bogus ceiling on the perf data = chk reserve fuel

feetdry · 03-19-2008, 11:13 AM

ok im sure this question has been asked several times but i did a search and could not find it.
How do you fix the ceiling in the perf data that makes you stop at fl 280 and screws your fuel numbers up. I thought that if you change the perf init to 250/.78 on LR's and or make it max spd it would fix it. I kept changing it and couldn't get any results. I have been told a trick a long time ago other than the perf init but cant remember. This happens just seldom enough for me to forget the remedy.

RBower · 03-19-2008, 06:36 PM

FL280? That is weird. Usually it latches at FL333. You can use the 250/78 thing, but even then sometimes it doesnt work. One thing that always worked for me was to just select Max speed, then plug in the mach number straight into the flight plan (main page, not perf init).

yasir1212 · 03-20-2008, 04:50 PM

As far as I've seen it, you don't need to plug in 250 for the EP/LR, you can just put in the cruise Mach number or Max speed, but on the XR, you must put it in as 250/.78 or whatever your cruise Mach number is planned, or choose to plug in max speed, or else you'll get FL333.

Endir1001 · 03-29-2008, 11:18 AM

The FL333 should've been only an XR problem...I think

Were you trying to get it recognize an altitude higher or lower?

If you had planned for lower and it seems stuck on FL280, check your STAR that you have selected; are there crossing restrictions? these will force the FMS to plan to be at that crossing restriction unless you delete the restriction out of the flight plan.

Maybe that will help?

yasir1212 · 03-29-2008, 12:00 PM

You'll also get the Check Reserver Fuel message if you were planned for and have plugged in to the FMS a higher altitude and you get stuck at a lower altitude. If you were planned for FL370 and get FL310 or something as a final and you forget to change it in the FMS, you have not "captured" the FL370 altitude and you'll most likely get that message until you modify it in the FMS. Some people say the FMS "learns" on its own and you don't need to change anything, which is absolutely incorrect when it comes to this situation, as well as many others. Even though it does "learn" a little, you still need to have correct info. plugged in.

WetPink · 03-29-2008, 02:59 PM

Quote:

Originally Posted by yasir1212

You'll also get the Check Reserver Fuel message if you were planned for and have plugged in to the FMS a higher altitude and you get stuck at a lower altitude. If you were planned for FL370 and get FL310 or something as a final and you forget to change it in the FMS, you have not "captured" the FL370 altitude and you'll most likely get that message until you modify it in the FMS. Some people say the FMS "learns" on its own and you don't need to change anything, which is absolutely incorrect when it comes to this situation, as well as many others. Even though it does "learn" a little, you still need to have correct info. plugged in.

CFM 3-228

..."The only required Pilot adjustment to the initial cruise altitude is when
the aircraft is leveled in cruise at a lower altitude. The FMS
automatically makes the adjustment if the aircraft is flown higher
than the initial cruise altitude or descends after being level at or
above the initial cruise altitude."...

On a side note, the company really needs to put out some better guidance regarding FMS functions and procedures. The training department can't be that busy right now.

Yariv · 03-29-2008, 04:02 PM

you guys are talking about two different things. the only thing the FMS learns is the specific performance of the aircraft you're in. this means fuel flow and resulting speed at different altitudes.

The paragraph from the CFM doesn't take into account the programming error in the XR FMS which gives you FL333. it's true that the FMS will wait for you to climb to the cruise altitude in the perf init (which is why you need to change it if you don't plan on climbing that high) but the FMS will continue to use data for FL333 even after you climb above it due to this error. it basically sees 333 as the highest the aircraft is capable of at the speed entered. to change the cruise altitude, change the cruise speed first, as was mentioned here earlier.

IAH145CA · 04-02-2008, 12:50 PM

When you enter the speed the indicated must be high enough so it captures the indicated number not the mach number this will throw the burn off too. At lower altitudes the indicated will higher than the 250.

bluedevils · 04-06-2008, 03:32 AM

i think it'll say FL280 when you forget to init the performance data (just finish it). And from playing with it, when entering speed/mach (i.e. 250/.78), it seems to use the LOWER of the two at your cruise altitude to calculate burn/ete. So, if 250 = .75 mach ... 250/.75 will yield the same numbers as 250/.80