In the flight1 manual it gives cautionary maneuvering speeds based on weight ie VA1600 at speeds 81 and above, VA2000 at 92 and above and VA2450 at 99 and above.My question is if my weight is 1800 then what would the cautionary speed be? and for the rest of the weights what would the formula be?Also please why are there 2 maximum flap speedsVFE 10deg 110KIASand also 10-30deg 85KIASWhich speed would apply to 10degrees as surely it can be 110 and 85?Ive posted this on Flight1 support forums but things are sometimes a little slow on there sometimes so thought Id post here tooThanksGraham

Concerning flaps, the second statement should be read to mean "Greater than 10 up to 30 degrees = 85". I.e., one notch of flap is permitted below 110 knots but any further requires speed less than 85 knots.Va is related to structural load, as you may be aware. Roughly speaking, full/large deflection of elevator at speeds greater than Va can exert G forces that exceed the aircraft's margin of safety (3.x Gs) and thus bend or break wings, tail, etc (As happened to an airliner a week or so after Sept 11, in New Jersey as I recall). If the Va for 1800 lbs isn't given, presumably you must interpolate. Are you saying that Va increases with more weight in the documents for the 172? This surprises me at first blush, I'll have to think this through a moment.

>>Va is related to structural load, as you may be aware. >Roughly speaking, full/large deflection of elevator at speeds>greater than Va can exert G forces that exceed the aircraft's>margin of safety (3.x Gs) and thus bend or break wings, tail,>etc (As happened to an airliner a week or so after Sept 11, in>New Jersey as I recall). If the Va for 1800 lbs isn't given,>presumably you must interpolate. Are you saying that Va>increases with more weight in the documents for the 172? >This surprises me at first blush, I'll have to think this>through a moment. >>>Va is determined at the point on the flight envelope where the stall speed coincides with the limit load factor. That is, the speed and G where the aircraft both stalls and touches max allowed G at the same time. Since stall speeds varies concurrently with weight, Va also varies concurrently with weight.

Thanks. An even better answer.

<>Just a minor correction. VA covers the deflection of all control surfaces, therefore including ailerons and rudder, not just elevator. I think the airliner accident you referred to was actually caused by excessive rudder during a turbulance encounter and not elevator deflection.VA is often associated with the stall speed i.e. as the aircraft slows, VA decreases.A great formula to remember is Va decreases

Absolutely Jim. I noticed the elevator error soon after i posted. That's what i get for posting late at night while tired! Thanks