Originally Posted by
Dora-9
Given that there's some conjecture about the aircraft being in a flat spin - while I've never even sat in a Cirrus, on most aircraft the spin will be flat if the engine remains at high power. Is it possible that, following a pilot incapacitation with no further control inputs, the aircraft stalled with cruise/climb power, departing controlled flight into a flat spin?
A flat spin would typically require a tail heavy centre of gravity outside of the normal operating envelope. I took an old SR22 W&B calculator, entered 80kg for the pilot, 50kg for the 11 year old and 35kg for each child on the rear seats, full tanks. In order to get the CoG just slightly outside of the envelope, rearwards, they would have had to have been carrying around 110kg of baggage in the boot....
Originally Posted by
Runaway Gun
No. Without pilot input, especially full back stick, the aircraft is not even going to stall, let alone spin.
Not true. If the aircraft was flying using a basic autopilot such as the STEC 55x, set on HDG & VS mode, climbing with, say, 700fpm, eventually the autopilot will pull the aircraft into a stall as the engine can no longer generate the power required to sustain the climb, the higher it climbs. In order to keep the commanded climb rate, the autopilot raises the nose in order to continue to climb....hey presto - stall. Depending on the VS set, depends how soon the aircraft will stall - with VS+1000 fpm commanded, it will stall much earlier than, say, VS +300fpm.
However for this to develop into a spin, yaw would have to be present in some form or other, otherwise the nose would just drop and the plane would mush downwards. Stalling a Cirrus with no yaw is relatively benign; because of the cuffed design of the wing, the inboard portion of it stalls first, allowing the outboard area to remain unstalled, meaning the ailerons are still effective; in a Cirrus, you can actually use the ailerons in a stall to keep the wings level.... yes, you're descending rapidly but without yaw, it won't spin - the Cirrus SR2x aircraft were considered the first spin resistant aircraft EASA certified.. External factors such as turbulence might create the yaw required to induce the spin, though....
Modern autopilots such as the Garmin GFC or Avidyne DFC have a safety feature which will trim the nose downwards before stalling the aircraft - unfortunately we don't know what A/P this aircraft had fitted. Other factors which can cause an aircraft to stall without pilot input would be icing, trim runaway...