Re: 747-400 Initial Cruise

Date:         29 Nov 97 03:24:33 
From:         Graeme Cant <graemec@ibm.net>
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James Matthew Weber wrote:
> I don't believe this.
>
> Cruise on a 747-400 at these mach numbers carries a huge fuel burn
> penalty. There is now ay the aircraft would make a Europe-Asia trip at
> those speeds. Long Haul Cruise on a 747-400 is M.82, while M.86 may be
> possible, I have never seen anyone do it.
>
>   Have anyone out there seen it?

Well, James, I have to say that I have.  Not only that, I've done it
myself - and been surrounded by a dozen other 747s doing it too.  In
fact, CI100 at max TOW at FL310 puts you at M.854 (+- depending on the
temp) in a RR -400.  It reduces during flight but you finish over London
around FL390 and M.84.

The PWs seem to cruise a smidgen (M.003) faster and climb about 4-5
tonnes earlier.

SIA don't like wearing out their computers so they do it even better.
They just fly M.86.  Period.  From Singapore to London. Non-stop.

> I've been in a D10 at m.85 (ATC kept asking us to go faster), when he
> asked again, the boss said, hey, we already doing M.85, I can't go
> much faster. The response from ATC was, OK, at least don't slow down
> for a while.

You probably had SIA behind you.

> 777's are often found at M.85, that is where they were designed to
> Cruise (it was an interesting way to attack the A340. On very long
> flight the difference in cruise speed has a very real impact on travel
> time).

I think they just didn't want to end up holding up their own 747s like
the A340 does.  The long-haul routes of the world largely move at
..84-.85.

Graeme Cant