Operational Order No. 10

Sunday, 12 October 1941

1941-10-12

S E C R E T. 21 SQUADRON OPERATIONAL ORDER NO. 10. COPY NO...4.... ( Ref: 261 Wing Operational Order No. "A" 90. ) DATE: 12.10.41. MAP REF: Tobruk 1:500000 and Target Map D./8 LIST OF APPENDICES. "B" INFORMATION. Derna L.G. is 5 miles due South of Derna. It is situated on the escarpment, some 900 ft. above sea level. It is the principal advanced base of the G.A.F. and I.A.F. and usually has a large number of well dispersed aircraft on both the L.G. and Satellite. Briefing by O. C. and S. I. O. and explanation of Target map D/8. INTENTION. (1) High level attack by 9 aircraft at the following heights. 16000ft. 16500 ft. and 17000 ft. (2) Test of fuel consumption under service and formation conditions. EXECUTION. (a) List of Aircraft and crews see appendix "B" (b) o/c "A" Flight will provide 3 Aircraft. o/c "B" Flight will provide 6 Aircraft. (c) Time of starting up 1015 hours. (d) Time of Take off 1030 hours. (e) Formation: Squadron Flights, line astern. [strike-through] Take off. [/strike-through] Squadron will climb quickly to 15000 ft., and then cruise at 2000 r.p.m. at 24" boost. (f) Route: Sea, on the courses indicated in 261 Wing Operation Order No. "A" 90. Any deviation to be recorded exactly by Observers. (g) Approach: When 50 miles from Target, go into rich and climb to 20000 ft. 10 miles this side ( unless Fighters are seen) dive to 16000 ft., 16500 ft., and 17000 ft. (h) After release: Close up immediately, lose height at 400 ft. per minute and open throttles. ( Suggest leader keeps r.p.m. at 2200.) Descend at this rate and speed, to 10000 ft., and carry on, on lean. If fuel guages register less than 45 gallons when near Sidi Barrani, Aircraft must land and refuel. Other aircraft will come on and land here as quickly as possible. (i) Immediately engines are stopped, Engineer Officer must check consumption of each Aircraft and hand in report. (j) Photography: 6 cameras. (k) Landing order: Order of take off. ADMINISTRATIVE ARRANGEMENTS. (a) All aircraft must carry full capacity fuel and oil. (b) All magazines and pans to be fully loaded. (c) Each aircraft will carry full bomb load i.e. 8 X 250 lbs. Fuse N. (inst.) (d) All necessary desert equipment. INTER COMMUNICATION. W/T Officer. ACKNOWLEDGE. [handwritten signature] L Saunders. Lt. For O. C. 21 SQUADRON.

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Original page(s): 75

Transcriber's Notes

Phase 2: Technical Expansion (The "Transcriber's Notes") Glossary of Terms * 21 SQUADRON S.A.A.F.: No. 21 Squadron, South African Air Force. During this phase of the Western Desert Campaign, the unit operated the Martin Maryland, a twin-engine medium bomber utilized for high-altitude horizontal bombing. * 261 WING: The higher tactical formation (R.A.F. Wing) to which 21 Squadron was attached for operational coordination. * FUSE N. (inst.): Nose Fuse (instantaneous). These detonators were set to initiate the high-explosive charge immediately upon contact with the surface, optimized for destroying aircraft and thin-skinned vehicles on the ground. * G.A.F. / I.A.F.: German Air Force (Luftwaffe) and Italian Air Force (Regia Aeronautica). * L.G. / SATELLITE: Landing Ground and its secondary/auxiliary airfield. Derna L.G. was a critical Axis air hub. * O. C. / S. I. O.: Officer Commanding and Squadron Intelligence Officer. * R.P.M. / BOOST: Revolutions Per Minute and manifold pressure (measured in inches of mercury). These represent the power settings for the Maryland's Pratt & Whitney Twin Wasp engines. * W/T: Wireless Telegraphy, the aircraft's radio communications managed by the Operator Gunner. Operational Context Operational Order No. 10, dated 12 October 1941, initiates a high-altitude strike against Derna Landing Ground. Strategically, Derna was the "principal advanced base" for Axis air operations in Cyrenaica, housing significant concentrations of Luftwaffe and Regia Aeronautica aircraft. Neutralizing Axis air power at Derna was essential for the Desert Air Force to achieve the air superiority required for the upcoming Operation Crusader, the Allied winter offensive to relieve Tobruk. This mission carries a dual purpose: a combat strike and a formal test of fuel consumption under combat load. This technical evaluation was likely prompted by the long-range nature of the flight to Derna, which pushed the operational radius of the Marylands and necessitated precise fuel management, including a contingency landing at Sidi Barrani if reserves fell below 45 gallons. Execution Constraints The mission profile involves 9 aircraft attacking from staggered altitudes of 16,000, 16,500, and 17,000 feet to saturate the target while providing vertical separation. The approach is planned entirely over the Sea to avoid detection by land-based Axis observers and anti-aircraft batteries. A significant technical constraint is the engine management directive: crews were to climb quickly to 15,000 feet and then cruise at specific fuel-efficient settings (2000 r.p.m. at 24" boost). The approach required a climb to 20,000 feet 50 miles from the target, switching to a "rich" fuel mixture for maximum power, followed by a tactical dive to bombing heights. Post-release, the formation was to descend at 400 feet per minute while "opening throttles" to maximize speed for egress, finally leveling out at 10,000 feet on a "lean" mixture to conserve fuel for the return leg. The handwritten strike-through in the Execution section ("Take off.") clarifies that the climbing instructions apply to the squadron as a whole once airborne. This order, signed by Lt. L. Saunders, represents a highly disciplined tactical and technical exercise in long-range interdiction. 77 Phase 1: Verification & Extraction Identity Check: 12.10.41.