The AC-4

A potted review of the AC-4, for those who like lots of pictures visit Jim's AC-4 picture trail. 

The Russian built AC-4 range of gliders (imported a few years ago as the 'ME-7' in the UK) are descendants of one of the 6 gliders that made the prototype stage of the World Class 'competition'. They have a 12.6m, forward swept wing, with significantly higher wing loadings than the PW-5. Performance of the fixed wheel models ('A' and 'B') is similar to the PW-5, and the retractable 'C' model is slightly better at 35:1 best L/D. The question is however, why would anyone buy a glider that not only came second to the PW-5, itself not currently a roaring success, but which costs about one and a half times more than the well proven Libelle or Standard Cirrus?

Why even look at an AC4?

The nicest glider I have ever flown was a Discus. It handled well, has powerful airbrakes, auto connect controls, big cockpit, and very good performance compared to my K6. I felt very confident flying it. Compare that experience with any of the first generation glass gliders; less powerful brakes or a small cockpit or horrible rigging and control connection or balsa wood filler or poor gel coat or twitchy handling or, well you get the picture. But of course a Discus is a LOT more money than a first-gen glider. Now imaging you could get a glider with all the nice points of the Discus, auto control connect and easy rigging, no gel to worry about, powerful airbrakes, confident handling, conventional 'T' tail, for a price that is a lot closer to the first-gen glider than the Discus...interested?

AC-4c on tow, pilot Brad Hill

OK, let's be realistic, 35:1 is less performance than a first-gen glider and a lot less performance than a Discus. I am not going to be able to compete against a Discus one-on-one, but with a handicap? A best L/D of 35:1 and a reasonable high speed polar puts the performance between a K6-E and a Std Cirrus, two well respected gliders. So I have enough performance for say a 500Km in the UK, and a glider that will allow me to compete reasonably in any handicapped or club-class competition. And then you have to question the exact performance you get from a 30 year old glider anyway. So that's the reasoning, I am happy to trade 2-3 points of glide angle for 30 years progress in design and none of those niggling first gen glider problems.

So why an AC4 and not a PW-5 or L33-solo? I did put a bid in for a second hand PW-5 outfit, but the price was more than a new AC4. The L33 is a beautiful glider, and being made of metal should last forever, but that makes it more expensive. Then I discovered that the retractable version of the AC4, the 'C' model was being imported into the UK, and that was the clincher. Nothing against the PW-5 or L33, but the AC4 seems to offer better value than either.

CD1 flying in sink on a rare UK day

What did I get for my money?

My first impression upon seeing my AC4 for real was relief, the quality of the glider is real and not just 'photo' deep. The paint finish is good, the interior is a wonderful 'granite speckle' colour and the cockpit is as large as I had hoped for. I will not pretend that you could not tell the difference between a new AC4 and a new Discus without measuring the wings, the AC4 is a much simpler and lower cost glider, but certainly everyone has seen it has been very pleasantly surprised and I am delighted!

The glider is shipped without instruments, so I have been able to put in a panel of my making, largely designed to keep the cost down. This means you do not have to worry about strange calibration or markings however. Plumbing for T/E and a fin aerial are included which helps. The cockpit ergonomics are pretty good. Plenty of seat and pedal adjustment and plenty of elbow room. I am 6 feet tall and have a few inches of head room left. The airbrake, wheel and trimmer are on the left, handles are smaller than usual but they all work very well. The air vent is a simple pull/push panel, which together with the clear vision panel give plenty of ventilation. The wheel brake lever is stick mounted. There is plenty of room behind the pilot for storage of cross country kit.

The cockpit is big enough for a large bloke who is unlikely to reverse the trend! Small panel, but big enough for a few toys, especially with the radio mounted at the side and cowling mounted compass. Easy to use and effective air-vent at the top (blue), stick mounted wheel brake, adjustable pedals, optional teddy (no he sat beside me for the flight!). All very simple but very effective stuff.

Rigging is wonderfully light. Everything is auto connect and the tailplane and main pins have large, simple to check clips to secure them. You are supposed to be able to rig single handed but frankly I'd rather use two people. The tips are so light that you could use a well trained child. The glider has wing root fairings which are taped on with the usual white glider tape, this is the most time consuming part. From unhitching the trailer to towing out the finished glider takes 15 minutes at the very most.

 

How does she fly?

So far the only flying that has been done was in 20-25 kt winds. Mike Woollard from the BGA, who did the test flight, said on landing "well if you don't want her, I will!". She is clearly a lightweight glider, which means you feel the thermal, but because of the relatively high wing loading, she penetrates very well. I had read this, but until I flew her I was a little skeptical! The handling is something else, with only 12.6 metres of wing she turns really quickly and seems to climb well. Until I get to fly her on a more sensible day, I cannot comment on performance, but the fact she goes into wind so well gives me hope.

Landing was a doddle, airbrakes work well, but again I need to try them out on a nil wind day to really tell. The wheel went down very easily but the wheel brake seemed a little weak? I flew twice, the second time with the root fairings off, and the stall buffet came on a lot sooner and less predictably. For the record Vne is 119 kts, max aerotow is 87kts and max winch is 60kts so you don't need special equipment to fly her! She is cleared for cloud fying and non-inverted aerobatics, but not with me in control!

I can now add some more, having flown her on a 10kt wind, thermic day. Airbrakes are good, I came in way too high and a combination of a wider circuit and brake worked well. The airbrakes match the glider very well. I also found myself low and downwind after following an LS1 to a turnpoint...got back but only just, really glad to scrape in. I can believe in 35:1 as a best L/D. Caught up with some big gliders in thermals, so she climbs well, but I'm not brave enough to corkscrew up the middle!

Conclusions.

So far so good. Very pleased with what I have and glad I made the decision. I am comfortable that 35:1 is a realistic figure for best L/D and that her high speed glide is as good as is claimed.  Enough performance for a 300K easily, proof being that I did mine in CD1.  500K?  Show me the weather!

 

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