FMC Cost Index Values
 

Minor thing but, anyone know why some Boeing FMC's can only go to 999 while others are designed to go as high as 9999?

Inflation? Currency conversion?

You mean like € vs $? :D

Cost index ranges for the various Boeing models:

737-3/4/500: 0-200
737-6/7/800: 0-500

747-400: 0-9999

757/767: 0-999 with Honeywell 200K and 700K FMC or 0-9999 with Honeywell non PIP, PIP and Pegasus Pre-2009 and Pegasus 2009.

777: 0-9999

Taking the 757 and 767 as examples. the original Honeywell 200K and 700 FMC's only had capacity of 200,000/400,0000 words and 400,000/1.4MB bytes capacity. This was insufficient memory capacity, to store CI values on a range of 0-9999.

When Honeywell's 1Meg/2meg 757/767 FMCS were introduced (originally Non-PIP FMCs which some airlines updated with the PIP software) with 1,000,000/2,000,000 words and 2MB/4MB bytes capacity the FMC now had sufficient memory capacity for CI values in a range of 0-9999.

The original Honeywell AIMS 1 on the 777-200/ER/300 had a 1,000,000 word and 2MB byte storage capacity. this being sufficient for storing CI values from 0-9999. This being the same capacity and available CI range of values on the Honeywell 747-400 FMC.

With the introduction of the 777-300ER and -200LR the Honeywell AIMS 2 upped memory capacity to 6,000,000 words and 12MB bytes.

The Honeywell 787 FMC has 15,000,000 words and 30MB byte storage capacity.

The Honeywell NextGen FMC, used on the 747-8 has 50,000,000 words capacity and 100MB bytes storage.

To sum it up, under 1,000,000 words and 2MB bytes storage capacity, the FMC could not store sufficient values to go beyond a CI range of 0-999.

The 737NG being the exception as Boeing never bothered to go above a CI range of 0-500.

:D:D:D

I literally laughed out loud at that one.

Incidentally, I can see the utility of 99 vs 999. I can see how the ECON speed can be fine tuned via increased CI sensitivity.

For other FMC's, what's the difference in cruise speed between CI 9999 & 9998?

It makes sense that more memory capability allowed the 4 digit Cost Index. But why bother? Is 0-999 not an adequate range?