Mr Spaceman
Topic Author
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DC-9 & DC-10 Engine Questions?

Fri Sep 19, 2003 4:30 am

Hi Guys.

I have two jet engine questions.

1). In the first photo below of a Northwest DC-9-51 on short final, you can see a small trail of white smoke coming out of the bottom front area of the left engine.

I've never seen this before, so I'm wondering whether it's normal or not, as well as what the source of the white smoke would most likely be?


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Photo © Ken Cheung



Here's a shot of an MD-81's (DC-9-81) engine. Does the Northwest DC-9 with the smoke trail have the same engines? If so, can the sourse of the smoke be seen on this engine?

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Photo © Rainer Nyberg



2). In the photo below, what are the 3 copper coloured vertical tubes that are located at the front left side of the engine, on the outside of the case that's around the intake fan blades? What's their function?

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Photo © Bruce Leibowitz



Thanks,

Chris  Smile
"Just a minute while I re-invent myself"
 
cdfmxtech
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Joined: Wed Jul 05, 2000 11:37 am

RE: DC-9 & DC-10 Engine Questions?

Fri Sep 19, 2003 5:57 am

1). In the first photo below of a Northwest DC-9-51 on short final, you can see a small trail of white smoke coming out of the bottom front area of the left engine.
I've never seen this before, so I'm wondering whether it's normal or not, as well as what the source of the white smoke would most likely be?
Here's a shot of an MD-81's (DC-9-81) engine. Does the Northwest DC-9 with the smoke trail have the same engines? If so, can the sourse of the smoke be seen on this engine?
----------------------------------------------
That looks like it is coming from the Oil tank breather. The oil tank is pressurized excess pressure is vented overboard. oil is hot of course and depending on the conditions outside, it can be seen much more (although I will say I've never seen it that clearly).

The vent can be seen on the picture.
The oil tank can be seen on the picture on the fwd left side of the engine. Right above it is the Fuel/oil heat exchanger. On the aft side of the ht exchanger, you should be able to make out the oil tank fill cap. Look down and just a bit aft and you should see a duct protruding outboard with a flange on it (orange hue at the end). This is the vent. It has the orange kiss seal on it because it contacts the cowling.


2). In the photo below, what are the 3 copper coloured vertical tubes that are located at the front left side of the engine, on the outside of the case that's around the intake fan blades? What's their function?

Those are hydraulic filters. There are four (it cannot be seen, but its behind the fwd one).
 
timz
Posts: 6100
Joined: Fri Sep 17, 1999 7:43 am

RE: DC-9 Engine Questions?

Fri Sep 19, 2003 6:21 am

DC-9-51 and -81 have different engines.
 
cdfmxtech
Posts: 1319
Joined: Wed Jul 05, 2000 11:37 am

RE: DC-9 & DC-10 Engine Questions?

Fri Sep 19, 2003 2:13 pm

They are both JT8Ds with different dash numbers (Increased thrust w/other improvements). The basic stuff on the engine is the same.
 
Mr Spaceman
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RE: DC-9 & DC-10 Engine Questions?

Sat Sep 20, 2003 1:00 am

Hi guys.

> Cdfmxtech, Thanks You very much for your explanation. Your info was nice and clear to understand. I can easily see all the components that you mentioned in the MD-81 engine photo.

OK, so the smoke is being vented overboard via the oil tank breather vent because there's excessive pressure in the oil tank.

In the first 2 photos below, I believe you can see the small vent pipe on the forward bottom part of the DC-9's left engine cowling where excessive oil pressure (and the white smoke in the photo) is vented overboard. The duct that's protruding out of the oil tank on the engine with the flange on it sure appears to be in the perfect location to contact the engine cowling where the outside vent pipe is attached.


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Photo © Ryan C. Umphrey
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Photo © Ken Cheung



I guess this DC-9 on short final could also be venting excess oil pressure during the shot, but you just can't see it because of weather conditions like you mentioned.


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Photo © Ken Cheung



Also, Thanks for explaining that the copper tubes on the front of the DC-10's engine are hydraulic filters. Great info  Big thumbs up

Chris  Smile
"Just a minute while I re-invent myself"
 
cdfmxtech
Posts: 1319
Joined: Wed Jul 05, 2000 11:37 am

RE: DC-9 & DC-10 Engine Questions?

Sat Sep 20, 2003 1:31 am

A correction:
It's called the Gearbox breather. The gearbox pressure is vented in addition to oil tank pressure. I got a chance to see it closer and it is not connected to the oilt tank (not directly). It is on the gearbox.

[Edited 2003-09-19 18:32:12]
 
Mr Spaceman
Topic Author
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RE: DC-9 & DC-10 Engine Questions?

Sat Sep 20, 2003 4:14 am

Hello Cdfmxtech.

Ok, so it's actually called the Gearbox Breather. Thanks. Big grin

I've been wondering. Because you mentioned that the stream of smoke from the vent on the engine cowling can be seen better when the conditions outside are right, is it possible that it's only excessive hot air (from pressurizing the hot oil & gearbox), and NOT smoke that's being vented overboard which condenses into visible steam when it's cool enough outside?

Is that a trail of white water vapour or smoke in the first DC-9 photo?

Chris  Smile


"Just a minute while I re-invent myself"
 
BR715-A1-30
Posts: 6525
Joined: Thu May 30, 2002 9:30 am

RE: DC-9 & DC-10 Engine Questions?

Sat Sep 20, 2003 8:07 am

The BR715 has the same thing. On really cold days, when a plane is taxiing to the gate, you can see smoke coming out. The DC9-51 has the JT8D-17 engine while the DC9-81 have JT8D-217A engines (-219 in SAS's case) The MD-82 has JT8D-217C, and the MD-83,87, and 88 have JT8D-219 engines
Puhdiddle

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