‘Evening all.
I need the help of the Chipmunk specialists.
The picture of the Irish Chipmunk 168 in which the rudder appears to be of a different size to the ex RAF Chipmunk restored and painted as 169.
Was the rudder modified when strakes were introduced or what is the history of the difference? Many thanks for any help.
Tony K
By: Tony Kearns - 16th November 2015 at 20:43
Many thanks Mark, yes I do recall having a conversation with you at the lecture in Dublin.
It is great to get this clarified and had wondered why the Air Corps did not implement that Mod. Another problem solved!
Best wishes,
Tony K
By: Arabella-Cox - 16th November 2015 at 00:42
Hello Tony… we met, I think, at 2012’s Air Corps Chipmunk lectures in Dublin.
I agree with DB. Irish Chipmunks 164 and 168 (at least) made it into retirement still with the original design of rudder. Most of the PPRuNe link is also correct.
Accuracy on this topic is refreshing as the reasoning behind the post-Mod H.104 Extended Chord Rudder is so often misrepresented. This has become more or less the ‘standard’ Chipmunk rudder, readily identifiable by the angled ‘bite’ where the trailing edge joins the bottom rib. From primary DH sources it was NOT introduced to improve spin recovery and was proven by extensive tests to have not the slightest effect on recovery from a spin.
What the larger rudder and hence increased rudder power DID achieve was:
1. Easier spin entry, because greater yaw can be induced.
2. Better directional control during crosswind takeoffs and landings.
3. Less rudder displacement to maintain directional trim in the climb.
4. Improved sideslipping capability, useful in the forced landing case.
5. More chance of keeping the nose up during the last quarter of a slow roll.
Indeed, John Derry authored a glowing report in 1950 in which he attributed a “vast improvement” in rolling manoeuvres to the long chord rudder.
Mod H.104 introducing the larger rudder was dated January 1951. The anti-spin strakes are a separate subject and came along much later – Mod H.231, August 1958, refers.
Mark Miller
de Havilland Support Ltd
By: Tony Kearns - 15th November 2015 at 23:28
Many thanks David, it probably explains the fact that at a recent Air Corps dinner I asked this question of a number of former Chipmunk pilots ….all expressed surprise and were not aware of it. They were aware of the strakes.
Thanks again for clearing that up for me, I was starting to lose sleep over this!
Regards
Tony K
By: David Burke - 15th November 2015 at 23:00
Looking at various pictures it appears that the Irish Air Corps didn’t adopt the broad chord rudder which you see fitted to the example pretending to be ‘169’
This is useful :http://www.pprune.org/aviation-history-nostalgia/479784-raf-dh-chipmunk-smaller-rudder-fitted.html
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November 15, 2015 at 9:47 pm