Originally posted by vyniker:
[b]Hi all,
I realise that SIA's choice of engines and the ones 'recommended'
at Boeing's website are different.
Plane-----------------Boeing
site------------SIA----------------Remarks
772-------------------Trent 877--------------Trent
884--------Higher
772ER----------------Trent 895--------------Trent
892--------Lower
773-------------------Trent 892--------------Trent
892--------Same
773ER----------------GE90-115B------------GE90-115B------Same
744-------------------PW4062----------------PW4056---------Lower
First and foremost.
- SIA does not have B777-200s. All of SIA's B777-200s are ER
versions.
- That said, all of SIA's B777-200s come with Trent 892s. The
regional 772s are then electronically downgraded to 84,000 lbs max
thrust hence rendering them similar to Trent 884.
My questions are
1) Why is there no specific trend of more powerful engines or less
powerful engines ? Why were some planes fitted with more powerful
ones and some less powerful ones ?
Lets just use the 772s as Eg. The takeoff weight for a regional
772 is usually much less than a long haul 772. With a lower take
off weight they require less power, and thus, lower engine
thrust.
2) The 773ER are to be fitted with GE engines. That is
understandable as I believe the Trent 895 is the most powerful
Trent 800 engine and its inadequate for the 773ER. Am I right
?
Yes, and also because of an exclusivity deal that GE has with
Boeing to produce the GE90-115s.
[qupte]
What I do not understand is why are the 744 not fitted with Rolls
Royce RB211? Won't SIA save money by using as many engines as
possible from the same maker ?[/quote]
No, why should it save money? IIRC there's an advantage in using
the PW engines, think they are the most economical ones but cant
confirm that.
3) The 744 has a maximum takeoff weight of 397 000kg. The 773ER has
a MTOW of 351 000kg. The 744 uses PW4056 and the 773ER uses
GE90-115B.
56 x 4 = 224.
115 x 2 = 230.
Why does the heavier plane, 744, require less thrust ?
My guess is the requirement is for the remaining engines to be able
to continue the takeoff even if one engine fails.
56 x 3 = 168.
168 > 115.
Is that the correct reason ?
A 777 requires enough thrust to take off on should 1 engine fail
on to. If 1 engine on the 777 fails, there's only another to
complete the to.
On a 744, if one fails, you have another 3 to complete the
work.
