I got a problem with getting MACH speed in FMC.I want to have an altitude change during the flight, so at the leg I want I put .800/360, but the FMC gives an error.I tried several things, but didn't work. But when I put:310/360 it works perfect. How to get the MACH in ?I also use the POSKY 763. I have seen some posts and the onlything I have to do is download that program B763 PIC POSKY3 ?Thanx,FlyerNL

767 fmc will not accept mach # , its stated in the manual

Thanx for that answer... So how do I know how many knots is the MACH then ?Thanx,FlyerNL

You really don't from a quick and dirty math point of view. MACH speed vs IAS is a function of atmospheric pressure/temps etc. We have a circular computer like the old EA-6B we spin around to develop the answers.Just between you and me, I'd just keep track when you are at cruise what you are indicating vs MACH number and tweak that. Wish I had a better answer for you without running into IAS vs TAS vs Pressure Altitude etc.Timothy

Here's a formula that will keep you working:TAS divided by 600 = MACH480 / 600 = .80 MACHMACH multiplied by 600 = TAS.80 X 600 = 480 TASTAS=true airspeed

Hi allDid a "Google" on "Mach TAS conversion" and popped up all sorts of the most oddest sites. One was the complete formula which was used in sims (unknown if it was full-blown airline type box or PC based). I would have cut n paste but I think that is in violation of the forum rules.Anyway, so now I went and violated the forum rules and found this little chart:SPEED EXAMPLES FOR FL350 AND -53 DEG. CELSIUSMach(Miss).65 .70 .72 .76 .78 .80 .82 .84 km/h 643 704 759 778 824 843 861 889 907 TAS 347 380 410 420 445 455 465 480 490 I have not "run the numbers" but they look close. Using KenG's formula they are close enough for government work.Timothy(Feeling the need for speed! This is gonna bug me)

Thanx for the answers. FlyerNL :-wave

If you want to set a specific mach for your climb, use FLCH, and dial the speed.For cruise, there's a couple of options. Use VNAV in speed intervention (not the preferred method), or modify your VNAV CRZ page with your desired speed.You cannot enter a mach speed from the LEGS page, however.Jon (KSEA)