ReverseThrust
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Dirty / Burnt Airline Engines.

Fri Jun 02, 2006 11:00 pm

I have always wondered why, on some types of aircraft, the rear portion of the engine is sometimes dirty: Airbus A319/20/21 all types of engines. LH, IB, BD and AF are notable examples that I have seen on here.

On MD80's and DC9's the right engine in particular seems burned across the top of the metal part of the reverser.

I am not sure, but have a feeling it may be caused by reverse thrust...

How is this actually caused and why does it only happen sometimes?
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FlyDeltaJets
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RE: Dirty / Burnt Airline Engines.

Fri Jun 02, 2006 11:04 pm

I thinks it is caused by lack of soap and water application for many years

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ReverseThrust
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RE: Dirty / Burnt Airline Engines.

Fri Jun 02, 2006 11:05 pm

LOL - Probably in AF's case it is!
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trent900
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RE: Dirty / Burnt Airline Engines.

Fri Jun 02, 2006 11:16 pm

Quoting ReverseThrust (Thread starter):
On MD80's and DC9's the right engine in particular seems burned across the top of the metal part of the reverser

I think the deposits you've mentioned on these aircraft is due to the APU exhaust which is situated in the side of the rear fuselage. As for other aircraft I dont know, Im sure a bit of a wash can get the 'dirt' off.

D.
 
ReverseThrust
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RE: Dirty / Burnt Airline Engines.

Fri Jun 02, 2006 11:32 pm

OK, thanks - but on Airbus/Boeing I am a little more curious then. I am quite new to forums and haven't yet worked out how to get pics off of a.net into my posts to provide examples.

Cheers for all relevant advice on the question in hand.

Reverse.
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FlySSC
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RE: Dirty / Burnt Airline Engines.

Fri Jun 02, 2006 11:56 pm

In the case of the B737-200, this pic. shows you exactely why the rear part of the fuselage is/was often so dirty :

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Some more :


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I guess the reasons are the same on the aircraft types you mentionned, with less impacts on the fuselage itself because of the thrust reverse system's conception

[Edited 2006-06-02 17:01:11]
 
ReverseThrust
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RE: Dirty / Burnt Airline Engines.

Sat Jun 03, 2006 12:06 am

OK, Thanks again - that one was obvious though, which was why I didn't specifically mention it.

I thought it wouldn't have been a question which was too technical for an answer here. Is the dirt on ther CFM/IAE Engines caused by heat on reverse or by a particularly hard reverse?

KLM's engines on the Boeing 733/734 aircraft are always quite dirty on the aft part of the engine itself too.
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HAWK21M
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RE: Dirty / Burnt Airline Engines.

Sat Jun 03, 2006 2:37 am

Thats why Aircraft should be cleaned regularly. Smile
regds
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miamiair
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RE: Dirty / Burnt Airline Engines.

Sat Jun 03, 2006 2:49 am

Quoting ReverseThrust (Thread starter):
MD80's and DC9's the right engine in particular

The APU exhaust is on the right side of the fuselage above the rear part of the pylon.
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jetstar
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RE: Dirty / Burnt Airline Engines.

Sat Jun 03, 2006 7:24 am

On the P&W JT8 powered B-737’s, they use the old style clam shell thrust reversers. To prevent the reversers from blowing any debris on the runway forward into the engine intake when reverse thrust is used, the reversers are installed slightly rotated. Looking from the rear, the #1 engine (left side) reverser is rotated about 30 degrees clockwise and the #2 engine (right side) reverser is rotated the same amount but counter clockwise. The 737-300 and up reverser system is different so they don’t have this problem.

Because of this the exhaust that is deflected from the upper reverser bucket hits the fuselage and leaves its telltale stains in the form of carbon dust. In the late 70’s into the early 80’s the JT8 engines was one of the smokiest engines out there. Watching a 727 or 737 climb out after takeoff all you would see was a black trail of smoke. Because of pressure from the FAA and airline operators, P&W redesigned the combustion chambers to reduce to almost nothing the visible black smoke. Another benefit to this redesign was longer turbine blade life because the carbon exiting the engine eroded the turbine blades.

Before this modification, the 737’s were the filthiest airplanes because of the design of the thrust reverser system left enormous stains on the fuselage. These photos are nothing as to what the airplanes looked like with the old combustion chambers.
 
BDKLEZ
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RE: Dirty / Burnt Airline Engines.

Sat Jun 03, 2006 7:37 am

Quoting Miamiair (Reply 8):
The APU exhaust is on the right side of the fuselage above the rear part of the pylon.

The APU exhaust is to blame for these dirsty tails as well. The situation is only made worse by the fact that these aircraft tails are painted white.


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ReverseThrust
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RE: Dirty / Burnt Airline Engines.

Sat Jun 03, 2006 7:54 am

OK, I'll try and make myself a bit clearer. In the following pictures, all of the aircraft have a stained rear part of the actual engine - nothing to do as far as I'm aware with the APU at all on these particular aircraft. It seems this is not something which always occurs, but what I want to know is HOW this actually happens.... it must get there somehow....


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Thanks.
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RE: Dirty / Burnt Airline Engines.

Sat Jun 03, 2006 8:10 am

Quoting ReverseThrust (Thread starter):
On MD80's and DC9's the right engine in particular seems burned across the top of the metal part of the reverser.

That is correct... The APU Exhaust on the DC9/MD80 is situated right there next to the reverse thrust, so the heat/deposits burn the shell. If you look on some DC9s, the left engine is burnt due to a switch from maintenance.
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RE: Dirty / Burnt Airline Engines.

Sat Jun 03, 2006 8:27 am

Quoting Jetstar (Reply 9):
Watching a 727 or 737 climb out after takeoff all you would see was a black trail of smoke

You are so right about that one. Before jet engines went "smokeless" the rear halves of a lot of aircraft were very black. In fact, some were so bad that it looked like the carbon was caked on the fuselage! Some of those engines were so smoky, you'd think they were running on coal!
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ReverseThrust
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RE: Dirty / Burnt Airline Engines.

Sat Jun 03, 2006 8:31 am

I'm not referring to the back of the aircraft on my question though, very specifically, the engine itself.

That said however, I am flying the TU134 twice in August... now that is a dirty aircraft which runs on coal if ever there was one.

U only need to view some of the videos on www.flightlevel350.com to bear witness to that.... but make sure u got the volume turned up good and proper!
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474218
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RE: Dirty / Burnt Airline Engines.

Sat Jun 03, 2006 8:52 am

What you see is soot, just like the stuff that comes out of a car exhaust If you cleaned it off every flight it would be right back as soon as the engine is started again.
 
FlyDeltaJets
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RE: Dirty / Burnt Airline Engines.

Sat Jun 03, 2006 8:57 am

Quoting Type-rated (Reply 13):
You are so right about that one. Before jet engines went "smokeless" the rear halves of a lot of aircraft were very black. In fact, some were so bad that it looked like the carbon was caked on the fuselage! Some of those engines were so smoky, you'd think they were running on coal!

When did jet engines go smokeless. I see smoke trails coming from the back of all types of new aircraft on take-off
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andrewuber
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RE: Dirty / Burnt Airline Engines.

Sat Jun 03, 2006 9:18 am

The dark stain you see is not a "burn", it is the soot from the kerosene. I have crews who remove this stuff on a daily basis.

Sometimes the paint will get discolored from turbine oil on the cowlings - especially JT8D powered aircraft (such as DC9, 727, 737-200). The engines will look orange or brown - and that discoloration does not come off.

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jetstar
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RE: Dirty / Burnt Airline Engines.

Sat Jun 03, 2006 12:27 pm

Quoting FlyDeltaJets (Reply 16):
When did jet engines go smokeless. I see smoke trails coming from the back of all types of new aircraft on take-off

The engines never went smokeless, all that was done was to greatly reduce the visible carbon particles in the exhaust. What you see today coming out of a jet engine is nothing like the older and dirtier jet engines.

The same thing was done to diesel engines. Years ago you would see large amounts of black smoke coming out of the exhaust pipes of large trucks and buses. On 18 wheel trucks, the exhaust soot would leave black stains on the trailers.

The diesel engine manufacturers under pressure from the EPA were forced to redesign their engines to meet the lower visible particle requirements, the same thing that the jet engine manufacturers had to do. While truck engines had no requirement to retrofit the change, as the jet engines went through overhaul they were modified to reduce the visible carbon particles so within a few years, all the dirty jet engines were cleaned up or in the case of the real old smokers like the CV-880’s or early B-707’s and DC-8’s were retired.
 
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HAWK21M
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RE: Dirty / Burnt Airline Engines.

Sat Jun 03, 2006 8:52 pm

Quoting Jetstar (Reply 9):
To prevent the reversers from blowing any debris on the runway forward into the engine intake when reverse thrust is used, the reversers are installed slightly rotated.

Another Main Reason was that the earlier T/R was lifting the Aircraft off the Ground & reducing Brake Efficiency.Hence the Tilt.
regds
MEL
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RE: Dirty / Burnt Airline Engines.

Sat Jun 03, 2006 11:27 pm

Thanks, Jetstar for explaining more of this.

Back in the 60's jets would leave long black streams of very black smoke coming out of each engine. It would trail for miles behind the aircraft. Then in the 70's they redesigned some of the engines as noted in this thread and they became almost smokeless when compared to the previous generation of engines. The jet engines of today put out nothing like the ones in the 60's did, so even though I mentioned them to be smokeless, they still do leave a little bit of smoke.
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320tech
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RE: Dirty / Burnt Airline Engines.

Sun Jun 04, 2006 5:09 am

In the following pictures, all of the aircraft have a stained rear part of the actual engine

If you're referring to the streaking that is coming from the gap between the fan cowl and the thrust reverser, that's either an oil or hydraulic leak, or else it's from the oil fill point, where someone missed. Any of those will cause black streaks on the reverser.
The primary function of the design engineer is to make things difficult for the manufacturer and impossible for the AME.
 
dan2002
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RE: Dirty / Burnt Airline Engines.

Sun Jun 04, 2006 10:09 am

Woah, check out these stains!


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