as far back as I can remember, I have always been fascinated by piston engined, propeller driven aircraft. When I was a child,
the "Jet Age" was also just beginning; however, my love was for planes with the whirring propellers and the sound and smell
of large radial or in-line engines. Military aircraft like P-38 Lightnings, P-51 Mustangs, B-25 Mitchells, and B-26 Invaders
were favorites, while airline Douglas DC' s, Constellations, and Stratocruisers filled my dreams.
I grew up, my room filled with posters, photos, magazines, and plastic models that my dad and I collected. In the late 50's,
I became aware of a variety of ex-military aircraft that had been converted into executive transports. Two of these, both
modified B-26 Invaders, were to become the focal point of my interest. They were the L.B.Smith, Tempo II from Miami Florida,
and the On Mark Marksman, rebuilt near where I lived. These two aircraft are the subject of this modeling exercise.
grew up in Sherman Oaks, a community in the San Fernando Valley area of Los Angeles, just nine and a half miles south east
of the Van Nuys airport. At age 14, I was permitted to bicycle out to the Van Nuys airport, and along with my lifelong best
friend, began exploring the wonders on the field. We would check out the various aircraft parked on the ramp, and watch the
planes come and go for hours at a time.
one of those trips I discovered On Mark Engineering Company. Their main function at the time was to convert into executive
transports, service, and maintain B-26 Invaders. I contacted their offices requesting drawings and photos in order to build
an accurate model of a Marksman. I was introduced to the sales manager, a Mr. William (Bill) Boone, and he provided all that
I requested, and gave me full access to their facility at any time. The model was based on the Monogram 1:48 scale "Speedee
Built" B-26 Invader kit ( primary balsa airframe with plastic parts for the difficult shapes ). During many of my visits to
On Mark, I observed the conversion of a Boeing Stratocruiser into the first "Pregnant Guppy" for Aero Space Lines, and the
modifications, and the return from the first flight of the prototype YB-26K Counter Invader ( # 35634 ), as well as many examples
their main product.
of my last to you I mentioned On Mark as a "cornerstone" ( #1 ) in my life. I will share with you the other
- Los Angeles Trade Technical College, Aircraft Annex, Supelveda Blvd. @ 96th Street - '64 ~ '66. The how and why they work.
Aircraft at site included a B-23 Dragon executive conversion operated by General Electric, and a Kelsey Hayes modified
B-25J Mitchell to a TB 25N, executive conversion operated by an oil company in the Gulf Coast area of Texas until
an inspection revealed inter-granular corrosion with the main spar. I was on the team that got it operational and did some
run-ups and rigging exercises on it.
- U.S. Army - Air Traffic Controller - '66 ~ ''69. Getting them away and back down again. Bayreuth, W. Germany controlling
"Creek-Lark" boarder surveillance flights, then to Long Binh ( S. ) Vietnam controlling traffic alternating between
the Long Binh Army Airfield and the "Head Shed" Pad at USARV Headquarters, then running V.I.P. flight operations out of a
air-conditioned 55' trailer along side of the pad at USARV for the last 7 months. Accumulated almost 50 hours in UH-1D
/ H's and OH-6A's ( 25+ and 23+ hrs respectively ) and had a few interesting experiences. ( Do you know about ACTV [
Army Concept Team Vietnam ], or that Air America pilots flying into Long Binh wore white shirts with blue shoulder boards
but used military call-signs for their aircraft, and when I asked the airfield commander who these guys were I was told not
to pursue my query but to clear them as requested.
- Ted Smith Aircraft - May '69 ~ November '69. Manufacturing and Flow Tech.. The how they went together from just parts and
pieces through to roll-out and delivery. Talked with Mr. Smith on a number of occasions and he was like Santa without the
facial hair and the red suit. A wonderful man. His Aero Commander 560 ( kept there at the plant ) was still his favorite.
the On Mark closure, many of those details are a bit obscure. My access was terminated before the contract signing for the
40 Counter Invaders, B-26K project late in 1963. In that same timeframe came the U.S. Government/CIA contract to build the
two “ Special Purpose “ Marksman conversions, eventually known as the Blue Goose. A guard shack was placed at
the entrance to the On Mark facility right at the north end of Hayvenhurst Avenue to control access. That was in late March,
early April, if memory serves. I had called Bill Boone to run my nearly completed Marksman model out for final inspection
prior to application of the finishing touches, and he sadly informed me that he could no longer grant access and that the
model was no longer necessary ( he was going to use it as a sales tool/display model ). I rode my bicycle out to Van Nuys
and On Mark anyway, discovering the closed gate and guarded entrance. Later in ‘63, On Mark
built the Super Guppy ( the base Stratocruiser aircraft can be seen in the distance behind the underwing turning away shot
of the YB-26K ), however, other than the Special purpose Marksman Blue Goose twins and the 40 Counter Invaders, that marked
the end of their civil conversions to my knowledge.
details presented by Mark Reynosa in his history of Van Nuys and On Mark, he indicates that Volpar utilized the site from
the early ‘70s on through the hangar teardown in the mid-‘80s. Interestingly, Volpar created the Beech 18s using
turbine power used by Air America, especially as flown out of their Udorn RTAFB base in Thailand. Coincidently, that same
timeframe is when the Blue Goose was there at Udorn ! CIA, Air America, On Mark, Volpar, B-26K/A-26A, Blue Goose, Turbo 18s,
all seem to be separate slices of the same pie to me ! They didn’t call it the “ Secret War “ for nothing.
am open to contact at all times from anyone that can share their knowledge and experiences at On Mark and enjoy sharing my
Mark Engineering Company, Van Nuys, California
Mark's civil conversions were called Marketeers with an extended more tapered nose, but otherwise relatively unchanged fuselage
profile, and the pressurized Marksman series. In all of the On Mark conversions, the rear wing spar carry-through structure
was replaced by a patented design, structural circumferential ring.
strengthened wings were mounted in the same position as with the original carry-through spar. The forward wing spar was not
altered because of On Mark's desire to maintain the layout, proportions, and flying qualities of the original Invader design.
This resulted in the crew inconvenienced by having to enter the flight deck through a duck-under along the right side of the
cabin beneath the forward spar. By opening up the fuselage interior space, removing as many of the bulkheads and partitions
as possible ( including the rear wing spar carry-through ), installing large cabin windows, entry stairs in fold down doors
( Airstairs ), airliner style interiors with custom seating to accommodate six or more passengers, these aircraft were at
the apex of personalized, piston engined, executive transports.
were made on almost a production line basis, and their popularity continued until the early 1960s, when purpose-built executive
types and corporate jets started to become available. I have accounted for 29 Marketeer, and 8 Marksman conversions.
Mark suspended, then terminated all civil conversions when awarded the contract to re-manufacture 40 Invaders to the B-26K
standards in 1964. By that time, six of the Marksman conversions had been completed for civilian customers. The seventh and
eighth Marksman modifications were done after my access was ended in 1963.
have found information that these were a special purpose version designed for and delivered to CIA associated companies. I
understand that these were flown in South East Asia, with terrain-following radar and equipped for air-drops.
Mark, Marksman C:
ultimate On Mark conversion was the pressurized Marksman C. The highly modified
fuselage used DC-6B heated windshield, cockpit, and cabin side windows ( these were "off-the-shelf" Douglas components designed
for pressurization ), while the increased interior height and the rear ring-type spar provided for a full length, stand erect
cabin. In addition to the pressurization, passenger comfort was improved with soundproofing and airconditioning. New
cockpit layouts included dual controls, upgraded radio/navigation equipment, and
radar. The extended more sharply tapered fiberglass nose unit incorporated an internal baggage compartment accessed through
a side mounted door with fold out ladder.
equipment included deicing, extra fuel tankage, wingtip tanks, increased chord metal skinned rudder with trim and booster
tabs, and vortex generator veins were installed on the vertical tail. The Marksman C was powered by 2,500 hp R-2800-CB17 radials
with Hamilton Standard broad chord, reversible pitch propellers. Anti-skid brakes were standard. The base price of the Marksman
A was around $260,000, to around $365.000 for a Marksman C, in 1962.
L.B. Smith Company, Miami, Florida Smith, Tempo II:
The other executive conversion was developed from the B-26 Invader using a new pressurised fuselage, which
was 9 ft 7 1/2 in (2.93 m) longer than the standard. The standard wings were mounted some 20 inches further outboard on each
side to ring type spar structures, opening up the cabin interior for a stand erect walk through length of nearly 28 feet,
and able to seat up to 13 passengers. With the R-2800 C series engines extended almost two feet further outboard, engine out
asymmetrical thrust dictated lengthening the fuselage, repositioning the tail further aft to maintain rudder effectiveness.
This accounted for much of the added length, the rest came from an extended nose to bring the center of gravity ( C.G.) into
correct position. With the wingtip tanks, and the new fuselage, I feel that the Tempo II was the most attractive of the Invader
However, since the airplane was so radically altered, I was informed that it lost the excellent flying
qualities of the original. In fact, N4204A was destroyed March 2, 1980, while being flown by the University of Nevada conducting
airframe icing research, in a stall-spin incident. ( Reference: NTSB Identification: LAX80FA060 ) It must be noted, however,
that the airplane was operated successfully by the University from 1968 to when it was lost. I have only found records for
two Tempo II conversions.
By Richard E. Fulwiler