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Thread: Extractor function

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    Default Extractor function

    Despite searching I have been unable to establish exactly what an extractor is, my reference is to an early Whiltley 1940 the ORB quotes returned due to extractor problem.

    Thank you for your assistance.

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    Hi,

    Basically a method of doing away with rod or cable control linkages.

    Typically linking actuator and control by hydraulic means.

    Developed in mid 1930s and came from a number of suppliers eg Helishaw and most commonly used in propeller pitch control gear.

    Regards
    Ross
    The Intellectual Property contained in this message has been assigned specifically to this web site.
    Copyright Ross McNeill 2015/2018 - All rights reserved.

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    Ross.

    Many thanks the name bore little hint as to the function upon the aircraft. Thanks again. Colin.

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    Default Exactor Control

    Quote Originally Posted by colinpateman View Post
    Ross.

    Many thanks the name bore little hint as to the function upon the aircraft. Thanks again. Colin.
    I hope I might help here.

    The hydraulic control was called an exactor, and they were made by the Exactor Control Co. and by other companies under licence. Basically a sealed oil-filled hydraulic control that allowed fine control of systems. In the Whitley the airscrew pitch was controlled by exactors. A detailed description of the item is given in a post on another forum:
    http://worldwar2warbirds88121.yuku.com/topic/367#.TyEAwa44XEU

    In a few operational reports I have read that the aircraft returned with exactor trouble. If the airscrews could not be placed into coarse pitch after takeoff and climb the aircraft's range was severely reduced and therefore could not continue the operation. In extreme cold these oil-filled controls could even freeze up.

    Deadrock

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    Hello Deadrock,

    The Exactor control was fitted on Short Stirling Is, and from I've read on the subject (for example about No. 7 Squadron in 1940-41), the system was not really working properly at the time.

    Joss

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    Murray Peden DFC, RCAF, author of "A Thousand shall Fall" encountered his first Stirling at HCU Stradishall.

    “The throttle, mixture, and pitch controls were “Exactor” hydraulic controls, a type completely foreign to me. Up to this point in my career-and I was not alone in this-I had never encountered anything but straight mechanical linkage.

    The Exactors, we found, required careful and frequent priming, otherwise startling problems arose. We heard stories of pilots on takeoff opening the throttle levers, from idle to full bore, without drawing any change in engine response whatsoever. Conversely, we learned that you could cut your throttles on landing and have the engines-or any combination of them-continue to roar at full power. This phenomenon was guaranteed either to kill you or to come very close to doing so. We became very Exactor-priming conscious.”

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    Glad the Extractor/Exactor problem has been sorted out! In British aircraft these hydraulic controls were extensively used for manipulating the engine/propeller controls on such types as the Short Empire boats, Sunderland, Stirling (early models), Westland Whirlwind twin-engined figher, AW Ensign, obviously also on Whitleys, and I think on the DH Flamingo. This type of control was originally trumpeted as THE answer to manipulating various controls on larger aircraft, particularly those with multiple engines, as the controls required merely a single small diameter steel hydraulic line to operate the control, and all those pulleys and cables (including return cables in most cases) could be dispensed with - and no continuous running adjustments! However the shortcoming already aired on this thread soon became apparent, but as several large and important aircraft types were already being delivered in large numbers by this time, the well-known constant "priming" had to be learned by all operators, although I believe the later Stirlings were delivered with conventional controls. The Exactor control system was also built in the USA by Sperry under license (but manufactured using castings rather than welded sheet construction), and one application I know of was on the Grumman TBF (Avenger) to manipulate the ASB yagi anennae under the wings, also presume ditto for SBD (Dauntless) and SB2C (Helldiver) so-equipped.
    Interestingly, despite its well-known short-comings, I believe the original Exactor company is still in business, and still marketing these controls for numerous applications - check on Google! I presume that the original shortcomings have been reduced or cured over time, although I have always suspected that the constant vibration these devices fitted in aircraft were subjected to may have contributed to the problem. Anybody have any knowledge of this?
    David D

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    Default Whitley Exactor problems

    I have come across 'Exactors' (Exactor being Company / Trade name), being mentioned in Bomber Command records at TNA.

    Basically the Whitley had problems with leaking fluid from the pipework and the control of the blade pitch would be lost.

    I suspect that aircraft vibration caused any compression type joints / unions to leak.

    Vibration of the fuel joints / unions on the Halifax aircraft caused the fuel lines to leak and I suspect that the Exactor hydraulic control pipe joints / unions leaked due to airframe vibration as well.

    Mark
    Last edited by Mark Hood; 27th January 2012 at 22:43.

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    Default Whitley V, Exactor Problems

    A bit more to my last post.

    Bomber Command at Southdown reports on the 15.8.1940 that the Chief Technical Officer is going very thoroughly into the whole question of exactor control troubles in No.4 Group.

    The Control levers for the Airscrew Control were in the cockpit, to give fully fine pitch to positive coarse pitch of the airscrew.

    There were some modifications in Whitley V Leaflet Nos:-
    P.6 Airscrew exactor control (Modification cancelled by Leaflet P.13)
    P.13 Airscrew exactor control

    P.17 Whitley V - Airscrew Exactor Control Steel Nipples-Introduction-
    Replacement of nipples in the pipe joints of the airscrew exactor control by steel nipples as an interim measure-
    Whitley V, Modification No. 330, Class 2, Interim Measure - Dated 10.8.1941, per RDA Defects Signal 10/12/1940-
    This cancels Whitley/221 and Whitley/257 Modifications [likely Leaflets P.6 & P.13 above] and is superseded in turn by Whitley/356 Modification [Leaflet P.18 below].

    P.18 Whitley V - Airscrew Control Exactor Unit - Flexible Pipe at Receiver End-Introduction-
    Whitley V, Modification No. 356, Class 2.

    The fitting of a flexible pipe at the receiver end (and early Mods to the joints), likely suggests that vibration movement was causing the control pipework to leak at the pipe joints and at the Exactor Unit joint.

    Mark
    Last edited by Mark Hood; 28th January 2012 at 17:42. Reason: alter layout "Exactor Unit joint"

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