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Re: was Arcjet, now solid boosters






>From: sco@sco-inc.com
>To: "Robert Oler" <cvn65vf94@msn.com>
>CC: amsat-bb@AMSAT.Org
>Subject: Re: [amsat-bb] was Arcjet, now solid boosters
>Date: Tue, 05 Jun 2001 00:28:33 -0400
>
>
>>>
>>>At 07:39 PM 6/4/2001 , you wrote:
>>>>Especially maintenance.  The airlines have long known that the per-unit
>>>>cost of jet engine maintenance is the same whether the engine is 20000,
>>>>50000, or 90000 pounds thrust.  Labor cost is the driving factor here,
>>>>not parts cost. This is the overriding reason why the Boeing 777 has
>>>>only two engines (or so a GE employee told me a few years ago).
>>>
>>>Over the USA if you lose one of those engines you can make an emergency
>>>landing ... hopefully.
>>>But over water to Hawaii and you will go swimming, there is no backup or
>>>place to land. You can only ditch at sea. If it at night (like coming 
>>>back
>>>from Hawaii usually is) then you go into the water in the dark, not a 
>>>very
>>>pleasant thing to consider.
>>>
>>>W4SCO
>>
>>Well...lets sort out Apples from oranges...first lets talk about two
>>engine airplanes (turbojets).  Two engine jet airplanes operating over
>>water must meet ETOPS requirements and be within certian distances from
>>land AT ALL times.  These numbers have gotten larger as the reliability
>>and record keeping on large turbofans has gotten larger.
>>
>>But in terms of an engine failure the remaining jet (and the pilot) doesnt
>>really care wheather or not they are over water or over the Rocky
>>Mountains (indeed under certian circumstances I would rather be pushing
>>the mighty twin (the triple seven) across the mighty water (the Pacific)
>>then say the little twin (the B-737) over the Rockies...
>>
>>Put it another way if you have to shut down an engine at the PNR (the
>>point of no return) from KLAX to KHOU in a 777 or 767 or 757 or 737 the
>>passengers would only know it because a prudent captain would put the vest
>>on etc...it wouldnt be any more or less exciting then losing one from KLGA
>>to KLAX....it just would take you a little longer to land (landings over
>>land must be made within one hour if you have an engine failure in a twin)
>>whereas it might take a little longer over the water...but statistically
>>you would still be as safe...ie the chances of losing the other one as
>>remote and the airplane would fly quite nicely (indeed you wouldnt have to
>>get over those nasty mountains).
>>
>>In short twin engine ops over water is NBD (no big deal)...Ditching in an
>>airplane with wing mounted turbofans is quite unlikely to occur
>>successfully either day or night.
>>
>>Four engines are a little different (ie the range rates are based on 1
>>out) and three engines are based on 1 out.  Its a myth that you could lose
>The Tomcat is a cool airplane ... you have two side by side engines. Would
>you like to lose one at 40,000 feet and then have to fly with minimal
>instruments thru 1200 miles thru a level 5 huricane in the dark?   I assume
>Boeing tried this feat with the 777 in order to get certified to fly the
>Pacific to Hawaii from the mainland. Hopefully they can balance the load by
>pumping fuel between the wing tanks?<<

These are not really great problems.  The triple seven can cross feed its 
wing tank fuel and its easy to keep the wings in balance or ligthen up the 
one where the engine is "dormant".

As for instruments...you dont lose any instruments in teh 777 with an engine 
failure even if you cant start that APU (and you can).  And no one is going 
to fly anything through a level five hurricane (you wouldnt dispatch in teh 
direction of one with all motors running.

An engine failure is really quite trivial in terms of being able to control 
the airplane.  You dont "fall" from FL350 you drift down...it might take you 
as much as 200-250 miles to make the descent (you put the remaining engine 
at Max continuous power and let it "drift down" to the new cruising 
altitude...even with a four engine airplane one is "drifting down".)

Passengers are rarely happy when you tell them an engine has failed but it 
happens SO INFREQUENTLY.

Always safer to put it down on a level piece of
>land
>(even the Great Salt Lake) than to attempt a diching at sea with waves in
>the dark. Remember going to Hawaii you are out of radar contact. No one
>knows where you are unless you tell them. But now with GPS I wonder if
>there is a way to track planes like Onstar can track vehicles on land?
>

ACARS (now through the satelites) tells every one exactly where you are...

Turbojet flying is about the safest form of transportation known to modern 
man AND two engine over the water isnt that big a deal...it really isnt.

(a Skyhawk is a great plane to...)

Robert
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