To expand on that:
- Vmo is a structural limit. Too fast and you would get structural damage if you moved the control surfaces or experienced a gust.
- Mmo is an aerodynamic limit as shockwave formation affects lift and drag.
Regarding the relationships between the speeds, this is how I was taught.
E is EAS (equivalent airspeed), which is CAS
(calibrated airspeed) corrected for compressibility.
C is CAS
(calibrated airspeed), which is IAS
(indicated airspeed) corrected for instrument and position error. Basically IAS
T is TAS
(true airspeed), which is EAS (equivalent airspeed) corrected for temperature deviation from ISA. This is the true speed of the aircraft through the air mass.
M is mach number, which is TAS
divided by the LSS (Local Speed of Sound). The LSS is only dependent on temperature. For air, the LSS is 38.94 times the square root of the temperature in Kelvin.
The four graphs are for flight in standard conditions below the tropopause. The vertical axis is altitude, the horizontal axis is the value of the speeds. Each graph represents what happens if one speed (the black one) is kept constant while climbing of descending.
Looking at the leftmost graph, if you are climbing at constant EAS, then CAS
and Mach number will increase. Say you are climbing at Vmo, at a certain altitude Mach number will reach Mmo, and you can no longer keep EAS constant because you would bust through Mmo. So from that point you climb at constant Mach number. Move over to the rightmost graph and you can see that if you climb at constant Mach number, EAS, CAS
You can take the rightmost graph and put it on top of the leftmost to get the whole story of climb in a jet. There are also variations for temperature inversions and flying above the tropopause but I'll leave those as an exercise for the alert reader.
[Edited 2013-07-11 20:07:07][Edited 2013-07-11 20:07:25][Edited 2013-07-11 20:07:47][Edited 2013-07-11 20:08:05][Edited 2013-07-11 20:12:27][Edited 2013-07-11 20:13:56][Edited 2013-07-11 20:14:36]
[Edited 2013-07-11 20:15:29]
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo