March 28, 201313 yr Hi folks, during my flights I set the descend forecast with winds aloft, destination temp/QNH and the TAI altitudes, let's say 50nm before T/D. I am puzzled on how many miles setting the TAI altitudes drags the Top of Descend backwards, ie. the descend is prolonged, and the VNAV calculated T/D has to start often almost immediately. (ATC mostly needs to be asked for an early descend, for they guide me down much later, around the TAI off T/D. ) Having TAI on reduces thrust, but why does it prolong the descend distance that long? Thanx. Andreas BergPMDG 737NGX -- PMDG J41 -- PMDG 77L/77F/77W -- PMDG B744 -- i7 8700K PC1151 12MB 3.7GHz -- Corsair Cooling H100X -- DDR4 16GB TridentZ -- MSI Z370 Tomahawk -- MSI RTX2080 DUKE 8G OC -- SSD 500GB M.2 -- Thermaltake 550W --
March 28, 201313 yr Because the engines have to idle at a higher speed to maintain bleed pressure with TAI on so you have more thrust. I found if you enter your TAI on/off altitudes in the DES forecast , it helps a ton, or if you are not sure enter 10000/1000 or something like that. Eric W.
March 28, 201313 yr The 737 is not too good in descends as is. TAI makes the idle go up. --Peter Fabian
March 28, 201313 yr Author Thanx, guys! Andreas BergPMDG 737NGX -- PMDG J41 -- PMDG 77L/77F/77W -- PMDG B744 -- i7 8700K PC1151 12MB 3.7GHz -- Corsair Cooling H100X -- DDR4 16GB TridentZ -- MSI Z370 Tomahawk -- MSI RTX2080 DUKE 8G OC -- SSD 500GB M.2 -- Thermaltake 550W --
March 29, 201313 yr Commercial Member during my flights I set the descend forecast with winds aloft, destination temp/QNH and the TAI altitudes, let's say 50nm before T/D. 50nm seems excessive for TAI only, but since you mentioned the winds aloft and temp/QNH were added, that seems slightly more reasonable (depending on the wind). Make sure you're only using those altitudes where you're in the range of icing conditions +10 to -40C and visible moisture. A lot of simmers seem to forget that last part and think "oh, well it's cold, so I have to protect myself from ice," though ice cannot occur without both parts of the formula: cold and moisture. So, take a look at your weather information and have a look at where the cloud levels are, and the temps at those levels. If it's cold and there are clouds, that's when you should have AI on. If it's cold, but there are no clouds, there's no reason to have it on. Kyle Rodgers
March 29, 201313 yr destination temp/QNH You must enter average ISA deviation, not destination temperature there. And one more thing: at this time NGX doesn't take into account this two values, so you can enter them just for practice. At least until SP2. +10 to -40C I'd like to remind that it's +10 TAT and -40 SAT and last one depends on stage of flight. Rostyslav S Wanna fly 737NGX with turbulence?
March 29, 201313 yr Author You must enter average ISA deviation, not destination temperature there. Ups, yep... Andreas BergPMDG 737NGX -- PMDG J41 -- PMDG 77L/77F/77W -- PMDG B744 -- i7 8700K PC1151 12MB 3.7GHz -- Corsair Cooling H100X -- DDR4 16GB TridentZ -- MSI Z370 Tomahawk -- MSI RTX2080 DUKE 8G OC -- SSD 500GB M.2 -- Thermaltake 550W --
Create an account or sign in to comment