“Rotors on takeoff” is something of a nefarious phrase. Pilots are warned against it in particular airports where it is prone to occur, though nobody really talks about what happens if one finds him or herself attempting to take off in one. The general idea is to avoid it, and nothing in the conventional spectrum is said about how to manage the problem once in the rotor.
Less than 20 hours into my initial self-taught mountain flying experience based out of Leadville, Colorado in 2013-2014, I encountered my first rotors on takeoff. It was a, needless to say, “breezy” day, and I found myself at 200’, at full power, descending, with the airspeed indicator reading 40mph, 2mph above stall speed. Since it was a long runway, I had plenty of length left. Mildly alarmed, I said to myself, “well, it looks like I am preconfigured for landing again.” Within about 10 seconds, the reverse occurred. I was climbing and climbing faster than normal. About 20 seconds later, I was descending, so upon the next ascent, I decided to make a hasty exit in the opposite direction, for which I had the joy of watching pine trees scream by a little too close than I would have liked as I went back into the rotor briefly. The rest of the flight featured a first-time jaunt into mountain waves over the Rockies, where I rode the roller coaster from 12,000 to 15,000 feet and back, whether I liked it or not, no matter if it was idle or full power, or what direction I yanked the stick toward. The flight home later that day was uneventful in Leadville.
The next time something similar occurred was in Spain, at La Cerdanya. Unusually strong winds were blowing locally (and unknown to me) over the ridge to the south, and I was abruptly startled by a 200’ AGL descent at full power, this time at 3800’ MSL instead of 10,200’ MSL (with the same airplane, of all things). The descending air went away, and I carried on like nothing had happened.
The latest occurrence was an interesting one. It started with an unusual itch to go flying, though as I drove to the airport in Saanen, Switzerland, I had this nervous energy I couldn’t dispel. I thought the situation through, asking myself if I was in a good frame of mind to fly, if it was a bad day weather-wise, and I concluded that the weather was fine, and I had some lingering perseveration upon some business matters that just needed to be ignored.
Before I go any further, I should note that the same thing would happen in the Pyrenees. The weather would clear, the winds would be relatively calm, forecasts would indicate nothing that couldn’t be handled, and I would gleefully drive to the airport with this strange nervous overload. As I got slammed around by angry, snaking, localized winds in flight shortly thereafter, I came to understand that I have some peculiar ability to emotionally express the representation of my weather observations by getting anxious, while convincing myself everything was fine. Eventually, I learned to listen to that internal nervous energy and avoid certain parts of the Pyrenees if I felt that way.
Well, this wasn’t the Pyrenees, I hadn’t felt like that in ages, and I was going flying. It might have been a tad breezier than I normally would have liked, though it was down the runway, and everything would be fine. The wind situation was a rare summer “Bise,” which is a mildly humid, cold, and persistent northeast wind that funnels between the north side of the Alps and the Jura Mountains. It blows quite angrily through Lausanne to Lake Geneva, where things are open, though usually gets quite obstructed in the Oberland. I figured it would be just like other events and decided to head above the clouds as upper-level winds with the Bise usually are not turbulent, even if strong. Full disclosure: I went flying the day before, above the clouds, and upper-level winds per GPS were a smooth 40kts while the forecast said 20kt. The forecast for this day said 20kt at 10,000 feet.
Within 5 seconds of taking off, that nervous energy was proven correct. I hit the upward side of the rotor at 50’ AGL and went up like a rocket. I instantly knew what was happening and yanked the stick to milk the ride for everything I could get, which lasted a short period before cresting and descending rather startlingly for 3500’ MSL and full throttle on a cool day. With a smirk, I rode it until the next wave up, thinking I would progressively end up higher on the crest of each wave. When I started descending the second time and upward motion delayed longer than before coupled with the end of the runway approaching and a general slight increase in terrain ahead, I briefly contemplated attempting a rejected takeoff and doing a wild aggressive slip and brake screeching landing. Opting against that risk, I pressed forward, turning toward the path of least resistance, as the rotors started to even out.
That presented a progressive change in wind direction, where a headwind became a strong tailwind as the winds had to go around a massive mountain to my right. I was concerned about lethargic climb performance as that worked itself out, which was an accurate reality though not as risky. As the airplane picked up speed, I eventually began a normal climb out, proceeded above the clouds, and frolicked around towering cumulus to FL20 and mountains that reached 12,000’ to almost 16,000’, all with little turbulence and much less energy. Curiously, winds were 25kt below the 7,500’ cloud deck and 10kt at high altitudes.
The return trip was something of a question. How would these rotors work out on final approach and landing? Terrain is quite tight and interesting in this neck of the woods, with an issue that the Cub ends up too high. On final, I was alternating rapidly between idle power and 2200 RPM, with enough headwind that I had no trouble bringing it down before the numbers without a slip. That was a first in my flying career, to hop between cruise and idle power repeatedly on final.
Afterward, I blamed the scare on my underpowered airplane coupled with my intransigent insistence upon operating this inadequate aircraft from 1949 in prodigious terrain. Perhaps I ought to get a “real” airplane so stupid things like this do not happen? A charter PC-12 landed just ahead of me, so I chatted with the first officer, assuming that the PC-12, with all its power, certainly would not have had the interesting ride that I did. He confirmed that they had a similar experience initially as I did, with the rotors stopping their climb performance where they “had no choice but to ride it out.” What about final? “We were alternating between the stall warning and high amounts of power.” 100 hp vs 1200 hp. 1949 vs 2021. VFR vs IFR. EASA regulated charter operation versus vagabond foreigner in a taildragger. It makes no difference. Rotors are rotors on takeoff.
I decided to publish the video as, while actual hazards are a problem in aviation, the other half is poor decisions made when reacting to them. I have never read any sort of official, conventional, or generally accepted advice about rotors on takeoff, other than that they are bad. In my case, I have never experienced them at this airport. Why did they come out in full force on that day? When will I get surprised again?
As for what a reader might do when encountering the same problem in their aircraft, well, watch the video and decide for yourself. I am not willing to state that one should simply ride them out or do a rejected takeoff. It depends on the pilot, the airplane, the situation, and the airport. It is probably best to avoid them though.