DESIGN ~ Electrotor-SloMo ~ Rotorhead - Blade-P - General

• For Non-autorotative flight.
• See; DESIGN: Electrotor-SloMo ~ Rotor - Disk - No Autorotation vs. Autorotation
• CONCERN: If one of the two independent sources of power was to fail would the remaining source, at probably greater than 50% of total power be able to stop the craft from entering the vortex ring state should the pilot remain in vertical flight for the duration of the descent? Or, could it hold the high power setting for the duration of a descent.
• This has got to be looked into much more thoroughly. See; DESIGN: Electrotor-SloMo ~ Rotor - Disk - No Autorotation vs. Autorotation Also see below.
• To utilize the shape of an existing large propeller since it might have the optimum aerodynamics for vertical flight, and for slow lateral flight.
• This blade is for a weight-shift backpack helicopter that cannot autorotate; due to its extremely large twist and taper.

• Propeller Performance Factors

• Potential Sources for Propeller:
• DE HAVILLAND ~ DHC-7 DASH 7 ~ Diameter 3.43 m (11 ft 3 in).OK (99.5 sq-ft area) [of slow-turning type (1,320 rpm) to reduce noise level. Propeller blades are of GRP, with forged aluminium spars and foam cores.]
• I think that this picture is Dash-7 http://www.hopeaero.ca/jeremiewithprop.jpg - Hamilton Sundstrand's propeller
• The chord may be too large for rotors with 3 blades. Might consider taking the dimensions from a blade and then have the program proportionately reduce the chord and the thickness.
• Its area of 99.5 sq-ft times 2 rotors = 199 sq-ft. If the GW is 300 lbs then the disk loading is 1.5 lb / sq-ft., which is good for foot landing. This is too large a diameter for non-autorotation.
• de Havilland DHC-2 Beaver . Propeller Diameter: 8 ft, 6 in.
• Its area of 56.8 sq-ft times 2 rotors = 113.5 sq-ft. If the GW is 300 lbs then the disk loading is 2.64 lb / sq-ft. This maybe too large a diameter for non-autorotation but maybe ideal for low power in normal flight.
• 3-blade Hartzell - 102inch (paddle prop) 8.5 ft on the turbo version. 650 H.P. TAKE-OFF & 550 H.P. CONTINUOUS
• 2-Bladed, Hamilton Standard, Constant Speed reciprocating engine, 450 hp continuous
• Other aircraft http://www.airliners.net/aircraft-data/

• The Mosquito helicopter has a rotor radius of 9 ft and a disk area of 254.5 ft².
• In a side-by-side configuration this disk area would be equaled by 2 rotors with 6.36 ft radius.

• See; DESIGN: Electrotor-SloMo ~ Rotor - Disk - 2 Blades vs. 3 Blades

• Vortex Ring State:
• A propeller or a rotor blade with ideal twist may not be able to autorotate, at least not in the same direction of rotation as when under power. This may involve compromises, particularly if the rotor was able to get into the vortex ring state while in a vertical descent and be un-able to power out of it.
• This appears to implies that the descent rate of the craft, particularly in vertical flight. Must not exceed more than 50% of the induced velocity.
• Also; "The limits of the vortex ring-state are hovering" Also see Figure 6-8 [Source ~ AH p.126]
• A reduction of torque also results in a nose up pitch on an Intermeshing configuration that has outside-froward rotation. Can there be an audible and visual warning device?
• More importantly, it must be possible to know what the crafts rate of descent is at a given power setting and to know what the induced velocity is at that same power setting. Therefore the controller has to assure that the power setting never drops below this setting. The pilot will apply additional power during the actual touchdown, and then take the power on down, or, switch off this automatic feature when entering ground effect.
• See Autorotation: below.
• Vortex Ring State and Ground Effect:
• "As a former Army helicopter pilot we were trained on the conditions which cause an aircraft to enter a vortex ring state and those that don't. A helicopter can not enter into vortex ring state when it is ground effect. Ground effect directs the rotor wash out and away from the rotor system."
• "As pointed out, VRS does not happen with a helo in ground effect even though the tip vortices are still present."
• Me:~ Ground effect exists when the rotor is within 1/2 a diameter of the ground. For the backpack helicopter during a landing the pilot's feet will likely have touched the ground before the ground effect comes about. This suggests that VRS could exist all the way to the ground.

• Rough assumptions and calculations. In reality, what power setting will be required to maintain a descent rate that is less than that of entering the vortex ring state?
• Played with Access program with limited results.
• Assume that this is based on vertical descent because ideal twist in forward flight will probably not make much difference
• Assume that induced velocity during descent is 13 ft per sec.
• Assume that the maximum descent rate is 50% of induced velocity; giving 6.5 ft per sec = 390 ft per min. Which is not shabby.
• If the [Low Pitch] setting is set for this value then it will not allow the pilot to remove his weight from the craft.
• Perhaps there must be a 2-position, maintain contact switch for the pilot to select [Maximum Descent Rate] or [No Lift]. The [No Lift] is a mechanical stop. On activation the [MDR] the controller will draw power at this pre-set rate.
• Like other aircraft, this craft will have a minimum fuel reserve. This minimum reserve must be placarded at a higher level than that which is need to descend from the AGL limitation.
• See; DESIGN: Electrotor-SloMo ~ Rotor - Disk - No Autorotation vs. Autorotation

• Vertical air velocity sensors (like a Pitot tube).
• The reduction of the empty weight due to the elimination of autorotation capability (i.e. blade characteristics) should well exceed the weigh of this addition.
• There is no reason why the craft should need to fly more than 200-300 feet AGL. This autorotative descent will probably take less than one minute.
• Aerodynamic development and testing will entail putting a remotely controlled craft through every conceivable flight attitude. In other words, trying to put it in an unrecoverable situation and also trying to make the recovery aerodynamically automatic. ~ Lots of fun.
• OTHER: Aerodynamic - General - Autorotation, DESIGN: UniCopter ~ Rotor Disk - Autorotation, DESIGN: SynchroLite ~ Rotor Disk - Autorotation

• For a light gyrocopter; the two propeller blades plus the two rotor blades will sell for approximately $2155.00. [Calculations below]
• For a light twin-rotor weight-shift helicopter; the four rotor blades, which will have a larger diameter and a lower weight than IVO's Magnum blades, will sell for approximately $1360.00. [Calculations below]
• This represents an approximately 30% lower cost for the airfoils.

1. Digitize the coordinates of the selected airplane blade.
2. Reduce the chord (Y-axis) and the thickness (Z-axis) dimensions proportionately. This will retain the profile of the blade at all blade elements (X-axis) and it retains the twist.
3. The span (X-axis) can be adjusted also, if desired.
4. The coding would be transposed for the blades that are to rotate in the opposite direction.
5. This could also be used to produce the coding for any number of different female molds, which will have the same basic characteristics.

1. Female mold only (2 parts).
2. Produce the desired internal bladder.
3. Lay-up Prepreg cloths for blade skin on the lower mold.
4. Lay the partially inflated bladder on top of the plies in the mould.
5. Fold the free plies of cloth over the bladder.
6. Close and clamp the two mold halves together while expanding and then pressurizing the bladder.
7. There will likely be the need for a bleeder ply to remove any trapped air.
8. Heat the cold oil in the bladder to assist with cure, if required.
9. This creates a hollow blade.
10. Alternatively, incorporate a foam core, and heat the female mold if necessary.
11. The bladder may or may not require removal, depending on it makeup etc. A light condom type material could probably remain in the airfoil.

Introduction Page | SynchroLite Home Page | Electrotor Home Page | UniCopter Home Page | Nemesis Home Page | AeroVantage Home Page: