Septimus

[Hotel26]

This is Septimus, a single-rotor express helicopter based on RuBisCO's eminent Compound Speed 2.

First off: all credit to RuBisCO for the original, very beautiful Compound Speed 2, a stock helicopter in which RuBisCO invested countless hours tuning to be the perfect machine, incorporating a state-of-the-art KAL controller.

                                                                                              

The reasons for the "fork" are several but the notable quality of this work is that it can be flown with a single rotary wing plane and no counter-balancing agency other then airflow over the control surfaces and the Reaction Wheels (only 15% of one of those is required usually).

 

Edited June 18, 2021 by Hotel26
Added the video

[Deddly]

Cool

Moved to Spacecraft Exchange as requested. 

[Hotel26]

Septimus Operation Guide
 

Controls

1. [1] Junos
2. [2] R121 turboshaft
3. [3] rotor brake
4. [4] VERT ref
5. [5] ladder
6. [6] RW boost (15% -> 115%)
7. [T/F] HORZ ref
8. [H/N] rotor thrust
9. [K/I] collective
    

Vertical Departure

1. engage brakes
2. start Junos [1]
3. engage rotors [2]
4. disengage rotor brake [3]
5. engage SAS [T]
6. select VERT ref [4]
7. retract ladder [5]
8. run up rotor to 460 rpm [H]
9. reduce rotor thrust to 15% [N]
10. ladder up?  ready to lift-off?
11. add collective [K] to begin a slow but steady ascent
12. [WASD] for joystick controls with [EQ] providing opposite yaw
13. retract gear [G]
14. tap SAS Hold [F] to reselect HORZ ref (revert to normal QWASDE control)
15. lower the nose and fly away
16. lower the collective as flying speed builds "wing" lift
17. >40 m/s, use [N] to zero the rotor thrust and hit [3] to brake the rotors
18. when rotor speed stops (0), you may engage autopilot [P] if you have Atmospheric Autopilot

You may elect to fly without SAS below about 38 m/s, but you will certainly require it exceeding that speed.

Note: if you wish to fly Septimus well, please consider that adverse roll is applied to the aircraft whenever the rotor is being torqued to accelerate the rotor speed.
Therefore, applying heavy power to the R121 is standard when a) the aircraft is parked on the ground, or b) the aircraft has flying speed >= 70 m/s.  Risky at all other times.

The trick (and test of pilot with true grit) comes when approaching the vertical landing.  You must time the approach such that you attain at least 100-150 rpm whilst still moving faster than 70 m/s.  This will likely require 100% torque due to drag.  As you decelerate below this speed, you will be obliged to reduce thrust as close as you can to 15%, understanding that 15% is nominal and not sufficient to keep accelerating the rotor speed while moving quickly through the air.  If you do this right, you will slow through a threshold with a goodly number of turns and be able to still lower rote thrust (to the nominal 15%) and enjoy still steady increasing revolutions due to decreased drag.  Expect to use plenty of port roll input and some assiduous jockeying of pitch, roll & yaw (yup, all three)to precipitously slow the aircraft to take enter into full advantage of still air.

You shouldn't have to use [6] RW boost (15% -> 115%) but it's there to bail you out if you do need it...
 

Vertical Landing

Well, the note above covers the tricky part.  Assuming you've nailed all that finalizing the initial approach:

1. engage SAS [T]
2. disengage autopilot [P] if Atmospheric Autopilot
3. you'll have the Junos idled; rotations >= 200 rpm and heading for 460; rotor thrust at ~15%
4. use the collective [K] to take up the lift deficit as your flying speed diminishes
5. raise the nose above the horizon to bleed off forward speed, controlling your approach over the target
6. it's good to increase the collective as you bring the nose up to "brake" and be ready to let it off as you quickly lower the nose pro-actively
7. expect to be a full three-fingered busy  on the left-hand side of the keyboard controlling the final approach to the hover point
8. if your nerves are fraying, hit [4] for VERT ref and then punch the SAS Radial Out button to let the auto help you settle
9. once over the target and close to stationary, patience and a very gentle touch with QWASDE will be your guide to a sweet touch-down with Mother Terra Firma

Good luck and enjoy!!

 

Note to designers: I found that a terrible "wobble" incurred during hover was due to having Pitch, Yaw & Roll set on the blades.  Canceling that magically smoothed the hover.  (This doesn't seem to be a problem with contra-rotating blades which must cancel each other out...)

 

Enquiries welcome and advice freely given.  Please use this topic to post questions or experiences, if you so desire!

Edited June 18, 2021 by Hotel26