Video: Skydive King Air 90 Stall/Spin
Posted: Thu Nov 04, 2021 2:58 am
From a Facebook post about it.
Aircraft Stall Captured by Skydiver
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Incident info released for general information / educational purposes to the aviation community by videographer Bernard Janse van Rensburg, with the full knowledge of the drop zone operations.
-Skydive Mosselbay, South Africa
-14 Oct 2021, 18h00
-Beechcraft C90 King Air
-Pilot +15 pax. All pax are fully qualified skydivers
-Jump run altitude 16000’ AGL
-6 skydivers in the ‘float’ position outside of the aircraft, including the videographer
-All known protocols of the aircraft type were understood, practiced and exercised by the skydivers
-This was the second load of a planned 20x jump event
VIDEOGRAPHER's PERSPECTIVE:
We turned to jump run overhead spectacular cloud / sunset scenery.
The aircraft was trimmed up for the exit procedure. We opened the door and began the climb out. As is normal, the skydive team was fully focused on achieving correct positioning and exit timing.
This intense focus on task resulted in many of the skydivers missing the tell-tale signs of imminent stall.
[Note: (1) the tell-tale signs manifest for only a very short period, so one has to be tuned into them to pick them up (2) such incidents are extremely rare meaning that more than 70% of this team had never experienced such an incident before and thus could not interpret the tell-tales]
From videographer exit position (outside, most tail-ward end of the jumper line) I felt the plane 'slip' once and then twice after which I knew something was wrong and decided to let go of the now banking aircraft.
This all happened inside of just a few seconds.
Those on the outside of the door and immediately inside of the door followed.
With 9 of us initially in the sky there were still 5 skydivers inside of the aircraft. The moment was surreal and I could not believe what I was seeing. Everything happened in slow-motion and I remember thinking 'am I really seeing the plane spinning nose down next to us'. After the spin the aircraft started to veer underneath us but luckily did not make contact. As the aircraft started to recover from the stall (still unstable) one further skydiver exited, leaving 4 skydivers and the pilot in the aircraft.
After I was satisfied that the aircraft had recovered (it is a fascinating and unusual thing to see your jump aircraft below you in freefall), I searched the sky for my team and found them building the pre-planned formations in a safe and normal manner.
PILOT's PERSPECTIVE:
1. The aircraft was inspected and is undamaged.
2. The jump run procedure entails setting flaps 60-80 and bringing back the left engine to flight idle. We also bring the left prop back to full coarse to minimize disking of the prop. This is to enable the jumpers to egress onto the outside step, which would otherwise be difficult due to the prop & thrust blast from the left engine. There is also the added danger of the blast pushing jumpers into the left elevator. Power is kept on the right engine to maintain altitude during the jump run, which typically takes 60 seconds. A fair amount of right rudder is required to fly a straight line in this configuration. Pilot to maintain 95-90 kts IAS.
3. The stall and subsequent spin happened when we allowed too many jumpers on the outside step, causing an aft center of gravity and excessive blocking of the airflow to the left horizontal stabilizer. The nose then pitched up beyond the controllability of the elevator.
4. I anticipated the stall when I hit the elevator stop. As the wing came over, I moved the right engine power and prop levers back to the flight idle position, thereby neutralizing the engine effect from both engines, centralized the ailerons and applied full right rudder (rudder was already in quite deep in at this point). The aircraft behaved very well, and the recovery was surprisingly easy. I pulled out as gently as possible as I did not want to stress the airframe. There was some additional instability when I pulled out of the dive and pushed the throttles forward to power up, as the one engine spooled up much quicker than the other and caused another asymmetrical moment. The flaps may have inadvertently helped to keep the airspeed low. AIS showed 140kts when I pulled out.
5. The incident was reported to CAA within 24 hours. They investigated (including a visit to our hangar) and they seem to be happy that the aircraft was operated and flown within its STC.
6. In future, no more than 5 jumpers will be allowed on the outside step. We will also brief the big formations to be wary of a pitch moment of the nose of the aircraft, so they can let go should this ever happen. This will also be placarded inside the aircraft and included in our King Air briefing for new jumpers.
7. I am sharing the above information because skydive ops is very different from normal operations and leave people wondering why we fly certain configurations during the climb, jump run and descent.
The aircraft landed safely with the skydivers that did not exit.
The incident was promptly reported to the South African CAA and PASA national safety and training officer. The next day the jump team made adjustments to their exit procedure following discussion with the pilot and no further incidents or near-incidents were experienced.
