FlyingMonkey Posted September 23, 2013 Report Share Posted September 23, 2013 Hey all... The yellow arc on the airspeed indicator for (at least my) CT is from 120-145 knots, and is supposed to be used only for smooth air flying. I just read a thread on the AOPA forums about flying in the yellow arc. Some guys say they just never do it (way too conservative, IMO), others they don't do it if there are any bumps at all (also too conservatives, IMO), and yet others that they fly there if they can and never even worry about it (not conservative enough, IMO). About they best idea I saw was to base it on comfort; if it's getting too bumpy to be comfortable by the seat-O-the-pants-meter, slow down. This seems about right to me. Thoughts? Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted September 23, 2013 Report Share Posted September 23, 2013 Comfort dictates for me and that keeps me out of the yellow arc most of the time. Link to comment Share on other sites More sharing options...
Jim Meade Posted September 23, 2013 Report Share Posted September 23, 2013 It's all about the chances of a large AOA change that would induce extra lift and stress the airframe. There are different kinds of bumpy. It helps to have a good understanding of weather and air movement. Yellow arc is only tangentially related to comfort, to me. Much more to do with positive g forces. The faster you go the closer to the edge of the envelope. I will fly in the yellow, especially at the very bottom, but near the middle or top I am thinking about what is going on. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted September 23, 2013 Author Report Share Posted September 23, 2013 At least with a Dynon I have a G-meter. I guess I'll be looking at the that to get a feel for the magnitude of bumps and turbulence and then act accordingly. No need to slow down for 1.2G bumps, but at over 2G I'd have to think seriously about it (not to mention I'll be having my fillings rattled out at that point). Link to comment Share on other sites More sharing options...
chanik Posted September 23, 2013 Report Share Posted September 23, 2013 the yellow arc is based on a somewhat arbitrary 50fps vertical gust. The real number to keep in mind over the Sierras flirting with rotor clouds is Va which is for any gust (and not labeled on the airspeed arc) That means you want the wing to stall before exceeding the load limit. It is all rather turgidly described In FAR 23.335 and contiguous sections, but the max G factor the wing will see basically corresponds to sqrt(V/Vno). So, counter intuitively, it is more dangerous if you are lighter since that drops your stall speed. You can also make it safer, if you don't need to climb by reflexing the flaps to -12 as that raises stall 5 kts. In the CT, it is 98kts which is just based on 42kts stall times sqrt 6 (2.44). But is can be 12kts higher if you sacrifice your lift. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted September 23, 2013 Author Report Share Posted September 23, 2013 IIRC there is a way to manually reflex to -12, does anybody know what it is? I don't think I'd ever use it, but I am curious just to have it in the bag of tricks. Link to comment Share on other sites More sharing options...
Doug G. Posted September 23, 2013 Report Share Posted September 23, 2013 Not if your plane is designed for the US. The -12 takes it out of the LSA category because of stall speed. Roger can fill you in, but basically it is a difficult modification with little return. (Not sure if it could even be done as E-LSA since it would no longer be LSA.) If you search the forum there are a lot of threads on this topic. Link to comment Share on other sites More sharing options...
Roger Lee Posted September 23, 2013 Report Share Posted September 23, 2013 Hi Andy, I have done some testing. Enough said for that part. The second part is it isn't worth the change to do it. You can go to manual on the flap switch selector on your panel and can get an extra 2-3 degrees, but that's not worth the bother either. Just put an extra coat of wax with Teflon and call it good. p.s. Absolutely no documentation supplied. Link to comment Share on other sites More sharing options...
chanik Posted September 23, 2013 Report Share Posted September 23, 2013 Wax won't help with Va speed though. Link to comment Share on other sites More sharing options...
FredG Posted September 23, 2013 Report Share Posted September 23, 2013 Kurt, you wrote that "the max G factor the wing will see basically corresponds to sqrt(V/Vno)." How does sqrt(V/Vno) become a value substantially greater than unity? I think I am confused about one or more of the parameters. Link to comment Share on other sites More sharing options...
chanik Posted September 23, 2013 Report Share Posted September 23, 2013 Ah, the other way, the square of the speed ratio; the speed solves for the sqrt of the load ratio which is also the G factor. So flying at twice stall speed means the wing stalls at 4G Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted September 24, 2013 Report Share Posted September 24, 2013 ...The real number to keep in mind over the Sierras flirting with rotor clouds is Va which is for any gust (and not labeled on the airspeed arc) ... When flying the Sierra Nevada Va becomes un-achievable at my cruise altitude. Link to comment Share on other sites More sharing options...
FredG Posted September 24, 2013 Report Share Posted September 24, 2013 Kurt, if flying at three times stall speed, does that mean the wings stall at 2**3 (or 8G)? Based on your earlier email, that seems to be the correct inference. Link to comment Share on other sites More sharing options...
FastEddieB Posted September 24, 2013 Report Share Posted September 24, 2013 I'm not great at math, but a picture is worth 1,000 words: Note the geometric (logarithmic?) rise of the stall speed with airspeed. Link to comment Share on other sites More sharing options...
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