drags as derived from calibrating model to actual flight

data from PAV

Hover Hover Out of Ground Effect (HOGE) at 6k ft with 1.1x margin

Typical Mission 30 sec hover, climb, cruise, descent, 30 sec hover

Planning Mission 120 sec hover, climb, cruise, descent, 120 sec hover +Reserve: 120 sec hover, 2nm divert, 120 sed hover


Common Footprint

‘T’ TR Hex TR SR/C

34

’ wid

th

Rotor Area, ft² 144.9 791.5 907.9

Disc Loading, lb/ft² 27.6 5.1 4.4

Total Hover HP 774.0 368.4 424.0

30 sec OEI HP 1869.6 467.8 N/A

Cruise HP at 175 mph 240 240 207

Total Installed Cont HP 1099.2 390.1 612.8

• Footprint driven by interface with vertiports • If certain size footprint can be justified, justification is

applicable to all technologies • Single Rotor SR/C & Hex Tilt Rotor have similar disc

loadings • ‘T’ tilt rotor has very high disc loading

• ‘T’ TR Rotor Area only includes 4 lifting rotors (tails rotors for trim control only) • SR/C Total Hover HP includes tail rotor power to counter torque • All Hover HPs include 10% lift margin

39 ft

34

ft


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0.6

0.8

1

1.2

1.4

0 200 400 600 800 1000

mile

/ k

W-h

r

Payload, lbs

Mileage vs. Payload

SR/C - 40 ft

SR/C - 37 ft

SR/C - 34 ft

Hex TR - 40 ft

Hex TR - 37 ft

Hex TR - 34 ft

'T' TR - 40 ft

'T' TR - 37 ft

'T' TR - 34 ft

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0 200 400 600 800 1000

Ran

ge, m

iles

Payload, lbs

Range vs. Payload

SR/C - 40 ft

SR/C - 37 ft

SR/C - 34 ft

Hex TR - 40 ft

Hex TR - 37 ft

Hex TR - 34 ft

'T' TR - 40 ft

'T' TR - 37 ft

'T' TR - 34 ft

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L/D

True Airspeed, mph

L/D vs. Airspeed

SR/C - 40 ft

SR/C - 37 ft

SR/C - 34 ft

Hex TR - 40 ft

Hex TR - 37 ft

Hex TR - 34 ft

'T' TR - 40 ft

'T' TR - 37 ft

'T' TR - 34 ft

Comparison Preliminary Results • ‘T’ Tilt Rotor has very high HP required due to disk loading – higher empty weight for installed HP • SR/C has better L/D @ 175 mph due to smaller wings & less wetted area from prop spinners,

fuselage, & no LG sponsons

1,700

1,750

1,800

1,850

1,900

1,950

2,000

2,050

2,100

32 34 36 38 40 42

Emp

ty W

eig

ht,

Exc

lud

ing

Bat

teri

es,

lb

Overall Width, ft

Empty Weight vs. Width

SR/C

Hex TR

T TR


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180

SR/C (123 mile) Hex TR (110 mile) 'T' TR (49 mile)

Ene

rgy,

kW

-hr

Useable Energy Budget, 800 lb payload, 34' width

R3. Reserve 2 min HOGE

R2. 2 nm reserve at best endurance

R1. Reserve 2 min HOGE

P1. 90 sec + 90 sec add'l HOGE for planning

5. 30 sec HOGE

4. Descend to Ldg Altitude

3. Cruise at 5000 at 175 mph

2. Climb at Max ROC to Cruise Alt

1. 30 sec HOGE

Comparison Preliminary Results

• SR/C has farthest range with least energy used in typical mission, due to better L/D at 175 mph

• ‘T’ Tilt rotor has low useable energy because of high empty weight fraction. Has low percentage of energy available for cruise because of high HOGE power requirements for planning / reserve.

Typical Mission

Add’l HOGE for Planning

Reserve


• Extreme energy absorbing – 24” stroke for descent rates up to 24 ft/s at touchdown

• Responds to impact speed for near constant deceleration across full throw of gear

• No rebound – no bouncing • Proven technology – used on all Carter

prototypes • Lightweight due to efficient energy

absorption

PAV Single Strut Design

Extreme Energy Absorbing Landing Gear

Energy Absorbing Cylinder

Main Gear Trailing Arm

Torque Tube

Automatic Metering Valve

Belleville Stackup to control valve

to keep pressure on piston near constant based

on impact velocity

Air Over Hydraulic for

Energy Absorption

Hydraulic Pressure in

Lower Cylinder for Gear Retract

Carter Smart Strut


Energy Absorbing Landing Gear Video

Video also available on YouTube: https://www.youtube.com/watch?v=MntCeJRl2YE

https://www.youtube.com/watch?v=MntCeJRl2YE

https://www.youtube.com/watch?v=MntCeJRl2YE


Energy Absorbing Landing Gear

0

510

1520

253035

40

45505560

657075

8085

9095

100

0 0.5 1 1.5 2Time (s)

Pe

rce

nta

ge

of

Ma

x

Piston position (8.44" max)

Valve position (.5" max)

Pressure Top (3000 psi max)

Pressure Bottom (3000 psi max)

Note near constant pressure over full stroke

Data from drop test shown in previous slide


Carter Scimitar Propeller • Highly swept to reduce apparent Mach

number – Allows higher CL’s, faster tip speeds, & thicker

airfoils – Swept tip reduces noise

• Twist a compromise between high speed cruise & static/climb

• Lightweight composites 1/2 to 1/3 the weight of conventional designs

• 100” diameter prop shown weighs 42 lb • Tested at Mach 1 for cumulative 10 minutes

• Wide chord – blade not stalled • Spinner nearly flat at prop root

– Reduces decreasing pressure gradient, keeping good airflow on prop root

• Cruise efficiencies of 90+% • Static/climb efficiencies on order of 30%

better than conventional designs


Scimitar Propeller – Bearingless Design

• Pitch change accomplished by twisting the spar

• Eliminates spindle, spindle housing, and bearings used on conventional propeller – simple & lightweight

• Similar design used on Carter rotors which further eliminates lead/lag and coning hinges

Video also available on YouTube: https://www.youtube.com/watch?v=scrXVfwJ7hY

https://www.youtube.com/watch?v=scrXVfwJ7hY

https://www.youtube.com/watch?v=scrXVfwJ7hY


CARTER AVIATION TECHNOLOGIES An Aerospace Research & Development Company

Jay Carter, Founder & CEO CAFE Electric Aircraft Symposium July 23rd, 2017

SR/C is a trademark of Carter Aviation Technologies, LLC

www.CarterCopters.com Wichita Falls, Texas


Backup Slides


Mission Definition

• Using same typical & planning missions as McDonald and German*

• Typical mission for operating cost only requires 30 sec hover for T.O. & landing

• Worst case mission for planning (i.e. charge required before taking off to fly a given mission) requires 120 sec T.O. & landing for given mission + 120 sec T.O. & landing for reserve + 2 nm reserve cruise

• For sizing, assuming 4 min continuous hover

*McDonald, R. A., German, B.J., “eVTOL Energy Needs for Uber Elevate,” Uber Elevate Summit, Dallas, TX, April 2017.


Cruise Performance Model

• Analysis conducted with Carter’s proprietary cruise analysis model • For SR/C, developed mainly for cruise when rotor is unloaded

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0 50 100 150 200 250

L/D

IAS, mph

Carter PAV L/D vs. IAS

Meas'd

Model

Note: Data scatter mostly attributable to gathering data when developing rotor rpm / mast control algorithms and varying rotor rpm considerably

• Model calibrated to measured flight data for PAV. Inputs were scaled appropriately for these concepts. • Had to estimate drag contributions

from different elements, since the aircraft is only instrumented to measure overall thrust*

• Interference & separation drags can account for up to ~1/2 of total aircraft drag, and must be accounted for to allow accurate L/D prediction (based on flight test experience by Carter and Bell Helicopter / Ken Wernicke)

• Air taxi analysis breaks flight into short segments, incorporating climb, descent, and reserves

* Overall drag is calculated based on thrust adjusted for rate of climb/descent – report with methods is available


Battery Assumptions

• Using same rationale as McDonald and German* for useable battery capacity • Top 10% & Bottom 10%

of capacity inaccessible

• 80% capacity accessible

• Ignoring internal resistance losses for this analysis

Ignored for this analysis

*McDonald, R. A., German, B.J., “eVTOL Energy Needs for Uber Elevate,” Uber Elevate Summit, Dallas, TX, April 2017.

DOD = Depth of Discharge


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120

1 1.5 2 2.5 3

Tim

e, s

ec

I / I_rated

Thermal Limit assuming 90 sec @ 1.5x

Motor Overload Capacity • Overload capacity very dependent on specific motor – see examples below from various

sources (only shown to illustrate behavior – these aren’t the motors being used)

• Model with a simple empirical curve that mimics those trends, where C is a constant

𝑇𝑖𝑚𝑒 = 𝐶

𝐼𝐼𝑟𝑎𝑡𝑒𝑑

− 12

• Based on text in ‘Uber Elevate’, assume a motor that can be overloaded 1.5x for 90 seconds (paper stated 1–2 min). Matching above formula to that data point, C = 22.5

t, sec I/Ir 15 2.22

30 1.87 45 1.71

60 1.61 90 1.50

120 1.43

240 1.31 480 1.22

1.87x for 30 sec OEI

1.31x for 4 min HOGE

Data from manufacturer needed to improve this estimate


Empty Weight Estimation

• Weight estimate for all concepts used same methodology

• Structures & Equipment Groups based on method in Chapter 15 of Raymer, Daniel P: Aircraft Design: A Conceptual Approach • Structures weights multiplied by 0.50 to reflect gains from carbon-

composite construction, with the exception of tilt rotor wings, which were multiplied by 0.625 to reflect the higher bending moments due to carrying lift from prop/rotor

• Landing Gear based on historical Carter data, not Raymer's method (same for all aircraft)

• Propeller weights based on historical Carter data

• All Equipment Group weights from Raymer included. Even if the system per se wasn’t in the aircraft, the functions it would have done must still be performed by another system, so the weight must still be accounted for (e.g. hydraulics)

• All other weights based on best engineering practices and judgment


Prop-Rotor Performance

• Conceptual design using a blade element model validated through previous Carter propellers – calculates FOM & efficiency • Includes induced velocity • Airfoils design by John Roncz • Uses CL & CD vs. alpha lookup tables for -20° < α < +20° • Models CL & CD as sine functions for α < -20° or +20° < α • Includes simple estimation of critical Mach & drag divergence Mach (Mcr &

Mdd) based on CL, & increases CD accordingly

• Completed for both tilt rotor configurations (substantially different operating parameters due to disc loading)

• Different flight regimes in hover and cruise make prop-rotor less efficient than a conventional propeller

• Varied prop-rotor planform area to shift optimization from static (hover) performance to cruise performance

• Requires very low RPMs in cruise for best efficiency – only possible with electric motors

(Results shown next slide)


Hover Cruise Airspeed 0 175 mph RPM 1690 267 ΩR 600 ft/s 95 ft/s HP per prop 215 HP 34 HP Dia 81.5” 81.5” Spinner 15” 15”

0.80

0.82

0.84

0.86

0.88

0.90

0.92

0.94

0.96

0.98

1.00

0.64 0.66 0.68 0.70 0.72 0.74 0.76 0.78 0.80 0.82 0.84 0.86 0.88 0.90

FOM

-cr

uis

e

FOM - static

0.80

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1.00

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FOM

-cr

uis

e

FOM - static

Prop-Rotor Performance

Hover Cruise Airspeed 0 175 mph RPM 820 422 ΩR 600 ft/s 310 ft/s HP per prop 66 HP 34 HP Dia 168” 168” Spinner 15” 15”

Hex Tilt Rotor

‘T’ Tilt Rotor

Note different x-scales

• Cruise RPM is ratioed by HPcruise/HPhover, assuming constant torque from motor – results in very low cruise rpm, especially for ‘T’ Tilt Rotor

• ‘T’ tilt rotor can achieve higher static FOM, but because of very high disk loading, actual HP requirement is still much higher


Single Rotor SR/C Hover Performance

• Using slightly modified method from WADC TR 55-410*

• Rotor Induced HP:

Where

HPih = Induced horsepower in a hover W = weight LWH = Wing, fuselage, & horizontal stabilizer downforce in a hover A = Disk Area ρ = density ρo = density at standard sea level

• Rotor Profile HP:

Where HPo = Profile horsepower σ = Solidity ΩR = Tip speed µ = Advance ratio fpr = profile correction factor

• Tail Rotor HP: *Foster, R. D., “A Rapid Performance Prediction Method for Compound Type Rotorcraft,” WADC TR 55-410, 1957.

aHorStabArepAreaFuselageToWingAreaaleFactorPlanformScgDiskLoadinL

A

LWLWHP

H

H

H

W

o

W

Wih

03.0

5506.418

23

o

prDb

o

o fRACHP

o

dia

k

T

HP

1

2

3


• Input from Ken Wernicke • Former program technical manager of all Bell helicopter’s tilt

rotor programs from the XV-15 through the V-22 (now retired)

• Tilt rotors have a special consideration for avoiding stall during the transition between partial rotor supported flight and full lift on the wings • Wing must be sized with appropriate margin.

• For 175 mph cruise, wing must support aircraft at 125 mph

• SR/C – rotor is already in autorotation and can take over and provide the lift required to prevent wing stall • For 175 mph cruise, wing must support aircraft at 150 mph

Wing Sizing


Wing Sizing Concern

• Wing Sizing / Structural Integrity • Required wing area combined with high wing spans yields very

high aspect ratios

• High aspect ratio a concern for tilt rotors with prop-rotors mounted near wing tips

AR with 34’ span

AR with 37’ span AR with 40’ span

SR/C (S = 63 ft²) 18.4 21.7 25.4

Hex Tilt Rotor (S_main = 68 ft²)* 17.0 20.1 23.5

‘T’ Tilt Rotor (S = 83 ft²) 13.9 16.4 19.2

*Note, Hex Tilt Rotor has 3 wings. Fore & aft wings provide additional area

Plan to do structural analysis to see if this will be an issue / how it will affect wing weight compared to historical trends from Raymer


Electric Air Taxi SR/C Concept I


Electric Air Taxi SR/C Concept I – Features

Battery pack in nose to balance tail

weight

Scimitar prop for high cruise

efficiency & high static thrust

Tail prop rotates to provide counter torque for hover, or thrust for

forward flight

Long tail boom reduces tail rotor required HP in hover, also reduces hor

stab area

High speed & fixed wing smoothness

from SR/C technology


Component Weight Estimation (lbs) - CC-31A Hovering SR/C Concept I

Gross Weight 34 37 40 Gross Weight 34 37 40

Structures Group Total Before Margins, no batteries

W_wing 137.5 152.2 167.1 Total Empty Weight Before Margin 1,588.1 1,585.5 1,587.0

W_horizontal tail 8.9 8.9 8.9 Empty Weight Fraction Before Margin 0.397 0.396 0.397

W_vertical tail 5.9 5.9 5.9

W_fuselage 136.0 136.0 136.0 Margin

W_main landing gear** 111.3 111.3 111.3 Margin % of Empty Weight 0.100 0.100 0.100

W_nose landing gear** 27.8 27.8 27.8 Margin, lbs 158.8 158.5 158.7

Total Structural 427.5 442.1 457.1

Total Empty Weight, no batteries

Propulsion Group Total Empty Weight Including Margin 1,746.9 1,744.0 1,745.7

W_motors+inverters 245.1 228.3 214.8 Empty Weight Fraction Including

Margin

0.437 0.436 0.436

W_wiring 10.3 9.6 9.0 W_prop 93.4 91.2 89.5 Batteries

Total Propulsion 348.8 329.0 313.3 Battery Weight 1,453.1 1,456.0 1,454.3

Empty Weight, with batteries 3,200.0 3,200.0 3,200.0

Equipment Group

W_flight controls 78.1 80.6 83.0 Other Weight W_hydraulics 4.0 4.0 4.0 Unusable Fuel 0.0 0.0 0.0

W_electrical 118.5 118.5 118.5 Oil 0.0 0.0 0.0

W_avionics 81.4 81.4 81.4 Oxygen 0.0 0.0 0.0

W_furnishings 167.8 167.8 167.8 Total Additions 0.0 0.0 0.0

W_air conditioning & anti ice 95.4 95.4 95.4

Total Equipment 545.3 547.8 550.2 Basic Weight 3,200.0 3,200.0 3,200.0

SR/C Unique Elements Gross Weight Rotor 200.0 200.0 200.0 Crew & Pax 800.0 800.0 800.0

Rotor Drive (Mechanical Only) 56.5 56.5 56.5 Gross Weight 4,000.0 4,000.0 4,000.0

Tail Rotor Pivot Mechanism 10.0 10.0 10.0 Total SR/C Elements 266.5 266.5 266.5

Structures & Equipment Groups based on method in Chapter 15 of Raymer, Daniel P: Aircraft Design: A Conceptual Approach Structures weights multiplied by 50% to reflect gains from carbon-composite construction Landing Gear based on historical Carter data, not Raymer's method. Includes hydraulic pumps to raise/lower gear W_hydraulics included to account for traditionally hydraulic systems, even though most of those will be electric on this aircraft All other weights based on best engineering practices and judgment

Electric Air Taxi SR/C Concept – Weight

Increasing structural weight from high aspect ratio wing offset by reduced motor weight due to lower hover power requirement


Electric Air Taxi Hex Tilt Rotor Concept


Electric Air Taxi Hex Tilt Rotor – Features

Lift sharing for 3 lifting surfaces optimized for

lowest possible induced drag for configuration

Distributed Electric Propulsion (DEP) allows multiple rotors without weight & complexity of

gearboxes & cross shafts

Battery packs distributed along length of aircraft for reduced wire run

lengths

Carter propeller technology for light

weight & best compromise between hover & cruise thrust


Motor Sizing for OEI Hover • Sized motors to maintain hover even if one motor fails (One Engine Inoperative – OEI)

• Must maintain balance around CG, not just total lift

• Two minimization strategies • Minimize total horsepower while hovering • Minimize horsepower increase of each individual

motor – results in lowest installed horsepower

• Solved with iterative solver to find min HP solutions

Baseline – normal hover

1L Fail, Min Total HP

1L Fail, Min Installed

1L Lift, lbs 682.23 0.00 0.00

1L Preq'd, HP 57.13 0.00 0.00

1L HP / HP Baseline 1.00 0.00 0.00

1R Lift, lbs 682.23 1070.24 988.89

1R Preq'd, HP 57.13 112.25 99.69

1R HP / HP Baseline 1.00 1.96 1.75

2L Lift, lbs 835.54 1404.31 1211.11

2L Preq'd, HP 69.96 152.45 122.10

2L HP / HP Baseline 1.00 2.18 1.75

2R Lift, lbs 835.54 808.04 1211.11

2R Preq'd, HP 69.96 66.54 122.10

2R HP / HP Baseline 1.00 0.95 1.75

3L Lift, lbs 682.23 705.93 988.89

3L Preq'd, HP 57.13 60.13 99.69

3L HP / HP Baseline 1.00 1.05 1.75

3R Lift, lbs 682.23 411.48 0.00

3R Preq'd, HP 57.13 26.76 0.00

3R HP / HP Baseline 1.00 0.47 0.00

Total Lift, lbs 4400.00 4400.00 4400.00

Total HP Req’d 368.44 418.12 443.58

Max HP / HP Baseline 1.00 2.18 1.75

Example Case – Fail front left rotor • Min Total HP Strategy – keeps all remaining rotors providing lift.

Total HP = 418.12, but rotor 2L must go to 2.18x the baseline (to balance moments about CG)

• Min Installed HP Strategy – Drops opposite rotor (rear right). Total HP = 443.58, but 2L only must go to 1.75x the baseline

2L 2R

1L 1R

3L 3R

1L


Motor Sizing for OEI Hover

Small Rotor Motor Failure Large Rotor Motor Failure

Failed Rotor

Reduce to zero

power

Increase power to remaining

rotors

Failed Rotor

Reduce to zero

power

Increase power to remaining

rotors

Motor HP Req’d (4000 lb GW, 1.1 margin)

Normal Hover

Small Rotor Failure

Main Rotor Failure

Main Rotor HP Req’d (each) 70.7 122.6 NA

Small Rotor HP Req’d (each) 56.4 97.7 117.0

• Min installed power solutions will give best empty weight fraction / most battery capacity

• Summary of min installed power solutions:


Hex Tilt Rotor – Weight

Component Weight Estimation (lbs) - CC-31C Hex Tilt Rotor

Overall Width 34 37 40 Overall Width 34 37 40


W_wings 189.6 193.4 208.1 Total Empty Weight Before Margin 1,587.3 1,573.5 1,572.9









W_motors+inverters 156.0 144.2 134.0 Empty Weight Fraction Including Margin 0.436 0.433 0.433

W_wiring 5.2 5.0 4.4 W_props 287.2 278.9 271.8 Batteries Total Propulsion 448.5 428.1 410.2 Battery Weight 1,454.0 1,469.2 1,469.8


Equipment Group W_flight controls 86.4 89.1 91.7 Other Weight W_hydraulics 4.0 4.0 4.0 Unusable Fuel 0.0 0.0 0.0

W_electrical 118.5 118.5 118.5 Oil 0.0 0.0 0.0



W_air conditioning & anti ice 95.4 95.4 95.4 Total Equipment 553.6 556.3 558.9 Basic Weight 3,200.0 3,200.0 3,200.0

Other Systems Gross Weight BRS 100.0 100.0 100.0 Crew & Pax 800.0 800.0 800.0

Wing Tilt Mechanism 30.0 30.0 30.0 Gross Weight 4,000.0 4,000.0 4,000.0

Total Other Elements 130.0 130.0 130.0



‘T’ Tilt Rotor


Motor Sizing for OEI Hover • Sized motors to maintain hover even if one motor fails (One Engine Inoperative – OEI)

• Must maintain balance around CG, not just total lift

• To keep motors as light as possible (min empty weight), minimize power increase for each motor (not total power) – strategy depends on which rotor fails

Inboard Rotor Motor Failure Failed Rotor

Tail Rotors don’t provide significant lift

Motor HP Req’d (34’ overall width, 1.1 margin)

Normal Hover

Inboard Rotor Failure

Outboard Rotor Failure

Inboard Rotor HP Req’d (L / R) 194 / 194 Fail / 388 547 / 547

Outboard Rotor HP Req’d (L / R) 194 / 194 388 / 144 Fail / 0

Decrease power, but not to zero

Outboard Rotor Motor Failure Failed Rotor

Increase power

Decrease to zero power

Tail Rotors don’t provide significant lift

Increase power


‘T’ Tilt Rotor – Weight

Component Weight Estimation (lbs) - CC-31F 'T' Tilt Rotor

Overall Width 34 37 40 Overall Width 34 37 40


W_wing 176.4 195.2 214.4 Total Empty Weight Before Margin 1,875.7 1,830.9 1,818.1









W_motors+inverters 439.7 392.8 365.7 Empty Weight Fraction Including Margin 0.516 0.503 0.500

W_wiring 26.8 23.8 22.0 W_prop 262.4 245.8 240.2 Batteries Total Propulsion 728.9 662.4 627.9 Battery Weight 1,136.7 1,186.0 1,200.1


Equipment Group W_flight controls 86.4 89.1 91.7 Other Weight W_hydraulics 4.0 4.0 4.0 Unusable Fuel 0.0 0.0 0.0

W_electrical 118.5 118.5 118.5 Oil 0.0 0.0 0.0



W_air conditioning & anti ice 95.4 95.4 95.4 Total Equipment 553.6 556.3 558.9 Basic Weight 3,200.0 3,200.0 3,200.0

SR/C Unique Elements Gross Weight BRS 100.0 100.0 100.0 Crew & Pax 800.0 800.0 800.0

Wing Tilt Mechanism 30.0 30.0 30.0 Gross Weight 4,000.0 4,000.0 4,000.0

Total SR/C Elements 130.0 130.0 130.0


Date post:	29-May-2020
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Jay Carter, Founder & CEO - Electric VTOL...

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