Hello everyone,
Something is bugging me for a while now and I hope to find an explanation with you guys.
FCOM: "Above 20 000 feet VLS is corrected for mach effet to maintain a buffet of 0.2g"
Please correct me if I'm wrong, I'm really trying hard to undestand:
From what I undestand, VLS increases above FL 200 due to compressibilty effect on the wing and on the pitot tube; For a constant IAS, the stall speed will increase as mach number increases the more we climb with decreasing temperature. So makes sense that VLS increases. But since compressibility also affects pitot tube and the higher and faster we fly, the IAS will overrread. And now I'm confused cause the IAS displayed on the PFD is not corrected for compressibilty, so assuming we are flying at FL330 at 270 IAS. Does it mean the aircraft is actually flying at like 262kt EAS and the IAS is overreading by 8kt if you remove the compressibility effect? We just accept that small pitot reading error? Does the FMS knows exactly by how many knots the compressibility affects The IAS?
Please bring some lights with basic explanations, I'm no scientist.
Thank you.