Event
- Spiral Dive from 150 feet.
- UU April 2009 10:30:00 (exact time to be determined)
- Secondary flying location - UUU
- Very windy, with gusts exceeding 19 knots, changing direction from westerly to, at times, easterly
- Make model and type of A/C to be determined
- All up weight 398g
- New brushless motor just installed (outrunner)
- Make and model and specification of motor to be determined
- Pitch and diameter of propeller to be determined
- Net thrust > 500g
- Slightly (incidental) off centre thrust - about 5 degrees to the left
- Weight and balance modified, tail wait of approximately 15g installed forward of vertical stabiliser
- C of G 25mm aft of leading edge (within limits)
- 11.1v LiPo fully charged
- Radio gear - digital 2.4GHz - DX6
- Mr UU-heli-man
- Mr UU-aero-man-not-too-windy
- Little G was running around, creating a landing hazard which required the PIC to need to look out top and bottom
- Aero configured in hangar
- New brushless and brushless ESC installed - checked out okay
- Motor held onto balsa with drilled screw
- Thrust slightly to the left (5 degrees) due to over pushing the motor onto balsa rod
- C of G moved aft by the application of plasticine weight fore of v. stab.
- Ground check okay
- Controls correct and proper movement
- Controls visually centred
- Full throttle, count "1-2-3-go"
- A/C hand launched by assistant - straight and level launch
- A/C airborne without too much trouble
- The A/C was difficult to handle in the fluky winds, with excessive aileron roll requiring constant correction
- Positioning the A/C was difficult - it was fairly constantly choosing its own path to fly
- Keeping altitude was easy - as excess thrust allowed it to climb near vertical, limited only by the ability to maintain the A/C attitude
- After around 3 minutes, the pilot considered attempting to try and get enough control to check the balancing of the A/C
- at T-10 seconds, the pilot attempted to initiate a down-wind (right to left (east to west)) pass, needing to turn the A/C 180 degrees to initiate the run
- the A/C was at about 100 feet and climbing - on initially 1/2 power
- at T-8 seconds the turn commenced, and additional power was applied (to full power) as the A/C became unmanageable
- the A/C climb at around 45 deg angle of climb to an altitude of around 300 feet at T-5 seconds
- the PIC was aware of the near vertical sun which was full (no clouds obscuring) - and was unable to bring the A/C under any control as it approached the suns direction at about T-4 seconds
- the PIC sheltered one eye and closed the other in order to try and keep visual on the A/C, and be able to pick it up post pass as soon as possible
- the A/C passed over the sun at T-3 seconds, also achieving maximum altitude of 350 feet as power was cut
- at T-2.5 seconds the PIC regained visual on the A/C which was proceeding to the northern outer permitter in with an attitude that was not initially determined
- at T-2.0 seconds the aircraft adopted a nose done, proceeding to vertical nose down attitude, with the PIC still not having positive control
- at T-1.5 seconds the A/C was nose down vertical, accelerating, and exactly on the edge of the boundry, although it appeared to be slightly beyond
- at T-1.0 seconds - at this point the PIC applied full back stick (elevator) - instintively - which only increase the speed - the A/C was in a tight near vertical spiral dive, estimated speed was at least 20 meters per second (70 km/h)
- the actual speed of rotation was not conciously realised until a few seconds later, but it was around two rotations per second
- again, the instinctive maneover to level the wings and pull back - was countered by the knowledge that this had a 50 percent chance of taking the A/C beyond the boundry - as a result - no action was taken
- at T-0.5 seconds - some control action was being applied, but with no response - the A/C's wings were perhaps stalling or some other type of control problem
- at time "T" (-0.0 seconds), the A/C impacted the ground nose first vertical, 5 cm into the boundary (short plants), remaining vertical after impact due to leaning on those same short plants - some 150 meters distant from the PIC
- the throttle remained closed, and the controls were still responsive (rudder, elevator) the ailerons were obviously jamming and did not have much movement
- the A/C initially appeared mostly intact despite the impact speed; however
- on closer inspection, the nose was considerable damaged and bent, and the wings were displaced
- the battery was disconnected
- video of the damage was taken
- The A/C was prepared sufficiently and to the best knowledge available
- The flight should not have taken place due to the nature and speed of the winds
- There should have not been extra people on the field during the test flight
- Being a test flight - the Sun's position in the sky was a factor, before sunrise would be preferable - or during overcoast (nil wind day)
- The aircraft's top speed was quite high, allowing the aircraft to get a long way downrange very quickly - perhaps different propping could improve this situation
This meant the orientation and attitude of the aircraft became ambiguous at difficult to determine quite frequently - It is quite possible the PIC's eyesight "ain't what it used to be" or it is just that the model was faster than what he was used to
- The PIC was unfamiliar with A/C of type - and needed at least extra simulator training before hand
- Incorrect recovery technique was applied, however the mitagating circumstances of loss of control in general, and exceed boundary were an issue
- The model could probably be repaired, with a fair amount of effort
- Rebuild nose mount, and fairing
- Re-set wing position
- Strengthen and straighten bent structural parts
- Paint or indicate on wings unique colours the enable simpler attitute and orientation perception
- Experiment with pitch and prop size to "gear down" the motor, which means greater low speed thrust, at the expense of top speed (which was too fast for the area) - trials and calculations required to do this
- Rebalance and correct control deflections on newly rebuilt model
- Airfield to be large and unobstructed
- No extra personnel or observers on airfield
- Nil wind conditions
- Series of planned exercises to ensure the model is flying correctly
- Initiate landing sequence early, then re-launch
- Low - or clouded Sun if possible
Things to Learn
- Gusty winds not the best for initial flight of a model (including changed setups)
- Practice, train, simulate, and stay current
- More diverse training worthwhile
- If it is your model, don't let some talk you into flying it in gusty wind - they don't know what they are talking about :-)
Terms
- RC - Remote Control
- A/C - Aircraft
- PIC - Pilot in Command
- attitude - the direction the aircraft is pointing (e.g. nose high)
- orientation - the exact relative position of the aircraft with repect to the PIC - e.g. closer (left) wing down, far wing up
- altitude - the height above the ground
- ESC - Electronic Speed Controller
- brushless - no brushes to the commutator
- outrunner - the outside of the motor rotates
- propping - the configuration of the propeller - pitch and diameter
- propeller pitch - how "deep" the cut into the air is, measured in inches
