Douglas A/B-26 Invader

Richard E. Fulwiler

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Page 1. On Mark Engineering Co.- A pictorial feast


Richard is working on 1:48 scale models of the Invader to represent the LB Smith Tempo II, N4204A, as used by the Univ. of Nevada and an On Mark Marksman C. Kit bashing from 4 Monogram B-26 kits
Richard goes on:
The following is what I put together to describe what the project is all about. The intention is to submit it to Fine Scale Modeler magazine when the Tempo II and Marksman C models are completed. The magazine is more concerned with the construction process, rather than the historical background. I'm really stuck on the history and my personal involvement with On Mark.
Model Project - Douglas A-26 / B-26 Invader Conversions
From 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.
As 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.
I 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.
On 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.
Richard also wrote:
One of my last to you I mentioned On Mark as a "cornerstone" ( #1 ) in my life. I will share with you the other three.

#2 - 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. 

#3 - 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.

#4 - 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.
Concerning 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.
From 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.
I am open to contact at all times from anyone that can share their knowledge and experiences at On Mark and enjoy sharing my own.
On Mark Engineering Company, Van Nuys, California
On 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.
The 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.
Conversions 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.
On 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.
I 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.
On Mark, Marksman C:

The 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.

Additional 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 conversions.
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





Heard a Pretty reliable rumour, that an On Mark Marksman is being fully restored to possibly race at Reno, so I asked Richard if he could knock me up something to resemble what she might look like, so he sent me couple of tasters of his initial draft. 
She will have a couple of HUGE lumps ( Wright's) to drive her round the course...Watch out Rare Bear.

One of Richard E. Fulwiler's incredibly detailed models 





Some of Richards Illustrations



Relating to the below Ilustrations,
The second Marksman, N827W, as she appeared in mid-July 1961 ( Wheaton Glass if information is correct ) along with N100Y at Carl Spaatz Field, Reading Pennsylvania. The drawings have as usual both inboard and outboard, port and starboard profiles.
There are many fuselage details hidden in the side view ( profile ) because of the engine cowls and nacelles that I have worked diligently to include correctly. I feel this is important to show the window, Airstair, scoops and vent positions that cannot be seen otherwise. The starboard footwell windows on the On Marks is of note as they are hidden by those nacelles, and on N827W, the unique paint scheme on the fuselage. I was asked by a fellow modeler about those footwell windows as to their size and placement. Notice that I located the wing spar attach points on the grey fairing base to give additional reference.