DC8FriendShip From United States of America, joined Apr 2005, 204 posts, RR: 3 Reply 1, posted (1 year 3 months 4 weeks 1 day 23 hours ago) and read 1671 times:
What? I don't undrestand. perhaps a photo to help?
Wingscrubber From United Kingdom, joined Sep 2001, 505 posts, RR: 0 Reply 2, posted (1 year 3 months 4 weeks 1 day ago) and read 1508 times:
I think MCIguy is specifically referring to why the rolls royce RB211 and trent cowlings stretch the entire length of the engine whereas other designs do not, for instance, RB 211 vs CFM 56
I would take a wild guess and say that it's because the engineers decided that the fan should have a fully-ducted cowling.. No two engines ever really follow the same design path.
WPIAeroGuy From United States of America, joined Aug 2007, 239 posts, RR: 0 Reply 3, posted (1 year 3 months 4 weeks 23 hours ago) and read 1479 times:
The ducts on the Rollys-Royce and IAE engines is to mix the stream between the fan and core flow, which reduces noise and adds a slight performance increase. In an ideal case, there may be between 1-3% increase in thrust, but that comes at an increase and weight, and thats also assuming a perfect mixer. My guess is that RR and IAE chose the full cowling mostly for noise reduction.
HAWK21M From India, joined Jan 2001, 28091 posts, RR: 60 Reply 4, posted (1 year 3 months 3 weeks 6 days 22 hours ago) and read 1356 times:
Quoting Wingscrubber (Reply 2): I think MCIguy is specifically referring to why the rolls royce RB211 and trent cowlings stretch the entire length of the engine whereas other designs do not, for instance, RB 211 vs CFM 56
The RB211-535C does not,though the RB211-535E4 does.
regds
MEL.
411A From United States of America, joined Nov 2001, 1621 posts, RR: 10 Reply 5, posted (1 year 3 months 3 weeks 6 days 21 hours ago) and read 1347 times:
With the early varients of the RollsRoyce RB.211 series (IE: RB.211-22B and RB.211.524B02) noise reduction was the reason for the extended cowl.
These engines were installed on Lockheed TriStar aircraft, and the L1011 was the only first generation wide-body jet transport to meet stage III, at all weights.
L1011...a superb design.
Years ago, I remember the dB meter installed at the end of one street in Morfeldon, a small town just south of the FRA airport.
The recording device was inside, but a dB meter was visible from the outside.
In talking to local residents one day, they mentioned that when a TriStar departed, the needle on the meter hardly moved.
Yet, when a 747 or DC10 departed, the meter read half scale.
Quiet...a TriStar specialty.
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