I Learnt About Human Factors From That

February 2024

GA ILAHFFT – All secure?

Dear fellow aviators, the following account of a compound rigging and daily inspection error might be of interest, especially to those flying Standard Cirrus gliders, although I suppose similar battery installations can be found in many other types.

My syndicate partner and I installed a new variometer and, in order to check its operability, we connected No1 battery in its starboard side slot behind the seat-back rest (our Standard Cirrus glider has slots for two batteries behind the back rest, located either side of the housing for the landing gear). After completing the installation we switched off the power supply but forgot to take out the battery, which was left in its slot until I next rigged the glider a few days later. On that day, I fitted the No2 battery and secured it with its latch and screw, not bothering about No1 battery because I knew it was already in its place. 

During my first flight of the day, I noticed that the controls felt slightly heavier than I was used to. As I entered cloud at 850ft AAL, I did not retract the undercarriage and landed shortly after. My syndicate partner took the second flight and reported that when he operated the undercarriage lever in order to extend it, he could only move it half way; he then moved the lever fully back again before being able to fully extend at the second attempt. I had a second flight and was able to retract the U/C without any problem but still noticed the heavy feeling on the controls.

When we de-rigged at the end of the day, we found No1 battery had dislodged from its tray and slid backwards into the area to the right of the U/C housing where the aileron-rod junction branches off into the starboard wing. When we had installed it to check the variometer we hadn’t secured its safety latch and subsequently completely forgot about it. Although it was possible to move the control rod, the battery was lying on top and was being bounced around by any control column movement. Additionally, we noticed that the U/C rod extended back into this space, and the battery would have prohibited its movement if it happened to be settled in the rod’s way.

Although it appeared that the battery did not completely obstruct the movement of the aileron control rod, it might be possible that such a situation could occur, either if it settled in a position which did not happen on the day, or if a slightly differently shaped – perhaps smaller – battery was installed.

I should perhaps add that my syndicate partner and I had never included an additional check of the battery position and latches in our DIs. They were simply always put in their slots, secured and the seat’s back-rest put back in place and secured with its screw. Needless to mention that the installation of a battery is not mentioned in the aircraft operating manual in a glider of this vintage.Make sure to check that batteries are installed and secured correctly as part of DI, and always secure batteries, even when ‘only’ using them on the ground to check something.

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