PDA

View Full Version : 757/767 drivers! RAT manual extension?


niallcooney
27th Feb 2002, 18:17
Just a quick question to all you 757/767 drivers about RAT extension. Let's say that you (just for fun <img src="wink.gif" border="0"> ) turn off all the HYD elec & demand pumps. If you hit the RAT button on the overhead, it indicates "unlocked" (amber), but does it indicate "PRESS" (green) on the button as well? In other words, does the RAT only work in a dual engine failure scenario?

Golden Rivet
27th Feb 2002, 20:40
Arming requirements for auto deployment are aircraft in the air,aircraft speed greater than 80KTS and N3 on both engines less than 47% (RB211 ).

The RAT will extend whenever the manual deployment switch is depressed. You will get an amber unlocked when away from the stowed position and a Green Press indication when the RAT has run up to speed and producing pressure &gt; 1275 psi. . .(fwd speed only !!)

Would'nt recommend you try this for fun ! The RAT comes out quick enough on the ground to take your head off if standing in the way !

[ 27 February 2002: Message edited by: Golden Rivet ]</p>

niallcooney
27th Feb 2002, 21:20
Hmmm. Thanx for the info. They could use the RAT as an alternate form of capital punishment in Saudi Arabia or wherever... "You are hereby sentence to death by 767 RAT extension". Bit inconvenient though...

cirrus01
27th Feb 2002, 23:11
If you ever get the chance to see a ground checkout of a RAT , my advise is run the other way !!!!. .After deploying the RAT you then backdrive it using Hydraulic pressure and check if it runs up to constant speeding by way of a LED light module.. .To do this you are standing some 2-3 feet away fom those whirling blades !........should add that the correct proceedure is to fit a cage around the RAT first ! I believe that there has been a few blade failures during testing (gulp)

SixDemonBag
28th Feb 2002, 06:42
Does anyone know of a picture online of the RAT. Interesed in seeing the damn thing.

OneDotLow
28th Feb 2002, 06:58
<a href="http://www.airliners.net/open.file?id=191739" target="_blank">CRJ Ram Air Turbine (close up)</a>

<a href="http://www.airliners.net/open.file?id=175572" target="_blank">B757 Ram Air Turbine (not such a good pic though)</a>

ODL

Thor Johnson
24th Mar 2002, 03:17
I've heard....... That while trying to troubleshoot inoperative auto-throttles inflight...... and if you were to pull both "speed card" circuit breakers..... . .. .auto RAT deployment.... (airplane thinks the engines just quit)!. .. .Dooh!

mono
24th Mar 2002, 08:35
B Shoe,. .. .Sorry mate but for 757/767 you are wrong. There is an airspeed switch (80 Kts) in the deploy circuit to prevent inadvertant deployment (see Rivets post) . Also prior to simulating air mode (or jacking the a/c) there is a huge list of cb's that have to be tripped to prevent various circuits activating when they shouldn't, including the auto RAT cb. further more pulling the speed card cb does not simulate a dead donk 'cos if your in the hangar its already dead (I hope, gulp). What needs to be done is simulate engines running for which there is a switch on the speed cards themselves (or an earthing point). . .. .Finally, ATPL, provided the RAT is extended and the a/c has a forward speed of more than 150 kts the RAT will supply enough pressure to light the press lt and power the centre hydraulic system. Landing speed may of course be a little lower than this, but then that's the pilots problem!!?. .. .Cheers <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" />. . . . <small>[ 24 March 2002, 03:38: Message edited by: mono ]</small>

tinyrice
24th Mar 2002, 08:43
Mono . .. .Isn't the 80 kt speed switch for the auto function only, I thought the drivers could manually override it from the overhead?

pterodactyl
24th Mar 2002, 09:35
Brown Shoe et al,. .I trust that the procedure being used to troubleshoot with regard to speed card CBs being pulled was in accordance with an appropriate checklist.. .. .CB resetting, pulling, cycling and the like should be strictly in accordance with authorised procedures. Otherwise the consequences can be unexpected and quite serious.. .. .An example of such experimentation occurred to a DC10. The very experienced FE persuaded the very experienced Captain and First Officer to try a little experiment by pulling the N1 sensing CBs to see what effect it had on the autothrottle response. To cut a long story short the result was quite dramatic and tragic.. .. .The number 3 engine fan speed increased rapidly and the engine exploded shedding fan blades in all directions penetrating the fuselage and a cabin window; pressurisation loss; passenger ejected; injury to other passengers; loss of electrical systems due to damage etc. Fortunately the crew managed to land the severely damaged aircraft successfully. I think if you search the Avnet data base for DC10 about 1973 you will find the full report.. .. .Another instance of a cabin fire and passenger deaths on a DC9 occurred as a result of repeatedly resetting a CB without following correct procedures.. .. .Experimentation is not a good idea.. . . . <small>[ 24 March 2002, 04:38: Message edited by: pterodactyl ]</small>

tinyrice
24th Mar 2002, 09:56
Right on! This is maintenance stuff only to be done in the peace and tranquility of a nice warm hanger. Kids dont try this while aviating.

mono
24th Mar 2002, 11:46
Freighterman,. .. .Yup you're right. I was just trying to state that you won't get auto deployment if in the air (jacked or simulated) and the speed card cb's are pulled.. .. .Cheers.. . <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" />

Thor Johnson
24th Mar 2002, 21:14
I agree that any troubleshooting not associated with a checklist is a big no-no. The auto deployment of the RAT did occur inflight after both speed card breakers were pulled at the same time. Happened to a friend and I'm just passing info gleaned from others mistakes.. .. .If its red or covered with dust, don't touch...

Golden Rivet
24th Mar 2002, 22:10
The 80kt speed switch was a mod - can't remember when embodied though.. . . . <small>[ 24 March 2002, 17:11: Message edited by: Golden Rivet ]</small>

mono
25th Mar 2002, 03:56
Rivet,. .. .The mod was actualy the addition of the air ground interlock, the airspeed switch has always been there.. .. .The mod was embodied many years ago when Boeing had several RATs deploy because of jet blast while queueing for T/O. (ground idle is borderline for the 47% N2 signal). .. .B Shoe, I owe you an apology, I thought the breakers had been pulled during maintenance T/S I did not imagine anyone would be daft enough to start pulling cb's in flight (outside of those specified in the QRH).. .. .Cheers.

Brenoch
2nd Apr 2002, 09:10
mono:

I believe the speed for the RAT to provide C HYD PRESS is 130 kts..

Atleast, thats what my QRH says..

Regards

Carbon Life Form
4th Apr 2002, 23:48
The RAT most positively WILL extend if you pull both speed card cb's, it happened at our airline and it has happened at Eastern and United airlines.

We now teach this scenario as part of recurrent and initial ground school. I think a suitably placed placard would also be a good idea
it's a matter of when and not if it will happen again.