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Zkpilot
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RAT

Sat Apr 15, 2006 8:34 pm

Hi all, sorry if this has been posted somewhere before,
just wondering has anyone here been operating, or been travelling on a flight where the RAT (RAM Air Turbine) has been deployed?  Smile
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A319XFW
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RE: RAT

Sat Apr 15, 2006 9:17 pm

Not been on a flight with the RAT out, but at XFW for the first flights (or on customer flights if they ask so) of new aircraft, they extend them.
You can always tell when an aircraft with a RAT extended is coming in to land - a funny and very loud (compared to the fans) turboprop noise coming from the aircraft!
 
kaddyuk
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RE: RAT

Sat Apr 15, 2006 9:32 pm

If you are ever on an aircraft which requires the RAT to be extended, i'd say you were a very lucky person.

On the A346:
The Ram Air Turbine supplies auxiliary-hydraulic power to the Green hydraulic system when there is a loss of hydraulic power.

The automatic function extends the RAT when the aircraft has a speed of more than 100 kts, is in flight and the N2 speed of all engines 1, 2, 3 and 4 is less than minimum idle, or there is a total loss of normal electrical power and the N2 speed of the engines 1 and 4 is below minimum idle, or there is a Blue and Green hydraulic reservoir low level indication and a engine burst wire is cut, or the aircraft has a speed of more than 100 kts, is in flight and there is a total pressure loss on all engine pumps.

It would have to be a pretty serious incident to have the RAT extend (i.e. Loss of ALL engines or Hydraulic Pumps).

I've seen one extend in the hangar on a test, really comes down with a whack!
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AvionicMech
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RE: RAT

Sat Apr 15, 2006 9:36 pm

Quoting A319XFW (Reply 1):
You can always tell when an aircraft with a RAT extended is coming in to land - a funny and very loud (compared to the fans) turboprop noise coming from the aircraft!

If you think it is loud when it is outside and flying, you should hear the noise it makes when you back drive it in the hangar. It is very very loud!!!
 
A319XFW
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RE: RAT

Sat Apr 15, 2006 10:00 pm

Quoting AvionicMech (Reply 3):
If you think it is loud when it is outside and flying, you should hear the noise it makes when you back drive it in the hangar. It is very very loud!!!

Yes, I know - they do ground checks on them at XFW in the FAL - a nice big cage around them should anything happen Big grin

As for the A320's - the RAT powers the blue hydraulic system.
 
SFOMB67
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RE: RAT

Sun Apr 16, 2006 3:07 am

Been on several 767 test flts out of HMV's, in which the RAT was deployed during routine cks. The deplyment is done near the end of the flt, as once it's down, it stays down. Seems like all the hyd press indicators read "0" - scary! Been quite a few years ago.
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lowrider
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RE: RAT

Sun Apr 16, 2006 7:21 am

I did a MX test flight to check the operation of the ADG (RAT) on the CRJ. A noticable increase in drag and a substatial increase in noise.
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N766UA
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RE: RAT

Sun Apr 16, 2006 8:43 am

Keep in mind most airliners do not have RATs or ADGs. Aircraft like the 737, for example, use windmilling of the engines.
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EMBQA
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RE: RAT

Sun Apr 16, 2006 8:56 am

Quoting N766UA (Reply 7):
Keep in mind most airliners do not have RATs or ADGs

Most commercial aircraft I can think of have RAT's. Boeing, Airbus, Douglas, Canadair CRJ, Embraer 170/190. I have a co-worker that went on some of the EMB-170 test flights with the RAT deployed. He said it was very loud in the cabin. I've also had the chance to be in the hangar while the RAT was being tested and it screams..!! Even with ear protection on, it's loud.

[Edited 2006-04-16 02:02:54]
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AvionicMech
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RE: RAT

Sun Apr 16, 2006 9:25 am

Quoting N766UA (Reply 7):
Aircraft like the 737, for example, use windmilling of the engines.

The reason that the 737 doesn't have a RAT is because the aircraft can be flown without hydraulic pressure unlike most current commercial aircraft.

Most aircraft have hydraulically powered flying controls which means that hydraulic power is needed to move them, whereas the 737 and some older aircraft have hydraulically assisted flying controls which means the hydraulic system just helps to move them.
 
kaddyuk
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RE: RAT

Sun Apr 16, 2006 11:23 am

Quoting AvionicMech (Reply 9):
the 737 and some older aircraft have hydraulically assisted flying controls which means the hydraulic system just helps to move them.

Include all types of B747 under this as well  Smile
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Zkpilot
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RE: RAT

Sun Apr 16, 2006 1:26 pm

Hey thanks, is interesting to know!

Quoting Kaddyuk (Reply 10):
Include all types of B747 under this as well

It does have a RAT also  Smile
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kaddyuk
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RE: RAT

Sun Apr 16, 2006 4:38 pm

Quoting Zkpilot (Reply 11):
It does have a RAT also

Negative, the B747-400 at least does not have a Ram Air Turbine.
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Zkpilot
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RE: RAT

Sun Apr 16, 2006 5:01 pm

Quoting Kaddyuk (Reply 12):
Negative, the B747-400 at least does not have a Ram Air Turbine.

sorry you are correct, it has a quadruple hydraulic systems so that in the event that 1,2 or even 3 don't work the aircraft is still controllable by hand. Having 4 engines of course reduces the need for a RAT also plus the APU can be used for electrical power.
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HAWK21M
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RE: RAT

Sun Apr 16, 2006 8:26 pm

The B757 has a RAT.
If the RAT is deployed on a Scheduled flight.Its something Serious.Considering its the Last option for Hydraulics and/or Electricals depending on the Aircraft.
On the B752.The RAT provides Hydraulics,while the HMG [Hydromechanical Generator] provides Electricals.
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VC-10
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RE: RAT

Sun Apr 16, 2006 9:40 pm

Quoting Kaddyuk (Reply 10):
Quoting AvionicMech (Reply 9):
the 737 and some older aircraft have hydraulically assisted flying controls which means the hydraulic system just helps to move them.

Include all types of B747 under this as well

Wrong. 747 Flight Control are not Hyd assisted
 
AvionicMech
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RE: RAT

Sun Apr 16, 2006 9:57 pm

Quoting HAWK21M (Reply 14):
The B757 has a RAT.
If the RAT is deployed on a Scheduled flight.Its something Serious.Considering its the Last option for Hydraulics and/or Electricals depending on the Aircraft.
On the B752.The RAT provides Hydraulics,while the HMG [Hydromechanical Generator] provides Electricals.

You are not wrong there Mel, if you are on a flight where the RAT has to be deployed start praying to whatever God you pray to.  

The RAT on the 757 if I remember correctly powers the Centre system whereas the HMG is powered by the Right system, so if you were down to the RAT you would also be down to standby power. But the HMG uses so much power that when testing it on the ground you need to run both the Left and Right Electric Pumps with the PTU running as well.

[Edited 2006-04-16 15:03:49]
 
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HAWK21M
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RE: RAT

Sun Apr 16, 2006 10:06 pm


Quoting AvionicMech (Reply 16):
The RAT on the 757 if I remember correctly powers the Centre system whereas the HMG is powered by the Right system. But the HMG uses so much power that when testing it on the ground you need to run both the Left and Right Electric Pumps with the PTU running as well.

True.Amazing set of Backups on the B752.

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[Edited 2006-04-16 15:10:21]
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ReidYYZ
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RE: RAT

Thu Apr 20, 2006 3:53 pm

I remember many moons ago, in the hangar we had this very senior, very experienced certified avionic tech trying to do the backdrive check on a '57. To do the check, you need both ctr system pumps running. I don't recall the elex logic, I think C2 has priority over C1. C1 would start to run, assuming C2 is already running, only after first engine start. To cheat the system, you had to jumper some ground in the Psomethingsomthing panel in the E and E bay. That way you get both pumps and enough volume to do the backdrive. I spent a whole shift lubing the t/e flaps and the whole time watching the tech (a severe tool) stare at the underspeed light. For 8 straight hours, he f*&%$d around with it, and asked NOBODY for any clues. The arrogant prick never did get it right:

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A/c train
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RE: RAT

Thu Apr 20, 2006 7:22 pm

isnt the 757 with HMG only for ETOPS aircraft ?
 
DH106
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RE: RAT

Thu Apr 20, 2006 7:43 pm

Quoting Zkpilot (Reply 13):
sorry you are correct, it has a quadruple hydraulic systems so that in the event that 1,2 or even 3 don't work the aircraft is still controllable by hand. Having 4 engines of course reduces the need for a RAT also plus the APU can be used for electrical power.

There was a tragic Japan Airlines crash back in 1985 I think where all 4 hydraulics systems were lost. The aircraft was rendered very laterally unstable due to losing most of it's fin, but as I recall the pilots had NO mechanical recourse after the hydraulics failures, but managed nonetheless to keep the aircraft aloft for sometime using differential engine power only.
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AvionicMech
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RE: RAT

Thu Apr 20, 2006 8:46 pm

Quoting ReidYYZ (Reply 18):
I remember many moons ago, in the hangar we had this very senior, very experienced certified avionic tech trying to do the backdrive check on a '57. To do the check, you need both ctr system pumps running. I don't recall the elex logic, I think C2 has priority over C1. C1 would start to run, assuming C2 is already running, only after first engine start. To cheat the system, you had to jumper some ground in the Psomethingsomthing panel in the E and E bay. That way you get both pumps and enough volume to do the backdrive.

Yeah I have installed this link a few times but I also can't remember the panel number, but I know it is the right hand panel round the back of the E1 rack. We have a special lead made up that fits in-line with the existing wiring which makes it nice and easy for the not so electrically minded airframe guys to fit it.  

But saying that I have seen an airframe supervisor not know which hydraulic system to turn on to retract the RAT. First he tried it with the CTR pumps still running, then he tried the Left system then finally he turned the Right system on.

Quoting A/c train (Reply 19):
isnt the 757 with HMG only for ETOPS aircraft ?

There are at least 2 different HMG's on the 757, one for ETOPS aircraft and one for non-ETOPS aircraft. The difference between then is the kVA output, the ETOPS aircraft have a higher output, that is on our fleet here at BY.

[Edited 2006-04-20 13:47:01]

[Edited 2006-04-20 13:47:47]
 
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HAWK21M
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RE: RAT

Sun Apr 30, 2006 12:55 am

Quoting A/c train (Reply 19):
isnt the 757 with HMG only for ETOPS aircraft

Not necessary.
Non ETOPS Aircraft can be Equipped with one too.
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MEL
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