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godu
10th Dec 2009, 11:59
A new EEC software is being loaded by boeing on the CFM engines for smoother transition of thrust change from derated Climb (CLB-1/2) to Climb (CLB) at 15000 ft which would now occur by 19000 ft. From guys who know this I want to know does the TMD still indicate the derate (CLB-1/2) till 19000 ft after this new software is loaded?

ballyboley
10th Dec 2009, 20:30
This sounds interesting - is it getting rolled out on all the existing NGs or just new ones?
My operator and a few others I believe encourage us to take the CLB1/CLB2 out of the FMC when cleared to a flight level above FL150, mainly when well below FL100 and get cleared to a high level. I believe its something to do with the fact its better to get up there sooner to burn less fuel by burning a little more fuel to get there sooner (if that makes sense!) Just wondering if this is commonplace and does it really stack up?

CaptainSandL
11th Dec 2009, 10:48
Hi Godu,

Good question, I have not flown a new FADEC-EEC equipped a/c yet so I don’t know, but I would say that TMD cannot indicate CLB until full CLB limit is reached ie at 19,000ft – just my guess.

The engineers have been given reams of info to ensure the permissible engine/EEC/FADEC intermix combinations, some of this contains useful flight ops info which may be of interest to crew as follows:

A partial list of changes/improvements is as follows:
EEC software version 7.B.U1 (P/N 1853M78P31 (FADEC2) and 2044M25P12 (FADEC3)) was introduced most recently and feature the following improvements:
• Introduce lightning stall detection logic and accommodation logic.
• Introduce bodie stall margin improvement logic
• Improve variable stator vane (VSV) open beta margin logic
• Add compressor health calculations
• Introduce water wash menu mode functions
• Introduce a new ECU/EEC fuel nozzle fault message
• Introduce variable bleed valve (VBV) sand ingestion logic
• N1 Trim altitude increase and optimization
• DAC engine instability correction
• Debris Monitoring System (DMS) resistance history

EEC software part numbers 1853M78P27 (FADEC 2) and 2044M25P07 (FADEC 3) and later include several significant operational differences from previous software versions including - a higher approach idle schedule, a higher minimum in-flight idle schedule, a transient N1 redline addition, and a faster engine deceleration rate during Refused Takeoff maneuvers. These in-flight idle differences will be readily noticeable to the flight crew. Due to the different engine deceleration rate during an Refused Takeoff maneuvers, intermix of these software part numbers with earlier part numbers is not permitted.

Intermixing with an earlier version of software will cause transient
asymmetric thrust differences due to different acceleration / deceleration rates at altitude.

Intermix of one of these software versions and any prior software version currently approved for installation will result in a small difference in idle speeds for three seconds after touchdown if thrust reversers are not deployed. This difference in idle speeds is negligible and requires no change to current flight operations.


Ballyboley,
It is available for retrofit, subject to intermix restrictions.

Re full thrust climbs, they do theoretically save fuel by getting you to the more efficient higher altitudes sooner, but it is not always appropriate due to high climb rates in busy airspace (RA risk).

S&L

godu
12th Dec 2009, 08:39
What I know is that this is for smoother transition by modulating the LP stage variable inlet guide vanes. Now I' ve got two more questions on this-
(i) Do the maint change software on both the engies at the same time, as I see it would be better to go one at a time.

(ii) Would this lead to remaking the performance graphs?

CaptainSandL
12th Dec 2009, 21:30
(i) Generally yes, but read the SL/SB for full details, there is pages of it for every conceivable combination of engine/EEC/FADEC etc. It is undesirable not to mod both engines at the same time because of the differing accel/decel rates a mix would give.

(ii) I dont think so. I would imaging the perf differences are negligible or exceed current cert perf, eg "a faster engine deceleration rate during Refused Takeoff maneuvers".