Chipmunk Mk.23
 

Hi All, I'm writing an article about flying Chipmunk Mk.23 Tango Fox/Bumblemunk and would welcome any info on it. Does anyone know why it was only in the RAF for a few years? Also, does anyone know anything about Farm Aviation? What happened to the other Mk23s? Cheers, Dave

https://cimg1.ibsrv.net/gimg/pprune....f80954efb8.jpg

Its first civil owner was the RAE (Farnborough) Aero Club, so maybe some kind of under-the-counter transaction ?

Farm Aviation of Rush Green, Hertfordshire (just South of Hitchin/West of Stevenage) was a crop-spraying outfit. Bill Bowker was the man behind it, I think, and they certainly had a Chipmunk of that reg.

https://cimg8.ibsrv.net/gimg/pprune....bdabb24dbd.jpg

Thanks Dave & Allan, all useful stuff. Interesting that it clearly still has a Gypsy engine - as a sprayer I'd assumed that part of the conversion was to fit a better, more powerful engine.

If I'm not mistaken, in the photo in post #1 it has a Lycoming O-360, whereas in the earlier B&W photo it still has the Gipsy Major.

I like the elastic bands holding the u/c fairings on.

G-APMN C1/0128 ex WB680 w/o at Potterhanworth Fen 27/5/1958
G-APOS C1/0763 ex WP893 to N8345 8/1969, current as N40291 with Lycoming GO-480
G-ASPW C1/0602 ex WK580 (composite, with parts of C1/0193 ex WB746) w/o after hitting cables at Wheathampstead 1/7/1967
G-ATVF C1/0265 ex WD327 current, based at RAF Halton
G-AOTF C1/0015 ex WB563 current with Lycoming O-360, based at Saltby

The first two were DH conversions; the other three were converted by Farm Aviation.

That's correct Dave - I'm flying (well, between tows) in the first pic, it does have a -360. Thanks for the info on the others.

Wikipedia suggests "Chipmunk Mk 23 Five converted T.10s powered by de Havilland Gipsy Major 10 Series 2 engine and with agricultural spray equipment."
without putting a date to it. Whether the Gipsy Major 10 Series 2 or the Lycoming O-360 is the "better" engine is not for me to say, but they were 145 b.h.p. and 180 b.h.p.

The O-360 is lighter, more powerful and more reliable - and uses a LOT less oil!

... but ruins the lines of originally pretty aeroplanes.

Or try a 275 hp GO-480. :O



Interesting that the US owner has restored this Mk.23 to the original Chipmunk tandem 2-seat configuration. Shame about the rudder. :O

Nice, so now he's b**ggered both ends of an otherwise pretty aeroplane!!!

Hmmm. So the choices are that you could have an aeroplane fitted with an engine that is lighter, more powerful and more reliable, and uses a lot less oil, or alternatively you could have an aeroplane fitted with an engine that is heavier, less powerful, less reliable, and uses a lot more oil, but is prettier. Sorry, I place power and reliability above pretty.

Does your wife/girlfriend read this???

My inclination is to prefer originality when dealing with out of date machinery rather than post-period redesign - in my case it's cars, but I think/hope most owners of old aeroplanes take that view. For example, would you re-engine a Spitfire with something more powerful than and a different shape from a RR Merlin?
The de Havilland Gipsy Major engine is quite common and has a good support for overhaul, etc.

Australia has its share of Chippie mods.


https://cimg2.ibsrv.net/gimg/pprune....ddf82f4f2e.jpg
Sasin Aerostructures SA-29 Spraymaster: Photo Geoff Goodall
https://cimg3.ibsrv.net/gimg/pprune....67f034db26.jpg
SA29 Spraymaster. The original engine was swapped out for a 210 hp Continental, although a Mk 2 version was offered with a conventional 145 hp Gipsy Major 10. The aircraft above was the Sundowner (non agricultural) variant featuring a 180 hp Lycoming O-360 engine: Photo Ed Coates

With regard to a Spitfire of course not Allan, but TF works, and sometimes works hard. The O-360 is a better engine from every perspective, which is why they junked the Gypsy. I flew a Beagle Terrier last year that had had the same conversion - nicest Auster I'd ever flown!

I agree that it doesn't do much for the Chippie's lines, but with almost double the horses up front, I'd want a larger rudder and fin too!

Dave /Allan ,the Allison V1710 could be a replacement for the Merlin,in Spitfires,one in USA and one in France,both replicas,but not here,I fear..!
The picture of Farm Aviation G-APOS in the video shows it has `slats`fitted on the outboard wing section;anyone know if this was `deH mod ` ,or FmAv…?
Difficult to tell if `OTF` had them fitted as well....

The outboard slots/slats were part of the DH mod, presumably also embodied by Farm Aviation on the three aircraft they converted.

Tango Fox doesn't have slats, but I've got an idea it might've done in the past.

Regarding the rather more elegant SA29, I think the endless bickering between AeroStructures/Mike Sassin and DCA which greatly delayed certifying this aircraft effectively killed off the potential market - only three were ever built (oddly two still survive, though not in the Spraymaster form). The Sundowner never even got off the ground (literally) - DCA wouldn't certify this, the "VH-CXZ" registration is spurious.

I've seen pictures of the Mk 23 before, but it was only after looking at Dave Unwin's spectacular picture of the Bumblemunk, that I began to wonder about C of G issues. The T10 Pilot's Notes specify that solo flight is restricted to the front cockpit. How is the C of G handled in the Mk 23?

Big lumps of lead in the hopper India!

I42:

I was told that one reason that the conversion of the SA29 back to the DHC-1 configuration (the VH-BCA project) was "easy" was because the pilot's seat was in the same position as the rear seat in the Chipmunk (only mounted higher), whereas the Mk.23 seat was located more between the original seat positions meaning that the centre section would have to be re-worked in order to re-converrt.

Re your "solo from the front seat" comment, I'm unsure if there is a balance reason why this should be so. The front seat is located directly on the datum point, meaning that the front seat occupant generates a zero moment arm. Therefore, by my admittedly possibly dodgy logic, the CoG position with two occupants or one only occupant in the rear seat should be the same. And no, I've never tried this out!

This might help explain. Note that the certified CoG range has changed from when this was published.


https://cimg3.ibsrv.net/gimg/pprune....06c7628d4a.png

Mike Sasin the engineer responsible for the SA29 design/modification ended up working for Australian Air Charters at Moorabbin Airport in Melbourne. I was employed by the same company during the mid seventies and knew Mike quite well. He was a nice bloke but terribly bitter about his fight with the 'Department of Changing Names'. (I think it began under DCA). One of the stumbling blocks, if I remember correctly, was the seat belt attachment fittings. Just mentioning it, poor old Mike would go into orbit.

The man must have been a saint George - not only the ongoing squabbles with the "Department of Changing Names", which at one stage involved importing a second fuselage to repeat the conversion to their satisfaction, but when he witnessed the first Spraymaster have an engine failure on take off and crash THE DAY AFTER IT WAS PLACED ON THE REGISTER he helped drag the pilot from the wreckage. Given that the engine stopped due to fuel mismanagement, I've have pushed him back in!

[QUOTE=Dora-9;10674782]I42:

I was told that one reason that the conversion of the SA29 back to the DHC-1 configuration (the VH-BCA project) was "easy" was because the pilot's seat was in the same position as the rear seat in the Chipmunk (only mounted higher), whereas the Mk.23 seat was located more between the original seat positions meaning that the centre section would have to be re-worked in order to re-convert.

Hi Dora, that's very interesting! I'll investigate that but suspect that the rear cockpit is essentially the same. I was flying TF recently and the seat is about abeam the trailing edge, as per the back seat in a T.10 (see pic)
https://cimg2.ibsrv.net/gimg/pprune....d146f007b9.jpg
. Also, simply keeping the rear cockpit would've made the Mk.23 conversion much simpler.

Dave, my engineering knowledge comfortably fits on a pinhead, but that's what the gents at Mareeba (who converted VH-BCA back to the DHC-1 configuration) told me. I too have looked at that Mk.23 photo and pondered...

I'm certainly open to a correction on this.

I do wish the late/great Dick Stratton was still around to answer the queries on Tango Fox, he would have entranced you for hours.

Hi Dave, I have no pics but have fond memories of getting towed behind her on many occasions when gliding with the RAFGSA at Bicester between November 1972 to October 1974. She still had a Gypsy engine then. Great to see her still flying.

Bit more on the Spraymaster conversions on Geoff Goodall's site...

https://cimg7.ibsrv.net/gimg/pprune....d63baa8830.jpg
Thanks Treaders, and here's a fine Keith Wilson photo of Chipmunk Mk.23 'BumbleMunk' flown by me near Saltby Airfield. Can't say too much more, but look in WHS next month....

https://cimg3.ibsrv.net/gimg/pprune....1c409e6aeb.jpg
Another fine Keith Wilson photo of Chipmunk Mk.23 'BumbleMunk' flown by me near Saltby Airfield. Can't say too much more for obvious reasons, but a full report on flying this rare Chipmunk will appear in a popular magazine very soon ...

He would have. TF was converted to a Lycoming while based at Bicester by the RAFGSA for aero-towing and not for agricultural operations. Dick was the instigator of these conversions. While at Bicester, she was painted in a fetching air defence grey - not the best colour scheme for a tug!

https://cimg5.ibsrv.net/gimg/pprune....5f71e3c550.jpg

Hi Dan, according to my research WB563 was bought by Farm Aviation Ltd in 1963, registered G-AOTF and converted to Mk.23 configuration. By 1967 ‘Tango Fox’ had left the agricultural industry and flew as a glider tug with Air Tows at Lasham. It then joined the RAF GSA (again as a tug) and eventually had its original Gypsy engine replaced with a Lycoming O-360. That is a terrible paint scheme for a tug!! BTW I met Dick a couple of times when I was the BMGC Tug Master and he the BGA CTO - very interesting bloke, extremely pragmatic engineer.

You might want to get in touch with some former Clevelands ( RIP ) people when we operated it at Dishforth. .....been dragged into the air many times by her.

Also met Dick Stratton a few times ..had an "interesting " test flight with him out of Bicester once in "CX " also from Dishforth. Brilliant guy and source of information.