B744 wit RB211s?

[captain cumulonimbus]

Hi guys.

Just a quick one.I'm a pilot and have never yet noticed the fact that the 747-400s with rolls rb211 engines seem to have slight differences in the pylons...there being three engines with 'long' pylons,ie extending forward over the engine further,and one engine with a noticeably shorter forward pylon extension over the engine.Why is this? just different fairings or is there some specific reason?

i know its quite obscure but thanks

[gas path]

Should all be the same ie. the fairings should be all short or all long depending on the a/c line number.

[Rainboe]

Are you thinking of old B707s with Pratt & Whitney engines? It was to do with only having 3 turbocompressors for the pressurisation system.

[captain cumulonimbus]

Thanks! No,i know about the 707s with their turbocompressors,this is just a difference in pylon fairing length...i saw it on an SAA 744 for the first time,had three 'long ' fairings and 1 shorter,stubbier one.Just looked unbalanced.A replacement perhaps?

[gas path]

The longer fairing was introduced as part of drag reduction on the later a/c and we ended up with a mismatch on our fleet due to the different mod states of the nose cowls, (the position of the hook!) until it was pointed out by Mr. Boeing that the a/c had not been flt. tested with an intermix there then followed a 'panic' to get the fleet back to the 'status quo'

[captain cumulonimbus]

Very interesting,thanks! You see how observant i am??

[barit1]

it was pointed out by Mr. Boeing that the a/c had not been flt. tested with an intermix

How did Mr. Boeing's Service Bulletin read? And where was Mr. Boeing's tech rep?