On Mark Marksman ZS-CVD in the early 1970s
On Mark Marksman - The Truth ? This narrative is an attempt to outline the true story of the On Mark Marksman, a civil conversion of the Douglas A-26 Invader. Unfortunately, most published online and written accounts of the Marksman and other A-26 conversions have contained many errors that continue to be repeated and 'written into history'. On Mark Engineering engaged in maintenance and conversion of A-26s for civil and military customers from 1954 to mid-1970s, and was based at Van Nuys airport. Initial A-26 conversions included :- removal of military equipment and replacement with fairings and civil avionics, deactivation of bomb bay doors to permit carriage of passengers, soundproofing, additional cabin windows, replacement of the small 'gunner's hatch' with a larger retractable entrance door in the 'bomb bay' or aft of the starboard wing root, baggage provision in the nose section, metal cockpit roof panels, improved brake systems, improved and expanded fuel systems, uprated engines, reversible-pitch propellers, etc. By about 1957, On Mark had developed a major modification that replaced the 'carry-through' section of the rear wing spar with a circumferential steel 'ring spar' that freed the fuselage space for better passenger accommodation and cockpit access. Other major improvements included a broad-chord metal-skinned rudder, DC-6 wheels and brakes, APU, autopilot, co-pilot controls, additional internal wing fuel tanks and wing tip fuel tanks. An extended glass-fibre nose for baggage and/or radar was described as the 103" nose, being the length of the removable section forward of fuselage station zero (Stn.0), that increased the overall length by about 26" more than an A-26C. The typical package of optional improvements was then becoming standardised, and that was promoted as the On Mark 'Executive'. The full options package was embodied in one aircraft used for development that became registered as N40Y and re-named as the 'Marketeer' in about 1957. By 1960 On Mark was developing the concept further into what then became the 'Marksman'. That added the major feature of full pressurization that was not possible with minor changes to the A-26 fuselage structure and outward-opening pilot access hatches. Flat glass windscreens and cockpit side windows, as designed for Douglas DC-6 and DC-7 airliners, replaced the curved acrylic panels of the A-26, and a replacement fuselage roof structure was added from the new windscreens back to the fin to provide a relatively continuous headroom of about 6ft. The fuselage structure remained largely intact, as did most other A-26 conversions - only the Tempo II had a largely new structure. The first Marksman first flew as such in January 1961, registered N100Y. Unfortunately, publicity materials included a retouched photo of Marketeer N706ME, and included loose 'proposals' of so-called 'Marksman A', 'Marksman B' and 'Marksman C' versions that were really just the usual major engine and fuel tank options already offered on the Marketeer. Passenger accommodation was probably no more than eight at absolute maximum, unlike many wild claims for various A-26 conversions. By 1964, six Marksman conversions had been carried out for civil customers, the final seventh and eighth being of a special version with terrain-following radar for air-drops, designed by and delivered to CIA-associated companies. See below for the eight A-26s converted to Marksman specs, listed in sequence of conversion :- 18607 43-22416 N1394N # N100Y N140Y N190Y N40XY 27805 44-34526 N9178Z # N827W CF-OFO N551EH N400V N7977 N26AB 28040 44-34761 N67158 N400E # N400E N60XY N60XX 29149 44-35870 N1471V N320 # N320 N99426 27846 44-34567 N9412Z # ZS-CVD 6934 41-39221 N9636C # N3035S N256H N26GT 27694 44-34415 N5002X # N900V N46598 28977 44-35698 N5001X # N800V N58071 N67623 # shows when the conversion occurred in the time line of each airframe. Note that some aircraft, eg N400E and N320, were progressively converted first to Executive, then to Marketeer, finally to Marksman specifications. N26AB and N26GT survive intact, ZS-CVD and N99426 are dismantled. Of others, N1242/N919P, N1243/N9150/N26BK, N61B/N161Q, N67160, N600WB never were Marksman conversions. ------ General A-26 Invader Bibliography. - Douglas A-26 and B-26 Invader, by Scott Thompson, 2002. Douglas A-26 Invader, by Frederick A Johnsen, Warbird Tech Vol.22, 1999. Foreign Invaders ..., by Dan Hagedorn and Leif Hellstrom, 1994. US Civil Aircraft Register, various editions 1963-1982. Air-Britain Digest, article Civil Invaders by Rod Simpson, Summer 2001. Warbirds Directory, by Geoff Goodall, 2002. Le Trait d'Union, No.229, article by Bernard Chenel, Sept-Oct 2006. McDonnell Douglas Aircraft Since 1920, by Rene Francillon, 1979. The Aircraft of the World, by Green and Pollinger, 3rd Edition, 1965. Jane's All The World's Aircraft, 1957-58, 1958-1959, 1959-60, 1960-61, 1961-62, 1962-63, 1963-64, 1964-65, 1965-66, 1966-67, 1967-68, 1968-69, 1969-70, 1970-1971. International Air Power Review, article by David Willis, Summer 2006. Bombing Twins - Allied Medium Bombers, by Michael O'Leary, 1994. Central American and Caribbean Air Forces, by Dan Hagedorn. FAA electronic files for selected airframes. ------ Heston Branch Home Page Photo page 1 Photo page 2 Photo page 3 Photo page 4 Photo page 5 Air-Britain web site Heston branch feedback This text updated 2008.02.17