USAAC/USAAF/USAF/Unified Attack Aircraft Designations

Last revised September 18, 2015


The recent resurgence of questions about the mysterious "gap" in the the post-1962 attack plane designation scheme (at A-11) leads me to repost this summary of American attack planes. Some of the confusion is due to the fact that there were TWO separate and distinct A-for-attack series of aircraft, one used by the Army in the years 1926-1948, and the other used by all the services in the years after 1962.

The Army introduced the A designation category in 1926. It applied to attack and light bombardment categories of combat aircraft.

This is the original A-series, which covered the years 1926-1948:

A-1				Not assigned, since it clashed with th	
				Cox-Klemm XA-1, an ambulance plane still in service.

Douglas XA-2			Conversion of O-2 two-seat observation biplane
                      		to attack configuration.  Lost out to Curtiss A-3
				in attack plane competition.  Only one built.

Curtiss A-3 Falcon		O-1B observation plane adapted to attack role
                       		by addition of bomb racks and additional 0.30
                      		cal gun in each lower wing.  144 built.

Curtiss XA-4 Falcon 		A-3 modified to test 440hp P & W R-1340 Wasp
                      		radial engine.  Only one built.

Curtiss XA-5			Attack counterpart of XO-16 two-seat observation
                      		biplane.  Canceled before any could be 
                      		delivered.

Curtiss XA-6			Attack counterpart of XO-18 two-seat observation
                       		biplane.  Cancelled before any could be 
                       		delivered.

General Aviation 		Two-seat low-wing monoplane ground attack plane.
    (Fokker) XA-7      		Lost out to Curtiss A-8 for production orders.


Curtiss YA-8			Two-seat monoplane ground attack aircraft. One
                       		8 built.

Lockheed YA-9			Two-seat monoplane attack aircraft.  Attack 
                       		version of Lockheed YP-24 experimental pursuit
                        	aircraft. Parent company (Detroit Aircraft) went belly-up and
                       		none were produced.

Curtiss YA-10	    		First YA-8 reequipped with a 625 hp P&W Hornet
                      		radial engine.  175 mph.  Proved that radial
                      		engine was preferable to liquid-cooled engine
                      		for attack role, and convinced Army to have A-8B
                       		aircraft on order be produced as A-12.

Consolidated A-11      		Development of Lockheed YA-9.  Two-seat 
                       		monoplane attack aircraft. Performance was
                       		well advanced over its contemporaries, but the
                        	Army disliked liquid-cooled engines for ground
                        	attack planes.  Pursuit versions were P-30 and
                        	PB-2A.

Curtiss A-12 Shrike		Two-seat monoplane attack aircraft.  Adaptation
                       		of A-8 design to 690 hp Wright R-1820 Cyclone 
                      		radial engine. Forty-six A-12s built for
                       		U. S. Army.  20 export versions sent to China.
                               
Northrop XA-13			Two-seat monoplane attack aircraft.
				Extensively modified version of Gamma 2C 
				commercial monoplane. 

Curtiss XA-14			Two-seat, twin-engined ground attack aircraft.
				Only one built.

Martin XA-15			Attack version of Martin YB-10 bomber. 
                       		Abandoned in design stage in favor of Curtiss
                       		XA-14.

Northrop XA-16			XA-13 fitted with 950 hp P&W R-1830-7 radial. 
                     		Only one built.  Test results indicated that the
				aircraft was overpowered and that production
				aircraft should have either a smaller engine
				or larger tail.
	
Northrop A-17			Two-seat, single-engine attack aircraft.  One
                     		P&W R-1535 radial engine.  A-17 had fixed
                      		landing gear, A-17A had retractable landing
                     		gear.  Numerous exports.

Curtiss Y1A-18 Shrike		Two-seat, twin-engined ground attack aircraft.
				Same armament as XA-1, but bombs were
                      		carried in wing bays rather than in fuselage.
                      		13 built.  Used primarily for operational
                        	training.

Vultee YA-19			Two-seat attack aircraft.  Evolved from V-11GB
                       		export attack aircraft.  Five built.

Douglas A-20 Havoc		Twin engine, three-seat attack bomber
				Most widely-used aircraft in the A series.
				Produced in many different versions with many
				different armament schemes.  7478 built.
				F-3 was photo recon version.
				P-70 was night-fighter adaptation equipped with
				radar.

Stearman XA-21                  Three-seat, twin-engine light bomber. No production orders.
                                Only one built.

Martin A-22 Maryland            Twin engine, three-seat attack aircraft.	
                                Lost out to Douglas A-20 for Army production
                                orders, but ordered by French.  Flew in combat
                                during German invasion.  After French collapse,
                                remaining Marylands were taken over by British.
                                Served with British units in Mediterranean and
                                North Africa.  Some service with Vichy French. 

Martin A-23                     Proposal for twin-engine attack aircraft powered
                                by Wright R-3350 radials.  Project was dropped.

Douglas A-24 Dauntless          Army version of SDB Dauntless carrier-based
                                dive bomber.  A-24 was similar to Navy SBD except for
                                removal of deck landing gear and a new tail
                                wheel.  953 built.  First examples entered
				Army service in 1941. Most A-24s remained
				Stateside, where they were used primarily for
				training, but some did see combat.
				

Curtiss A-25 Shrike 		Army version of SB2C-1 Helldiver carrier-
                                based dive bomber. 900 delivered to US Army.  
                                Army eventually decided that it didn't need
                                dive bombers, and A-25 never entered combat.  
                                Most used as trainers and target tugs.  Ten were
                                delivered to Australia.  410 were turned over
				to the US Marine Corps, which used them as
				operational trainers under the designation 
				SB2C-1A.
     
Douglas A-26 Invader            Three-seat, twin-engine light bomber.  	
				Regarded as USAAF's best twin-engine bomber at
				end of WW2, and plans were under way to convert
				all A-20, B-25, and B-26 units to the A-26 at
				war's end.
				B-26 saw lots of action in Korean War in armed
				reconnaissance and interdiction role.
				Withdrawn from front-line service with USAF 
				in mid-1950s and replaced by B-57 and R/B-66.
				Many Invaders were sold as surplus on the
				civilian market, and converted to executive
				transports.
				Many were exported to foreign air forces.  Some
				are still in service.

North American A-27             Designation for 10 NA-69 export attack planes
			        ordered by Thailand, but siezed by Army lest 
                                they fall into Japanese hands. 
 				Used only for training.
 
Lockheed A-28 Hudson            Hudson was military adaptation of Model 14
				commercial airliner designed to British
				requirements.  Nearly 2000 Hudsons were 
				acquired by British, either by direct purchase
				or via Lend-Lease.  After Lend-Lease was 
  				approved in 1941, outstanding British contracts
				for Hudsons (and other aircraft as well) were
				taken over under Army contracts and produced
				under USAAF designations and serial numbers.
				Most went directly to British Commonwealth air
				forces, and never served with USAAF.

Lockheed A-29 Hudson            Designation given to Hudson light bomber ordered
				under Lend-Lease for service with British 
				Commonwealth forces.  Differed from A-28 in
				being powered by two Wright R-1820 Cyclone
				radials.  Most went directly to Commonwealth
				air forces and never served with USAAF.

Martin A-30 Baltimore           Twin-engine attack bomber built for British use
                                under Lend-Lease.  Served exclusively in the
                                Mediterranean area with British, South African, 
                          	Greek and Italian Co-belligerent air forces.
                                None used operationally by USAAF.  1575 built. 

Vultee A-31 Vengeance           Two-seat, single-engined dive bomber.  One
				Most were sent to the British under Lend-Lease.
				Vengeances in US service used
                             	primarily for training and never saw combat.

Brewster XA-32                  Single-seat attack bomber. Speed and range performance fell
                                below expectation.  Project cancelled.

Douglas A-33                    Designation for 31 Douglas 8A-5 attack planes
                                taken over from Peruvian order. 
                                Used for general utility service.  Never saw
                                any combat.

Brewster A-34 Bermuda           Designation assigned for Lend-Lease 
                                documentation to SB2A Buccaneer naval dive
                                bomber.  None ever served with AAF.

Vultee A-35 Vengeance		Two-seat, single-engined dive bomber.  
                       		Modification of A-31 with four fixed 0.50 cal
                      		guns in wing, one 0.50 cal gun in rear cockpit.
				Most sent to the British and the 
                       		Australians.  Some given to Free French.
				Never saw combat in USAAF service, serving only
				in training and target-towing roles.

North American A-36 Mustang     Dive bomber version of P-51 Mustang fighter.
				First version of Mustang to see action in USAAF
				service.
				Saw action primarily on Italian front and in
				India. 

Hughes XA-37                    Twin-boom, twin-engined light bomber project.
                                Most of airframe constructed of Duramold, a
                                material made of heat-bonded wood and plastic.
                                Carried no armament. 
				USAAF considered it as a bomber escort, as a 
				fighter, and as an attack aircraft.  In its
				fighter incarnation, it seems to have had the
				designation "XP-73" reserved for it.  The
				designation "XA-37" refers to its attack 
				incarnation. 
			
Beechcraft XA-38 Destroyer      Two-seat attack bomber.  Two Wright R-3350
                                radials. Delayed by lack of 
              			availability of engines, which were needed by
                                B-29.  Never reached production.

Kaiser-Fleetwings XA-39         Single seat, single-engined light bomber.
			        One P&W R-2800 radial. 
                                Never got past the mockup stage.        

Curtiss XA-40			Single seat, single-engined light bomber.
			        One Wright R-3350 radial. 
                                Never got past the mockup stage.        
    
Convair XA-41                   Single seat, single engine close-support
                                aircraft.  One P&W R-4360 radial.  Four 37-mm
                                cannon and four 0.50 cal guns in the wings.
                                Internal bomb bay could carry 3000 lbs of 
                                bombs.  Flight tests showed promise, but
                                Army close support was well provided for by P-47
                                Thunderbolt and A-26 Invader.  No production
                                orders.  Only one built.

Douglas XA-42                   Proposal for twin-engine attack aircraft powered
				by two Allison V-1710 liquid cooled engines 
				mounted in fuselage and driving two contra-
				rotating props in tail. Design 
				showed greater potential as a medium bomber and
				was redesignated XB-42

Curtiss XA-43                   Proposal for two seat, four jet attack plane.
				Project cancelled in early design stage.  Funds
				and serial numbers transferred to similarly-
				configured XP-87 Blackhawk night fighter.

Convair XA-44                   Tactical bomber with three 4000 lb. st. General
				Electric J-35 turbojets buried in the fuselage 
				and fed by two lateral intakes.  30-degree
				swept-forward wing.  Redesignated XB-53 in 1948.
				Cancelled before any could be built.

Martin XA-45			Three-jet light tactical bomber.  Redesignated
				XB-51 in 1948.

	[The original A series ends at this point.]

In 1948, the separate A category was eliminated from the Air Force designation scheme. Henceforth, all future Air Force planes that fell under the attack category were to be classified under B (for bomber). At that time, only two aircraft from the original attack series still remained in service with the Air Force--the Douglas A-26 Invader and the Douglas A-24 Dauntless. The Invader was redesignated B-26. There was no danger of confusion with the Martin B-26 Marauder, since all Marauders had been removed from active service by that time. So there were TWO airplanes that carried the B-26 designation, but they didn't both serve at the same time! In addition, the few Douglas A-24s still serving with the USAF in 1948 were redesignated F-24, a fighter category. Again, there was no possibility of confusion, because the prior P-24 designation had been carried by a Lockeed design of the early 1930s which never attained quantity production.

1962 Unified Designation Scheme

Prior to 1962, the US Navy had its own separate designation scheme for its attack aircraft. In 1962, Secretary of Defense Robert McNamara decided to unify the aircraft designation schemes of all the services under one umbrella. In addition, the A for attack category (which had been eliminated in 1948) was reintroduced. The Air Force initially had no aircraft that fell into the A category, but the Navy did have some and all of these were duly redesignated. In later years, the Air Force did acquire some attack aircraft, and these were assigned numbers in the A series in the sequence in which they were ordered into service.

The attack planes in the post-1962 A-category are:

Douglas A-1 Skyraider		Formerly designated AD.  Single-engine,
                                carrier-based attack aircraft.  One Wright
                                R-3350 radial. 322 mph at 15,000 ft.
				Four 20-mm cannon in wings, underwing load of
                                up to 10,000 pounds of bombs.  Night-attack,
                                antisubmarine warfare, ambulance, cargo,
                                and radar picket versions built.  Also served
                                with USAF, Royal Navy, France, Vietnam.
                                Served in Korean, Algerian, and Vietnam wars.  
				Total of 3180 built.

North American A-2 Savage       Formerly designated AJ.  Three-engined carrier-
                                based strategic bomber.  Two 2300 hp P&W 
				R-2800-44W radials in underwing nacelles, 
				one Allison J33-A-10 turbojet of 4600 lb. st
                                in rear fuselage. 
				Most Savages did not serve in their intended
				roles as strategic bombers, but were converted
				as flight-refuelling tankers.

Douglas A-3 Skywarrior		Formerly designated A3D.  Twin-jet, swept-wing
                                carrier-based strategic bombing aircraft.  Two 
                                P&W J57-P-6A turbojets.  Many converted to
                                aerial tankers, electronic countermeasures
                                planes, and trainers.  Total of 284 built.
				

Douglas A-4 Skyhawk             Formerly designated A4D.  Single-engine carrier-
                                based attack aircraft.  Versions A through D
                                powered by Wright J-65 jet.  E version powered
                                by P & W J-52 jet. 
				Extensive service with US Navy during Vietnam
				War. Served with IAF during "War of Attrition"
                                and Yom Kippur War.  Served with Argentina
                                during Falklands/Malvinas campaign.  Also
                                delivered to New Zealand, Singapore, and Kuwait.
				2960 built.

North American A-5 Vigilante    Formerly designated A3J.  Twin-engine, two seat
                                carrier-based supersonic strategic bomber and 
                                reconnaissance aircraft.  
			        In 1964, it was decided that Navy strategic role
                                would in the future be pursued exclusively by 
				Polaris-armed nuclear submarines and not by
                                aircraft.  Remaining A-5s were all converted
                                to RA-5C reconnaissance configuration.  
 				Total of 156 Vigilantes built.      

Grumman A-6 Intruder            Formerly designated A2F.  Twin engine, two seat
                                carrier-based all-weather attack aircraft.
				Two P&W J-52 turbojets mounted below wing roots.

Ling/Temco/Vought A-7           Single seat attack and close support aircraft.
            Corsair II		Looks much like a snub nose F-8 Crusader.
				A, B versions are Navy carrier-based attack
				planes powered by P&W TF-30 turbofans and 
				armed with two 20 cannon.  D is Air Force land-
				based version with one Allison TF-41 turbofan
				and armed with one 20-mm rotary cannon.

McDonnell-Douglas AV-8          Single-seat V/STOL close support and tactical
		Harrier         reconnaissance aircraft.  License-built
                                British Aerospace Harrier.

Northrop A-9                    Twin-engine, single-seat close air support
                                aircraft.  Two Lycoming YF102 turbofans under
                                the wing roots of a high wing.  Lost out to
                                Fairchild Republic A-10 for production orders.

Fairchild Republic A-10         Twin-engine, single-seat close air support
          Thunderbolt II        aircraft.  Two General Electric TF34 turbofans
                                in pods above and behind low-mounted wings.
                                Primary armament is seven-barrel GAU-8/A
                                30-mm antitank cannon. 
                              
A-11				This one appears never to have been assigned.
			        The reasons are obscure.  One possibility is 
			        that the A-11 designation was not used because 
				someone might "confuse" it with the "A-11"
				designation which LBJ applied deceptively
				to the supersecret Lockheed A-12 spyplane.  Another
				possibility is that A-11 was reserved for the Grumman design
				for the Advanced Tactical Aircraft competition that was won
				by the A-12 Avenger II.
 				Another possibility is that A-11 is the  
				designation given to an as-yet-unannounced
				"black" project.  Noone seems to know for
				sure.  Anyone who knows isn't talking.

McDonnell Douglas/General       Two-seat low-observable medium attack aircraft.
    Dynamics A-12		Extensive use of composites.  Designed as
       Avenger II  		replacement for Grumman A-6.  Large flying
				wing.  Typical A-6 weapons load internally.
				Additional ordinance can be carried externally
				when stealth is not important.  Range and
				speed supposedly exceed those of A-6.  Project was cancelled
				in early 1991 due to cost overruns and schedule
				slippages.

From this point on, there are "gaps", since these later A- aircraft were attack planes that had been converted from other roles.


General Dynamics A-16		Proposed close air support version of F-16
				Fighting Falcon fighter. Not built.

McDonnell Douglas A-18		Designation given to attack version of F-18
		Hornet		twin-engined, single-seat carrier-based
				fighter.  Initially, the F-18 and A-18 were
				envisaged as separate and distinct aircraft
				fulfilling different requirements.  However,
				during the design phase the two aircraft evolved
				in such a manner that they differed from each
				other only in minor details, and the Navy
				decided to combine both planes under the joint
				designation F/A-18.
  
Douglas A-26A Counter Invader   Originally designated B-26K.  Conversion of
				existing B-26 airframe to counter-insurgency
			        role.  While operating in Thailand,
				the aircraft were redesignated A-26A, since
			        a treaty between that government and the USA
				forbidded the basing of "bombers" in Thailand.
				Phased out of service in 1969.

A-29B			Allocated to Embraer Super Tucano, but this was not an official DoD designation.

Cessna A-37 Dragonfly		Initially designated YAT-37D.  Attack version
				of T-37 tandem, two-seat primary jet trainer.
				


Sources:


  1. American Combat Planes, Third Enlarged Edition, Ray Wagner, Doubleday, 1982.

  2. McDonnell Douglas Aircraft, Rene J. Francillon, Naval Institute Press, 1988.

  3. Curtiss Aircraft, 1907-1947, Peter Bowers, Naval Institute Press, 1979.

  4. Lockheed Aircraft since 1913, Rene J. Francillon, Naval Institute Press, 1987.

  5. Boeing Aircraft since 1916, Peter M. Bowers, Naval Institute Press, 1989.

  6. United States Military Aircraft Since 1909, Gordon Swanborough and Peter M. Bowers, Smithsonian, 1989.

  7. E-mail from Vahe demirjian on A-11, A-29B