Honeywell SPZ 8000 series

[Mzee]

Trying various sources for answers but I have two queries on the FMS fitted to Challenger 601.

Scenario: Both FMS in 'Initiated Transfer' mode and setup with all parameters inc perf i.e. Cruise Lvl, speeds, Fuel qty and databases etc identical.

Q1. How come on starting a long leg selecting 'Progress' (FMS 1) on climb-out it gives say 400lbs fuel at dest and will increase as you get into cruise say at FL390 to give a sensible figure at dest of say 2500lbs (To me this would be normal - high fuel burn in climb etc)whilst FMS 2 starts around 2700lbs at dest and reduces to roughly match the first FMS on touchdown. Very noticeable on legs over 5hrs.

Q2. Same scenario but FMS 1 will give a much lower Perf Ceiling (around 8-10,000ft) than FMS 2, will eventualy agree but around 4hr mark.

Are the Q's related? Which one do you believe?
Fuel Flows identical, Fuel Tank contents senders recently calibrated.

Any help would be appreciated.

[freespeed2]

Hi Mzee,

First apologies for any possible stupid questions, since I fly a GIV with the 8000, so maybe it works different.

Just curious what the system spits back if you use dual mode for the perf?

On last sim, a guy who flys Global started talking about smartperf, which learns and remembers your inputs from previous flights and updates its calculations accordingly. Does the 601 have this? If it did it might explain the differences depending on which side is used for perf init more often.

Are you giving a wind & temp during perf init, or a perf plan after the plan is complete. The 8000 uses 100% of present wx out to 300nm, and 60% current/40% historic or perf plan winds to 600nm, then 100% perf plan beyond that. (mileages maybe slightly off from memory but it does do this). This might explain the big difference between on the ground and TOC figures.

The 8000 on the GIV has a problem calculating fuel from T/O to TOC. The GIV checklist requires that the FMS fuel quantity on perf init page 4 is deleted to agree with guage reading during cruise checks and every hour of flight thereafter as they tend to go out of sync. This caused huge debate when it appeared first, as you can imagine, and there were suggestions that it was purely Gulfstream trying to encourage pilots to check for a fuel leak frequently.

Hope this helps in some way, or at least might give you somewhere to look. Of course it may be of no use for a 601 based 8000. If so, apologies.

Good luck with it.

Freespeed2

[g4phil]

Operating a GV here, basically an upgraded SPZ 8000 (SPZ 8500).

We have just suffered a similar problem, the answer is to turn smartpref off and reload the aircraft database (first disc) to each FMS.