Mr Spaceman
Topic Author
Posts: 2723
Joined: Thu Mar 15, 2001 5:09 am

A Jet Engine Question-What's This?

Sat Sep 18, 2004 11:36 pm

Hi guys.

What are the small rectangular fairings with the square shaped holes in them, that are located on the bottom aft end of the engine cowlings on the 747-4 in this photo used for?

A wild guess on my part is that they are drain ports for oil that's leaked down onto the bottom of the engine cowling from the gearbox and bearing seals, etc.


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Photo © David Morrell - Avid Creations



After doing a good photo search of engine shots, I believe I've determined that the Pratt & Whitney PW 4056, General Electric GE CF6-80C, and Zeus Olympic engines all have this small fairing on their engine cowling. However, the Rolls Royce RB-211 does not. I guess the reason for this is simply based on a different engine design. What's the difference?

Here's some photos of engines that have this fairing .........

GE Engine.
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Photo © Mark Donoghue



Zeus Olympic Engine (you can just see it).
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Photo © Marian Musil



With the fairing (I don't know the engine types, but I'm sure they're either GE or PW engines).


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Photo © Anatol Kolendo
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Photo © Toby Willis



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Photo © Oliver Brunke



RB211 Engine (I believe) - without the fairing.


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Photo © Will Lanting



Without the fairing (I don't know the engine types for sure, but I believe 3 of the jets have RR RB211 engines).


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Photo © Glenn Stewart
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Photo © Greg Weir



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Photo © Darren Howie
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Photo © Jonathan Simmons




Does the JT9D-3A engine have this fairing? (I can't tell from the photo).


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Photo © Jack Hannen



Thanks,

Chris  Smile
"Just a minute while I re-invent myself"
 
air2gxs
Posts: 1443
Joined: Mon Jun 18, 2001 1:29 pm

RE: A Jet Engine Question-What's This?

Sun Sep 19, 2004 12:17 am

Though I'm sure of this particular engine it is probably the drain masts & the access area for the thrust reverser cowl latches.

As a note, the grain mast or gang drain does not gather fluids that have dripped onto the cowl (that usually goes overboard if its any large quantity, otherwise it stays and stains the inside of the cowl until wiped up), the gang drain gathers fluid from the accessory pads and accessories via tubing and dumps it overboard without allowing it to gather and puddle in the cowling. Any fluid coming from the drain mast (except oil after servicing) requires some attention. Whether anything has to be done depends on quantity, origin and type.
 
boeing767mech
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Joined: Fri Dec 15, 2000 5:03 pm

RE: A Jet Engine Question-What's This?

Sun Sep 19, 2004 2:17 am

Those fairings are for the Thrust reverser latches and also the Thrust Reverse guide rails for the translating cowl of the Thrust Reverser.

David
Never under-estimate the predictably of stupidty
 
Mr Spaceman
Topic Author
Posts: 2723
Joined: Thu Mar 15, 2001 5:09 am

RE: A Jet Engine Question-What's This?

Sun Sep 19, 2004 2:18 am

Hello Air2gxs.

Thanks for your reply.

OK, so if I understand you correctly, the square hole in the fairing is infact for drainage, but, it's not for oil, hydraulic fluids, etc, that have leaked and caused a puddle on the bottom of the engine cowling, it's for fluid from the accessory pads and accessories which is dumped overboard via tubing and the square hole is where these fluids are dumped overboard.

Am I close to understanding?

Also, do you know how the RR RB211 engines allow leaking fluids to be dumped overboard. Do their engine cowlings have drain masts that are flush with the cowling? - therefore they're not visible from side views.


Chris  Smile
"Just a minute while I re-invent myself"
 
air2gxs
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Joined: Mon Jun 18, 2001 1:29 pm

RE: A Jet Engine Question-What's This?

Sun Sep 19, 2004 3:01 am

A puddle in the cowling is not permitted, that's why this elaborate drain system exists. It also exists to help maintenance determine what is leaking and the rate. All engines, including APU's have a drain system.

The RR engines have drain ports that are flush with the cowl. The fairing itself houses part of the T/R system as Boeing767mech has stated.
 
Mr Spaceman
Topic Author
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RE: A Jet Engine Question-What's This?

Sun Sep 19, 2004 3:53 am

Hi guys.

> Air2gxs, Thanks Again, you stated ........

"it is probably the drain masts and the access area for the thrust reverser cowl latches"

> Boeing767mech, Thanks for your reply. You stated ........

"Those fairings are for the Thrust reverser latches and also the Thrust Reverse guide rails for the translating cowl of the Thrust Reverser."

Thanks for your info guys. Here's two more questions about these Thrust Reverser (TR's) fairings .......

Is that square hole in the fairing large enough for a mechanic to fit his/her head & shoulders into in order to inspect/service the thrust reverser guide rails, etc? Also, do the holes in these fairings have anything to do with drain masts?

Regarding part of my original question about why some jet engines have these cowling fairings while others don't, well, I understand now that only jet engines with "Cascade" type TR's (with aft moving cowlings during deployment) have these fairings. This explains to me why the RR RB211 engines don't have these fairings ......... because they use "Target" type TR's.

Here's some photos ........

Engines with Cascade type TR's with the fairings.


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Photo © Europix
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Photo © PixAir



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Photo © Tim Feise - APO Photos
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Photo © Christian Waser - Aviapix Zurich/Worldwide



Engines with Target type TR's and no fairings.


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Photo © Nicolas St-Germain
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Photo © Michael Fritz



This is neat stuff to learn about.  Big thumbs up

Chris  Smile

"Just a minute while I re-invent myself"
 
aloges
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Joined: Tue Jan 17, 2006 3:38 am

RE: A Jet Engine Question-What's This?

Sun Sep 19, 2004 8:20 am

That "Zeus Olympic Engine"... sweet!  Love They are GE CF6-50E2s.
Don't cry because it's over, smile because it happened.
 
air2gxs
Posts: 1443
Joined: Mon Jun 18, 2001 1:29 pm

RE: A Jet Engine Question-What's This?

Sun Sep 19, 2004 8:14 pm

The hole you see is the actual drain mast port. All the tubes run to this one area. It is not big enough to fit your head in. Usually, the fairing incorporates an access panel that is held closed by latches. When opened you gain access to the actual mast and the some of the T/R cowl latches. Undoing the latches allows you to open the T/R halves and gain access to the engine components under the cowl.

Note, not all engines are set up the same way. It all depends on the engine/airframe combination. An engine will always have some sort of drain mast, it varies as to where it discharges. If I remember correctly the drain mast on the tail engine of the MD11 discharges somewhere on the empennage (aft fuselage).

The fairing is just a convenient place to put the drains on some engines.

Look at the drain here:

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Photo © Anthony Cheng



The drain mast is an actual mast protruding into the airstream. (look at the #1 engine, #2 engine appears to have 3 objects: only 1 belongs to the engine, the other 2 are fuselage items).


 
Victor Hotel
Posts: 289
Joined: Fri Aug 25, 2000 8:29 pm

RE: A Jet Engine Question-What's This?

Sun Sep 19, 2004 8:25 pm

Sorry, A bit off topic but looking at the two aft main gear bay doors and the forward left main gear door, looks almost like contact with air bubbles under it. Does anyone know what this is?
 
air2gxs
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Joined: Mon Jun 18, 2001 1:29 pm

RE: A Jet Engine Question-What's This?

Sun Sep 19, 2004 10:22 pm

Victor,

Not sure what you're looking at. The only thing that looks like a "bubble" is the lower beacon.
 
Mr Spaceman
Topic Author
Posts: 2723
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RE: A Jet Engine Question-What's This?

Sun Sep 19, 2004 11:56 pm

Hi guys.

> Aloges, Thanks for explaining that the engine I thought was a Zeus Olympic engine (because of the photographer's comment), is actually a General Electric GE CF6-50E2 engine. You can even see the GE emblem on the side of the cowling. I understand now that it's the 747 that's named Zeus, not the engines!  Nuts I guess it's safe to say you like these sweet! engines.


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Photo © Marcel Venema - Dutch Ops



> Air2gxs, Thank You, for your info and explanations. Now I understand that these fairing's main purpose is for the Thrust Reverser system and that on some engines they provide a convenient place to put the drains.

I can clearly see the drain masts on the engines of the A340. I guess the pipe that can be seen protruding out from the bottom of this GE CF6-50E2 engine is a drain mast.


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Photo © Marian Musil



> Victor Hotel, I'm not sure about what you're looking at either, but, I suspect you might be looking at the curves of the #3 engine in the background directly behind the main landing gear.


Chris  Smile

[Edited 2004-09-19 16:57:00]
"Just a minute while I re-invent myself"
 
Victor Hotel
Posts: 289
Joined: Fri Aug 25, 2000 8:29 pm

RE: A Jet Engine Question-What's This?

Mon Sep 20, 2004 9:56 pm

Sorry didn't explain very well. The skin on the actual gear bay doors looks rippled, if you enlarge the first picture. The rest of the aircraft skin looks smooth except the main gear doors.

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