The never-ending myth of the "dangerous downwind turn"
November 4, 2006 edition
steve at aeroexperiments.org
The myth of the "dangerous downwind turn", or the myth that is more difficult to fly in the downwind direction than in the upwind direction, never ends.
Here are some examples from published literature and other sources. Some pertain to full-scale, piloted aircraft and some pertain to radio-controlled models.
Source: "West Wings Hunter" by Curtis Matikow. Radio Control Jet International magazine, issue 80 (October/November 2006), pp. 28-30. Quote: "After a 150 foot take-off run, she was off and climbing, but rather slowly...as soon as I turned downwind, I knew I was in trouble. With the modest power of the motor, the extra drag and weight of the landing gear I had made up, and the 30 mph tailwind, I was unable to keep altitude downwind. I ended up in the bushes at the edge of the runway..."
Source: "Electric Jet Airplane Design" by Ian Monty. Quiet Flyer magazine, v.11, issue 08 (August 2006), pp. 24-27. Quote: "When turning onto the downwind leg of a landing pattern, always be ready to add a little extra power."
Source: Certified Flight Instructor (and recent graduate of Embry-Riddle Aeronautical University) giving me a biennial flight review in a Cessna 172 at Corvallis Oregon, spring 2005. Quote: "Let's do the stall flying into the wind--the wing will stall at the same airspeed flying in either direction, but it will take more altitude to recover if we are flying downwind. It's like the difference between taking off into the wind and taking off with a tailwind."
Recall again that in the related article on this website entitled "Downwind turns ARE 'different'!", we noted that IF there is a significant wind gradient in the usual direction (wind increasing with height), then an aircraft actually extracts energy from the wind gradient (leading to a decrease in sink rate) when descending WITH the wind, and loses energy to the wind gradient (leading to an increase in sink rate) when descending INTO the wind! Yet many of the pilots quoted above appear to be describing the opposite phenomenon. It certainly appears that in many of these cases these pilots are unconsciously moving the control stick aft and decreasing the airspeed to a value well below the optimum airspeed, and simultaneously increasing the angle-of-attack to a value well above the optimum angle-of-attack, when flying with a high groundspeed, i.e. when flying with a tailwind.
For more, see these related articles on the Aeroexperiments website:
Brain teasers for those who believe that downwind turns are "different"
Downwind turns ARE "different"!--this is a bit of a "disclaimer" for the "Brain teasers for those who believe that downwind turns are 'different'"!
Mathematics of circles in wind
And for still more, see these articles from the "Ask J and D" feature of the "DJAerotech" website:
Downwind -- debunking the myth of the dangerous downwind turn
Wind_plane -- more on the above topic, with some interesting notes on wind shear
And for still more, see these articles:
Challenging the wind by Martin Hepperle-- an interesting little article on the best strategy for flying in wind during a pylon race