GalaxyFlyer wrote:Jets don’t have carburetors, so they don’t “run rich”.
CoronadoConrad wrote:Hello guys.
I have a question regarding Delta/Northwest 747s. I was wondering why their engines seem to have consistently run a bit richer than other operators? They seemed to be almost like B-52's taking off. I found a few videos to highlight what I am talking about.
Now I know that a few of their aircraft were some of the earliest -400's built, but I have noticed other early operators such as United didn't seem to have aircraft that were this smokey. Here is a couple of 1989/1990 build models operating long haul flights out of Narita as well, so I can't imagine that a derate is the excuse either.
What I am wondering is, was there some sort of combustor upgrade that occured in the PW4000 development cycle that Delta/Northwest never bothered to add to their aircraft? Any information would be appreciated.
strfyr51 wrote:yes there were fuel nozzle upgrades that eliminated the smoke trail. And United did the upgrades in our shops
CoronadoConrad wrote:strfyr51 wrote:yes there were fuel nozzle upgrades that eliminated the smoke trail. And United did the upgrades in our shops
Thanks for that. Do you know more about what specifically was improved in the newer fuel nozzles? Did they further atomise the mixture?
747classic wrote:P&W has certified in 1993 a Phase 3 reduced pressure combuster on the PW4056, as installed at the 747-400 series.
The smoke number was original 18,4 (100,2% of the Original limit)
After this modification the smoke number was reduced to 10,9% (59,4% of the limit.)
See : https://www.easa.europa.eu/easa-and-you ... s-databank
- Select and download : current data sheets
- Select P&W and P&WC
- Select 1PW041 for the original PW4056 emission data (1986)
- Select 1PW055 for the modified PW4056 emission data (1993)
Compare the PW4056 with the engines of other manufacturers installed at the 747-400 :
GE CF6-80C2B1F : Original certified smoke number 8.3%
RR RB-211-524G : Original certified smoke number 5.0%
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