Hello all! I've been using the J41 for about a year now and its simply the best addon aircraft out there at the moment in my mind! I really enjoy short 1 hour or less hops between regional airports and I love flying through clouds and over nice sceenry rather then being up at FL35 with nothing to see. Its complexity and detail give me great pleasure every day, money well spent! A questions i've wondered for the last while is that what does the three minute cooldown period mentionned in the manual mean? After landing I pop the condtion levers to taxi and head to the gate then just shut down as soon as I get there. I don't see any noticable fast drop in EGT by idling for three minutes from toucdown so don't see any benefit to doing this. I only today seen some forum posts here discussing the method called the "ventilation run" to run the starter and cool EGT before start so I wondered is this what everyone does in between short legs to enable another flight to happen or what should the correct procedure be?

Paul....Gentle reminder that they like you to sign your posts on this siteDave Cook

It's not the EGT that matters for the cool down, it's the temperature of the components and engine liquids. The components (the housings, bearings, etc) have all been heated up to a rather high temperature, but are still moving, which is a good thing. If you take hot metal and stop it from moving while it is still hot, the metals next to each other will continue to heat each other up mutually and you run the risk of temperature-locking the components (they get so hot that they melt and freeze together, essentially). Also, the hotter the components are, the more malleable they are, meaning, if they haven't cooled appropriately, they can melt slightly, but still work, which increases the wear on that part and surrounding parts in the future. If you ever have a friend replace his turbo in his car, take a look at the turbo vanes. If he didn't use the appropriate cool-down period on the turbo, the vanes will have an odd distortion (some of the vanes will droop more than others). By keeping the parts rotating during the cool down, gravity has less of a chance to distort the hot components. Once they aren't as hot, they are less malleable and shutting down will cause no harm as they continue to cool down.On startup, EGT is the important matter, and that's where the ventilation run comes into play. Normally, you won't need to make the run because the rampers take time unloading the bags, and the people in the back take their time leaving (ever leave a widebody from the back? takes forever thanks to people not having any sense about them), and then you have to wait for the next flight's bags and pax to show up, which also takes time. By the time all that's done, your EGT is normally within the acceptable range.

Just to add quickly...I'm not to sure how common in is with the JS41, but where I work I have frequently seen neighbouring companies Metros and JS31 utilise a rather common but unique to garrets cool-down procedure.On some frigid cool days, it isn't uncommon to see a FO run out after shutdown and start giving the ol' prop a good bunch of some vigourous spins. I've worked with some TPE331's only in AME training, and it was always stressed to us that these Garetts run HOT, relative to the free-turbine engines we may be more used too. Anyways, in these frigid cold temperatures, there is a real risk of cooling the exterior of the powerplant far faster than the guts inside, Which causes a real risk of "droop", as a Metro FO once explained to me. Basically the turbine shaft will droop and bend itself out of round, and as a precaution in cold weather operations, a pretty good feel of the prop rotating is observed for resistance in once spot during a turn. This may signify a bad thing.By giving the engine a good deal of turns you no only help cool the engine down a bit, you also help keep the thing from tweaking itself apart, much like the dangers of shock cooling a piston engine. By drawing in some cool air by hand, it helps equalise the cooldown throughout the whole engine, but like most thing too much is just as bad; you don't want to draw too much -30 air inside as well.Maybe Rob can shed light on what the procedures were in the much milder (sometimes!) climes of the eastern US.Patrick Houghton