Turbulence

[Sparkles1]

During the last few days area 20/21 have had sigmets issued for severe turbulence. What type of turbulence would you only fly in with a typical ga single/twin?
Is this type of turbulence encountered constant throughout the areas involved or just localised and short lived phenomenona?
Having only been in light turbulence have really nothing to compare what moderate and severe would be really like.
thanks

[Trojan1981]

Flew around in a Dakota (piper type) on Mon-tues. Patches of moderate turb west of Richmond below about 7500ft. Severe turb around bindook/ blue mountains and in lee of mountains in the Pigeon House Mtn area (south of Nowra) unfortunately ended the days flying early. It was pretty unberable, however once away from the mountains it was very smooth.

[SIUYA]

Sparkles1………….

Have a look at CASA's Safer air travel - Turbulence (http://www.casa.gov.au/airsafe/trip/turbulen.htm) for some pretty basic information on turbulence.

Turbulence can be generated by obstructions to airflow, such as mountainous areas, and if the wind component perpendicular to ridges or areas of high terrain is >50kts, then severe turbulence will normally be present! Under those conditions, the turbulence can extend for 50 to 150 miles downstream from the terrain that generated it.

Moderate turbulance is accepted as generating a positive/negative ‘g’ load of 0.2 to 0.5 ‘g’, and severe turbulence is accepted as generating a positive/negative ‘g’ load of 0.5 to 1.5 ‘g’.

Aircraft handling in severe turbulence can become problematic! :ooh:

Also, if you exceed the design manoeuvring speed (Va) of an aircraft while flying in turbulence then you’re certainly increasing the likelihood of damaging or breaking something, and also of frightening the sh1t out of yourself by doing so! :ooh: In summary, DON’T exceed Va in those conditions!

From memory, Va is 1.95 Vs1 for normal category light aircraft, and 2.1 Vs1 for utility category light aircraft, but I’m happy to be corrected on this if wrong. :}

[NZScion]

My understanding of Va was the maximum speed at which full control deflections do not cause structural limits to be exceeded (i.e. the aircraft will stall before you overload the wings if you suddenly heave the stick all the way back). You fly at or below Va in Turbulence to prevent structural overloading (turbulence ripping the wings off your aircraft due to sudden changes in attitude). Please correct me if I am wrong

[RadioSaigon]

Think you might find Va relates more to the current weight of the aircraft than its normal/utility category rating.

[Cap'n Arrr]

And the Turbulence Penetration Speed would be worth using. Only use Va if there is no Penetration Speed for your aircraft.

I was under the impression that severe turbulence meant the aircraft was pretty much uncontrollable (disturbances to attitude).

[SIUYA]

RadioSaigon............

Think you might find Va relates more to the current weight of the aircraft than its normal/utility category rating.

Yes, and because I said that Va is a multiple of Vs1, and because stall speed varies as the square root of weight (or lift) varies, I'm therefore really not too sure what point you're trying to make. :confused:

Cap'n Arrr...........100% agree, if the POH quotes a TPS. :D

If not then the rules of thumb I previously quoted seem to make sense, remembering that Va is the maximum speed you'd want to be at.

[empacher48]

There are times when turbulence might get so bad that Va is not even a comfortable speed to be at.

As mentioned Va is the speed where maximum control deflection will not cause structural damage, the aircraft will stall before damage occurs. It is related to weight. From memory the C207's Va ranges from 103kts light through to 130kts at MAUW.

There have been times where I have been caught in the wrong place in certain wind conditions, and you can feel that hand of god about to throw you about - just get it below Va, and get the seat belt tight, ride it out - check the punters are ok, re attach the carpet to the floor and put everything back into its place!