NTSB Links Crashes to Mythical Phenomenon
Downwind turn cited as probable cause in NTSB reports.
By Robert Goyer / Published: Feb 20, 2013
There have been a couple of accident reports that have come to our attention in which the NTSB cites as a probable cause the accident airplane making a downwind turn. Don’t get me wrong: The statement of probable cause is often little more than a way of saying the airplane crashed because, well, it crashed. The statement, “the pilot failed to maintain control,” is one of my favorites. Yes, we can tell he did, by the way the airplane crashed.
Naming the “downwind turn” as probable cause rises to a whole new level, however. One might as well name “an evil spirit” as being the culprit. The science is comparable.
In the first such report we found, featured in the On the Record section of the March edition of Flying, the NTSB investigator looked into the crash of a North American T-6 Texan which came to harm while maneuvering at low level near the airport in Perry, Michigan. In the report the investigator commented that the “left turn after takeoff resulted in the airplane encountering a progressively increasingly downwind condition during the turn,” the implication being that the airplane stalled as a result of the turn. Slow speeds, maneuvering, mechanical turbulence caused by tall trees all could have resulted in a stall and loss of control. The downwind turn could not have.
Yet while we were investigating the subject, we ran across another NTSB report, this one on a fatal accident that left four dead after a loaded Cessna 172 crashed at Wendover, Utah.
In the report, the investigator again points to the downwind turn, this time more directly, as a probable cause: The report in part reads, “The sudden change from a 24-knot left crosswind to a 24-knot tailwind during the pilot’s execution of the right-hand turn towards the downwind leg of the landing pattern, combined with some pitch sensitivity due to the cg location, most likely induced an aerodynamic stall and subsequent loss of lift that was not anticipated nor compensated for by the pilot.”
In this case, the pilot could not have anticipated it, because the phenomenon is a myth, and the pilot could not have corrected for it for the same reason.
Here’s Peter Garrison’s last column on the myth of the downwind turn, from 2005. The physics have not changed since then.
The point is, it’s shocking that in 2012 investigators at the NTSB, who would hopefully have more than a passing knowledge of aerodynamics, are still seduced by the lazy logic of the downwind turn.
Maybe we could set up an organization-wide seminar for them on the subject with Peter Garrison himself.