Re: Older Aircraft

Date:         16 Sep 97 02:35:27 
From:         kls@ohare.Chicago.COM (Karl Swartz)
Organization: Chicago Software Works, Menlo Park, California
References:   1 2 3
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>>birds as they can.  If you look in the right corners of the world,
>>you'll still find 707s soldiering along, and even older props.
>.....
>>an American carrier -- Airborne Express.  No DC-8s are still flying
>>passengers (other than charters) within the US, but plenty of them
>>are still flying freight.

>Just wondering: is the inference (from above) that the 707 is mainly
>still in service for passengers, and the DC-8 mainly freight, valid or
>not?

Most or all of the DC-8s flying cargo in the US are 50 series or later
models, which (except for the DC-8-63F Jet Trader) are comparable to
the 707-320C in cargo lift, but have higher MGTOW and thus can carry
more fuel (read: longer range) with a full payload.  In addition, a
good number of them are Super 70s -- Super 60s re-engined with quiet,
fuel-efficient CFM56 engines.  Commericial 707s have no such option
available (ignoring the one-off 707-300 and the KC-135R and related
military conversions) and thus will be further hobbled by hushkits if
they're to fly in much of the world after 1999.

I didn't say that those 707s in out-of-the-way places are carrying
passengers, though some are.  I think it's more a matter of the more
financially able cargo carriers buying up DC-8s for their superior
cargo capabilities, leaving a relative abundance of 707s on the used
market for cash-poor third-world carriers.

>Also, something that puzzles me.  What makes the economics of air freight
>dictate older passenger jets?  Presumably some of the reasons passenger
>airlines are no longer flying DC-8s and 707s is that the turbojets are
>noisy and inefficient compared to turbofans.

Many cargo operations are primarily charter, and their aircraft may
sit idle for extended periods of time.  Others are very hub-based with
a single hub, which means most of their aircraft fly a single round-
trip per day.  (FedEx being the obvious example of the latter.)

With this sort of low utilization, the lower capital cost of older
aircraft outweighs the better operating aircraft of newer aircraft.

As an example, someone else mentioned a ~30-year old DC-9 which had
reportedly flown over 100,000 cycles for Northwest.  That's an average
of a bit over 9 cycles per day.  If it's estimated that it has another
10,000 cycles left and it's up for a D check (an extensive rebuild
that takes place every nine years), Northwest won't bother because
they'll expect to get a little over 2.5 years of service out of it.
In contrast, Airborne, flying a single round-trip, would be able to
get over 13.5 years out of it before using up the 10,000 cycles,
making it economical for them to invest in the D check.

--
Karl Swartz	|Home	kls@chicago.com
		|Work	kls@netapp.com
		|WWW	http://www.chicago.com/~kls/
Moderator of sci.aeronautics.airliners -- Unix/network work pays the bills