Brown Shoe et al,. .I trust that the procedure being used to troubleshoot with regard to speed card CBs being pulled was in accordance with an appropriate checklist.. .. .CB resetting, pulling, cycling and the like should be strictly in accordance with authorised procedures. Otherwise the consequences can be unexpected and quite serious.. .. .An example of such experimentation occurred to a DC10. The very experienced FE persuaded the very experienced Captain and First Officer to try a little experiment by pulling the N1 sensing CBs to see what effect it had on the autothrottle response. To cut a long story short the result was quite dramatic and tragic.. .. .The number 3 engine fan speed increased rapidly and the engine exploded shedding fan blades in all directions penetrating the fuselage and a cabin window; pressurisation loss; passenger ejected; injury to other passengers; loss of electrical systems due to damage etc. Fortunately the crew managed to land the severely damaged aircraft successfully. I think if you search the Avnet data base for DC10 about 1973 you will find the full report.. .. .Another instance of a cabin fire and passenger deaths on a DC9 occurred as a result of repeatedly resetting a CB without following correct procedures.. .. .Experimentation is not a good idea.. . . . <small>[ 24 March 2002, 04:38: Message edited by: pterodactyl ]</small>