A pilot reported a possible fire hazard relating to the standard-looking; 3-pronged; 400Hz electrical outlets in the cockpits of the B747-400's and B777-200's. The outlets accept standard household appliances; such as laptops and battery charges; rated at 50-60Hz; to be plugged into the 400Hz rated outlets. No use restrictions are noted in the flight manual nor are there restrictive placards near the plugs.
Synopsis
A pilot reported a possible fire hazard relating to the standard-looking; 3-pronged; 400Hz electrical outlets in the cockpits of the B747-400's and B777-200's. The outlets accept standard household appliances; such as laptops and battery charges; rated at 50-60Hz; to be plugged into the 400Hz rated outlets. No use restrictions are noted in the flight manual nor are there restrictive placards near the plugs.
Narrative
I have brought this problem to 747 fleet management in the past and now the same issue is occurring on the B777-200 fleet. The cockpit (electrical outlet) plugs are being used for items that are not rated for the power output of the plug. The cockpit plugs are indeed 115v; however; the frequency cycles are 400 versus the U.S. Standard of 60hz. The reason this is a problem is that the power adapters for computers; etc.; that are plugged into this outlet CANNOT accommodate these 400hz outlets. Computer power adapters are rated to accept 110-250v and 50-60hz. Maintenance Control confirmed the cycles of 400Hz for these aircraft outlets and Line Maintenance confirmed that it is dangerous to use equipment that is not the proper 400 Hz. (This was when I was on the B747-400). In June 2009; Maintenance confirmed via ACARS that the B777 outlets are also 400hz and potential damage can occur to the aircraft and the equipment plugged in to it. This is a potential fire hazard (according to Maintenance) and it needs to be addressed through the proper channels of company Engineering; Boeing or both. If all of the above related to me is true; these outlets need to be placarded as unsafe for use by cockpit crews; or anything other than Maintenance use.
NASA callback
Reporter stated there are two standard 3-pronged outlets in the B777-200 cockpit; located behind the First Officer's seat; between the First and Second Observer's seat. There is nothing in their flight manual about restricting the use of the two cockpit electrical outlets to equipment rated for 400Hz use versus the 50-60Hz type commonly used for laptops or battery charges. Reporter stated he has ruined one of his own computers when he was flying the B747-400; which have the same type of standard; three prong electrical outlets. Reporter stated he believes the transformer rectifiers (TR) may be affected and the improper use of the outlets is a fire hazard. He feels that at a minimum the outlets should be placarded. Just a simple sticker; indicating 'NOT' to plug in household items; due to the large differences between 50-60Hz and 400Hz may prevent an electrical fire; whether in-flight or on the ground.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.