Spitfire XIV with Contra-props

Discussion in 'Aviation' started by wuzak, May 21, 2014.

  1. wuzak

    wuzak Well-Known Member

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    The Spitfire XIV experienced some difficulties with directional stability, requiring larger rudders to compensate. Even then, the trim of the aircraft needed constant correction.

    In The Spitfire Story, Alfred Price mentions that the 6th Mk VIII, JF321, to be converted to serve as a Mk XIV prototype was fitted with the Griffon 85 and contra-rotating propellors. Later JF317 was also converted to run the 85.

    Does anybody know how these compared to the standard XIV, and whether stability was affected, either positively or negatively?

    Tony Buttler, British Experimental Combat Aircraft of World War II, describes the conversion of one of the Tornado prototypes to trial contra-rotating de Havilland propellers and that the result was worsened stability.

    Was the Griffon 85 ever a viable optoion to be installed into Spitfire XIV and XVIII production aircraft?
     
  2. Clayton Magnet

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    The Planes of Fame museum mated a Shackleton counter rotating prop to a Spitfire PR.XIX , with impressive results, although I dont know any details beyond that. Im sure GregP can fill in the blanks for us.
    It was a real beauty though, the extra monkey motion up front detracted nothing from the profile.
    Spitfire_PR_XIX_PS890.jpg
     
  3. davebender

    davebender Well-Known Member

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    That depends on your objective. You could turn a state of the art lightweight fighter aircraft into a flying brick like USA did with the P-43 to P-47 evolution.

    P-43A. R1830 engine. Empty weight = 5,982 lbs.
    P-47D. R2800 engine. Empty weight = 10,000 lbs.
     
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  4. vikingBerserker

    vikingBerserker Well-Known Member

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    I have to agree, it's still a beautiful plane.

    +10 points for the "extra monkey motion up front" comment. :lol:
     
  5. wuzak

    wuzak Well-Known Member

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    How much extra did the engine and contra-prop weigh?
     
  6. Jabberwocky

    Jabberwocky Active Member

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    Peter Caygill has some information on the Mk XIV with contra-props in 'Ultimate Spitfire'. If it hasn't been packed away (moving day tomorrow), I'll see what I can find.
     
  7. wuzak

    wuzak Well-Known Member

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    Thanks mate.
     
  8. Aozora

    Aozora Well-Known Member

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    Not enough to turn the Spitfire into a P-47...

    According to Morgan and Shacklady there were two Mk XIVs fitted with contra-props:

    JF321 NH657: Fitted with de H prop, considered to be the best (propeller?) hitherto flown.
     
  9. nuuumannn

    nuuumannn Well-Known Member

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  10. wuzak

    wuzak Well-Known Member

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    I have recently purchased Morgan and Shacklady, but haven't got too far into it as yet. Was just reading about the XIV in Price's book when I saw the use of contra-props on one or two of the VIIIGs and wondered how it would affect handling.
     
  11. wuzak

    wuzak Well-Known Member

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    #11 wuzak, May 22, 2014
    Last edited: May 22, 2014
    A quick scan of Morgan and Shacklady gives the weight of JF321 with Griffon 65 and Rotol 6 blade contra-prop as 6,645lb tare and an auw of 8,614lb. The first production XIV had a tare weight of 6,580lb and an uw of 8,489.

    So, the engine intsallation made a difference of less than 100lb.

    Edit: I notice that the text says JF321 was fitted with a Roto contra-prop, but the caption of teh picture of JF321 says it was de Havilland prop.
     
  12. wuzak

    wuzak Well-Known Member

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  13. Shortround6

    Shortround6 Well-Known Member

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    More hatred of the P-47 with little or nothing to back it up?

    and very, very little to do with this thread.
     
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  14. wuzak

    wuzak Well-Known Member

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    #14 wuzak, May 22, 2014
    Last edited: May 22, 2014
    Yes, quite off topic.

    The statement makes an assumption that the P-43 was a) lightweight and b) manoeuvrable. The P-43 may apear light, but it did without armour and self sealing fuel tanks:

    From Joe Baugher:
    Sounds like the P-43 was already a "brick".
     
  15. Shortround6

    Shortround6 Well-Known Member

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    Opened a new thread on the P-43.
     
  16. nuuumannn

    nuuumannn Well-Known Member

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    Not much on handling, although Like I stated, in the section on the Mk.VIII is the quote by Shea-Somminds on the graunching noise. Use of Griffon 85 question you asked about in the Spit 21 and 22 sections.

    I found a quote by Quill in Spitfire a test pilot's story that might be useful.

    "Meanwhile intensive flying went on with the Griffon 61 engine, both at the firm and at Boscombe Down and one of the Mk.VIIIGs, JF321 was fitted with a rotol six blade contra rotating propeller. This consisted of two three bladed propellers on concentric shafts rotating in opposite directions but controlled by a single constant speed unit. It was a most remarkable device, rather complicated mechanically, but it completely eliminated proeller torque, both at take-off and during manoeuvres in the air. It also provided a much needed increase in blade area within a given diameter which in itself tended to solve a fundamental problem for the Spitfire."

    This gives something of an indication of handling, but not much. Quill doesn't say anything else about handling, although he talks about failures of translational bearings and the graunching noises.
     
  17. Aozora

    Aozora Well-Known Member

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  18. wuzak

    wuzak Well-Known Member

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    Thanks Nuumann and Aozora.

    Just found a report on the 21 with contra-rotating props in Price's book.

    Trial of Spitfire F.21 LA218 With Contra-Rotating Propellor.


    Introduction
    Spitfire F.21 No. LA218 was delivered from Messrs Vickers Supermarine at High Post on 23 May 1945 for brief handling trials and was flown by nine experienced pilots from this Establishment.
    This aircraft was fitted with a Rotol contra-rotating propeller and had a slight modification to the rudder. Otherwise it was representative of the production model.
    As the aircraft was available for only one afternoon it was not possible to carry oout a full and comprehesnive trial, and it must be borne in mind that the opinions expressed are based on one flight only by each pilot. However, it was felt that the opinions were so unanimous that it was worthwhile putting them on paper to make them available for wider distribution.

    Handling on the Ground
    Taxying is quite straight forward and exactly similar to the normal Spitfire.

    Handling in the Air

    Take-Off
    Although the Take-off run appears to be longer than on the normal Spitfire 21, the actual handling is much improved. Provided the rudder has been trimmed there is no tendancy to swing whatever and it is possible to climb the aircraft immediately, with hands and feet free from teh controls and without skid or slip. If correct trim has not been applied there is a decided swing once the aircraft becomes airborne.

    Flight
    Handling in teh air is remarkably pleasant and all manoeuvres, including aerobatics, can be carried out without attention to rudder trim and irrespective of throttle setting and/or the speed. It is possible to loop and slow roll with feet free from the rudder.

    Throttle Response
    Violent opening of the throttle produced surging, but there is no indication of this when the throttle is opened smoothly. The engine of this aircraft tested appeared to run excessively rough at most throttle settings and at high rpm there appeared to be a phase of vibration which could not be attributed to the engine rough running.

    Ground Attack
    In dives up to 60 degrees and at all speeds and throttle settings the sight can be held on the ground target without the slightest tendancy to skid or slip. Teh aircraft becomes tail heavy at about 280mph and a large forward trimming movement is necessary in order to fly 'hands off', especially above 400mph Indicated, but once trimmed the dive is absolutely straight. With hands and feet off the controls, recovery from the dive was carried out by means of tail trimming and teh ensuing climb was found to be without tendancy to turn, skid or slip. Moreover, the light aileron control and excellent manoeuvrability of this aircraft at high speed make it emminantly suitable for strafing where a quick turn on the target and violent evasive action are frequently required.

    Combat
    The throttle can be opened and closed without any noticeable change of aim in azimuth but the absence of need for rudder trimming emphasises the improtance of correct elevator trim, which previously might have gone unnoticed. The aircraft handles pleasantly in steep turns and shows no tendancy to tighten up.

    Landing
    Landing is straightforward with a very marked braking effect with the propeller in the fully fine position. There is no tendancy to swing but the landing run appeared to be considerably longer on teh aircraft tested than on other marks of Spitfire. This may have been due to the fact that the engine was idling too fast as throttling back on teh engine in question was liable to cause a complete cut-out. When the throttle is opened at near stalling speed, for example to correct a bad landing, the lack or torque greatly improves the stability of the aircraft and reduces the risk of accident.

    Conclusions
    The Spitfire 21 with contra-rotating propeller shows a remarkable improvement in handling over the normal aircraft, and allows all manoeuvres to be carried out without attention to rudder trim.
    The elimination for the need for rudder trim during ground attack reduces the possibility of a skid at the moment of firing. This factor has always been one of the major sources of aiming error in the past. The fitting of a contra-rotating airscrew has now turned the aircraft into a very reasonable gun platform and without any apparent loss in performance.
    Air-to-air combat is similarly enhanced and it was found that no change of trim was necessary with change of throttle setting. A considerable improvement in sighting accuracy may be expected.

    Recommendations
    From the limited amount of flying carried out by the Central Fighter Establishment on the Spitfire F.21 fitted with the contra-rotating propeller it would appear that the skid, the major source for error in ground attack, is largely eliminated by the introduction of the contra-rotating propeller. This innovation promises such advantage for conventional airscrew fighters that it is strongly recommended that another aircraft with a contra-rotating propeller be attached to the Central Fighter Establishment as soon as possible fore xtensive and exhaustive tactical trials.
     
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  19. wuzak

    wuzak Well-Known Member

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    So, from this brief trial it would seem that the handling of the F.21 was enhanced by using the contra-prop. It would not be unreasonable to assume that the XIV would have also benefitted from the CR prop. The issue for bringing the CR into production earlier seems to be one of reliability, with failures of bearings, vibrations (possibly the vibration in the above report was also due to the prop) and oil leakage from the rear prop mechanism.

    Far from turning "a state of the art lightweight fighter aircraft into a flying brick" the contra-prop may well have elevated the XIV and XVIII higher in fighter ability.

    (And not that the Spitfire, especially in XIV form, was actually a lightweight fighter - either in terms of airframe, performance or firepower.)
     
  20. pbehn

    pbehn Well-Known Member

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    Some one recently posted that a spit (I think it was a spit) was fitted with a Shackleton contra prop but it suffered problems with limited "G" in turns.
     
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