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Thread: Variable incidence tailpane on Canberra

  1. #1
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    Variable incidence tailpane on Canberra

    Hello all,

    can anyone give me some info on how this worked, i.e. when the angle of incidence was changed, and if this was controlled in a trim-tab manner or just part of the normal elevator surface controls via the yoke?

    Thanks,

    Steve

  2. #2
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    Yes. Very simple and effective use of an electric actuator to drive the tailplane incidence up and down.

    The Canberra was a really delightful aircraft to look at, work on and fly in. Of all the aircraft that I have been associated, got to be one of the best.
    Safety first. Always.

  3. #3
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    Thanks Fieldhawk. So the normal motion of the yoke on the elevators controlled the electric actuator then? Was this a pretty advanced feature for a 1940s era design?

    I am a dedicated Canberra nut so you've no trouble convincing me she's a beaut to look at!

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    Quote Originally Posted by nazca_steve View Post
    Thanks Fieldhawk. So the normal motion of the yoke on the elevators controlled the electric actuator then? Was this a pretty advanced feature for a 1940s era design?

    I am a dedicated Canberra nut so you've no trouble convincing me she's a beaut to look at!
    Steve
    The yoke controlled the elevators in the normal way,there was a switch on top of the yoke (been a loong time but i am pretty sure it was on top of the yoke,scorpion 63 will be able to tell you for sure),which moved the tailplane actuator ...hence tailplane incidence for trimming the a/c in pitch.

    regards baz

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    Steve
    Just checked a photo of a canberra cockpit...the tailplane trim switch is on the top of the control column,it is a 'twin pole' type not on the control 'horns' or 'yoke' but on top of the vertical column or 'stick'

    cheers baz

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    The double pole switch is the air brakes selector. The tail trim is a push switch and biased rocker switch, mounted on the right hand horn of the control stick, which both have to be selected together, this replaced the single switch which could fail and caused several fatal losses on early Canberra's where tail trim could motor fully up or down and stay in that position.
    Last edited by scorpion63; 20th June 2009 at 19:19.

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    Quote Originally Posted by scorpion63 View Post
    The double pole switch is the air brakes selector. The tail trim is a push switch and biased rocker switch, mounted on the right hand horn of the control stick, which both have to be selected together, this replaced the single switch which could fail and caused several fatal losses on early Canberra's where tail trim could motor fully up or down and stay in that position.
    Thanks S63...It has been a long time,I had worked out the switches but too late by the time I got back here !!!!


    cheers baz

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    Many thanks for all the info chaps, very helpful.

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    Yes we have got there. Two pole rocker switch for tailplane trimming so that the early runaways would not be repeated. The elevator is linked to the stick by a rod for the entire length of the aircraft. As far as I can remember trim actuator moves the rear (spar) of the taiplane. Am I right?
    As an electrician (sorry, we all have a cross to bear) I found the Canberra one of the best aircraft to work on. Everything had been thouugh out carefully and not just crammed in corners like so many other types. No wonder it is still flying.
    Safety first. Always.

  10. #10
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    We can thank Teddy Petter and the other genius team members at EE for that, Fieldhawk. Funny you should mention it being thought out and not crammed in - whenever I see the interior of a Canberra it looks very crammed-in to me (being a civvie outsider that is). Of course, I am sure it was considered adequate enough in its original design for a radar-guided bomber, but getting down into that nose crawlspace in full flight gear for visual bomb-aiming must have been a tad tricky at times!!

    Don't get me wrong though, I love the old girl. I think she is now out of service with all nations though (barring any NASA WB-57s), but some 50+ years in the RAF is impressive.

  11. #11
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    Quote Originally Posted by nazca_steve View Post
    Thanks Fieldhawk. So the normal motion of the yoke on the elevators controlled the electric actuator then? Was this a pretty advanced feature for a 1940s era design?
    Certainly Hawker and Fairey designs of the 20s and 30s had variable incidence tailplanes for trim, adjusted by screw-jack on one spar, controlled from the cockpit in flight - manual power, I presume. Fairy had 'variable camber wings', on their biplanes too.

    The Westland Lysander tailplane went through various design iterations - the final version had a variable incidence tailplane, required to be at different angles for take off and landing, and potentially fatal in a go-round the elevator control not having enough authority to overcome the trim angle. Harald Penrose was not happy to sign the design off, but with the war coming, it was. (How much the of Lysander's design was Petter's is disputable.)

    HTH
    James K

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    Very, very interesting - show how little I know about design history. I should imagine that shortcoming on the Lizzie was rather worrisome for crews - I suppose it made pretty sure you got the landing right on the first go-round, eh?

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    Quote Originally Posted by nazca_steve View Post
    Very, very interesting - show how little I know about design history. I should imagine that shortcoming on the Lizzie was rather worrisome for crews - I suppose it made pretty sure you got the landing right on the first go-round, eh?
    Yes if they had to do an overshoot(go around) they had to gradually open up and retrim in stages to retain control.

    cheers baz

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    I very recently just repaired a snag on WT333's tail incidence actuator. It's a beast of thing, with a high and low gear motor (though only one motor was actually ever used). When you see a Canberra tail and elevator assembly removed from the aircraft, you can see why such a big actuator was required - its is a single piece affair with a weighty spar forming a flat web running through the middle which occupies the famous "see through" portion of the tail cone..real engineering!

    Our fault was just a crusty connection..the tail was stuck in the dangerous fully up trimmed position..a real issue even for us fast taxy types as it tries to lift the nose off the ground at the very earliest opportunity. Rectified by a quixk disconnect and blast with some moisture dispersant, trimmed back to neutral then associated fuse duly removed to prevent the same thing happening again!

    And to think I was born a rigger...don't tell my Airframes TM I've been flirting with wiggly amps for goodness sake!

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    Tim, very, very interesting story there, good to know and help my overall understanding of the thing. Any chance you could take some snaps in that region or better yet, next time (if there is one) you are doing some maintenance on her? Ideally I'd like to see how much 'see through' there is when trimmed fully up and down. Also, is the actuator visible in this area, or buried further out of sight? 'scuse the ignorance here, I'm working with small cutaway drawings and trying to build her for FS2004.

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    Does anybody know the degree of trim offered the variable incidence tailplane? In all the pics I have show what appears to be very little angle, this striking me as the 'neutral' position as parked after landing.

    Cheers,

    Steve

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    Quote Originally Posted by JDK View Post
    Certainly Hawker and Fairey designs of the 20s and 30s had variable incidence tailplanes for trim, adjusted by screw-jack on one spar, controlled from the cockpit in flight - manual power, I presume. Fairy had 'variable camber wings', on their biplanes too.

    The Westland Lysander tailplane went through various design iterations - the final version had a variable incidence tailplane, required to be at different angles for take off and landing, and potentially fatal in a go-round the elevator control not having enough authority to overcome the trim angle. Harald Penrose was not happy to sign the design off, but with the war coming, it was. (How much the of Lysander's design was Petter's is disputable.)

    HTH
    The DH89 Rapide also had a variable incidence tailplane for trim... and Miles aircraft were playing around with an all-flying tailplane way before the Merry Cans claimed it as 'theirs' with the Bell X-1
    Interested in what I'm doing? Please visit http://gmsenterprises.blogspot.com/

  18. #18
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    [QUOTE=nazca_steve;1437632]Does anybody know the degree of trim offered the variable incidence tailplane? In all the pics I have show what appears to be very little angle, this striking me as the 'neutral' position as parked after landing.

    Cheers,

    Incidence measured from starboard inboard rigging gauge position
    Range between electrical stops;
    2 deg12min +/- 5.4min to 3deg 59min +/- 4.5min

    Take off position 3deg 15min +/- 2min
    On shut down trim is set "fully nose down and one blip up"
    Hope that helps

  19. #19
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    Thanks Scorpion, it should be enough to get what I need done. What do the 'min' denote by the way? Not being that technically minded it went over my head.

  20. #20
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    A friend of my father was flying a Canberra in 1954 or 55 at the Biggin Hill airshow (I believe) when he suffered a tailplane actuator fault.
    Apparently, during a flypast, the aircraft climbed and disappeared from view...shortening his routine somewhat.
    He did manage to land the aircraft, with great difficulty. I believe, as a result, Canberras were grounded whilst the fault was investigated.

    I would greatly appreciate if anyone have any information on this incident?
    (The pilot was T.Murphy and aircraft was probably from 231 OCU Bassingbourn or possibly 101 Squadron Binbrook)

    Many thanks
    Richard

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    Thing that I remember about the Canberra is that crews returning from Luqua were rumoured (it could not possible be true, now could it?) to stow duty free fags in the tailplane actuator space and the customs officers couldn't check the area as 'on the secret list'.
    Mike (RAF Marham 1956-8)

  22. #22
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    One pilot if I remember correctly came back from Hong Kong and reported that he had handling problems and noticed the Nav getting the groundcrew to unpanel the back end, there he discovered a new washing machine tied off to the cables. He had spent the whole trip humping a washing machine back and forth.

    As for moving tail planes check out the Mooney's, the whole backend pivots just fwd of the fin.

  23. #23
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    getting the groundcrew to unpanel the back end
    Unlikely, access to the rear fuselage is via a panel on the underside and ust big enough for one person to enter.

    As for the tailplane actuator space ... I don’t think so.

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    Quote Originally Posted by TonyT
    As for moving tail planes check out the Mooney's, the whole backend pivots just fwd of the fin.
    Or PA22 Piper Colt or Piper Tripacer

    Moggy
    "What you must remember" Flip said "is that nine-tenths of Cattermole's charm lies beneath the surface." Many agreed.

  25. #25
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    Originally posted by TonyT
    One pilot if I remember correctly came back from Hong Kong and reported that he had handling problems and noticed the Nav getting the groundcrew to unpanel the back end, there he discovered a new washing machine tied off to the cables. He had spent the whole trip humping a washing machine back and forth.
    I agree with Exbrat on this one Tony - I think it is unlikely that anybody could smuggle a whole washing machine into blighty via a Canberra,I doubt you could even fit a small one such as a Hoover Washdog (twin tub) up through the back hatch of a Canberra - as Exbrat posted - the back hatch panel was just big enough to mount your (3 ?) spare starter cartridges on and just big enough to get the rear (flexible) fuel tank in and out of.I did see a PR7 in from Malta one day in the early 70's and the pilot proceeded to untie his bicycle from inside the fuselage (camera bay ? ) - he had been posted back to blighty.

    rgds baz

  26. #26
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    Originally posted by nazca_steve

    What do the 'min' denote by the way? Not being that technically minded it went over my head.
    'min' = minutes

    60 minutes in one degree.In aviation terms it is the usual calibration unit used for Rigging on flying controls using (say) a Watts Clinometer to accurately measure flying control range of movement or for checking angles of incidence etc.
    Sorry about late reply LOL

    rgds baz

  27. #27
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    A friend of my father was flying a Canberra in 1954 or 55 at the Biggin Hill airshow (I believe) when he suffered a tailplane actuator fault.
    Apparently, during a flypast, the aircraft climbed and disappeared from view...shortening his routine somewhat.
    He did manage to land the aircraft, with great difficulty. I believe, as a result, Canberras were grounded whilst the fault was investigated.
    Richard,

    there were a number of Canberra tailplane incidents and accidents going back a number of years. Unfortunately there was little hard evidence as to the cause(s), and a bit of "burying head in sand" by the authorities. Finally came to a head in March 1956, by which time the the growing number of reported malfunctions (and fatal crashes in which tailplane was implicated) could not be ignored. So the incident you mention was really just one several. Several fixes were proposed (since the root cause was not 100% understood) before a series of modifications were developed and applied.

  28. #28
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    Hi Abadonna,
    Thank you for your reply, I thought it was a bit of a long shot...but worth asking.

    The same pilot was involved in an incident at RAF Bassingbourn or Binbrook in 1953/54 where he had a brake failure on landing.
    The Canberra came off the end of the runway but thankfully the crew were unharmed...
    However, when the fire engine reached them it couldn't stop and it ran down a slope and into the tailplane, this caused the pilot some head injuries as he was just climbing out of the aircraft.
    I'm guessing there conversation that followed couldn't be written on this forum!

    Anyway, thanks again
    Richard

  29. #29
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    Richard,

    the overrun accident could have been WD998 (9 Sqn) on 10 August 1953. Landed at high speed, no flap and high weight. Despite heavy braking ran off end off end of runway, across overshoot and beetfield and came to rest on bank. Pilot Officer T G Murphy. Cat 3R. Pilot error.

    Just found the other incident. WD946. 9 Sqn. 20 September 1954. Battle of Britain display. "At Church Fenton, Flg Off T G Murphy was unable to do a high-speed run due to his tail trimmer sticking in the nose down position". No fault found in subsequent examination of aircraft.
    Last edited by abadonna; 12th January 2018 at 18:03. Reason: additional information

  30. #30
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    Hi abadonna,
    That is brilliant stuff, thank you. Your searching through the records is very much appreciated.
    (I'm very impressive after I gave details of the wrong squadron and airshow!)
    I'll pass the information onto my dad, he will be very pleased to hear about it.
    Pilot Officer T G Murphy was a childhood friend of my father and was best man at my parent's wedding.
    Unfortunately, my dad lost touch with him when he transferred to a Vulcan squadron during the height of the Cold War.
    I have made various attempts to find out how his career progressed without success.

    Thanks again
    Richard

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