John Kerman 89

Hi, I downloaded RP1 a few days ago using the express install on CKAN. Really loving it so far! I noticed that the engines all have a ''Rated burn time'' but my engines seem to ignore this for some reason and just go on burning as long as there is fuel i.e. the Aerobee engine which is rated for 47 seconds went right up to 1 minute 30 seconds without failure. I sometimes get the odd engine losing thrust etc on some launches, just after launch so that part of the mod seems to be working. I noticed the mod test flight did install which I believe controls this so the mod is there. Is there something I need to change in the config files or something?