XP-67 Moonbat — Engineering Reports, Test Data & Program History Collection

The XP-67 "Moonbat" was one of the most aerodynamically radical experimental interceptors of World War II — a twin-engine, long-range fighter designed by the McDonnell Aircraft Corporation at Lambert-St. Louis Municipal Airport under Army Air Forces contract. Its blended-wing-body configuration, true airfoil fuselage cross-sections, and laminar-flow wing surfaces placed it decades ahead of its time. The programme was ultimately cancelled in late 1944 after persistent Continental XI-1430 powerplant failures and the total destruction of the sole flying prototype in a ground fire on 6 September 1944.

This archival collection assembles nine primary declassified documents from the Army Air Forces Materiel Command and the McDonnell Aircraft Corporation, spanning the full programme lifecycle from the 1941 ducted radiator engineering studies through the 1946 classified case history compiled by the Historical Division Intelligence T-2 at Wright Field.

1. Airframe & Aerodynamic Configuration

• True Airfoil Profile: Fuselage and engine nacelles utilised cross-sections shaped as true NACA airfoils — minimising interference drag across the entire wetted surface
• Blended-Wing Body: Wing, centre section, and nacelles merged into a unified organic body — a configuration not seen again until the B-2 Spirit
• Laminar-Flow Wings: Smooth skin tolerances critical to maintaining laminar-flow characteristics at high speed
• Testing Collaborators: Wind tunnel studies conducted by the McDonnell Aircraft Corporation, NACA, and the University of Detroit

2. Powerplant — Continental XI-1430

• Engine Type: 2× Continental XI-1430-17 and XI-1430-19 — liquid-cooled, 12-cylinder inverted-vee
• Output: 1,350 hp each — leaving the heavy airframe chronically underpowered
• Overheating: Aluminium skin sculpted tightly around nacelles choked critical cooling airflow
• Exhaust Thrust: Unique exhaust configuration designed to generate supplemental thrust
• Turbocharger Failures: General Electric turbochargers routinely failed to deliver expected high-altitude performance

3. Handling & Stability

• Controllability: Counter-rotating Curtiss Electric propellers minimised engine torque during takeoff
• Aerodynamic Instability: Airflow separation around blended tail and wing junctions — documented in flight test reports
• Stall Characteristics: Heavy, underpowered weight caused unfavourable stall behaviour
• Undercarriage: Wide-track tricycle gear with oversized tyres for rough-field deployment

4. Performance Data

5. Engineering Modifications & Proposed Variants

• Dihedral Modification: Wing dihedral increased from 5° to 7° to combat rolling instability
• Nacelle Redesign: Ducts widened and rear nacelles cut back in early 1944 to expose hot exhaust
• Propeller Cuffs: Added to force more cooling air into engine inlets
• XP-67E Variant: Proposed unarmed photo-reconnaissance variant with mixed piston and GE I-20 turbojet propulsion — never built
• Armament: Designed for six 37mm M4 cannons — no guns were ever fitted to the prototype

Document Manifest

• Memorandum Report OJR/mac/47 — XP-67 Airplane, AAF No. 42-11677: Pilots' Comments, Section Flight, Serial No. Eng-47-1755-A — Army Air Forces Materiel Command, 19 May 1944 — Declassified
• AAF Technical Report 5412 — Final Report on the XP-67 Airplane: Army Air Forces Air Materiel Command, Wright Field, Dayton, Ohio — Restricted / Declassified
• Engineering Report No. 43 — Experimental and Theoretical Analysis of Ducted Radiators, Item 1.e, Contract 41-1685 W 935 ac 15840: Lambert-St. Louis Municipal Airport, June 30, 1941
• Report No. 176, Serial 5 — Study of Modifications to XP-67 Cooling System: Lambert-St. Louis Municipal Airport, September 1943 — Confidential / Declassified
• XP-67 Wind Tunnel Report — Army Air Forces Air Materiel Command
• XP-67 Vibration Report — Army Air Forces Materiel Command
• XP-67 Modification Reports (MRs) — Army Air Forces Materiel Command
• XP-67 Squawk Sheet — Form E: MAC 203 (6-14-43), 7 January 1944 — 25-item inspection defect log covering turbocharger failures, structural damage, wiring burns, and bulkhead damage — Enclosure C, M.A.C. Ltr. 200-1033-kbg, dated 19 January 1944
• Case History of XP-67 Airplane: Compiled by Historical Division Intelligence T-2, Air Materiel Command, Wright Field, July 1946 — Originally Secret — Declassified per Executive Order 10501, Authority NND 760052, V-2095-1

⚠️ Regulatory Notice: Under FAA 14 CFR § 43.13 and EASA Part-M, any mechanic performing maintenance on an active aircraft must use current, manufacturer-approved revision-controlled data. This archival document does not satisfy that requirement.

This is an archival, static-copy edition fixed at its original publication date. Intended for historical reference, flight simulation, museum restoration, and educational use only. Not approved for active airworthiness maintenance under FAA 14 CFR § 43.13, EASA Part-M, or equivalent international regulations. Operators of active aircraft must use current, revision-controlled publications from the Type Certificate holder or an authorised distributor.

Living Collections with Free Lifetime Updates — Please review our Legal Notice and Export Notice before purchasing.