Zenith Zenair CH601 HDS – homebuilt with an impeccable pedigree

By: shortfinals

May 08 2011

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Category: aircraft, Aviation, British Isles, England, Great Britain, United States

2 Comments

Aperture:f/7.1
Focal Length:23mm
ISO:200
Shutter:1/200 sec
Camera:NIKON D40

If you wish to build your own aircraft in the U.K., you would be well advised to read widely, talk with other builders, and then join the Light Aircraft Association! Formerly known as the Popular Flying Association (PFA), the LAA provides technical support for the homebuilder; their local branches (known as ‘Struts’) are scattered around the country.

Basically, there are three choices facing someone wishing to build a light aircraft – wood, metal or composite materials. Most aircraft designs will require the ability to work in all three classes of materials, (the W.A.R. Replica kits have a wooden main spar and fuselage framework, but polyurethane foam fuselage sections and fibreglass skinning), but it is wise to match your skills and available working area to the type of aircraft, whether you intend to buy just a ‘bare’ set of plans, some finished components, or a whole kit of parts (minus engine and instruments).

The aircraft shown is a Zenair Zodiac CH601 HDS, built by Terrance Smith of Yeovil, Somerset. This metal monoplane is produced as a set of parts by the Zenith Aircraft Co. of Mexico, Missouri (yes, the town is called Mexico!), who have the exclusive licence to sell the designs of Zenair Ltd., a Canadian-based company, founded in 1973 by the Swiss engineer, Chris Heintz (Zenith is an anagram of Heintz). Chris Heintz has an impeccable aeronautical background – a graduate of the E.T.H. Institute in Switzerland – having worked for Aérospatiale on the design of Concorde, and for De Havilland Canada on the DHC-7, as well as being the former Chief Engineer of Avions Robin in France.

G-CEAT is parked on the grass at Cotswold Airport, Kemble, Gloucestershire; it is powered by a Rotax 912 ULS, a four-cylinder engine putting out 100 hp (maximum) and running on MOGAS. This is capable of giving a cruising speed of 140 mph (at 80% power), whilst consuming only 4 gallons/hr. There is a small problem, in that if you are ‘touring’ away from your home base, you may not, necessarily, find it easy to procure MOGAS on any airfield or strip you use; if AVGAS is used in the Rotax engine either increased wear or damage to certain components may ensue. In any case, when using AVGAS, the oil will need to be changed every 50 hours, and (possibly) the oil tank removed periodocally to remove any lead which has accumulated on the bottom; Rotax service instruction SI 912-016 gives all the necessary data.

The performance of the CH601 HDS has been increased from the previous model by the use of a tapered ‘speed wing’ with near full-span ailerons (there are no flaps, rather like another aircraft Chris Heintz worked on). I am told that it flies ‘something like a Piper Cherokee’; high praise, indeed.

You might have noticed the distinctive Hoerner wing tips, with their characteristic ‘wash-out’. These give the maximum ‘lift area’ for a given wingspan, as they minimise induced drag caused by the formation of wingtip vortices in a ‘conventional’ wing. All things considered, the Zenair Zodiac CH601 HDS is a ‘nifty’ machine, giving excellent performance on modest power. Chris Heintz well deserves the many awards and honours that have been heaped on him by the EAA, LAMA and other organizations.

You may notice that the aircraft bears a name on the starboard side of the engine cowling – ‘Gimlet’. I can only surmise that it is meant to refer to the nickname of a certain fictional Commando officer, Captain Lorrington King, D.S.O., a.k.a. ‘Gimlet’, who appeared in a series of adventure books for boys written by W.E. Johns (much better known for his ‘Biggles’ books) during, and immediately after, WW2. Oh yes, and the other flapless design Chris Heintz worked on? Concorde, of course!

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2 comments on “Zenith Zenair CH601 HDS – homebuilt with an impeccable pedigree”

  1. Hi
    Would love to be present when flying your HDS at 140 mph , i have one made all the modes still not getting close to 120mph !!!

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    • Dear Leon, I was just quoting the book figures. (I don’t own an HDS) Perhaps they confused it with Vmax or Vne – or the reading just before the wings came off in the terminal velocity dive! In any case, the main problem would SEEM to be the one caused by having to avoid lead in the 912, (and the difficulties in easily obtaining MOGAS when touring). Hope that SHS Security is booming…..(used to be in that field myself, once) If I hear of sonic booms being reported over Polokwane, I shall have to put them down to a hard-flown HDS, and not some local flying by a Lightning! Take care……….

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