Friday, September 21, 2012

Breaking the Chain

If you study aviation long you will hear about the "accident chain". This is a series of events and decisions, sometimes related, sometimes not, which eventually lead to an incident or accident. At any point the chain can be broken by making a different decision. Often these decisions are very easy to make in hindsight, they are less easy to make when you are in the moment.

Today's instrument lesson was less about instrument flying and much more about breaking the chain. What was going to be about a two hour mock check ride turned out to be 0.9 on the hobbs, 0.3 simulated instrument and a different lesson learned.

Link #1 The day started with my CFI running late, really late, 90 minutes late. Which is very unusual for him. Not a big problem, I had nowhere I needed to be. So I relaxed, took my time preflighting the plane we would be flying (its a new plane at the club and not one I know too well). I wasn't pressured by the time, but my CFI was feeling the pressure.

Link #2 I did preflight of the plane and noticed a couple odd things. One, the flaps extended, but extremely slowly. The low voltage light wasn't on but I suspected a low battery. Low but not dead. Two, two of the three tires were visibly low, not flat but low. So after I completed the preflight, I filled the tires to the proper pressure.

Link #3 We go to start the plane and it won't even attempt to crank. The battery was dead. There was no excuse for it to be dead, the plane had sat for less than a week with everything off (I double checked that during preflight, nothing was left on). But there it was, dead battery. My CFI gets out of the plane, finds the A&P and ask if he wants to help hand prop the plane and see if the alternator was working. We hand prop the plane, it fires up and, after a couple resets, the alternator starts charging the battery. We decide to go ahead since I had a hand-held radio with me.

Link #4 (and 4a?)  In run-up I cycled the alternator again and when I turned off the alternator the Garmin 430W power cycled itself. Alternator back on, everything was OK. When I did the mag check one side was lower than the other but both were within spec. I noticed the whisky compass was about half full of fluid, the ball was still floating, but the fluid was low. About this time my CFI noticed, the second on the clock in the plane moved significantly faster when the RPMs were higher and slower when the RPMs were lower. We may have found the cause of the low battery.

Link #5 After the normal delay for traffic landing at SJC airport (6 miles away) we were cleared for takeoff. The takeoff roll was good and the plane took off quickly and climbed strong. CFI took the controls, I put on the foggles and off we went. This plane climbed so fast (for a 172) I actually got to request permission to climb higher from ATC! The fun was short lived however, the engine was running a bit rough. CFI told me to fly and he adjusted the mixture to see if he could smooth out the engine.

Link #6 We leveled off at 5000 feet and he kept troubleshooting the engine roughness as I handled the radio comm and intercepted the required airway. He finally deciding that there must be bad plugs on the right side. We were then cleared direct to OYOSO (the initial approach fix for the approach we were going to fly.)  I repeated back to clearance and then said to my CFI, "You know, I'm OK if we call it a day and go back to the airport." I felt we had dealt with enough problems and didn't need to see what the next one would be. He agreed, he said he had just texted the A&P and let him know we were coming back. He said this was a good lesson in breaking the accident chain.

After canceling IFR and reassuring ATC we were OK and did not need assistance, I took off the foggles and we turned back to RHV. To be on the safe side we stayed at 5000 feet until about 10 NM from RHV. There I started the descent, about 2000 feet higher than normal. I got to learn a new trick. If you want to end up at a certain spot, put that location in the center of the windscreen and keep it there, that will give you the descent rate you need to get to the spot. Pretty cool trick that worked great. I flew a normal approach and a good landing. Then taxied the plane back to its spot and gave the keys to the A&P who suddenly had a bunch of work to do!

We talked about what we'll do on the next flight. We were both confident I'd get to that instrument checkride soon. All in all, it was a good day and another minor adventure. That's one of the things I love about flying... the little adventures.

PS. I just stumbled across an eBook by NASA called Breaking the Mishap Chain. Looks like some excellent reading.

1 comment:

  1. I have read this post and remembered this saying:
    'If you want to live long as a pilot,you have got to know when not to push matters too far.'

    It was a good decision you made to return and land due to the engine roughness. Three weeks ago, a friend of mine who is a Private Pilot taking his night rating invited me to right seat on a C172.

    It then emerged that the aircraft had a discharging battery. Therefore, the avionics did not function well. The radio and navigation lights were almost going off. We then decided to to use a trick in order to conserve the little current we had from the battery.

    Given that R/T is important in the circuit,we would switch off the navigation lights when on the downwind leg since we were the only ones in the circuit. When we begin to turn to base leg we would turn back on the navigation lights.

    After the first touch and go, we decided to make it a full stop during the next landing. As we were backtracking, the navigation lights went off and we had to entirely rely on the taxi way lights. Fortunately, we were the only aircraft moving at night at my home airport(HKNW).