What Went Wrong?Why some commercial aircraft programs
didn’t live up to expectations
AIAA Southern California ASAT
Conference
April 30, 2016
Tony Hays
California State University Long Beach
Selected Programs
• De Havilland Comet
• Lockheed Electra
• Convair 880/990
• De Havilland Trident
• Vickers VC10
• Dassault Mercure
• BAC/Sud Aviation
Concorde
• Lockheed L-1011
• VFW-Fokker 61
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1: de Havilland DH 106 Comet
• Comet 1: First flight July 1949
• Entered service May 1952
• Pax: 36-44 Range: 1,300
nmi.
• Two aircraft broke up in flight
in 1964
• Comet 4 entered service in
1958, with 30 year service life
4
Source: www.extremetech.com
Comet 1
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Engines Embedded in Wing Root
7
• V-bomber triad – Vulcan, Valiant, Victor
• First generation of strategic jet bombers
• Contemporaneous with B-47
• British obsession with minimizing wetted area at
expense of everything else
Source:www.telegraph.co.uk Source: en.wikpedia.org
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© Nathan Daws Source: airliners.net
Comet Accident Investigation
• Fatigue failure of
frame of escape
hatch
11
Source: www.greatwen.com
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Comet Lessons Learned
• Do as many trade
studies as time and
money permit
• Include the “-ilities”
– Supportability
– Reliability
– Maintainability
– Vulnerability
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• Design for derivatives
– Payload
– Range
– Propulsion system
• Be prepared for
“unknown unknowns”
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2: Lockheed L-188 Electra
• First flight Dec 1957
• First US commercial
turboprop
• Up to 80 pax / 1,913 nmi.
• Wing root fatigue failure in
Sept 1959 and March 1960
due to loosened engine
mounts
• Public lost faith
• Production ended in 1961 at
170 aircraft
14
Source: commons.Wikimedia.org
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Electra Preceded by Vickers Viscount
• First flight 1948
• Entered service 1950
• 4 X R-R Dart turboprops
• Up to 75 pax / 1200 nmi.
• Total production of 445
15
Source: commons.Wikimedia.org
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1945 1955 1965 1975 1985 1995 2005 2015
De Havilland Trident
Boeing 727
Vickers Vanguard
Lockheed Electra
Vickers Viscount
Service Period and Production Quantity
16
Data source: Wikipedia
2016-04-28
1,832
170
44
445
179
Electra Eventually Replaced by B.727
• Up to 189 pax
• Design development
~1960
• First flight Feb 1963
• Entered service Feb 1964
• Production ended in 1984
with 1,832 aircraft built
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Source: theairlines.net
Success as P-3 ASW
• Total of 734 built
• Eventually to be replaced
by Boeing P-8A (IOC in
late 2013)
18
Source: US Navy
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Model 188 Lessons Learned
• Meet customers’ expectations (they wanted jet
comfort and low vibration levels)
• Too late for a large turboprop (at first flight,
Viscount had been operational for 7 years)
• Be lucky, your design may just have other
applications
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3: Convair 880/990• First flight Jan 1959
• Belated attempt to enter
four-engine transport
market (B.367-80 first flight
in July 1954)
• Five abreast seating
– CV 880 110 pax / 2,943 nmi.
– CV 990 149 pax / 3,124 nmi.
• Mcruise = 0.91 (CV990)
• Production
– CV 880 65
– CV 990 39
20
Source: commons.wikmedia.com
Convair CV 990
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Application of Kücheman
Carrots
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Source: aviation.stackexchange.com
Strong shock on upper surface Shock reduced
Convair 880/990 Competition
• Boeing 720
– first flight Nov 1959
– 149 pax (one class)
– Range 3,680 nmi.
• Boeing 727-100
– First flight Feb 1963
– 149 pax (one class)
• Boeing 727-200
– 189 pax (one class)
23
Source: commons.wikmedia.com
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1955 1965 1975 1985 1995 2005 2015
Vickers VC10
Convair 880/990
Douglas DC-8
Boeing 707
Service Period and Production Quantity
24
Data source: Wikipedia
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556
104
1010
54
Convair 880/990 Lessons
Learned
• Too late to the party
• Difficult to find niche on payload-range plot that
can’t be filled by derivative of another aircraft type
• GE805 had higher SFC than PWC JT-3C on 707
• Higher cruise Mach didn’t result in significant
reduction in operating cost
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4: De Havilland DH 121 Trident
26
Source: century-of-flight.net
• First flight Jan 1962
• Designed to 1957 BEA
requirement for 88 pax
• 3 R-R Speys
• Trident 1: 101 pax
• Range: 1,170 nmi.
• Entered service March 1964
• Production ended in 1979
with 179 aircraft
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Trident 3B
Trident Handicaps
• UK government insisted on merger with losing competitor
(to form Hawker Siddeley)
• Too small for worldwide market
• Shared design details with Boeing
• Long flight test cycle (two years vs. one for Boeing)
• Low production rate (12/year vs. 80-100 for Boeing)
• Limited growth potential (couldn’t re-engine)
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Trident 3B had 3½ Engines
29
Source: www.airliners.net
• 3 R-R Speys
Fn = 3 x 11,960 lb.
• 1 RB.162 Fn = 5,250 lb
– Designed as lightweight
lift jet
– Added 15% takeoff thrust
with 5% increase in
TOGW
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© Paul Markman
Trident Lessons Learned
• Don’t allow launch customer to dictate specs
• Don’t show design details to a competitor
• Commit manpower and facilities for quick entry
into service and adequate production rate
• Design for growth in MTOGW
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5: Vickers VC10
31
Source: wikimedia
• First flight June 1962
• Designed to BOAC
requirement ‘hot and high’
airfields on Empire routes
• 4 R-R Conways
• Entered service April 1964
• Production ended in 1979
with only 54 aircraft
manufactured (inc. Super)
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VC10 Characteristics
• Clean wing (Vapp approx. 10 kt less than 707)
• Low cabin noise
• BOAC calculated DOC/pax mile ~3% higher than for
707 (and made this public)
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VC10 707-320
TOFL [ft] 8,280 ~10,800
LFL [ft] 6,380 ~7,500
Field Performance
Source: airliners.net Source: Boeing Performance Manual
Fuselage And Wing Root Bending
• Additional wing
and fuselage
bending
• Cabin not centered
over wing
• Made worse by
– Stretched fuselage
– Higher BPR
(heavier) engines
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McDonnell Douglas MD-80
Larger C.g. Travel
35
Douglas DC-9-20
• C.g. moves
forward as
aircraft is
loaded
• Problem made
worse with
heavier
engines
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Source: Schaufele
More Difficult to Control C.G. Location
• C.g. location is aft at OEW and forward at MTOGW
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More Difficult to Control C.G. Location
• When defueling, remove fuel from fin tank first
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RAF Brize Norton, Dec. 1997
© Crown Copyright
© Crown Copyright
VC10 Handicaps
• We/Wto = 0.47 compared with 0.44 for B707-320
• Higher cruise drag than predicted due to nacelle/pylon
geometry
• Runways lengthened to accommodate 707/DC8
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• Geometry modified to
maintain (or increase)
isobar sweep at wingtip
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Added Küchemann Wingtips
Source: Küchemann, Aerodynamic Design of Aircraft
Source: http://www.airliners.net/aviation-
forums/general_aviation/print.main?id=6249338
DH Trident 2E modIsobar comparison
VC10 Nacelle and Pylon Mods.
• Extended fairing between engine nacelles
• Extended pylon trailing edge
• Moved nacelles outboard
• Eliminated inboard thrust reversers
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Before After
VC10 Uncontained Failure
41
http://www.vc10.net/History/incidents_and_accidents.html#Engine Disintegrates
• Departed LHR, Nov 1969
• LP turbine blades shed from
No. 3 engine
• Penetrated No. 4 engine
which caught fire (quickly
extinguished)
• Returned to LHR 90K lb over
max landing weight
• Blew fusible plugs
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VC10 Lessons Learned
• Don’t allow launch customer to dictate specs
• Don’t allow a penalty in payload-range unless
commensurate benefit is justified
• Take account of potential changes in the operating
environment
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6: BAC/Aerospatiale Concorde
43
Source: commons.Wikimedia.org
• First flight March 1969
• UK-French government joint
development agreement in
Nov 1962
• 90-120 pax
• Range 3,900 nmi.
• Cruise Mach 2.02
• 4 X B-S Olympus Mk 593
• Production ended at 20 a/c
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Concorde Handicaps
• Development cost 6X original estimate
• Flown supersonically only over water
• 1973 oil shortage deterred buyers
• 15.8 pax miles/gal, compared with B707 33.3 pax
mpg, B747 46.4 pax mpg, DC-10 53.6 pax mpg
• Banned from operation at some airport because of
perceived noise
• In July 2000, AF Concorde crashed at CDG due to
fuel leak/engine fire
• Withdrawn from service 2003
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Concorde Accident at CDG
• In July 2000, AF Concorde crashed at CDG due to
fuel leak/engine fire
45
Source: en.wikipedia.org
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More Concorde Handicaps
• Government to government contract prevented
unilateral withdrawal
• Development costs not adequately controlled
• Profitable operation doubtful, even before 1973 oil
crisis
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Concorde Lessons Learned
• Manufacturers must take responsibility for
success or failure
• There is a big difference between
technological possibility and economic viability
• Safety is paramount
• Pioneers may get all the glory, but they rarely
make all the money
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7: Lockheed L-1011 Tristar
48
Flight test aircraft at Palmdale
• Designed to AA requirement
for ORD-LAX, LGA-ORD
• Capable of operation from
LGA (7000 ft)
• 3 X R-R RB.211
• New production facilities at
Palmdale, CA
• First flight Nov 1970
• Production ended in 1985
with 250 aircraft
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Source: www.airlinereporter.com
L-1011 Direct Lift Control
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Source: © DIASpotter
With landing flaps
deployed, spoilers linked
to control column for direct
control of rate of descent
L1011 Direct Lift Control
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Source: www.flightaware.comr
Direct control of rate of
descent without changing
pitch attitude
L-1011 Maneuver Load
Control/Gust Alleviation
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Source: Lockheed
Deflect ailerons t.e.
up to reduce wing
root BM during
maneuver or gust
Overall lift
unchanged
e is reduced
Enables higher wing span (and reduced drag) for
same maximum wing root bending moment
L-1011 All-moving Horizontal Tail
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Source: Green & Swanorough, Commercial Aircraft
Triple-redundant
horizontal tail
hydraulic actuators
L-1011 Handicaps
• Almost identical mission requirement to DC-10
– Fierce competition for sales
– Offered too cheaply
• Bankruptcy of Rolls-Royce during development
• Uneven production required training new labor
• Production facilities too far from source of labor
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History behind Rolls-Royce Downfall
56
CX-LHS Program (1963)
Boeing CX-LHSDouglas CX-LHS
Lockheed C-5AGE TF-39 P&W JT-9D
GE CF-6
Boeing 747-100 Douglas DC-10 Lockheed L-1011 Airbus A300(UK-France MOU signed 1967)
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Lockheed Plant 10
58
http://www.astrosurf.com/luxorion/vaisseaux-falcon-sls-dragon-orion2.htm
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Theoretical Scissors Plot
59
• Development cost ~$5 B
• Aimed for breakeven at
250 aircraft
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Actual Scissors Plot
60
• Early sale price
reduced to build market
share
• 50 aircraft sold to Air
Holdings Ltd
• When production
picked up, new
employees had to be
trained
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L-1011 Lessons Learned
• Don’t go head to head with an identical
product
• Design for different engine options
• Design for growth in MTOGW
• Build airplane near skilled labor pool
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8: Dassault Mercure
62
Source: wikimedia
• First Dassault airliner
• First flight May 1971
• Designed for 120 – 162 pax
• Stage lengths up to 1100
nmi.
• 2 X JT-8D
• Entered service June 1974
• Production ended in 1979 at
54 aircraft (inc. Super)
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Dassault Mercure Handicaps
63
Source: wikimedia
• Dassault not a recognized
commercial a/c manufacturer
• No significant performance
improvement over B737
• DC-9-50 matched payload-
range of Mercure 100
• We/Wto = 0.57 compared with
0.52 for B737-200
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Mercure Lessons Learned
• Difficult for an unknown commercial
aircraft manufacturer to break into an
established market
• Derivative designs can fill market holes
more cheaply than new designs
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9: VFW-Fokker 614
65
Source: commons.Wikimedia.org
• First flight July 1971
• DC-3 replacement
• 40 – 44 pax
• Range with 40 pax = 645 nmi.
• 2 X R-R/Snecma M45H
turbofans
• Production ended in Dec 1977
with 16 airplanes
• Last flight Dec 2012
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VFW 614 Field Performance
66
Source: http://www.vfw614.de/die_vfw_614_e.html
• Better field performance than DC-3
• Not true STOL (2000 ft TOFL)
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Engines Mounted on Top of Wing
• Advantages
– Wing root bending relief
– Short landing gear and airstairs
– Protection from FOD
– Fan noise reduction on ground
• Disadvantages
– Reduced length of t.e. for flaps
– Inlet in high-speed flow
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HondaJet
Hybrid Wing Body
• Lockheed Martin studies
started in 2009
• Carries outsized cargo
lifted by C-5
• Burns 70% less fuel than
C-17
• Over-wing nacelles permit
very-high-BPR engines
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VFW-Fokker 614
source: aviationweek.com
Operating Cost Comparison
69
Seats: Wikipedia
DOC: https://www.flightglobal.com/FlightPDFArchive/1968/1968%20-%200119.PDF
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2
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
3
0 20 40 60 80 100 120
DO
C/s
ea
t m
ile
Maximum seats
Trends in DOC/seat mile vs. Capacity
VFW-614
FH-228
HS.748
F.28
DC-9-10
VFW 614 Handicaps
• DC-3 was cheap and ubiquitous
• VFW 614 had higher price, higher fuel burn
• Rolls-Royce bankruptcy in Feb 1971
• Lost test a/c due to elevator flutter in Feb 1972
• VFW not known as commercial aircraft manufacturer
• Rolls-Royce (Bristol Siddeley) M45H was a new engine
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VFW 614 Lessons Learned
• Very difficult to design viable aircraft at bottom
end of market that meets FAR 25 (i.e., > 20 pax,
or > 12,500 lb TOGW)
• Keep to design goals (including costs)
• Try not to introduce new airframe from unknown
manufacturer with new engine
• Don’t build a Mercedes Benz when a VW is
wanted
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Conclusions
• Be prepared for
“unknown unknowns”
• Do impartial trade studies
• Ensure performance
capabilities will be
utilized
• Don’t compete with an
identical product
• Design for derivatives
• Don’t compete where an
existing product is well
established unless your
product is demonstrably
superior
• Ensure technology is
proven
• Safety is paramount
• Be lucky
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