A132

DESIGN: Electrotor-MicroLite - Control - Flight & Power

Safety in Respect to Loss of Power:

It appears that current small rotorcraft with; no collective, 'absolutely' rigid rotors, 'relatively high' disk loading, and low rotor inertia, must fly within a few feet of the ground, for safety reasons. Also, it can be assumed that these craft would be unsafe at speeds above ?? mph, no mater how close they are to the ground.

In addition, perhaps the collective pitch on these craft is fixed at optimal lift and their rotors could not even sustain autorotation. Does anyone know? [I think that Pegg did a NACA report on this subject many years ago]

My challenge is to provide this type of craft with the ability to fly safely outside of ground effect and with a respectful forward velocity.
The primary means of achieving this is by giving the craft an extremely high assurance level that power can be delivered to the rotors for a fraction of a minute at touch-down.

It seems that dropping the collective on a low inertia rotor when at altitude is more important than raising the collective to squeeze a little extra lift of a low inertia rotor when touching down.

This is the current thinking for a basic microlight;

Loss of power at altitude: ~ Upon loss of all power the 2-position collective will automatically drop to the autorotation position, due to a torque-pitch coupling. The throttle will be located in the 'LOW' position. Just before landing he will flip the Emergency Power Switch to 'ON', which will then allow him to provide emergency power for lift to decrease his descent rate, flare and touchdown.

Loss of power near ground level: ~ When setting up for a conventional landing the pilot will also flip the Emergency Power Switch to 'ON'. This will allow the emergency power to automatically come in to effect, at the current setting of the throttle, plus an announcement warning alarm to sound, if the primary batteries fail.
The above two lines suggest that the Emergency Power Switch should be 'ON' whenever the craft is < xx ft AGL and off when > xx ft.
Perhaps there should even be a separate switch of each emergency power, not a double or triple throw switch?

Weight Shift Flight Control on an 'Absolutely Rigid Rotor: To be eventually moved to appropriate Secondary Grouping

Idea (that has not yet been thought through):

Cyclic Action: The radial (spanwise) center of lift on blades with taper and twist will be closer to the mast than on blades without taper and twist. Now considering two rotors that are identical in all respects except that rotor A has taper and twist while rotor B does not. For a given thrust, I suspect that it will require less effort on the part of the pilot to change the orientation of rotor A than to change the orientation of rotor B.

Steady Forward Flight:

If the above is true then it would also appear that the pilot will be required to use less force to hold the axis of the rotor and the axis of the craft in an unaligned position, such as during steady forward flight. Of course, this force could be trimmed out.
In addition, if the force to hold the axe misalignment is less, then on a rotor with 2 blades the 2P vibration should be less.

The following is an un-though-out idea for improving the controllability of a rotorcraft that uses weight-shift control and rigid rotors. The thinking is that blades with taper and twist might result in easier controllability, and/or, be able to have a slightly larger span (lower disk loading) than straight untwisted blades.

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It is known that the radial (spanwise) center of lift on a blade with taper and twist [blade A] is closer to the mast than it is on an comparable blade without taper and twist [blade B].

If we have two rotors with comparable thrusts and diameters etc. but one has [blade A] and the other has [blade B], the following assumptions should be valid;

~ The rotational inertia in the out-of-plane direction (tipping) will be less on [rotor A] then on [rotor B].
~ The profile drag in the out-of-plane direction (tipping) will be less on [rotor A] then on [rotor B].

Re: Cyclic Action: I suspect that it will require less effort on the part of the pilot to tilt [rotor A] than to tilt [rotor B].

Re: Steady Forward Flight: If the above is true then it would also appear that the pilot will be required to use less force to hold the axis of the rotor off of the axis of the craft during steady forward flight. Of course, this force could be trimmed out.

In addition, if the cyclic stick force to hold steady forward flight is less, then on a rotor with 2 blades then the 2P vibration should also be less.

Pilot Controls:

Other than the pitch, roll and yaw by gimbal and arm movement.

It is intended that twisting the Principal Assembly will change the 'rudder'. The spherical rod end will only allow 10º of twist. What is to be done to eliminate the opposite action during autorotation.

Throttle ~ hand grip
??

Musings Regarding of All Electric Control:

The follow does not consider pitch and roll. It is only some preliminary thoughts on some radical ideas.

Electrical Synchronization of Intermeshing Rotors:

By reading the back-EMFs and/or the use of encoders.

The application of redundancy goes without saying.

This would allow the use of planetary gearing for the MicroLite, which is closer to the desired SloMo.

Concern re Autocollective: A torque that uses lead-lag to change the pitch will have an effect on the coning angle at the hub. This may create a dangerous rotor-rotor clashing.

Yaw control of Intermeshing Rotors:

The objective will be to have one rotor provide more reactant torque to the fuselage while not acting detrimentally to the above synchronization and not causing the craft to roll. Good luck.

By pulsating the power to the rotor that is to impart the greater reactant torque on the airframe. ????

The way-out preliminary thinking is that by providing dampening on the pitch-change where the negative pitch change is slower than the positive pitch change. This make create a situation where .....................??????????

Concern re Autocollective: A torque that uses lead-lag to change the pitch will have an effect on the coning angle at the hub. This may create a dangerous rotor-rotor clashing.

Same Page Different Craft: ~ Electrotor-Simplex ~ Electrotor-SloMo ~ Electrotor-Plus (no page) ~ | ~ SynchroLite ~ UniCopter

Last Revised: December 23, 2009