This gives the background as to why all those Stearmans and TBM Avengers came to New Brunswick in the first place, starting in 1952.
I have added two articles at the end of this page that came from the Forest Protection Limited files:
- 1) “Progression towards smaller spray blocks in New Brunswick” (H.J. Irving 1985), and
- 2) “Early TBM use in N.B. by Forest Protection Limited” (Don Henry 2008).
[Edward G. Kettela Commentary – 1980s. Edited by C. Adam. Ed Kettela is a retired federal Research Scientist at the Canadian Forest Service – Atlantic Forestry Centre, Fredericton, New Brunswick.]
The spruce budworm in eastern North America is without doubt the most destructive and important insect that inhabits the forests of Eastern Canada and the United States. Infestations of this insect erupt to levels that can kill large tracts of forest land and its constituent trees, balsam fir and the spruces. The occurrence of spruce budworm outbreaks are probably among the most natural biological phenomena to occur in the forest.
In the early 1950s there was no real way to protect the forest from insect pests. It was (1) the production of large numbers of aircraft during World War II and the post-war period and the subsequent availability of these types of aircraft to the commercial sector and (2) the advent of easy-to-use chemical pesticides, namely DDT, that contributed to a total shift over about a thirty-year period in the forest industry.
Historical infestations. Spruce budworm infestations have been recorded and documented as far back as the late 1700s. The infestation at the turn of the last century, from 1910 through 1918, was certainly much better documented than the previous infestations. This one died down by 1924 and then the next one started to rise in the late 1940s. By the time the New Brunswick forest industries realized what was happening to the trees, the infestation had already been active for some four to five years, albeit, mostly in the northern half of the province.
In the early 1940’s, the spruce budworm had made its appearance again in Western Quebec and Ontario. Government agencies were concerned about the growing budworm threat, and early experiments brought governments together with private companies. The most extensive experiment was the spraying of 64,000 acres in the Lake Nipigon area of Ontario in 1945 with DDT at one pound per acre. In the United States, the states of Oregon and Washington initiated a large-scale spraying program in 1949. [FPL unpublished report]
1951, 1952 and Forest Protection Limited. By 1950 it was evident to foresters and to entomologists that the budworm infestation was well underway in the northern part of New Brunswick and that serious damage was being sustained. Insecticide was also inexpensive, easy to formulate, and for the first time, easy to apply from large numbers of surplus aircraft.
The forest industry, not government, was the initiator of the forest protection operation that lasted to the 1980s in New Brunswick. An operation to spray some 182,000 acres (293,000 hectares) of forest land in north-central New Brunswick was planned for 1952. That meant considerable amount of planning in 1951, the definition of sites, and where to build an airstrip, for at that time New Brunswick was a wall-to-wall forest, unlike today, where it is broken up by numerous harvesting blocks and plantations resulting from their reforesting.
By 1952, large patches of forest in the northern part of the province were grey, i.e., they had been completely denuded. DDT was sprayed in the US, so that is what we did here in Canada: DDT killed spruce budworm wonderfully well.
Forest Protection Limited was formed in 1952, and still operates today (2014). FPL was a company established as a non-profit organization by the Province and the forest industry to work as their agents to carry out spruce budworm forest protection spraying operations.
1956 – The Big Moth Fallout. There was an extraordinarily large invasion of spruce budworm moths in Campbellton, N.B., on the nights of August 6 and 7, 1956. The moths were deposited following the decay of a convective storm at 2400 h.
Stearmans vs. TBMs. Plans were laid for larger operations and thus more aircraft. Many new airstrips were built, which is an engineering feat in itself over the time frame from 1952 through 1957. The type of aircraft used exclusively in the early days was the Stearman, a bi-plane equipped with boom and nozzle equipment.
In the very early days of spraying with the Stearman aircraft, the actual mode of operations changed very quickly over a three-to-four-year period. Initially pilots were given a photograph, then loaded up and were told to spray on the patch of ground. Later developments established much more control over where spray pilots took their load. The development of the pointer and buddy system of spraying was initially from a safety point of view but then made spray operations more efficient, at least in getting the material out in an orderly fashion. The lining of spray blocks and the development of the aerial pointer system all took place during the later half of the fifties. The largest operation ever tried during the fifties in New Brunswick was in 1957 when 200 Stearman aircraft were employed.
At that time the ‘‘Feds’’ had the Job of evaluating TBM performance compared to Stearmans, and apparently there was not much difference. It was thought because TBMs were bigger and faster that they would miss everything, and I think in the long run it was just the complete opposite. This in itself was a turning point, for the TBM was a larger aircraft with a larger payload that could spray more efficiently, and theoretically would result in the need for fewer aircraft.
|Type||Single engine two place biplane trainer||Single engine low wing monoplane bomber|
|Construction||Fabric cover on wooden wings and metal fuselage||All metal|
|Wing span||33 ft.||52 ft.|
|Original engine||225 H.P. Continental||1900 Wright|
|Present engine||450 P. & W. Wasp Jr.||1900 Wright|
|Fuel consumption||20 g.p.h.||80 g.p.h.|
|Speed – cruising||100 m.p.h.||180 m.p.h.|
|Speed – spraying||90-100 m.p.h.||150-160 m.p.h.|
|All up weight||3,600-4,000 lbs.||18,000 lbs.|
|Runway length to get airborne||1,500 + ft.||2,500 + ft.|
|Endurance||2 hrs.||4 hrs.|
|Crew||one pilot seated in rear open cockpit||one pilot seated in closed canopying high, forward of wing, position|
|Tank location||Forward cockpit space||Belly|
|Useful load of insecticide||150 US gal.||700 US gal.|
|Spraying||Boom type, pressure applied by outside wind driven pump||Boom type, pressure from a/c hydraulic system|
|Swath width – two aircraft||Up to 400 ft.||Up to 900 ft.|
1957 to 1959. By 1957, the budworm infestation had started to subside. In 1958 the operation size was considerably reduced over that of 1957 and reflected a downturn in budworm populations. TBMs were first used to spray budworm in New Brunswick in 1958. (See below for more on the 1958 season.) In 1959 the infestation had dropped so much lower that no spraying operations were planned and executed, except for some experimental work. Surveys in the fall of 1959 showed that the infestation had increased again, and Forest Protection Limited was reactivated.
1960 to 1967. Stearman and TBM aircraft were used together in spray operations, not as teams, but certainly they each had their role in the spray operation. In 1968 the Stearman was retired, and from then on the TBM aircraft were the preeminent spraying aircraft used, delivering the largest volume of spray.
The early 1970s. By 1970, it was apparent that the infestation was a full-blown outbreak once again, and that this had all the makings of a very substantial infestation across eastern North America, of which New Brunswick was a part. The surveys from the fall of 1970 indicated that there was a much larger area of infestation but it was not expanding into northern New Brunswick that contained the bulk of the balsam fir in large over-mature forest but into southern New Brunswick.
1975: the first big year. Through survey technology of the day, the extent and the intensity of the infestation had more or less peaked in 1975, and had infested over 150 million hectares of forest land from the Ontario-Manitoba border to and including Newfoundland.
From a forest protection point of view, 1975 was a watershed year for many reasons, notably the acute world shortage of insecticides. Further, it was the year following 1974, which was the first of two years in New Brunswick when virtually every stick of wood in the Province of New Brunswick was defoliated to some degree, which scared the living hell out of the forest industry. This was also in concert with record sales and profits from the forest industry. So 1975 was when there was enough money, there was the will and there was enough insecticide to do an operation on a scale large enough to both impact on the insect and to impact for a year or two to provide quality foliage protection.
1976: the second big year. 1976 saw the happy coincidence of 21 days of unhindered spray weather. Operations in themselves usually are at the whims of weather, whether it is too cold or too foggy or too rainy or too windy and hot, but in 1976 all these things came together and yielded a most remarkable result in terms of foliage protection. It was probably the best foliage protection ever achieved in the province. It was also the one year in which there were a lot of people watching sprayers, because of the increasingly high profile and the fact that we were spraying down in the southern area where a lot of people lived.
Up to the 1980s. By the 1980s, the infestation has gone through a series of rises and falls and, over the last three or four years, had started to approach levels of infestation reminiscent of the early 1960s. During the course of this infestation, at least from 1968 to the 1980s, which I consider to be the hottest infestation ever, and combined with fitful, sporadic and inconsistent protection practices, a terrific amount of the forest of New Brunswick was consigned to the budworm.
The 1958 Season – Program Cutback, but the Avengers arrive
[The following are excerpts from an anonymous internal FPL report about a history of Operation Budworm covering the years 1951 to 1960.]
The spraying program for 1958, the first year that TBM Avengers were used, was cut back to 2,588,000 acres in New Brunswick and 760,700 acres in Quebec.
For the first time, the reliable Stearman no longer comprised the entire spray fleet. In 1958, it was decided to try the Grumman TBM Avenger, a medium torpedo bomber … The Avenger is a much larger plane that the Stearman, with a loaded weight of eight and one-half tons, as against less that two tons for the stearman, and carried 700 gallons of DDT solution as compared with 150 gallons for the Stearman. It could spray a full load in ten minutes. It was hoped that the Avenger would provide a more economical method of application.
Twelve Avengers and seventy-six Stearmans comprised the spraying fleet in 1958. The method of spraying used by the Avengers was quite different from the Stearman technique. Each pair of Avengers sprayed under the tutelage of an inspection pilot, who flew above them and directed their movements by radio. Eighteen Cessna observation planes were on hand for the operations, one for each Avenger and six more to handle the Stearmans.
Once again, Forest Protection Limited formulated its own insecticide at Dalhousie in northern New Brunswick.
The 1958 operations included 850,000 acres of new high hazard forest in York, Carleton and Victoria Counties, to the south and west of previous spraying. This took in considerable faring areas, a different kind of country entirely from the remote bush which had been the scene of previous operations.
Spraying began out of Fredericton on June 1 with the twelve Avengers. They started cautiously, with the weather not very favourable. As soon as Juniper [Airstrip] opened up, four Avengers moved north to that field — although there was some concern as to how the Avenger, which required a much better surface that the Stearman, would handle the Juniper strip.
One Avenger pilot, Thomas Marsten, was killed when his aircraft crashed and burned twenty miles southwest of Juniper, during evening spraying on June 12. It was the second fatal crash in seven years of spraying operations.
The operations were completed successfully at a total cost of $1,557,714 for New Brunswick and $465,390 for Quebec — a cost per acre of $0.61. This figure marked a record low and was less that one-fifth of the per acre cost of the New Brunswick spraying project in 1952.
The State of Maine launched its second budworm spraying program in 1958. A total of 302,000 acres in northeastern Aroostook County [which borders Quebec and New Brunswick] were sprayed … The spraying was carried out by the Simsbury Flying Service of Simsbury, Conn., with a fleet of eight converted torpedo bombers and two Stearmans for use around irregular boundaries, lakes, and streams. Five Cessna observation planes were also on hand. The insecticide — 300,000 gallons of it — was obtained at cost from Forest Protection Limited. It was thus imported into the United States from New Brunswick, although the basic ingredients from which it was mixed came originally from the U.S.! Excellent results were reported, with a 96 per cent reduction of the budworm population.
The Evolution of the Avenger as a Sprayer in New Brunswick – 1964
An interesting article in the May 18, 1964, issue of Aviation Week & Space Technology (under the section Business Flying) titled “Spraying Program Uses New Techniques” (David A. Brown) provides some insight on the early TBM Avengers and their journey from the Royal Canadian Navy to their use as sprayers in New Brunswick. The article reports that 28 Avengers were to spray in New Brunswick in the spring of 1964 to cover about 2 million acres and will be “directed by 18 Cessna 172 and 182 spotter aircraft. Stearman aircraft will be used to cover hard-to-reach areas.” These 28 TBMs were obtained by Canadian operators in 1958 from the Royal Canadian Navy
When the TBMs were introduced in 1958, they flew, as did the Stearmans, in overlapping straight swaths over the contour lines by sight within areas of 4 to 10 square miles at an altitude of 65 to 200 feet. This continued in 1960 when the TBMs were doing half the work. There were no operations in 1959.
In 1961, a “new system of aircraft control” was used to utilize the full potential of the TBM. A team of 4 TBMs and two Cessnas (172’s/182’s) were used, with two TBMs spraying while the other two were reloading. The Cessnas were used as aerial flagmen, “a direct adaptation of the ground flagmen used in agricultural work.”
Barney Flieger wrote in a 1975 internal report to FPL (called Company Organization and Background) that “spraying has been carefully controlled”:
“Spraying is contracted to licensed operators who must work under F.P.L. direction and supervision. Records are kept on all spray sorties, on the basis of which payments are made to contractors. Since 1961 the company has provided a navigation system for sprayers and under this system all spraying operations have been witnessed and recorded.”
The TBMs were contracted directly from the owners. Forest Protection Limited had encouraged their purchase from the Royal Canadian Navy when they were declared surplus in 1958. The Canadian government “had placed a strict interpretation on a U.S. ban on exporting TBMs from the U.S. These aircraft were modified for agricultural work only, which meant that they sat idle for ten months of the year.”
The two operators, Wheeler Airlines of St. Jovite, Quebec, and Skyway Air Services, Ltd., of Langley, British Columbia, maintained and operated the TBMs, supplied the pilots and crews and maintained a “parts pool to ensure against loss of time from breakdowns.” Parts had been available from the Canadian Department of National Defense, but these were now drying up. FPL supplied “the fuel, oil, insecticide and housing for the crew.” Most of the maintenance men were former Royal Canadian Navy mechanics. Half the pilots were Canadian and half American. Wheeler was the prime contractor for the TBMs and Stearmans, including those from other companies; Skyway dealt directly with FPL.
Because of its great experience in spraying forests, FPL was occasionally invited by other provinces and states (mainly Quebec but also Ontario, Newfoundland and Maine) to come to their assistance. “Work of this kind was always on a cost-plus basis and of course was cheap for those who invited F.P.L. to carry it out” (Flieger 1975).
1975 – A Critical Year for the Spruce/Fir Forests of New Brunswick, and 1976
by Don Henry, FPL Operations Coordinator, 1969-1976 inclusive
1975 – The Critical Year
A great year for spruce budworm and a correspondingly poor year for saving the foliage of much of the budworm-infested forest of New Brunswick and especially for the Forest Protection Limited TBM fleet whose only purpose in NB at that time was the forest spraying project.
In the late sixties/early seventies, the conditions were ideal for the rapid spread of spruce budworm in eastern North America; consequently the area of infestation in NB had increased by a large percentage annually, regardless of areas sprayed. Since the spraying operation was designed only to attempt to save trees in moderate and high hazard areas, the surrounding areas of light infestation retained a residual population. This situation, along with invading moth populations, were more that sufficient to repopulate and expand the hazard area in susceptible forest. We seemed to be playing “catch up” or a best were in a holding situation. Records show that the areas treated in the early to mid 1970s reveal this increase in hazard areas:
1973 – 4.55 million acres treated
1974 – 5.9 million acres
1975 – 6.6 million acres
1976 – 9.59 million acres
New Brunswick has some 18 million acres, of which some 75% was susceptible to budworm infestation, an imposing task to attempt a protection program and even more so when the spraying schedule called for two applications three to five days apart.
In 1975 FPL operated several airstrips in south central New Brunswick, with aircraft traditionally starting work in the southernmost airstrips and moving north as per development of the budworm larvae. The spray formulation was effective as a contact as well as an ingested solution, and was applied at the rate of 2 oz/acre per application when two applications were scheduled. This proved to be an adequate dosage for control under ideal application conditions when larvae were in their early feeding stages.
In consequence of the impending increased infestation area in NB, FPL bought 11 TBM Avengers in late 1974 from US companies. Some of these aircraft had worked in NB in previous years and were all equipped for forest spraying. The remaining necessary aircraft were leased from other Canadian companies, with a total fleet of TBM sprayers scheduled for 1975 of 33 aircraft. The 25 light aircraft used for control, supervision, transport, etc., were leased from Canadian companies. The number of aircraft required each year fluctuated as required and corresponded directly to the size of the area to be treated, along with an educated guess as to the ability to fly to the whims of the weather, a decision that has to be made well in advance and with no small amount of optimism.
The year 1975 was certainly unpredictable and proved to be critical when the main objective of the whole operation was to save the foliage of the spruce/fir forest.
The operational system for FPL spraying operations was set up so all information funneled through a field operations headquarters. The Search and Rescue Unit, all aircraft movements between fields, all light aircraft maintenance, all aircraft radio maintenance, as well as personnel movement, flight planning, mail, entomological information on insect development and all spray records — all this information in 1975 funneled through this field headquarters staffed by the Operations Coordinator and a Records Clerk.
As the US-bought aircraft arrived at Fredericton Airport, they were serviced and checked out by contracted personnel, and prior to spraying were ferried to Dunphy Airstrip for calibration for spray emission rate. Here they were joined by the remaining fleet that had flown directly to Dunphy for calibration.
All aircraft were then assigned to teams of three sprayers and two Cessna control aircraft and then to their respective airfields, the control personnel having completed their training in low level navigation, with the Chief Navigator per airstrip having all maps made up prior to departure.
The 1975 Diminishing Airpower Saga
The loss of five TBMs substantially reduced the available working fleet of aircraft for subsequent season, as will be apparent in the type and numbers of spray aircraft available in 1976.
Number 1 – May 8, TBM C-GLEI, BuNo 53307 (FPL), flown by John Inman, developed engine problems on approach to Dunphy
Number 2 – May 20 a.m., TBM CF-BEF, BuNo 53078 (Miramichi Air Services), pilot Biro lost control of his fully loaded aircraft on his initial takeoff on the first day of scheduled spraying from Juniper
Number 3 – May 20 p.m., TBM CF-ZYC, BuNo 53607 (Hicks & Lawrence), flown by Hans Koerfgen, crashed on a test flight
With the loss of three aircraft so early in the season (including two in one day!), the fleet was operationally diminished by nearly 10%, a tough situation to overcome. With the adverse weather conditions in late May, which restricted operational flying along with this loss of aircraft, a critical operational condition evolved, and the decision was made to curtail part of the second application to spray areas. Consequently, of the 6.66 million acres treated, some 1.1 million acres received only one application, a condition that was very evident in the subsequent July Aerial Defoliation Surveys and in the hazard area for the 1976 operational year. 1976 was a very historic year when FPL sprayed some 9.59 million acres, with all two applications as scheduled that year and with adequate air power and more accommodating spray weather conditions.
Number 4 – June 10, TBM CF-IMW, BuNo 85928 (Evergreen Air Services), flown by Dean Kelly, crashed near Chipman Airstrip.
While the loss of this aircraft late in the spray season was unfortunate, the overall operational schedule was not affected appreciably, as the season was about two thirds completed.
Number 5 – July 4, TBM C-GLEG, BuNo 53334 (FPL), flown by Bert Archer, experienced fuel management problems east of Dunphy while on a test flight.
The Larva Spray Program was completed, and several TBMs were being readied for an Adult Budworm Spray Program when GLEG crashed.
1976 – The Great Year
With the forest hazard area in New Brunswick being some 12.2 million acres, the operational planning for 1976 was enormous, almost to the point of being overwhelming in size and logistics.
The Hazard Area calculated by an Aerial Tree Condition survey and the number of Budworm Egg Masses in the area were the general factors that decided where tree protection was required. This information is obtained and recorded in the summer and fall prior to the following spring spray season. The hazard area is defined by several categories from light to extreme, with only the higher categories considered for protection.
The Hazard Area for 1976 (12.2 million acres) was approximately twice that of the previous year, due to many factors: poor spray weather conditions in the 1975 season, lack of adequate air power due to accidents and the normal spread of the budworm infestation in NB as well as in the susceptible forest of Eastern North America.
Planning for the huge 1976 project started several months prior to spray application and escalated for operational planners to seven days a week for four to five months prior to application. Actual application started on May 17 in one southern NB airstrip and terminated on June 21 in northern NB. During this time period, seven airstrips were active and utilized 3 DC6’s, 4 C-46’s, 41 TBMs and, part time, 4 Thrush Commanders. In addition, 4 Ag-Cats were used for small isolated areas at three airfields in southern and western NB.
The remainder of the fleet of aircraft was made up of some 39 light aircraft for guidance, transport, supervision, etc., along with a Search and Rescue helicopter, making a total fleet of 92 aircraft. A formidable fleet, since all aircraft maintenance was done within the project, including radio maintenance.
The flying personnel were only a part of the total, since living accommodations were available at seven large aircraft airstrips for up to 100 people each, with cook houses open on a 24-hour-per-day basis during operational spray periods. At each airstrip, the ground personnel were made up of Supervisors, Assistants, Clerks, Radio Operators, Batchers, Loaders, Recorders, Cooks, Waiters, Mechanics, Handymen, Janitors, First Aid, Assessment Crews, etc., a huge logistics problem assembling all personnel, some for only a month or so.
1976 proved to be a milestone for FPL in many ways: a record of some 9,591,792 acres sprayed, all with two applications. An additional sizable area received three applications, which resulted in just under 20 million flying acres utilizing over 90 aircraft and some 400 personnel. The complete application was finished within a five-week time frame and a record of just under a million acres was sprayed in one 24-hour period of very favourable spray conditions. This was a remarkable achievement that became very evident during the summer aerial survey that showed a recovering and relatively green softwood forest in New Brunswick!
This was all most gratifying especially when all but one TBM arrived safely home after upwards of 100 hours each of flying over extreme terrain and flying conditions. [Conair’s TBM C-FKCG crashed on May 29.]
Progression Towards Smaller Spray Blocks in New Brunswick
by H.J. Irving, General Manager, Forest Protection Limited
August 29, 1985, FPL files
New Brunswick spray programs since 1978 have tended toward smaller and more widely distributed spray blocks. This change becomes apparent when examining maps from the 1978 program, largely typical in design of programs in the decade prior to that year, and the 1985 program, which displays a much heavier emphasis on smaller, more precisely defined and more spatially independent blocks. Comparative statistics for the two years are listed below.
|TBM – Total Area Treated (‘000 ha)||1498||461|
|Ag Aircraft – Total Area Treated (‘000 ha)||55||240|
|No. of Blocks||81||746|
|No. of TBM’s||33||12|
|No. of Ag Aircraft||0||26|
(The 1978 program [also] used aircraft from J.D. Irving Ltd.)
Several factors have combined in producing the smaller block program. Some of these include:
(a) increasing heterogeneity of the forest due to:
- i) mortality
- ii) limit on clear cut size
(b) improved ability to delineate non-susceptible forest due to:
- i) new set of aerial photographs
- ii) GIS computer mapping and updating
(c) changes in policies defining forest conditions requiring treatment for:
- i) small woodlots
- ii) industrial forests
Early TBM Use in N.B. by Forest Protection Limited
[TBM’s vs Stearmans]
Don Henry, January 2008, FPL files
As early as 1954 there is documentation of commercial use of TBM’s as fire bombers in U.S.A. Evidence shows that this aircraft (TBF-1C, Bu#46122, Reg. N9394H) owned by Paul Mantz Air Services of Los Angeles, California, was flown by Ed Ball. Ed also flew TBM’s in N.B. during Spruce Budworm Operations in the mid 60’s, also in Maine in 1963 on their budworm spray project. [Ball was also the co-founder of Ball-Ralston Flying Service – C. Adam.] [Click HERE for the story of Paul Mantz and his aircraft and HERE [downloads as a pdf] for an image of the Wealth-Air TBM.]
With the availability of surplus TBM’s from the Canadian Navy, and with favourable performance reports as sprayers and water bombers in the U.S.A., Canadian contractors bought 15 TBM’s in 1958. The decision to introduce TBM’s into the N.B. spray program was not done without knowledge of their ability of sprayers in Canada. There is documentation of their use as sprayers in British Columbia in 1957 when four U.S. Registered aircraft were leased from U.S. contractors by Skyway Air Services of Langley, B.C., to spray for Spruce Budworm on Vancouver Island. [More info HERE]. Skyways at this time owned several Stearman in spray configuration, [and] they were (May/June) contracted by Forest Protection Limited to spray Spruce Budworm in New Brunswick.
The 1957 Spruce Budworm program in Eastern Canada was a huge project, with some 5.2 million acres to be treated in N.B. integrated with the Quebec program in Gaspe of approximately 1.5 million acres, using the same aircraft and personnel. This program utilized some 200 Stearman aircraft and 22 supervisory aircraft, operating out of 14 airstrips in N.B. and 6 in Gaspe, all in the spray season of approximately 7 weeks (May 20 – July 5) — a huge logistics endeavor involving some 1000+ temporary personnel. These 200 Stearman aircraft were supplied by 18 U.S. contractors and 6 from Canada, spread continent wide in both Canada and U.S.A. — a huge achievement! [This story is told in much detail on the sister site to this TBM archive: STEARMANS.]
In an attempt to explain the change by F.P.L. to using TBM’s starting in 1958, it can only be speculation at this time (some 50 years later) [that] their use in 1957 in B.C. (presumably favourable) and the logistics of the huge N.B. and Gaspe project using Stearman … were very convincing reasons for aircraft diversity, and in reviewing relative costs the change appears very positive.
The TBM carried four times the payload at about 80% greater speed with an operating range approximately double that of the Stearman. This resulted in far less personnel and approximately half of the airstrips required by Stearman. The general forested area requiring treatment was generally large and continuous thus not requiring the more maneuverable Stearman, which were more suitable for small isolated treatment areas.
In reviewing relative costs (1956-1960) with the same application rate, the cost difference per acre [was] substantial, being some 13% less in 1960 compared to 1957 and some 20% less in 1960 compared to 1956:
1956 – 1.9 million acres – 90 Stearman – 11 airstrips
1957 – 5.2 million acres – 200 Stearman – 14 airstrips
1960 – 2.6 million acres – 42 Stearman, 20 TBM’s – 6 airstrips