Gravity

I use a simple wood notched dowel to gauge how much gas I have onboard b4 I launch, idiot proof I rarely launch with full tanks, burn more fuel to carry more fuel. I plan though using a higher than known FF, works for me.

I think this is part of the possibilities.The RV7, being aerobatic, has 2 sets of load factors. For 'normal,non-aerobatic flight' - it has the usual +3.8 / - 1.9 load factors. For aerobatic flight, it is weight limited to 727 kgs, down from 818 kgs MTOW.

 

Now this is where it gets interesting. Va is calculated from the clean stall speed at any given weight - and, Vs varies with the weight of the aircraft. So, at MTOW of 818 kgs - Vs = 56kts. At aerobatic weight of 727 kgs - Vs is, (my calcs), 50 kts.

 

Now, VANS states that at aerobatic weight of 727 kgs, the RV7 has a load factor range of +6 / -3 g - higher than at MTOW.

 

So, using the calculation of multiplying the Vs x the square root of the positive load factor to attain Va, I obtain the following:

 

MTOW 818 kg: 1.95 x 56 = 109 kts Va ( which is well less than the blue line on the analog ASI provided ex VANS)

 

MTOW 727 kg: 2.45 x 50 = 123 kts Va (which is the blue line shown by VANS for the RV7)

 

This presents the pilot with a conundrum, of sorts.

 

On the one hand, it appears you could use 123 kts as your Va for all 'normal' flight if the weight was limited to 727 kgs?

 

OR, is VANS saying that, yes, you can do limited aeros if the weight is kept below 727 kgs, and that during those aeros you should not exceed 6G?

 

AND, does VANS mean that, for the majority of the RV7s' usuage, it should be operated in the normal category to a limit of +3.8/-1.9g, because it is not really designed to be aerobatted for its entire life. In which case, it appears that they may have published a Va which is too high?

 

Remembering that the RV7 cruising speeds are way above even the Va of 123 kts, it is entirely possible that the airframe could be really stressed by hitting some really severe turbulence around mountain areas. And, with 180HP and a cruise pitched propeller, it takes quite a few seconds to decelerate to Va - probably too long to avoid some structural effects.?

 

It's also worth checking all the VANS SBs on their website: there have been SBs raised for stabiliser cracks, elevator spar cracks, and the wing aft spar at the inboard aileron hinge bracket. This would prompt me to think carefully about, not just aerobatics, but the cruising speeds to use where turbulence might be expected.

 

Having flown around 1000 hrs on every model of RV, and seen how often pilots flog them downhill with the ASI in the bottom of the yellow arc - I'm surprised that we haven't seen any obvious airframe damage in Australia. I can only ascribe this good result as being due to the inherent strength in the RV series. Love 'em.

 

happy days,