Re: Please answer - 757/767 Hydraulic Question

From:         tdlowe01@ulkyvx.louisville.edu (Tony D. Lowe)
Organization: University of Louisville
Date:         17 Feb 93 14:09:37 PST
References:   1
View raw article
  or MIME structure

In article <airliners.1993.178@ohare.Chicago.COM>, bwood@nssdca.gsfc.nasa.gov (William Wood) writes:
> He stated that its proported purpose is to assume the intake
> of forced wind through it's intake channels, which then
> force the turning of its 'turbo-prop' which acts-out as
> a wind-propelled electric generator (to allow steerage
> of the plane having restored the power to the hydraulic
> systems of the plane).

It's called a Ram Air Turbine or RAT (also sometimes called a ramjet).  It's
purpose is to provide hydraulic power in the event of total engine failure. 
I do not believe that it is deployed if one engine is still running, but I
wouldn't swear to it.  It is located underneath the plane, just aft of the
right rear landing gear and is covered by a 2 by 4 foot door (approx) that
is released by explosive bolts.  The RAT itself is on a swing arm that is
mounted aft and falls from fore to aft such that the forward motion of the
plane aids in deployment and locks it into place.  This is the same force
that drives the small prop (I definitely wouldn't call it a "turbo prop").

I've never actually seen the RAT deployed.  I have only seen technical
drawings during fueler safety meetings on "Why you shouldn't be under the
RAT".  Because it would hurt if the thing deployed while you were under it!

> Also, if it is a truth, would this also be the case in the design
> of the 767 as well??

The 767 has something like an 85% parts compatibility with the 757, so I
would guess it would have a similar RAT.
-- 

  Tony D. Lowe, The HapMaster  BITNET:   tdlowe01@ulkyvx.bitnet
  University of Louisville     INTERNET: tdlowe01@ulkyvx.louisville.edu
       "People without a sense of humor don't have any sense at all."