Douglas A/B-26 Invader

Development - Civil

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Since 1945, over 300 A-26s have been entered on to the FAA US Civil Aircraft Register.

Perhaps up to a hundred of those were probably only registered for ferry flights from USAF bases such as Davis-Monthan AFB, AZ and Hill AFB, UT to civil airports and stored as candidates for sale on the civil or overseas military markets.

The initial main civil uses were as "executive" personnel transports with minimal modifications such as removal of military features, bomb bay doors sealed shut, passenger entry stairs in bomb bay, and the conversion of the fuselage to accept six to eight passengers.

Improvements developed considerably until the early 1960s, when purpose-built executive types such as the (turboprop) Gulfstream started to become available. During the mid-1950s, A-26's were tested and used as air tankers for suppression of forest and wildland fires, and may have briefly used borate based retardants, hence the inaccurate and unofficial term "borate bombers." Borate was soon discontinued due to its undesirable ecologic effects, replaced with retardant mixtures of water, clays, fertilizers and red dyes. That use of A-26s on USDA contracts was discontinued in major regions by about 1973, when many of the A-26 air tankers then found willing purchasers in Canada. Much early development of conversions was carried out by Grand Central Aircraft, whose drawings and personnel were taken up by the On Mark Engineering Company of Van Nuys, California from about 1955. By the 1960s, On Mark had obtained an exclusive licence from Douglas Aircraft Company for manufacture and sale of parts for A-26s. The On Mark Executive (1956), the On Mark Marketeer (1957), and the more radical pressurized On Mark Marksman (1961) were products of this effort.

The next most significant conversion was the Rock Island Monarch 26, while less numerous and more basic conversions were carried out by Wold Engineering and R. G. LeTourneau Inc.


There were several other smaller ( aviation related ) companies that undertook modifications to the Invader, one of these being Stahmann Farms of Las Cruces NM.
It modified and converted 44-34524 ( N558, N58Y and HK-999E ) and was a one-off, modified in 1959/60, for extra long-range using a Marksmans wing with tip tanks and flew from Minnesota to Prestwick, with routing from Madrid to Iceland.
Spares for this aircraft were salvaged from an unidentified Marksman badly damaged by fire at Phoenix AZ.
It actually looked like a Marketeer but was not and is an airframe that has caused some confusion over the years.
There is evidence that Stahmann Farmes Inc, also undertook modification work for Rock Island, to upgrade Invaders to the Monarch 26 and was possibly involved in Air tanker conversions in order to maintain their vast operating portfolio of farming.
Stahmann Farms Inc. Las Cruces, NM. used Harpoon N6655D (15-1600) between 1961 - 1984 for frost control flights over Stahmann's 4000 acre (16188 hectares) pecan nut plantation in New Mexico. The aircraft would be dispatched usually between 3 and 4 a.m and would be directed from the ground to areas that were in danger of freezing. It was flown at between 75-100ft (22.8-30.4m) above tree top level to deflect the warmer air downwards. To increase the down wash the aircraft was flown with its spray tanks full of water. This aircraft was to have been converted to a long range transport for Dean Stahmann and his family to transport them to Peru in case of war - this was at the time of the Cuban Missile Crisis. However, there was the possibility of a proprietary conflict with the Howard 500 and therefore Stahmann chose a A-26B for this role.

Grand Central Aircraft Company


Lockheed Air Service (LAS)

On Mark Engineering

Rhodes Berry

Rock Island Oil & Refining Co.

Slick Airways

L.B. Smith Aircraft

Wold Corp.

NOTE: Hamilton Aircraft

In 1966, wing spar cracks had started to show up in some of the FAB's (Brazilian Air force) Invaders.

In an attempt to prolong their service lives, in 1968, several FAB Invaders were flown back to Tucson, Arizona for an upgrading by the Hamilton aircraft Company. Most of the changes involved IRAN (Inspect and Repair as Necessary) of avionics, communications equipment and weapons systems.

15 aircraft were refurbished. In addition, three new aircraft (FAB serials 5173/5175) were acquired by Hamilton from surplus stocks as attrition replacements.

Unfortunately, one of the FAB B-26 was so badly corroded that it had to be struck off in Arizona and replaced by another.

In addition, a civilian B-26 ( Ex- LeTourneau ) was impounded by the Brazilian government in June of 1966 due to its involvement in illegal smuggling activities. It sat derelict at Brasilia until 1970, when the FAB finally took it on charge and used it as a transport aircraft under the FAB serial number of 5176.

In spite of the Hamilton rebuild program, wing spar cracks began to reappear in the wings of many FAB B-26s in 1972, which led to the decision to retire the B-26 from FAB service rather than to attempt to keep them in the air for much longer. The withdrawal took place in stages, beginning in 1973 and lasting until December of 1975.