GE90 Engine Start

[Lemon Drop]

Will GE ever offer an engine kit to reduce/quiet the awful "moooing cow" sound on the 777-300ER during engine start up?

[8888]

I bloody hope not!!! Love that noise. Menacing, purposeful, unique.

[FlexibleResponse]

The RB211 on the Tri-Star would take a lot of beating on the longest and most mournful start.

[N1 Vibes]

Dear Lemon Drop,

kit available:

Advanced Ultra-High Blocking Ear Plugs-World-Wide Shipping (http://www.earplugsonline.com/)

Best Regards,

N1 Vibes:ok:

[SMOC]

Used on the D4 as a great hot start indicator (if it failed to hmmm).

[Cpt. Underpants]

When recorded and played backwards, the "mooing sound" is Gerry C saying "No Money In Freight, No Money In Freight, No Money In Freight"

[Lemon Drop]

Very funny!!

[Rook]

I like that sound. I like that engine!

[N1 Vibes]

Lemon Drop,

there was a modification to the Trent 800 inlet cowls to reduce the 'buzz-saw' noise on take-off, which was deafening biz class pax in row 15+16, as it exceeded basic H&S noise levels. I think the cost of replacing the inner barrel panels was around US$140k per a/c. Plus the panels were heavier, so we are still paying for them in fuel costs....

But of course, we do it because we love our customers and want to make them as comfortable as possible - fawn, fawn, fawn.

So still believe the earplugs are cheaper for the GE90 moo-cow.

Best Regards,

N1 Vibes

[The Wraith]

Lemon Drop,
If you don't like that sound then you must be either an Airbus pilot or simply as effeminate as your name sounds!!!:}:}:}:}

[F Scaler]

You'll get that same noise on most engines at start if you have low bleed pressure. Boost the pressure - Spin the rotor faster - Noise history

[8888]

F Scaler, not wanting to directly dispute your claim but interested in an elaboration... Surely it's a little more complicated than that, non?

[Mouwaa]

from my experience the moo cow noise seems to always be at low N1 rpm when the initial light off occurs on any turbine engine. On the 777 fuel is automatically sequenced by the EEC, but even on previous jets and turbo props, it seemed to make little or no difference to the low growling noise during initial light off if you let the starter spin faster before introducing fuel. It was usually evident in the cases when you had to let the starter spin to get the ITT/EGT down before whacking the fuel in on a quick turnaround. Though I do remember it used to stop the 'boom' compared to introducing fuel at close to minimum light off N1.

[F Scaler]

8888
To eradicate that specific whine, you must understand what is happening first. Obviously turbines are meant to run at high revolutions - not at starter revs. At light off, you have a mass expulsion of exhaust gas being fed over an 'effectively stationary' high speed turbine. As the turbine is not aerodynamically suited to this slow state, it cavitates/stalls (not the typical compressor stall you know) in sections (that's the whine) until it accelerates and stabilises within its operating envelope.
If you can drive the high speed rotor faster before light-off, no whine is produced. A big engine with only 2 spools needs a massive amount of bleed air demand (high pressure) and hence more robust bleed plumbing and starter. In the interest of commonality and dollars... Question is, do you want to?

[Mr. Bloggs]

If it is not RR, it’s not worth running. Where do I begin?:}:confused: