Sign in to follow this  
Followers 0
downscc

PMDG J41 Stop Latches

49 posts in this topic

With the JS4100 coming soon, I wanted to take a couple of minutes and prepare you for one of the lessons you will learn.The geared turboprop may be new to some of you, it has been for me. I want to give you a heads up about something called STOP LOCKS. These are mechanical latches on the props that hold the blade in flat pitch and they are required because: 1) Loss of oil pressure in the prop dome causes the blades to feather (this means they align with the airflow and present minimum drag desired if engine is out). 2) The electric starter/generator does not have enough power to spin feathered blades up to speed for start, the blades have to be in flat pitch.The reason this is important is because if you try to start when not in the stop locks, then it will simply crank until the starter shaft overheats and it will shear.The gotchya' is when you shut down and look at the props, gee! They look like they are on the stop locks, but walk away from the plane and in about a minute or so after the oil pressure bleeds off in the prop domes the blades will feather with or without you watching.The shutdown procedure includes pulling the power levers into reverse AFTER the RPM has decreased below 50%.If this isn't done right, you will end up with feathered props and you will have to either spend an extra few minutes running a special little oil pump that slooowly unfeathers the props before you start or you unawaringly try to start with feathered props and as I mentioned, that is not good.Here is a picture of feathered props (Not STOP LOCK):Compare it to the flat pitch blades on the STOP LOCKS:I hope this thread is not referenced too many times, but I am sure it will come up.

0

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

talk about details eh? thanks for the tip Dan!
Thanks for that... looks like you all are going to great effort to give us a true simulation of the J41.JB
0

Share this post


Link to post
Share on other sites

Cool reading, thanks for that Dan!The documentation over at smartcockpit.com talks of start latches... From what you describe, I can only conclude that it is one and the same thing...This is looking good, really good...Andrew

0

Share this post


Link to post
Share on other sites

start latches - stop latches, yeah that is my old brain working. Same thing.

0

Share this post


Link to post
Share on other sites

Please tell me that if you forget you have to hand crank the oil pump by pressing O repeatedly on your keyboard until they are back into position :( :( :( (yes I'm kidding)

0

Share this post


Link to post
Share on other sites

I thought fsx started the sim with the engines running!!! Or is this if you do a continuation flight?I bet I'll forget anyway lol. That's a super livery in the background by the way.John Ellison

0

Share this post


Link to post
Share on other sites

Hi Dan. Just wondering something. On Garretts there is a cannister that get pressurized after you get the engine going. On shutdown, for Garretts, if someone has ever heard this, you will hear a garrett speed up for a second or two on shutdown and then it will continue to shutdown. What this is is the cannister releasing the built up pressure to clear out the engine from fuel. If fuel is left uncleared, what happens is there will be residual fuel left on the fuel "injectors" and with the amount of heat in the engine will coke the fuel to the fuel nozzles and reduce the effectiveness of the nozzles which will require replacing. I am sure everyone has seen pilots get out and spin the props after shutdown. Some people think it is to cool the crankshaft properly but this is not true. It is to blow air through the nozzles so it can blow off any remaining fuel that is left on the nozzles. If I remember correctly this is "supposed" to be done within 2 mins of shutdown. Not sure where that theory of the crankshaft derived from but the crank shaft is too short and would not bend due to uneven cooling. Its like trying to bend a piece of 1 inch think plywood that is 2 inches long. You can't. Anyways I was wondering if the quick spool-up on engine shutdown was simulated Dan. thxJack

0

Share this post


Link to post
Share on other sites

Jack,You're referring to the Air Purge system, and on the TPE331, it happens automatically when the STOP buttons are pressed. You can hear the RPM increase momentarily, and the EIS will show a momentary increase in both RPM and EGT.The Air Purge system only works if the accumulators are charged, which requires that the engine be operated at greater than 95% RPM for a minimum of 5 seconds.The PMDG J41 simulates this perfectly.Nick

0

Share this post


Link to post
Share on other sites
I thought fsx started the sim with the engines running!!! Or is this if you do a continuation flight?I bet I'll forget anyway lol. That's a super livery in the background by the way.John Ellison
John,This will happen any time you have to start/stop the engines - yes the default is to start up with the engines running, but you can make a save flight that has whatever configuration you want. A lot of people like to go through the startup procedure and will likely use a "short turn" or "long turn" saved flight that has the aircraft in the condition a pilot would most likely find it in when starting a leg...
0

Share this post


Link to post
Share on other sites
Please tell me that if you forget you have to hand crank the oil pump by pressing O repeatedly on your keyboard until they are back into position :( :( B) (yes I'm kidding)
I don't know what the O key does, but it sounds like it's the same as what Dan mentioned about the oil pump (Unfeather) switch. Very simple to use, but if you don't start the engine quickly enough (I think you get a minute or so), the props will feather again. If you're anything like me you will end up using that switch more than you would like to. :(
0

Share this post


Link to post
Share on other sites
FANTASTIC!!!!!Best regards,Robin.
Robin, I echo your feelings QUADRUPLED, and Ryan......, I CAN HARDLY WAIT !!!! Note: Please pardon the shouting, but I'm very excited, because the J 41 seems to be about to take us even closer to, "As Real As It Gets" on a PC, and I am very impulsive :( I may have to stop eating for a while and get me a new, top notch PC to really do this aircraft and myself justice. Please,....Pretty Please let it be released tonight, I CAN'T BEAR IT ANY LONGER !!! There I am, shouting again !!AHH Well, better get back to flying my MD-11 :( Best Regards,GodfreyG :(
0

Share this post


Link to post
Share on other sites

BRILLIANT!!! Looking like this J41 is a fantastic tribute to the programmers and pmdg :( I'll be rubbing my hands with glee (not available in the shops) same as I was when with the Aerosoft Catalina startup - truly brilliant, foul the plugs and you've had it lol.And yes Ryan, I do like to start in cold&dark, adds to the whole experience :( John Ellison

0

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0