Stock Chipmunk vs. modified Chippie vs. Bulldog

[chipmunkbob]

Hi,

I come to you as a sometimes poster and most-time lurker to these boards. I am asking for your opinion on a dilemma that is before me concerning airplanes.

I'll try and keep this as brief as possible. I am currently the "caretaker" of ex-RAF Chipmunk WK639. She was released from AEF service in 1996 so is mostly stock including the Gipsy Major. She is in a high mod state, having been in the RAF so long and converted to fly on the G-reggie before I bought her. I have had her since 1999 and I participate in many airshows (fly-bys and static park) with the EAA Cascade Warbirds group here in Washington State (USA).

My wife and I both love the airplane and revel in the RAF and DH heritage. We have had some problems (mostly mags) and had a top overhaul done on the engine a year or so ago but overall she's behaved herself. Next spring the original fabric will need to be renewed and we are probably looking at a complete Gipsy overhaul in a couple of years. We put about 100 hours on her a year. She is leaking like a sieve though but it is still less than 1 qt/hr loss...

Lately we've been flying some long trips and would like to have a little bit more speed, if a little bit more room (we have a modified baggage area in the Chippie now). I'm also looking at putting rudimentary IFR equipment in the Chippie if only to keep me current and for the occasional need to shoot the ILS at our home field.

The Chippie has always been an airplane that has had many different engine replacements, most of them ugly IMHO. There is one mod however that is very attractive and that is the Walter LOM 337 inline 6 of 210-250hp (depending on version). Couple this with a CS prop (with reverse!!!) and I think you would have a really fun package. The engine and prop weigh about the same as the stock setup so you can still solo from the front. There is a retired airline captain that has done this mod to his Chipmunk but I haven't hooked up with him yet to fly it or get his opinion. I have heard excellent things about the 337, not so good things (but improving) about the engine company.

Now on to the Bulldog. I have been a big fan of the Bulldog/Pup series even before I flew them back in 1996. The sterling handling and the room was impressive. Add a moderate amount of speed and you have a great airplane. But without a tailwheel. In the US the airplanes are experimental - exhibition. My mechanic says that the IO360-A1B6 can be uprated from 200hp to 220hp reliably. A 'dog with increased performance is a good thing and one which gets the thought processes flowing.

So this is my question -
Should I:

a) Keep the Chipmunk stock. Overhaul the Gipsy and find another rare Fairey Reed prop to add to my spares collection. Live with the oil leaks and mag problems. I have so far.

b) Substitute the 337 for the Gipsy. Even airplanes that have more historical significance have been re-engined. At least the 337 keeps the oval Chippie cross section through to the spinner like the original.

c) Sell the Chippie and buy a nice 'dog. Kiss your tailwheel logging days goodbye - but in a faster airplane that holds more in back and has a CS prop, fuel injection in a supported airframe and an in production engine.

So that's it...I look forward to what you all have to say!!

=CB=

[MLS-12D]

Hello Bob,

There is no right or wrong answer; it all depends upon your individual priorities.

If it were my decision, I would choose between (1) and (3). Option (2) may have advantages, but personally I don't like the idea of modifying a semi-rare historic aircraft from its original configuration. Also, as you and your wife are keen participants in the warbird scene, I'm concerned that you may be unhappy with some of the feedback you may receive from people attending the airshows (of course they are mere strangers to whom you owe nothing, but you may get tired of always being asked to explain [justify?] why you modified the airplane).

If the stock Chippie no longer meets your requirements, I would sell it to someone who values its history more than practical considerations, and purchase the Bulldog; or perhaps even an already-modified Chippie (if the 'damage' has been done, you'll have a clear conscience).

Those are my only thoughts; which really aren't worth anything. I suspect that you already know in your heart what is right for you.

[Miserlou]

As stated above, a very personal choice.

I'd go with the stock Chippie but one really must keep an eye on availability of spares.

The LOM engines may be the difference between Gypsy engined aircraft being reduced to static display or staying airworthy. Have a good long chat with the other chap you mention.

Bulldog will be what you end up with when you are fed up of not flying because the maintenance state of the Chippie.

[Lowtimer]

Or
d) Sell the Chippie and get a nice Yak-52 (with / without tailwheel depending on your budget), cruise effortlessly at 150 knots (tailwheel) 130 knots (nosewheel) and climb at 2,000 fpm, cheap spares and far more robust than even the Dog.

I love Chippies and Bulldogs both, but Chipmunks are starting to get very hard to maintain at reasonable cost, as you are finding, and a lot of the ex RAF Bulldogs are VERY tired. A nice one that has lived a quiet life in Sweden or Botswana, though, is a far more tempting aeroplane. Some of them are also fitted with the third seat in the rear. As I was not able to persuade the man who never flies his to sell it to me, I went down the Yak route and I can't say I've regretted it, it's a lovely machine and not as impractical for touring as people will try to tell you (especially with the big tanks).

[waldopepper42]

Slightly off the point, but if you DO decide to keep the stock Chippy, the oil consumption can be much improved by modifying the oil scraper piston rings.

Basicall the originals are swapped for those from a Cummins diesel! We had this mod done to our Chippy by Vintech in the UK and were rewarded with a drastic reduction in oil usage.

If you already knew about this, please accept my apologies - just trying to help!

[chipmunkbob]

Hi Waldo,


Actually this was a mod that was already performed by the RAF (according to the logs) and confirmed at my OH time.

We still lose a little under 1qt/hr. Since acceptable is 2.5qts/hr I guess we're doing OK ;)