737-300/400 Mcp
 

Happened to me recently, the MCP "freezes", all numbers displays '8' (except the ALTITUDE window shows 50.000 ft). I could not set the CRS, HDG, SPEED.The A/P disengaged and will not CMD , A/T if engage only in MCP SPEED mode.

Tried to change the source of electrical with the APU GEN, nothing change.

Anybody know the "cure" for this ?

Try pulling the AFDS MCP DC 1 (P18-1-D-5) and the AFDS MCP DC 2 (P6-2-C-3) Circuit breakers. This will reset the MCP display.

One would assume that when 'the autopilot disengaged' they were airborne? Playing around with the A/T in speed mode on the ground might be a bit dangerous too :rolleyes:

I seem to remember a SB or SL on this and the fix was to put a different chipset in the MCP.

It appears that the original chips used were prone to overheating, especially with the radiant effect of the sun beating down on a black glareshield.

Not all SB's however are mandatory and so not all operators incorporate them.

Yes there is a Honeywell SB Mod D curing this problem, often referred to as the 'lock-up' condition. It's been ok within our fleet post mod accomplishment. If the MCP P/N is 4082260-937 or -939 then the SB No. is 4082260-22-0004. Different P/N and mod No. for the B737NGs.

Thank you all !
Mono, what are those SB , SL things ? We use the same nomenclature for those 'hot CABAT' Ha..ha..! Plenty of them ..AK. BJ, BT even XL !!

I've had it lock up once onthe ground. All that would work was the #2 CRS window
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Pulling CBs sis nothing, but shutting EVERYTHING down and starting agan froma cold aeroplane cured it!

The company say they've had it happen a number of times on other airframes and have traced it to poor bonding between the MCP panel and the windscreen.

This happened to me twice.Both times we were flying in clouds with high static electricity.We tried to reset it using CBs but nothing happened.After landing we talked to maintenance and they said the only way to reset it is to shut down the airplane completely(electrically) and power it up again.So actually there is no cure while airborne.A good chance to sharpen your manual flying skills!!