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December , 1936 AIRCRAFT ENGINEERIN G 343 Instruction s to Ground Engineers and Private Owner s on Essential Modifications No . 32 of the year 1936 B.2148 Increase in main jet sizes from 700 equipment, in so far as these have yet been Failures having occurred on Monospar S.T.25 t o 800 c.c. for A.V.55A car drafted, are published in Air Ministry Civil engine mounting members, at a point approxi burettors and 800 to 900 c.c. Specifications, copies of which can be purchased mately 2½ in. from the engine attachment of for A.V.55B carburettors. (Only from U.M. Stationery Office at one of the the upper tubular member between the welded for engines operating under partic following addresses :—Adastral House, Kings- gusset plates, it has been decided that a ularly onerous conditions.) way, London, W.C.2 ; 120, George Street, modification to the engine mounting is essential. Edinburgh, 2 ; York Street, Manchester, 1 ; All engines should be checked within 14 A free issue of parts for carrying out the days of the date of this Notice to ensure that 1, St. Andrews Crescent, Cardiff ; 80, Chichester modification, including drawings and instruc carburettors fitted to Mark 1 engines in which Street, Belfast ; or through any bookseller. tions, will be made on application to the Modifications B.1687 and B.1710 have been U p to the present the following thirteen Civil manufacturers, General Aircraft Limited, embodied, or carburettors fitted to Mark IA Soccifications have been issued :— Feltham, Middlesex. Price engines, incorporate 155 c.c. slow running jets. Net Post free Owners of Monospar S.T.25 aeroplanes are Slow running jets which are not of this size are CS . No. s. d . s. d . 1. 0 0 7 advised to carry out this modification at once, t o be removed and replaced by 155 c.c. jets. Altimeters .. .. .. .. 6 0 6 7 bu t in any case it must be effected within one 2. Air speed indicators .. .. .. On all Mark I engines the fuel level in the Pressur e heads for use with air speed month from the date of issue of this Notice. 1 0 1 I float chamber of the carburettor is also to be indicators .. .. .. .. 4 . Engin e speed indicators .. .. 0 6 0 7 I n those cases where it is not practicable to checked to verify that it is 4 t o 5 m.m . below Pressur e gauge s for oil an d fuel systems 0 6 0 7 modify the engine mounting immediately, daily Oil temperature thermometers .. 0 6 0 7 th e top face of the float chamber when tested 7. Radiato r temperature thermometers 0 6 0 7 inspections, which must include removal of with a 7 ft. 6 ins. head of fuel. If the level is 8. 0 6 0 7 Turn indicators .. .. .. th e split cowling bracket, must be carried out 0 6 0 7 no t within these limits, then Modification 9. Magnetic compasses .. .. .. 10. Fire extinguishers .. .. 0 6 0 7 during the period of one month referred to B.1661 must be embodied. After the em Minimu m requirements for electrical 11 . above. If, on inspection, signs of cracking bodiment of the modification, the fuel level apparatu s (other than wireless 0 6 0 7 are detected, the member must be replaced should be checked again under the same head apparatus .. .. .. .. 12. Safet y belts an d harness .. .. 0 0 7 immediately by a new and modified member, of fuel, and adjusted to the above position. 13 . 0 6 0 7 Fire resistance tests .. .. which will be supplied free by the manu Additional specifications are now in prepara A t the next complete overhaul of Mark I facturers. engines with A.V.55A carburettors installed in tion. The issue of additional specifications and Certificates of Airworthiness of the aeroplanes Avro " Cadet " or other aircraft having less tha n amendments to existing specifications will be concerned will be liable to suspension or can a 2 ft. head of fuel at the carburettor, Modifica announced in Notices to Aircraft Owners and cellation if the modification referred to above tion B.1661 must be embodied. After the em Ground Engineers. is not carried out within one month of the date bodiment of the modification the fuel level Certain manufacturers of instruments and of this Notice. Certificates of Airworthiness should be checked with a 7 ft. 6 ins. head of equipment have been authorised to certify that instruments and items of equipment, not will not be renewed and ground engineers must fuel, and adjusted to the position mentioned in necessarily of their own design, comply with not sign Certificates of Safety for Flight in th e preceding paragraph. respect of such aeroplanes after the expiration th e relevant Civil Specification. Following At the next complete overhaul of all Mark I of the aforementioned period, unless the such certification, the items may be used on engines, Modifications B. 1687, B.1707 (Part) modification has been incorporated. civil aircraft provided that inspection and test and B.1710 are to be embodied. ing are certified on a Release Note issued by an September 30, 1936 If A.V.55A carburettors are fitted, the follow Aeronautical Inspection Directorate approved ing jets and chokes should be used : 700 c.c. No . 33 of the year 1936 inspection authority. One copy of the firm's Main, 85 c.c. Power and 155 c.c. Slow Running Experience has shown that there may be " certificate of compliance " is kept in the firm's jets, and 45 m.m . chokes. Existing main jets difficulty in recovery, particularly in " bumpy " records and another copy is forwarded, for varying between 700 and 740 c.cs. need not be weather, if Cierva Autogiros, Types C30P and record purposes only, to the Airworthiness changed. C30A are dived at speeds in excess of about Department, Royal Aircraft Establishment, If A.V.55B carburettors are used, as per 115 m.p.h. Farnborough. mitte d by Modification B.2155, 800 c.c. Main, The speed of these aircraft should not, there Each Civil Specification, except No. 13, 145 c.c. Power and 155 c.c. Slow Running jets fore, be allowed to exceed the above-mentioned contains a clause requiring every item certified and 45 m.m. streamline type chokes should be limit. against tha t specification to b e indelibly marked fitted. Note.—This Notice replaces Notices to Airmen with the maker's name and maker's serial I n those instances where Modification B.2148 Nos. 46 and 72 of 1935, which are being cancelled. number, and recommending that every item is embodied, the main jet sizes as shown above October 20, 1936 should also be marked with the number of the will be increased by 100 c.cs. ; the maximum No . 34 of the year 1936 Civil Specification (e.g., " CS . No. 9 " or 9A, for use with A.V.55A carburettors then being Townend rings are to be removed, within 9B, etc., according to the edition of the 800 c.cs. This modification is only to be one week of the date of this Notice, from specification) against which it has been certified. applied to engines used for particularly onerous Genet Major (7 cyl.) Mark I and Mark IA duties and may result in restricted range of Instrument s and items of equipment for engines in active use in Avro " Cadet " aero th e aircraft. which no Civil Specification has yet been issued planes, in order t o facilitate adequate cooling. will be sent to the Royal Aircraft Establish Modification B.2096 is to be embodied at I n order to improve the carburation of all ment, Farnborough, for test as in the past, and th e next complete overhaul. This will only Genet Major (7 cyl.) Mark I and Mark IA approval will be notified by Air Ministry letter apply to a limited number of Mark IA engines engines, type-approved with Claudel Hobson t o the makers. In certain cases th e information having 1/16 in. holes in the crankshaft rear A.V.55A and A.V.55B carburettors respectively, tha t such approval has been given will be plugs ; these engines were delivered between the modifications below have been introduced :— promulgated by a Notice to Aircraft Owners November, 1935, and June, 1936. and Ground Engineers. Modification A.V.55A carburettors may not be used on Types of instruments and equipment No. Description. Mark IA engines. B.1661 Modified float and needle scat. approved before the issue of the relevant Civil Details of the modifications enumerated in B.1687 New type gland on rear driving Specification may continue to be used without th e second paragraph hereof can be obtained modification after the issue of the Civil shaft. from Messrs. Armstrong Siddeley Motors Ltd., Specification, until further notice. B.1707 Change slow running jets from Parkside, Coventry. (Fart) 300 c.c. to 155 c.c. Types of instruments and equipment duly Unless th e above instructions have been com B.1710 Increase in strength of springs for certified as complying with the appropriate plied with, the Certificate of Airworthiness induction fan gland. Royal Air Force Specification may be used on of the aircraft concerned will be liable to B.2096 Plugging 1/16 in . hole in rear crank civil aircraft provided that authority is first suspension or cancellation. shaft plug. obtained from the Royal Aircraft Establish October 21, 1936 B.2155 Application of A.V.55B carburettors ment. No . 35 of the year 1936 t o Mark I Engines. Design requirements for instruments and November 3, 1936
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Dec 1, 1936
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