Asymmetric Canberra

[Phortz]

Hi folks,

Back after a spot of yachting in the sunshine, good for the back don't you know!

Anyway, the point of my getting back into the P-Prune web site.

Is there anyone out there who knows if it was possible to fly a Canberra, in a non-asymmetric mode and throughout the 'normal' flight envelope range of air speeds, with a broken rudder torque tube?

The plot thickens!

Cheers aye....Phortz

PS - I believe I may have the spelling right this time, tks!

[FJJP]

Possibly, but more detail needed, eg, surface winds on t/o and landing, flight profile, etc. Why the question?... Intrigued!

[Lukeafb1]

Phortz,

This subject was discussed at length on another thread about 4 or 5 months ago. Unfortunately, I can't now remember where it was. Can anyone out there help?

[The Nr Fairy]

Luke:

Do you mean this thread (http://www.pprune.org/forums/showthread.php?s=&threadid=80069&highlight=canberra+torque) which Phortz started in February ?

[Lukeafb1]

Fairy,

Yes thanks, but Phortz started it?? I'm confused.

[Phortz]

Thanks FJJP and other for your comments.

Yup, this is a continuation of a previous thread of a few months ago.

I'm now back in the UK and a piece of the airframe has come out of the 'woodwork' which was probably not considered during the original 'Board of Enquiry' and hence the Board findings!

My question is as follows, assuming a normal flight envelope with matched RPM, no UP's and no significant cross winds during T/O and landing, is there a Canberra pilot out there who has experienced flying a Canberra with a broken rudder torque tube.

Information which I already have to hand, from a VG source has stated that it is possible provided nothing untoward happens which requires a large rudder input to keep the aircraft S/L or in a balanced turn.

This now also begs the question, has anybody found a broken torque tube during a post/pre-flight inspection or during a minor/major servicing cycle?

Cheers aye.....Phortz

[FJJP]

I've no experience of a broken torque tube, but several times I have had a torque tube frozen after a prolonged high level flight. Symptoms were rudder refused to move! After a time below the zero degree isotherm, the ice melts and the rudder becomes effective again. Only once did I have to land with the rudder frozen (short of fuel - couldn't fly around below the zero degree long enough for the ice to melt). No problem with the landing, though, since surface wind virtually zero.

Chap at St Mawgan once landed with full rudder on and stuck after and air test malfunction - got the AFC for his troubles.

[Reichman]

If the torque tube breaks, the results will be an increased load on the rudder pedal in order to move the rudder as the anti balance tab wouldn't move. If this happened just after take-off there would be a lot of grunting from the pilot and a severe case of "Disco Leg" afterwards. At any other stage of flight I doubt if there would be much difference.

Never heard of a torque tube breaking but I will look into it.

[Titan Locked]

Slightly off thread but as I understand it one of the actions following pulling the yellow and black handle in the Canberra is the yoke is automatically pulled forward (ie away from the seat) to clear the way for the seat to go upwards wihtout taking the pilots knees with it. Understand this happened to a sqn JP (a plt off - shows how long ago it must have been) whilst flying down in Aus. Managed to still land the thing and I believe also got an AFC. Would be interested to hear as to the validity of this story ...

Almost 60 years old and still going strong (and thats just the aircrew!!)

TL

[Lukeafb1]

I serviced many marks of Canberra over a period of nearly 12 years, both 1st line and majors. I never experienced or heard rumours of broken torque tubes. Can't think inthe normal course of events, how one could snap. They were pretty strong!

I've also heard the story of the pilot who landed successfully after the explosive collar on the elevator tube fired and severed the elevator controls. The column would have smashed most of the console in front of the column as it was sprung forward. Actually, I believe that a successful landing has been done with the same problem twice.

[Albert on Tour]

I had six years as a rigger on Canberras (13 Sqn, 100 Sqn & Canberra Servicing Flight - all at Wyton) in the 1980's

In CSF we did Primary Star, Minor and Minor Star servicings. On the Minor Star's we would replace all the torque tubes.

A couple of (pedantic) points

Reichman

If the torque tube sheared you would lose control of the rudder alltogether.


Lukeafb1

If the Elevator control tube explosive collar went, then it would just shear the tube. It takes gas from the ejection to force the control column forward via the snatch unit.


I cannot imagine a torque tube shearing, but imagine that the weak point would be connecting point of the inner and outer sections. (The fact that they were replaced every Minor Star servicing suggests that they were a lifed item, due to the stress they were put under and possibly due to previous failures)


Phortz

I am assuming that (as a Nav) you know the difference between a control tube and a torque tube. If you have the rudder, then the torque tube is inside it still?

[Beeayeate]

AoT wrote :
If the Elevator control tube explosive collar went, then it would just shear the torque tube.
In pedant mode . . . The det collar severs the elevator control rod which runs under the floor of the port side cockpit throttle console, not the torque tube. :ok:
Also . . .
It takes gas from the ejection to force the control column forward via the snatch unit.
Don't remember this. :confused: I seem to recall a couple of wicked springs at foot of control column under the floor and anchored just about under the bang seat. Hazy memory here, it was 30 yrs back when I last did this sort of riggering stuff on Canberras - 3Sqn, 51Sqn, 39Sqn, TVASFlt, Wyton.

Further Luke, when the control column is "snatched" there's only relatively light damage to the bottom of the instrument panel - except in a B(I)8.

Ref the topic though, I for one would be interested to hear a tad more detail from Phortz. If, as he says, there's no axe to grind, there would seem to be no problem in setting out more gen - maybe even a pic of the "bit" he now has. :rolleyes:

[Lukeafb1]

Albert,

Sorry, you're most definitely wrong about gas being the means which forced the control column forward (at least on B6, B15, B16 and T4 mks - I can't speak for other marks). I'm also talking here of the nineteen sixties and early seventies. The time, during which the two airborne emergencies which Titan and I mentioned, occurred.

A pre-set spring which surrounded the elevator control tube down at the pilot's left side, was the mechanism which drove the control column forward after the tube was severed. The column could be pulled back after the explosive had fired, but with extreme difficulty. On the above marks, the bang seat was totally independent of the control severing mechanism. As proof, how would a pilot manage to fly and land a Canberra with a severed elevator control, if the column was sprung forward only as a result of the pilot ejecting??

Indeed, I vividly remember a groundcrew member activating the device whilst the aircraft was in the hangar for servicing (at Watton, or possibly Wyton). It caused considerable damage to the console, but the seat and the man remained in the aircraft. One of them, however, suffering from acute bowel instability!!

I'm sure there must be some Pprune Canberra armourers out there who would confirm this.

Beeayeate, do I know you from 51??

[Beeayeate]

Luke

Thought AoT had it wrong. The seat had no part in the action as the plumbers were only involved just in re-fitting the det in the det collar, otherwise it was a rigger and leccy job.

And I too recall a story (but only one) about a pilot getting a Cranberry back after inadvertant det collar action - can't find the detail in my crash list of Canberras though, maybe too technical for the brief info I have for each crash.

Ref the ground crew and collar activation. Seem to recall this was an instrument mech at Bruggen<?> in late 60s.

Also, on reflection, I now recall that the inst panel damage, when the column was snatched forward, WAS a serious thing. :\

As for 51 Sqn, well, matey, I was on that lot from 65 - 67. You? :ok:

[Albert on Tour]

Oh dear I wish I hadn't joined in

Thanks Beeayeate, I'll edit that, sorry if it makes nonsense of your post.


I ain't wrong. (or maybe the design changed?) The snatch unit has got a big spring but was tested on the ground using a nitrogen rig, simulating gas pressure tapped from the ejection seat as it started up the rails. Explosive collar removed for test but presumably fired by snatch unit as part of the operation.

I was on B2, T4, PR7, E15, T17, & TT18 in the 80's

[FJJP]

The Canberra (B2 varients) had an electric trim for the elevator - it actually moved the whole tail wing [I believe the first variable incident tailplane in the world?]. It was therefore possible to manoeuvre the aircraft in pitch using the trim alone, thus enabling the pilot to land with the elevator control rod severed.

[Pindi]

Not sure how the original thread got round to the snatch unit but I'm with Lukeafb here. I'm sure the seat gun gases had no input to the operation of the explosive collar bolts and the snatch unit.
After all, it was years before the Model T was fitted with magic seats in the front and the Nav didn't have a black and yellow handle in the back to activate the device. I once had the snatch unit self-activate in the air, fortunately without the explosive collar
operating. The effect was benign and apart from a sudden nose down pitch, which was easily controllable, it was contained within the trim range and presented no landing problems. Nobody offered me an AFC though !!

[Lukeafb1]

Albert,

I suspect from your reply (re: replacing torque tubes during servicing), that the practice of replacing torque tubes as a norm during Minor Star servicing, came in after I left the R.A.F. It certainly wasn’t normal practice in the 60s and early 70s – I left in 1973.

Beeayeate,

(tongue in cheek) Doubt that you would find the details of the incident you refer to in your crash list. Cos’ he didn’t!

I was on 51 from 63 to 64 and again from 68 to 72, so our paths obviously didn’t cross.

FJJP

I think I’m right in saying that almost all Canberras (don’t know about the PR9, though) had all moving tailplane trim.

All,

Saw a photo once (in the 60s) of the results of the column impacting the console after the explosive collar fired (during servicing) and if my recollection is accurate, the panel where Battery Master Switch and Master Start switches were situated and up to about 10 inches above, looked like a sledge hammer had been taken to it. Don’t know, however, if the same degree of damage was always the result.

Phortz,

Hope we're not departing too much from the main theme.;)

[Reichman]

Just to get back to the original question - and my original answer. Just checked with the engineers: If torque tube fails you still have control of the rudder. There will be no aerodynamic assistance from the spring tab. Normal symmetrical flight would be no problem. However, asymmetric would be quite difficult and require plenty of grunt. I do have the diagrams if anyone requires a more detailed explanation.

[FEBA]

Once went out with a girl called Vanessa. I checked out her torque tubes regularly via the snatch unit without double de-clutching. Ah those were the days!!! ;)
FEBA

[Phortz]

Many thanks, one and all for your valuable inputs, though I doubt if the most recent from FEBA would be any great help at a Board of Enquiry!

Reichman

Can you thank your engineers for taking time out from no doubt a busy schedule to dig out the appropriate drawings of the tailplane assembly and the confirmation of that which I (we) already suspected, the Canberra can be flown with a broken torque tube within the rudder assembly, provided no throttle embalance occurs during the flight.

May I get back to you via other means, if needed, to arrange a sight of the drawings?

I expect our field recce this month will provide the additional data needed to complete the puzzle after 32 years! How will that be for a closure, to use an awful American phrase.

Phortz

[Albert on Tour]

Good Luck Phortz

I'll crawl back into my box now, but I'd just like to re-state on record that I think you'd totally lose control of the rudder if the torque tube broke.

No need to gang up on me any more chaps, I won't get 'closure' until I have a torque tube in my hands for inspection. (As I did on numerous occasions in the early 80's)

If anybody wants to start a Canberra thread on the Nostalgia forum then I'll be happy to share memories! Hazy though they seem to be, they were the best years of my life.

Albert

[Beeayeate]

AoT

Be happy to "torque" Canberras with you, anytime, and with Luke, (who's another rigger :} ). Send me a PM.

There's a new Cranberrie thread on "Nostalgia" already.

You might enjoy browsing my Canberra Tribute (http://www.bywat.co.uk/) web site, have look through the pictures, squadrons list, survivors, etc. :ok:

[Reichman]

Phortz,

No problem at all. Just drop me a private msg if you need anything and I'll see what I can do.

Reichman