sudden
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Engine Start DC-10

Tue Jul 31, 2001 6:02 pm

Was listening to a DC-10 at Schiphol when enginestart was in progress. Did not sound very correct when they tryed to start cause it came a wooosh followed by a boom! This strange sound came for 3-4 times and then the engine started. Same sound for all 3 engines. Can someone spread some light over this!? Have heard DC-10's start before, and this was the first time I ever heard this.
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DC10Tony
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RE: Engine Start DC-10

Tue Jul 31, 2001 9:27 pm

If that was the CF-6, I think I may be able to explain from my perspective as a ramp agent. When we're pushing out DC-10s, they don't sound as smooth as an A330 when they start, it's more like "flicking on a light switch", they start all of a sudden. The "woosh" you heard was probably the engine spooling up like as soon as the captain hit the button. Then like 2 seconds aftera the "woosh", comes the "boom". Have you ever seen a welder light a solder? You know how when he turns the gas on for it it makes like a hiss, and then when he lights the match to it, it makes like a poof sound? That's what the DC-10 sounds like when it's starting its engines up. Hope this helped.
 
sudden
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RE: Engine Start DC-10

Tue Jul 31, 2001 9:37 pm

DC-10Tony! Thanks for your answer! I work as a rampagent to. And to me it sounded like it was the APU who was screaming for "help". Heard the same "boom" from a nother flight one time, but that was the APU and that flight was towed to the hangar.
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VC-10
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RE: Engine Start DC-10

Wed Aug 01, 2001 2:39 am

I would say it was the APU surging due to an APU compressor inlet guide vane defect.
 
sudden
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RE: Engine Start DC-10

Wed Aug 01, 2001 3:44 pm

VC-10....

I guess this does not make any problems to the flight cause the bird took to the sky. Otherwise they would probably have stayed on the ground, or am I wrong?
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VC-10
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RE: Engine Start DC-10

Wed Aug 01, 2001 6:42 pm

As the APU is not used in flight, there would be no problem. They could have inop'd the APU and used an air start truck to start the engines, but if the defect had just developed the crew probably thought it quicker to try and use the APU (slot restrictions etc)
 
sudden
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RE: Engine Start DC-10

Wed Aug 01, 2001 9:37 pm

Still makes me wonder why they kept on trying when the APU sounds like that! Like I said, heard this a nother time but a diffrent A/C type, and that one was grounded. No questions asked.
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VC-10
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RE: Engine Start DC-10

Wed Aug 01, 2001 11:51 pm

Was it the operators main base or one of their outstations ?
 
DC10Tony
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Sudden

Thu Aug 02, 2001 4:35 am

For the first time yesterday, I heard that "screaming" noise."

I was at the bottom of hold 5 on an A330-200 and all of a sudden it sounds like there was someone in the APU saying, "hey...hey...hey...", with like a raspy smoker's voice. Man what a weird experience that was.
 
DC-10Tech
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RE: Engine Start DC-10

Tue Mar 04, 2008 7:35 pm



Quoting VC-10 (Reply 3):
I would say it was the APU surging due to an APU compressor inlet guide vane defect.

Yes and no.

What you were hearing was the APU stalling or 'surging' after each starter cutout. This is caused by a faulty APU surge valve that does not proberly dump the excess 'surge' air overboard after the demand for that extra air is removed.

A surging APU can sound like a small cannon firing rapidly. Big grin

Quoting SUDDEN (Reply 6):
Still makes me wonder why they kept on trying when the APU sounds like that! Like I said, heard this a nother time but a diffrent A/C type, and that one was grounded. No questions asked.

Often times during engine start, you can't even hear the APU surging. Usually you feel it in your seat before you hear it (it feels like someone is banging a hammer on the floor)
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HAWK21M
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RE: Engine Start DC-10

Tue Mar 04, 2008 9:00 pm

This is one Old thread.What you doing.Searching for DC10 Discussions  wink 

Quoting DC-10Tech (Reply 9):
Often times during engine start, you can't even hear the APU surging

Is this a common problem with the DC10 APU,regarding susceptable to surging?

regds
MEL.
I may not win often, but I damn well never lose!!! ;)
 
DC-10Tech
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RE: Engine Start DC-10

Tue Mar 04, 2008 11:16 pm

Quoting HAWK21M (Reply 10):
This is one Old thread.What you doing.Searching for DC10 Discussions

It came up as a similar thread at the bottom of a thread I was posting in. I didn't even notice how old this thread was. 

Quoting HAWK21M (Reply 10):
Is this a common problem with the DC10 APU,regarding susceptable to surging?

Yes, its quite common. Its not a problem with the APU, its an issue with the APU surge valve itself. The valve has a filter on it that gets dirty and sometimes cleaning it will clear the problem. If not, you change the valve and everything is good.

When you have a bad surge valve, the only time you'll notice is if you have the APU isolation valve open (which causes the APU N1 to increase and the VGV's to open to increase bleed air pressure) and you are not using the available air.

An old trick is to turn on an AC pack before opening the isol valve so that the surge air is immediately used by the pack to prevent the APU from surging.

If you have an APU surging like this, you can place the APU pneumatics on MEL and go on your way.

[Edited 2008-03-04 15:17:16]
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avioniker
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RE: Engine Start DC-10

Wed Mar 05, 2008 4:01 am



Quoting DC-10Tech (Reply 11):
Yes, its quite common. Its not a problem with the APU, its an issue with the APU surge valve itself. The valve has a filter on it that gets dirty and sometimes cleaning it will clear the problem. If not, you change the valve and everything is good.

Gee, nice to hear someone was awake and listening.
I have to say, though, it isn't that common in an airline that is up on its maintenance. The filter should have been changed before it got dirty enough to cause the stall. I'd be checking the B nut first like I said in the first place. . . how soon we forget, eh?

 Smile
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DC-10Tech
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RE: Engine Start DC-10

Wed Mar 05, 2008 6:24 am



Quoting Avioniker (Reply 12):
Gee, nice to hear someone was awake and listening.
I have to say, though, it isn't that common in an airline that is up on its maintenance. The filter should have been changed before it got dirty enough to cause the stall. I'd be checking the B nut first like I said in the first place. . . how soon we forget, eh?

Listening to what?
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HAWK21M
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RE: Engine Start DC-10

Thu Mar 06, 2008 10:10 am



Quoting DC-10Tech (Reply 11):
If you have an APU surging like this, you can place the APU pneumatics on MEL and go on your way.

What would the MEL declare u/s.....Is it the Surge valve?
regds
MEL.
I may not win often, but I damn well never lose!!! ;)
 
DC-10Tech
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RE: Engine Start DC-10

Thu Mar 06, 2008 11:17 pm



Quoting HAWK21M (Reply 14):
What would the MEL declare u/s.....Is it the Surge valve?

The APU pneumatic supply would be placed on MEL. If you don't use the APU pneumatics, the surge valve is no longer a factor.
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avioniker
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RE: Engine Start DC-10

Fri Mar 07, 2008 4:36 am



Quoting DC-10Tech (Reply 15):
The APU pneumatic supply would be placed on MEL. If you don't use the APU pneumatics, the surge valve is no longer a factor.

You're quoting the MEL you're familiar with.
The master is a little different and there are operator customizations to deal with.
MEL has a valid alternative. A number of operators, not yours, allow you to defer the specific malfunctioning item. A lot of operators have pilots with a lot more experience who understand what the loss of a specific valve means to their operational capabilities.

Listening to the instructor, what else would I have meant???
 Smile
One may educate the ignorance from the unknowing but stupid is forever. Boswell; ca: 1533
 
DC-10Tech
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RE: Engine Start DC-10

Fri Mar 07, 2008 5:09 am



Quoting Avioniker (Reply 16):
You're quoting the MEL you're familiar with.

I'm quoting the MEL I"m familiar with on the KC-10 and on the three DC-10 operators I've worked for. You can't defer the surge valve without deferring the isol valve closed. (hence, apu pneumatic function inop)

Quoting Avioniker (Reply 16):
Listening to the instructor, what else would I have meant???

I've never had a DC-10 class at big purple, but I'm glad they're teaching that in the class. Big grin
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HAWK21M
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RE: Engine Start DC-10

Fri Mar 07, 2008 10:27 am



Quoting DC-10Tech (Reply 17):
You can't defer the surge valve without deferring the isol valve closed. (hence, apu pneumatic function inop

This is interesting.On the B737/757 MEL Im aware of,theres always an individual item that is declared u/s & subsequently the system.
regds
MEL
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DC-10Tech
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RE: Engine Start DC-10

Fri Mar 07, 2008 5:45 pm



Quoting HAWK21M (Reply 18):
This is interesting.On the B737/757 MEL Im aware of,theres always an individual item that is declared u/s & subsequently the system.

Well, the surge valve is part of the APU pneumatics, if its not working and you use APU pneumatics, you can damage the APU, so you defer the next-higher system, which would be the pneumatic function.

The only individual component in the APU pneumatics on the -10 you can defer is the load control or 'isol valve' operation. This means that the valve the supplies APU bleed air to the aircraft doesn't open and close properly. If you just defer this valve, you can have mx manually open and close the valve as needed (ie, for engine start), allowing you to still use the APU pneumatics.

On the engines its different. You can defer a fan air valve or high stage valve and still use the pneumatics on that engine (with some restrictions).
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ex52tech
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RE: Engine Start DC-10

Sat Mar 08, 2008 3:53 am



Quoting DC-10Tech (Reply 17):
I'm quoting the MEL I"m familiar with on the KC-10 and on the three DC-10 operators I've worked for. You can't defer the surge valve without deferring the isol valve closed. (hence, apu pneumatic function inop)

Same for me, KC-10s, and two different DC-10 operators, and you either had APU pneumatics, or you didn't as far as the MEL was concerned. One trick I have used when dealing with a faulty surge valve, we would snap on one of the PACs right as the engine starter would cut out, and help ease the pneumatic shock load off the surge valve.
"Saddest thing I ever witnessed....an airplane being scrapped"
 
DC-10Tech
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RE: Engine Start DC-10

Sat Mar 08, 2008 4:19 am



Quoting Ex52tech (Reply 20):
One trick I have used when dealing with a faulty surge valve, we would snap on one of the PACs right as the engine starter would cut out, and help ease the pneumatic shock load off the surge valve.

Yep, like I said in post 11.

Quoting DC-10Tech (Reply 11):
An old trick is to turn on an AC pack before opening the isol valve so that the surge air is immediately used by the pack to prevent the APU from surging.

These two techniques were great when you were on the road and needed that APU air.
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ex52tech
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RE: Engine Start DC-10

Sat Mar 08, 2008 5:09 am



Quoting DC-10Tech (Reply 21):
Yep, like I said in post 11.

OH....hey.....sorry about that, I totally missed your post. I hate it when I do that.  ashamed 
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DC-10Tech
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RE: Engine Start DC-10

Sat Mar 08, 2008 2:55 pm



Quoting Ex52tech (Reply 22):
OH....hey.....sorry about that, I totally missed your post. I hate it when I do that.

Oh, I didn't mean it like that, you mentioned the trick during engine start. I was mentioning the trick when you first open the isol valve. Big grin
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