Geoffrey Sinclair
Staff Sergeant
- 774
- Sep 30, 2021
More from the Admiralty Fleet Orders, SPC-A Publications | Royal Australian Navy
Year of 1944
335.—Aircraft—Avenger (late Tarpon) (TBF-1, TBM-1 and TBM-3)—Interchangeability of Spare Parts
(N.S. 05660/43.—20 Jan. 1944.)
Avenger (late Tarpon) I (TBF-1) is manufactured by the Grumman Aircraft Corporation and Avenger II (TBM-1) and Avenger III (TBM-3) by General Motors Corporation, Eastern Aircraft Division, and for all practical purposes interchangeability between the products of the two manufacturers should be regarded as non-existent although both manufacturers apply the same part numbers to spares performing equivalent functions. For this reason the composition of individual squadrons will as far as possible be confined to aircraft from one manufacturer, i.e. either TBF or TBM.
2. On receipt from America of airframe spares for these types into store depots in the United Kingdom and abroad, great care must be taken to identify the parts by the type symbol (TBF or TBM) shown on the invoice (form 600) and the manufacturer's tab attached to each part. Spares for the two types must also be stowed and accounted for separately.
3. All demands on store depots for Avenger airframe spares must indicate the Mark number and maker of the aircraft for which the spares are required, in order to avoid the possibility of supply of spares which may prove to be unsuitable. It should be noted, however, that although the majority of the spares are not "interchangeable" as between the aircraft built by the two manufacturers, many will be found to be "replaceable," that is, capable of being fitted, with some adjustment by drilling or reaming, to the aircraft produced by the other manufacturer. Consequently, store depots in dealing with demands for spares for one type which are unavailable in stock should advise the availability (if this should be the case) of the corresponding spares of the other type.
4940.—Aircraft—Avenger (T.B.F.I., T.B.M.I. and T.6.M.3)—Interchangeability of Mainplanes
(N.S. Air/AE . 4222/44.—14 Sep. 1944.)
Mainplanes of Avenger aircraft of the same basic Mark vary as to the forward firing armament and certain other details. All mainplanes of the same basic mark are, however, interchangeable provided they are complete with flaps and ailerons.
2. There is no objection to mainplanes embodying provision for forward firing armament being fitted to an aircraft which already has forward firing armament in the fuselage. In no circumstances, however, should mainplanes not fitted with forward firing arm am en t be installed in an aircraft which has no forward firing armament in the fuselage.
{A.F.O. 335/44.)
455 update of fuels and lubricants
847.— Corsair Aircraft— Colouring of Washers for Identification Purposes
(A.M.R. 14/44.—17 Feb. 1944.)
Washers used in Corsair aircraft will in future be coloured for the purpose of identification of the material. The colouring is carried out after zinc chromate painting and will be applied as detailed in the following table: —
Washers, Tint, (2) Coats Paint
Al. Alloy, Purple, Zinc chromate
Steel, Brilliant Green, Zinc chromate
Brass, None, None
St. Steel, None, None
917 RN flying regulations (38 pages)
1759 manning of air units (8 pages)
2152 RN abbreviations (20 pages)
3427.—Compressibility Effects in High Speed Diving
(A.W.D. 1348/44.—29 Jun. 1944.)
The following is a report of a Technical Note issued by the Bureau of Aeronautics, Navy Department, Washington :—
It describes control effects that are associated with compressibility phenomena and suggests certain cautions that may aid in avoiding or reducing the hazard therefrom. This information is to be brought to the attention of all pilots, including those under training at Naval air stations.
2. In recent years the attainable airspeeds of many service types have increased to a point where unusual or unexpected flight characteristics sometimes develop. These effects may take the form of a sudden change in trim, a change in stability about any of the airplane's axes, buffeting or vibration, and the formation of vapour sheets. They may be expected at high speeds, particularly at altitude and under accelerated conditions.
3. These effects are attributed to compressibility. Aerodynamic theory, based on the assumption that air is an incompressible fluid, has been commonly and successfully applied in the determination o f magnitudes and distributions of air loads during the era in which possible dive speeds were comparatively low and the actual effects of compressibility were negligible from a practical standpoint. As airspeeds increase, however, certain predictable effects of the compressible nature of air rapidly become of considerable importance. With further increase of air speeds, approaching the speed of sound in air, certain phenomena occur which are difficult of prediction or evaluation. The term "compressibility" has become associated with these latter phenomena which are not completely understood and for which no practicable or thoroughly accurate corrections are yet available.
4. Some of these effects may be visualised as resulting from discontinuities in the air flow about an airplane, or "shock waves". Shock waves do not form on slowly moving bodies because the air flow adjusts itself to pass over the object as smoothly as possible with only small changes in the pressure and density of the air. Shock waves do, however, form on high speed bodies because the air cannot adjust itself to pass the body without radical changes in pressure and density and the introduction of what have been termed "compressibility effects". The shock wave phenomenon is comparable to the water wave that forms at the bow of a ship. I f the ship is moving rapidly, the water cannot follow the smooth contours of the ship and, instead, piles up as a bow wave.
5. The appearance of shook waves and other compressibility effects in air depend on the ratio of the speed of the object to the speed of sound. This ratio, which is called the Mach Number, is based on true air speed. The speed of sound decreases with altitude, and i f the indicated speed remains constant, the true air speed increases with altitude. Hence, the Mach Number increases rapidly with altitude for constant indicated air speed. An indicated speed of 250 knots corresponds to a Mach Number of 0 • 38 at sea level, but at 35,000 feet this same indicated speed gives a Mach Number of 0-74. This difference is considerable and results in compressibility effects being much more easily encountered at high altitudes than at sea level.
6. As a result of the rearrangement of the airflow when speeds are reached at which shock waves occur, control surfaces may be expected to have varying degrees of effectiveness and the airplane may be expected to change its stability characteristics. These changes are not predictable with accuracy either from analysis or from conventional wind tunnel tests. Flight test is the only means of reliable exploration of these effects and this method may involve undue hazard to the test pilot unless a systematic programme with careful instrumentation is undertaken.
7. Although service types have normal characteristics and no unusual handling qualities may be expected in accomplishing the missions to which they have been assigned, some o f them may easily be dived through inadvertence or combat necessity to speeds well above those for which their handling characteristics are thoroughly known. I f such a condition should arise, changes in behaviour may occur. Those most likely to occur are listed and described below in order that pilots may recognize them more quickly and thus be able to take more effective steps to counteract or to avoid them :—
(а) Buffeting.—This is one of the most common disturbances associated with high speed flying. It is aggravated by partially open cowl flaps or intercooler doors, damaged or bent fairings, by movements of control surfaces, especially when the leading edges of these control surfaces are sharp, and by other factors that would cause turbulence or irregular air flow. Although buffeting may occur at low speed, it will be more pronounced at high speed. If a severe buffet develops, immediate action to decrease the applied acceleration will probably be more effective in reducing the buffet intensity than a reduction in speed. However, both should be reduced as soon as practicable.
(b) Aileron Snatch.—Ailerons, particularly those with sharp leading edges, may snatch at high speeds. Aileron snatch is a movement, with or without oscillation, of the control stick, caused by air striking or flowing around the leading edge as the aileron is being deflected. In high speed dives the pilot should keep a firm hold on the stick and keep the stick neutral so far as practicable.
(c) High Stick Force.—In high altitude dives with the true speed greater than about three-quarters of the speed of sound, the pilot may find that he cannot hold the airplane in the dive. On the other hand, the opposite effect may occur with the pilot unable to exert sufficient force on the stick to pull the airplane out of the dive. Inability to pull the airplane out of the dive may be due either to a very large diving moment attended by a loss of lift on the wing, which requires a much greater elevator load at high altitudes for a pull-out than the pilot can apply, or it may result from a redistribution of tail loads which increases elevator hinge moments. At lower altitudes, where the true speed becomes less than about three-quarters of the speed of sound, the pilot will probably be able to pull out with normal stick forces.
(d) Loss in Effectiveness of Elevator Trim Tab.—The elevator tab keeps its normal effectiveness up to a true air speed of approximately three quarters of the speed of sound. Beyond this point the elevator tab often becomes ineffective so far as pull-outs are concerned. If this condition is found to exist, the elevator trim tab should always be restored to its initial position, because the tab will regain its original effectiveness and cause a very abrupt pull-out when the airplane reaches lower altitudes where the true speed is less than about three quarters of the speed of sound.
(e) Formation of Vapor Sheets.—Although of no particular significance as regards control effectiveness, the formation of vapor sheets is an interesting phenomenon which evidences high speed. It is a visible indication, in humid weather, of local high velocity of the air over the wing. With increase of speed or "g" the thickness or height of the sheet can be seen to vary. The formation of a thin vapor sheet may or may not be accompanied by other compressibility effects.
8. Certain cautions have been suggested by test pilots and others to avoid compressibility effects. They may not, however, apply in all cases. Each airplane may be expected to have its own peculiarities at high speed at altitude. Pilots who experience any of these effects should make reports of their experiences, including as much thoroughly factual information as possible. The cautions commonly recommended to avoid or to minimize compressibility effects are the following :—
(а) Return 'the elevator trim tab to its initial position if it is found to be ineffective in reducing control forces. As explained in paragraph 7 (d), failure to do so may result in a sharp pull-out when the tab regains its effectiveness.
(b) Attempts have been made to slow down an airplane in a high-speed dive by yawing it. Such attempts have not only failed but have proved dangerous because the dive angle was greatly steepened when the airplane was yawed. Excessive yawing has also resulted in failures in the tail surfaces and in buckled fuselages. Therefore, efforts should be made to prevent a diving airplane from yawing when at high speed and high altitude.
(c) Some pilots of single-engine airplanes have experienced a considerable increase in diving angle when the power was cut in high-speed dives. Since an increase in diving angle greatly increases the difficulty of pull-out from a dive, the throttle should not be cut or the r.p.m. control changed during a high-speed dive except with great care.
(d) Avoid over-controlling by being alert to detect a change or reversal of control force. Unnecessary control surface displacement may provide the disturbance necessary to produce a compressibility effect. For example, at high speeds, rocking the wings may stall first one wing and then the other.
(e) When practicable, dives to high speed should be made as shallow as possible, so that if compressibility effects do present themselves, speed and acceleration will be under better control.
(f) Avoid high-speed accelerated stalls at altitude.
9. As planes become capable of attaining higher and higher speeds, pilots will become more and more familiar with compressibility effects and the peculiarities associated with the high-speed performance of individual airplanes. Good piloting technique requires avoidance of these effects much the same as it requires the avoidance of stalls. The approach of a stall is associated with certain sensations which a pilot normally recognizes and avoids. In the same way, pilots should learn to recognize the approach of compressibility effects by certain of the characteristics described in this technical note, or others which experience will indicate to be present.
5968, preserving aircraft and engines. (12 pages)
6124 engine and airframe publications. (12 pages)
Year of 1944
335.—Aircraft—Avenger (late Tarpon) (TBF-1, TBM-1 and TBM-3)—Interchangeability of Spare Parts
(N.S. 05660/43.—20 Jan. 1944.)
Avenger (late Tarpon) I (TBF-1) is manufactured by the Grumman Aircraft Corporation and Avenger II (TBM-1) and Avenger III (TBM-3) by General Motors Corporation, Eastern Aircraft Division, and for all practical purposes interchangeability between the products of the two manufacturers should be regarded as non-existent although both manufacturers apply the same part numbers to spares performing equivalent functions. For this reason the composition of individual squadrons will as far as possible be confined to aircraft from one manufacturer, i.e. either TBF or TBM.
2. On receipt from America of airframe spares for these types into store depots in the United Kingdom and abroad, great care must be taken to identify the parts by the type symbol (TBF or TBM) shown on the invoice (form 600) and the manufacturer's tab attached to each part. Spares for the two types must also be stowed and accounted for separately.
3. All demands on store depots for Avenger airframe spares must indicate the Mark number and maker of the aircraft for which the spares are required, in order to avoid the possibility of supply of spares which may prove to be unsuitable. It should be noted, however, that although the majority of the spares are not "interchangeable" as between the aircraft built by the two manufacturers, many will be found to be "replaceable," that is, capable of being fitted, with some adjustment by drilling or reaming, to the aircraft produced by the other manufacturer. Consequently, store depots in dealing with demands for spares for one type which are unavailable in stock should advise the availability (if this should be the case) of the corresponding spares of the other type.
4940.—Aircraft—Avenger (T.B.F.I., T.B.M.I. and T.6.M.3)—Interchangeability of Mainplanes
(N.S. Air/AE . 4222/44.—14 Sep. 1944.)
Mainplanes of Avenger aircraft of the same basic Mark vary as to the forward firing armament and certain other details. All mainplanes of the same basic mark are, however, interchangeable provided they are complete with flaps and ailerons.
2. There is no objection to mainplanes embodying provision for forward firing armament being fitted to an aircraft which already has forward firing armament in the fuselage. In no circumstances, however, should mainplanes not fitted with forward firing arm am en t be installed in an aircraft which has no forward firing armament in the fuselage.
{A.F.O. 335/44.)
455 update of fuels and lubricants
847.— Corsair Aircraft— Colouring of Washers for Identification Purposes
(A.M.R. 14/44.—17 Feb. 1944.)
Washers used in Corsair aircraft will in future be coloured for the purpose of identification of the material. The colouring is carried out after zinc chromate painting and will be applied as detailed in the following table: —
Washers, Tint, (2) Coats Paint
Al. Alloy, Purple, Zinc chromate
Steel, Brilliant Green, Zinc chromate
Brass, None, None
St. Steel, None, None
917 RN flying regulations (38 pages)
1759 manning of air units (8 pages)
2152 RN abbreviations (20 pages)
3427.—Compressibility Effects in High Speed Diving
(A.W.D. 1348/44.—29 Jun. 1944.)
The following is a report of a Technical Note issued by the Bureau of Aeronautics, Navy Department, Washington :—
It describes control effects that are associated with compressibility phenomena and suggests certain cautions that may aid in avoiding or reducing the hazard therefrom. This information is to be brought to the attention of all pilots, including those under training at Naval air stations.
2. In recent years the attainable airspeeds of many service types have increased to a point where unusual or unexpected flight characteristics sometimes develop. These effects may take the form of a sudden change in trim, a change in stability about any of the airplane's axes, buffeting or vibration, and the formation of vapour sheets. They may be expected at high speeds, particularly at altitude and under accelerated conditions.
3. These effects are attributed to compressibility. Aerodynamic theory, based on the assumption that air is an incompressible fluid, has been commonly and successfully applied in the determination o f magnitudes and distributions of air loads during the era in which possible dive speeds were comparatively low and the actual effects of compressibility were negligible from a practical standpoint. As airspeeds increase, however, certain predictable effects of the compressible nature of air rapidly become of considerable importance. With further increase of air speeds, approaching the speed of sound in air, certain phenomena occur which are difficult of prediction or evaluation. The term "compressibility" has become associated with these latter phenomena which are not completely understood and for which no practicable or thoroughly accurate corrections are yet available.
4. Some of these effects may be visualised as resulting from discontinuities in the air flow about an airplane, or "shock waves". Shock waves do not form on slowly moving bodies because the air flow adjusts itself to pass over the object as smoothly as possible with only small changes in the pressure and density of the air. Shock waves do, however, form on high speed bodies because the air cannot adjust itself to pass the body without radical changes in pressure and density and the introduction of what have been termed "compressibility effects". The shock wave phenomenon is comparable to the water wave that forms at the bow of a ship. I f the ship is moving rapidly, the water cannot follow the smooth contours of the ship and, instead, piles up as a bow wave.
5. The appearance of shook waves and other compressibility effects in air depend on the ratio of the speed of the object to the speed of sound. This ratio, which is called the Mach Number, is based on true air speed. The speed of sound decreases with altitude, and i f the indicated speed remains constant, the true air speed increases with altitude. Hence, the Mach Number increases rapidly with altitude for constant indicated air speed. An indicated speed of 250 knots corresponds to a Mach Number of 0 • 38 at sea level, but at 35,000 feet this same indicated speed gives a Mach Number of 0-74. This difference is considerable and results in compressibility effects being much more easily encountered at high altitudes than at sea level.
6. As a result of the rearrangement of the airflow when speeds are reached at which shock waves occur, control surfaces may be expected to have varying degrees of effectiveness and the airplane may be expected to change its stability characteristics. These changes are not predictable with accuracy either from analysis or from conventional wind tunnel tests. Flight test is the only means of reliable exploration of these effects and this method may involve undue hazard to the test pilot unless a systematic programme with careful instrumentation is undertaken.
7. Although service types have normal characteristics and no unusual handling qualities may be expected in accomplishing the missions to which they have been assigned, some o f them may easily be dived through inadvertence or combat necessity to speeds well above those for which their handling characteristics are thoroughly known. I f such a condition should arise, changes in behaviour may occur. Those most likely to occur are listed and described below in order that pilots may recognize them more quickly and thus be able to take more effective steps to counteract or to avoid them :—
(а) Buffeting.—This is one of the most common disturbances associated with high speed flying. It is aggravated by partially open cowl flaps or intercooler doors, damaged or bent fairings, by movements of control surfaces, especially when the leading edges of these control surfaces are sharp, and by other factors that would cause turbulence or irregular air flow. Although buffeting may occur at low speed, it will be more pronounced at high speed. If a severe buffet develops, immediate action to decrease the applied acceleration will probably be more effective in reducing the buffet intensity than a reduction in speed. However, both should be reduced as soon as practicable.
(b) Aileron Snatch.—Ailerons, particularly those with sharp leading edges, may snatch at high speeds. Aileron snatch is a movement, with or without oscillation, of the control stick, caused by air striking or flowing around the leading edge as the aileron is being deflected. In high speed dives the pilot should keep a firm hold on the stick and keep the stick neutral so far as practicable.
(c) High Stick Force.—In high altitude dives with the true speed greater than about three-quarters of the speed of sound, the pilot may find that he cannot hold the airplane in the dive. On the other hand, the opposite effect may occur with the pilot unable to exert sufficient force on the stick to pull the airplane out of the dive. Inability to pull the airplane out of the dive may be due either to a very large diving moment attended by a loss of lift on the wing, which requires a much greater elevator load at high altitudes for a pull-out than the pilot can apply, or it may result from a redistribution of tail loads which increases elevator hinge moments. At lower altitudes, where the true speed becomes less than about three-quarters of the speed of sound, the pilot will probably be able to pull out with normal stick forces.
(d) Loss in Effectiveness of Elevator Trim Tab.—The elevator tab keeps its normal effectiveness up to a true air speed of approximately three quarters of the speed of sound. Beyond this point the elevator tab often becomes ineffective so far as pull-outs are concerned. If this condition is found to exist, the elevator trim tab should always be restored to its initial position, because the tab will regain its original effectiveness and cause a very abrupt pull-out when the airplane reaches lower altitudes where the true speed is less than about three quarters of the speed of sound.
(e) Formation of Vapor Sheets.—Although of no particular significance as regards control effectiveness, the formation of vapor sheets is an interesting phenomenon which evidences high speed. It is a visible indication, in humid weather, of local high velocity of the air over the wing. With increase of speed or "g" the thickness or height of the sheet can be seen to vary. The formation of a thin vapor sheet may or may not be accompanied by other compressibility effects.
8. Certain cautions have been suggested by test pilots and others to avoid compressibility effects. They may not, however, apply in all cases. Each airplane may be expected to have its own peculiarities at high speed at altitude. Pilots who experience any of these effects should make reports of their experiences, including as much thoroughly factual information as possible. The cautions commonly recommended to avoid or to minimize compressibility effects are the following :—
(а) Return 'the elevator trim tab to its initial position if it is found to be ineffective in reducing control forces. As explained in paragraph 7 (d), failure to do so may result in a sharp pull-out when the tab regains its effectiveness.
(b) Attempts have been made to slow down an airplane in a high-speed dive by yawing it. Such attempts have not only failed but have proved dangerous because the dive angle was greatly steepened when the airplane was yawed. Excessive yawing has also resulted in failures in the tail surfaces and in buckled fuselages. Therefore, efforts should be made to prevent a diving airplane from yawing when at high speed and high altitude.
(c) Some pilots of single-engine airplanes have experienced a considerable increase in diving angle when the power was cut in high-speed dives. Since an increase in diving angle greatly increases the difficulty of pull-out from a dive, the throttle should not be cut or the r.p.m. control changed during a high-speed dive except with great care.
(d) Avoid over-controlling by being alert to detect a change or reversal of control force. Unnecessary control surface displacement may provide the disturbance necessary to produce a compressibility effect. For example, at high speeds, rocking the wings may stall first one wing and then the other.
(e) When practicable, dives to high speed should be made as shallow as possible, so that if compressibility effects do present themselves, speed and acceleration will be under better control.
(f) Avoid high-speed accelerated stalls at altitude.
9. As planes become capable of attaining higher and higher speeds, pilots will become more and more familiar with compressibility effects and the peculiarities associated with the high-speed performance of individual airplanes. Good piloting technique requires avoidance of these effects much the same as it requires the avoidance of stalls. The approach of a stall is associated with certain sensations which a pilot normally recognizes and avoids. In the same way, pilots should learn to recognize the approach of compressibility effects by certain of the characteristics described in this technical note, or others which experience will indicate to be present.
5968, preserving aircraft and engines. (12 pages)
6124 engine and airframe publications. (12 pages)
