Injector nozzles: annual cleaning or not?

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photofly
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Injector nozzles: annual cleaning or not?

#1 Post by photofly » Tue Oct 04, 2016 6:04 pm

I noticed Mike Busch recommends against cleaning fuel injector nozzles annually:
The next item that caught my eye was a $200 estimate for cleaning the engine’s fuel injector nozzles. I used to do such prophylactic nozzle cleaning on my own airplane until about 10 years ago, when I had an illuminating discussion with George Braly (of GAMI and Tornado Alley Turbo fame), who is arguably the world’s expert on fuel nozzles. George pointed out to me that there’s no valid reason to do such periodic nozzle cleaning, because the nozzles do not get dirty in service (since they are continuously being cleaned by a very effective solvent). He told me that in his experience with many thousands of GAMIjector nozzles, virtually all clogged nozzle events occurred shortly after maintenance during which the fuel system was opened up and some foreign material got into the system. That resonated with me, because in the first 12 years I owned my Cessna T310R, I experienced two clogged-nozzle episodes, and both occurred right after maintenance due to grease getting into the fuel system. So I stopped cleaning my nozzles 10 years ago, and haven’t had a clogged nozzle since.
http://blog.aopa.org/opinionleaders/201 ... intenance/

What do the knowledgeable people here say?
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GyvAir
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Re: Injector nozzles: annual cleaning or not?

#2 Post by GyvAir » Tue Oct 04, 2016 8:24 pm

I tend to lean towards the “if it's working, leave it alone” side of the argument.

I have seen erratic fuel flow indication fluctuation issues disappear after ultrasonic cleaning of nozzles that looked perfectly clean to the naked eye though.
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Re: Injector nozzles: annual cleaning or not?

#3 Post by crazyaviator » Tue Oct 04, 2016 8:38 pm

I agree ! The sad part is the AME does not like to sign off the insp. sheet and not do the job OR not sign off the insp. sheet and note as non-applicable. Either way, it is an opening to legal exposure after an accident !
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Re: Injector nozzles: annual cleaning or not?

#4 Post by cgzro » Wed Oct 05, 2016 5:41 am

There is certainly a good reason not to be disassembling and reassembling the injectors too frequently as its easy to damage things.

However there are little aerator holes in the body of the injector, not the insert itself that also need to be cleaned and they are not being washed in gas continuously. These you can see as they are externally visible. So what I'd suggest is if the injector bodies look dirty or the aerator holes have anything obvious on them the bodies and inserts should be removed and cleaned.
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Re: Injector nozzles: annual cleaning or not?

#5 Post by robertw » Wed Oct 05, 2016 9:34 am

What does the manufacturer's checklist say? Does it specify that you need to clean the injectors every so many hours? If so, how do you justify not doing it? If the manufacturer's checklist says you need to do it, then there's a reason for it. Not doing it would mean that you'd be pencil whipping that part of the checklist, which isn't a good habit to get into.

As far as my opinion on cleaning injectors, I haven't done it for a while, but if memory serves me correctly, they usually have black carbon deposits on the end of the injector, the build up of which over time can alter the path of the fuel spray, so I don't see where cleaning them would hurt. The comments about foreign objects in the injectors after maintenance do ring true. Any time you open a closed system it increases the risk that something will get in that is not supposed to be there. I don't think that is any reason to argue against doing maintenance to a system though. It's kind of foolish in my opinion. With that kind of thinking, we might as well just not do any maintenance or inspections until the aircraft breaks!

Preventative maintenance / inspections are what you call risk mitigation. There is a risk that preventative maintenance will introduce defects into an aircraft. There is a greater risk though that more severe defects will occur if you don't. :shock:
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Re: Injector nozzles: annual cleaning or not?

#6 Post by photofly » Wed Oct 05, 2016 3:42 pm

With that kind of thinking, we might as well just not do any maintenance or inspections until the aircraft breaks!
It's Mike Busch's oft-stated opinion that this is a much more appropriate approach to maintenance of light aircraft than that which is usually seen in practice, and considerably enhances overall reliability. Read the whole article I linked to.
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Re: Injector nozzles: annual cleaning or not?

#7 Post by DonutHole » Wed Oct 05, 2016 4:40 pm

In Canada...

If contradictory information is found in maintenance manuals of aircraft accessories and aircraft the information in the aircraft manufacturers manual will be used. I'm not sure if its the same in the states.
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Re: Injector nozzles: annual cleaning or not?

#8 Post by C-GKNT » Wed Oct 05, 2016 9:54 pm

A proper engine monitor and a cruise power mag check (ideally lean of peak) will tell you which (if any) injectors needs cleaning. I do this every few flights before beginning my descent.

If an injector needs cleaning it gets done well before the annual therefore no cleaning required during the annual.

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Re: Injector nozzles: annual cleaning or not?

#9 Post by robertw » Fri Oct 07, 2016 8:18 am

photofly wrote:It's Mike Busch's oft-stated opinion that this is a much more appropriate approach to maintenance of light aircraft than that which is usually seen in practice, and considerably enhances overall reliability. Read the whole article I linked to.
Yes, I read it and think it's great. I wish we had more people like Mike flying and fixing. :prayer: Until we do, we'll just have to keep cleaning those injectors as long as they appear on our inspection checklists.
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