"Start Vlv NO close" after MES
Thread Starter
Joined: Jun 2005
Posts: 51
Likes: 0
From: position data invalid
"Start Vlv NO close" after MES
i've been an observer of this site for some time now but until recently haven't posted. i'm looking to find out the correct procedure for when start valve will not close after main engine start on airbus or boeing aircraft.
training and run-up guide at my carrier tells me to isolate pneumatics on effected engine and shutdown.
isolate pneumatics, ok, but why is there a need to shutdown right away?
why shouldn't i be able to continue my run (with the particular engine isolated), complete my ground checks as required, then shutdown?
heck, i could even call our storeman on my mobile and ask him to deliver a new start vlv while i complete my run.
saves time and returns the aircraft back to service quicker!!
of course, i would never contravene company policy
feedback appreciated
cod
training and run-up guide at my carrier tells me to isolate pneumatics on effected engine and shutdown.
isolate pneumatics, ok, but why is there a need to shutdown right away?
why shouldn't i be able to continue my run (with the particular engine isolated), complete my ground checks as required, then shutdown?
heck, i could even call our storeman on my mobile and ask him to deliver a new start vlv while i complete my run.
saves time and returns the aircraft back to service quicker!!
of course, i would never contravene company policy
feedback appreciated
cod
Joined: Jul 2003
Posts: 53
Likes: 0
From: AUSTRALIA
CLO,
The reason is, depending on the aircraft and installation, even with pneumatics isolated the starter can still be supplied with pneumatics from its own engine if the start valve is open.
This applies to crew actions as well, not so much for the more modern aircraft but it is for the 727, 747 Classic.
VTM
The reason is, depending on the aircraft and installation, even with pneumatics isolated the starter can still be supplied with pneumatics from its own engine if the start valve is open.
This applies to crew actions as well, not so much for the more modern aircraft but it is for the 727, 747 Classic.
VTM
Joined: Jul 1999
Posts: 352
Likes: 0
From: Europe
i'm looking to find out the correct procedure for when start valve will not close after main engine start on airbus or boeing aircraft.
As has been mentioned there is a real risk of starter overspeed, especially if de-clutch speed is reached before the bleeds are isolated.
I'm not sure that continuing an engine run with a starter that might have popped its lid is such a good idea.
Also, if you look in the QRH for your particular airplane, I'm sure that the drill is similar to the one your run-up guide.
Thread Starter
Joined: Jun 2005
Posts: 51
Likes: 0
From: position data invalid
i guess if i allow the the starter to continue to operate as i complete my ground checks, i might as well ask my storeman to bring me a new starter as well
so company policy it remains.
thank you for the input.
cod
so company policy it remains.
thank you for the input.
cod
Joined: Apr 2004
Posts: 775
Likes: 2
From: near EDDF
i'm looking to find out the correct procedure for when start valve will not close after main engine start on airbus or boeing aircraft.
Start the Engine Procedure (Normal Start) [TASK 71-00-00-800-808-F00]
...
If the starter disengaged at more than 56% N2 or does not disengage, do these steps:
(a) Manually put the start switch to the OFF position.
(b) Look at the center DU to see if the START VLV OPEN maintenance message goes out.
(c) If the START VLV OPEN maintenance message does not go out, move the start lever to the CUTOFF position to stop the engine
...
HIH
Ingo
Joined: Feb 2005
Posts: 257
Likes: 0
From: Sydney
If the start valve remains open after eng start then the starter will still be engaged.
As it is designed to disconnect at roughly 50% idle speed you will probably be picking up pieces of starter off the ground if you actually get to idle with the starter still engaged.
Many messages are inhibited during eng start but a faulty start valve is not one of them because immediate action is required.
As it is designed to disconnect at roughly 50% idle speed you will probably be picking up pieces of starter off the ground if you actually get to idle with the starter still engaged.
Many messages are inhibited during eng start but a faulty start valve is not one of them because immediate action is required.
Thread Starter
Joined: Jun 2005
Posts: 51
Likes: 0
From: position data invalid
disagreed numbskull,
regardless of whether start valve is open or closed, the starter 'disengages' from spooling up engine long before it reaches idle (aircraft engine speed exceeding pawl liftoff speed of starter drive shaft assembly).
as VTM mentioned, since the starter can still be supplied with pneumatics from its own engine, the starter will still continue to motor. the speed at which it continues to operate is determined strictly by the pneumatic pressure, not engine speed.
none the less, because i don't know what effect prolonged motoring might have on the starter and company procedure dictates, i will s/d immediately.
rgds
cod
regardless of whether start valve is open or closed, the starter 'disengages' from spooling up engine long before it reaches idle (aircraft engine speed exceeding pawl liftoff speed of starter drive shaft assembly).
as VTM mentioned, since the starter can still be supplied with pneumatics from its own engine, the starter will still continue to motor. the speed at which it continues to operate is determined strictly by the pneumatic pressure, not engine speed.
none the less, because i don't know what effect prolonged motoring might have on the starter and company procedure dictates, i will s/d immediately.
rgds
cod
Joined: Apr 2004
Posts: 775
Likes: 2
From: near EDDF
Cod,
you are right.
The Starter have a clutch that slip over when the N2 is higher than the speed of the starter:
Ingo
you are right.
regardless of whether start valve is open or closed, the starter 'disengages' from spooling up engine long before it reaches idle (aircraft engine speed exceeding pawl liftoff speed of starter drive shaft assembly).
Ingo
Joined: Feb 2005
Posts: 257
Likes: 0
From: Sydney
Cod you are right about the starter disengaging at higher eng speeds.
However the danger is that it won't disengage as normal now that it has pneumatic power still driving it. At the very least it will be spinning faster than normal before it disengages.
The duty cycle for most starters is 5 min.
So if the starter does disengage properly while while still being driven pneumatically (and then under no load) you only have minutes before the starter self destructs
However the danger is that it won't disengage as normal now that it has pneumatic power still driving it. At the very least it will be spinning faster than normal before it disengages.
The duty cycle for most starters is 5 min.
So if the starter does disengage properly while while still being driven pneumatically (and then under no load) you only have minutes before the starter self destructs
Last edited by numbskull; 11th July 2005 at 21:47.
Joined: Oct 2004
Posts: 18
Likes: 0
From: UK
I seem to remember a TU154M (?) #2 engine fire after take off - attributed to start valve open after start - starter continued to run - overheated - and caught fire at some point - aircraft crashed and was destroyed.
Oh yes, and people were killed.
So, if we get a start valve not closed type message after start, lets shut it down then shall we.
It may be your mate on the headset who gets showered with red hot bits of starter turbine as well.
Oh yes, and people were killed.
So, if we get a start valve not closed type message after start, lets shut it down then shall we.
It may be your mate on the headset who gets showered with red hot bits of starter turbine as well.
