Thread Tools
Jan 29, 2014, 09:41 AM
Registered User
Thread OP

Douglas A-26, B-26 Invader A-26A Counter Invader

from wikipedia:

The Douglas A-26 Invader (designated B-26 between 19481965) was a United States twin-engined light bomber and attack aircraft built by Douglas Aircraft during World War II that also saw service during several of the Cold War's major conflicts. A limited number of highly modified aircraft (designation A-26) served in combat until 1969.

It was found to be a fast aircraft capable of carrying twice its specified bomb load. A range of guns could be fitted to produce a formidable ground-attack aircraft.

The A-26 was originally built in two different configurations. The A-26B had a "solid" nose, which originally could be equipped with a combination of anything from .50 caliber machine guns, 37mm auto cannon, 20mm or even a 75mm pack howitzer, but normally the solid nose version housed six (or later eight) .50 caliber machine guns, officially termed the "all-purpose nose", later commonly known as the "six-gun nose" or "eight-gun nose". The A-26C's "glass" nose, officially termed the "Bombardier nose", contained a Norden bombsight for medium altitude precision bombing. The A-26C nose section included two fixed M-2 guns, later replaced by underwing gun packs or internal guns in the wings.

The Douglas company began delivering the production model A-26B in August 1943 with the new bomber first seeing action with the Fifth Air Force in the Southwest Pacific theater on 23 June 1944, ...

... The A-26As were retired (from US service) in 1969 when they had reached the safe limits of allotted flying time.

However A-26's were still flying combat missions in SE Asia as late as 1977.

I would like to thank Mr. Martin J Simpson for allowing me to link the following images from his website

If a builder needs more information ... there are a large number of other drawings and data available from that site.

General characteristics

Crew: 3
Length: 50 ft 0 in (15.24 m)
Wingspan: 70 ft 0 in (21.34 m)
Height: 18 ft 3 in (5.64 m)
Wing area: 540 ft (50 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)
Powerplant: 2 Pratt & Whitney R-2800-27 "Double Wasp" radials, 2,000 hp (1,500 kW) each


Maximum speed: 355 mph (308 kn, 570 km/h)
Range: 1,400 mi (1,200 nmi, 2,300 km)
Service ceiling: 22,000 ft (6,700 m)
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)


Up to 8 0.50 in (12.7 mm) M2 Browning machine guns in the nose (1,600 rpg)
8 0.50 in (12.7 mm) M2 machine guns paired in four optional underwing pods
2 0.50 in (12.7 mm) M2 machine guns in remote-controlled dorsal turret
2 0.50 in (12.7 mm) M2 machine guns in remote-controlled ventral turret
Bombs: 6,000 lb (2,700 kg) capacity - 4,000 lb (1,800 kg) in the bomb bay plus 2,000 lb (910 kg) carried externally on underwing hardpoints
Last edited by TedD60; Apr 09, 2016 at 09:40 AM.
Sign up now
to remove ads between posts
Jan 29, 2014, 09:49 AM
Registered User
Thread OP

May 10, 2014, 01:03 PM
homo ludens modellisticus
Ron van Sommeren's Avatar
Building continues in october 2014

Vriendelijke groeten Ron

Last edited by Ron van Sommeren; Apr 09, 2016 at 07:29 PM.
May 10, 2014, 01:29 PM
Registered User
Although all of the above drawings show it more or less correctly, most historical articles seem not to mention the fact , A-26/B-26 has "laminar" airfoils, similar to p-51's.

According to "Incomplete Guide to Airfoil Usage" same airfoil used at both root and tip (but I would verify !!)
Last edited by packardpursuit; May 10, 2014 at 01:41 PM.
Apr 09, 2016, 09:14 AM
Registered User
Thread OP
B-26K to A-26A Counter Invader

From wikipedia:

On 11 February 1964, two pilots from the 1st Air Commando Wing stationed at Hurlburt Field, Fla., died in the crash of a B-26 on Range 52 at Eglin AFB when it lost a wing during pull-out from a strafing pass. The aircraft was participating in a demonstration of the Special Air Warfare Center's counter insurgency capabilities and had completed a strafing run when the accident occurred. SAWC had presented the demonstration on an average of twice each month for the previous 21 months.[27] B-26 aircraft used by USAF Commandos in Vietnam were grounded 8 April 1964, following an official investigation into the 11 February accident. B-26 aircraft in use by the Vietnamese Air Force were also grounded in accordance with the U.S. ruling.
An A-26A of the 609th SOS in 1969

In response to this, the On Mark Engineering Company of Van Nuys, California was selected by the Air Force to extensively upgrade the Invader for a counterinsurgency role. The first production flight of the B-26K was on 30 May 1964 at the Van Nuys Airport. On Mark converted 40 Invaders to the new B-26K Counter-Invader standard, which included upgraded engines, propellers, and brakes, re-manufactured wings, and wing tip fuel tanks, for use by the 609th Special Operations Squadron. In May 1966, the B-26K was re-designated A-26A for political reasons (Thailand did not allow the U.S. to have bombers stationed in country at the time, so the Invaders were redesignated with an "A", for attack aircraft) and deployed in Thailand to help disrupt supplies moving along the Ho Chi Minh trail. Two of these aircraft were further modified with a Forward Looking Infrared (FLIR system) under project Lonesome Tiger, as a part of Operation Shed Light.

More on the developmnt of the A-26A:

This sight also includes the Flight and maintenance manuals:

Crew: 2

Length: 51 feet 7 3/16 inches
Wingspan: 71 feet 6 inches (over wingtip tanks)
Height: 19 feet 0 inches
Wing area: 540 square feet.
Empty Weight: 25,130 pounds empty
Loaded Wieght: 37,000 pounds loaded
Max takeoff weight: 39,250 pounds maximum.
Powerplant: Two Pratt & Whitney R-2800-52W air-cooled radials, each rated at 2500 hp for takeoff and 1750 hp at 15,000 feet.


The A-26A R-2800-52W engine was the military version of the CB-17. The R-2800-52W had the bolted front case like that of the "C" series R-2800. The ignition was, quoting the "Dash -1"

The ignition system was a low tension, high altitude type, comprised essentially of one double tandem, low tension magneto, two distributors, thirty-six shielded ignition harnesses, eigthteen double high tension coils, shielded spark plugs, and one induction vibrator for each engine.

The system was completely independent of the aircraft electrical system, with exception of the induction vibrator."

The distributors were those shaped like an inverted tapered drinking cup. The coils were bolted to the baffle plate on top of each cylinder.


Maximum speed: 323 mph at 15,000 feet, 291 mph at sea level.
Cruising speed: 169 mph.
Stalling speed: 114 mph.


Wing Root Airfoil: NACA 65-215
Wing Tip Airfoil: NACA 65-215

The following items were some of the more significant and visible mods included in upgrading to the On Mark B-26K.

Higher powered Pratt & Whitney R-2800-52W Double Wasp.
New DC-6 props ( shortened ). With reversing capability
Wing tip fuel tanks
Improved and strengthened wings with more pylons re manufactured fuselages Updated avionics.
Landing Gear strengthened and KC-135 wheels/brakes used.
Larger rudder installed, Rudder was broadened some 8 inches
Dual controls and a standardized cockpit Provisions for JATO use Gun armament was standardized with an eight gun nose.
Turrets were deleted and paneled over
Larger rudder installed, the actual difference is in the chord of the rudder - it was widened 12 inches, 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) as a single pilot facility.

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, to emulate the B-26K's handling characteristics.

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.

The B-26B was used in Vietnam in the early 1960s in the armed reconnaissance role. The 4400th Combat Crew Training Squadron (CCTS) initial stated purpose was to provide advisors and training in support of counter insurgency operations. The aircraft began flying in 1961 in support of various operations including Ranch Hand and Farm Gate; however, with two losses due to structure failures, the B-26Bs were withdrawn in 1964.

The B-26Bs were suited to the counter insurgency role, so the USAF ordered an improved prototype aircraft built with the designation YB-26K. A B-26C (S/N 44-35684) was sent to On Mark Engineering Co. for conversion. The engines were updated to 250-hp Pratt & Whitney R-2800-103W radial engines, each equipped with a larger propeller. The wing was strengthened, 165-gallon wing tip fuel tanks were added, and four weapons pylons were installed on each wing. The vertical stabilizer and rudder were enlarged. The cockpit was adapted for dual controls and improved, updated avionics were installed. The nose retained the eight .50-cal. machine gun arrangement, and the wings each had three .50-cal. machine guns.

Testing began in January 1963 and showed the aircraft to be well suited for the planned counter insurgency mission over Southeast Asia. Based on the success of the YB-26K, a production contract for conversion of 40 more aircraft was signed later in the year.

Last edited by TedD60; Apr 09, 2016 at 09:34 AM.
Apr 09, 2016, 09:26 AM
Registered User
Thread OP

Apr 09, 2016, 06:59 PM
Registered User
Thanks all for the posts! Most of what you have posted are WWII-era Douglas A-26 Invaders, which is my favorite multi-engine military aircraft. My absolute favorite version of this aircraft is the Vietnam-era On Mark B-26K Counter Invader!
Apr 09, 2016, 07:31 PM
homo ludens modellisticus
Ron van Sommeren's Avatar
Maidened in May 2015, see
Videos of my models

Jan has lots'n lots of documentation, under Downloads.

Originally Posted by Ron van Sommeren
Building continues in october 2014

Vriendelijke groeten Ron

Apr 11, 2016, 03:59 PM
Registered User

is this thred dead?

I like this type of building projects but will the builder talk about

1. what retract speed motors is he using and how does he make the landing gear motors run forward and backwards?

2. how did he make the p61 window frames?

3. does he have a wiring diagram showing how to wire the landing gear motors and are they connect to the retract plug in on the rx via a y lead?

very well done I like to see more info.

Apr 13, 2016, 06:32 AM
Registered User
Thread OP

Go to this website:

and go to "Contact Plans and Links.

All of his contact information is there.

Quick Reply

Thread Tools