What Constitutes "Rough Air"?

PropFanPropFan
in General Discussion
As we returned to our home airport on Saturday in very choppy air, I found it hard to keep my 180C at or below the 129 mph "rough air or maneuvering speed" limit without sitting squarely in the prohibited 2150 to 2350 rpm zone. I am a relatively low-hour pilot with little experience in turbulent conditions, so I'm not sure I know exactly what constitutes "rough air". Other pireps from the area that day reported light to moderate turbulence at our altitude. The ride was certainly bumpy, but articles weren't flying around the cabin, and we weren't banging our heads on the roof. Thoughts/tips?

Comments

  • PropFanPropFan
    Sac Arrow: The plane is placarded, per the AFM: "Rough Air or Maneuvering Speed 129 mph." Thank you for the reference to the AIM. I'll check that out. It appears I may still have the challenge of finding an acceptable airspeed outside the 2150-2350 rpm limitation in "true" rough air.
  • flyguydonflyguydon
    Chop is not a problem. Green arc and all is good.

    Let's put it into perspective. Anything that is bad enough for you to need to slow down for fear of the plane coming apart is not something you'd fly in for very long. Sure, briefly over a mountain wave... or intermittent deflections... But again, anything bad enough to have to slow down for is not something you'd fly in longer than to find a place to get down.

    Continual hitting of your head on the ceiling is an indication of being close to this level. As Sac suggested... if you still have positive control you are probably not quite there. Deflections that make it obvious that "it" is beginning to take control and you might consider slowing her down for the ride.
  • GMGM
    flyguydon Wrote:
    > As Sac suggested... if you still have positive
    > control you are probably not quite there.


    If I'm being firmly pressed into the seat and jarred against the seatbelt on more than a few occasions (if the seatbelt is keeping me in the seat) it’s past the time to slow down not only for the for the airframe’s sake but for comfort. Passengers don’t appreciate their arms flying off their laps or water bottles hovering in front of their faces.

    GA aircraft are flying higher and faster than ever before, sometimes "Chop" will precede the heavier stuff. Don't always wait until you're in it to begin speed reduction.

    Proper preflight planning can give you a heads up to areas of moderate turbulence. And remember, reports of moderate in a large aircraft can be quite uncomfortable or even severe to a light GA aircraft.
  • vcollazovcollazo
    Remember PropFan, Va is the maximum speed at which full control imput will not overstress the airframe. It takes pretty heavy turbulence before you need to approach these deflections to maintain a relatively stable attitude. If you suddenly encounter moderate to severe turbulence do not chase airspeed or altitude. Remember the never exceed and maneuvering airspeeds are indicated. I haven't flown a 180 in a long time, but if memory serves me right, 2100 RPM should keep you below Va and well above stall speed.
  • PropFanPropFan
    Based on these responses, I don't think the turbulence we experienced was significant enough to trigger the "rough air/maneuvering" limitation. Nevertheless, there's certainly nothing wrong with taking a cautious approach as long as I can stay out of the "bad rpm" range.

    vcollazo, you're right: 2100 rpm is usually about what I use on downwind. It seems to put me around 100-105 mph. We had about a 40 knot headwind on Saturday, so at that rpm it was S..l..o..w going.
  • vcollazovcollazo
    PropFan,

    Also remember it's a good idea to climb in most cases. You're likely to find smoother air and a lower indicated will give you a higher true.
    Basically your true increases 2% per 1000 feet of altitude so at 10000ft that 109 indicated will be about 130 true. Also your Vy will be well below your Va and you can keep your RPM up.
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