"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

The problem methinks is the starter gears will overheat, and the risk of a starter overspeed (possibility of a wheel burst even).

Some start valves have a manual override handle, don't they?

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

I would say that the procedure provided by your company is the correct one.

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.

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.
:ok:

cod

737NG
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

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.

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

Cod,
you are right.
The Starter have a clutch that slip over when the N2 is higher than the speed of the starter:
http://img269.imageshack.us/img269/4...utch0xp.th.jpg

Ingo

Quite right guys,

So........

.........What you have now is a starter motor fed with Say 35psi and NO LOAD!!:ooh: :ooh:

A recipe for disaster. Sutting down is the only option.

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

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.