Understanding part of an NTSB accident report

MrNomad · #1 10-31-2019, 09:48 PM

A friend of mine was killed in a Cessna 152 two years ago. NTSB WPR18FA035 report is out and I am vexed by the following paragraph. I realize this is not an RV issue but I am trying to understand where "lint" could come from. Thx.

"The carburetor fuel inlet screen was found properly installed. The fuel inlet screen contained a loosely packed material consistent with lint that constituted approximately 50% of the screen internal volume. The material was submitted to the NTSB Materials Laboratory for identification. The material consisted of two different fibrous materials: one blue, and one reddish-brown in color. A spectrometer was used to collect and process infrared wavelength absorbance spectra of the material; the spectral results indicated that the material was most likely cellulose, which is found in natural plant fibers such as cotton. The material was foreign to the airplane fuel system, and it was not determined when or by what means the lint was introduced into the fuel system."

chaskuss · #2 10-31-2019, 10:35 PM

Sounds like a cotton cloth or rag may have been used to clean the inside of one of the fuel tanks or some part of the fuel system previous to the accident. Most likely an edge or some portion of the cloth contacted a rivet or a sharp edge inside and was torn off. That's probably where your lint came from.

Charlie

theduff · #3 10-31-2019, 10:35 PM

I suspect it came from either shop disposable towels or rags. Might have cleaned something in the fuel system and wiped it off with the above.
Sorry for your loss.
Duff

rv8ch · #4 11-01-2019, 01:32 AM

Sorry for your loss Barry. Clearly anything foreign in the fuel system is bad, and that's very important for all of us, but it does not seem to have caused the engine to stop, based on the information in the report.

Discus2b · #5 11-01-2019, 02:14 AM

Very interesting. Tragic. I can see maybe a fueler using a rag or wearing cotton gloves to handle the fuel caps. They become worked and deteriorated, perhaps a piece gets pinched and caught putting the cap back on. Next time the cap is removed the piece falls in and with time breaks down into smaller pieces.
At 65 and 36,000+ hours.....this one really has my attention and I will be rethinking my refueling method. The 152 has a raised refueling port offering some protection from debris falling in, or blown in. Vans is flush. In my hanger I use a small soft carpeted inverted bath mat to protect the wing in front of the port from the nozzle and hose even though I hold both off the wing. Not any more. Seems dumb now.
Thanks for reaching out with your question. It certainly impacted my methods.

R

BillL · #6 11-01-2019, 06:12 AM

Good question, doesn't the 152 have a collection screen in the gascolator?

So in that case it would have been something from service work downstream of the gascolator. Two colors sounds like a process issue with multiple occurrences.

It is a good reminder to check my servo screen at annual.

rv8ch · #7 11-01-2019, 07:14 AM

Quote:

Originally Posted by BillL

Good question, doesn't the 152 have a collection screen in the gascolator? ...

Looks to me like the screens worked - the engine kept running. The accident was not caused by any type of engine failure. The engine was turning at impact, according to the report I read.

crabandy · #8 11-01-2019, 07:31 AM

I Had to pop open my fuel tanks to perform a service bulletin before flying, I cleaned the tanks ?very? well with red shop rags. I found red fibers in my fuel filter screen as well as red fibers causing the quick drain to drip. It took several flushings before I got them all out.

koupster · #9 11-01-2019, 09:35 AM

Part of my A&P school involved two weeks working with an A&P who maintained a fleet for a university flight school. When he tasked me with opening and inspecting a gascolator, he told me that I'd probably only find lint on the screen. It didn't occur to me at the time to ask where the lint might come from, but it was common enough for him to prepare me to look for it.

Cheers, David
RV-6A - A&P

rvbuilder2002 · #10 11-01-2019, 09:52 AM

Quote:

Originally Posted by BillL

Good question, doesn't the 152 have a collection screen in the gascolator?

So in that case it would have been something from service work downstream of the gascolator. Two colors sounds like a process issue with multiple occurrences.

It is a good reminder to check my services screen at annual.

Quote:

Originally Posted by rv8ch

Looks to me like the screens worked - the engine kept running. The accident was not caused by any type of engine failure. The engine was turning at impact, according to the report I read.

I agree, it doesn't sound like the foreign material in the carb screen was a factor in this unfortunate accident.
In fact, my guess would be that it had been there for a long time since there was no indication of the same material in the gascolator screen or pick-up screens in the fuel tanks. Likely because the gascolator screen was probably getting regularly maintained during inspections, like it is supposed to be, but the inlet screen on the carb. was not. Fairly common, unfortunately.

Good reminder for RV owners. Do you know that the carb. or fuel injection servo you have on your airplane has an inspect-able / cleanable inlet screen?