Sponsor Message:
Civil Aviation Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
Hush Kits-What Do They Consist Of?  
User currently offlineTWA717_200 From , joined Dec 1969, posts, RR:
Posted (13 years 10 months 1 day 16 hours ago) and read 1423 times:

And how do they effect engine performance?

4 replies: All unread, jump to last
 
User currently offlineTWA717_200 From , joined Dec 1969, posts, RR:
Reply 1, posted (13 years 10 months 1 day 15 hours ago) and read 1405 times:

Anyone?

User currently offlineExPratt From United States of America, joined Mar 2000, 311 posts, RR: 0
Reply 2, posted (13 years 10 months 1 day 4 hours ago) and read 1380 times:

JT8D hush kits consist of a mixer, inlet guide vane spacer case, No. 1 disk and hub, accoustic treatment of the fan ducts, and tubes.

The mixer is installed just behind the turbine exhaust case. The mixer breaks up the core engine flow and mixes it with the fan flow. The high velocity core engine exhaust flow is the primary component of jet noise.

The inlet guide vane (IGV) spacer case moves the IGV case about 4 inches forward. This moves the wakes of the air going through the IGVs forward of the fan blades. The fan blades cutting through those wakes is another major component of jet noise.

The new No. 1 disk and hub has a longer nose piece for the No. 1 bearing journal to account for the IGV spacer case and the repositioned No. 1 bearing support.

The fan ducts have panels on the interior surfaces that have holes drilled in them. The holes are intended to absorb specfic sound frequencies of the compressor and combustor noise.

The tubes are the oil and antiice tubes that had to be replaced because of the respaced inlet case.

Because the 727, 737, and DC9 airplanes were certificated engines that generated specific levels of thrust, the hush kits could not and did not effect engine performance.






User currently offlineJETPILOT From United States of America, joined May 1999, 3130 posts, RR: 29
Reply 3, posted (13 years 10 months 21 hours ago) and read 1340 times:

That was a very informative post.

But it's only a piece of the pie.

Some hushkits go about the same business in a different way.

Raisbeck modifies flap settings, derates the engines, and modifies the cascade reversers to achieve the same effect.

Raisbeck covers a portion of the reverser cascades with sheetmatal to reduce noise during reverse operations. The trade off is a much reduced braking.

Raisbeck modifies the flap settings and limits the 727 to a flap 25 landing configuration requiring less power on approach but higher airspeeds. This extends the landing roll.

Raisbeck derates the engines and lowers the aircrafts MGTOW utilizing a lower EPR setting for TO. The efffect is a much lower usefull load, and less than stellar climb performance.

Raisbeck also offers an external exhaust gas mixer (cookie cutter). This increases drag and fuel burn.

So hush kits come in different forms. There is the right way, and then there is the Raisbeck way. But the Raisbeck is considerably cheaper. It is a good modification for planes with little useful life left.

JET


User currently offlineTWA717_200 From , joined Dec 1969, posts, RR:
Reply 4, posted (13 years 10 months 15 hours ago) and read 1303 times:

Thanks for the info, all.

Top Of Page
Forum Index

This topic is archived and can not be replied to any more.

Printer friendly format

Similar topics:More similar topics...
Fly Baboo, What Do You Think Of The Name? posted Sat Nov 11 2006 00:50:21 by Dambuster
What Do You Make Of This Landing? (Video) posted Mon Oct 16 2006 02:00:01 by BMIbaby733
Y, K, M, F, Etc, Class What Do They Mean? posted Thu Sep 28 2006 13:56:25 by Falstaff
Boarding Pass Check - What Do They Look For? posted Fri Aug 25 2006 08:21:30 by Aviationwiz
What Do You Think Of Varig Situation? posted Mon Jun 26 2006 19:45:38 by Thering
What Do You Expect Of A Good Gate Agent? posted Wed May 17 2006 04:05:19 by DLAgent
What Do You Think Of BBI? posted Fri Apr 28 2006 19:43:35 by TommyBP251b
What Do You Think Of The A350 Ads? posted Thu Oct 13 2005 02:56:39 by MarshalN
What Do You Think Of Biometric Security? posted Wed Jun 1 2005 20:36:53 by RootsAir
What Do You Thinkg Of Independence Air Commercials posted Sat Sep 11 2004 22:08:35 by Nycfuturepilot