Re: ETOPS question on Aer Lingus A330

Date:         01 Dec 97 02:33:54 
From:         kls@ohare.Chicago.COM (Karl Swartz)
Organization: Chicago Software Works, Menlo Park, California
References:   1 2 3 4 5 6 7 8
Next article
View raw article
  or MIME structure

>>The JT9D certainly was big enough for the 767-300 -- the first flight
>>of a 767-300 was powered by JT9D engines!  JAL was the only customer,
>>however, with 18 examples.

>Perhaps for the -300, certainly not for the -300ER. I am are of no
>-300ER's that are JT9D powered.

As I said, JAL had the only JT9D-powered 767-300s.  All were non-ER,
and thus there are no JT9D-powered 767-300ERs.  Which does not imply
that one could not have ordered such a beast, merely that nobody did.

BTW, I was incorrect in stating that there were 18 built.  That came
from a Boeing list.  I had forgotten that Boeing only notes the first
engine type purchased by an airline on a given airframe.  Only the
first 13 aircraft (built 1985-1990) have JT9D engines.  Beginning with
their 14th 767-300, built in 1994, they switched to CF6-80C2B2 engines,
possibly because of problems with the JT9Ds (either performance and/or
reliability) or perhaps simply because Pratt may no longer have been
willing to build JT9Ds.  (JAL also switched to GE for their 747-400s,
but back to Pratt for the MD-11 and 777.)

>QANTAS only bought the -300ER variant, and while you probably could
>use the JT9D on the -300ER, I don't know of anyone who did. It would
>imply a fairly sizeable loss in MGTOW. The largest JT9D is 56,000
>pounds, the CF6-80 used on the -300ER's is rated at 60,800 pounds
>thrust ...

No, *one* CF6-80 model used on the 767-300(ER) is rated at 60,800 lbs
thrust.  According to AvLeak's Source Book, engines with as little as
52,000 lbs thrust are available on the 767-300(ER).  As we've observed,
that's not always the most reliable reference, and one has to wonder
at what point the plane stops being an ER, so a better indicator may
be a real aircraft -- Gulf Air has 767-3P6(ER)s with relatively low
(for an ER) MGTOW of 387,000 lbs and 57,900 lbs thrust CF6-80C2B4
engines.  For the same application, lhrust levels for engines from
different manufacturers vary, with GE generally a bit higher than
Pratt, so a 56,000 lbs thrust JT9D seems plausible as a 767-300(ER)
powerplant, at least at lower weights.

In practice, most 767-300(ER) operators seem to have optioned them to
the highest weight possible, or very nearly so.  This and the fact
that the JT9D was both obsolete and endowed with more than its share
of problems is probably why no JT9D-powered 767-300(ER)s were built.

>>More plausible is that Qantas, like many JT9D operators, had not had
>>a good experience with them.  When they ordered their 767-300s, they
>>weren't about to repeat their mistake and order more Pratts, old or
>>new.  They switched from the JT9D to RB.211 for later 747 orders for
>>the same reason.

>I don't believe that was the reason. They bought the 767-200's long
>after the airline was buying 747's with RR engines.

Yes, but the RB.211 was not an option for the 767-200, at least not
at that time.  So, buying GE engines for their 767-200s would have
meant choosing to have three large turbofans in their inventory.
They ultimately did attain that dubious status when they ordered the
767-300s with GEs, but at that point it was a Hobson's choice.

>My understanding is they got better fuel economy on the
>RB211-524D4D's ... A few per cent difference in SFC if you keep
>flying 5-7000 miles leg is a lot of money as both fuel saved, and
>cargo carried.

As someone else noted, SFC doesn't mean much if it comes with greater
drag and/or weight.  Rolls long claimed lower fuel burn for the RB.211
while their competitors pointed out that the RB.211 was heavier and
that it had more drag, which collectively cancelled out the advantage
in SFC.

In practice, the 747SPs provided a good comparison.  Qantas flew their
RB.211-equipped versions on the same routes flown by Pan Am, and later
United, with JT9D-equipped 747SPs.  I've heard that Qantas had to
divert for fuel far less often, thanks to the RB.211s.  (Obviously
Qantas had a direct comparison between their JT9D- and RB.211-powered
747-238Bs, but I've never heard any comparisons of them.)

>>Nice engines, but you've got to be nuts to buy them on the 767
>>because the small world-wide fleet means their resale value is
>>extremely low.

>QANTAS knows all about that, they have a couple of 747-SP's that are
>unique. (They have the only SP's with RB211-524D4D's in the world), in
>fact there appear to be only 3 or 4 RR equpped SP's  ever built.

A total of six 747SPs were built with RB.211s.  (The other 39 have JT9D
engines.  Oddly, none were ordered with GEs.)  Besides Qantas's two,
the other RB.211-powered 747SPs were bought by Saudia (three) and UAE
Royal Flight (one, the last SP built).

--
Karl Swartz	|Home	kls@chicago.com
		|Work	kls@netapp.com
		|WWW	http://www.chicago.com/~kls/
"The average dog is a nicer person than the average person." - Andrew A. Rooney