Re: 747-400 Initial Cruise

Date:         20 Nov 97 02:53:42 
From:         Graeme Cant <graemec@ibm.net>
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Filip De Vos wrote:
>
> Jan-Olov Newborg (newborg@algonet.se) wrote:
> : Boeing 767 flying from Bangkok to Europe, many the times get final level
> : 270 inbound New Dehli, a common level for Beach 200, all because B767
> : cruises to slow compared to B747-400 and MD11 and traffic control keeps
> : 767 down at low alt...
>
> ... So much for Boeing's marketing claims that the big wing of > the 767
> allowed the aircraft to climb to high altitude quicker, giving an
> advantage over the small-winged A310.

Don't turn everything into a marketing battle, filip - and don't believe
everything you read on the internet.

NOBODY gets FL270 westbound to Delhi - he would hit the eastbound
traffic.  767s (Lauda and SAS mainly) often get FLs280 and 260 - but
then so do 747s and MD-11s and A340s.  It all depends on the traffic
density.  In a 747, I've been held down to Fls 220/240 from Calcutta to
the Iranian border on a couple of occasions.  FLs 260 and 280 are
common.

767s are usually not too bad because they can often accept 350 by half
way across the Bay of Bengal and usually by Calcutta (just as you claim
Boeing claimed, although I never heard it myself).  Only loss-making (=
few passengers) 747s can make it quite that early so the 767s CAN get
out of the road of the faster traffic.

Unfortunately, with radar only at Calcutta and Delhi, aeroplanes are
often held down by traffic, even when they have the performance to climb
because they can't get past the traffic at the intervening levels.

The worst problems are A340s - Virgin, Turkish, on my last trip Brunei -
who I DID read Airbus claim would cruise at comparable speeds to 747s.
They may be able to but only if they want to refuel half way.  If they
are trying to make Europe direct, or are simply operated in such a way
as will allow the owner to make a profit, they cruise some .04-.06 Mach
slower than the other traffic - 747s and MD-11s - and, unlike 767s, at
the same altitudes.

At any given point in the journey, 767 optimum altitudes are about
4000ft higher than 747 and A340.

> : After India over Afganistan and Russia higher level
> : is given to the slow B767.

And, due to some unusual topographical features (The Hindu Kush and the
Karakorams) in that area, higher levels are given to fast 747s and slow
A340s.  In fact, the lowest safe altitude is 290 or 310 depending on how
you work it.

At Delhi, the airway splits to  Iran and Turkey or north over
Afghanistan and the CIS.  This gives more capacity in the airway
system.  Also, on the northern route, the CIS has continuous radar cover
with much reduced longitudinal separation requirements than the 10
minutes over India.  So everyone gets their level - well, nearly
everyone.

Graeme Cant