731 Falcon 20

PILOT REPORT
O
perator Survey:
731 Falcon 20
Built to endure, many of Dassault’s popular
Falcon 20 business jets are enjoying a new
longer-legged, more economical lease on life.
By ROBERT L. PARRISH
August 1992, Document No. 2604 (4 pages)
In the corporate segment of aviation, where inflated
development and certification costs coupled with a congressionally
mandated luxury tax appear to have
clamped a damper on new aircraft sales, there is a
glimmering hope for continuing expansion. It lies in the
visibly growing business of marrying the latest technology
propulsion systems and avionics with seasoned but
still airworthy airframes.
One of the more promising of these programs is the
retrofit of the Dassault Falcon 20 with EFIS and Garrett
TFE731-5 series turbofan powerplants. Depending
on options, the cost ranges from $4.3 million to $7.5
million.
Designed in the late 1950s and placed in production
in 1965, the Falcon 20 was the first (and allegedly is
still the only) business jet to be put through the fatigue
test equivalence of 90 years of flying, thereby earning
FAA certification with no life limits on the airframe.
Originally powered with General Electric CF700
fanjet engines rated at 4,125 pounds takeoff thrust,
the 26,455-pound gross weight standard Falcon 20
provided spacious cabin comfort that passengers
found appealing but with speed, altitude and range
limitations that were often anxiety-inducing to
flightcrews. Over a production span of nearly 20
years, power and gross weight increases, and other
improvements were incorporated into successive Falcon
20 models. Nearly 500 units were delivered
worldwide before the Garrett ATF3-powered Model
200 superseded the series in 1985.
To Garrett conversion specialists who previously had
engineered popular engine retrofit programs for the
Lockheed JetStar and British Aerospace 125 series business
jets, that production volume represented a target
with far greater long-term potential than their earlier
undertakings. The company therefore disclosed in
1987 plans to develop a TFE731 turbofan conversion
for the Falcon 20 series that would improve performance
and operating economy across the board, and
virtually double the effective nonstop range.
In March 1989, FAA and French certification of the
731 Falcon 20, powered by 4,500-pound-thrust
TFE731-5AR engines, was achieved. Last fall additional
approval was obtained for installation of the 4,750-
pound-thrust 731-5BR in the aircraft. As of mid-June this
year, Garrett had delivered 51 of the -5A-powered 731
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Falcon 20s. At that time, the company claimed a growing
backlog of orders for the Falcon 20B version of its
retrofit (incorporating the 731-5B and promising further
performance improvements over the -5A version). The
base price was $3.5 million for installation of the new
engines, pylons, nacelles and associated wiring, plumbing
and cockpit instrumentation.
To determine how effective the 731 Falcon 20 retrofit
program has been so far, B/CA surveyed operators of
more than half those conversions currently in use.
Though a number of operators reported that some of
the claimed performance upgrades reflected “best
case” optimism, virtually all agreed that the enhancements
overall more than justified the contention that the
retrofit gives the 30-year-old design a whole new productive
life.
Most of those surveyed said that the Falcon 20 had
been part of their company fleets prior to retrofit.
Lengths of time in which those aircraft have been operated
since conversion ranged from four months to
about three years. While the TFE731-5A installation
alone was priced at $3.05 million in 1990 when the
majority of conversions took place, those disclosing
total investment reported outlays between $4.3 million
and $7 million. This was because virtually all aircraft
involved incorporated outstanding Dassault service bulletins
and the Dee Howard $275,000 thrust reverser
option, and a substantial number converted to Garrett’s
GTCP36-150 APU. One-third of all retrofits have
included EFIS upgrades at $1 million or so, and most
underwent interior refurbishing and painting either in
conjunction with, or prior to, the engine retrofit. Three
operators who acquired their Falcon 20s already
retrofitted reported purchase prices between $6.5 million
and $7.3 million.
With the resolution of TFE731-5B engine gearbox
problems (B/CA, July 1992, page 73) the retrofit is
now being offered only in the 731 Falcon 20B version.
That version reportedly will afford significantly better
performance than the 731-5A version, especially in hot
day takeoff, balanced field and climb characteristics
(see accompanying comparison chart). Garrett marketers
claim that efforts are being made to avoid retrofit
price increases in the near-term, so the cost range indicated
above should remain relatively unchanged.
But operators of only eight of the 51 units completed
as of mid-June expressed interest in “re-retrofitting” from
the A to the B version. That is in spite of the fact that a
number of operators felt that the takeoff performance of
the AR version shows some derogation from CF700
performance under hot day conditions.
Interestingly, mission profiles for most Falcon 20 operators
have remained relatively unchanged from preretrofit
use, although an operation in the Southwest
disclosed that its aircraft has performed two round-theworld
trips since conversion; one eastbound, the other
westbound. The major difference is that operators say
they now can do nonstop flights from the Midwest or
Southwest to either coast, cruising at FL 370 to 410
and speeds of Mach 0.76 to 0.80, and arriving at their
destinations with ample reserves.
Prior to retrofit those same trips most commonly were
flown at FL 310 to 370 and speeds of Mach 0.74 or
less with intermediate fuel stops required in the event of
adverse weather or ATC delays. And even under the
best of circumstances, arrival at destination airports
with remaining fuel well below NBAA-recommended
reserves was not infrequent, it was reported.
On the question of improved economy, an operator
who makes flights regularly from the Northeast United
States to Oklahoma with late model Falcon 20Fs
revealed that before the retrofit those trips consumed
about 7,000 pounds of fuel. Since installation of the
Garrett TFE731-5As, fuel burn has averaged 4,000
pounds for the same trip, he said. In a similar vein,
other respondents agreed that the retrofit has transformed
the standard Falcon 20 from a three-hour-andyou’d-better-be-aimed-at-a-fuel-farm
ulcer stimulator
into an honest, 4.5-hour-range aircraft, with the larger
fuel capacity F model reaching a comfortable fivehour-plus
range.
Utilization rates among those interviewed indicate
that their 731 Falcon 20s serve as corporate workhorses.
Configured for eight or nine passengers (10 in at
least three cases), overall average load factors in
excess of 50 percent were reported. And annual flight
hours, ranging individually from slightly over 300 to
more than 600 per aircraft, showed a group average
of just under 500 hours per year.
Features of the 731 Falcon 20 cited as best-liked
were its increased range, speed, climb capability,
quietness of operation, cockpit roominess, general handling
characteristics, and improved altitude and trip
length flexibility. From the maintenance view, three A&P
technicians added to those attributes the lower manhour
requirements, better accessibility and reduced
costs associated with the TFE731 powerplants.
Asked to explain their company’s primary motivations
for retrofitting the Falcon 20 rather than choosing a
new production aircraft, most operators indicated that
they regarded the airframe as the most ideally suited to
their needs and capable of many more years of safe
operation. Some indicated that with engines nearing
major overhaul, maintenance costs had become unacceptably
high. And with the CF700 now out of production,
spare parts and adequate support were becoming
increasingly dear.
Some looked at the retrofit as an investment that will
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greatly enhance the market
value of the aircraft. For
many, the decision was predicated
on economy and perceived
safety with, as one
operator has documented, a
32 percent reduction in fuel
consumption and a 50 percent
increase in range. Additional
fuel for ATC holding was also
a major plus.
Leading the list of least-liked
aspects of the retrofit was lack
of adequate airflow in the aircraft.
Even though the volume
of air produced by the Garrett
engines far surpasses that of
the GE fanjets, this was the
most common complaint heard
and one that still may have not
been resolved to the operators’
satisfaction. Some
attributed the problem to passenger
compartment outfitting
design; others blamed retrofit
engineering that failed to consider
the diversity of approved APU installations. But
most faulted the pressure regulator valves that were part
of the conversion. Acknowledging that the problem initially
may not have been given the attention it deserved,
a Garrett marketer disclosed that a new PRV design has
been introduced to the field that is expected to eliminate
major airflow deficiencies.
Several operators also noted that the added retrofit
engine and thrust reverser weight (about 454 pounds)
and further aft placement of the engines resulted in an
uncomfortably tail-heavy characteristic, especially in the
F model with its rear fuel feeder tanks. As part of the
conversion, Garrett designed a nosetip ballast arrangement
to offset that tendency. Incorporation of Duncan
Aviation’s main battery relocation and aft baggage
compartment STCs also were found to restore a normal
CG range, some operators reported.
Others noted what they considered a lack of
hydraulic pressure at slow speeds, which had not been
present in the CF700-powered Falcon; the high bypass
turbofan engine’s relatively impaired performance at
ISA-plus; and what they regarded as derogated differences
in deployment and vibration characteristics of the
Dee Howard thrust reversers, as compared to the
Aeronca TRs installed on the Falcon 20. But several of
these operators acknowledged that they may still be in
an “unlearning curve” in disassociating the 731 Falcon
20 from its non-altered predecessor.
SELECTED DIFFERENCES 731 FJ20/FJ20B
Garrett General Aviation Services Division provides this list of “differences” between the
731 Falcon 20 and the 731 Falcon 20B. The differences, of course, are due to the
installation of Garrett TFE73-5B engines. All figures are based on the F-model. Garrett
says changes for other Falcon models are similar.
CERTIFICATION DIFFERENCES
731 Falcon 20 731 Falcon 20B
Thrust/Engine 4,500 lb ea. 4,750 lb ea.
Basic Operating Weight 18,250 lb 18,275 lb
VMCA 103 KCAS 106 KCAS
PERFORMANCE DIFFERENCES
Balanced Field Length
(2,000ft, 30°C, 27,000 lb GTOW) 7,050 ft 5,750 ft
Maximum Takeoff Gross Weight
(2,000 ft., 30°C} 27,250 lb 28,100 lb
Time to 39,000 ft.
(lSA, FL 390, 26,000 lb, LRC) 34 min. 27 min.
Cruise Fuel Flow/Engine
(ISA, FL 390,26,000 lb, LRC) 686 lb/hr 669 lb/hr
A number of operators complained that they had discerned
cockpit instrument inaccuracies following the
retrofit. One noted that throttle positions in his airplane
were different from those in the original Falcon 20 and
the gear warning switch had not been revised to conform
with the new positions. Consequently, when he
pulled the power back and did not have the landing
gear down, a red light and audio warning were actuated,
even during cruise.
Another operator remarked that a source of annoyance
for him was a variance between air temperature
cockpit instruments and the temperatures seen by the
TFE731’s DEECS (digital electronic engine control system).
He said his mechanics had complained that to
accurately set the latter, the aircraft had to be faced
directly into the wind and even then the system senses
only immediate ambient air temperature, which may
differ from that registered by visual instruments. In discussing
the problem with Garrett technicians, however,
this operator said he has been told that the company
has developed but not yet fielded a modification that
will enable the flightcrew to see the precise temperature
the DEECS is sensing.
Several operators—including some who indicated
they do not plan to “reretrofit” to the more powerful
TFE731-5B configuration—maintained that the -5A
affords insufficient power to accommodate the aircraft’s
increased allowable gross weight. A few felt that hot
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Most said the Falcon 20
had been part of their
company fleets prior
to retrofit.
system than did the GE engines, some operators reported
chafing of wing leading edge components and the
rupture of bleed air pressure tubing. Garrett coordinated
with Dassault the issuance of service instructions calling
for an increase in component gap tolerances to
allow for heat expansion and provide for more effective
anti-ice pressure hoses.
With regard to the reported lack of adequate internal
air flow, the problem reportedly did not evolve with the
731 Falcon 20, but has been inherent in the aircraft
itself since initial production. It is being investigated on
several fronts, retrofit representatives claim.
Garrett also is continuing to examine all ducting,
restrictors and related hardware to ensure that maximum
heating or cooling air will be directed to where it
is intended, B/CA was told. And new PRV valves also
have been developed which have an expanded calibration
range which increases air flow pressure from
29.5 psig to 38.5 psig at sea level and from 12.5 psig
to 22 psig at 40,000 feet msl, it was disclosed.
In the case of the different throttle position resulting
from the retrofit, Garrett pointed out that “the TFE731 is
so fuel efficient that the throttle can be pulled back far
enough to get landing gear warnings” but Garrett has
worked with Falcon Jet Corporation to develop an FJC
service bulletin that inhibits the warnings when the aircraft
is flying at or above 160 KIAS.
Both Garrett and Dassault have looked at the matter of
increasing the airplane’s speed during climb, and
according to officials, engineers believe that this could be
accomplished. But the penalty in added cost and possible
compromises in other flight parameters led to the conclusion
that it would not be economically feasible.
With the foresight to have begun studying aging aircraft
back in 1973, Dassault has conducted continuing
in-depth inspections of the Falcon 20 series. Determinations
concerning its structural integrity led to approval of
extended maintenance intervals in 1989. The company’s
cumulative findings also show that there is no reason
why the aircraft should not be expected to enjoy at
least another 20 years of useful life. That is why Garrett
believes the 731 Falcon 20 may live to become its most
successful retrofit ever. B/CA
day takeoff performance is not as good as it was with
the CF700. One commented that while his airplane
climbed well to 20,000 feet, it faded rapidly above
30,000. Another reported that during operations in the
Northeast Corridor he is frequently asked by ATC to
climb out at 300 KIAS, “but above 270 knots it just
won’t climb.”
Conversely, another operator said that the climb performance
of his retrofit defies comparison to its predecessor.
So impressed is he with his newfound ability to
go direct to FL 370 and cruise at FL 410, he believes
Garrett should recertify the 731 Falcon 20 to a service
ceiling of at least 43,000 feet.
From the standpoint of product support, virtually every
operator contacted gave Garrett high marks. In one
case, in which a customer claimed that two of four
engines were showing excessive metal content in spectrometric
oil analysis samples, the operator concluded
that “even though Garrett [technicians] may not agree
that you have a problem, they listen to you and give
you some response.” Several operators concurred with
this assessment.
In addition to Garrett, which has its facility in Springfield,
Illinois, Falcon Jet conducts the engine retrofit program
at its Little Rock, Arkansas completion center.
Falcon Jet’s support efforts were less highly regarded
than Garrett’s, as were those of its parent, Dassault.
But many operators acknowledged that may be a
reflection of how participants in the retrofit program
perceive their respective roles. While the focus of Dassault
and Falcon Jet is primarily on new aircraft production,
sales and service, they rationalize, Garrett’s target
is the marketing and support of its engines and APUs
(and avionics products of its sister Allied-Signal divisions)
in whatever application.
Garrett retrofit program representatives indicated that
they have worked hard to cultivate customer confidence
and are putting even more effort into that task as the
731 Falcon 20B order backlog continues to grow. As
one example of that, they point to the initiative taken to
help resolve an anti-ice system problem of which only a
few operators in the survey group seemed to be aware.
Because the TFE731 turbofans provide greater volumes
of bleed air at higher temperatures to the anti-ice
COPYRIGHT 1995 THE MCGRAW-HILL COMPANIES, INC. ALL RIGHTS RESERVED