I'll preface this post by saying "no-one was hurt." So read on and don't worry.
Sanjay got a great example of several things today. Probably the most useful, non-flight 0.3 hobbs time he'll ever pay for. First, the ATIS at PAO was reporting 320 @ 14 knots. A vistual look at the sock from the run-up area indicated more like 020 @ 14. Winds varying from 60 to 80 degrees off the nose. We were in a 152.
During our pre-take-off briefing we talked about the required yoke input during the take-off roll and I asked him what would happen if he took that out at any time during the take-off roll and attempted to steer the plane down the runway with the ailerons neutral. The short answer to this question was, with a 12 to 13 knot crosswind component, if we do that we will crash.
Good. Don't do that.
Then he noted that the motor glider taking off before us did not seem to have any aileron deflection at all. I had a look and had to concur... maybe a small amount, but not what you would expect for the conditions. Well, it doesn't look right to me but I don't fly motor gliders. So we watch the motor glider's take-off roll, watch his slow acceleration, watch him begin to weathervane almost right away, watch his tail swinging to the left and watch his initial attempt to correct the condition by hitting left rudder (and, I think, pulling power to idle at this point to abort the take-off), so now tail swinging left, then nose yawing left, right wing rising, left wing dipping precariously close to the ground, speed slowing but not slowing quickly enough... watch his desperate attempt to re-correct by hitting right rudder so that the plane might at least escape a ground loop, even if it ends up traveling diagonally across the runway.
And for as close as he was to striking that left wingtip on the ground, I have to say that the pilot did an amazing job of getting the plane back under control, ultimately coming to a rest just off the right side of the runway.
I think Sanjay will probably never forget the sight of that. But what could cause a very experieced, well-respected pilot flying his own airplane, which he has owned for years and with which he is very familiar, to fail to correct for a 12 to 13 knot crosswind? It is virtually inconceivable that he would have simply forgotten. I don't have the answer, but I have some ideas and in the interest of learning from the woes of others rather than having to experience them ourselves, let's see how many possible causes you guys can come up with. That's your Question of the Day for today. Before posting any reply, please remember that this is an experienced pilot who deserves our respect and that the only point of our conjecturing is to learn from a realistic scenario, and not to criticize. With that in mind, what could cause such a thing to happen?
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Was the pattern busy? Perhaps he was concentrating on taking off quickly to get out of the way of landing traffic. Or perhaps he was going on a long trip and was thinking about his flight plan or route after takeoff. Maybe subconsciously he had remembered the ATIS report and had thought that the wind was straight down the runway, and therefore thought he was correcting. The wind was also almost constantly changing - maybe when he looked at the sock it was more of a headwind and he just didn't look at his point of entry onto the runway. Or maybe even more simply, it was just one of those days.
ReplyDeleteWhat Julia said is one of my first thoughts... Given that ATIS reported one thing and the sock reported another it seems likely that the wind was shifting. A visual check of the sock one moment sounds like it could have been different a minute later. So perhaps a check was done and maybe the pilot was told to position and hold and prior to clearance to takeoff the wind shifted and another visual check of the sock and proper adjustment was not made--- would an experienced pilot do that??? Seems not too likely.
ReplyDeleteAnother possibility is perhaps something mechanically was wrong with the ailerons and the control input on the Yoke did not translate into the actual proper deflection of the ailerons. So the experienced pilot put in the correct xwind aileron deflection but the actual aileron was insufficient because of a mechanical problem. If that was the case, an experienced pilot might realize after analyzing what is happening that my ailerons are not working so my best option is to head into the wind and hope that will prevent the ground loop and that the plane will be easier to control and bring to a stop. That scenario matches some of the observations.
That was my thought. There have been accidents where a control lock was left in and not noticed til the take-off roll. That would be a missed preflight or run-up checklist item. Or a cable could have slipped or broken and it would be possible for the pilot to move the yoke around during taxi and runup but not notice, if not actually looking at them, that the ailerons weren't corresponding. I suppose it's even possible for the malfunction to occur at the momemt the controls are deflected for that particular take-off. The only fix for that would be to glance at them briefly before adding power. I don't do that, but I think I will add it to my procedures from now on. The other, catch-all "fix" was that the pilot made a very timely abort decision that certainly prevented the situation from becoming much worse. I think he came to a stop just past the middle windsock, which means he initiated he abort well before the halfway point.
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