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C-CVL22Class/S38(638-812) EN28/A2-11 NAVY DEPARTMENT BUREAU OF SHIPS WASHINGTON,D.C.  Copy dh 30 July 1943 CONFIDENTIAL RESTRICTED From: The Chief of the Bureau af Ships. To: The Commander, Service Force, Pacific fleet. The Commander, Service Force, Atlantic Fleet The Commander, Air Force, Pacific Fleet The Commander, Air Force, Atlantic Fleet. The Commanding Officers, all CVL22Class.   Subject:  CVL22Class - Hanger Deck Plane Warm-Ups - Recommended Procedure.      1.   The Bureau of Ships and Naval Medical Research Institute have recently completed tests on one of the subject aircraft carriers to determine the conditions under which planes may be warmed up in the hanger(SIC) without building up concentration of carbon monoxide that will endanger personnel. The unrestricted warming up of planes in the hanger(SIC) might well create a real hazard, as from 10 to 12% carbon monoxide is found in engine exhaust gases and the maximum concentration to which a person may be exposed for a twenty-minute period - provided there are at least eight hours between warm-ups - is 12 parts of CO in 10,000 parts of air, or 0.12%.      2.   In order to simulate actual operating conditions, two arrangements of planes were used for the tests; first with eight F6F's and four TBE-l's (SIC - TBF-1's)all with their propellers facing forward, and, second, with three F6F's and eight SBD's. During the second test the F6F's propellers faced forward but the SBD's, whose wings cannot be folded, were so arranged that although their fusilages (SIC)were not parallel to the of the ships their propellers were all forward.      3.   The test proved if both elevators are lowered three feet advantage can and must bs taken of the large quantity of air moved by the propellers to induce a flow of air through the hangar space of sufficient quantity to dilute the carbon monoxide in the exhaust gas to safe values, provided the propeller slip streams supplement each other.      RECOMMENDED SAFE OPERATING PROCEDURE.      4.   Any combination of SBD's, TBFl's or F6F's may be warmed up on the hangar deck, provided:       a.    The planes are so arranged that propeller slip streams supplement each other to a maximum degree.         b. Both elevators must be lowered three feet.   - 1 -

C-CVL22Class/S38(638-812) EN28/A2-11 CONFIDENTIAL       c.    The warm-up period per plane should not exceed 10 minutes; however, when all planes cannot be started simultaneously, the total warm-up period for the group should not exceed 20 minutes.         e.    Condition "Able" should be set on the hangar deck whenever practicable during any warm-up or run-in period to reduce the quantity of exhaust gases that are forced down to the second deck through open accesses.         e.    The second deck should be ventilated for at least 10 minutes after the plane warm-up period, to wash out any accumulated carbon monoxide.      5.   Flying personnel should be kept off the hangar deck during warm-up periods.      6.   To obtain maximum lighttightness under conditions of paragraph 4(b), the spaces between the flight deck beams at the after end of the forward elevator and the forward end of the after elevator should be blocked. In addition, light reflecting surfaces at the elevator openings should be painted black from the flight deck down for a distance of about six feet.      7.   Ready room ventilation systems should be set for maximum replenishment air during warm-up periods to minimize the possibility of carbon monoxide concentration in the ready rooms.      8.   During daytime warm-up all curtains and weather access of the hangar deck should be opened as an additional precaution.      9.   During the two hour run-in for newly installed engines two TBFl's or two F6F's may be turned over, provided both elevators are lowered three feet. The planes should be located aft with their propellers forward so that a minimum of the hangar is contaminated by carbon monoxide.     10.   The test results indicated that if all of the above provisions are complied with the carbon monoxide concentration will not build up to dangerous values in any part of the ship and the concentration in the ready room and compartments below the hangar deck will have no harmful effect on flying personnel.   Standard Distribution List: List la, k, l,o,p Copy to: BUAER -2- J. J. Broshek By direction

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