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planelover
Topic Author
Posts: 313
Joined: Sat Dec 22, 2001 1:22 pm

Ram Air Turbine:

Sun Jan 06, 2002 8:00 am

Hey all,
On a movie I was watching the other day (Falling from the Sky), a commercial jet ran out of fuel while in flight, thus having no way of powering the flight deck or hydraulics (sp?). After several seconds, a "ram air turbine" came down from the belly and used the on-coming air to power a small generator that produced enough energy to run the flight deck and hydraulics. I'm not sure what kind of plane it was. It looked like a 777 on the inside, but looked like a 767-200 on the outside (you know how Hollywood is). Anyways, is there such a thing as a "ram air turbine"? By the way, the pilots managed to glide the plane in for a landing.
Thought I'd ask. Thanks.  Smile/happy/getting dizzy
 
Av8trxx
Posts: 633
Joined: Sun Nov 11, 2001 7:08 am

RE: Ram Air Turbine:

Sun Jan 06, 2002 8:13 am

It was an Air Canada 767, known as the "Gimli Glider". Luckly, the Captain was an avid glider pilot, which I am sure helped!

The RAT is used in emergency situations to generate sufficient power to keep an aircraft flying long enough to land. A RAT basically performs the same function as an auxiliary power unit (APU) in a pinch. But while an APU is essentially a small jet engine that burns regular jet fuel to generate this additional power, the RAT consists of a propeller that is spun by the high-speed air flowing past the aircraft. The spinning propeller powers a turbine that provides the emergency electricity needed to keep critical systems running, such as hydraulics, flight controls, and key avionics. In normal flight, the entire assembly is folded up and stored in the aircraft fuselage or wing.

I think the CRJ has one, as well as the A330.
 
TommyS
Posts: 18
Joined: Tue Oct 30, 2001 10:52 pm

RE: Ram Air Turbine:

Sun Jan 06, 2002 8:56 am

Here is a shot by a friend of mine:



Click for large version
Click here for full size photo!

Photo © Gregg Stansbery



This is on an RJ but should answer your question.
 
ewr757
Posts: 356
Joined: Mon Apr 03, 2000 8:47 am

RE: AV8trxx

Sun Jan 06, 2002 11:20 am


The RAT has nothing to do with any electrical function or power supply on the B767.

It strictly powers the Center Hydraulic system components (flight controls) with a loss of both engines.

It does not in any way shape or form mimic an APU or it's functions (electrical and pneumatic).
 
planelover
Topic Author
Posts: 313
Joined: Sat Dec 22, 2001 1:22 pm

RE: Ram Air Turbine:

Sun Jan 06, 2002 1:27 pm

Thanks guys. Do most planes have a RAT? Or is it just the CRJ, 767, and A330? Does a plane's engines provide electrical power for an aircraft or does it use the APU during the whole flight? If it does use the engines for electrical power and both engines and APU stop working, would the engines windmailing in the wind produce enough rotation to provide electrical power for the aircraft? Thought I'd ask. Thanks you all.
 
Trent_800
Posts: 136
Joined: Thu Jan 03, 2002 11:29 pm

RE: Ram Air Turbine:

Sun Jan 06, 2002 7:33 pm

I remember reading somewhere of a 747-2 or 300 that flew into a cloud of volcanic ash and lost all 4 engines i think he used the windmilling effect of the engines to provide power. he desended to aboyt 12,000ft before managing to start engines 1,2 and 3 but 3 was producing a high vibration so he just landed with 1 and 2
 
ewr757
Posts: 356
Joined: Mon Apr 03, 2000 8:47 am

RE: Ram Air Turbine:

Sun Jan 06, 2002 9:25 pm


Windmilling engines provide no power (thrust) and little if any residual rpm to supply rotation for the Hydraulic pumps to operate at a designed pressure output. They also do not turn fast enough to allow the IDG/CSD to allow the electrical generators to come online.

With a high enough airspeed (chart for different altitudes), they will rotate fast enough for a relight to restart without an outside (i.e. APU) pneumatic source.

I think the airplane you mentioned was a China Air 747.
All 4 engines needed to be changed with extensive repairs to other parts of the airplane (pneumatic and pressurization system)
 
vc10
Posts: 1436
Joined: Thu Nov 15, 2001 4:13 am

RE: Ram Air Turbine:

Sun Jan 06, 2002 10:32 pm

The Concorde has a Ram Air turbine on it,s port side. When it is deployed it,s little prop willl power the hydraulic system so that the flying controls, which are hyd powered, can still be used. As the aircraft slows for landing the hyd output reduces, so if it is using just the RAT for hyds then I seem to remember it's recomended landing speed was very high [190/200kts over the fence]. This allowed it to produce enough hyd pressure to the flying controls for the flare to take place.
Also the old VC-10 had a RAM air turbine again powering the hyds [ Or was it electrics memory failure due to age]
Anyway the VC-10 was designed back in the early 1960's which only proves there is very little that is new in aviation.
Little vc10
 
cdfmxtech
Posts: 1319
Joined: Wed Jul 05, 2000 11:37 am

RE: Ram Air Turbine:

Sun Jan 06, 2002 11:48 pm

B757/B767 and the B777 all have RATS. I belive the DC10 has a RAT, but u can select whether or not it is used for Electrics or hydraulics.
Can anybody confirm??

Cdf
 
FDXmech
Posts: 3219
Joined: Sun Mar 19, 2000 9:48 pm

RE: Ram Air Turbine:

Mon Jan 07, 2002 1:59 am

Hi Cdfmxtech,

Yes you're correct. The DC10 has an ADG (air driven generator) which when deployed, the pilot has the option of powering one aux pump (electric motor driven hydraulic pump) or powering the right emergency bus system. Similar system installed in the MD11 but much more versatile in function.
You're only as good as your last departure.
 
FDXmech
Posts: 3219
Joined: Sun Mar 19, 2000 9:48 pm

RE: Ram Air Turbine:

Mon Jan 07, 2002 2:00 am

Hi Cdfmxtech,

Yes you're correct. The DC10 has an ADG (air driven generator) which when deployed, the pilot has the option of powering one aux pump (electric motor driven hydraulic pump) or powering the right emergency bus system. Similar system installed in the MD11 but much more versatile in function.
You're only as good as your last departure.
 
delta-flyer
Posts: 2635
Joined: Mon Jul 30, 2001 9:47 am

RE: Ram Air Turbine:

Mon Jan 07, 2002 7:45 am

The A320 also has a RAT.

Some RAT's have both hydraulic pumps and electric generators, while the CRJ just has a generator no hydraulics. Hydraulic power in the CRJ (when both engines are out) is obtained by running an AC motorpump off the power produced the the RAT generator.

Allied Signal (now Honeywell) and Sundstrand manufacture RAT's. Here is a link for the Sundstrand RAT's .....

http://ww3.hamiltonsundstrandcorp.com/aerospace/products/ram_air_turbine.htm

Cheers
Pete
"In God we trust, everyone else bring data"
 
Av8trxx
Posts: 633
Joined: Sun Nov 11, 2001 7:08 am

EWR757

Mon Jan 07, 2002 9:36 am

The description I posted of a RAT was for general explaination purposes only, and was not specific to the 767, although it may have appeared to be. I referenced an explaination provided by Aerospaceweb.org on their aircraft FAQs section in writing my post.

I only mentioned the Air Canada 767 because Planelover was wondering what model was actually involved in the incident.

Planelover- if you are interested, here's a site devoted to the
Gimli Glider
 
NZ767
Posts: 1553
Joined: Sun Nov 18, 2001 9:17 am

RE: Ram Air Turbine:

Mon Jan 07, 2002 10:20 am

The aircraft that flew into volcanic ash and lost all four engines was a British Airways 747 enroute LHR-BOM-PER-AKL under the command of Captain Bob Moody.

This occured in 1982 while flying in the vicinity of Mt Galungung south of Jakarta,Indonesia.

There were no prior warnings given to the crew regarding an eruption in this area so when it happened, they had no idea what was going on as it was night time and the ash cloud did not show up on the weather radar due to the fact that it contained no moisture and therefore produced no radar return.

All four engines stopped; the a/c glided to a lower level where they were eventually restarted.
The flight limped back to Jakarta where they made an emergency landing without ILS.

The RAT was not used in this incident.

Mike  Smile
 
FDXmech
Posts: 3219
Joined: Sun Mar 19, 2000 9:48 pm

RE: Ram Air Turbine:

Mon Jan 07, 2002 11:16 am

I read an account of the BA 747 losing all four engines flying into a volcanic plume.

Normally when an engine experiences a shutdown or in fact is shut down, the generator will trip off by virtue of a CSD (constant speed drive) underspeed switch.

Basically this underspeed switch will trip its respective generator as the engine spools down (normal) before it would trip due to a low voltage condition caused by a too slow a rotating generator.

From what I read, one of the generators remained on line because its underspeed switch malfunctioned and did not trip the generator when the engine flamed out and was windmilling. The gen. was putting out some very low voltage but just enough to remain on line.

The 747 is not equipped with a RAT.
You're only as good as your last departure.
 
ewr757
Posts: 356
Joined: Mon Apr 03, 2000 8:47 am

RE: Av8trx

Mon Jan 07, 2002 11:26 am



Yes it did seem that way. No harm no foul. Just wondered if I missed something in ground school
 
rmm
Posts: 518
Joined: Sun Feb 04, 2001 10:34 am

RE: Ram Air Turbine:

Mon Jan 07, 2002 11:46 am

I'll have to check my books on this one but I think the
RAT can provide electrical power on "certain" 767's.

Some models have a hydraulic driven generator in the
L/H w/w. From memory it runs off the centre system.

Rmm
 
TimT
Posts: 168
Joined: Sun Jun 03, 2001 1:38 pm

RE: Ram Air Turbine:

Mon Jan 07, 2002 1:35 pm

The A-319/320 also has a RAT. Left side just aft of MLG door. Runs hydraulic system. If you don't shut the a/c down in the correct sequence ( "hit the button Max!") it drops and you have to restore electric & hydraulic power to stow it. (Please don't ask me how I know)  Wink/being sarcastic
 
747Teach
Posts: 176
Joined: Wed Nov 29, 2000 3:05 am

RE: Ram Air Turbine:

Mon Jan 07, 2002 10:39 pm

Planelover: The Lockheed L-1011 has a Ram Air Turbine (RAT) in the center of the belly just forward of the hydraulic service bay fwd door. The RAT is connected to the "B" hydraulic system, and will produce 2850 psi at 15 gpm. The 2 bladed prop is about 30" in diameter and spins about 5800 rpm. It is automatically deployed by a spring cartridge if all engines are out or all pumps are off, and the aircraft is in the air mode and over 100 kts. The RAT may be manually deployed in the air by lifting the guard and pressing the switch labeled Ram Air Turbine on the Flight Engineers hydraulic control panel, just above the "B" system pressure gauge. To restow the RAT, the aircraft must be on the ground, the flaps set between 4 and 30 degrees, and the No. 2 engine running above 85%. Then operate the test switch on the hydraulic service panel to reset, and observe the lock engaged light illuminates. Stay clear of the RAT doors, especially if the ground safety bar is not installed. The ground safety bar is stowed inside the hydraulic bay fwd service door.
Operation of the RAT should give you at least one operable hydraulic channel to all major flight controls, and normal brakes. By turning on the B-A PTU, you can then power up the "A" system hydraulics, which gets you normal flight controls and tailskid. My information comes from the L-1011 systems handbook, pages 29-113 through 120. Regards,
 
Staffan
Posts: 3879
Joined: Tue Mar 18, 2008 9:21 am

RE: Ram Air Turbine:

Tue Jan 08, 2002 6:05 am

Wasn't that BA 747 on a flight between KUL and PER when it hit the volcanic ash??

 
NZ767
Posts: 1553
Joined: Sun Nov 18, 2001 9:17 am

RE: Ram Air Turbine:

Tue Jan 08, 2002 10:18 am

Nup!!
It was BOM-PER.
BA10 I think it was!!

Everyone aboard this flight were made members of the "Gallungung Gliding Club"; formed so that they could all keep in touch.

Mike  Smile
 
Staffan
Posts: 3879
Joined: Tue Mar 18, 2008 9:21 am

RE: Ram Air Turbine:

Tue Jan 08, 2002 11:06 am

This is strange...
I have a book about the 747 and the author tells the whole story about this incident, the facts given...

June 24th 1982, Cpt. Eric Moody
B747-236B, G-BDHX City of Edinburgh, Speedbird 9.
It says the flight was KUL-PER (which to me makes more sense than BOM since a flight from KUL would pass over Jakarta and the one from BOM would be mostly over the sea)

*scratches head*... hmm...

Don't know what is right or wrong...  Smile

Regards,

Staffan
 
NZ767
Posts: 1553
Joined: Sun Nov 18, 2001 9:17 am

RE: Ram Air Turbine:

Tue Jan 08, 2002 3:40 pm

Hey Staffan,

That's a point!!
Sounds like the book I've read (twice  Smile)
If so, remember at the start when they said that the flight is "almost always full" on the LHR-BOM leg as it was the quickest way for Indian nationals to get home; or something to that effect?

I remember BA used to have the only same-plane service between New Zealand and India.

Hell I dunno, maybe it was LHR-BOM-KUL-PER-AKL??
If I'm wrong, then SORRY Embarrassment.

I'm scratching my head too.......I'll have to dig the book out when I get home.

Mike (WLG)



 
411A
Posts: 1788
Joined: Mon Nov 12, 2001 10:34 am

RE: Ram Air Turbine:

Tue Jan 08, 2002 4:14 pm

Right on all accounts, 747Teach and, it is recommended to maintain at least 160 knots of final to assure proper RAT rpm. But, beware of icing.
Also, if it were me, I would not use the BtoA PTU (on final) as the B system provides all the control you would need.
During landing, the RAT will not provide enough hyduaulic pressure for normal brakes, but the brake accumulator has plenty of capacity....beware no nosewheel steering will be available.
 
cdfmxtech
Posts: 1319
Joined: Wed Jul 05, 2000 11:37 am

RMM....Read

Sat Jan 12, 2002 12:10 am

The B767s (along w/the B757) have an HMG (Hydraulic Motor Generator). That uses hydraulic power to power a motor which supplies power to some electrics (forget exactly which...but it's stby stuff). Has nothing to do with the RAT. RAT is for flight controls only in the B767.

Unless u know something i don't about some kind ogf options for some companies...but i belive that's what you're referring to.

cdfmxtech
 
delta-flyer
Posts: 2635
Joined: Mon Jul 30, 2001 9:47 am

RE: Ram Air Turbine:

Sun Jan 13, 2002 12:22 pm

Cdfmxtech.... Does the HMG operate when only the RAT is providing the hydraulic power, or is it just a back-up for the main generators during powered flight? We make the HMG for the 757/767 and also the RAT pump on the 777, among others. Unfortunately, our customers sometimes do not divulge their system architecture to us.

Thanks,
Pete
"In God we trust, everyone else bring data"
 
flysab
Posts: 102
Joined: Fri Nov 05, 1999 7:59 am

RE: Ram Air Turbine:

Thu Jan 17, 2002 10:56 pm

Airbus 330 and 340 also have a RAT.
It is located in the aft part of one of the flap track fairings on the right hand wing.
When deployed, it will pressurize the green hydraulic system, which in turn will drive an electric generator.
Thus both hydraulic and electric power will be partially restored.
 
sudden
Posts: 3936
Joined: Fri Jul 13, 2001 5:20 pm

RE: Ram Air Turbine:

Fri Jan 18, 2002 12:08 am

EWR757.........

I'm not questioning your knowledge, but the movie *FREEFALL* as the name is, is based on a true story. I'v seen it.
When the turbine was deployed, it also powerd some electrical components in the cockpit.
Was this just fictive?
Just curious.

Regards!
When in doubt, flat out!
 
TechRep
Posts: 1877
Joined: Sun Jan 13, 2002 6:53 am

RE: Ram Air Turbine:

Fri Jan 18, 2002 12:26 am

In my experience there are two types of RAT's. One supply's emergency electrical power only and the other type that provides both electrical and hydraulic power. I can recall during heavy checks on A300's there was a specific ops check of the system, The RAT had to deploy and retract in a certain time frame, I think it was 20 seconds. If my memory serve's me correctly it was an emergency electrical power only RAT on the A300-B4. Everyone always seems very interested in this system for some reason I don’t know why, technicians and inspectors would gather around to watch it go down then back up. Other than looking like a cool outboard motor it has no interest to me.

TechRep
 
sudden
Posts: 3936
Joined: Fri Jul 13, 2001 5:20 pm

RE: Ram Air Turbine:

Fri Jan 18, 2002 12:29 am

It is a funny "gadget" I must admit.  Smile
When in doubt, flat out!

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