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Flight on Asymmetric Power

Flight on Asymmetric Power CORRESPONDENCE The Author's Reply I am much obliged to Mr Beverley for his letter, which does a great deal towards clarifying the To the Editor: by the applicant at which, for the purpose of points applicable to civil aircraft. As a Service determining the accelerate stop distance and the pilot, I have not probed too deeply into the DEAR SIR, take-off path, failure of the critical engine is I.C.A.O. requirements, but it would appear from Flight-Sergeant Wright's article on 'Flight on assumed to occur. If this point is located so that Mr Beverley's letter that there is some difference asymmetrical engine power', published in your the airspeed is less than the take-off safety speed in the interpretation of the term SAFETY SPEED; December issue, dealt with the subject primarily it must be demonstrated that in the event of sud­ since we in the Service are concerned only with from the point of view of military practice and den failure of the critical engine at all speeds military aircraft, we are not required to conform service aircraft. On the civil side, the ability of down to the lowest speed corresponding with the to any requirements regarding the single-engined transport aeroplanes to perform satisfactorily in critical point, the aeroplane is controllable satis­ performance of a given aircraft. The Service the event of engine failure at the critical point at factorily and that the take-off can be continued specification for an aircraft no doubt lays down take-off has for some time not only been a design and safely using normal piloting skill without: certain limits to which the prototype must con­ requirement which has to be met as a condition form before acceptance, but in normal operation (a) Reducing the thrust of the remaining engines. of certification for new aeroplanes, but also an a Safety Speed derived from these specifications international operating regulation. It would ap­ (b) Encountering characteristics which would re­ is laid down in Pilots' Notes for the type. pear from your leading article that these facts are sult in unsatisfactory controllability on wet The pilot is then instructed to use this Safety not generally known. runways. Speed thus: The I.C.A.O. regulations on the subject require The I.C.A.O. Operating Regulations require the If an engine failure occurs during the take-off, the applicant for a Certificate of Airworthiness operator to ensure that the accelerate stop dis­ two alternatives appear: for a multi-engined civil transport aircraft to tance and the distance to 50 ft. scheduled in the 1. If he has attained the Safety Speed quoted in schedule the following information in the aero­ Flight Manual for the relevant conditions of Pilots' Notes for the conditions in force, he plane Flight Manual: wind, temperature, altitude and aircraft weight will continue the take-off and carry out do not exceed the aerodrome distances available. the emergency drills laid down. (a) The Accelerate Stop Distance It is the speed associated with the critical This is the distance required to reach the 2. If he has not attained this speed, he must point that Mr Hufton referred to in his article in critical point from a standing start and, assuming carry out a crash landing ahead to the best the Royal Aeronautical Society's Journal on the critical engine to fail suddenly at this point, to of his ability. July, 1947, and which is criticized by Flight- stop if a landplane or to bring the aeroplane to a Sergeant Wright in section 3 of his article. In view of the fact that the Service Safety Speed speed of approximately three miles per hour if a The I.C.A.O.Airworthiness requirements, which provides quite a large margin of speed above the seaplane. contain similar requirements concerning en route critical speed for the conditions, it is felt that the and landing performance with an engine in­ average pilot is quite safe in applying the two (b) The Distance to reach 50 ft. operative, have been incorporated in the air­ rules noted above, which is one of the reasons This is the distance required to reach a height worthiness requirements of many nations. They why the Safety Speed is so called. It is also of 50 ft. from a standing start with the critical were introduced into British Civil Airworthiness manifestly impossible to call the speed at the engine becoming inoperative at the critical point Requirements as long ago as January 1, 1948, 'critical point' the Safety Speed, since Mr Beverley —the speed at the 50 ft. point being not less than and similar requirements have been in force in the states that this point can come at a point below take-off safety speed. United States for a much longer period. This the aircraft safety speed, but should it do so, it emphasis on the performance of the aircraft in (c) Take-off Safety Speed must still be possible to climb the aircraft away. the event of engine failure at take-off has played It is my opinion that something could and This is defined as an air-speed selected by the a most important part in the design of such air­ should be done towards standardizing these terms applicant at which the aeroplane shall be able to craft as the Constellation, the DC6, the Convair achieve a specified rate of climb with one engine to avoid confusion. Service pilots can at least liner, the Martin 202, the Ambassador, the inoperative, but which must not be less than: console themselves by reflecting that their case is Viscount and the Marathon. the simple one in which the decision is made by (i) 1 ·2 VSI for aeroplanes with two engines, or reference to air speed alone. 1·15 for aeroplanes having more than two Yours faithfully, Yours faithfully, engines. ERIC L. BEVERLEY, E. WRIGHT (ii) 1·1 VMC for all aeroplanes. D.F.C. , A.R.Ae.S. Some of the I.C.A.O. requirements were dealt with For the purposes of establishing these three 25 St Thomas's Mansions, Stangate, S.E.1 in the article by Mr K. G. Wilkinson on pp. 36-39 requirements, the critical point is a point selected January 9, 1951 of our last issue.—EDITOR March 1951 85 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Aircraft Engineering and Aerospace Technology Emerald Publishing

Flight on Asymmetric Power

Aircraft Engineering and Aerospace Technology , Volume 23 (3): 1 – Mar 1, 1951

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Publisher
Emerald Publishing
Copyright
Copyright © Emerald Group Publishing Limited
ISSN
0002-2667
DOI
10.1108/eb032012
Publisher site
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Abstract

CORRESPONDENCE The Author's Reply I am much obliged to Mr Beverley for his letter, which does a great deal towards clarifying the To the Editor: by the applicant at which, for the purpose of points applicable to civil aircraft. As a Service determining the accelerate stop distance and the pilot, I have not probed too deeply into the DEAR SIR, take-off path, failure of the critical engine is I.C.A.O. requirements, but it would appear from Flight-Sergeant Wright's article on 'Flight on assumed to occur. If this point is located so that Mr Beverley's letter that there is some difference asymmetrical engine power', published in your the airspeed is less than the take-off safety speed in the interpretation of the term SAFETY SPEED; December issue, dealt with the subject primarily it must be demonstrated that in the event of sud­ since we in the Service are concerned only with from the point of view of military practice and den failure of the critical engine at all speeds military aircraft, we are not required to conform service aircraft. On the civil side, the ability of down to the lowest speed corresponding with the to any requirements regarding the single-engined transport aeroplanes to perform satisfactorily in critical point, the aeroplane is controllable satis­ performance of a given aircraft. The Service the event of engine failure at the critical point at factorily and that the take-off can be continued specification for an aircraft no doubt lays down take-off has for some time not only been a design and safely using normal piloting skill without: certain limits to which the prototype must con­ requirement which has to be met as a condition form before acceptance, but in normal operation (a) Reducing the thrust of the remaining engines. of certification for new aeroplanes, but also an a Safety Speed derived from these specifications international operating regulation. It would ap­ (b) Encountering characteristics which would re­ is laid down in Pilots' Notes for the type. pear from your leading article that these facts are sult in unsatisfactory controllability on wet The pilot is then instructed to use this Safety not generally known. runways. Speed thus: The I.C.A.O. regulations on the subject require The I.C.A.O. Operating Regulations require the If an engine failure occurs during the take-off, the applicant for a Certificate of Airworthiness operator to ensure that the accelerate stop dis­ two alternatives appear: for a multi-engined civil transport aircraft to tance and the distance to 50 ft. scheduled in the 1. If he has attained the Safety Speed quoted in schedule the following information in the aero­ Flight Manual for the relevant conditions of Pilots' Notes for the conditions in force, he plane Flight Manual: wind, temperature, altitude and aircraft weight will continue the take-off and carry out do not exceed the aerodrome distances available. the emergency drills laid down. (a) The Accelerate Stop Distance It is the speed associated with the critical This is the distance required to reach the 2. If he has not attained this speed, he must point that Mr Hufton referred to in his article in critical point from a standing start and, assuming carry out a crash landing ahead to the best the Royal Aeronautical Society's Journal on the critical engine to fail suddenly at this point, to of his ability. July, 1947, and which is criticized by Flight- stop if a landplane or to bring the aeroplane to a Sergeant Wright in section 3 of his article. In view of the fact that the Service Safety Speed speed of approximately three miles per hour if a The I.C.A.O.Airworthiness requirements, which provides quite a large margin of speed above the seaplane. contain similar requirements concerning en route critical speed for the conditions, it is felt that the and landing performance with an engine in­ average pilot is quite safe in applying the two (b) The Distance to reach 50 ft. operative, have been incorporated in the air­ rules noted above, which is one of the reasons This is the distance required to reach a height worthiness requirements of many nations. They why the Safety Speed is so called. It is also of 50 ft. from a standing start with the critical were introduced into British Civil Airworthiness manifestly impossible to call the speed at the engine becoming inoperative at the critical point Requirements as long ago as January 1, 1948, 'critical point' the Safety Speed, since Mr Beverley —the speed at the 50 ft. point being not less than and similar requirements have been in force in the states that this point can come at a point below take-off safety speed. United States for a much longer period. This the aircraft safety speed, but should it do so, it emphasis on the performance of the aircraft in (c) Take-off Safety Speed must still be possible to climb the aircraft away. the event of engine failure at take-off has played It is my opinion that something could and This is defined as an air-speed selected by the a most important part in the design of such air­ should be done towards standardizing these terms applicant at which the aeroplane shall be able to craft as the Constellation, the DC6, the Convair achieve a specified rate of climb with one engine to avoid confusion. Service pilots can at least liner, the Martin 202, the Ambassador, the inoperative, but which must not be less than: console themselves by reflecting that their case is Viscount and the Marathon. the simple one in which the decision is made by (i) 1 ·2 VSI for aeroplanes with two engines, or reference to air speed alone. 1·15 for aeroplanes having more than two Yours faithfully, Yours faithfully, engines. ERIC L. BEVERLEY, E. WRIGHT (ii) 1·1 VMC for all aeroplanes. D.F.C. , A.R.Ae.S. Some of the I.C.A.O. requirements were dealt with For the purposes of establishing these three 25 St Thomas's Mansions, Stangate, S.E.1 in the article by Mr K. G. Wilkinson on pp. 36-39 requirements, the critical point is a point selected January 9, 1951 of our last issue.—EDITOR March 1951 85

Journal

Aircraft Engineering and Aerospace TechnologyEmerald Publishing

Published: Mar 1, 1951

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