The Sound of Muscle

I was east of Seattle today in in Clearview when I heard what sounded like a C180 in a power dive, prop screaming. I looked frantically to see it but all I could see was a 777-300 in the distance. Then I realized that the sound was attached to the 777 and for a minute I thought that an engine had a failure. No smoke , no vapors, but the sound locked on to the airplane as it passed and I realized that they had deployed the RAT. That thing is loud! They have been testing several airplanes around greater Seattle during this wonderful summer weather, 777, 787, and 747's. Nice to live here.

 

Bob- RATs are handy things to have. A few of my friends could have used one, but no dice.

 

Sounds like a wood-chipper in the sky..

[ame=http://www.youtube.com/watch?v=FfB2EP71hqY]Boeing 777 Ram Air Turbine (RAT) function test - YouTube[/ame]


Look between Engine 2 and the Fuselage...
[ame]http://www.youtube.com/watch?v=2BAqp7oh6Wg[/ame]

 

What's turning the impeller in the test video? They must have a really powerful blast of air directed at it...

 

The video description lays it all out. To test the RAT, it spins on hydraulic feed.

 

Taz, i was correct in my assumption. i checked with the gang at work and it was a pre-delivery flight of a 787 that was on an extended base leg to Paine. At 180MPH that prop really sounds off.

 

Bob- They do sound like hundreds of African bees stuck inside your helmet, or an air raid siren. Nice to have flight controls and limited bus power. When our engines quit, it was the old 30,000 lbst rocket departure.

 

That must have been a thrill but hard on the back.

 

Bob- Affirmative, everybody who jumped out ended up shorter. About 10 g on departure and quite a bit more on landing, unless it was in the water.

 

Taz, would you translate, please? I have zero idea what you're talking aobut...

"When our engines quit, it was the old 30,000 lbst rocket departure."


and


"everybody who jumped out ended up shorter. About 10 g on departure and quite a bit more on landing, unless it was in the water."

 

F-111 had a capsule ejection system that weighed about 3000 lbs. Solid rocket motor for the capsule had 30,000 lbst, so 10 g acceleration at max thrust. There were impact attenuation bags on the bottom of the capsule, but landings felt like being strapped into a straight legged chair and being dropped out of a second story window. Spinal compression was the normal result and loss of height.

 

Thx... didn't know you were an Aardvark guy.

 

The crew of the "Gimli glider" was sure happy to have a RAT!

 

I would be willing to bet that the effects of those spinal impacts will surface again in later years. At 87 I can attest to the reappearance of what were " minor injuries" when I was a kid. The body remembers what you did to it and it gets back at you. I have seen the effects on those who saw heavy action in WW2, early aging and more problems as they age.

 

Bob- Plus being deaf as a post from sitting behind a 2000 hp recip or firing artillery rounds. My brother, too, who refused to wear ear plugs under his helmet in F-4s. I always did and stll have relatively good hearing.

 

Wow, that RAT makes quiet a noise.

Here's some pics of the 747-8 RAT....

1: On the EICAS HYD page, you'll see the RAT powers system 3.
2: RAT switch. The lights are in test mode now, that's why it's lit.
3: Bad Overhead pic showing the RAT switch. Again, light test mode. I never realized that the PRESS light on the RAT is GREEN. It's the only green light on the overhead. As Boeing goes for the "dark cockpit" concept, only warnings are shown. So most of the lights on the overhead are AMBER. A few are RED. Those being FIRE warnings. There are a few WHITE lights, but not many.

Typically, we don't use the overhead lights much as the associated warnings are shown on the EICAS display. But they are a good backup.

As the RAT's design on the 747-8 is for "loss of all engines", I guess a GREEN PRESS light is a good idea. With loss of all engines, you lose all generators too. In the 747-400, a RAT isn't required as the engines windmill fast enough to provide hydrallic operation. In the -8, I guess they don't.

At first I thought, why not have the RAT power electrics too. But I guess if you've lost all engines, the batteries should last long enough.

Interesting sidenote, in the 747 classic, there was a "loss of all generators" checklist. In the 400 and -8, there isn't. I was told that Boeing figured the possibility is too remote. Don't know if that's true or not......

Lou
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