VNAV behaviour in thunderstorm

[mozart 1]

HiI just simulated a flight out of MMMX. The first 30 minutes were "bumpy" - medium chopp I'd say. I climbed using VNAV mode. What I noticed: the target speed indication (little pink arrow on the speed tape) jumped around erratically. No big moves, but moving between 290kt and 300kt. It only stabilized once I was out of the rough.Is that realistic or something happening only in the Sim (that would be OK, I am just curious)? Or do real world pilots not use VNAV when climbing through rough weather?ThanksChrisPS: although I was using AS6 and had just downloaded current weather, this was not hurricane "Dean" - I was flying out to the Northwest.

[downscc 1,327]

I have disabled gusts in thunderstorms in the AS6 options because I found the effects were very unrealistic.That's not to say that indicated airpeed doesn't vary in rough air because it certainly does, but nothing like AS6 was doing to the sim.A/P is very nice to have in moderate to heavy turbulence because it does a good job of keeping the average speed and altitude at the setpoint; however, the severe stuff might be best flown by hand (depending on the airplane and systems) because by definition you are no longer trying to hold an average altitude (you're trying to survive).

[michal 44]

>best flown by hand (depending on the airplane and systems)>because by definition you are no longer trying to hold an>average altitude (you're trying to survive).>I agree. The principle of flying through very rough air is to forget about altitude. This applies to aircraft of any size. Holding wings level (and survival) and flying below maneuvering speed is the only priority. No sane pilot would fly VNAV going through even a mildest thunderstorm.Michael J.http://img142.imageshack.us/img142/9320/apollo17vf7.jpg