fulcrum
stranger to the ground
- Joined
- Dec 3, 2001
- Posts
- 122
hey dudes ! just an humble cfi's 2 cents
Coffin corner occurs at an aircrafts absolute ceiling where the speeds at which mach number buffet and prestall buffet occur are identical
stall speed is a function of IAS and Mach number is a function of the local speed of sound whic itself is a function of temperature
for a constant mach number the IAS decreases with altitude due to decreasing LSS to prevent the IAS from decresing to its stall speed the mach number must be increased
for a constant IAS the mach number increases with altitude due to decreasing LSS and temerature to a point where the IAS exceeds the critical mach number
to prevent the mach number from exceeding critical mach the IAS must be reduced which results in a decreasing mach number so there comes a point at the aircrafts absolute cieling where the aircraft can go no higher because it is bounded on one side by the low speed stall buffet and the other by the high speed buffett because the stall IAs and the critical mach values are equal
this is the coffin corner and it effects the altitude attainable by the aircraft,
usually there is a buffer built in and that is the difference betweeen the absolute and the maximum service ceiling
hope this helps
Fulcrum
Coffin corner occurs at an aircrafts absolute ceiling where the speeds at which mach number buffet and prestall buffet occur are identical
stall speed is a function of IAS and Mach number is a function of the local speed of sound whic itself is a function of temperature
for a constant mach number the IAS decreases with altitude due to decreasing LSS to prevent the IAS from decresing to its stall speed the mach number must be increased
for a constant IAS the mach number increases with altitude due to decreasing LSS and temerature to a point where the IAS exceeds the critical mach number
to prevent the mach number from exceeding critical mach the IAS must be reduced which results in a decreasing mach number so there comes a point at the aircrafts absolute cieling where the aircraft can go no higher because it is bounded on one side by the low speed stall buffet and the other by the high speed buffett because the stall IAs and the critical mach values are equal
this is the coffin corner and it effects the altitude attainable by the aircraft,
usually there is a buffer built in and that is the difference betweeen the absolute and the maximum service ceiling
hope this helps
Fulcrum
