Building a Chipmunk from scratch

There is one advertised in loop for £36k, slightly less time, effort and money than building one….

DO IT ! 😀 Fololow your dream and go for it 🙂

Anything is possible 😀

There has been a long and continuous recoird of Chipmunks being modified from their original form. In very few cases has anything untoward happened . Indeed modifications in the U.S has resulted in engines of 295HP and in some cases above being bolted on. It’s an incredibly strong airframe that makes most homebuilds and indeed production machines seem flimsy .
The majority of modifications carried out to the Chipmunk were to extend it’s fatigue life beyond the nominal 10000 fatigue hours . Indeed the steel tie bar mod and Mod .289 to the lower wing spar gave her a life of 30000 fatigue hours . Much of this was drawn from a de Havilland experience with a Dove that came apart in a thunderstorm.

Canadair: Perhaps no-one saw the Harvard break-up coming because no-one has paid for a full-scale fatigue test on it. Perhaps the routine inspections lacked rigour and the early stages of the cracking were not spotted during scheduled maintenannce. At least the Chipmunk and now its civilian owners benefit from the investment put into it by the RAF.

I have no grief with homebuilders doing their own thing in accordance with whatever the airworthiness code is within their country. I just hope they don’t kill innocents while they are at it. I also think it would be best for all concerned if the homebuilders/replica makers gave the Chipmunk a very wide berth!

As far as homebuilts go we have the success stories and we have the cowboys.Do it by the book with proper build techniques,a proven design that has been tested in destructive and non destructive testing.Do it wrong,not deburring holes,use substandard materials,dodgy build techniques with half assed paperwork and your in for a wild ride.Here in Auss a homebuild AFAIK has more freedom than a proven aircraft types restoration or new build.Scarey..

Agcat,
Interesting discussion.
I think the bottom line is we can both support our and refute each others points with statistics, which of course implies statistics will get us nowhere!
You cite the Chipmunk as an example, highly proven, and I would imagine you are correct, no structural failures.
But lets look at an equally successful, if not more so training aircraft, the harvard, T-6, Texan, highly proven, benefiting from operation in dozens of Air Force, yet two years ago it proved to have a major fatigue factor resulting in an inflight failure and loss of life.
Apparently no one saw that coming.
The fact is that if homebuilts were falling from the skies with major components following behind I could endorse your argument, but in reality most homebuilts and for that matter certificated aircraft, tend to hit the earth with all components intact, and more times than not, perfectly flyable.
You see, what neither the PFA, DOT, FAA or any other can effectively regulate is personal ability, or lack thereof, and as long as people are licensed to fly an aircraft, aircraft will crash, unfortunately many times with other people on board.
I agree there must be a check and balance, to a degree, but you cannot control each and every facet. When we choose to fly, we accept an inherent risk, it is our individual choice to minimise that risk to an acceptable level, as we do in most other areas of life.
I have no figures to back it up, but I would imagine on a comparison basis, UK built Homebuilts are no more or less a guarantee of a safe trip than their North American cousins.
I also agree that it is tragic when a passenger is involved, but people enjoy flying, and more times than not will accept the offer of a ride, and the acceptable risk factor is for each to decide, but it probably has a great deal more to do with the specific type and more so even, the person behind the stick.

Canadair – I note your comments and agree that the homebuilt/experimental sector in North America is deregulated, bringing with it certain benefits; but there is a downside. If deregulation meant that only the designer/builder got killed when it all went wrong, then OK. Unfortunately, in the case of the Super Chipmunk a poor innocent passenger was also involved. I wonder how many times the PFA engineers (and perhaps those at the BMAA also, but I have no microlight experience) have prevented someone getting airborne in a home-designed aircraft which had a fundamental design flaw? The US system of total deregulation does not seem to have this long stop to weed out the crass mistakes.

You are right to say that certificated aircraft sometimes suffer structural failures and that maintenance in this sector is not always 100%. I agree. But when did you last hear of a Chipmunk having an airborne structural failure? Touch wood etc etc etc. The Chipmunk – at least the UK-built variant – has undergone a massive programme of structural testing funded by its principal customer, the RAF. The benefits of this testing have crossed over to the civil world and certain structural modifications were developed. Provided that these modifications are embodied at the due time (and provided that owners have properly recorded their fatigue hours!) then structural failure should not be an issue. I am not sure if the Canadian-built variants have the benefit of such testing as in many respects they are quite different aircraft to those buuilt in the UK.

I remain utterly convinced that you mess with proven designs at your peril. If you are going to go the homebuilt route then do it with an organisation like the PFA looking over your shoulder – they might just stop you killing yourself and some poor unsuspecting friend.

Well I have to admit, it now appears I chose a bad example to defend the relative rights of homebuilders!
I was not aware of the follow on history to this Super Chipmunk, very sad to see, the report certainly confirms the errors in construction.
But, Agcat, I think you missed my point.
I was merely pointing out that in the US and Canada, as long as you build and design to “accepted aircraft practice” you are pretty much free to build as you like, no horsepower, wing loading, etc. issues, they are very liberal, and this is of course why we see the vast majority of new designs eminate from these regions.
I was only making an observation that the PFA appears to take a different view, and they require a great deal of analysis, testing, and documentation, ( perhaps this is a funcion of the CAA as Bruce states?) but to me this means that they are then accepting the subsequent blame if the design fails, as they approved it after thorough analysis. Correct?
Thats the point I am trying to make, and why I felt they are potentially liable, where as in the US and Canada the authority has been quite careful to limit it`s liability by leaving the design perameters to the individual builder.
Regardless of these issues, I am and have always been a proponent of “homebuilts” having owned and built a number, ( a few Pitts, a Christen Eagle,) and rebuilt a couple. Every builder has his own definition of “quality”. But believe me poor quality is not solely the domain of homebuilt aircraft, as I have seen appalling examples in the certified world!
I guess the point I am rambling towards 🙂 is that because it is or was “factory Built” is no assurance of quality. Has there never been an example of structural failure of a certified design? of course there has, and it is not limited to design error, there is also many examples of failure due improper construction.
Proven design is a nice statement, and of course it has relevance, but I do not think it automatically is an assurance of quality.
Do not the Russians have a great proverb?
“Best is the enemy of good enough”
That to me sums up a great deal of certified designs, and homebuilts tend to be a labour of love, no commercial pressures. But again as I stated, the level of quality is a variable
To bring this back to historic significance, as this is the historic section, everyone would agree that the new build ME 262`s are vastly superior to the originals, in powerplant and undoubtably in build quality, ( modern materials and practice, not to mention wartime pressures eliminated) but they would never have been built in the UK. So I guess we can say that it is only due to the more liberal attitudes of the regulating authorities in the US and Canada that we now see them flying.

Oh dear. Oh dear. Oh dear. It seems that the silly season has got into full swing!

Canadair: so the PFA stifles innovation and attracts liability to itself? Perhaps, but it or something like it might have saved the life of the owner-pilot and passenger of the ‘Gilles Leger Super Chipmunk’ C-GLSC which crashed on 14th July 2002 at an airport in Quebec. That was a cobbled-up aircraft with a variety of home-made parts. Somehow, the sympathy vote only goes to the family of the poor innocent passenger. Perhaps the reason the website for ‘Super Chipmunk’ is no longer around is because the project bit the dust, so to speak.

If you ever want a lesson in not messing with proven designs, check out this link:

http://www.tsb.gc.ca/en/reports/air/2002/a02q0098/a02q0098.asp

And then people wonder why manufacturers do not release drawings to allow replicas to be built.

WP840 – if you want an iconic Chipmunk that badly why are you prepared to put up with a bodged up homebuilt? Get real, get the real thing!

Nothing to do with PFA – this is a CAA issue, and also an original manufacturer issue. The original manufacturer will not release the drawings for manufacturing purposes. If you want to build a Chippy, and register in the UK, you will need CAA involvement, and they will want to ensure it complies with the published date, which err, isnt available…

Bruce

100,000 pounds + !
5 + years?

It`s already been done!
for lots less money, less time, and it was on the cover of Sport Aviation magazine.

In fact he had a website; www. super-chipmunk.com
but it is now down.
He was even offering kits.
From what I remember he used existing wings, but built the rest, used a continental engine, and a bubble canopy, as per most “super Chipmunks”
However I imagine this type of project was much easier in North America, the fellow was in Quebec.
Once the PFA has to be involved that tends to stifle creativity.

Its a fifty plus year old design with many flying, exactly WHY would they require stress testing, and newly engineered drawings??
To be honest, this attitude of regulating down to the last nut and bolt has always made me wonder, in North America you are pretty much free to build as you like, as the attitude of DOT and the FAA is basic practice applies.
Beyond that, build what you like.
I cannot hep but think the PFA exposes themselves to potential liability by imposing such severe limitations.

And me!

Yes, Mark12 has it about right I reckon. However it depends on how you term ‘from scratch’

Noting your previous posts on the Chippy, I wonder if what you mean is ‘Can I build one from available parts?’

Fact is that most parts for the Chipmunk are still available, and if you go the Lycoming route, you can keep the costs down. You would need a (largely) original fuselage to base the restoration around, and you could happily do the bulk of the work on this before acquiring anything else. That said, good wings are getting scarce now, so it would be worth acquiring a pair and storing them.

There was a good airframe floating around with a knackered Gipsy, airworthy and registered, with the exception of the engine, available for around £10K. Made me think!!

Bruce

A Conservative estimate to build a Chipmunk from scratch would be £100,000

A touch too conservative for me.

Scratch, no donor parts, an awful lot more than that.

Jigs, fixtures, the paperwork and approvals minefield.

Five man years work, at least, plus parts.

Commercial rates, SWAG estimate £.5m.

Mark

Ahhhh the Dhc Chipmunk the first aircraft I ever flew in down at Hurn courtesy of the ATC. (A Canadian aircraft for the person who said it was British! 🙂 )

A 1 to 1 replica of the Chipmunk would be quite a challenge requiring alot of time and money as well as some original components (cockpit glass etc…) and the paperwork would be murder.

A Fibreglass scale replica along the lines of the Isaacs Spitfire could be possible but again the paperwork and cost would be an issue.

If you are keen to go down the Kit root the Popular Flying Association would be a good start they will be able to put you in contact with people who have experiance of the process and pitfalls (as well as the enjoyment) of building your own aircraft:

http://www.pfa.org.uk/

I’m sure if you look at there approved list of kits you will find something that fits in with your tastes.

http://www.pfa.org.uk/engineering_aircraft_index.asp

http://www.pfa.org.uk/pdfs/Hombuilt%20List%20by%20Type.pdf

So you want a new build cheeper to look after airframe and a more modern engine with lower costs than a Gipsy Major, so you dont actualy want a Chipmunk you want a cheep alternative :rolleyes:
No such thing my friend, if you built a Vans RV 8, closest thing to a modern Chipmunk, with a new airframe and a new Lycoming engine on the PFA its still gona cost you £40K plus. Melve is probaly being conservative at £100K, and any way you aint gona get permision from DH Canada to use the drawings, liability you know. 😉

There are a few Chipmunks out there with the lycoming(flat four) engine conversion ,called I believe supermunks; I would have thought that an amount of alteration to the cowlings would be required to fit these engines , but the advantages are that 1, its been done before ,so that design approval is already in place, 2,the engine bearers are welded steel and very simple (on original as well as super) and 3, the engines are available “brand new” or recon, and are much cheaper than gypsy rebuilds. Probably the cheapest way to get a flying A/C, would be to buy a Chippie with either a recently time expired engine, or a major failure ,and throw the engine away ( not actually throw it away you understand!) and replace it with a lycoming.

Building a Chipmunk is easy – start with something larger. A dog and cut away all the bits that don’t look like a chipmunk.

😀

Stuart G, I had seriously considered buying a complete Chipmunk (WP840?) but because of their age thought it would be far cheaper to run a new build airframe.

Err, no, not even close. Not even REMOTELY close

DHfan, I realise it would be quite a substantial undertaking to build a complete aircraft but think, in the long term, it would be very beneficial.

Can’t see that myself. All you would have proved is that you can spend way more than something is worth on something you could have got much more quickly.

QldSpittey, considering the popularity of the Chipmunk would have thought copies of original design plans would have been quite easy to find?

It is not just drawings. You would need to submit endless tons of paper to the CAA. I doubt very much you would get this on the PFA so all work would have to be done by an approved organisation, you would need all the material specs, you would need to design and have approved your engine mounting, you would have to find parts and fittings that were forged or machined in a way that might be cost effective on a production run but very expensive as a one off.

The only thing I still don’t know about building an aircraft is the total cost!

A convervative estimate to build a Chipmunk from scratch would be £100,000

Agcat, I wasn’t planning on using a Gipsy Major engine but choosing a more economical modern engine.

Stuart G, I had seriously considered buying a complete Chipmunk (WP840?) but because of their age thought it would be far cheaper to run a new build airframe.

DHfan, I realise it would be quite a substantial undertaking to build a complete aircraft but think, in the long term, it would be very beneficial.

QldSpittey, considering the popularity of the Chipmunk would have thought copies of original design plans would have been quite easy to find?

The only thing I still don’t know about building an aircraft is the total cost!