Snap roll vs. Va

Sport Aerobatics magazine of May 1987 noted some wind tunnel tests by
Avions Mudry - the info was vague but apparently confirmed significant
dynamic lift effects in snap rolls for the CAP 10. There are other
effects - if the flight envelope is drawn from power off stall speeds
at forward cg then its easy to get a higher load factor at the stall
than that calculated.
For the CAP 10B - Va is 146 mph and snap roll speed is 110 mph.

The reference below gives some flight data on snap rolls in a
Decathlon - not enough info for me to draw any conclusions on dynamic
lift effects but concludes that overall the loads are within the
design envelope. Some-one else may be able to analyse it - the only
relevant time history data is a positive snap roll from inverted at 80
kts giving +3g peak.

There are a number of standard design load cases - the designer must
ensure that snap rolls, at the recommended entry speed, do not exceed
the loads that they impose on the airframe - not always the same
answer for every airplane.

Reefrence: Loading Conditions Measured During Aerobatic Maneuvers by
Albert W. Hall, Langley Research Center, NASA. SAE paper 700222.



Greg Esres wrote in message . ..
http://naca.larc.nasa.gov/reports/19...ca-tn-2525.pdf