View Full Version : RATs and Vixens
27th Dec 2008, 16:20
I was working down at the Solentsky museum today and was asked a question about the RAT (at least I have always been told that is what it is !!!) on our Sea Vixen. Realising I do not know a whole lot about them I had a trawl on the internet and realised that very little information seems to exist and even less photos seem to exist.
I know all about the Gimli Glider and a little of the functionality of the things. But I do have some questions.......
First here is the photo of the RAT on our Sea Vixen, taken today (a nice sunny day today in Southampton....). Probably a nice 'puzzle' pic for those organising a 'what the h*** is that?' quiz.
So...a few questions:
What is the history of the RAT and what was the first aircraft to fit as standard?
Were any ever deployed on Sea Vixens? The books I have read never made mention. Presumably there is some history as it is an early example of RAT use.
There seems to only be a few pictures around of their fitting to commercial aircraft. Where did the (presumed) legislation of their fitting come from?
Can they be retracted once engines have restarted?
Do they ever deploy accidentally?
Anyone have any photos of them extended on commercial planes?
Are they fully automatic on todays passenger aircraft? Can they be deployed manually?Thanks
27th Dec 2008, 17:39
Well here is the general description of the RAT and its operation for the Airbus 320 series:
EMERGENCY GENERATION AFTER LOSS OF ALL MAIN GENERATORS
If both the AC BUS 1 and AC BUS 2 buses are lost and the aircraft speed is above 100 knots, the Ram-Air Turbine (RAT) extends automatically. This powers the blue hydraulic system, which drives the emergency generator by means of a hydraulic motor. This generator supplies the AC ESS BUS, and the DC ESS BUS via the ESS TR.
If the RAT stalls or if the aircraft is on the ground with speed below 100 knots, the emergency generator has nothing to drive it. The emergency generation network transfers automatically to the batteries and static inverter, and the system automatically sheds the AC SHED ESS and DC SHED ESS buses.
When the aircraft is on the ground :
Below 100 knots the DC BAT BUS is automatically connected to the batteries.
Below 50 knots the AC ESS BUS is automatically shed, leading to the loss of all CRTs.
Note : During RAT extension and emergency generator coupling (about 8 seconds), the batteries power the emergency generation network.
The RAT may be extended via the MAN ON P/B on the overhead panel. Once extended it cannot be retracted in flight.
There is much more, but those are the bare bones of it.
27th Dec 2008, 20:26
The following may be of some help as there is a reference to the use of the RAT:-
Sea Vixen. Royal Navy. Carrier Jet. - Sea Vixen Aircrew Testimonies > That of Lt.Cdr.(O) Ed Hughes MIRN. RN. 1962/1991 (http://www.seavixen.org/index.cfm?fa=contentGeneric.yypvawcledkvkehd&pageId=180356)
Incident No 1 – Zone A fire Warning
To return to the story, Ian had also realised the mistake and so because the warning caption remained on continued with the drill for dealing with a Zone A fire which was to shut down the remaining (port) engine. I recall popping the Ram Air Turbine (RAT) at this point to provide emergency power for the flying controls but by this time we were without electrical power and had lost intercom and radio, in fact we were quietly gliding earthwards with no engines. The only good things were that the SWP Zone A caption had gone out and we were still airborne.
28th Dec 2008, 01:49
FYI there are two main types of RAT in use today. The ones that are, effectively, Air Turbine or propellor-driven hydraulic pumps (B-767 is about the largest I know of) which then use that to power a generator or use the pressure directly and also the Air Driven Generators which provide 3-phase AC directly but perversely are mainly used to drive an electric hydraulic pump (for example Canadair Challenger, Global Express & all RJs).
The original Challenger 600 with the Allisons didn't really need an ADG as the ram air flow through the engine provided enough motive power to keep the main generator online until after touchdown - not so with the later GE-powered variants.
British aircraft seem to have been proponents of Emergency Power Units - either mini jet turbines or mono-fuel beasts using Iso Propyl Nitrate (?) which is lethal below the level you'll detect it.
28th Dec 2008, 03:34
I'm real glad I didn't know Iso Propyl nitrate (AVPIN) was lethal otherwise I would have been dead a long time ago.
Its not good for you but I know an awful lot of Guys who have had it all over their hands breathed the fumes and we all still alive. Breathing the fumes after it has burnt is a particularly nasty experience, made me throw up every time. Still not dead tho. Certainly killed a lot more brain cells with the alcohol intake than from AVPIN.
Hydrazine (spelling?) as used on the F16 is extremely nasty. But it was soluable in large quantities of water.
Due to its hazardous nature pilots would allegedly report a leak, ensuring that the aircraft would be parked at a far corner of the airfield with only engineers using breathing apperatus present. While one inspected the aircraft other engineers would unload the contraband ciggies and alchohol etc. Once it was declared free of leaks (and contraband) the aircraft was taxied into dispersal to meet the Customs gent. I of course always refused to get involved in such dastardly activities. :ok:
28th Dec 2008, 14:45
Most BAe or DeHavilland 50s-80s Jets used a multitude of Hydraulics Systems-Yellow,Green,Blue and emergency Red.On the Vixen,you could lose either Yellow or Blue,sometimes.All systems operated between 2650 and 3200 Psi,with Red operating Emergency Brakes ,U/C,Emergency Flaps,Emergency Hook,Rad Scanner,Fuel Filter DeicingPort,Radome,Sceen wiper:Green operated Airbrakes, Normal Brakes,U/C,Hook,Wingfold,Nose Wheel Steering,Fuel Filter Deice Sbd.Blue and Yellow operated the Flying Controls,more or less in duplication.But with a Blue failure,As per the check list-immediate actions were to retract air brake,and extend the RAT.Over land having extended the RAT,one was to rejoin the circiuit above 150 Kts,until gear down and full flap extended.Then one had to keep all control movements to a minimum,and make an extended final approach,reducing to 140 Kts,and fly the A/C on to the runway at 130-140Kts,firmly touching down,without using the Vixen's superb ground effect.If before touchdown Blue pressure went lower than 1600 Psi,another circuit should be made to allow the RAT to build up more pressure,since a late overshoot with low ressure was hazardous!!On the deck,a recovery was only made in good weather by day,if no land diversion airfield was available.Normal Hyd Pressure was a minimum of 2500 Psi.With a Yellow failure,there was a loss of Autopilot and Autostabilizers.When deploying the RAT,it is raised into the airstream with the assistance of a spring-loaded damper strut,and can only be retracted on the ground,and is to be found in a retracted position inside the upper rear fuselage between the jet pipes,as per the photo in the previous listing.I hope this clears up why RATs were an essential part of a Naval Aircrafts emergency equipment.
29th Dec 2008, 13:56
My experience of RATs.
The Hawk has a RAT. Powers B sys Hyd (IIRC) in the case of an engine failure and powews the flying controls only. Electricity comes from the batts. But as you're gliding at this point, they don't have to last too long.
The Victor MK2 had two RATS which were in the aft fuselage and were fed by retractable scoops. The scoops were alwys open for take off and landing and the RATs could be bought on line instantly something went wrong. But they were originally installed to provide electrical power (the flying controls were electrically powered) in case of a 4 engine flame out. Sounds unlikely? Not if you've just dropped a bucket of instant sunshine and the shock wave goes up your jet pipes.
The VC10 was orignally designed with a ELRAT (electrical) and HYRAT (er - hydraullic!) but at some stage in the developement process, it lost the HYRAT. We had to drop the ELRAT in airtests and it was very noisy. A VC10 with a RAT deployed sounded like a turboprop. For a while, we had a problem with the frequency controllers (they were AC and the RPM goverened the frequency and the blade pitch was adjusted to do this) and the RAT was ADD'd to the effect that it was only to be used in emergencies :rolleyes:
The A320 RAT has been described. But there are two ways of deploying it. Either for hydraullics with one button or for electrics with another. Have a hyd problem? Make sure you press the right button, or you've just put yourself in the Emergency Electrical Configuration as well as having the hyd problem. It's been done in the sim more than once!
29th Dec 2008, 15:30
RAT was ADD'd to the effect that it was only to be used in emergencies As it was on at least one occasion when all 4 engines of a VC10 flamed out between Hong Kong and Bangkok, one fine day at the end of 1974, if memory serves correctly.
The BA crew* did a fine job getting 1 relit using the RAT, and then relighting the others. The reason they flamed out in the first place was another matter; BA was rather coy about that, as I recall, something to do with fuel mis-management, running all 4 from one source?
Edit: OK, it was the FE, in the version related by the FE.
2nd Jan 2009, 22:25
Thanks all, really interesting stuff. But has anyone got any RAT photos?
9th Jan 2009, 17:10
I've seen photo's of airliners with RAT's deployed ( on the ground, not in emergencies ) so it's a case of trawling the internet; manufacturers might be the best place to start.
The Harrier 1 series had a RAT, which deployed when the engine was shut down on the flight line - if memory serves, once it had decided there wasn't an emergency after all, it self consciously stowed itself away.
On the mid-life update FA2 serious modifications, the RAT was removed; like the American approach to the Harrier 2 AV-8B ( GR5 etc ) where one was never fitted, as it was regarded as extra weight & complication, and as a Harrier glides like a brick one is more likely to be ejecting than dead-sticking a landing - though it has been done.
The ultimate use of a RAT may well be the airliner ( forget type & airline but it was a BIG twin engine widebody, someone fill in here please ) ran out of fuel way short of destination on a transatlantic flight to the U.S, due to a cock-up translating gallons into lbs.
The thing glided - using the RAT for control surfaces - a hell of a long way, eventually landing safely on an abandoned airfield the Captain happened to know.
It did cause a bit of a stir coming in silently as there was the equivalent of a boot fair being held there !
No-one hurt as far as I know, and the aircrew won awards.
I get the impression most modern fighters don't bother with RAT's, but they seem well worthwhile on transports / airliners, well, anything without an ejection seat !
9th Jan 2009, 17:27
Sounds like you are thinking of a mix of the Air Transat glider ( A330 ) which was over the pond, only ended up just getting to Lajes,
& the Gimli glider ( B767 ) which was got down by Capt Pearson on a field ( I think ) the F.O. remembered, Canada.
That was a metric conversion cockup as I seem to recall.
9th Jan 2009, 20:20
The Gimli Glider.
Gimli Glider - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Gimli_Glider)
9th Jan 2009, 20:39
It was the Lajes glider Captain & F.O. that got airmanship awards, so it's prob more that, that 00 was thinking of.
The fuel shortage though was due to mis-handled maintenance causing a leak within the Engine, & crappy troubleshooting by Capt.Piche & co.
It's also sobering to note that if they had been on their normal routing, they would've been 60miles further north & would've been quite unlikely to make landfall at all. RAT or NO
Hope this isn't thread drift :8
20th Mar 2009, 18:06
While trying to research the fuel starvation incident in a VC10 in 1974 I came across this site....apologies if it's been linked before in the thread.
A Little VC10derness (http://www.vc10.net/)
Lots of VC10 information and pictures there too, in case anyone is interested.
20th Mar 2009, 18:16
Well, I've been and gone and looked at my Sea Vixen Pilots Notes - circa 1969. I had the dubious privelige of flying the Vixen in it's last tour at sea.
The RAT was a hydraulic RAT which powered the blue and yellow hydraulic systems in an emergency. Typically, this would have been a double engine failure or a Zone A fire which required both engines to be shut down.
Blue and yellow hydraulics powered the flight controls. The Rat could be used for shore landings, but only for carrier landings by day in "suitable weather conditions".
Hope that answers your question.
20th Mar 2009, 19:20
Thanks all, really interesting stuff. But has anyone got any RAT photos?
Here's the HYRAT and ELRAT (L to R) on the VC10 prototype. As Dan mentioned the HYRAT was not installed on the production aircraft.
From this page (http://www.vc10.net/Memories/radio_development.html).
If you look here you'll find a photo of a MEA VC10 with the ELRAT deployed (http://www.vc10.net/History/other_operators.html#Middle%20East%20Airways), coming in to land after a test flight (top right).
21st Mar 2009, 11:36
I had the dubious privelige of flying the Vixen in it's last tour at sea.
And what a dashing young man you were, too. When you weren't breaking the cab so that you could claim the last ever launch ;)
21st Mar 2009, 13:38
“… the last ever launch …” at sea I presume.
The RAE Bedford Sea Vixen (XN652) continued to use the ‘HMS Bedford’ Cat facility up to the late 70’s.
IIRC the RAT was deployed during annual air tests; also, but memory fails me, there were some training flights simulating hydraulic failures which resulted in the RAT extending.
My only experience with the RAT for real was after total hyd failure on the ground; but at 75 kt during an accelerate-stop check it wasn’t much use.
22nd Mar 2009, 22:02
On the Hawk and Harrier 1 ( FRS1 - GR1-3 ) the RAT would pop up on power down at the Flight Line, then slowly retract.
I don't remember if there was one on the P1127 ( pretty sure there was ) Hugh Merewether would have found it handy when he dead-sticked a couple of times, into Tangmere & Thorney.
Those are the only occasions which spring to mind when the RAT was used, but doubtless there were others.
Mike Oliver ( Test pilot on the Gnat & Mij ) described going in the Dunsfold 'Hack' Dove to pick Hugh up, and seeing pools of molten metal along the Tangmere runway !
RAT's are frowned on now for military aircraft, which is all jolly well if not over a built-up area...
We have a Sea Vixen at Tangmere, I'll have a look at it & the pilot's notes re.RAT; I like to say I'm keen to fly in anything, but the coal-hole might make me reconsider...
28th Mar 2009, 09:17
How time distorts memories! There was no intention I assure you, in fact I wanted to get back to the arms of my middus after god knows how long away!