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NW Flight -- Sparks During Reverse Thrust? (video)  
User currently offlineTweety From Bulgaria, joined Aug 2009, 0 posts, RR: 0
Posted (7 years 11 months 2 days ago) and read 3611 times:

A friend was on N583NW SEA-MSP (a 752) several days ago, and seated by the PW2040 engine (#2?), just aft of the L2 door, and filming the landing roll.

He was rather startled to see what appeared to be sparks coming out of the engine while reverse thrust was selected and engine spooled up. The sparks went away when reverse thrust was de-selected. As far as he knows, the landing was otherwise normal.

Question: what exactly was this phenomenon? Normal or abnormal? Normal but something that's only seen at night? FOD-induced or something else?

http://206.251.255.134/~dsf/N583NW-landing.wmv

(Can't promise the link will always be valid, but for now, it's up.)

File is 1.4 MB and about 26 seconds long.

18 replies: All unread, jump to last
 
User currently offlineCCA From Hong Kong, joined Oct 2002, 841 posts, RR: 14
Reply 1, posted (7 years 11 months 1 day 23 hours ago) and read 3598 times:

Looks like foreign objects (small stones etc) impacting the blades, I've see this before during an engine ground run up to high power but it doesn't last long as the aircraft isn't moving, once the debris is sucked up there's no more left so the sparking stops.

It looks like the runway is wet and possibly dirt from the surrounding area has made onto the runway prior to a possible storm and downpour.



C152 G115 TB10 CAP10 SR-22 Be76 PA-34 NDN-1T C500 A330-300 A340-300 -600 B747-200F -200SF -400 -400F -400BCF -400ERF -8F
User currently offlineDougloid From , joined Dec 1969, posts, RR:
Reply 2, posted (7 years 11 months 1 day 21 hours ago) and read 3552 times:

Titanium makes some interesting sparkage. When I was working on MD11 high power ground runs the P&W engines would get a pretty good fan stall with a crosswind and then you'd see stuff like this although not as sustained.
Another possibility could be static electricity??


User currently offlineMX757 From United States of America, joined Aug 2005, 628 posts, RR: 12
Reply 3, posted (7 years 11 months 1 day 20 hours ago) and read 3547 times:

Definitely abnormal.

Looks like the engine ingested debris from the runway. It appears the FOD was bouncing around in the fan duct until the engine went back to normal forward thrust and then the debris was probably ejected out the back.

I hope your friend informed the crew about what he recorded.

Welcome to A.net BTW.



Is it broke...? Yeah I'll fix it.
User currently offlineMX757 From United States of America, joined Aug 2005, 628 posts, RR: 12
Reply 4, posted (7 years 11 months 1 day 20 hours ago) and read 3542 times:

Quoting Dougloid (Reply 2):
Titanium makes some interesting sparkage. When I was working on MD11 high power ground runs the P&W engines would get a pretty good fan stall with a crosswind and then you'd see stuff like this although not as sustained.

I too have been on several high power runs on different types of engines. But I have never seen anything like that.

Quoting Dougloid (Reply 2):
Another possibility could be static electricity??

That is a possibilty. But then I would have to say the engine has some serious bonding issues.



Is it broke...? Yeah I'll fix it.
User currently offlineAirfoilsguy From , joined Dec 1969, posts, RR:
Reply 5, posted (7 years 11 months 1 day 19 hours ago) and read 3500 times:

Quoting CCA (Reply 1):
It looks like the runway is wet and possibly dirt from the surrounding area has made onto the runway prior to a possible storm and downpour

Then blown forward by the reversers and sucked into the intake. I heard this happens when you apply reverse thrust below a certain speed. I.E that once the plane is going slow enough that the debris that are blown up by the thrust reversers catches up to and passes the front of the engine.


User currently offlineAogdesk From United States of America, joined Jun 2004, 935 posts, RR: 3
Reply 6, posted (7 years 11 months 1 day 18 hours ago) and read 3476 times:

Sand& grit being sucked into the intake will cause that, seen it many times.

User currently offlineXFSUgimpLB41X From United States of America, joined Aug 2000, 4224 posts, RR: 37
Reply 7, posted (7 years 11 months 1 day 17 hours ago) and read 3449 times:

Could that be St. Elmos?


Chicks dig winglets.
User currently offlineAirfoilsguy From , joined Dec 1969, posts, RR:
Reply 8, posted (7 years 11 months 1 day 17 hours ago) and read 3436 times:

No that would be this.


View Large View Medium
Click here for bigger photo!

Photo © Ander Aguirre - AirTeamImages



User currently offlineFr8Mech From United States of America, joined Sep 2005, 5603 posts, RR: 15
Reply 9, posted (7 years 11 months 1 day 17 hours ago) and read 3427 times:

I guess I'm going to disagree with the concensus here. That is normal for the proper atmospheric conditions. I've seen it many times while standing ground during runs in reverse where power is applied (contrary to some AMM's).

The sparks appear behind the fan. I'm guessing that they are generated by the friction as the air rapidily chages direction due to the physical obstruction (blocker door).

What were the weather conditions? I've only seen this during low humidity conditions.

Quoting Tweety (Thread starter):
PW2040 engine (#2?),

That would be the left engine on a B757.



When seconds count...the police are minutes away.
User currently offlineGkyip From United Kingdom, joined Apr 2006, 163 posts, RR: 0
Reply 10, posted (7 years 11 months 1 day 15 hours ago) and read 3380 times:

Quoting Dougloid (Reply 2):
Titanium makes some interesting sparkage.

Indeed, Ti can be sparked very easily. I keep sweeping my Ti driver at the driving range on those plastic(?) mats and seeing sparks fly from my driver. Quite alarming!

Gary



The strength of the turbulence is directly proportional to the temperature of your coffee
User currently offlineFr8Mech From United States of America, joined Sep 2005, 5603 posts, RR: 15
Reply 11, posted (7 years 11 months 1 day 14 hours ago) and read 3377 times:

Quoting Dougloid (Reply 2):
Titanium makes some interesting sparkage

I missed that earlier. The PW2000 fan blades are not made of titanium. So it's not titanium sparking.



When seconds count...the police are minutes away.
User currently offlineRyDawg82 From United States of America, joined Sep 2001, 868 posts, RR: 8
Reply 12, posted (7 years 11 months 1 day 14 hours ago) and read 3344 times:

Hey there,

Thank you for posting this video. I had asked about this back in Sept 2006 as well, but without a video to back it up. I too noticed this on several NW flights. Also I have had several friends ask me about this after flying on NW 757s.

Thanks again, and I look forward to the explanations.

Old Topic: http://www.airliners.net/discussions/tech_ops/read.main/167211

Ryan



You can take the pup out of Alaska, but you can't take the Alaska out of the pup.
User currently offlineN231YE From , joined Dec 1969, posts, RR:
Reply 13, posted (7 years 11 months 1 day 13 hours ago) and read 3332 times:

Quoting Tweety (Thread starter):

Nice video.

Quoting RyDawg82 (Reply 12):

I thought someone had asked this a few months ago.


User currently offlineMarkC From United States of America, joined Apr 2006, 259 posts, RR: 0
Reply 14, posted (7 years 11 months 1 day 12 hours ago) and read 3317 times:

The fan blades are certainly made of titanium. 6Al, 4V at a guess, but if anyone really wants to know the exact alloy, ask me tomorrow.

The fan rubstrips are made of a Kevlar impregnated resin...fairly tough stuff. My guess is that its light contact between the tips and the rubstrips under reverse operation.


User currently offlineTweety From Bulgaria, joined Aug 2009, 0 posts, RR: 0
Reply 15, posted (7 years 11 months 1 day 12 hours ago) and read 3308 times:

Quoting MX757 (Reply 3):
I hope your friend informed the crew about what he recorded.

You bet! He told a flight attendant; the FA told the flight crew at an appropriate time. Then while passengers were getting off the plane, the FA said the flight crew asked to meet with him so he went to the cockpit and showed them the video.

The captain then thanked him for bringing it to their attention and said they would write it up for maintenance personnel to look at.

Quoting MX757 (Reply 3):
Welcome to A.net BTW.

Thanks!! Looks like a very nice place. I've enjoyed the photo section for years and finally made the crossover into the forums.

Not directly related to above quotes, but wanted to say thanks to everybody for commenting. It's been interesting.

Hmm, weather conditions at MSP... it was on NW Flight 168 on December 31, and I think that was a 5:50p-11p flight, and was home 45 mins later. Let's see...

KMSP 312147Z 32013KT 3/4SM R30L/6000VP6000FT -SN BR OVC008 00/M01 A2963
KMSP 312222Z 33013G22KT 1/2SM R30L/4000V4500FT SN FG BKN006 OVC013 A2963 RMK AO2 TWR VIS 1 P0002
KMSP 312333Z 33012KT 1SM R30L/P6000FT -SN BR BKN008 OVC013 M01/M01 A2962

Lots of precipitation (mostly snow??), which would probably explain why it looked wet. He did mention something about the snow briefly (unrelated to the flight) but I wasn't paying much attention.


User currently offlineTweety From Bulgaria, joined Aug 2009, 0 posts, RR: 0
Reply 16, posted (7 years 11 months 1 day 7 hours ago) and read 3227 times:

I'd like to apologize for having had posted this without having the good sense to allow my friend to have the opportunity to post about it, or to mention I had posted the query here.

Thus, he then had the same good sense to post a query about the same event here (not realizing I had done so earlier). It's my fault for not communicating, and my fault for resulting in duplicate threads.

I'm really sorry, and I will defer to whatever the moderators wishes. In the future, I promise to communicate better and be more considerate of other people.

In case you'd like to read his better-crafted query:

Video - FOD Ingestion - Night Landing On NW 753 (by Western727 Jan 3 2007 in Tech Ops)

I think he was the one whom originally mentioned a.net years ago, and knows even more about commercial aviation than I do. Again, my apologies.


User currently offlineFr8mech From United States of America, joined Sep 2005, 5603 posts, RR: 15
Reply 17, posted (7 years 11 months 1 day 6 hours ago) and read 3195 times:

Quoting MarkC (Reply 14):
The fan blades are certainly made of titanium.

My bad. I just checked the AMM and they are made of titanium. Don't know where my mid was.

Again, I think this is a normal event based on previous experience. I can't explain the phenomeon, but I've seen it enough on static runs.



When seconds count...the police are minutes away.
User currently offlineAirfoilsguy From , joined Dec 1969, posts, RR:
Reply 18, posted (7 years 11 months 1 day ago) and read 3155 times:

Quoting MarkC (Reply 14):
The fan blades are certainly made of titanium. 6Al, 4V at a guess, but if anyone really wants to know the exact alloy, ask me tomorrow.

Titanium, nickel, molybdenum, carbon, jethete, chromium, ceramic and many others in various combinations depending on there location in the engine.  spin 


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