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Old 4th January 2014 | 08:56
  #224 (permalink)  
rudderrudderrat
 
Joined: Oct 2009
Posts: 1,270
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From: UK
Hi HazelNuts39,
So V2 can be equal to V(alpha-prot)?
Well spotted!

FCOM, Aircraft Systems, DSC-27-20-10, Protections:
"At Take off aProt is equal to aMAX for 5s."
By which time, the SRS will have commanded about V2+10.
During OEI, aFloor is disabled.

@Chris Scott
Hi Chris,

Thanks for those figures in post #213 because if we assume the Cl is proportional to AoA (straight line graph between afloor and aMax), then we can guesstimate aMax.

Lift = 1/2 rho * A*Cl*Vsquared.
Since the lift remains constant at 1g, and A is constant,
Cl(amax) * V(amax)squared = Cl(afloor) * V(afloor) squared.
Rearranging Cl(max) = Cl(afloor) * V(afloor)squared / V(amax)squared.
If we assume Cl is proportional to AoA then,

AoA(max) in conf3 = 15 * (1.1)squared/(1.06)squared = 16.15°.
Using the same assumptions, astall = 18.15°
Since the accuracy of the AoA probes is 2.5% (see post #46), then the error could be +/- 0.45°.
18.15 - 0.45 = 17.7

I wonder if that where the 17.5° came from?
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