ADA:Avro Jetliner C102-North America's First
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AVRO
C102 Jetliner
North America's First
1949-1956
This
republication has been made possible thanks to the assistance
of
The Society of Automotive Engineers and Dr. James C. Floyd. This
is quite a lengthy lecture and was presented in January 1950. We hope
you enjoy this piece of aviation history.
Scott McArthur. Webmaster, Arrow Recovery
Canada
DIRECT
OPERATING COSTS
                 While
it is not the purpose of this paper to join in the merry-go-round
of comparisons of the conventional and jet-powered transports
on a ton-mile per lb. of fuel basis, nevertheless, the
operating costs had to be considered very carefully,
and their consideration played an important part in the
final design confimration of the aircraft. 
                The
two important efficiency factors in the cost analysis
are the cost per mile and the payload for a given range.
                 The
cost per mile is obviously governed by speed, as manv
of the direct costs such as, crew salaries, depreciation,
insurance, etc. are fixed hourly costs. Neglecting fuel
consumption, if the blockspeed is increased from say
250 mph to 350 mph, the cost per mille would be
decreased by approximately 30%. It can and has been
shown elsewhere, that this decrease in cost due to speed
more than compensates for the increase due to higher
fuel consumption.
                The
effect of blockspeed can possibly be seen more clearly
by considering the number of aircraft required for a
given scheduling. The equation in its simple form is
shown below.
where
N=
     D     
     
U
x Vb x Np
 
 
N=
Number
of aircraft required
D=
Traffic
density in passenger miles per year
U=
Utilization
in hours per year
Vb=
Blockspeed
Np=
Passenger
capacity of aircraft
                For
a given yearly utilization, traffic density and passenger
capacity, it can be seen that if the blockspeed is doubled,
the number of aircraft required is halved, and consequently,
the earning power of each aircraft is considerably increased.
                To
take advantage of the higher blockspeeds, however, maintenance
and turn-around time at the airport has to be cut down
to a minimum, and the optimum climb and descent procedure
from operating altitude taken into account.
                The
high degree of pressurization and the incorporation of dive
flaps to allow a rapid descent; the use of special accessories
and radio compartments where practically all items that
required frequent servicing are housed; and the employment
of underwing pressure refueling are only a few of the
items, which have been incorporated to increase the economic
efficiency of the aircraft.
               So
far as the payload portion of the cost per ton mile efficiency
datum goes, the fuselage was laid out to give the best compromise
between a full passenger version and combined passengers
and cargo. Two typical lavouts are the 40 passenger version
with an additional 4,100 lb. of freight making a total
pay-load of 12,500 lb., and
the 50 passenger version with a payload of 10,500 lb.
Payload Vs. range with all ,allowances is shown on figure
6.
               While
the final analysis of economy must be left to the individual
airline, the results of a detailed analysis show that
the direct operating costs compare very favourably with
those of present transports, despite the relatively high
fuel consumption of present jet engines, and the fact
that the present allowances for stooge and flight to
an alternative airport are severe on the jet transport.
               It
is obvious that as the specific fuel consumption for
the jet engine improves, with the use of ceramic blade
materials, and higher compression ratios, and the flight
procedures are modified to cut down the stooge time,
the picture will be even brighter.
CABIN
LAYOUT
                Although,
the final seating arrangement and cabin layout will depend
on the customer's choice, it appears to be fairly
definite that the high density passenger version will
be the one of greatest interest,.
                Two
typical layouts are shown in figure 7. Accommodation
for 40 or 50 passengers is shown with provision for their
baggage on the left hand side of the cabin, adjacent
to the front entrance door. The washroom is
situated opposite this baggage compartment, and a small
commissary and hostess station is situated at the rear
of the passenger cabin.
                The
ten ft. diameter fuselage allows for wide seats, and
a generous aisle with a head room of 82 inches. Seat
pitching is at 38 inches.
               Emergency
exits are situated in the centre section and rear section
above the wing, and a crew emergency exit is fitted in
the ceiling of the crew compartment.
               A
permissible C. G. travel of approximately 23%.of the
mean chord or approximately 35 inches provides for flexibility
of loading with the least number of restrictions.
Noise
Level and Vibration
             Noise
level in the cabin is considerably reduced by the use
of turbojets, and this, coupled by a complete lack of
vibration, will add enormously to passenger comfort.
 POWER
PLANT
               The
four Derwent 5 engines are mounted in pairs in two under-slung
nacelles, each nacelle being made up as a single integrated
structure. The engines are toed-in toward the centre
line by 5 deg, and set at approximately 11 1/2 deg to
the horizontal in order to take the jet pipes under the
main spars without cutting away
any of the spar structure.
               Tubular
engine mounts are used, and these can be removed or replaced
separately. The nacelle geometry is shown in figure 8.
All nacelle air loads are taken back into the two engine
mounts, which are attachedto the centre section front
spar.
               Engine
servicing and maintenance is made particularly easy by
the low position of the nacelles. All engine
adjustments can be made without the necessity of using
service ramps or ladders, see figure 9.
               Engine
removal is carried out by detaching the services and
gear drive at the break points, swinging the trunnion
locating caps down, and dropping the engine on to the
special trolley. The engine is then wheeled away sideways
to make way for the replacement engine. With this unique
arrangement, a complete engine change can be made in
a very short time.
               The
jet pipes are parallel in plan and are supported on trunnions
and links. Two spherical joints are incorporated to give
flexibility to the pipes on expansion, and also for the
withdrawal of the jet pipe for engine removal. Although,
a relatively long jet pipe is used, it Is estimated that
less than 1% of thrust is sacrificed from the combined
effects of length and shape of the pipe.
              A
sixteen inch nozzle is fitted and the jet emerges at
7 deg. to the datum line of the aircraft, to bring the
line of action of thrust as close to the C. G. as possible.
                 The
jet pipe runs through a tunnel of stainless steel formed
by firewalls attached to the adjacent structure. The
jet pipe itself is insulated, and is cooled by a flow
of air passing through the firewall tunnell and induced
by the extractor nozzle. The vena-contractor at the nozzle
sucks the cooling air through the nacelle, after it enters
through louvres at the forward end of the cowling.
Engine
Accessories
                 The
main accessories driven by the engines are mounted on
an accessory gearbox located between the engines in each
nacelle,and attached to the wing front spar. The gearbox
contains two completely independent
gearing systems, each driven by one engine, and each
having independent lubrication.
                 Each
inboard engine drives a cabin blower, a vacuum pump,
and a Tachometer generator, and each outboard engine
drives a 50 KW alternator, a 9 KW generator, an hydraulic
pump, and a Tachometer generator.
                 The
gearbox drives are connected with the engines by a system
of drive shafts linked by means of flexible couplings,
as shown in figure 10.
Derwant
5 Modified Engines
                The
C-102 engines are standard Rolls-Royee Derwent 5 engines
but with a completely redesigned oil tank.
The cast oil tank is sited at the front of the engine,
underneath the forward gear drive. The engines are handed
only by the oil tank filler and the gear take-off, see
figure 11.
                 The
change from starboard to port engines is made simply
by interchanging the filler neck and blanking plate on
the oil tank and swinging the gear take-off around in
the opposite direction. The oil tank and system are integral
parts of the engine.
 Engine Suspension
                The
engine is supported by mounting trunnions at approximately
the center of gravity of the engine, and is steadied
at the rear and by a shackle plate bolted to the top
of the nozzle box.
 Cowling
               The
upper part of the cowling is developed as a permanent
structure provided with small access doors for engine
slinging, and a larger door to permit access to the upper
part of the accessory gearbox.
                  The
lower half of the cowling consists of two large access
doors hinged at the sides and a smaller door beneath
the accessory gearbox swinging aft. All access doors
are locked by means of flush-type quick release fasteners,
and the  two main curved doors can be quickly
detached by swinging them out and unhooking  the
special hinge locators.
"Copyright
1951 Society of Automotive Engineers, Inc. This paper
is published on this web-site with permission from the
Society of Automotive Engineers, Inc. As a user of this
web-site, you are permitted to view this paper on-line,
download the pdf file and to print a copy at no cost
for your use only. Downloaded pdf files and printouts
of the SAE paper contained on this web-site may not be
copied or distributed to others or for the use of others."
CONVERTED
TO HTML, AND HYPERLINKS ADDED, January 17, 2002.
Scott McArthur.
ONLINE
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