Douglas A/B-26 Invader

Technical specifications - Civil














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Specifications - Propulsion

Associated reading

Flying the A-26 Invader

Flight characteristics of the Douglas A-26 Invader

Stability control tests

Performance tables

Performance comparisons

General information for A/B-26 Invader

 
Manufacturer: The Douglas Aircraft Co. Inc., Santa Monica, Cal, USA.
 
Manufacturing Sub divisions:
  • Douglas, El Segundo, Calif (DE)
  • Douglas, Long Beach, California (DL)
  • Douglas, Tulsa, Oklahoma (DT)
 
Civilian modifications undertaken by: See patents and mods
  • Aero Trades Inc.,
  • Grand Central Aircraft Company,
  • LeTourneau,
  • Lockheed Air Service (LAS),
  • On Mark Engineering,
  • Rhodes Berry,
  • Rock Island Oil & Refining Co.,
  • L.B. Smith Aircraft,
  • Slick Airways,
  • Wold Corp.,
  • Intermountain Aviation,
  • Hamilton Aircraft
  • Lynch Flying Service.
 
Designed by: E Heinemann, Ted R. Smith and Robert Donovan
Sales manager for Douglas Aircraft: Nat Paschall
Sales manager for On Mark Engineering: - William Boone
Note: On Mark contracted to convert 18 No B-26B and 22 No B-26C Invaders, to On Mark B-26K counter invader status, total cost $16m. 
Designations: A-26; B-26, JD
First official flight: XA-26 10/07/1942 at Mines Field, El Segundo.
Douglas test Pilots: Benny Howard / John F Martin
Factory production period: 1942 - 1945
Primary service period: 1944 - 1969
Total number of sorties During the war in Europe: 11,567
Working life: 1944 - 2008 ( Incl. Air tanker ops ) 
Number built: 2452
Number cancelled: 4,000 ( before the end of WWII )
MMAC (Material Management Aggregation Code) - DK
Type/Weight class - L2P/L
 
Civilian nickname / Given name:
  • Invader
  • Little hummer/Little racer
  • Blue Goose/The Blivet ( CIA )
  • Marketeer
  • Marksman
  • LAS Super 26
  • Rhodes Berry Silver 60
  • Monarch 26
  • Consort 26
  • Smith Super 26
  • Smith Biscayne 26
  • Lynch STOL 26
  • Smith Tempo 1 & 2
 
Unit cost: US$242,595 (basic airframe 1943)
On Mark Marksman C - $361,492.00 ( Late 1961 )
 
 
 
 
 
Note:
  • It was the first medium bomber to use a NACA laminar-flow airfoil, double-slotted flaps and remote-control turrets.
  • All metal, semi monocoque fuselage.
  • Aluminum alloy monocoque engine mount.
  • Engines were cooled with a new type of high entrance velocity cowling.
  • It was the last twin engine propeller driven bomber to be built for the US Air Force.

Aircraft classification number

The aircraft classification number (ACN) is a number expressing the relative effect of an aircraft on the runway pavement for a specified standard subgrade category (ICAO).

Subgrade support strength category

The ranges of subgrade strength covered by these standard subgrade categories (designated as A, B, C and D) are shown below.

Flexible pavements

The flexible pavements have four subgrade categories:

  • A. High Strength – CBR 15 (All CBR above 13%).
  • B. Medium Strength – CBR 10 (For CBR between 8% to 13%).
  • C. Low Strength – CBR 6 (For. CBR between 4% to 8%).
  • D. Ultra Low Strength – CBR 3 (For CBR below 4%).

Rigid pavements

The rigid pavements have four subgrade categories:

  • A. High Strength – Subgrade k = 150 MN/m3 (550 lb/in3) (All k values above 120 MN/m3).
  • B. Medium Strength – k = 80 MN/m3 (300 lb/in3) (For values between 60 to 120 MN/m3).
  • C. Low Strength – k = 40 MN/m3 (150 lb/in3) (For values between 25 to 60 MN/m3).
  • D. Ultra Low Strength – k = 20 MN/m3 (75 lb/in3) (All k values below 25 MN/m3).

Aircraft Classification Numbers (ACNs)

                                        Flex pav'nt CBR%      Rigid pav'nt k (MPa/m3) 

           Max Wt kN    Tire Pr MPa    High  Med  L  V L        High  Med  L  ultra L

A-26               120                 .40                  7        8    10   11             8        8      9       9

B-26               156                 .48                  9       11   13   14            10      11     11     12

Standard A/B-26 Specifications prior to modification

General Specifications ( Covering all marks )
  • Length: 51' 3" (15.24 m)
  • Height: 18' 6" (5.64 m)
  • Wingspan: 70' (21.34 m)
  • Wing Area: 540 Sq. Feet (50.17 m)
  • Empty weight: 22,850 lb (10,365 kg)
  • Loaded weight: 27,600 lb (12,519 kg)
  • Max takeoff weight: 35,000 lb (15,900 kg)
Take off dist. required at gross max weight: 4000ft
Fuel capacity, Int: 1,332.1 Imp gal
Fuel capacity, Ext: 383 Imp gal in two drop tanks
 
  • Propulsion
    Number of Engines: 2
  • Powerplant: Pratt & Whitney R-2800-27 "Double Wasp" 18-cylinder radial engines; Horsepower: 2000 HP each (1,500 kW) Weight 2,350lbs
Propellers: Hamilton Standard 33D50
Wake category: Medium
 
Performance
  • Normal Range: 1400 miles (1,200 nm, 2,300 km)
  • Maximum (ferry) range: 3200 miles
  • Cruise Speed: 284 mph
  • Max Speed: 355 mph (308 knots, 570 km/h) at 15,000 feet
  • Ceiling: 22,100 feet (6,700 m)
Initial rate of climb: 10,000 ft in 8 min 6 sec
Rate of climb: 1,250 ft/min (6.4 m/s)
Wing loading: 51 lb/ft (250 kg/m)
Power/mass: 0.145 hp/lb (108 W/kg)
Combat radius (Nm): B-26B-839, B-26C-775, B-26K-606
Combat target altitude: Sea level
 
 
Airfoils
  • Wing Root Airfoil: NACA 65-215
  • Wing Tip Airfoil: NACA 65-215
Note: The rudder on the B-26K, was enlarged to improve single-engine handling.

Diving Speeds:
  • 26,000 lbs gross  -  425 IAS
  • 32,000 lbs gross  -  400 IAS
  • 35,500 lbs gross  -  360 IAS
Fuel capacity
Fuel capacity, Internal: 6.056 l
Plus provision for 1.173 l if the ventral barbette was omitted (mostly the Pacific theatre)
Fuel capacity, external: 1.741 l in two drop tanks.
Main Tanks: 300 gals each
Aux Tanks: 100 gallons each
Bomb Bay Tank: 125 gallons
Total Normal: - 925 gallons
Ferry Tank: 675 gallons
Total Ferry: - 1600 gallons

 
 
Individual aircraft specifications - General variations and modifications.
Apart from On Mark, the other specifications list only brief mods undertaken on the companies variants.

On Mark Engineering

 

On Mark Marksman

 

Specifications

Crew: 1(2)

Capacity: 6 to 8 passengers (including 'jump' seat)

Takeoff gross weight:  ........................................................ 35,000 lbs.

Landing weight:  ................................................................ 31,000 lbs.

Empty weight:      25,200 lb - 27,150 lb for the Special Purpose vers'n

Useful load:  .................................................................10 - 11,000 lbs.

Wing span:  ( with tip tanks )  ...............................................71 ft. 6 in.

Wing area: ......................................................................540 ft (50 m)

Length:  ...............................................................................53 ft. 10 in.

Height  ...................................................................................18 ft. 6 in.

 

Engines : ( by specification )

“Marksman A“ - Two P&W R2800-75/79 engines ( less than 350 hours SMOH ) with  23E50-505  propellers

“Marksman B“ - Two P&W R2800 83AM-4A  ( zero time SMOH ) with Hamilton Standard 33E60 propellers ( 43E60 reversible propellers optional )

“Marksman C“ - Two P&W R2800 CB16/17 ( zero time SMOH ) with Hamilton Standard  43E60  reversible propellers

Fuel capacity  : ( by specification )

“Marksman A“ - ( standard )  ..................................................................800 gal.

“Marksman B“ - ( standard plus 165-gal. wing-tip tanks )....................1,130 gal.

“Marksman C“ - ( stand, wing-tip tanks and Pliocell int wing tanks.....1,330 gal.

 

Performance *

Takeoff distance over 50 ft:  ( 32,600 lbs. )  ............................3,495 ft.

Takeoff ground run:  ( 32,600 lbs. )  .......................................2,450 ft.

Landing over 50 ft:.  ( without reversing props ).....................3,000 ft.

Two-engine ceiling:  ............................................................. 25,000 ft.

Single-engine ceiling:  ......................................................... 16,400 ft.

Single-engine speed:  ( at 16,400 ft.  )  ...................................200 mph

Max. rate of climb  ( 32,000 lbs. ) 

Sea level  ...............................................................................1,700 fpm

10,000 ft:  ..............................................................................1,300 fpm

20,000 ft:  .................................................................................500 fpm

 

Max. range, tip tanks & Pliocell wing tanks (norm reserve).....2,500 mi.

Norm range, tip tanks & Pliocell wing tanks (norm reserve)....2,100 mi.

Stall speed :

         Power off, gear-flaps down, 29,000 lbs., tip tanks  .........85 mph

         Same as above without tip tanks  ....................................95 mph

Note: Marksman B: Two 165 US gal (622 l) wingtip tanks)

Airfoils

Wing Root Airfoil: NACA 65-215 

Wing Tip Airfoil: NACA 65-215

 

Max. gear extension speed:  ..............................................160 mph IAS

Max. flap extension speed:  ...............................................208 mph IAS

Vne speed ( max. – never exceed ) at 35,000 lbs.   ...................365 mph

Cruise speed : ( by specification )

“Marksman A“  -  ( At 16,000 ft. )  ......................................................................................325 mph

“Marksman B“  -  ( At 18,000 ft. )  ......................................................................................350 mph

“Marksman C“  -  ( At 23,000 ft. )  ......................................................................................365 mph

Maximum speed: 365 mph (317 knots, 587 km/h)

Power/mass: 0.143 hp/lb (106.5 W/kg)

 

Fuel consumption : ( by specification )

“Marksman A“  -  ( Per engine )  ............................................................................80  gal./hr.

“Marksman B“  &  “C“  -  ( Per engine )  ..............................................................95  gal./hr.

 

  ( Where not indicated, performance is based on R2800-75/79 engines. All speeds are in statute miles )

Prices for these aircraft
On Mark Marksman A - $257,430.00
On Mark Marksman B - $314,715.00
On Mark Marksman C - $361,492.00
 
Note: These prices did not include for radio/Avionics, electronics or sales tax.
 

 

 

Note: On Mark Marketeer modifications

See equipment schedule for Marketeer N61B ( Bottom of page )

On Mark Engineering ( Marketeer ) Modification Details and Prices – May, 1962

The following is transcribed from a May 1962 price list from On Mark Engineering for civilian conversion of B-26 Invaders.

NOTE: Many of the prices listed below are based on performing the modification at the time of complete aircraft conversion and consequently would be slightly higher if performed separately. Price adjustment would depend on the configuration of the customer’s aircraft.


1. Fuselage and spar conversion. Install circumferential rear wing spar. Install Airstair door RH side. Install 8 windows ( 2 picture windows ). Recontour fuselage top &bottom. Modify wiring, plumbing, cables, floor, etc. $58,000

2. Fuselage conversion. Install belly ladder door. Install 8 windows ( 2 picture windows ). Recontour fuselage top only. Modify wiring, plumbing, cables, floor, etc. $38,000

3. Custom Interior. $17,000.

4. Deluxe Interior. $25,000.

5. Install Wing Tip Tanks ( 165 gal. each ). Modify wing plumbing and valves. Install boost pumps and dump valves. $16,710.

6. Install Pliocell Wing Tanks ( 100 gallons each ). Modify wing, plumbing and valves. $10,500.

7. Replace existing self-sealing main and aux. fuel tanks with lightweight Pliocell tanks. ( reduces airplane weight 450 lbs. ) $5,200. With top filler necks ( adds 90 gal. usable fuel ). Includes A.D. Note compliance. $6,000.

8. Install 103” Plastic Nose. Includes ladder, baggage door. Provides for 1,000 lbs. baggage and radar. $10,500.

9. Install dual controls. $5,500.

10. Install Co-Pilot Brake Pedals. $990.

11. Install 100,000 B.T.U. Heater and Ducting. $3,900.

12. Install Custom Instrument Panel. Includes complete set flight instruments for co-pilot. Includes custom glare shield for radio controls. $4,250.

13. Install Scott High Pressure Oxygen System. $1,800.

14. Install DC-6 Wheels and Brakes. $4,850. In kit form. $4,450.

15. Install Hytrol Anti-skid braking system. $5,250.

16. Chrome Plate landing Gear struts. $1,200.

17. Install Tip Tank Landing Lights. $1,050.

18. Install De-icer Boots all Surfaces. ( Goodrich high-pressure “stick-on” type ) $8,850.

19. Install Long all-metal rudder. Includes modified tail cone and vortex generators. $9,750.

20. Install Nose Wheel Steering. Choice of rudder pedal or aux. wheel control. $1,995. In kit form $1,550.

21. “Ceconite” covered Control Surfaces-exchange. $1,800. With new draft curtains $2,150. Installed complete $2,450.

22. Modify Canopy. Metalized top and install double glass $1,750.

23. Modify Cockpit Plumbing and Structure. Provide space for observer seat $3,100.

24. Install Refrigerated Air Conditioning. Operates in flight or on the ground $5,000.

25. Install Auxiliary Power Unit: New 105 ampere Homelite APU $2,450. Surplus 70 ampere APU $1,700.

26. Custom Exterior Paint – paint only. $3,850. Strip and clean $960. Seal Exterior $1,100.

27. Install 20-gallon Engine Alcohol Tank. $870.

28. Install Fire Warning and Fire Extinguishing System with Firewall Shut-off Valves. $2,650.

29. Install Modified Short Metal Nose. Includes ladder baggage door. $2,500.

30. Install New Bendix Weather Radar. Includes Sperry Gyro Antenna Stabilization ( 103” Plastic nose required ) $18,500.

31. Install Overhauled, Certified Sperry A-12 Autopilot unit $18,500.

32. Install P&W R-2800 “C” Series engines with Hamilton Standard 33E60 High-activity propellers and autofeather. Labor and installation material only. Engines and propellers priced separately. $15,450.

33. Install P&W R-2800 “CB” Series engines with Hamilton Standard 33E60 High-activity propellers and autofeather. Labour and installation material only. Engines and propellers priced separately. Includes ADI installation. $16,800.

34. Install propeller spinners and afterbodies. Includes cowling mod. For inside carb. air scoops. On request.

35. Install Hamilton Standard 43E60 reversing propellers on “C” or “CB” engines. Labor and installation material only. Propellers priced separately. $4,800.

36. Install Booster Tab Rudder and Vortex Generators ( with exchange rudder ). Lowers Vmc to 118 mph C.A.S. ( standard engines ). Includes new Ceconite cover and matching paint $3,950. In kit form $3,750.

37. Flap modification for increased flap extension speed. 25 degrees flaps may be extended at 250 mph I.A.S. $265. In kit form $145.

Grand Central Aircraft Company

Specifications as for a standard A/B-26 Invader, but with the following modifications:

  • Seating for six passengers in a soundproofed cabin

LeTourneau

Specifications as for a standard A/B-26 Invader, but with the following modifications:

  • Seating for six passengers in a soundproofed cabin.  
  • Air stair door.
  • 2 Pratt & Whitney R-2800-27/71 Double Wasp

Lockheed Air Service (LAS)

  • Increased interior height by raising the fuselage top and deepening the belly ( by 6 - 9 inches )
  • Increased the interior cabin length by adding a 6 foot " plug " in the fuselage aft of the wing.
  • New ring spar.
  • Constellation L-1049 Super G cabin windows in conjunction with pressurization.
  • Entrance "Airstair" to starboard and the escape panel opposite. 
  • Standard cockpit, but with small cockpit side windows, both incorporating heavier framing to withstand pressurization loads.
  • Newly designed fiber glass nose, increased to compensate for the added fuselage length aft of the wing.

Rhodes Berry

Some specifications as for a standard A/B-26 Invader, but with the following modifications:

  • Fuselage completely redesigned.
  • Seating for 16 passengers in a soundproofed cabin .
  • Nose gear now retracts straight back without first swiveling, as on stock Invaders.

Rock Island Oil & Refining Co.

Specifications as for a standard A/B-26 Invader, but with the following modifications:

  • Airframe extensively reconfigured with re-contouring and extensive re-skinning.
  • New wing spar design.
  • Seating for six passengers in a soundproofed cabin .
  • Floor heating.
  • New restroom.
  • New galley
  • Panoramic windows.
  • New airstair door on the rear starboard side.
  • New 30" extended nose.
  • Additional fuel cells in the outer wing panels, raising total fuel capacity to 1012 US gallons.
  • The cockpit fitted with dual controls, new instrument and overhead panels, and "metalized" double-paned cockpit canopies.
  • 2 Pratt & Whitney R-2800-79 Double Wasp

Slick Airways

Specifications as for a standard A/B-26 Invader, but with the following modifications:

  • New large window installed in the aft fuselage
  • New cabin door installed.
  • Tip tanks added along with other fuel system mods to wings.
  • Weather radar unit with the radome on the nose.
  • New Goodrich brakes.
  • Aft cabin floor lowered.
  • Mods undertaken on existing wing spars.

L. B. Smith Aircraft

Biscayne 26

  • Aircraft completely re engineered, with both original spars being replaced with ring spars built of aluminum.
  • Wing center section increased, which moved the engines on each side 20 inches from the cabin to reduce noise.
  • DC-6 wheels and brakes fitted.
  • New canopy and cockpit, lengthened nose, rebuilt fuselage.

Super 26

  • Interior designed by Charles Butler Associates, with a colour scheme feraturing gold, wheat and tones of blue. Cabinetry was of smooth hand rubbed blond walnut with the instrument and overhead panel in turquoise and eyebrow type lighting.
  • Fitted with wingtip fuel tanks and had executive accommodations 

Tempo I

  • (Unpressurized) Powered by 2 Pratt & Whitney R-2800 B-series Double Wasp

Tempo II

  • ( Pressurised) Powered by 2 Pratt & Whitney R-2800 C-series Double Wasp

Note: The Tempo's I and II were ten feet longer than a standard Invader and had a 28-foot fully soundproofed cabin that could accommodate up to 13 passengers.

Wold Corp.

Specifications as for a standard A/B-26 Invader, but with the following modifications:

  • Powered by two Pratt and Whitney R-2800-CB-16 Double Wasp engines, rated at 2,400 h.p. with water injection, and driving Hamilton Standard reversing propellers.
  • Seating for eight passengers in a fully soundproofed cabin, with four large reclining chairs and a divan.
  • New toilet
  • Extensive additional storage facilities

Optional equipment included the following:

  • Sperry A-12 autopilot
  • Bendix X-band and weather radar
  • Collins Integrated Flight System
  • Bendix D.M.E.
  • Sperry engine analyzers
  • Collins 51R3 Omni receiver
  • Bendix Omni receiver
  • 17L3 Collins transmitter
  • Series 440 Wilcox 50W V.H.F. transmitter simplexed with Wilcox receiver.
  • Dual Collins R.M.I.
  • Dual A.D.F. Bendix MN62, Bendix markerbeacon receiver
  • F-ll A isolation amplifier
  • Cockpit and cabin speakers
  • Collins 51V glideslope receiver
  • R89 glide-slope receiver.

Air tanker specific

Two doors - independent and leak-proof.

  • Each side divided into compartments to prevent the slurry from sloshing back and forth in flight and creating an undesirable bathtub wave effect.
  • When the doors open, vents also pop open on top of the fuselage, scooping up air to force the slurry out in one and a half seconds.
  • Bomb doors are shorter than the original - War time bomb load of 4,000 pounds (1,816 kg) was stored horizontally whereas the retardant tank is vertical.
  • Directly behind the right door is the three-inch (7.5 cm) Cam Lock loading receptacle, which enables 760 gallons of slurry to be pumped into the tank in just three minutes.

Note: Most air tankers have hydraulic bomb doors but some aircraft are equipped with air compressor pneumatic doors; operationally, there's no performance difference.

  • The original instrument panel is replaced with a redesigned panel which has been relocated and re grouped, the flight instruments are in the standard T-display, engine gauges are nicely grouped, and the nav/comm package is easy to reach and use.
  • The mph airspeed indicator (in World War II, miles per hour was the standard) has been replaced by the same instrument used in the T-33 jet trainer, calibrated in knots.
  • Aircraft today use knots (K) for airspeed, partly for standardization and also because navigation is easier using nautical miles (nm).
  • LORAN C navigation system installed

Note: The Lynch tankers used an older, four-door tank on all of their aircraft.

Air Spray, Conair and a number of American operators used Aero Union's two-door tank, which reused the A-26's original bomb doors.

 
A-26 retardant tank developed at Red Deer

w1tank3.jpg

w1tank2.jpg

Note: An air tanker company that operated 9 A-26 Bs and Cs for air tanker ops, looked into the possibility of swapping the K model rudder to their aircraft for single pilot operation.

 The actual difference was in the chord of the rudder - it was widened (about a foot) in an attempt to lower the VMC (minimum single engine control speed with one engine operating at take-off power and the second engine is windmilling - rather critical on any twin engine aircraft on take off - on the early model A/B 26s it was 140 kts)

For the most part, it was a straight forward swap. Simply remove the original B/C rudder, swap positions on the rudder attach brackets (Top bracket moved to the lower position and bottom moved to the top position) and bolt on the K rudder. However, the FAA insisted that we also had to install the two rows of vortex generators that had been installed vertically on the right side of the vertical stab in front of the rudder. Unfortunately the vortex generators were not available and the operator would have had to have them manufactured to match the original drawings so it didn't go forward with the modification.

w1w1p1520740.jpg

Above, Vortex generators on the fin of a B-26K, which directs dedicated airflow onto the rudder for more a responsive flying surface operation, especially during single pilot operartion. 































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